Appalachia biogeography

Chase D. Brownstein

Article number: 21.1.5A

https://doi.org/10.26879/801

Copyright Society for Vertebrate Paleontology, February 2018

Author biography

Plain-language and multi-lingual abstracts

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Submission: 5 July 2017. Acceptance: 17 January 2018

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ABSTRACT

The Cenomanian to Maastrichtian of the Late Cretaceous saw the flooding of the interior of North America by the Western Interior Seaway, which created the eastern landmass of Appalachia and the western landmass of Laramidia. Though Appalachian dinosaur faunas are poorly known, they are nevertheless important for understanding Cretaceous dinosaur paleobiogeography and ecology. In order to better track the vicariance of eastern and western North American dinosaur faunas over the duration of the Cretaceous, the former were compared with the latter from the Aptian to Maastrichtian Stages of the Late Cretaceous using several similarity indices. The data gathered from biogeographic similarity indices suggest that an almost completely homogenous North American dinosaur fauna found in the Early Cretaceous experienced significant vicariance, splitting into a Laramidian fauna differentiated by the presence of ceratopsids, pachycephalosaurids, saurolophids, lambeosaurines, ankylosaurids, therizinosaurids, and troodontids and an Appalachian fauna characterized by the lack of the aforementioned groups and the presence of non-hadrosaurid hadrosauroids, massive hadrosauroids, basal hadrosaurids, leptoceratopsians, “intermediate”-grade tyrannosauroids, and nodosaurids between the Cenomanian and Campanian, with these two faunas later experiencing limited dispersal after the disappearance of the Western Interior Seaway from the American Interior during the Maastrichtian. Dinosaur provincialism and ecology on Appalachia are also investigated and discussed. Though the fossil record of dinosaurs for parts of the Cretaceous is poor throughout North America and in the eastern portion of the continent especially, the analyses herein nevertheless allow for a greater glimpse at dinosaur biogeography and ecology in Appalachia and in North America generally during the time.

Chase D. Brownstein. Research Associate, Stamford Museum & Nature Center, Stamford, CT. USA.

Keywords: paleobiogeography; paleoecology; Appalachia; Cretaceous; Dinosauria

Final citation: Brownstein, Chase D. 2018. The biogeography and ecology of the Cretaceous non-avian dinosaurs of Appalachia. Palaeontologia Electronica 21.1.5A 1-56. https://doi.org/10.26879/801

palaeo-electronica.org/content/2018/2123-appalachia-biogeography

Copyright: February 2018 Society of Vertebrate Paleontology.

This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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INTRODUCTION

During the Albian to Cenomanian stages of the Late Cretaceous, the interior of North America was flooded by a shallow sea called the Western Interior Seaway (e.g., Russell, 1995; Roberts and Kirschbaum, 1995). The creation of the seaway caused the formation of a long, slender landmass known as Laramidia to the west and the wider, more rectangular Appalachia to the east (e.g., Schwimmer, 2002; Sampson et al., 2010), having appreciable consequences in the evolution of North American dinosaurs. The former of these two landmasses apparently experienced a heightened level of non-avian dinosaur diversification during the Campanian (Sampson et al., 2010; Loewen et al., 2013), when a high level of local dinosaur endemism partnered with regional differences in non-avian dinosaur faunas may have occurred there (Lehman, 1997; Sampson et al., 2010; Loewen et al., 2013). The cause for this rapid diversification of non-avian dinosaurs and other vertebrates on Laramidia has been hypothesized as a consequence of climate variability leading to floral variability, of orogenesis or orogenic activity, and of transgressions and regressions of the Western Interior Seaway (Horner et al., 1992; Lehman, 1997; Sampson et al., 2010; Loewen et al., 2013). There has been some disagreement regarding the existence of faunal provinces on this continent (e.g., Larson and Vavrek, 2010; Lucas et al., 2016).

Unfortunately, the terrestrial fauna of Appalachia is not well-sampled, and only a limited number of dinosaur taxa are known due to lack of Cretaceous-age terrestrial sediments in eastern North America (Baird and Horner, 1977; Baird and Galton, 1981; Baird, 1986; Schwimmer, 1986; King et al., 1988; Gates et al., 2012). Preservation bias thus exists against any articulated specimens of terrestrial animals, including non-avian dinosaurs (e.g., Schwimmer et al., 1993; Schwimmer, 1997). Schwimmer (1997) suggested that, antithetic to the hypotheses of Russell (1995), the known dinosaurs from Appalachia may represent a fair selection of non-avian dinosaur groups endemic to the continent. Schwimmer (2002) also suggested that a lack of theropod diversity or abundance on Appalachia may have also been caused by competition from the massive crocodylian Deinosuchus rugosus, a species abundant in eastern North America with bite marks on both theropod and ornithopod bones attributed to it (Schwimmer, 1997; Gallagher, 1993, 1995; Schwimmer 2002).

The recent discoveries of a leptoceratopsian from the Campanian Tar Heel Formation of North Carolina (Longrich, 2016), the description of the dinosaurs Eotrachodon orientalis from the Santonian-Campanian Mooreville Chalk Formation (Prieto-Marquez et al., 2016a) and Appalachiosaurus montgomeriensis from the Campanian Demopolis Chalk Formation (Carr et al., 2005), and the description of new dinosaur remains from microfossil sites like Ellisdale and Stokes Quarry (e.g., Gallagher, 1993; Denton et al., 2011; Schwimmer, 2015) have largely increased the non-avian dinosaur diversity of Appalachia. The dinosaur fauna of Appalachia itself was apparently dominated by relict forms isolated by the Western Interior Seaway (Schwimmer et al., 1993). However, the development of Appalachian faunas and their eventual mixing with Laramidian ones during the Maastrichtian (Schwimmer et al., 1993; Carr et al., 2005) is poorly understood.

Here, I review and statistically compare faunas known from the Aptian through Maastrichtian of eastern North America with those known from the west to better illustrate the vicariance of Appalachian and Laramidian non-avian dinosaur faunas after the creation of the Western Interior Seaway. This analysis provides a temporal framework for the evolution of non-avian dinosaur faunas on Appalachia. Additionally, non-avian dinosaur provincialism during the Coniacian, Santonian, and Campanian Stages of the Cretaceous was tested using several biogeographic similarity indices and discussed, as were ecological implications regarding competition between predatory dinosaurs and crocodyliforms in Appalachian ecosystems. Because the vast majority of Appalachian dinosaur remains occur in marine deposits and Laramidian dinosaurs are comparatively well-known from terrestrial ones, depositional bias was surely a factor that may have skewed the results of the statistical analyses conducted (e.g., Schwimmer, 1997) and is discussed below. This analysis is important for being the first major one to compare the non-avian dinosaur faunas of Appalachia with Laramidian ones statistically. Specific depositional comparisons between Appalachian and Laramidian faunas analyzed are noted in the results section.

MATERIALS AND METHODS

Permits

No permits were required for the described study, which complied with all relevant regulations. Photographs of specimens from the Arundel Clay referred to herein were supplied by Thomas Jorstad of the National Museum of Natural History. Photographs of the specimens figured herein from the Yale Peabody Museum were provided by Jamie Henderson.

Institutional Abbreviations

The following abbreviations for museum collections are used in the manuscript: USNM V/PAL: United States National Museum (Smithsonian), Washington, DC, USA; UAM(1): University of Arkansas at Fayettville, Fayettville, AK, USA; YPM VPPU: vertebrate paleontology collections, Yale Peabody Museum, New Haven, CT, USA; RMM/MCWSC: McWane Science Center, Birmingham, Alabama, USA; AMNH FARB: American Museum of Natural History (fossil amphibian, bird, and reptile collections), New York, NY, USA; ANSP: Academy of Natural Sciences at Drexel University, Philadelphia, PA, USA; AUMP: Auburn University Museum of Paleontology, Auburn, AL, USA; CCK: Columbus State University (Cretaceous research collections), Columbus, GA, USA; FMNH: Field Museum of Natural History, Chicago, IL, USA; MMNS: Mississippi Museum of Natural Science, Jackson, MS, USA; MOG: Mississippi Office of Geology, Jackson, MS, USA; PPM: Memphis Pink Palace Museum, Memphis, TN, USA; UAM: University of Alabama Museum, Tuscaloosa, AL, USA.

Methods

Faunal lists. Occurrences documenting a total of 54 major clades of non-avian dinosaurs were catalogued from the western and eastern portions of North America. Faunal lists were created for all eastern North American dinosaur-bearing units that corresponded to the Aptian, Albian, Cenomanian, Turonian, Coniacian, Santonian, Campanian, and Maastrichtian stages of the Cretaceous. The biogeographic occurrences that fed the compilation of such faunal lists were taken from an extensive review of previously published works, access to unpublished information, and personal observation, representing to the author’s knowledge the most rigorous review of Appalachian dinosaur faunas to date. Detailed review and references for the faunal lists included in Appendix 1 may be found below. Aptian Appalachian faunas were compared with those of the western North American (pre-Laramidian) Ruby Ranch Member of the Cedar Mountain Formation and units V through VII of the Cloverly Formation, whereas Albian Appalachian faunas were compared with those of the Blackleaf Formation, Wayan Formation, and Willow Tank Formation. Cenomanian Appalachian faunas were compared with the upper Cedar Mountain Formation (Mussentuchit Member), Chandler Formation, and Dunvegan Formation. Turonian Appalachian faunas and the non-avian dinosaur faunas of the Moreno Hill, Frontier, and Matanuska formations were compared. Santonian Appalachian faunas were compared with those of the Milk River Formation. Campanian Appalachian faunas were compared to those of the Wahweap, Kaiparowits, and Kirtland formations representing southern Campanian Laramidian faunas and with the Oldman, Dinosaur Park, and Judith River formations representing northern Campanian Laramidian faunas, whereas the Maastrichtian Appalachian faunas were compared with those of the Javelina, Hell Creek, Lance, and Horseshoe Canyon formations. The Laramidian (western North American) faunas used for comparisons are among the most well known (e.g., Kirkland et al., 1998; Weishampel et al., 2004, Weishampel, 2006; Gates et al., 2010; Zanno and Makovicky, 2013; Sampson et al., 2013; Farke et al., 2014) and represent a sampling of northern, middle, and southern faunas, both factors being considered to minimize statistical bias and error on the part of such faunas. As such, formations like the Foremost Formation, from which only a few taxa and indeterminate elements are known (e.g., Weishampel et al., 2004), were not included.

Statistical comparisons. For comparisons between Appalachian and Laramidian faunas, Simpson’s similarity index, the Jaccard coefficient, and Jaccard distance were employed to quantify the differentiation of the faunas of the aforementioned landmasses over time (Jaccard, 1902; Jaccard, 1912; Simpson, 1943). The former two indices show the statistical similarity of two faunas, with Simpson’s similarity index emphasizing similarity and the Jaccard coefficient emphasizing differences, whereas the Jaccard distance measures the dissimilarity between two faunas and is equal to one minus the Jaccard similarity value (e.g., Jaccard, 1902; Jaccard, 1912; Simpson, 1943). These indices were calculated by comparing dinosaurian faunas at the genus and “family” (= the next highest identifiable clade above genus) levels for the purpose of shedding light on what taxa were differentiating in the context of their parent clades as well as to better factor in the many Appalachian occurrences unable to be identified to the genus or species level. Indeterminate specimens assignable to the “family level”, even those which were the only representation of the presence of a particular clade in a faunas, were only included in “family level” calculations. This protocol was used in order to make the analyses herein more comparable to those of Gates et al. (2010), who coded their datasets at the “family”, genus, and genus-species levels. The latter level was not used in analyses herein, as so few Appalachian dinosaur fossils are identifiable past the genus level (see Appendix 1 and the Review section).

As some Appalachian dinosaur faunas with biogeographically significant records (e.g., the Owl Creek Formation) have yielded less than four distinct species, they were not included in calculations of the Jaccard coefficient, Jaccard distance or of the Simpson similarity index, and instead were compared analytically with western faunas. This group of geological units includes 14 of the Appalachian faunas examined, three of which have yielded the holotype specimens of Appalachian dinosaur taxa. The results of the calculation of these indices can be found in Appendix 1 (the Jaccard distance and Jaccard coefficient are listed in the same tables, with parentheses around values of the former).

