All specimens are three-dimensionally preserved with little or no distortion. Several bones have been removed from the matrix, but their foramina, other openings and fractures are still filled with carbonate. The holotype skull is prepared from dorsally and both lateral sides, but ventrally embedded in matrix ( Fig 3A ). A large crack dorsally at the cranial table has been filled with glue. The juvenile skull DFMMh/FV 605 has been prepared completely. Teeth are preserved in situ on both skulls and the isolated dentary (DFMMh/FV 790.12). Both skulls were slightly crushed dorsally during diagenesis, and in particular DFMMh/FV 200 shows medially tilted dermal bones because of the distortion of the skull. Investigations by μCT of the juvenile skull DFMMh/FV 605 supplement the description. Most vertebrae lack their neural spines. None of the bones shows signs of abrasion or weathering, but several bones have fractures along their surfaces. Completeness and preservation of small cranial elements and other bones indicate a short distance transport before burial. Details on preservation of the skeletal regions are given together with the description.

Skull

External naris. On both specimens (DFMMh/FV 200 and DFMMh/FV 605), the indentation of the medial margin of the premaxilla indicates that the external naris was positioned in the rostral half of the bone (reaching the rostral skull margin) and faced dorsally (Figs 4A, 5A and 5C). The nasopremaxillary suture, well exposed in DFMMh/FV 200 suggests together with the medial premaxillary margin that a median thin spine of the nasals reached the caudal margin of the external naris. It remains unclear if there is a complete separation of left and right naris by a median bone bar of the nasal.

Antorbital foramen. The right maxilla of DFMMh/FV 200 shows an indentation of the caudomedial margin associated with a rostrally positioned depression on the maxilla that is interpreted as the margin of a small antorbital foramen (Fig 4A). The antorbital foramen of DFMMh/FV 200 is proportionally only slightly reduced in size in comparison to DFMMh/FV 605. The antorbital foramen of DFMMh/FV 605 is located rostral to the orbit and is rostrally, rostromedially and ventrally restricted by the maxilla (Fig 5C and 5D). The caudal and caudomedial margin are bounded by the lacrimal. The antorbital foramen is longitudinally oval in outline and a slight antorbital fossa is developed in the maxilla of DFMMh/FV 605. The length of the antorbital foramen is 9% that of the orbit (Fig 5C).

Orbit. The large, longitudinally oval orbit is 54% longer than it is wide in DFMMh/FV 200 (Fig 4B) and 27% longer than it is wide in DFMMh/FV 605 (Fig 5A and 5C). Rostrolaterally, the orbit is bounded by the lacrimal, rostromedially by the prefrontal. Its lateral and caudolateral margins are formed by the jugal, which excludes the maxilla from the orbit. The xpillarlike postorbital bar separates the orbit caudally from the infratemporal fenestra. The caudomedial margin of the orbit is restricted by the frontal, which is not elevated from the orbital margin, and the caudal margin of the orbit by the postorbital.

Supratemporal foramen. In DFMMh/FV 200, the supratemporal foramen is irregular in shape, with a rounded rectangular rostromedial and rostrolateral margin, and a narrow and rounded caudal half (Fig 4A). It is 42% longer than wide. In DFMMh/FV 605, the supratemporal foramen is narrow oval-shaped and 54% longer than wide (Fig 5A). In DFMMh/FV 200, the supratemporal foramen is bounded by the postorbital along the rostral and rostrolateral margin (Fig 4A). In contrast, in DFMMh/FV 605, the rostromedial corner of the supratemporal foramen is formed by the frontal (see also “Ontogeny”) (Fig 5A). The caudomedial margin of the supratemporal foramen is bounded by the parietal in both specimens, the caudal and caudolateral margins are formed exclusively by the squamosal. The wall of the supratemporal fossa is formed rostromedially by the frontal and caudomedially by the parietal. The squamosal seems to contribute to most of the lateral part of the supratemporal fossa, but because of the poor preservation of this region in both specimens, it remains unclear if there is also a contribution of the quadrate.

