Cricosaurus bambergensis, Sachs & Young & Abel & Mallison, 2019

Sachs, Sven, Young, Mark T., Abel, Pascal & Mallison, Heinrich, 2019, A new species of the metriorhynchid crocodylomorph Cricosaurus from the Upper Jurassic of southern Germany, Acta Palaeontologica Polonica 64 (2), pp. 343-356 : 345-351

Cricosaurus bambergensis sp. nov.

Figs. 1 , 3–7 .

ZooBank LCID: urn:lsid:zoobank.org:act:AAAD9169-1411-451C-BBB5-F069E938575F

Etymology: Named after the city of Bamberg, where the specimen is housed and that is the namesake of the Bamberg district, which encompasses the type locality at Wattendorf.

Holotype: NKMB-P-Watt14/274, almost complete skeleton ( Figs. 1 , 3–7 ).

Type locality: Kalk- und Dolomitbruch der Andreas Schorr GmbH, Wattendorf, Bamberg district, Bavaria, southern Germany ( Fig. 2 ).

Type horizon: Aulacostephanus pseudomutabilis Tethys Ammonite Zone, Wattendorf Member, Torleite Formation , late Kimmeridgian, Upper Jurassic ( Fig. 2 ).

Diagnosis.—A member of Cricosaurus with the following unique combination of characters (proposed autapomorphic characters are indicated by an asterisk): bicarinate dentition, lacking conspicuous enamel ornamentation; tooth crowns in the premaxilla, maxilla and dentary show distinct labiolingual compression (shared with C. suevicus and C. elegans ); the maxillary tooth row continues posteriorly past the anterior margin of the orbit (thalattosuchian symplesiomorphy); presence of pronounced reception pits for dentary tooth crowns on the lateral margins of the anterior and mid-portions of the maxilla; palatines have a distinct midline ridge with paired depressions on either side*; morphology of the tail displacement unit: the distal-most three preflexural vertebrae have neural spines that are oriented very strongly posteriorly, their posterior margin lies on top of the prezygapophyses of the adjacent vertebra; these neural spines appear almost rod-like in lateral view; the three vertebrae anterior to them have a similar morphology, but the neural spines look more like a “regular” neural spine, albeit strongly oriented posteriorly*.

Cricosaurus bambergensis retains the following four metriorhynchid tail fluke symplesiomorphies (unlike C. suevicus ): (i) the distal-most preflexural caudal vertebra has a rod-like hemapophysis; (ii) the proximal-most five or six flexural vertebrae have anteriorly oriented neural spines, but not strongly oriented anteriorly; (iii) the flexural hemapophyses contact one another along their anteriorposterior margins; and (iv) the distal-most postflexural hemapophysis return to a rod-like morphology.

Description.—Supplementary Online Material available at http://app.pan.pl/SOM/app64-Sachs_etal_SOM.pdf illustrates the specimen in detail and contains further information: SOM 1, a text file with information on 3D model and orthophoto generation, 3D file viewing information, and further information on the phylogenetic analysis; SOM 2, 3D models of the fossil slabs; SOM 3, a very high resolution orthophoto of the 3D models; SOM 4, *.emf files for bootstrap values and Bremer support values and nexus file.

General remarks on the skull: The cranium and mandible of Cricosaurus bambergensis are preserved in articulation and are exposed in ventral view ( Fig. 3 ). The skull is largely damaged, but part of the palate and the mandible are well-preserved and bear traceable sutures. Unidentifiable skull roof elements are preserved adjacent to the skull.

Premaxillae: The premaxillae are exposed in ventrolateral view ( Fig. 3 ). Their lateral sides are undulated and convex at the alveoli. The exposed ventral side is nearly flat and the premaxillae are separated posteroventrally by the pointed anteroventral portions of the conjoint maxillae. The premaxillary–maxillary suture is visible ventrally and terminates at the position of the third premaxillary tooth. The conjoint premaxillae form a rounded tip of the rostrum.

Maxillae: The maxillae are exposed in ventral and ventrolateral view ( Fig. 3 ). As at the premaxillae the alveolar edges are undulated, forming pronounced reception pits for dentary tooth crowns. The right maxilla bears 23 teeth. The exposed ventral surface shows that the conjoined maxillae form a pointed tip that separates the premaxillae posteroventrally. This tip extends to the level of the third premaxillary tooth. Posterolaterally a jugal contact is established. A ventral midline suture is clearly visible and the maxillae are slightly dorsally inclined throughout the ventral midline.

Jugal: Part of the strap-shaped jugal is preserved posterior to the maxilla on the right side of the cranium ( Fig. 3 ).