Analysis of dinosaur faunal provincialism on Appalachia. Because it has been noted that Laramidia may have had multiple different dinosaur faunal provinces during the Campanian (e.g., Lehman, 1997; Sampson et al., 2010a; Loewen et al., 2013), dinosaur provincialism on Appalachia was also investigated for during the Coniacian, Santonian, and Campanian Stages of the Late Cretaceous. This was done by first rarefying the assemblages, which represent the most well-known (in terms of number of specimens) faunas of units from the aforementioned Stages of the Late Cretaceous and then by employing the Simpson similarity index and Jaccard coefficient to compare faunal similarities at the genus and family levels for each. Rarefaction, which calculates the expected number of taxa in a given sample A if that sample were reduced to the size of a smaller sample B (e.g., Sanders, 1968), was used to examine sampling differences between Appalachian dinosaur-bearing strata and assess for sampling bias between the corresponding faunas. The relative ages of each of the stratigraphic units was also taken into account during this process, and the ages of the formations included in this analysis of provincialism are given in the results section. The fauna of the coeval Campanian Mooreville Chalk, Blufftown, and Coffee Sand formations and an unnamed clay from Missouri were also rarefied for comparison with the Coniacian/Santonian Eutaw Formation in order to track the development of dinosaur faunas in the southeastern United States during Late Cretaceous. In comparing faunas, the presence of larger phylogenetic groups was considered. In the case of Aptian, Cenomanian, and Maastrichtian Appalachian faunas, the existence of only one comparatively well-sampled fauna in each case did not allow for considerations of provincialism. The Albian Appalachian Formations were also too poorly sampled to allow for rarefaction.

Biases. As previous studies have noted, biases in the collection of fossils, use of previously published literature, taphonomic biases among and within sedimentary units, and temporal differences among sedimentary units studied and within their faunas all play a role in skewing paleobiogeographic analyses (e.g., Nicholls and Russell, 1990; Lehman, 1997; Gates et al., 2010). Because of these factors, the specific paleoenvironments, taphonomy, and age of sediments compared herein were extensively reviewed and compared in the Results section.

Biases in the collection of fossils have been noted as an appreciable hindrance to paleobiological analyses previously (e.g., Alroy et al., 2001; Smith, 2001, 2007; Lloyd et al., 2011). Indeed, such biases among the Campanian Kaiparowits, Judith River, Dinosaur Park, and Kirtland formations were reviewed by Gates et al. (2010), who noted that significant biases exist even between these and the other Campanian faunas they compared. However, because few extensive dinosaur faunas are known from the Aptian to Santonian of North America (e.g., Carpenter et al., 1995; Kirkland et al., 1998; Main, 2013), the ability to perform statistical analysis on known faunas would be severely limited if an attempt was made to rule out certain collection biases for such comparisons. Regarding to the analysis of Appalachian dinosaur provincialism during the Campanian, collection biases are easier to take into account and are discussed below.

As noted, biases in this study reflecting taxonomically or occurrence-wise inaccurate faunal lists relied on herein may also be present (e.g., Lehman, 1997; Lloyd et al., 2011). However, given the extensive literature review undertaken for the review of Appalachian faunas and for their comparison with Laramidian faunas and the large amount of data compiled, any such discrepancies seem not to be a large bias in the analyses undertaken.

REVIEW

Aptian

Arundel Clay. The most well-represented dinosaur fauna from the Early Cretaceous of eastern North America comes from the Arundel Clay of Maryland. The classification of these elongate, discontinuing clays as a formation has been debated, and the deposits have been interpreted by at least one author as those of oxbow swamps (Kranz, 1998). Further support against the existence of the Arundel as a formation comes from the fact that the palynomorphs of the Patuxent and Arundel sediments cannot be distinguished (Brenner, 1963; Doyle and Hickey, 1973; Doyle and Robbins, 1977; Robbins, 1991; Kranz, 1998). Lipka et al. (2006) considered the Arundel Clay to be a facies contained within the Potomac Formation of late-early Aptian age. The Arundel is made up of black lignite and massive dark-grey mudstones containing limonite and siderite and is the second oldest and most fossiliferous of the three Potomac facies (Lipka et al., 2006). Here, the classification of the Arundel Clay by Lipka et al. (2006) is followed.

The non-avian dinosaur fauna present within the Arundel Clay facies consists of a variety of theropods, at least one species of sauropod, and specimens representing at least three ornithischian clades. The theropods of this unit include the dubious “Allosaurus” medius described on the basis of a single tooth (Figure 1.1) (Marsh, 1888) and other elements that were later assigned to “Dryosaurus” grandis (Lull, 1911), Coelurus gracilis described on the basis of a pedal claw (Figure 2.5) (Marsh, 1888; Lipka, 1998), and Creosaurus potens based on a caudal vertebra (Lull, 1911). “Allosaurus” medius was regarded by Lipka (1998) as a carnosaur and Coelurus gracilis a coelurosaur. Lipka (1998) noted that Ostrom (1970) had considered the holotype pedal ungual of the latter as similar to Deinonychus and suggested a possible relation. Holtz et al. (2004) listed all three of these theropods as indeterminate.

Several large teeth (Figure 1.2-4) described by Lipka (1998) and reviewed and figured in Weishampel (2006) have been assigned to a large allosauroid similar to or synonymous with Acrocanthosaurus. Lipka (1998) was able to assign these large, serrated teeth to Acrocanthosaurus based on several features diagnostic to that taxon found on its teeth, discussing the controversy over assigning teeth to a specific taxon of dinosaur. This carcharodontosaur has been regarded as the apex predator of the Arundel ecosystem (Weishampel, 2006). Importantly, two distinct possibilities regarding the presence of two carnosaurs in the Arundel facies have been stated (Lipka, 1998). The first, regarding the Arundel “Creosaurus” potens and Acrocanthosaurus material, suggested they represented distinct taxa, whereas the second held that the “C.” potens material belonged to the taxon Acrocanthosaurus (Lipka, 1998). This latter hypothesis is more congruent with data on carcharodontosaur ecology from geologically younger Appalachian sites and from other Early Cretaceous localities (e.g., Weishampel et al., 2004; Appendix 1). Though the fairly diverse ornithischian and small theropod fauna and the presence of at least one species of sauropod in the Arundel may have allowed for the coexistence of two large carnosaur species, more complete carcharodontosaurid specimens must be recovered to accurately test this hypothesis (Lipka, 1998). In addition to the teeth, a massive manual ungual from the Arundel (Figure 1.5) may also be assignable to Acrocanthosaurus.

Another clade of carnivorous theropod dinosaurs represented in the Arundel are the dromaeosaurids. Lipka (1998) assigned strongly recurved, laterally compressed teeth retrieved from the Arundel facies to Deinonychus, and several are figured herein (Figure 2.1-4). Lipka (1998) noted that these teeth and those of Acrocanthosaurus from the Arundel extended the range of both taxa during the Aptian across North America.

One of the better records of theropod dinosaurs from the Arundel is of at least two indeterminate taxa of ornithomimosaurs. The bones originally described as “Dryosaurus” grandis by Lull (1911) and later as a species of Ornithomimus (O. affinis) (Gilmore, 1920) are currently in the collections of the USNM (Figure 3.1-6). More recently, the specimens were assigned to Archaeornithomimus (Russell, 1972), to indeterminate theropods (Smith and Galton, 1990), and to Ornithomimosauria indet. (Makovicky et al., 2004; Weishampel, 2006; Brownstein, 2017a). All but one of the original specimens of Arundel ornithomimosaurs were found at the same site near Muirkirk, Maryland (Gilmore, 1920). These original specimens include a dorsal vertebral centrum, two elongated caudal vertebrae, the distal ends of metatarsals II and III, two phalanx II-1s, a partial astragalus from the left hindlimb, a pedal phalanx III-2, a partial phalanx identified as from pedal digit IV, and a single pedal ungual (Figure 3.1-6). Additionally, a partial anteroposteriorly short pedal phalanx IV-? was assigned to “Ornithomimus affinis” (Gilmore, 1920). Gilmore (1920) noted that more material from Arundel ornithomimosaurs, including a partial tibia, phalanx and pedal ungual (USNM PAL 466054) had been recovered (Figure 3.1) (Weishampel and Young, 1996), and there are also many other specimens which have not yet been described formally in the literature (pers. obs.). The original fossils found nearby Muirkirk likely come from the Dinosaur Park site, which has yielded the tibia and other pedal elements as well as a variety of other elements including many pedal unguals (Brownstein, 2017a). Notably, two morphotypes of ornithomimosaur pedal unguals (diagnosed as such based on a single flexor fossa on the ventral surfaces of the elements) are found at this site: the shorter and smaller recurved unguals like that described by Gilmore (1920), and elongated, larger unguals with more flattened ventral surfaces in lateral view and less expansive dorsal and ventral faces over their proximal articular facets (Brownstein, 2017a). This latter morphology is more akin to the pedal unguals of more derived ornithomimosaurs, suggesting the possibility of two distinct ornithomimosaurs coexisting within the Arundel facies. Two ornithomimosaur taxa are known from the Yixian Formation of China, which is of similar age to the Arundel.

The sauropod material from the Arundel facies has been the subject of some taxonomic confusion (Figure 4.1-4). A sauropod tooth was named Astrodon johnstoni (Leidy, 1865). Marsh (1888) named two species of his new genus Pleurocoelus from sauropod bones discovered near Muirkirk, Maryland. Pleurocoelus nanus was named from cranial elements and multitude of other fragmentary and isolated remains of several individuals, whereas P. altus was named on the basis of a partial hindlimb (Weishampel, 2006). Later studies have synonymized the three taxa (Hatcher, 1903; Gilmore, 1921; Carpenter and Tidwell, 2005), though some have doubted this taxonomic classification and instead regard all three Arundel sauropod species as dubious (Rose, 2007; D’Emic, 2013). If the Arundel material does indeed belong to one valid species, the correct name would be Astrodon johnstoni, which Carpenter and Tidwell (2005) classified as a basal titanosauriform. This placement is consistent with the data on sauropod clades in North America during the Early Cretaceous (e.g., Weishampel et al., 2004; Appendix 1). Carpenter and Tidwell (2005) and Weishampel (2006) suggested that the three Arundel sauropod taxa represented different growth stages of the same taxon; Weishampel (2006) estimated juveniles at 5 m and 500 kg in size with adults approaching 20 m and 18000 kg. Juveniles of the Arundel titanosauriform may have been prey items of the carcharodontosaurids, which were present in the region.

A single tooth was referred to the medium-sized ornithopod dinosaur Tenontosaurus sp. by Galton and Jenson (1979). This assignment was followed by Weishampel and Young (1996). Norman (2004) later assigned this specimen to Iguanodontia indet. Nevertheless, the tooth provides evidence for a large iguanodont in the Arundel ecosystem, adding to the similarities between the eastern Arundel fauna and the Aptian faunas of western North America (e.g., Ostrom, 1970; Forster, 1984; Forster, 1990; Winkler et al., 1997; Weishampel et al., 2004).

Armored dinosaurs left one of the better records of Early Cretaceous eastern North American ornithischians, and are represented by the genus Priconodon crassus in the Arundel Clay (Figure 5.1-5). This animal was first described on the basis of a single tooth (e.g., Carpenter and Kirkland, 1998), and additional teeth, an osteoderm (Weishampel, 2006), and a tibia (Carpenter, 2001; Vickaryous et al., 2004) have since been recovered. A multitude of teeth and the tibia referred to this taxon are in the collections of the United States National Museum. These teeth are all similar in being triangular, short, and having large denticles, and are assigned to nodosaurs based on the presence of a cingulum on the tooth between the base and the entirety of the crown and their narrow morphology (Weishampel, 2006). Notably, Priconodon crassus has been regarded as an unusually large nodosaurid based on the huge size of the teeth assigned to it (Carpenter, 2001). Though some have regarded this fragmentary taxon dubious (Vickaryous et al., 2004), the validity of this species has been supported by multiple studies comparing the morphology of the teeth of Priconodon with other nodosaurids (Carpenter, 2001; West and Tibert, 2004).

