Campinasuchus dinizi, Carvalho, Ismar De Souza, Teixeira, Vicente De Paula Antunes, Ferraz, Mara Lúcia Da Fonseca, Ribeiro, Luiz Carlos Borges, Martinelli, Agustín Guillermo & Neto, Francisco Macedo, 2011

Carvalho, Ismar De Souza, Teixeira, Vicente De Paula Antunes, Ferraz, Mara Lúcia Da Fonseca, Ribeiro, Luiz Carlos Borges, Martinelli, Agustín Guillermo & Neto, Francisco Macedo, 2011, Campinasuchus dinizi gen. et sp. nov., a new Late Cretaceous baurusuchid (Crocodyliformes) from the Bauru Basin, Brazil, Zootaxa 2871, pp. 19-42 : 24-36

Campinasuchus dinizi sp. nov.

Holotype: CPP 1235 (Centro de Pesquisas Paleontológicas L. I. Price, Peirópolis – Uberaba, Minas Gerais, Brazil), a well preserved posterior skull and partial rostrum (Plates 1, 2).

Horizon and locality: The specimen was collected at Três Antas Farm (19°30’47”S, 50°06’20”W), Honorópolis District, Campina Verde County, Minas Gerais State, Brazil from the Turonian-Santonian sediments of the Adamantina Formation, Bauru Basin.

Derivatio nominis: The specific name honors Izonel Queiroz Diniz Neto and the families Diniz and Martins Queiroz, owners of the Três Antas Farm, where the fossil was excavated.

Paratypes: CPP 1234, partial skull with occluded mandible missing posterior portion of the skull (Plates 3, 4). CPP 1236, nearly complete rostrum (Plates 5, 6). CPP 1237, partial skull and mandible and associated postcranial skeleton (Plates 7, 8).

Horizon and locality: The paratypes were collected at the same locality and stratigraphic level as the holotype.

Diagnosis: Baurusuchid crocodyliform characterized by the following combination of features (autapomorphies marked with an asterisk): a short, low, laterally compressed rostrum; cranial table higher than dorsal border of rostrum; four premaxillary and five maxillary teeth; marked heterodonty, with third maxillary and fourth dentary teeth extremely enlarged relative to other teeth*; last maxillary tooth placed almost at the level of anterior border of palatal (suborbital) fenestra; posteroventrally projecting quadrate; pit on the premaxilla for reception of first mandibular tooth placed lateral to first premaxillary tooth (or between first and second premaxillary teeth); marked constriction of the skull posterior to last maxillary tooth; ten dentary teeth; large anteroposterior depression on each palatine between palatal fenestrae*; ventrally flat ectopterygoid surface; anteriorly semi-circular maxilla-jugal suture; slender posterior process of jugal; dorsal nasal-maxillary suture strongly laterally concave; nasal-frontal contact reduced; ventral depression on splenial at mandibular symphysis; anteriorly convex dentary-splenial suture at mandibular symphysis in ventral view.

Description

Skull. In comparison with other baurusuchids, Campinasuchus dinizi is notable for its much shorter and lower snout. The holotype (CPP 1235, Plates 1, 2) consists of an incomplete skull missing the anterior extremity of the snout. Due to the weakly downturned rostrum the cranial table is higher in relation to the dorsal border of the snout (CPP 1234, Plates 3, 4). The skull lacks an antorbital fenestra (preorbital fenestra). The orbits are circular and laterally directed. The supratemporal fenestrae are medium-sized, elliptical, and smaller than the orbit. The infratemporal fenestrae are triangular and separated from the orbits by flattened, inset postorbital bars. In comparison with other baurusuchids, the dentition is markedly heterodont in size. The jaws contain with four premaxillary, five maxillary (although there is a possible sixth tooth in the specimen CPP 1236) and ten dentary teeth. The skull surface is ornamented with grooves and ridges.