Palatines: The almost complete palatines are well preserved and exposed in ventral view ( Figs. 3 , 4B ). The anterior portion of the conjoined palatines is obscured by the mandibular rami, and the posterior part, where the palatines contact the pterygoids, is damaged. Interestingly, the conjoined palatines form a prominent ridge at the midline suture that flares anteriorly and demarcates two elongate depressions that are placed adjacent to the ridge ( Figs. 4B ).

Pterygoids: Damaged remnants of the pterygoids are present, but the poor preservation does not provide any information ( Fig. 3 ).

Sclerotic ring: Fragments from the sclerotic ring are preserved along with some unidentifiable skull elements near the posterior portion of the right maxilla ( Fig. 3 ).

Unidentifiable skull elements: A number of skull roof elements, most likely from the nasal–prefrontal–frontal complex and probably also from the postorbital and squamosal are placed dorsally in the posterior part of the skull ( Fig. 3 ), but they cannot be identified more precisely.

Dentaries: The dentaries are visible in ventral view, but no clear surangular suture can be traced ( Fig. 3 ). The straight ventral midline contact is well visible and forms more than 50% of the symphysis. The later continues in the conjoined splenials that separate the dentaries posteriorly. The surangulodentary groove starts in about the middle of the mandible and becomes more prominent posteriorly. The exact tooth count cannot be provided as some tooth positions are obscured.

Surangulars: The surangular cannot be separated from the dentary. The surangulodentary groove is visible in lateral view, on the posterior region of the ramus ( Fig. 3 ). The surangular forms the posterodorsal part of the mandible and is demarcated ventrally by the angular. Posteriorly the surangular forms part of the dorsal portion of the retroarticular process and, at the posterior end, contacts the articular.

Angulars: The elongate, strap-like angular is well visible and starts at about mid-length of the mandible and forms the posteroventral demarcation of the latter ( Fig. 3 ). It terminates at the posterior end of the retroarticular process of which it forms the ventral portion. The latter is broken off, displaying a bulged midline part. Anteriorly, a splenial contact is established on the medial side of each angular and a long dentary suture is formed laterally. Posterodorsally the angular contacts the articular.

Articular: Only a small portion of the articular is exposed posterodorsally at the retroarticular process ( Fig. 3 ).

Hyoids: Remnants of the hyoids are preserved adjacent to the atlas-axis ( Fig. 4C ). They are curved, strap-shaped elements, bearing a flaring, transversely flat posterior end.

Dentition: Each premaxilla bears three and the right maxilla 23 tooth positions. The number of dentary teeth is uncertain as some are obscured. All well preserved tooth crowns are slender, labiolingually compressed and have an elliptical cross-section ( Fig. 4A ). The enamel surface is smooth, but a faint carina with a low keel extends along the mesial and distal margins of each crown. Some smaller premaxillary and maxillary teeth are replacement teeth.

Atlas-axis vertebrae and ribs: An elongate element adjacent to the first post-axial cervical vertebra most likely represents part of the atlas-axis ( Fig. 4C ). The bone is exposed in ventral view, but the preservation is poor and it is partly obscured by a rib. It is thus not possible to determine whether the elongate portion represents the axis only or both elements conjoined. On the right side, adjacent to the elongate bone, there is a curved element that might represent the atlantal or axial rib.

Postaxial cervical vertebrae and ribs: An articulated series of five postaxial cervical vertebrae is preserved Figs. 4C , 5 ). The dimensions of the centra cannot be provided as they are largely obscured by matrix and bone fragments. The first and second postaxial cervicals are exposed in ventrolateral view ( Fig. 4C ). The posterior articulation surface of the first centrum is partly visible, indented and surrounded by a thickened rim. The dorsolaterally placed diapophysis can be seen in the first and second vertebrae SOM 3). It is transversely compressed and less prominent than the ventrolaterally placed parapophysis. The latter has an oval shape and the surface between each dia- and parapophysis is slightly indented. The cervical ribs are only fragmentary preserved.

Dorsal vertebrae and ribs: An articulated series of 18 dorsal vertebrae is present ( Fig. 5 , SOM 3). Most dorsals are visible in ventral view and are partly obscured by ribs. Only the posterior-most dorsals are exposed in lateral view. The centra are longer than wide/high and have concave ventral sides. Adjacent to the articular faces there are some longitudinal striations. In ventral view, the transverse processes are only slightly posteriorly inclined. Their oval diapophyses are dorsoventrally compressed. The parapophyses are only well preserved in the posterior-most dorsals. They are placed anteriorly on the transverse processes and are smaller than the diapophyses. The zygapophyses on the posterior dorsals exceed the margins of the centra longitudinally with about half of their length. The neural spines in these vertebrae are about as high as the corresponding centra and have slightly concave anterior and posterior edges and a convex dorsal side when seen in lateral view.