Lastly, the Arundel has surprisingly yielded teeth (Figure 5.6-7) described in detail and found to be most similar to those of neoceratopsians by Chinnery et al. (1998). The Arundel neoceratopsian teeth are especially important as they predate the age of the holotype skeleton of Aquilops americanus, which was discovered in Albian deposits (Farke et al., 2014), teeth from the Cenomanian Mussentuchit Member of the Cedar Mountain Formation (Chinnery et al., 1998), and possible ceratopsian remains from the late Albian of Idaho (Weishampel et al., 2002). This makes the Arundel teeth the oldest occurrence of neoceratopsians in North America, suggesting that the clade arrived in the continent during the middle Early Cretaceous and thus supporting the hypothesis that neoceratopsians had dispersed into North America during the Aptian (Farke et al., 2014). Farke et al. (2014) suggested that at least three interchanges of neoceratopsians, the first being of Aquilops-like taxa, occurred between North America and Asia. Therefore, the Aptian age of the Arundel teeth suggests that the Arundel neoceratopsian may have been part of this dispersal and therefore would have been similar to the small Aquilops in form.

The Arundel Clay dinosaur fauna therefore consists of Acrocanthosaurus sp. and perhaps another large carnosaur, indeterminate coelurosaurs, the dromaeosaurid Deinonychus (including “Coelurus” gracilis), two unnamed possible species of ornithomimosaurs, the titanosauriform sauropod Astrodon johnstoni, iguanodontian dinosaurs similar to or possibly synonymous with Tenontosaurus, the large nodosaurid dinosaur Priconodon crassus, and a neoceratopsian.

Patuxent facies. Another one of the facies assigned to the Aptian by Lipka et al. (2006) is the Patuxent, the oldest unit exposed in the coastal plain of Maryland and Virginia (Stanford et al., 2004). This facies consists of sandstones mixed with light grey mudstones (Lipka et al., 2006). Though this formation has not preserved an extensive faunal list like the western Cloverly or Cedar Mountain Formations (Weems and Bachman, 1997), a somewhat extensive ichnological record of dinosaurs has been preserved in Patuxent facies. These include the tracks of theropods (Megalosauropus sp.), euornithopods (Amblydactylus sp.), and an ichnotaxon based on the tracks of a small ornithopod with possible affinities to the western form Zephyrosaurus (Hypsiloichnus marylandicus) (Weems and Bachman, 1997; Stanford, 1998; Stanford and Stanford, 1998; Stanford et al., 2004; Weishampel et al., 2004). One study (Lockley and Stanford, 2004) reported from the siliciclastic Patuxent facies the tracks of 14 different morphotypes of ornithopod, theropod, sauropod, and ankylosaur tracks. Lockley and Stanford (2004) also reported the presence of small tracks interpreted as those of hatchling dinosaurs alongside those of juveniles and adults, which they regarded as indicating the presence of nests nearby. Weems and Bachman (2015) reviewed and added to the known dinosaur ichnotaxa from the Patuxent facies, which they found to include the theropod ichnotaxon Megalosauropus sp., the ornithomimosaur ichnotaxon Ornithomimipus angustus, the sauropod ichnotaxon Brontopodus birdi (suggested to be the track of a titanosauriform), the ichnontaxon Tetrapodosaurus borealis (interpreted as a nodosaurid and compared with Propanoplosaurus), the small ornithopod taxon Hypsiloichnus marylandicus (suggested to be tracks of a dinosaur of similar grade to Zephyrosaurus schaffi), and the medium-sized to large euornithopod tracks Caririchnium leonardii (suggested to be tracks of Tenontosaurus), Gypsichnites pacensis (suggested to be tracks of an iguanodontid of similar size to Hippodraco scutodens), and Amblydactylus gethingi (suggested to be the tracks of a hadrosauroid similar to Eolambia) (Weems and Bachman, 2015).

The nodosaur genus Propanoplosaurus marylandicus (Figure 5.8) is known from a specimen constituting of both molds and casts of the skeleton of a neonate individual which was recovered alongside the ichnofossils of dinosaurs (Stanford et al., 2011). The specimen included the posterior cranium, the ribcage vertebrae, the right femur and portions of the pes, and the partial right forelimb. The holotype of Propanoplosaurus is important for being the first nodosaur skeleton from the eastern seaboard (Stanford et al., 2011) and along with Priconodon is the only valid nodosaur taxon named from the Aptian of the east coast of North America.

Arkansas Trinity Group. The Trinity Group in Arkansas consists of varying layers of fine quartz sand, clay, barite, celestite, gravel, and fossiliferous gypsum and limestone (Dane, 1929; Hunt-Foster, 2003). These sediments, which are deposited in an unconformity with eroded Paleozoic rock, originated in the Ouachita Mountains (Hunt-Foster, 2003). The record of dinosaurs from the Aptian of Arkansas is limited. However, the partial right pes of an ornithomimosaurian dinosaur (Quinn, 1973; Hunt-Foster and Kirkland, 2017) was collected from what is now termed the “Friday Site”. This specimen, UAM(1) 74, consists of metatarsals II, III, and IV and four phalanges and portions of the pedal unguals from pedal digits II, III, and IV reported from what is now termed the “Friday site” (due to it being on the property of Joe B. Friday, discoverer of the specimen) in Lockesburg Arkansas (Quinn, 1973; Hunt-Foster, 2003). Both the holotype and casts of the specimens are in the collections of the University of Arkansas.

Albian

Dakota Formation. The Albian Dakota Formation of Kansas and Nebraska has yielded the remains of a variety of dinosaurs whose relatives are also observed from the facies of the Potomac Formation. This formation consists of coastal and marine fluvial deposits in Kansas (e.g., Liggett, 2005) and as fluvial to estuarine deposits characterized by major facies changes and having common hydromorphic paleosols and disticontinous, long lignites and carbonaceous mudstones in Nebraska (e.g., Brenner et al., 2000; Joeckal et al., 2004). The most complete dinosaur skeleton ever found on the eastern margin of the Dakota Formation is the Kanas taxon Silvisaurus condrayi. The holotype specimen of this dinosaur was retrieved from a site pertaining to the Terra Cotta Clay member of the Dakota Formation in Ottawa County, Kansas, a hard, limonite-containing sandstone that was cross-bedded (Eaton, 1960). The environment in which Silvisaurus condrayi would have lived is regarded as a warm-temperate forest based on fossil leaves found nearby the Silvisaurus site (Eaton, 1960). In addition to a partial skeleton including cervical and dorsal vertebra, a sacrum, and armor including a spike possibly from the shoulder, the holotype of Silvisaurus condrayi also includes a skull and a left mandible, all of it corresponding to an individual approximately 3 m long (Eaton, 1960). During the Skull Creek highstand, the site where Silvisaurus condrayi was found would have been on the coast of the newly-formed continent of Appalachia (e.g., Eaton, 1960). The natural mold of the possible sacrum of another Silvisaurus has been retrieved from Russell County Dakota Formation exposures (Liggett, 2005).

In addition to Silvisaurus, the Dakota Formation of Kansas has yielded the tracks of ornithomimosaurs (Magnoavipes sp.), of possible ankylosaurids, and of indeterminate dinosaurs (Liggett, 2005). The probable sacrum of an ankylosaur has also been found in Cloud County, Kansas (Liggett, 2005). In Nebraska, both ornithopod footprints and the proximal end of an ornithopod femur have been recovered from Dakota Formation sediments (Joeckel et al., 2004).

Paw Paw Formation. The Paw Paw Formation of Texas is middle Albian in age and has produced the remains of two to three species of nodosaurid dinosaurs along with indeterminate nodosaur remains (e.g., Coombs, 1995; Lee, 1996; Weishampel et al., 2004). The formation is made up of ferruginous clay and sand (Hill, 1894) and was deposited in a nearshore marine setting (Scott et al., 1978). Nodosaurid dinosaurs have left a number of specimens in this formation, including a juvenile nodosaur (Jacobs et al., 1994) and two named taxa.

Pawpawsaurus campbelli is known from a complete skull lacking mandibles from Tarrant County, Texas that is morphologically similar in some ways to Silvisaurus condrayi (Lee, 1996 Paulina-Carabajal et al., 2016). Texasetes pleurohalio is known from a partial skeleton including a skull fragment, a tooth, elements from the limbs, portions of the pelvis and scapulocoracoid, and vertebrae (Coombs, 1995) and may be a synonym of Pawpawsaurus (Lee, 1996). However, in the phylogenetic analysis of Ankylosauria, the two Paw Paw nodosaur taxa and the Paw Paw nodosaur juvenile were found to be in notably different phylogenetic positions, with Pawpawsaurus the sister taxon to Europelta, Texasetes a sister taxon to Edmontonia, Denversaurus, and an unnamed nodosaur from Argentina, and the Paw Paw juvenile a sister taxon to Niobrarasaurus (Arbour et al., 2016).

Paluxy Formation. The Paluxy Formation of Texas, which is also middle Albian in age (e.g., Jacobs and Winkler, 1998; Weishampel et al., 2004; D’Emic, 2013), is a thin unit composed of shale and sandstone (Caughey, 1977). This unit has preserved arguably the most diverse of dinosaur faunas corresponding to Appalachia during the Albian. In addition to the remains of indeterminate theropods, the fossils of indeterminate dromaeosaurids have been recovered (e.g., Langston, 1974; Weishampel et al., 2004). Importantly, remains assigned to Ornithomimus sp. have also been recovered from the formation (e.g., Langston, 1974; Weishampel et al., 2004). As noted, both ornithomimosaurs and dromaeosaurs are known from Aptian to Albian deposits in the American west (Ostrom, 1969; Ostrom, 1970; Ostrom 1976; Cifelli, 1997; Cifelli and Gardner, 1997, Weishampel et al., 2004; Signac and Mackovicky, 2010; Oreska and Carrano, 2013; Brownstein, 2017a). Notably, “Laelaps” (= Dryptosaurus sp.) has also been reported from the Paluxy Formation (Langston, 1974), but these remains are likely those of indeterminate coelurosaurs or simply indeterminate theropods. Remains assigned to titanosauriforms (=“Pleurocoelus”) have also been reported from the formation (Langston, 1974; Weishampel et al., 2004). These specimens have more recently been assigned to the taxa Astrophocaudia and Cedarosaurus by D’Emic (2013). Indeterminate sauropod fossils have also been reported from the Cloverly Formation (e.g., Ostrom, 1970; Oreska and Carrano, 2013), while in Texas the ichnotaxon Brontopodus birdi has been reported from multiple localities (e.g., Langston, 1974; Pittman, 1989). Additionally, specimens assigned to nodosaurids and Tenontosaurus have been reported from the Paluxy Formation (Langston, 1974; Weishampel et al., 2004).

Glen Rose Formation. The Glen Rose Formation, which consists of alternating hard limestone and marl or marly limestone (Sellards et al., 1932), has preserved both dinosaur body specimens and ichnofossils. Trackways include the ichnotaxon Eubrontes glenrosensis (=?Acrocanthosaurus), which is found alongside the tracks of sauropods (Brontopodus) in the Paluxy River Valley (Farlow et al., 2010). There are also additional sites within this valley which have produced tridactyl tracks (Farlow et al., 2010). The Glen Rose has produced the trackways of both theropods and ornithopods (e.g., Wrather, 1922; Gould, 1929; Houston, 1933; Bird, 1939; Bird, 1944; Langston, 1974; Kuban, 1986; Pittman, 1989; Hawthorne and Bonem, 2002; Vance, 2002; Rogers, 2003). The ornithopod Tenontosaurus has also been reported from the formation (Weishampel et al., 2013). A partial juvenile titanosauriform skeleton is known from the Glen Rose as well (e.g., Langston, 1974; D’Emic, 2013), though it is not diagnostic to the genus level. In its entirety, the documented Glen Rose fauna consists of large theropods represented by tracks, sauropods, and ornithopods. This fauna is also somewhat similar to the theropod and ornithopod fauna of a track locality from the Chuta Formation of Mexico (Ferrusquía-Villafranca and Applegate, 1978).

