At top: our Prospectiuni fieldwork vehicles. Lower left: the amazing and distinctive foot of the Romanian theropod Balaur bondoc. Lower right: reconstructed Zalmoxes skeleton at IRSNB, Brussels, image by Ghedoghedo, CC BY-SA 3.0

Over the past several years, I and colleagues have aimed to improve our knowledge of the Late Cretaceous fauna of the Haţeg Island, a landmass that corresponds to modern-day Romania. This work is led by the Transylvanian Museum Society’s Mátyás Vremir and the University of Bucharest’s Zoltán Csiki-Sava and involves researchers based in the UK and USA as well as Romania. We’ve found a lot of new stuff in the field, much of it at localities discovered within recent years by Mátyás. Our work has involved azhdarchid pterosaurs (Vremir et al. 2013, 2015), archaic birds and related theropods (Dyke et al. 2012, Cau et al. 2015) and turtles (Dyke et al. 2015). There are also in-prep projects on multituberculate mammals, crocodyliforms and lizards.

Our latest contribution has just appeared. It’s a paper that reviews our knowledge of the faunas concerned and aims to better pin down their stratigraphic and temporal context, effectively providing the first comprehensive stratigraphic framework for these vertebrate-bearing strata (Csiki-Sava et al. 2015a).

This montage - showing the vertebrate groups reported from the localities of the Haţeg Basin - gives some idea of how diverse the Upper Cretaceous Romanian vertebrate record is. Diagram from Csiki-Sava et al. (2015a).

This is therefore one of those papers that does a good job of showing just how rich and diverse the Haţeg Island fauna is. Zoltán and colleagues also recently discussed the region’s vertebrate assemblage in another review paper (Csiki-Sava et al. 2015b). So, yes, we have a quite detailed view of the region’s vertebrate fauna, though of course there’s much left to discover and there are a great many taxa that are as yet known only from fragments and which remain enigmatic.

The dwarf, island-dwelling dinosaurs of this fauna – the weird archaic hadrosaurs, miniature titanosaurian sauropods and small ankylosaurs – are relatively familiar, and you might say the same about the giant azhdarchid pterosaur Hatzegopteryx (Buffetaut et al. 2002, 2003). But there’s also a rich assemblage of small animals, including albanerpetids* (a group of terrestrial, superficially salamander-like amphibians), frogs of several sorts, multituberculates, lizards, snakes and crocodyliforms. I’m especially interested in the lizards and an article on them is forthcoming, I promise. Haţeg Island lizard fossils don’t just include bones and teeth, but eggshell fragments too, much of which is the dispersituberculate type characteristic of gekkotans. We report assorted new lizard fossils from several Romanian localities (Csiki-Sava et al. 2015a).

* I’ve previously been calling these animals ‘albanerpetontids’. But this seems to be incorrect: they should be Albanerpetidae, not Albanerpetontidae. Thanks to Christian Kammerer for pointing this out.

Some of the new fossils we report. The specimens here represent albanerpetids (C), frogs (D), lizards (E), crocodyliforms (F-G), snakes (H-I), small theropods (J-O), nodosaurids (P), and multituberculates (R-T). Scale bars = 1 mm. From Csiki-Sava et al. (2015a).

The three classic Romanian maniraptoran taxa. As you can see, there isn't a tremendous amount to go on. The Elopteryx and Heptasteornis illustrations are from Naish & Dyke (2004); the Bradycneme photos are (c) NHMUK.

We also report a set of new theropod remains. Frustratingly, most Upper Cretaceous Romanian theropod specimens consist of isolated teeth and fragmentary specimens: only the paravian Balaur bondoc – originally described as a dromaeosaurid (Csiki et al. 2010, Brusatte et al. 2013) but more recently argued to be a jeholornithid-grade member of the bird lineage (Cau et al. 2015) (and recently discussed here on Tet Zoo) – is represented by good remains. Of the new specimens we discuss and illustrate, some of the teeth have been assigned to the Richardoestesia morphotype (I really don’t think that all these teeth, found at so many locations and horizons worldwide, represent the same one animal). Others are of troodontid- or dromaeosaurid-like morphology. We also report a new partial femur that looks referable to the poorly known maniraptoran Elopteryx (Csiki-Sava et al. 2015a). Incidentally, there is as yet no indication whatsoever of large theropods in the Haţeg Island assemblage. Hold that thought, since we’ll come back to it at some point in the future.