The premaxillae are sub-rectangular elements in dorsal view, dorsally separated from each other by the nasals and vertically disposed. The external nares are located at the anterior-most extremity of the rostrum, medially divided by a thin bar (specimen CPP 1237, Plates 7, 8). In specimens CPP 1234 and CPP 1236, the area of the external nares are partially broken and presented as a single large opening. The external nares are bordered ventrally and laterally by the premaxillae and dorsally by the nasals. Each premaxilla has four conical teeth which are regularly spaced. The first premaxillary tooth is positioned in the anteriormost portion of the rostrum. It is followed by a second tooth of almost equal size. The third tooth is the largest and is rounded in cross section. Carinae and serrations on premaxillary teeth are absent. The fourth and last premaxillary tooth is the smallest of this series, and is labio-lingually elliptical in cross-section. An occlusal pit on the premaxilla for the first dentary tooth is located lateral to first premaxillary tooth (between the first and second premaxillary teeth), rather than posterior to the first tooth as in other baurusuchids. This is concordant with laterally divergent first premaxillary teeth.

The maxilla is sub-rectangular in shape in lateral view, contacting the premaxilla anteriorly within a partially enclosed notch for reception of the large fourth dentary tooth. The dorsal border contacts the nasal along its entire length, posteriorly contacting the lacrimal, jugal, and prefrontal (Plates 4, 5, 6). The maxilla-jugal suture is anteriorly convex. The surface of the maxilla is ornamented by small ridges and grooves. The maxillary dentition consists of five conical teeth (a possible alveolus for a sixth tooth is present in CPP 1236). All of the teeth are located in the anterior portion of the maxilla, separated by short diastemata. The first three teeth increase in size posteriorly. The first tooth is the smallest of this series, located along the margin of the notch at the premaxilla-maxilla contact. The second tooth is moderately compressed and possesses finely serrated carinae on the mesial and distal edges. The third maxillary tooth is the largest of the series, with serrated carinae. The last two teeth are also compressed mediolaterally with finely serrated carinae. The fourth tooth is the second largest of this series, and the fifth is almost the same size as the second maxillary tooth. The last maxillary tooth is located posteriorly at almost the level of the anterior margin of the palatal (suborbital) fenestrae. There is a marked constriction in the snout posterior to the last maxillary tooth. In CPP 1237, there is evidence of a rounded antorbital fenestra bordered anteriorly by the maxilla and posteriorly by the lacrimal. In the other specimens, this area is badly preserved.

The nasals are long and reach the narial border. They contact the premaxillae in the anteriormost portion of the rostrum, extending as a thin bar anteroventrally to separate the dorsal portion of the external nares. The preserved portion of the rostrum in CPP 1236 (Plates 5, 6) shows that the nasal contacts the premaxillae, maxillae, prefrontals, and frontals but there is no contact with the lacrimal. The nasals maintain a constant width along most of their length, abruptly narrowing at the anterior of the rostrum. Here, they participate in the internarial bar as a thin nasal lamina together with an upward projection of the premaxilla (Plates 7, 8). Posteriorly the nasals meet the prefrontal and frontal. The contact with the frontal is reduced. Dorsally, the nasal-maxillary suture is more laterally concave than in other baurusuchids.

The lacrimal is sub-rectangular in lateral view, contacting anteriorly the maxilla, ventrally the jugal, dorsally the prefrontal, and posteriorly forming the anterior border of the orbit. The lacrimals are oriented almost vertically. Although in CPP 1235 the lacrimals are badly preserved and sutures with other bones are difficult to recognize, on the left element there is a posteriorly opening foramen interpreted as the naso-lacrimal duct, located close to the suture with the prefrontal descending process.

The jugal contacts the maxilla anteriorly, the lacrimal dorsally, the quadratojugal posteriorly, and the postorbital along the postorbital bar. The lateral surface of the horizontal ramus of the jugal is ornamented with irregular furrows. The anterior suture with the maxilla is convex, and at this portion the jugal exhibits its highest point. The ventral margin of the orbit is delimited by a relatively straight border of the jugal. The ascending process, contributing to the postorbital bar, arises from the medial surface of the jugal. It is thin, straight, slightly posterodorsally inclined, and lacks sculpturing. The posterior process of the jugal forms a slender bar contacting the quadratojugal through an interdigited suture. It forms the ventral border of the infratemporal fenestra.