Cenomanian

Woodbine Formation. The Woodbine Formation of Texas has preserved the singularly most complete dinosaur fauna of eastern North America during the early Late Cretaceous, representing fluvial, shelf, and deltaic deposits (Oliver, 1971; Trudel, 1994; Main, 2005; Main, 2013), and consisting primarily of sandstones and shales (Johnson, 1974).

The most diverse non-avian theropod dinosaur assemblage from the Woodbine Formation comes from a locality known as the Arlington Archosaur Site, which would have been on the Rudradia Peninsula of Appalachia during the Cenomanian (Main, 2013). This locality has produced the teeth of both dromaeosaurids and adult and juvenile allosauroids as well as the remains of other coelurosaurs (Main, 2013). The proximal portion of a large manual ungual was also recovered and may belong to an animal similar to Allosaurus, Acrocanthosaurus, or Suchomimus (Main, 2013). The latter possibility is unlikely, as no spinosaurid remains have currently been reported from North America. Main (2013) also discussed the possibility that some of the material recovered at the site could belong to tyrannosauroids. Additionally, teeth assigned to the taxon Richardoestesia have also been retrieved from the Arlington Archosaur Site (Main, 2013). Additions to the theropod fauna known from the Woodbine Formation include cf. Richardoestesia teeth and the tracks of theropods, including ornithomimosaurs (Magnoavipes) (Lee, 1997a, 1997b; Lockley et al., 2001; Lockley et al., 2011). The Arlington Archosaur Site also has preserved the remains of the hadrosauroid dinosaur Protohadros byrdi and P. sp. (Main, 2013). This genus of hadrosauroid dinosaur was originally named on the basis of a partial skull and fragmentary skeleton retrieved from Flower Mound in Denton County, Texas, and has been estimated at 7 to 8 m in length (Head, 1996; Head, 1998). This species possessed a robust set of ventrally oriented mandibles suggested as an adaptation for the consumption of low-lying plant matter (Head, 1996; Head, 1998). A set of ornithopod tracks from the Woodbine Formation have been assigned the name Caririchnium protohadrosaurichnos based on the hypothesis that they may represent the tracks of this taxon (Lee, 1997b).

Ornithischian remains assigned to indeterminate hadrosaurs and a basal nodosaurid have reported from the Woodbine Formation (Lee, 1997a). The Woodbine nodosaur, which is known from teeth, limb elements, and an osteoderm, may be a distinct species (Lee, 1997a).

Raritan Facies. The Cenomanian Raritan facies of the upper Potomac Formation (e.g., Dalton et al., 1999; Miller et al., 2004; Lipka et al., 2006) preserves a scant but biogeographically significant non-avian dinosaur fossil record. This unit is made up of alternating clay and sand beds (Kimyai, 1966; Dalton et al., 1999; Miller et al., 2004; Lipka et al., 2006) and has produced both the only record of dinosaur tracks from the Cretaceous east of the Mississippi river and several other specimens, including an isolated distal metatarsal II of a tyrannosaur (YPM VPPU 016760) most similar to Appalachiosaurus montgomeriensis (Figure 6.1-6) (Baird, 1988, 1989; Gallagher, 1997; pers. obs.).

The trackway described in detail by Baird (1989) consists of the pes prints of a large theropod dinosaur. These tracks have been regarded to have affinities with those of a “megalosaurian type” (Baird, 1989). More recent studies have cast doubt on assigning any Cretaceous tracks to megalosaurs (Lockley et al., 1998). All of these tracks are now lost except for one track on display at the Rutgers University Geology Museum (Baird, 1989; Gallagher, 1997). A trace of the track at Rutgers was figured in Baird (1989) and is nearly identical in form to the Saurexallopus tracks from western North America figured by Gierlinski and Lockley (2013) in the slenderness and lengths of digits II through IV, the morphology for the impression of digit I, the relative size and shape of the digits to each other, and the presence of a noticeable hallux track alongside a somewhat centrally located noticeable metatarsophalangeal pad suggesting the presence of an arctometatarsus in the track maker. The swelled pad behind pedal digit III and the reversed hallux were noted by Gierlinski and Lockley (2013) to be features of avian pedal morphology. Additional tracks figured in Baird (1989) in photographs taken before the tracks were lost are identical to some western Saurexallopus tracks listed in Gierlinski and Lockley (2013) (Gierlinski and Lockley, 2013, figures 23.1A, C, 23.3B) and also seem to show the presence of a clearly centralized triangular metatarsophalangeal pad extremely indicative of an arctometatarsalian condition and a hallux toe indicative of an avian pes as noted by Gierlinski and Lockley (2013). Gierlinski and Lockley (2013) suggested that the trackmakers of western Saurexallopus were oviraptorosaurians, especially noting Hagryphus and Chirostenotes as plausible candidates based on the presence of a well-developed hallux toe among members of the Oviraptorosauria. This feature is shared by the larger Woodbridge tracks. Thus, it may be that the Woodbridge tracks represent some large oviraptorosaur. However, here the relationships of the tracks are regarded as equivocal among Theropoda.

In addition to theropod material, euornithopod tracks have also been recovered from the Raritan facies of the Potomac Formation (e.g., Weishampel et al., 2004). These represent an important occurrence as they evince the presence of herbivorous dinosaur taxa in the upper Potomac fauna. The possibility also remains that these tracks belong to hadrosauroids, though any assignment beyond Euornithopoda would be tentative.

The Potomac Formation clearly represents an enticing look into the non-avian dinosaur fauna of the Cenomanian of northern Appalachia. Currently, the sparse record of non-avian dinosaurs has produced at least three different types of dinosaur. Importantly, the Raritan Facies of the Potomac Formation is a terrestrial deposit, suggesting a likelihood that future dinosaur specimens may be discovered from the formation (e.g., Gallagher, 1997).

Coniacian and Santonian

Niobrara Formation (Smoky Hill Chalk). The Niobrara Formation non-avian dinosaur fauna is important for being the only known non-avian dinosaur fauna from the Coniacian of Appalachia as well as for being one of the only records of Coniacian North American dinosaurs. The two most completely known taxa from this formation are the nodosaurid Niobrarasaurus coleii and the derived non-hadrosaurid hadrosauroid Claosaurus agilis, both from Coniacian-Santonian sediments (Carpenter et al., 1995; Weishampel et al., 2004; Prieto-Márquez​ et al., 2016b). Additionally, the nodosaurid Heirosaurus sternbergi is known from more fragmentary remains (Carpenter et al., 1995), though it may be a synonym of Niobrarasaurus (Carpenter et al., 1995; Everhart, 2005).

Indeterminate nodosaurid and hadrosauroid specimens have also been recovered (Carpenter et al., 1995; Everhart, 2005; Everhart and Hamm, 2005; Everhart and Ewell, 2006; Everhart, 2014). One set of hadrosaurid caudal vertebrae from an animal somewhat larger than the holotype of Claosaurus agilis has been recovered with evidence of consumption by a large shark (Everhart and Ewell, 2006). The preservation of partial specimens in the marine Smoky Hill Chalk is typical of the bloat-and-float model of preservation, which often characterizes Appalachian dinosaur specimens (Schwimmer, 1997). The author follows Carpenter et al. (1995) and Prieto-Márquez​ et al. (2016b) in considering this fauna to be Appalachian, a hypothesis which is supported by the close position of Claosaurus to Lophorhothon as a non-hadrosaurid hadrosauroid and of Niobrarasaurus as outside the group containing the derived western nodosaurids of the Late Cretaceous (e.g., Arbour et al., 2016; Prieto-Márquez​ et al., 2016b), being congruent with the current understanding of Appalachian as a refugium (e.g., Schwimmer, 1997). Further discussion on the assignment of the Niobrara fauna to an Appalachian origin may be found in the discussion section.

Claosaurus agilis was a small hadrosauroid and is only known presently from a fragmentary specimen that has been described in detail (Carpenter et al., 1995) and compared with other Appalachian hadrosauroids (Prieto-Márquez​ et al., 2016b). Claosaurus has most recently been resolved as a derived hadrosauroid just outside to Hadrosauridae (Prieto-Márquez​ et al., 2016a).

Niobrarasaurus coleii is the most completely known of the three ornithischians from the Smoky Hill Chalk, and the holotype of that taxon consists of a partial specimen including portions of the skull, vertebrae, partial limbs, and a variety of osteoderms (Carpenter et al., 1995) originally described as a species of Hierosaurus (Mehl, 1936). Hierosaurus sternbergi, the original “Niobrara nodosaur”, is based on a multitude of osteoderms first described in 1905 by George Wieland (Wieland, 1905). More recently, Heirosaurus has been regarded as a nomen dubium (e.g., Carpenter et al., 1995).

McShan Formation. The McShan Formation of the southeastern United States also provides an important glimpse into Coniacian Appalachian faunas, arguably making the Appalachian dinosaur record from the Coniacian more complete than that from Laramidia. Several tyrannosaur fossils have been reported from this unit (Ebersole and King, 2011).

Eutaw Formation. The Santonian strata of southeastern North America produce the first complete non-avian dinosaur faunas from the Late Cretaceous that are distinctly ‘Appalachian’ in composition. One of the units has preserved a non-avian dinosaur fauna dating from the late Coniacian to the Campanian is the Eutaw Formation of Alabama and Mississippi, which has preserved a diverse fauna of dinosaurs including indeterminate theropods, hadrosaurids, and possibly indeterminate ankylosaurids (Kaye and Russell, 1973; Lamb, 1996; Weishampel et al., 2004). A complete review of Alabama dinosaur material (excluding Eotrachodon orientalis) found the Tombigbee Sand Member of the Eutaw Formation to have an even more diverse fauna consisting of dromaeosaurs, indeterminate tyrannosaurs (including possibly Appalachiosaurus montgomeriensis), ornithomimosaurs, nodosaurids, Lophorhothon atopus, and a multitude of hadrosaur specimens (including one notable partial specimen in the collections of the Mississippi Museum of Natural Science) (Ebersole and King, 2011).

Campanian

Demopolis Chalk Formation. The Demopolis Chalk Formation is a marine layer deposited around 78 million years ago that has yielded the most complete skeleton of an Appalachian tyrannosaur currently known: the holotype of Appalachiosaurus montgomeriensis (Carr et al., 2005). The holotype of Appalachiosaurus montgomeriensis was found at the Turnipseed Dinosaur Site and consists of the mostly complete skull and partial skeleton of a subadult tyrannosauroid (Carr et al., 2005). Multiple phylogenetic analyses using different character lists and different taxa have consistently recovered Appalachiosaurus montgomeriensis as a close outgroup to Tyrannosauridae and slightly more derived than the other currently named Appalachian tyrannosaur Dryptosaurus aquilunguis (e.g., Carr et al., 2005; Brusatte et al., 2011; Loewen et al., 2013; Fiorillo and Tykoski, 2014; Brusatte and Carr, 2016; Brusatte et. al., 2016). Two caudal vertebrae of the holotype of A. mongomeriensis are fused, possibly due to an injury the young dinosaur sustained to the tail (Carr et al., 2005). The holotype subadult specimen is estimated to have been around 6-7 meters long (Carr et al., 2005).

Additional remains of non-avian dinosaurs from the Demopolis Chalk Formation include vertebrae, hindlimb elements, and a single tooth assignable to indeterminate hadrosaurs (Ebersole and King, 2011). These large herbivores likely constituted as a prey source for Appalachiosaurus montgomeriensis.