Infratemporal fenestra. The infratemporal fenestra of both skulls is roughly rounded trapezoidal in outline, laterally longer than medially and tapers caudolaterally to a tip. It is 1.5 times as long as it is wide. The fenestra is bounded rostromedially by the postorbital, rostrally by the postorbital bar and laterally by the jugal. Caudomedially, the infratemporal fenestra is bounded by the squamosal and caudolaterally by the quadratojugal.

Secondary choanae. The paired secondary choanae are partly preserved in DFMMh/FV 605 (Figs 5B and 6C). The openings of the secondary choanae are positioned within the through-like depressions (choanal groove) at the rostral process of the pterygoid and are medially separated by a rounded crest. The secondary choanae are longitudinal slitlike openings placed with its caudal half in the rostral narrow process of the pterygoid. The rostral edge of the choanae is situated between the suborbital fenestrae in the palatines. Only a small, caudalmost part is positioned in the pterygoid wings. Caudal to the secondary choanae, the pterygoid surface is slightly elevated, but there is no distinct vertically high rim present. PPT PowerPoint slide

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larger image TIFF original image Download: Fig 6. DFMMh/FV 605, skull and mandible of Knoetschkesuchus langenbergensis gen. nov. sp. nov., juvenile specimen. (A) Occipital view of skull, (A1) photograph of the original specimen on the left side, (A2) interpretative drawing with labels in the middle, and (A3) reconstructed 3D data as derived from MeshLab (FOV: Ortho; only skull elements originally visible and important in the respective view are shown). (B) Caudoventral aspect of skull with basisphenoid exposed. (C) Pterygoid in ventral aspect. (D) Pterygoid in dorsal aspect. (E) Dorsal aspect of ventral skull elements, featuring quadrates, exoccipitals, basioccipital and basisphenoid. (F) Left lateral aspect of braincase wall including pterygoid, prooticum and laterosphenoid. (G) Medial aspect of left laterosphenoid and prooticum. (H) Mandible in left ventrolateral aspect. (I) Mandible in ventral aspect. (J) Mandible in dorsal aspect. For anatomical abbreviations, see text. 3D images are not to scale. https://doi.org/10.1371/journal.pone.0160617.g006

Premaxilla. DFMMh/FV 200 preserves the left premaxilla with one tooth in situ but the rostral-most portion of the bone is missing (Fig 4A). In DFMMh/FV 605, the left premaxilla is complete but without teeth and disarticulated from the rostrum, whereas only a small part of the right premaxilla is exposed (Fig 5C and 5D). The premaxilla is approximately 1.5 times wider than long. Its lateral margin forms a convexity. Its medial margin is concave and thus provides space for the external naris. The premaxilla contacts the maxilla caudolaterally with a slightly serrated rostromedially extending suture and is medially connected to the nasal by a longitudinally straight suture, thus it participates only little in the internarial bar, if at all. The 3D reconstructions revealed that the suture between premaxilla and maxilla in ventral aspect is jagged and rostromedially directed (Fig 5C and 5D).

Maxilla. The maxilla is medially bent along its long-axis. The maxilla is widest in its rostral fourth, bifurcating then into a short medial and a long lateral process. The rostral margin of the maxilla is slightly rostromedially oriented and shares a serrated suture with the premaxilla. The lateral margin of the maxilla is convex in its rostral third with a maximum curvature at the fourth maxillary tooth. Caudally to this convexity it becomes slightly concave, then straight. The medial maxillary margin, including the medial process, contacts the nasal along a sagittally aligned suture. Caudal to the nasal, the medial process of the maxilla roofs the antorbital foramen and contacts the lacrimal. A dorsal furrow at the rod-like part of the maxillary process represents the contact area to the lateral part of the lacrimal, which attaches dorsally to the maxilla (Figs 4C and 5C). Only in DFMMh/FV 605, the length of the maxillolacrimal suture is visible over approximately four maxillary alveoli and the caudal contact to the jugal (Fig 5C). The lateral process of the maxilla preserves its maximum rod-like process that thins out far caudally. Directly caudal to the lacrimal, the maxilla underlaps the jugal, which attaches dorsally on the very thin caudalmost part of the lateral maxillary process with a smooth suture. In ventral aspect, the posterior palatal branches of the maxillae meet entirely rostral to the palatines (Fig 5B). The rostralmost part of the medial suture of the ventral maxilla to the palatine lies shortly rostrally to the suborbital fenestra.