PLATE 1. Holotype skull and mandibles of Campinasuchus dinizi gen. nov. et sp. nov. (CPP 1235). 1, dorsal view; 2, palatal view; 3, left lateral view; and 4, occipital view.

PLATE 2. Schematic drawings of the holotype skull and mandibles of Campinasuchus dinizi gen. nov. et sp. nov. (CPP 1235). 1, dorsal view; 2, palatal view; 3, left lateral view; and 4, occipital view. Grey indicates broken surfaces and regular dotted grey indicates matrix.

The prefrontal contacts the nasal, frontal and lacrimal. Each prefrontal is medially expanded, but they do not meet at the midline. The prefrontal is rectangular in shape, anteroposteriorly elongated, and elevated relative to the nasal and frontal. In CPP 1235, preserved on the left side is a portion of the descending process of the prefrontal, forming the anterior wall of the orbital cavity.

PLATE 3. Paratype of Campinasuchus dinizi gen. nov. et sp. nov. (CPP 1234). 1, dorsal view; 2, palatal view; and 3, left lateral view of the partial skull and mandible.

PLATE 4. Schematic drawings of the paratype of Campinasuchus dinizi gen. nov. et sp. nov. (CPP 1234). 1, dorsal view; 2, palatal view; and 3, left lateral view of the partial skull and mandible. Grey indicates broken surfaces and regular dotted grey indicates matrix.

PLATE 5. Specimen CPP 1236 of Campinasuchus dinizi gen. nov. et sp. nov. 1, dorsal view; 2, palatal view; and 3, right lateral view of the partial skull.

PLATE 6. Schematic drawings of specimen CPP 1236 of Campinasuchus dinizi gen. nov. et sp. nov. 1, dorsal view; 2, palatal view; and 3, right lateral view of the partial skull. Grey indicates broken surfaces and regular dotted grey indicates matrix.

PLATE 7. Specimen CPP 1237 of Campinasuchus dinizi gen. nov. et sp. nov. 1, left lateral view; 2, detail of the anterior portion of the rostrum, presenting the external nares; and 3, detail of bony septum that divides the external nares.

PLATE 8. Schematic drawings of specimen CPP 1237 of Campinasuchus dinizi gen. nov. et sp. nov. 1, left lateral view; 2, detail of the anterior portion of the rostrum, presenting the external nares; and 3, detail of bony septum that divides the external nares. Grey indicates broken surfaces and regular dotted grey indicates matrix.

PLATE 9. Reconstruction of the Campinasuchus dinizi skull in lateral view. 1, osteology and 2, life restoration in digital sculpture (art by Rodolfo Nogueira).

The frontals are fused forming a quadrangular bone bordered laterally by the prefrontal, anteriorly by the nasal, posteriorly by the parietal, and posterolaterally by the postorbital. The dorsal surface of the frontals is concave with a sharp and elevated medial crest running axially. Contact with the nasals is extremely reduced by the medial expansion of the prefrontal. The frontal contacts the prefrontals along a relatively straight suture. The frontal is higher in relation to the posterior border of the prefrontals. Based on CPP 1237, the frontal contributes slightly to the supratemporal fossa. In CPP 1235, it is difficult to observe this trait because sutures are not well preserved.

The parietals are fused and contact the frontals anteriorly, the supraoccipital posteriorly, and the squamosal posterolaterally. It is a very narrow triradiate bone that borders the medial and posterior margins of the supratemporal fenestrae. The dorsal surface of the parietal is higher than the frontal. Between the supratemporal fenestrae, the parietal forms a narrow, raised ridge. The supratemporal fenestra is smaller than the orbit; the medial margin formed by the parietal is convex, while it is straight along the lateral border. They extend beyond the limits of the infratemporal fenestra, nearly reaching the posterior border of the skull.