Mooreville Chalk, Blufftown, Coffee Sand Formations, and unnamed Missouri clay unit

The Mooreville Chalk has yielded a diverse dinosaur fauna from the Santonian and Campanian. This dinosaur fauna included at least two species of hadrosauroid dinosaur (Lophorhothon atopus and Eotrachodon orientalis), the ornithomimosaur “Ornithomimus” antiquus, the dromaeosaurid Saurornitholestes, indeterminate hadrosauroids, nodosaurids, indeterminate theropods, and notably two different avian dinosaur taxa (Lull and Wright, 1942; Langston, 1960; Olson, 1975; Dobie, 1978; Lamb et al., 1993; Lamb, 1996, 1997, 1998, 2001; Chiappe et al., 2002; Weishampel et al., 2004; Kiernan and Schwimmer, 2004; Prieto-Márquez​ et al., 2016a; Prieto-Márquez​ et al., 2016b). Its equivalent to the east, the Blufftown Formation (e.g., Schwimmer, 1993; Kiernan and Schwimmer, 2004; Ebersole and King, 2011), has preserved additional non-avian dinosaur fossils, including those assigned to indeterminate hadrosaurids, ?Albertosaurus sp. and indeterminate ornithomimids (e.g., Schwimmer et al., 1993; Ebersole and King, 2011). Schwimmer et al. (1993) noted that one element assigned to Albertosaurus was virtually indistinguishable from that of Appalachiosaurus montgomeriensis, and more recent studies have considered the Blufftown “Albertosaurus” material to be of A. montgomeriensis (Ebersole and King, 2011). The holotype of Appalachiosaurus montgomeriensis itself was also previously referred to Albertosaurus prior to its recognition as a new taxon (Carr et al., 2005).

In addition to the large tyrannosauroid Appalachiosaurus montgomeriensis, smaller theropod remains have also been recovered from these Campanian strata. The dromaeosaurid dinosaur Saurornitholestes sp. was reported from the Mooreville Chalk Formation on the basis of a tooth (Kiernan and Schwimmer, 2004), and indeterminate dromaeosaurid remains are also known from the Mooreville Chalk and Blufftown Formations (e.g., Ebersole and King, 2011). Ornithomimosaurs are represented by a single element assigned to “Ornithomimus” antiquus from the Blufftown Formation (Schwimmer et al., 1993; Ebersole and King, 2011).

Lophorhothon atopus is known from a partial skull and skeleton collected from lower Campanian Mooreville Chalk sediments outcropping in Dallas County, Alabama (Langston, 1960; Prieto-Márquez​ et al., 2016b). This hadrosauroid dinosaur was around 7.5 m in length (Schwimmer, 2002) and has been resolved as a derived hadrosauroid close to Hadrosauridae in a recent phylogenetic analysis (Prieto-Márquez​ et al., 2016a). Eotrachodon orientalis, the most recently described hadrosauroid from the Mooreville Chalk Formation, was described on the basis of a juvenile specimen estimated between 4 and 5.1 m in length (Prieto-Márquez​ et al., 2016a; Prieto-Márquez​ et al., 2016b). This specimen represents the most completely known hadrosauroid dinosaur from the landmass of Appalachia and along with other Appalachian hadrosaurid taxa suggests that the landmass was where the hadrosaurid dinosaurs may have first evolved (Prieto-Márquez​ et al., 2016a; Prieto-Márquez​ et al., 2016b). Eotrachodon orientalis may have gotten somewhat larger in size than the holotype juvenile specimen, which is thought to have been several years old at the time of death (Prieto-Márquez​ et al., 2016b). In addition to the two named taxa from the Mooreville Chalk, indeterminate hadrosaurids (including hadrosaurines) are known from both the Blufftown and Mooreville Chalk Formations, and indeterminate ornithischian remains from the Selma group may also be from these geological units (Langston, 1960; Schwimmer et al., 1993; Ebersole and King, 2011).

In addition to the hadrosauroids of the Mooreville and Blufftown Formations, the armored nodosaurids were also present. These are represented by indeterminate remains and the notable partial specimen of a juvenile nodosaur labeled RMM 1224 from the Mooreville Chalk (Langston, 1960; Lamb, 1996; Ebersole and King, 2011; Ebersole, personal commun., 2016). This specimen is the most complete nodosaur known from east of the Mississippi river (e.g., Ebersole and King, 2011) and probably represents a distinct taxon based on its stratigraphic location in comparison to other nodosaurs.

The Chronister Site of southeastern Missouri (e.g., Fix and Darrough, 2004) represents a unique chance to view the dinosaur fauna found in western Appalachia, bearing a notable assemblage corresponding to an unnamed smectite clay unit of Santonian to Campanian age overlapping in age with the Coffee Sand Formation (Ebersole, 2009) and thus perhaps with the Mooreville Chalk and Blufftown formations (Ebersole and King, 2011). The non-avian dinosaur fauna known from the Chronister site is somewhat diverse, containing both indeterminate dromaeosaurid and tyrannosauroid material, as well as a species of hadrosauroid (Fix and Darrough, 2004). This latter species, originally named Neosaurus missouriensis and incorrectly identified as a sauropod (Gilmore and Stewart, 1945), was later assigned a new genus Parrosaurus due to the name Neosaurus being occupied (Gilmore, 1945). Later, Baird and Horner (1979) assigned P. missouriensis to Hypsibema based on the similarity of their caudal vertebrae. More recent discoveries show the site is rich in dinosaur fossils warranting study (Darrough, personal commun., 2016) and in some places the site may even constitute as a bone bed (Fix and Darrough, 2004). Additional remains of Hypsibema missouriensis, including skull elements, have also been recovered (Darrough et al., 2005; Darrough, personal commun., 2016). This dinosaur is likely assignable to its own genus, Parrosaurus, as it is not only separated from the localities where the material assigned to H. crassicauda was found but also is now known from more material, which may allow for detailed description (e.g., Darrough et al., 2005). Therefore, the name Parrosaurus missouriensis is preferred herein. This hadrosauroid was of huge size, as its distal caudal vertebrae are similar in dimensions to those of Hypsibema crassicauda (Baird and Horner, 1979). As Baird and Horner (1979) suggested, the similarity of the vertebrae of these two taxa indeed suggest a relationship between the two species. The Coffee Sand has been considered equivalent in age to the Mooreville Chalk and Blufftown Formations (Ebersole and King, 2011). Additional remains from the Coffee Sand include those of an indeterminate hadrosauroids and the limb element of a possible Eotrachodon orientalis adult (Ebersole and King, 2011; Prieto-Márquez​ et al., 2016b).

Tar Heel and Coachman formations. The Tar Heel and Coachman formations, which are equivalent in age (Schwimmer et al., 2015), have produced among the most extensive Appalachian dinosaur faunas. This fauna is middle Campanian in age (e.g., Baird and Horner, 1979; Self-Trail et al., 2004; Weishampel et al., 2004; Schwimmer et al., 2015), and is most extensively known from two sites. These are the Phoebus Landing site on the Cape Fear river of southern North Carolina (Bladen County) and the Stokes Quarry Site in northern South Carolina (Darlington County) (e.g., Miller, 1967; Baird and Horner, 1979; Schwimmer et al., 2015). The former site has produced four or more different species of dinosaur (e.g., Miller, 1967; Baird and Horner, 1979; Weishampel and Young, 1996; Weishampel, 2004), whereas the latter has preserved an extensive theropod dinosaur fauna and indeterminate material from hadrosaurids (Weishampel and Young, 1996; Schwimmer et al., 2015).

The Phoebus Landing fauna includes a multitude of hadrosauroid taxa. The taxon Lophorhothon has been reported from the site (Miller, 1967; Baird and Horner, 1979; Weishampel and Young, 1996; Weishampel et al., 2004) alongside material assigned to Hadrosaurus sp. and a small unnamed taxon or juvenile hadrosaur (= “Hadrosaurus” minor) (Baird and Horner, 1979). Additional remains assignable to indeterminate hadrosaurids have also been recovered from the Phoebus Landing Site and Stokes Quarry (Miller, 1967; Baird and Horner, 1979; Schwimmer et al., 2015). A right metatarsal III recovered from the Phoebus Landing site is comparable to that of Hadrosaurus foulkii and provides evidence for the presence of an ~8 m hadrosaur in the Phoebus Landing fauna (Baird and Horner, 1979). Additionally, a partial tooth from Stokes Quarry was noted by Schwimmer et al. (2015) to compare favorably with “hadrosaurines” (Hadrosauroidea indet.). Weishampel and Young (1996) documented the discovery of many hadrosaur teeth, vertebrae, and limb material, including the partial femur of a hadrosauroid.

The behemoth hadrosauroid Hypsibema crassicauda is also known from caudal vertebrae from Phoebus Landing (Figure 7.1) and from other sites pertaining to the Tar Heel Formation (e.g., Cope, 1871; Miller, 1967; Baird and Horner, 1979; Weishampel and Young, 1996). A very large partial hadrosaur humerus from the Tar Heel Formation was described by Baird and Horner (1979) and is tentatively referred to as Hypsibema crassicauda based on its estimated complete size of 830 mm, massive for a hadrosaur (Baird and Horner, 1979). This dinosaur has been estimated at 12 m or more in length (Baird and Horner, 1979; Weishampel and Young, 1996), and based on comparisons with the vertebrae of the hadrosaurs Hadrosaurus foulkii (Cope, 1871) and Eotrachodon orientalis (Prieto-Márquez​ et al., 2016b) in comparison to the estimated size of each of these taxa (Weishampel and Young, 1996; Prieto-Márquez​ et al., 2016b), the author herein makes a tentative estimate of the size of this hadrosaur as being around 12-17 m in length. The implications of the large size attained by H. crassicauda and other Appalachian hadrosauroids are considered in the Discussion section.

Hypsibema crassicauda has been placed as a hadrosaurid and as dubious taxon within Hadrosauroidea (e.g., Weishampel and Young, 1996; Horner et al., 2004; Weishampel, 2006; Prieto-Márquez​ et al., 2016b). The author concurs with the sentiment of Baird and Horner (1979) that H. crassicauda represents a valid species among Hadrosauroidea based on its caudal vertebrae being laterally uncompressed. In any case, the vertebrae assigned to H. crassicauda represent a distinct morphotype of hadrosauroid in the Phoebus Landing fauna. Further discussion of Hypsibema as a distinct hadrosauroid may be found in the discussion.

The ceratopsian dinosaurs, though extremely rare on Appalachia, left a single indication of their presence within the Tar Heel non-avian dinosaur fauna. This record includes a derived leptoceratopsid left maxilla from sediments of the Tar Heel Formation of equivalent age to the Phoebus Landing Site (Longrich, 2016). Longrich (2016) noted that Appalachia belonging to a distinct palynofloral province may have implications for the adaptations found on the Tar Heel leptoceratopsian for the consumption of less-resistant plant matter.

The theropod dinosaurs also left behind an extensive record at Phoebus Landing. Hindlimb material comparable to Dryptosaurus aquilunguis was noted by Baird and Horner (1979). The femoral material compared to D. aquilunguis and figured by Baird and Horner (1979) may show an autapomorphic feature of this taxon. This is the presence of an ovoid fossa on the medial surface of the femur just above the distal condyles (Brusatte et al., 2011). More recently, Weishampel and Young (1996) also regarded Dryptosaurus aquilunguis as present at Phoebus Landing. This large tyrannosauroid theropod is known from a holotype specimen from the New Egypt Formation of New Jersey (e.g., Brusatte et al., 2011).

In addition to Dryptosaurus aquilunguis, material assigned to the tyrannosauroid dinosaur Appalachiosaurus montgomeriensis was reported from Stokes Quarry by Schwimmer et al. (2015). Some of these elements may be from juvenile individuals (Schwimmer et al., 2015). Therefore, two large tyrannosauroid dinosaurs were present in the Tar Heel-Coachman non-avian dinosaur fauna. Adults of both of these species probably measured from 6-9 m in length, comparable in size to the crocodylian Deinosuchus rugosus (Schwimmer, 1997; Schwimmer, 2002). An address on competition between large tyrannosauroids and D. rugosus is made in the Discussion section.