Nasal. The nasals are a wedge-like pair of bones, forming the medial third of the rostrum (Figs 4A and 5A). The elongate element is narrowest rostrally and continues between the premaxillae to send a medial spine into the external naris. Caudally, the nasal widens to reach at the contact with the prefrontal five times of its rostral width at the contact with the prefrontal. Caudally to this contact, the nasal tapers again and wedges out between the lateral prefrontal and the medial frontal level with the rostral orbital margin. The contact between the left and right nasals is a straight median suture. The lateral suture to the maxilla is restricted to the cranial half of the nasal bone and directed vertically (Fig 4A).

Lacrimal. The lacrimal of DFMMh/FV 200 possesses in dorsal and lateral aspect a massive rounded squarish body from which a delicate process descends caudolaterally (Fig 4A). The rostral and caudal margins of the lacrimal are concave and mark the boundaries of the antorbital fenestra and the orbit, respectively. The medial margin of the lacrimal is slightly wavy and contacts the maxilla with its rostral tip and the prefrontal with its medial margin. The lacrimal is nearly completely excluded from a contact with the nasal by both of these elements, and touches the nasal only with a small rostromedial tip dorsal to the antorbital foramen. Laterally, the lacrimal attaches to the maxillary process and contacts the jugal in the rostral third of the orbita (Fig 4A). In contrast, the lacrimal of DFMMh/FV 605 is more delicate than in DFMMh/FV 200, having a more robust dorsal part from which a delicate caudoventrally bent process descends (Fig 5C and 5D). The delicate caudolateral process of the lacrimal is enlarged and also forms the boundary between antorbital fenestra and orbit (Fig 5C).

Prefrontal. The prefrontal is nearly triangular in outline in dorsal view (Fig 4A and 4C). Having a nearly straight medial margin, it tapers rostrally to a tip and forms a narrow expansion laterally (Fig 5A and 5C). Caudally, the prefrontal forms another narrow expansion that represents the rostral third of the dorsal orbital margin. The medial margin of the prefrontal is bounded in its rostral half by the nasal and in its caudal half by the frontal. Craniolaterally, the prefrontal is restricted by the lacrimal, caudally it contributes to the orbital margin. The rostral margin of the orbit bears in its rostromedial half a broadened depression that comprises equal parts of lacrimal laterally and prefrontal medially (Fig 4A). This depression represents the attachment area for the palpebral. The prefrontal pillar is not exposed in DFMMh/FV 200, but preserved as a narrow and flat ventral process in DFMMh/FV 605 (Fig 5E). The prefrontal pillar is positioned in the rostromedial edge of the orbit and decends from the prefrontal body ventromedially to contact the palate (Fig 5B and 5E). The prefrontal pillar is dorsally and ventrally expanded, with a medial constriction.

Palpebral. A left and a right palpebral are preserved in the orbits of DFMMh/FV 200 (Fig 4A and 4C), and a left palpebral is preserved in DFMMh/FV 605 (Fig 5A and 5D). The palpebrals are roughly drop-shaped in outline with a convex dorsal margin that mirrors the concave medial orbital margin and a narrow rostral end. The lateral palpebral margin is straight and aligned rostrocaudally. The external surface of the palpebral is slightly vaulted and weakly sculptured. On its internal smooth surface, the palpebral is slighty concave in its caudal two thirds. In its rostral third, the palpebral forms an oval articular surface on the internal side that probably was positioned in the depression of the rostral orbital margin.