The dorsal ribs are preserved adjacent to the centra but the rib heads are largely obscured. The ribs are slender and slightly offset proximally. The distal portion of each rib is transversely compressed.

Gastralia: The disarticulated gastral basket is represented by some curved, strap-shaped elements ventral to the dorsal ribs ( Fig. 1 , SOM 3).

Sacral vertebrae and ribs: Two articulated sacral vertebrae are preserved and exposed in lateral view ( Fig. 1 , SOM 3). The centra are longer than high and show longitudinal striations adjacent to the articular faces. The ventral sides of the centra are concave, but they are largely obscured by the sacral ribs. The morphology of the neural arches and neural spines resembles that of the dorsal vertebrae. The sacral ribs are still attached to the centra. The first sacral rib is gently posteriorly inclined and flares distally. The second sacral rib is slightly larger and likewise flares distally. The distal portions of both ribs are obscured by the femur.

Caudal vertebrae and ribs: All caudal vertebrae are preserved in articulation, but the tail is interrupted after the 13th vertebra. The preserved portion incorporates 28 preflexural, six flexural and 20 postflexural caudal vertebrae ( Figs. 1 , 6 ; SOM 3). All caudals are preserved in lateral view and have concave ventral sides. The preflexural centra are longer than high but become gradually shorter posteriorly. The articular faces have slightly expanded lateral sides and are gently angled ventrally for the articulation with the hemapophyses. The sub-triangular transverse processes are preserved in the proximal-most caudals and are placed at about the dorsoventral midsection of the vertebrae. They are, however, broken off and pushed downwards, displaying their dorsal aspect. The zygapophyses are reduced in the proximal part of the tail. The proximal caudal hemaphophyses are strap-shaped and first occur between the third and fourth vertebrae. They become rapidly shorter and are missing in the distal-most preflexural caudals. The neural spines in the three proximal-most caudals resemble the morphology of the posterior dorsal and sacral neural spines. In the fourth caudal a prominent anterodorsal process is formed ( Fig. 1 ). The margin between this process and the remainder of the neural spine is excavated. The neural spines of the fifth and sixth preflexural caudals are obscured by the overlying right hindlimb. The anterodorsal process is placed more ventrally in the 7th–9th preflexural caudals, and the remaining neural spines are anteroposteriorly narrower and more posteriorly inclined, leading to a larger excavation between the two parts. The anterior process is also present in the first caudals behind the cut, but here it is reduced and more dorsally oriented. The inclination of the neural spines continues after the cut, but they become gradually lower, more lobate and posteriorly inclined in all of the preflexural vertebrae. In the proximal caudals the neural spines only barely exceed the level of the centra with their posterior portions.

In the post-cut caudals, in the mid-tail section, about 1/3 of neural spine length exceeds the level of each centrum whereas in the distal-most preflexural caudals about half of their length exceeds the centrum posteriorly. The neural spines are here also more posteriorly inclined. The last preflexural centrum is stout, compared with the other preflexural centra, and leaned anteriorly with a slightly higher and more ventrally protruding posterior articular face. In the first flexural centrum the anterior and posterior articular faces are both gently ventromedially inclined and the posterior face again reaches further ventrally than the anterior one. In the remaining caudals the anterior and posterior faces are not noticeably inclined and the posterior one always protrudes slightly more ventrally. The neural spine in the last preflexural caudal is only gently posteriorly inclined and more erected than that of the preceding vertebrae and its prezygapophysis faces anteriorly, whereas the neural spines in all flexural caudals are facing anteriorly ( Fig. 6 ). In the first flexural vertebra the neural spine meets the apex of the shorter preceding neural spine and here the prezygapophyses are likewise anteriorly oriented. The following neural spine is more elongate and the prezygapophysis faces dorsally. The neural spine of the third flexural caudal is about as long as that of the third one but broader, more anteriorly inclined and the prezygapophysis faces dorsally. The neural spines of the 4th–6th flexural caudals become rapidly shorter and the reduced prezygapophyses are facing anterodorsally. Postzygapophyses cannot be seen in any of these vertebrae. In the first and second postflexural caudal vertebrae the neural spines are very reduced and prominently posteriorly inclined, and only remnants of the prezygapophyses are present as small tips. In the remaining postflexural caudals the neural spines are reduced to low straps and no neural spines are present in the last seven vertebrae. The hemapophyses of the last preflexural caudal are formed as a rectangular bar that exceeds the preceding centrum completely. Here a short, posteroventrally inclined hemapophyseal dorsal process is formed. In the st–3rd flexural caudals the dorsal processes are longer and more posteriorly inclined and the ventral hemapophyseal parts are lobe-shaped. The same morphology continues in the 4th–6th flexural caudals but the hemapophyseal dorsal processes are less posteriorly inclined and the lobate part becomes smaller. Hemapophyses are visible to the 10th postflexural caudal but the shape changes from lobate to low-rectangular at the intersection between the flexural to the postflexural caudals. There are no hemapophyses visible in the distal-most caudals.