Small carnivorous theropod dinosaurs are represented by at least two taxa in the Upper Tar Heel-Coachman non-avian dinosaur fauna. Schwimmer et al. (2015) identified the dromaeosaurid Saurornitholestes langstoni from diagnostic teeth and a pedal ungual. These 1.8 m long dromaeosaurids (Currie and Koppelhus, 2005) were small predators in their environment. Additionally, two teeth were noted by Schwimmer et al. (2015) to be distinct from the Coachman Saurornitholestes material and similar to those of the western species Troodon and Dromaeosaurus, though they noted that the teeth are not sufficient to affirm the presence of either of the two taxa in the Coachman Formation. Additional teeth from small theropods have been uncovered in North Carolina (Weishampel and Young, 1996).

Remains assigned to ?Ornithomimus sp. and indeterminate ornithomimosaurs have been recovered from Phoebus Landing and Stokes Quarry, respectively (Miller, 1967; Baird and Horner, 1979; Schwimmer et al., 2015). These medium-sized feathered dinosaurs represent an important addition to the theropod diversity of the Tar Heel-Coachman non-avian dinosaur fauna.

Additionally, Schwimmer et al. (2015) mentioned “bird-like” limb elements which they assigned to Maniraptora indet. These remains are indicative of the presence of small maniraptorans within the Tar Heel-Coachman non-avian dinosaur fauna. A small, pathological metatarsal was also assigned to Theropoda indet. by Schwimmer et al. (2015) from Stokes Quarry. Thus, a population of small, maniraptoran theropods likely existed among the Upper Tar Heel-Coachman Formation ecosystem.

Bladen Formation. The Bladen Formation also preserves a record of dinosaurs from the Carolinas, but from the late Campanian. This record includes the remains of indeterminate dromaeosaurids, indeterminate tyrannosaurs, Ornithomimus sp. and indeterminate hadrosauroids (Crane, 2011). This fauna, along with that of the Donoho Creek Formation below, indicates that a fairly homogeneous dinosaur fauna persisted in the Carolinas through the Campanian.

Donoho Creek Formation. The Donoho Creek Formation of the Carolinas is slightly younger in age than the Coachman Formation, dating to the late Campanian (e.g., Schwimmer et al., 2015). This formation has not preserved as diverse of a dinosaur fauna as earlier Late Cretaceous sediments in the Carolinas. However, Schwimmer et al. (2015) reported a diverse theropod assemblage from the Donoho Creek Formation including the large tyrannosauroid Appalachiosaurus montgomeriensis, the dromaeosaurid Saurornitholestes langstoni, and indeterminate ornithomimosaurians.

Indeterminate hadrosaurid material has been reported from the Donoho Creek non-avian dinosaur fauna (Weishampel and Young, 1996; Weishampel et al., 2004; Schwimmer et al., 2015), including from skull elements (Schwimmer et al., 2015). The presence of the same two theropod taxa (A. montgomeriensis and S. langstoni) in the Coachman and Donoho Creek formations suggests that theropod faunas remained somewhat homogeneous throughout the Campanian in the Carolinas.

Merchantville Formation. The Merchantville Formation of the Atlantic Coastal Plain has preserved at least three different species of dinosaurs representing three distinct clades. Hadrosaurus foulkii is present in this formation (Gallagher, 1993; Weishampel and Young, 1996; Weishampel et al., 2004). One specimen from this unit, YPM VPPU.021795, represents an indeterminate tyrannosauroid distinct from either Appalachiosaurus or Dryptosaurus (Brownstein, 2017b). This unit is early to middle Campanian in age (e.g., Miller et al., 2004).

Woodbury Formation. Like the Merchantville Formation, the Woodbury Formation is middle Campanian in age and has preserved the remains of only Hadrosaurus foulkii (e.g., Prieto-Márquez et al., 2006; Prieto-Márquez, 2011). This medium-sized basal hadrosaurid dinosaur represents, along with the Alabama taxon Eotrachodon orientalis, an important discovery from Appalachia in regards to the evolution of hadrosaurs due to its placement as a basal hadrosaurid outside Saurolophidae (Prieto-Márquez​ et al., 2016a; Prieto-Márquez​ et al., 2016b). In addition to the holotype of Hadrosaurus foulkii, a historically important specimen described by paleontologist Joseph Leidy (Leidy, 1858) and the first somewhat complete skeleton of a dinosaur known from the Americas (Prieto-Márquez et al., 2006), hindlimb material originally assigned as the holotype of the taxon “Ornithotarsus immanis” by Cope (1869) has been more recently assigned to Hadrosaurus foulkii (Baird and Horner, 1977; Weishampel and Young, 1996). Gallagher (1997) remarked on the huge size of these remains, noting that a truly large hadrosaurid was present in the Upper Cretaceous of New Jersey. Weishampel and Young (1996) gave a length estimate of Hadrosaurus foulkii at 10 m, though the individual to which the holotype of “Ornithotarsus” immanis pertains may have approached 12 or more meters in length. Additionally, a large partial femur discussed by Gallagher (1997) from the Matawan Group (which includes the Woodbury Formation) (e.g., Gallagher, 1997) may also belong to a large individual of H. foulkii, though the extremely poor condition of this bone (Gallagher, 1997) means that any assignment to a specific taxon is nearly or completely impossible. Another occurrence of large hadrosaur possibly from the Woodbury Formation is based on the single pedal phalanx of a hadrosaur assigned to “Ornithotarsus” (=Hadrosaurus foulkii) by Edward Drinker Cope, which is a third larger than the corresponding element in the holotype of H. foulkii (Weishampel and Young, 1996).

Marshalltown Formation. The most extensive non-avian dinosaur fauna from the Campanian of New Jersey and also Delaware comes from the early late Campanian Marshalltown Formation (Sugarman et al., 1995; Miller et al., 2004) consisting of fine, quartz-rich glauconite clays (Olsson, 1988; Weishampel and Young, 1996). This dinosaur fauna consists of at least two different hadrosaur taxa, a large tyrannosauroid dinosaur, ornithomimosaurs, dromaeosaurids and nodosaurids (Lauginiger, 1984; Grandstaff et al., 1992; Gallagher, 1993; Weishampel and Young, 1996; Weishampel et al., 2004; Denton et al., 2011; pers. obs.). The Ellisdale fossil site of New Jersey in particular has produced an array of fossils assignable to at least three different species of non-avian dinosaur (e.g., Grandstaff et al., 1992; Gallagher, 1993; Weishampel and Young, 1996).

Hadrosauroid dinosaurs are represented in the Marshalltown Formation by remains assigned to the gigantic hadrosauroid Hypsibema crassicauda and the hadrosaurid Hadrosaurus sp. from the Ellisdale site (Grandstaff et al., 1992; Weishampel and Young, 1996), Hadrosaurus (including H. foukii) remains from Marshalltown exposures elsewhere in New Jersey (Gallagher, 1993; Weishampel and Young, 1996, Weishampel, 2006), and indeterminate remains from both New Jersey and Delaware (Gallagher, 1993; Weishampel and Young, 1996; Weishampel et al., 2004). Additionally, indeterminate ornithopods have been reported from the Ellisdale site (Grandstaff et al., 1992).

Nodosaurids are also present in the Marshalltown Formation (Gallagher, 1993; Weishampel and Young, 1996; Weishampel et al., 2004). Though they are known only by indeterminate remains, they represent the earliest record of nodosaurids from New Jersey and the possibility remains that they correspond to an unnamed taxon or taxa.

Theropods left a diverse fauna within the Marshalltown Formation. Dryptosaurus (sometimes assigned to D. aquilunguis) was reported from the Marshalltown by Grandstaff et al. (1992), Gallagher (1993), Weishampel and Young (1996), and Weishampel et al. (2004). Ornithomimosaur specimens, including material assigned to Ornithomimus (=“Coelosaurus”) have also been collected from the Marshalltown Formation (Gallagher, 1993; Weishampel and Young, 1996; Weishampel et al., 2004; pers. obs.). Teeth referable to indeterminate dromaeosaurids are also known from the Marshalltown Formation (Kiernan and Schwimmer, 2004; Denton et al., 2011; pers. obs.), increasing the carnivorous theropod diversity of this late Campanian unit. In addition, Grandstaff et al. (1992) reported the remains of indeterminate theropods from the Ellisdale site.

Mount Laurel/Wenonah Formations. The Mount Laurel/Wenonah Formations are latest Campanian-early Maastrichtian units from New Jersey (e.g., Gallagher, 1993) that preserve a variety of dinosaur taxa. Dryptosaurus sp. has been reported from the formations, as have indeterminate ornithomimosaurs (Weishampel et al., 2004). Additionally, material assigned to Hadrosaurus sp. has been collected from the formations along with bones from indeterminate hadrosaurids (Gallagher et al., 1993). Overall, this fauna is similar in composition to that of the Marshalltown Formation.

Coon Creek and Ripley Formations. The Coon Creek and Ripley Formations represent late Campanian deposits that are equivalent in age (e.g., Ebersole and King, 2011; Ebersole, personal commun., 2016) and have yielded a non-avian dinosaur fauna consistent with faunas from earlier in the Campanian. Ebersole and King (2011) listed hadrosaurid remains as coming from the Ripley and Coon Creek Formations. Of note is a hadrosaurid skull which was recovered from the Coon Creek Formation in Tennessee (Ebersole and King, 2011). Additionally, the partial skeletons of multiple ornithopods were noted to be recovered from the Ripley Formation (Ebersole and King, 2011).

Kanguk Formation. This Campanian/Maastrichtian age deposit lies to the north of Nunavut, Canada, and has preserved a fairly diverse assemblage of dinosaurs (e.g. Gangloff, 2012; Vavrek et al., 2014). This assemblage includes a lambeosaurine and possibly another type of hadrosaurid as well as a tyrannosauroid dinosaur (Gangloff, 2012). The lambeosaurines of the Kanguk are possibly the earliest known from the continent of Appalachia, and this fauna is the only one known from the far north of the landmass.

Maastrichtian

Navesink Formation. The Maastrichtian Navesink Formation is mainly composed of glauconitic clays (e.g., Sugarman et al., 1995; Kennedy et al., 2000; Miller et al., 2004) and has preserved the best known non-avian dinosaur fauna from the Maastrichtian of Appalachia. This extensive fauna includes a diverse assemblage of theropods, including an ornithomimosaur and two possibly distinct species of tyrannosauroid, a nodosaurid, a basal hadrosaurid, and lambeosaurines.

The hadrosaurid species found within the Navesink Formation include the medium-sized Hadrosaurus “cavatus” (=foulkii), an unnamed genus of very small hadrosaur (“Hadrosaurus” minor) currently considered a hadrosaurid of undetermined affinities, remains originally designated as the holotype of Hadrosaurus minor with the possibility that they represent juvenile remains, and an indeterminate species of lambeosaurine dinosaur (Colbert, 1948; Gallagher, 1993; Gallagher, 1997; Prieto-Márquez et al., 2006). The original specimen of Hadrosaurus minor consisted of dorsal vertebrae, and has been rendered a nomen dubium (Horner et al., 2004). Thus, the Navesink specimen described by Colbert (1948) has been referred to as “Hadrosaurus” minor (e.g., Weishampel et al., 2004; Weishampel, 2006). While Baird and Horner (1977) suggested the Navesink “Hadrosaurus” minor specimen was closely related to the saurolophine Edmontosaurus from the American west, more recent studies have suggested the taxon to be an unresolved taxon within “Hadrosaurinae” (=Saurolophinae) and as a hadrosaurid of uncertain affinities (Horner et al., 2004; Prieto-Márquez et al., 2006). Prieto-Márquez et al. (2006) noted that referral of “H.” minor to Edmontosaurus would be equivocal. Furthermore, the presence of multiple species of basal hadrosaurids and non-hadrosauroids on Appalachia suggests a higher likelihood of “Hadrosaurus” minor being of a basal phylogenetic position among the hadrosaurs.

In addition to the hadrosaurids, nodosaurid remains have also been recovered from the Navesink Formation. This clade of armored dinosaurs is represented by a single vertebra (e.g., Gallagher, 1993; Weishampel et al., 2004; Weishampel, 2006). As nodosaurid remains have been recovered from the somewhat older Campanian Marshalltown Formation in New Jersey, the possibility that the Navesink vertebrae represents a distinct taxon from the Marshalltown animal is certainly possible. Regardless, this vertebrae certainly shows that another distinct group of herbivorous dinosaurs was present alongside the hadrosaurids in the Navesink ecosystem.