Frontal. In DFMMh/FV 200, only the rostral and interorbital part as well as the caudalmost part of the frontal are preserved (Fig 4A). The frontal contributes both to the interorbital bone and the rostral part of the cranial table. From its rostral, wedge-like process, the bone widens moderately in caudal direction to reach twice its rostral width at the orbit. The frontal maintains its width between the orbits, being roughly as wide as the nasals, and widens continuously on the skull roof (Figs 4A, 4C and 7A). From the direct contact between postorbital and parietal here it is visible that the frontal is mostly excluded from the supratemporal foramen (Fig 4A), and the serrated frontoparietal suture lies at the rostral end of the supratemporal foramen. The frontal bone is complete in DFMMh/FV 605 (Fig 5A). The frontal contacts contacts the postorbital laterally at the skull roof. The rostral, midorbital part of the frontal is somehow inflated in comparison with DFMMh/FV 200. The medial frontal wedge is more acute and more narrow than in DFMMh/FV 200 (Fig 7). Caudally, the suture to the parietal is jagged and rostrally convex, so that the caudal margin of the frontal becomes deeply concave. The frontoparietal contact is positioned in the rostral fourth of the length of the supratemporal foramen. In DFMMh/FV 605, the frontal bears a median blunt ridge that denotes the median suture of the once unfused frontals. The caudal third of the frontal is vaulted medially and slightly depressed laterally. In ventral aspect (Fig 5B), the orbital margin of the frontal is recurved, so that the ventral surface of the frontal forms a shallow trough. Caudal to the orbit, the frontal forms a lateral projection, which is unsculptured and slightly depressed to enter the supratemporal fossa. PPT PowerPoint slide

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larger image TIFF original image Download: Fig 7. Reconstructions of the skull and mandible of Knoetschkesuchus langenbergensis gen. nov. sp. nov. Reconstruction of larger skull based on specimen DFMMh/FV 200, missing information supplemented with information from skull DFMMh/FV 605. (A) Dorsal aspect. (B) Left lateral aspect with mandible. Reconstruction of juvenile specimen DFMMh/FV 605, based on skull morphology and 3D data obtained in MeshLab. (C) Dorsal aspect. (D) Ventral aspect. For anatomical abbreviations, see text. Not to scale. https://doi.org/10.1371/journal.pone.0160617.g007

Parietal. The parietal is roughly rounded rectangular in outline, but its width slightly increases caudally (Fig 4A). The lateral parietal margin forms in its cranial half the medial margin of the supratemporal foramen, and in its caudal half is bounded by the squamosal so that it does not contribute to the caudal margin of the supratemporal foramen. The parietosquamosal suture is longitudinally straight. In DFMMh/ 200, the caudal margin of the parietal is medially slightly notched and forms the medial third of the caudal margin of the cranial table, excluding the supraoccipital from the latter (Fig 4A). In DFMMh/FV 605, the caudal margin bears a deep incision that exposes the supraoccipital dorsally (Fig 5A). The parietal is incompletely fused and bears in its caudal two thirds a thin median longitudinal suture, but its dorsal surface is even (Fig 5A).

Squamosal. The squamosal is approximately four times wider caudally than it is rostrally (Figs 4A and 5C). Rostrolaterally, the squamosal contacts the postorbital in the rostral third of the length of the supratemporal foramen, where it overlaps the postorbital laterally in its rostral extent. Its lateral margin is convex. In its medial third, the lateral squamosal margin is beveled to form an unsculptured lateral bordure set off from the cranial table by a marginal crest. The unsculptured beveled lateral area in DFMMh/FV 200 is small and extends from the caudolateral third of the dorsal squamosal area to the caudal squamosal corner (Fig 4A and 4B). The beveled portion is similarly long in DFMMh/FV 605 as in DFMMh/FV 200, but deeper, hanging into the infratemporal foramen (Fig 5C and 5D). The caudal margin of the squamosal is medially concave, but drawn out into a caudolaterally directed lobe at its lateral corner. This lobe is one fourth longer and more narrow in DFMMh/FV 605 (Fig 5A) than in DFMMh/FV 200 (Fig 4A). Similar to the beveled lateral margin, the caudolateral process of the squamosal is unsculptured and abated from the cranial table. The dorsal margin is straight in occipital aspect and the ventral contact of the squamosal to the exoccipital is visible in parts. Contact areas to the quadrate are in both specimens either destroyed or obscured.