Scapulae: The scapulae are obscured by the coracoids Fig. 5 ) and can therefore not be described.

Coracoids: Both coracoids are preserved in ventral view Fig. 5 ). They are flat elements with concave anterior and posterior sides. The anterior edge is more strongly concave and almost semi-circular, whereas the posterior one is transversely wider. The mid-section of each coracoid is constricted. The proximal and distal coracoid portions are expanded and have convex edges. A small, circular, distally placed coracoid foramen is present.

Humerus: A fragment preserved adjacent to the right coracoid ( Fig. 5 ) might represent part of a humerus.

Radius and ulna: The right radius and ulna are preserved and overlap each other ( Fig. 5 ). They are flat, circular elements. It is uncertain which of these elements represents the radius and which the ulna.

Carpal elements: The carpal elements are preserved Fig. 5 ), but due to disarticulation an exact identification is not possible.

Metacarpal elements: The metacarpal elements are preserved in original arrangement ( Fig. 5 ). The first metacarpal is a crescent-shaped element that is the largest in the row. It has a strongly convex anterior side and a slightly concave posterior one. The second to fourth metacarpals are rod-shaped elements of about equal size. The fifth metacarpal is largely obscured by a rib.

Phalanges (forelimb): Several hourglass-shaped phalanges are preserved ( Fig. 5 ). They are still in original position showing that five digits with two phalanges each are formed. The proximal phalanges are clearly larger and more elongate than the distal ones. The anterior-most proximal phalanx is placed distal to the first metacarpal and is wider than the other phalanges of the forelimb. The distal phalanges have a sub-circular shape.

Ilium: The ilium is largely obscured, preventing a description (SOM 3).

Pubes: The pubes are complete, but the right pubis partly overlies the left one ( Fig. 7 ). They are gracile elements having fan-shaped distal portions with a convex distal edge. The anterior and posterior sides are concave, but the pubes are massively constricted at mid-length, having only about ¼ of the expansion of the distal end. The proximal head is only slightly wider than the midshaft in lateral view.

Ischia: The ischia are largely obscured or damaged (SOM 3). The dorsal portion of the right ischium is in original articulation with the femur that largely obscures it. A slightly convex edge is formed posterodorsally, whereas the anterior side is deeply concave from the dorsal acetabular end to the anteroventral portion of the ischium. The latter protrudes slightly more anteriorly than the acetabular head. The ventral side of the left ischium is almost flat.

Femora: The femora are elongate, sigmoidally curved elements ( Fig. 7 ). They are narrowest at about mid-length and lack a fourth trochanter. The proximal end of each femur is obscured by other bones. The distal ends articulating with the tibiae and fibulae are gently convex.

Tibiae: Both tibiae are preserved ( Fig. 7 ). They are stout, long-rectangular elements that are much wider than the fibulae. Proximally each tibia forms most of the contact with the femur. The anterior edges of the tibiae are straight, and the posterior ones are slightly concave. Their distal ends are slightly narrower than the proximal ones.

Fibulae: Both fibulae are preserved in original alignment with the tibiae ( Fig. 7 ). They are narrow, rod-shaped elements with a slightly constricted shaft due to concave anterior and posterior edges. The proximal and distal ends are slightly convex. Tibiae and fibulae are about equal in length.

Tarsal elements: The tarsal elements are sufficiently preserved in the right hindlimb ( Fig. 7 ). Astragalus and calcaneum are slightly displaced. The astragalus, adjacent to the fibula, is kidney-shaped and the largest tarsal element. The calcaneum which contacts the tibia has an oval shape and is slightly smaller than the astragalus. Distal tarsal 3 is placed proximal to the metatarsals 2 and 3 and is smaller than the posteriorly placed distal tarsal 4 that distally contacts the fourth metatarsal.