Theropods also left a somewhat diverse fauna behind in the Navesink Formation. The tyrannosauroids are represented by remains attributable to Dryptosaurus aquilunguis (Weishampel and Young, 1996; Weishampel, 2006), a tibia, AMNH 2550, of an unnamed tyrannosauroid (=“Laelaps” macropus) (e.g., Holtz, 2004; Weishampel et al., 2004; pers. obs.), and indeterminate material, including a taxon named Diplotomodon horrificus known from a single tooth (e.g., Weishampel and Young, 1996; Holtz, 2004; Weishampel et al., 2004; Weishampel, 2006). Additionally, the holotype of “Ornithomimus” antiquus, which has most recently been regarded as a distinct taxon of ornithomimid dinosaur, is known from the Navesink (e.g., Leidy, 1865; Weishampel and Young, 1996; Makovicky et al., 2004; Weishampel et al., 2004; Weishampel, 2006; Brusatte et al., 2012).

The Navesink Formation was the only one of the few Maastrichtian Appalachian dinosaur-bearing formations included in statistical analyses herein, being compared to the Hell Creek, Lance, Horseshoe Canyon, and Javelina Formations. The Navesink was found by Miller et al. (2004) to be approximately 69-67 million years old (early to middle Maastrichtian), whereas the dinosaur fauna of the Horseshoe Canyon Formation is early and those of the Hell Creek, Lance, and Javelina Formations are late Maastrichtian in age (e.g., Weishampel et al., 2004). The results of the statistical analyses performed on these faunas may be found in Tables 27-31 of Appendix 1.

Severn Formation. The Maastrichtian (~70.7 Ma) (Hazel et al., 1984; Baird, 1986) Severn Formation of Maryland has also produced an important record of dinosaurs. This record includes the partial femur of an ornithomimosaur assigned by Baird (1986) to “Ornithomimus” antiquus, an ornithomimosaur pedal phalanx (Hartstein et al., 1986), and indeterminate hadrosauroid limb portions and partial vertebrae (e.g., Baird, 1986; Hartstein et al., 1986).

New Egypt Formation. The New Egypt Formation preserves the most complete late Maastrichtian dinosaur fauna from the eastern United States. The dinosaur remains retrieved from this formation include the holotype of the large tyrannosauroid dinosaur Dryptosaurus aquilunguis (e.g., Brusatte et al., 2011) and are housed in the AMNH FARB and ANSP collections. This partial skeleton is one of the most complete theropod dinosaur skeletons known from the Cretaceous of eastern North America (e.g., Schwimmer, 1997; Brusatte et al., 2011). One of the most intriguing features of D. aquilunguis are its large hands and massive manual ungual. The hadrosaurid dinosaurs from the New Egypt Formation include lambeosaurines, the dubious taxon Hadrosaurus minor, and indeterminate forms (e.g., Colbert, 1948; Weishampel and Young, 1996; Weishampel et al., 2004; Prieto-Márquez et al., 2006; Weishampel, 2006).

Kingstree Formation Equivalent. This unit is late Maastrichtian in age and has preserved the vertebra of an indeterminate theropod dinosaur (Schwimmer et al., 2015).

Prairie Bluff Formation. The late Maastrichtian Prairie Bluff Formation has preserved the vertebra of an indeterminate hadrosaur (Ebersole and King, 2011; George Phillips, personal commun., 2015).

Owl Creek Formation. The Owl Creek Formation of late Maastrichtian age has preserved an extremely important record of a single type of non-avian dinosaur. This is the single tooth of a possibly chasmosaurine ceratopsid (Farke and Phillips, 2017).

RESULTS

Aptian Dinosaur Faunas. Because the Arundel Clay has been dated to the upper Aptian to Albian (e.g., Kranz, 1998; Lipka et al., 2006), it was compared with two well-known upper Aptian to Albian units of the western United States: the Ruby Ranch Member of the Cedar Mountain Formation (e.g., Kirkland et al., 1999; Mori, 2009) and the Cloverly Formation (e.g., Chen and Lubin, 1997). The age of the Cloverly Formation is not well-constrained, but several studies regarding Ostrom’s (1970) units V-VII have found an Aptian-Albian age for those sediments with dates that range from about 113-108 Ma (Burton et al., 2006; Zaleha, 2006; Farke et al., 2014). However, D’Emic and Britt (2012) found a much younger age of about 103 Ma for sediments corresponding to unit VI or VII of Ostrom (1970) (Farke et al., 2014). The age of the Ruby Ranch member is also relatively unconstrained, with some estimates placing the unit from 120-108 Ma and others at around 104 Ma, overall corresponding to the Aptian and Albian (Mori, 2009; Chure et al., 2010). Units V-VII of the Cloverly Formation represent fluvial to overbank and lacustrine environments (e.g., Ostrom, 1970; May, 1992), whereas the environment represented by the Ruby Ranch Member was a semi-arid one punctuated by low-sinuosity rivers and ephemeral ponds (e.g., Harris, 1980; Kirkland et al., 1999; Kirkland and Madsen, 2006). Though depositional differences between these formations certainly hinder precise statistical analysis by causing possible biases, the author emphasizes that Aptian dinosaur faunas containing several taxa are lacking in North America save for very few units (e.g., Weishampel et al., 2004).

Analytic comparisons of the Arundel Clay fauna and those of these two units (Table 1 of Appendix 1) show the Arundel fauna is somewhat similar in composition to that of the Ruby Ranch in containing Deinonychus, Tenontosaurus, Acrocanthosaurus, or a similar taxon, a large nodosaurid, and a large titanosauriform (e.g., Leidy, 1865; Marsh, 1888; Kranz, 1996; Weishampel, 2006; Ostrom, 1970; Weishampel et al., 2004; Mori, 2009; Woodruff, 2012; D’Emic and Foreman, 2012; Mannion et al., 2013; Oreska et al., 2013). Notably, ornithomimosaurs and neoceratopsians are absent from the Ruby Ranch Member, though they are present in both the Arundel and the Cloverly Formation along with a large nodosaurid (Sauropelta), Deinonychus, Acrocanthosaurus, Tenontosaurus, ornithomimosaurs, and titanosauriforms (Ostrom, 1969, 1970, 1976; Kranz, 1996; Chinnery et al., 1998; Makovicky and Sues, 1998; Weishampel et al., 2004; Gignac and Makovicky, 2010;Woodruff, 2012; d’Emic et al., 2012; Oreska et al., 2013; Farke et al., 2014; Brownstein, 2017a). Nevertheless, the Arundel ceratopsian material remains problematic (e.g., Farke et al., 2014), and so future work on the Arundel fauna will be needed to better comparisons between these formations. Statistical comparisons of these faunas show medium to medium-high similarity (50-70% Simpson Similarity index values, 0.5-0.6) on the family level between the Arundel and these two units, although the same comparisons yield low genus level similarity when measured with the Simpson similarity index (30-50%) and Jaccard coefficient (0.2-0.3) (Tables 2-5 of Appendix 1). The low genus-level similarity between the faunas is likely augmented because of the lack of specimens from the Arundel assignable to specific genera, as half the genera known from the Arundel (Deinonychus, Acrocanthosaurus, Tenontosaurus) are known from the Cloverly and Ruby Ranch faunas (Table 1 of Appendix 1). Acrocanthosaurus and Deinonychus specimens have also been collected from the Twin Mountain and Antlers formations of Texas and Oklahoma (Stovall and Langston, 1950; Cifelli, 1997; Harris, 1998; Currie and Carpenter, 2000; D’Emic et al., 2012), and in addition to the common occurrence of Tenontosaurus remains (e.g., Ostrom, 1970; Forster, 1984; Forster, 1990; Winkler et al., 1997; Weishampel et al., 2004), the ankylopollexian iguanodontians Hippodraco and Theiophytalia are present during the Aptian in the American west (Brill and Carpenter, 2006; McDonald et al., 2010). The lack of reported ornithomimosaur material from the Ruby Ranch member of the Cedar Mountain Formation is not regarded as significant, as the possible ornithomimosaur Nedcolbertia justinhofmanni is known from the slightly older Yellow Cat Member of the Cedar Mountain Formation (Brownstein, 2017a; Kirkland and Hunt-Foster, 2017).

Nodosaurids and titanosauriforms were also spread across North America during this time, with the latter also known from the Early Cretaceous of Texas (Sauroposeidon proteles, Astrophocaudia slaughteri, Cedarosaurus sp., and Titanosauriformes indet.) (e.g., Larkin, 1910; Langston, 1974; Cifelli, 1997; Wedel et al., 2000; Weishampel et al., 2004; D’Emic, 2013), from Utah (Brontomerus mcintoshi; Cedarosaurus weiskopfae) (Taylor et al., 2011), and from the Cloverly Formation of Montana and Wyoming (including Sauroposeidon) (Tidwell et al., 1999; Ostrom, 1970; Weishampel et al., 2004; Woodruff, 2012; D’Emic and Foreman, 2012; Mannion et al., 2013; Oreska et al., 2013). The nodosaurid taxon Sauropelta was present in the Aptian of the Little Sheep Mudstone of the Cloverly Formation in the western United States (e.g., Ostrom, 1970; Kirkland et al., 1997; Weishampel et al., 2004; Oreska et al., 2013). Additional fossils assigned to Sauropelta have been recovered from middle Cedar Mountain Formation (Jensen, 1984; Weishampel et al., 2004). Fossils of the nodosaurid taxa Hoplitosaurus sp. and Tatankacephalus cooneyorum have also been recovered from the middle Cedar Mountain Formation and the Cloverly Formation, respectively (Weishampel et al., 2004; Parsons and Parsons, 2009). Finally, the polacanthine Gastonia lorriemcwhinneyae was described in 2016 (Kinneer et al., 2016).

Though the lack of body fossils from the Patuxent facies and the Trinity Group in Arkansas warranted against statistical comparisons between the faunas of these and western units, several analytical similarities can be observed between them. Indeed, the Patuxent facies shares with the Cloverly Formation and other western units nodosaurids, small (= Zephyrosaurus-like) and large euornithopods, ornithomimosaurs (as does the Arkansas Trinity Group) (e.g., Quinn, 1973; Kirkland and Hunt-Foster, 2017), large theropods, and titanosauriforms (e.g., Ostrom, 1970; Weishampel et al., 2004; Kirkland et al., 1999; Mori et al., 2009; D’Emic, 2013) and thus supports the hypothesis that a relatively homogenous dinosaur fauna existed throughout land now within the United States during the Early Cretaceous.

Albian Dinosaur Faunas. The Dakota Formation is late Albian to early Cenomanian in age (e.g., Joeckel et al., 2004; Koch, 2007) and was compared with the similarly-aged Wayan, Blackleaf, and Willow Tank formations of the western United States (Varricchio et al., 2007; Bonde et al., 2012; Ullman et al., 2012; Krumenacker et al., 2017). The Wayan Formation of Idaho was found to be deposited between 101.8 and 95.5 Ma by Krumenacker (2010), who reviewed the formation’s stratigraphy. The Willow Tank Formation has been found to be between 98.5 and 98.1 million years old (e.g., Fleck, 1970; Troyer et al., 2006; Bonde et al., 2012), and the Blackleaf Formation has been dated to the late Albian and early Cenomanian (e.g., Dorr, 1985; Varricchio et al., 2007; Ullman et al., 2012). All of these western formations have been considered as overlapping in age (e.g., Bonde et al., 2012; figure 2 in Krumenacker et al., 2017). The Dakota Formation in southeastern Nebraska has been interpreted as representing fluvial to estuarine environments (e.g., Joeckal et al., 2004), whereas the Dakota Formation in Kansas has been interpreted as a coastal plain (e.g., Eaton, 1960), and the Blackleaf, Wayan, and Willow Tank formations all seemingly represent fluvial-deltaic environments (e.g., Kirkland et al., 1999; Bonde et al., 2008; Ullman et al., 2012; Krumenacker et al., 2017). Thus, these formations were compared due to their similar paleoenvironments and ages (Table 6 of Appendix 1). Although these formations are not as well-known as those from the Cenomanian (e.g., Krumenacker et al., 2017), the majority share the presence of iguanodonts and ankylosaurs. Genus level comparisons of these formations’ faunas yielded low values for both the Simpson similarity index and Jaccard coefficient, yet family level comparisons yielded a medium-high (50-70%; 0.5-0.7) Simpson similarity index value between the faunas of the Dakota and Wayan formations (Tables 7-10 of Appendix 1) and lower Simpson similarity index values between the Dakota and the other western faunas. The Simpson similarity index and Jaccard coefficient values found for comparisons of the Dakota with the Blackleaf and Willow Tank formations’ faunas were also low (Tables 7-10 of Appendix 1). Family-level comparisons between the Dakota and Paluxy formations yielded a 100% Simpson similarity index and a 0.6 Jaccard similarity index value.