Postorbital. Details of postorbital anatomy are visibly mostly in DFMMh/FV 605 (Fig 5A). The postorbital lies dorsal and medial to the jugal. In dorsal aspect, the postorbital divides into a medially directed part contacting the frontal, and a caudally directed part that contacts the squamosal, both having an orientation in a wide angle of approximately 130° to each other (Fig 5A). The caudally directed part of the postorbital is broader in DFMMh/FV 200 than in DFMMh/FV 605 and sculptured (Fig 4A and 4B), thus forming a broad dorsal surface between the orbit and the supratemporal fossa. In contrast, the postorbital bar between orbit and supratemporal fossa is very narrow in DFMMh/FV 605 (Fig 5A), being only half as wide as in DFMMh/FV 200. The junction between these two parts forms a gentle curve in the rostrolateral corner of the cranial table. Laterally on the corner is a slightly ventrally tilted and medially depressed area from which a constricted and smooth process descends and unites at mid-height of the postorbital pillar with an ascending process of the jugal (Figs 4B, 5A and 5C). Together, the processes of the jugal and the postorbital form the thin, pillarlike postorbital bar. The postorbital part of this bar is a laterally directed crest, and contains at its dorsal end a small vascular foramen (Fig 5C and 5D). In medial aspect, the postorbital medial margin, which forms the rostrolateral wall of the supratemporal fenestra, is recurved ventrally and does not contribute to the inner wall of the supratemporal fossa.

Jugal. The jugal is a rostrocaudally elongate bone that contributes both to the orbit and the infratemporal fenestra (Figs 4B, 5C and 5D). At mid-length, it forms a rod shaped caudodorsally ascending jugal process that constitutes the ventral half of the postorbital bar. This process is displaced medially from the lateral surface of the jugal and separated from the latter by a ridge. The dorsal margin of the jugal is convex at the rostral end of the postorbital bar, and rostrally and caudally to it weakly concave. The jugal body is rostrally to the postorbital bar only slightly dorsoventrally higher than caudally, where it forms a slender rodlike process (Fig 5A). The most rostral part of the jugal becomes very slender and wedges out between the underlying maxilla and the caudoventral process of the lacrimal (Fig 5C and 5D).

Quadratojugal. The quadratojugal is preserved only in DFMMh/FV 200 (Fig 4B). In lateral aspect, the quadratojugal is an elongated, rectangular bone that extends from rostromedially to caudolaterally. Medially, it contacts rostrally the squamosal with a narrow process, and caudally with a straight and tight suture the medially positioned quadrate. The quadratojugal forms the caudolateral corner of the infratemporal fenestra (Fig 7A). Lateroventrally, the quadratojugal attaches to the jugal, and forms together with the quadrate the caudolateral corner of the skull.