A really weird thing about several of the Haţeg Island theropods is that the outside surfaces of their bones possess a distinctive ‘wrinkled’ texture that consists of subparallel, raised ridges. Nobody has any firm idea what’s going on here. The texture doesn’t seem to be pathological. Rather, it’s a normal feature of these animals. If this is so, it seems mightily suspicious that the texture is present in animals that are supposed to belong to wholly different (and phylogenetically disparate) maniraptoran lineages, including alvarezsaurids, Jeholornis-grade avialans, and dromaeosaurids.

Bradycneme, reconstructed as a giant owl by Gregory Irons in the 1980 book The Last of the Dinosaurs.

Indeed, another interesting thing about the taxa concerned is that they’ve been re-interpreted on several occasions as the members of different theropod groups. My favourite of these suggestions is that two of them – Heptasteornis and Bradycneme – might have been giant archaic owls (Harrison & Walker 1975). Back in 2004, Gareth Dyke and I argued that Heptasteornis might actually be an alvarezsaurid (Naish & Dyke 2004). But proposals of this sort are hypotheses, and hypotheses that are liable to be overturned as we learn more about the animals concerned, especially when they’re based on horribly incomplete, fragmentary specimens. Heptasteornis is, after all, based only on the incomplete distal ends of tibiotarsi.

What seems more likely – it’s now been mentioned several times by several researchers – is that the various specimens don’t represent disparate lineages at all, but close relatives within an endemic clade (Csiki-Sava et al. 2015a). Some might be synonymous, perhaps being different bits of the same one animal. You might recognise this as being similar to the ‘Holy-Grail-o-saurus Hypothesis’ discussed here previously in connection with Wealden theropods and Eotyrannus. Oh, yeah, Eotyrannus. That.

The 'Holy-Grail-o-saurus Hypothesis' as once applied to the (non-Romanian!) British theropod Eotyrannus. It failed: those different Wealden theropods really are from different Wealden theropods. This illustration is a slide from a talk I gave in 2013.

New bits and pieces of lizards and dinosaurs are all very nice. But the raison d’etre of this paper is to better pin down the age of the localities (and hence their constituent faunas) better. Views on the ages of these strata have varied considerably since they were discovered in the late 1800s. They were initially suspected to be Paleogene or Miocene, and – for some of the locations – this view was the dominant paradigm really recently. Some were thought to date to the Miocene until just a few years ago, the discovery of undoubtedly Cretaceous dinosaur bones and palynomorphs finally causing opinion to shift.

Late Cretaceous Romania was home to several titanosaurian sauropods, some of which were really quite small (for sauropods). This is a life-sized model of Magyarosaurus at Centrul de Ştiinţă şi Artă, General Berthelot, beautifully made by Brian Cooley. It's super-accurate.

What we argue in the new paper is that several of the faunas are upper Campanian or lower Maastrichtian, and thus date to perhaps 72 Ma or so. Others are mid Maastrichtian, and others upper Maastrichtian. It’s complicated, and it can be hard to work out which locality specific historical specimens or taxa might come from since original collection data on them is sometimes scant. Regardless, many surprises emerge. Balaur is ‘only’ known from the lower and mid Maastrichtian while some taxa (like the turtle Kallokibotion and the Zalmoxes species) seem to have persisted across most of these time zones (Csiki-Sava et al. 2015a). Zalmoxes shqiperorum is seemingly around for an impressive 5 Ma... do the specimens concerned really all represent the same one species? Incidentally, a Zalmoxes specimen described in the paper (Csiki-Sava et al. 2015a) represents an even smaller individual (represented by a 72 mm long tibia) than the one we previously described in 2013 (Brusatte et al. 2013b).

The presence of large titanosaurs throughout the time-frame indicates that there was not one progressive dwarfing event but that things were more complicated (Csiki-Sava et al. 2015a). Did dwarfing happen independently several times? Did it only affect one lineage? Were dwarf populations ‘contaminated’ with big-bodied animals that swam in from adjacent regions? We don’t yet know.

Closeup of the head of Cooley's Magyarosaurus model. Photo by Darren Naish.

So, Haţeg Island animals don’t represent one fauna, but several distinct ones separated quite considerably in time. This makes it more difficult to use the Haţeg Island animals as a whole to make generalisations about events and trends in the region, and also means that animals from different regions shouldn’t be assumed to be contemporaneous.

More work on this diverse and fascinating island-endemic fauna is coming – on the azhdarchids, the lizards, the multituberculates, the theropods and more. But this new study is a significant one, sure to prove integral to ongoing research in the research, and sure to prove essential as goes our views on latest Cretaceous animal diversity and evolution in Europe.