Although the Paluxy is middle Albian in age (112.2-106 Ma) (Jacobs and Winkler, 1998; D’Emic, 2013) and the Dakota, Wayan, Blackleaf and Willow Tank formations were deposited in the late Albian to early Cenomanian (e.g., Liggett, 2005; Varricchio et al., 2007; Bonde et al., 2012; Krumenacker et al., 2017), the scarcity of dinosaur-bearing deposits from this time in North America and the relatively well-documented state of the Paluxy Formation fauna warranted statistical comparison between it and the faunas of the other aforementioned sedimentary units. Genus level similarity for both indices used was 0.0 between the Paluxy and all other formations, whereas family-level comparisons resulted in low Simpson similarity index and Jaccard coefficient values between the Paluxy fauna and those of all other formations save for the Dakota (Tables 7-10 of Appendix 1).

Because of the limited number and diversity of dinosaur taxa from the Paw Paw and Glen Rose Formations, statistical comparisons between these and other formations were not conducted. The Paw Paw formation was deposited during the Late Albian (e.g., Lee, 1996), thus being similar in age to the Dakota, Wayan, Blackleaf, and Willow Tank Formations (e.g., Liggett, 2005; Varricchio et al., 2007; Bonde et al., 2012; Ullman et al., 2012; Krumenacker et al., 2017). Like these other formations, the Paw Paw evinces that nodosaurids continued being widespread across North America during the Albian. The Glen Rose fauna further shows that large theropods, titanosauriforms, and Tenontosaurus were included in the Aptian-Albian fauna of North America.

Cenomanian Dinosaur Faunas. The non-avian dinosaur fauna of the deltaic plains (e.g., Main, 2005; Main, 2010; Main, 2013) represented by the Woodbine Formation included large carcharodontosaurs, dromaeosaurs, ornithomimosaurs, indeterminate theropods (including possible tyrannosauroids), hadrosauroids, and nodosaurids (e.g., Main, 2005, 2013). Possible allosauroid and carcharodontosaurid dinosaurs are known from the Mussentuchit Member of the Cedar Mountain Formation (Siats meekorum) (Zanno and Makovicky, 2013) and from the Turney Ranch Formation (Thayer and Ratkevich, 1995). Dromaeosaurids are also known from the Mussentuchit Member of the Cedar Mountain Formation (Garrison and Brinkman, 2007) and from the Blackleaf Formation (Ullman et al., 2012). The nodosaurid Animantarx caroljonesa is also known from the Mussentuchit Member of the Cedar Mountain Formation (Carpenter et al., 1999). Adding to similarities between the Woodbine Formation and the Mussentuchit Member of the Cedar Mountain Formation is the presence of the hadrosauroid dinosaur Eolambia in the latter unit (Kirkland et al., 1998). This taxon has been found as an outgroup to hadrosauridae behind Protohadros or as a sister taxon to P. byrdi in phylogenetic analyses (Prieto-Marquez and Norell, 2010; Wenhao and Godefroit, 2012), although another study found it to be a sister taxon of Probactrosaurus and Protohadros to be a more derived hadrosauroid (McDonald et al., 2012).

The Woodbine Formation was statistically compared to the Mussentuchit Member of the Cedar Mountain Formation of Utah and the Dunvegan Formation of western Canada (Tables 11-15). The Mussentuchit Member of the Cedar Mountain Formation is latest Albian to Cenomanian in age (~104-98 Ma) (e.g., Cifelli et al., 1997; Chure et al., 2010) and represents fluvial to deltaic environments (e.g., Kirkland et al., 1998; Carpenter et al., 1999; Kirkland et al., 1999; Garrison and Brinkman, 2007; McDonald et al., 2012; Ullman et al., 2012; Main, 2013; Zanno and Makovicky, 2013; Krumenacker et al., 2017), whereas the Dunvegan Formation represents a middle Cenomanian-age delta complex (e.g., Burns and Vavrek, 2014). The Lewisville Member of the Woodbine Formation, to which the Arlington Archosaur Site corresponds, is middle Cenomanian in age (~96-95 million years old) and preserves a coastal deltaic environment (e.g., Main, 2005; Main, 2013), making it closely comparable to the Dunvegan Formation and somewhat so to the Mussentuchit. The faunas of these units and the results of statistical analysis of the similarity of those faunas are listed in Tables 11-15 of Appendix 1.

Because the record of dinosaurs from the Raritan facies is so scant, no statistical comparisons were made between it and other Cenomanian units’ faunas. It is notable that the Raritan shares with the Mussentuchit, Wayan, and Blackleaf formations tyrannosauroid dinosaurs (e.g., Baird, 1989; Kirkland et al., 1998; Varricchio et al., 2007; Ullman et al., 2012; Zanno and Mackovicky, 2013). The size of the Raritan facies tyrannosauroid is relatively large compared to Cenomanian North American tyrannosauroids (pers. obs.). The dinosaur trackways of the Raritan are additionally important for being the only Late Cretaceous dinosaur tracks known east of the Mississippi (e.g., Baird, 1989).

Coniacian/Santonian Dinosaur Faunas. The Niobrara Chalk is late Coniacian to Santonian in age in the general area surrounding Hackleberry Creek (where Niobrarasaurus, “Heirosaurus”, indeterminate nodosaurids, and the caudal vertebrae of an indeterminate hadrosaurid have been found) and late Santonian in Logan County (where the holotype of Claosaurus was uncovered) (e.g., Carpenter et al., 1995; Weishampel et al., 2004; Everhart and Ewell, 2006; Prieto-Márquez​ et al., 2016a; Prieto-Márquez​ et al., 2016b). Thus, the Niobrara Formation is comparable in age to the Eutaw Formation, which has been dated to the Santonian (87-83 Ma) (e.g., Weishampel et al., 2004; Ebersole and King, 2011; Prieto-Márquez​ et al., 2016a; Prieto-Márquez​ et al., 2016b). Additionally, the Eutaw represents marginal marine to marine deposits and was formed during a sea transgression (Liu, 2009), somewhat comparable to the marine setting of the Niobrara Formation (e.g., Carpenter et al., 1995; Liggett, 2005; Ebersole and Ewell, 2006). Both of these formations share hadrosaurids, nodosaurids, and non-hadrosaurid hadrosauroids, whereas only hadrosaurids are observed in the latest Santonian (~84.5-83.5 Ma) Milk River Formation (thus overlapping with the Eutaw Formation entirely) (e.g., Payenberg et al., 2002; Weishampel et al., 2004; Ebersole and King, 2011; Prieto-Márquez​ et al., 2016a; Prieto-Márquez​ et al., 2016b). Additionally, the fauna of the Milk River Formation differs from those of the Eutaw and Niobrara, other Coniacian-Santonian, and Campanian Appalachian formations (e.g., Tables 17, 22 of Appendix 1; Carpenter et al., 1995; Ebersole and Ewell, 2006; Gallagher, 1993; Weishampel et al., 2004; Denton et al., 2011; Ebersole and King, 2011; Schwimmer et al., 2015) in containing pachycephalosaurids, centrosaurines, troodontids, and tyrannosaurids. Thus, it seems that major differences in the composition of dinosaur faunas emerged between Laramidia and Appalachia sometime during the “mid”-Cretaceous. Statistically, this hypothesis is supported by the low Simpson similarity index value at the family level (40%) found between the Eutaw and Milk River formations, the low Jaccard coefficient (0.2) value found from comparisons of Coniacian-Santonian Appalachian faunas (Eutaw Niobrara faunas) with that of the Milk River Formation, and the 100% Simpson similarity index value found between the Niobrara and Eutaw faunas at the family level (Tables 17-21 of Appendix 1). Unfortunately, the poor record of dinosaurs during the Turonian-Santonian of North America (e.g., Carpenter et al., 1995) hinders more precise estimates of when such faunas experienced vicariance. Indeed, all comparisons Coniacian-Santonian formations at the genus level yielded values of 0.0 for both metrics.

Though the Santonian McShan Formation preserves a heavily incomplete dinosaur fauna (e.g., Ebersole and King, 2011) and thus was not compared statistically to other Appalachian and Laramidian faunas, the presence of tyrannosauroids and hadrosauroids in its fauna supports the notion that Appalachian and Laramidian faunas had already differentiated appreciably during the Santonian.

Campanian Dinosaur Faunas. Among the several dinosaur-bearing units of the Campanian of Appalachia, the Mooreville Chalk, Blufftown and Coffee Sand formations and unnamed Missouri clay, the Tar Heel and Coachman formations, and the Marshalltown Formation were used in statistical comparisons with several western Campanian-age strata as well as with each other for the investigation herein of dinosaur provincialism on Appalachia. The Mooreville Chalk, Blufftown, and Coffee Sand formations and the unnamed Missouri clay all latest Santonian to middle Campanian in age (e.g., Ebersole, 2009; Ebersole and King, 2011; Prieto-Márquez​ et al., 2016a; Prieto-Márquez​ et al., 2016b), with the marine Mooreville Chalk being approximately 80-83 million years old (e.g., Prieto-Márquez​ et al., 2016b) and equivalent with the Blufftown and Coffee Sand formations (e.g., Schwimmer et al., 1993; Ebersole and King, 2011), and the apparently terrestrial (representative of an oxbow lake) (Fix and Darrough, 2004) Chronister site also apparently Campanian in age (e.g., Fix and Darrough, 2004; Ebersole, 2009). The fauna of these equivalent formations thus correspond in age to the 81-76 million year old Wahweap (Sampson et al., 2013a) and the Oldman (coeval with the Wahweap; e.g., Roberts et al., 2005; Gates et al., 2010) formations.

The dinosaur-bearing sites of the Tar Heel and Coachman formations, as noted previously, are middle Campanian in age, with the upper portion of the Tar Heel (Tar Heel II sequence) dated to be between 78.7-74.5 million years ago. This range overlaps somewhat with that of the Marshalltown Formation, which may be slightly younger at 75.7-71.2 million years of age (e.g., Miller et al., 2004; Self-Trail et al., 2004; Harris and Self-Trail, 2006; Schwimmer et al., 2015). Thus, the Marshalltown and Tar Heel-Coachman faunas overlap by at least 1.2 million years, the former overlapping with the main fossiliferous zones of the Dinosaur Park, Kaiparowits, upper Judith River, and lower Kirtland formations in age by approximately 1.5 million years and the latter by at least 2 million years (the main fossiliferous zones of these latter four units being between ~76-74 Ma; e.g., Eberth and Hamblin, 1993; Rogers et al., 1993; Horner et al., 2001; Eberth and Deino, 2005; Roberts et al., 2005; Hanson et al., 2006; Lucas et al., 2006; Gates et al., 2010). The Kaiparowits Formation has been dated to 76.6-74.4 Ma (Sampson et al., 2013a), the Dinosaur Park Formation to 76.9 and 75.8 Ma (e.g., Gates et al., 2010; Gates et al., 2012; Sampson et al., 2013a), the Hunter Wash Member (lower Kirtland Formation) to between 74.5-74.1 Ma (e.g., Gates et al., 2010), and the the Judith