Metatarsal elements: The metatarsals are preserved in original alignment, along with the phalanges, in both limbs ( Fig. 7 ). The first metatarsal is the widest and shortest element in the row. It is placed slightly more proximally than the other metatarsals and contacts the distal tarsal 3 posteriorly. The proximal end of the first metatarsal is fan like expanded and more than twice as wide as the distal one. The first metatarsal terminates at the level of the distal fourth of the other metatarsal elements, but may be slightly displaced. The second metatarsal is slightly shorter than the third and fourth ones. All are rod-shaped elements with slightly expanded distal and ventral portions. The fifth metatarsal is reduced into a small triangular bone.

Phalanges (hindlimb): The phalanges are preserved in original alignment in the first to fourth digits of both limbs ( Fig. 7 ). The first digit consists of two phalanges, the proximal one being rod-shaped and placed half way between the second metatarsal and first phalanx of the second digit. The distal phalanx of the first digit is pointed and less than half as long as the corresponding proximal phalanx. The second digit has three phalanges. The proximal one is rod-shaped and slightly longer than the according one of the first digit. It is placed at level with the proximal phalanx of the third digit but is slightly shorter. The second phalanx of the second digit is about half as long as the proximal one, but likewise rod-shaped. The terminal phalanx of the second digit again is pointed and ends at level of the distal end of the second phalanx of the third digit. The third digit bears four phalanges, of which the first to third are rod shaped. The proximal one is the largest in the hindlimb. It terminates further distally than the corresponding phalanx of the second digit and so does the shorter third phalanx of the third digit. The fourth phalanx of the third digit is about 1/3 the length of the proximal one, whereas the pointed fourth phalanx is formed as a small tip only. The fourth digit is the longest and formed the trailing edge of the limb. It consists of five phalanges of which the first to third are rod-shaped. The proximal phalanx starts slightly distal to the according one of the third digit. It also terminates slightly further proximal to the later. The same applies to the second and third phalanx of the fourth digit. The short, rectangular fourth phalanx is placed half way between the third and fourth phalanges of the third digit. The pointed fifth phalanx of the fourth digit forms the distal-most part of the entire limb. Stratigraphic and geographic range.—Wattendorf Member, Torleite Formation, late Kimmeridgian, Wattendorf, Bavaria, southern Germany.

Figures

Fig. 1. Metriorhynchid thalattosuchian Cricosaurus bambergensis sp. nov., NKMB-P-Watt14/274, holotype, late Kimmeridgian of Wattendorf (southern Germany). Skeleton in ventrolateral view.

Fig. 3. Metriorhynchid thalattosuchian Cricosaurus bambergensis sp. nov. (NKMB-P-Watt14/274) holotype, late Kimmeridgian of Wattendorf (southern Germany). A1, skull in ventrolateral view; A2, illustrates the preserved elements which can be unambiguously identified (please note that the dentary-surangular contact cannot be traced and is based upon the position in C. suevicus).

Fig. 4. Metriorhynchid thalattosuchian Cricosaurus bambergensis sp. nov. (NKMB-P-Watt14/274) holotype, late Kimmeridgian of Wattendorf (southern Germany). A. Dentition. B. Palatines showing the midline keel seperating symmetrical depressions (dashed outline). C. First cervical vertebrae. Abbreviations: aac, atlas-axis vertebrae; cv, cervical vertebra; hy, hyoid.

Fig. 5. Metriorhynchid thalattosuchian Cricosaurus bambergensis sp. nov. (NKMB-P-Watt14/274) holotype, late Kimmeridgian of Wattendorf (southern Germany). Pectoral girdle and forelimb elements. Abbreviations: ca, carpal elements; co, coracoid; cv, cervical vertebra; dv, dorsal vertebra;?h, questionable humerus; mc, metacarpal elements; ph, phalanges; ru, radius and ulna; sc, scapula.

Fig. 6. Metriorhynchid thalattosuchian Cricosaurus bambergensis sp. nov. (NKMB-P-Watt14/274) holotype, late Kimmeridgian of Wattendorf (southern Germany). Distal part of the tail showing the flexural and postflexural region.

Fig. 7. Metriorhynchid thalattosuchian Cricosaurus bambergensis sp. nov. (NKMB-P-Watt14/274) holotype, late Kimmeridgian of Wattendorf (southern Germany). Hindlimb and pelvic girdle. Abbreviations: mt, metatarsals; ph, phalanges.

Fig. 2. A. Reduced stratigraphic table of the Kimmeridgian rock units of the northern Franconian Jurassic, based on Niebuhr and Pürner (2014). B, C. Maps showing the locality of NKMB-P-Watt14/274 at Wattendorf (asterisk) within the Bamberg district and its placement in Germany.