Refs - -

Brusatte, S. L., Vremir, M., Csiki-Sava, Z., Turner, A. H., Watanabe, A, Erickson, G. M. & Norell, M. A. 2013a. The osteology of Balaur bondoc, an island-dwelling dromaeosaurid (Dinosauria: Theropoda) from the Late Cretaceous of Romania. Bulletin of the American Museum of Natural History 374, 1-100.

Brusatte, S. L., Vremir, M., Watanabe, A., Csiki-Sava, Z., Naish, D., Dyke, G., Erickson, G. M. & Norell, M. A. 2013b. An infant ornithopod dinosaur tibia from the Late Cretaceous of Sebeş, Romania. Terra Sebus. Acta Musei Sabesiensis 5, 627-644.

Buffetaut, E., Grigorescu, D. & Csiki, Z. 2002. A new giant pterosaur with a robust skull from the latest Cretaceous of Romania. Naturwissenschaften 89, 180-184.

Buffetaut, E., Grigorescu, D. & Csiki, Z. 2003. Giant azhdarchid pterosaurs from the terminal Cretaceous of Translyvania (western Romania). In Buffetaut, E. & Mazin, J.-M. (eds) Evolution and Palaeobiology of Pterosaurs. Geological Society Special Publication 217. The Geological Society of London, pp. 91-104.

Cau, A., Brougham, T. & Naish, D. 2015. The phylogenetic affinities of the bizarre Late Cretaceous Romanian theropod Balaur bondoc (Dinosauria, Maniraptora): dromaeosaurid or flightless bird? PeerJ 3:e1032.

Csiki-Sava, Z., Buffetaut, E., Ősi, A., Pereda-Suberbiola, X. & Brusatte, S. L. 2015b. Island life in the Cretaceous – faunal composition, biogeography, evolution, and extinction of land-living vertebrates in the Late Cretaceous European archipelago. ZooKeys 469, 1-161.

Csiki, Z., Vremir, M., Brusatte, S. L., Norell, M. A. 2010. An aberrant island-dwelling theropod dinosaur from the Late Cretaceous of Romania. Proceedings of the National Academy of Sciences of the United States of America 107, 15357-15361.

Csiki-Sava, Z., Vremir, M., Vasile, S., Brusatte, S. L., Dyke, G., Naish, D., Norell, M. A. & Totoianu, R. 2015a. The East Side Story – The Transylvanian latest Cretaceous continental vertebrate record and its implications for understanding Cretaceous-Paleogene boundary events. Cretaceous Research http://dx.doi.org/10.1016/j.cretres.2015.09.003

Dyke, G. J., Vremir, M., Brusatte, S., Bever, G., Buffetaut, E., Chapman, S., Csiki-Sava, Z., Kellner, A. W. A., Martin, E., Naish, D., Norell, M., Ősi, A., Pinheiro, F. L., Prondvai, E., Rabi, M., Rodrigues, T., Steel, L., Tong, H., Vila Nova, B. C. & Witton, M. 2014. Thalassodromeus sebesensis – a new name for an old turtle. Comment on “Thalassodromeus sebesensis, an out of place and out of time Gondwanan tapejarid pterosaur”, Grellet-Tinner and Codrea. Gondwana Research 27, 1680-1682.

Dyke, G., Vremir, M., Kaiser, G. & Naish, D. 2012. A drowned Mesozoic bird breeding colony from the Late Cretaceous of Transylvania. Naturwissenschaften 99, 435-442.

Harrison, C. J. O. & Walker, C. A. 1975. The Bradycnemidae, a new family of owls from the Upper Cretaceous of Romania. Palaeontology 18, 563-570.

Naish, D. & Dyke, G. J. 2004. Heptasteornis was no ornithomimid, troodontid, dromaeosaurid or owl: the first alvarezsaurid (Dinosauria: Theropoda) from Europe. Neues Jahrbuch für Geologie und Paläontologie, Monatshefte 2004, 385-401.

Vremir, M., Kellner, A. W. A., Naish. D. & Dyke, G. J. 2013. A new azhdarchid pterosaur from the Late Cretaceous of the Transylvanian Basin, Romania: implications for azhdarchid diversity and distribution. PLoS ONE 8(1): e54268.

Vremir, M., Witton, M., Naish, D., Dyke, G., Brusatte, S. L., Norell, M. & Totoianu, R. 2015. A medium-sized robust-necked azhdarchid pterosaur (Pterodactyloidea: Azhdarchidae) from the Maastrichtian of Pui (Haţeg Basin, Transylvania, Romania). American Museum Novitates 3827, 1-16.