Quadrate. In DFMMh/FV 200, a strip of the left quadrate is visible laterally, underlying the squamosal and being laterally in contact with the quadratojugal (Fig 4A). In DFMMh/FV 605, the articular condyle of the left quadrate is visible on the specimen directly, but the lateralmost extent is obscured by sediment. μCT data of DFMMh/FV 605 depict both quadrates, with the right quadrate being completely preserved and the left one being fragmentary and lacking its condyle (Figs 5B and 6E). In occipital aspect, the quadrate condyle, which is entirely formed by the quadrate itself, possesses a kidney-shaped outline from which a rounded prong ascends dorsally. There is no good separation into a medial and a lateral hemicondyle and no intercondylar groove is visible. The ventral margin of the condyle is concave, and the medial part of the condyle is enlarged in comparison with the lateral part (Figs 5B and 6B). In dorsal aspect, the quadrate is elongate and rounded rectangular in shape. It is divided into a large dorsolateral part and a medially inclined medial part that is half the size of the lateral part, both separated from each other by a rounded longitudinal bulging crest (Fig 6E). The dorsolateral part ends laterally with a serrated margin that forms a suture to the quadratojugal. The dorsolateral surface is caudally flat, but medially depressed in its rostral half. In the center of the rostral half lies a large, rostrocaudally rounded oval shaped otic foramen. The open (i.e., unroofed) cranioquadrate canal is visible in dorsal view, extending from the dorsal margin of the medial quadrate condyle rostrolaterally (Fig 6E). Squamosal and exoccipital do not contribute to the cranioquadrate canal. Medial to the cranioquadrate canal, the surface of the quadrate bends ventromedially. The medial margin curves from the quadrate condyle in medial direction and contacts the exoccipital with a serrated, straight medially directed suture. The caudal edge of the quadrate is narrow and strongly concave dorsal and lateral to the otoccipital contact. Dorsal to this curved margin, the quadrate is roofed by a crest that overhangs the foramen vagii (Fig 6A3 and 6B). The foramen leads into a canal in rostral direction. Rostrodorsally to the crest, the ventromedially directed part of the quadrate bears another large and rounded oval foramen (Fig 6A3 and 6B). This foramen opens into a larger bipartite passage for the carotid artery and the cranial nerves IX–XI. The quadrate contacts the pterygoid ventrally, and the prootic and the laterosphenoid of the braincase rostrodorsally. These bones, however, are not preserved in articulation so that the contact cannot be determined more precisely. The ventral quadrate surface bears a well developed and high crest B [52], that extends from the lateral part of the quadrate condyle rostromedially, and a more rounded crest A, positioned relatively central at the quadrate (Fig 6E).

Pterygoid. The pterygoid is well preserved in DFMMh/FV 605, where it is exposed in ventral aspect on the ventral face of the skull (Figs 5B, 6C and 6D). The pterygoid wings are well developed and straight laterally directed. The pterygoid wings make the bone twice as wide as it is long. The pterygoid wings possess in ventral view a slightly concave rostral and a slightly convex caudal margin. The rather straight lateral margin extends obliquely from craniomedially to caudolaterally. A distinct pterygoid flange is visible as a rugose and thickened area at the margin of the pterygoid wing (Fig 6C and 6D), rostral to which the pterygoid wing is laterally depressed. The pterygoid body is slightly depressed on its ventral face, but it bears a faint median ridge. The pterygoid forms a median process that tapers rostrally. Left and right to the median ridge, a small, distinct longitudinally oval depression is developed that continues rostrally on each side of the narrow rostral process like a furrow (choanal groove) (Fig 6C). No distinct contact to the rostrally adjacent palatines is visible. Caudally, the pterygoid is in contact with the basisphenoid, which itself is only preserved in small bone fragments. The dorsal part of the pterygoid extends dorsally to contact the laterosphenoid and form the ventrolateral edge of the trigeminal foramen (Fig 6F). The suture to the quadrate and the laterosphenoid is clearly visible (Fig 6F).

Ectopterygoid. The only preserved left ectopterygoid of DFMMh/FV 605 is visible in the μCT reconstruction (Fig 5F), but preserved slightly disarticulated. The ectopterygoid has a constricted and slightly twisted body with a nearly straight rostromedial margin that forms the boundary of the suborbital fenestra, and a strongly concave caudolateral margin. The rostrolateral margin is slightly concave and rough, and attaches to the maxilla and the jugal. Because of the isolated position, the length of this contact and the contact to the maxilla cannot be determined, but the size of the ectopterygoid in relation to the skull size suggests that the ectopterygoid reached caudally at least to the dorsal process of the jugal. Caudally, the ectopterygoid is drawn out into a tongue-shaped and slightly striated and rugose medial process (Fig 5F). This process is attached to the rostrolateral margin of the pterygoid wing (Fig 7D).

Supraoccipital. The supraoccipital is subtrapezoidal in outline. On the occiput, it is ventrally bounded by the exoccipital (Fig 6A). It is separated from the cranial table by the parietal in DFMMh/FV 200, however, in DFMMh/FV 605, the supraoccipital is dorsally expanded and forms the medial third of the caudal margin of the cranial table (Figs 5a, 6A and 7C). In occipital view, the supraoccipital bears a rounded median crest and laterally to that a circular depression.

Exoccipital. DFMMh/FV 200 bears only fragments of the exoccipital, but this element is better preserved in DFMMh/FV 605 and could be depicted in the 3D reconstruction (Figs 5B and 6A). Left and right exoccipital are separated from each other in DFMMh/FV 605, and the paroccipital process is preserved only partially. The exoccipital bears a bone texture of weak grooves and pits, which is either diagenetic or a sign of poor ossification due to the ontogenetically young age of DFMMh/FV 605. The lateral half of the dorsal margin of the exoccipital is bounded by the squamosal. Medially, the exoccipital contacts the supraoccipital. The exoccipital forms the dorsal, lateral and lateroventral margins of the foramen magnum and excludes the supraoccipital from the latter. The ventral contact to the basioccipital is a broad and straight suture (Fig 6A). Lateroventrally to the foramen magnum, the exoccipital bears three circular foramina. The largest foramen lies at the exoccipital level to the dorsal margin of the foramen magnum and is interpreted as foramen for cranial nerve X and XI (foramen vagi) (Fig 6A and 6B). The foramen vagi is enlarged and internally bipartite to create a separate passage of cranial nerve IX medial to cranial nerves X and XI. A small foramen dorsomedial to the foramen vagi probably represents the exit of cranial nerve XII, whereas another, circular foramen ventral to the foramen vagi is interpreted as foramen caroticum posterior (Fig 6B).

Basioccipital and basisphenoid. The basioccipital and basisphenoid are preserved in DFMMh/FV 605, where they have been segmented from the 3D data (Fig 6A and 6B). Both are preserved adjacent to each other, but not in original articulation. The basioccipital is preserved with the occipital condyle, which is rounded trapezoidal in caudal aspect and slightly wider than high. Ventrally to the condyle, the basioccipital expands and the occipital surface bears in its ventral half a median crest. The ventral margin of the basioccipital bears a deep median indentation that represents the dorsal half of the median Eustachian foramen (Fig 6B). The left and right margins of the basioccipital are thick and each bears in its ventral third a large, oval foramen that is interpreted here as the lateral Eustachian foramen (Fig 6B). In rostral aspect, the surface of the basioccipital is medially slightly depressed and bears a pair of rounded depressions ventrally (Fig 6E). The basisphenoid is preserved isolated and segmented with its nearly complete body (Fig 6B), but with a very irregular and incomplete lateral surface. Its occipitoventral part, which lies ventrally adjacent to the basioccipital and is exposed on the occipital surface of the skull, forms left and right a thickened flange with a median incision that together form the ventral half of the median Eustachian foramen (Fig 6B). The ventral part of the basisphenoid is attached to the pterygoid and excluded from the ventral surface of the skull. Thus, the Eustachian tube is entirely enclosed between basioccipital and basisphenoid (Fig 6B). The basisphenoid rostrum is hatchet-shaped, i.e. dorsoventrally expanded and with a slightly convex rostral margin (Fig 6F). In rostral view, the hypophyseal fossa is exposed caudodorsally to the basisphenoid rostrum (Fig 6E). The caudodorsal wall of this fossa, the dorsum sellae (which floors the brain cavity rostrally) is preserved as well, and perforated by two medial, circular anterior carotic foramina (Fig 6E). Rostrolaterally to the anterior carotic foramina, the left and right foramen for the cranial nerve VI are visible (Fig 6E).