The postorbital is a robust bone that dorsally contacts the frontal, squamosal and parietal, and ventrally contacts the jugal and quadratojugal. Posteromedially, the postorbital forms the curved border of the supratemporal fenestra, meeting the squamosal along a broad straight suture. Dorsally, the postorbital is heavily ornamented. The anterior descending process of the postorbital forms a prominent crest decreasing ventrally that forms the posterodorsal edge of the orbits. At its contact with the jugal, it is circular in cross-section. The posterior descending process is smaller and laminar, and contacts the quadratojugal through a dorsoventrally oriented suture located immediately posterior to the dorsal corner of the infraorbital fenestra. In CPP 1235, the postorbital has an anteriorly oriented depression on its anterolateral border, above the anterior descending process, that possibly corresponds to the facet for a palpebral bone.

In dorsal view, the squamosal is V-shaped, with its point forming the posterolateral corner of the cranial table. Anteriorly, it contacts the postorbital, medially the parietal and supraoccipital, but these latter sutures are not clearly observed in the holotype CPP 1236. In dorsal view, the squamosal forms the posterior and lateral borders of the supratemporal fenestra and, in lateral view, it limits dorsally and posteriorly the otic recess. The ventrolateralprocess of the squamosal descends posteroventrally to contacts the quadrate through an almost vertical suture, located immediately posterior to the incisura otica. In posterior view, the suture between squamosal and exoccipital is partially observed in the left paraoccipital process of CPP 1235. In this specimen, the process of the squamosal descends to reach the level of the occipital condyle. The angle between the plane of the skull roof (squamosal) and the quadrate is 60°.

The quadratojugal is a dorsoventrally elongate element. It contacts anteriorly the jugal, anterodorsally the postorbital, posteriorly the quadrate, and probably posterodorsally the squamosal. The suture with the jugal is interdigited, almost vertical and positioned close to the posteroventral corner of the infratemporal fenestra. The suture with the quadrate is almost straight running in posteroventral-to-anterodorsal direction. Near the ventral border of the skull, this suture is strongly interdigitate process delimiting the post. The ascending process delimiting the posterior border of the triangular-shaped infratemporal fenestra is constricted in its middle region, at the level of lower edge of the incisura otica.

The quadrate is posteroventrally inclined 45º relative to the skull roof. It contacts anteriorly the quadratojugal, dorsally the squamosal, and posteriorly the exoccipital. The pterygoid process of the quadrate is robust and well developed; however, at present the contacts with basisphenoid and pterygoid could not be observed clearly. The contact with the exoccipital is partially visible in ventral view. The lateral surface of the quadrate has a shallow depression for muscle attachment located posterior to the suture with the quadratojugal and below the otic recess. Dorsally, the otic recess of the quadrate is highly fenestrated. The condylar surface is rounded and faces posteroventrally, the medial condyle more ventrally projected than the lateral one. In the posterior view, the quadrate has an oval, laterally opened foramen.

The supraoccipital is a triangular-shaped bone that contacts the parietal, squamosals and exoccipitals; however the sutures among these elements are not clear. It is exposed on the cranial roof, separating the parietal from the posterior margin of the skull. The contribution of the supraoccipital to the occipital wall is unknown because of the poorly preserved sutures among elements in the available specimens.

The exoccipitals meet medially, dorsal to the foramen magnum. They extend laterally into the paroccipital processes, which contact the quadrates and squamosals. Unfortunately, sutures in this region are unclear.

The basioccipital comprises the small, rounded occipital condyle and forms a narrow tuberosity that extends laterally. It forms the ventral border of the foramen magnum and is inclined, facing posteroventrally.

The basisphenoid is partially preserved in CPP 1235. On the left side of this specimen, there is a small, circular foramen, interpreted as the lateral Eustachian foramen, located on the suture between the basisphenoid and basioccipital.

The pterygoids are partially preserved. They meet to form a large plate behind the internal nares and expand laterally to form flattened laminar lateral pterygoid flanges. Here they meet the ectopterygoid along their lateral border. The posterior projection of the pterygoids is badly preserved in CPP 1235 (not available in CPP 1237 at present) precluding any information about its contact with the basicranial portion.

The ectopterygoids contact the medial surface of the jugals along a broad suture. They extend ventrally to contact the pterygoid flanges and anteromedially to contact the palatines, forming the lateral borders of the secondary choanae. The palatal surface of the ectopterygoids is flat and laminar, in contrast to the ventrally concave ectopterygoids of other baurusuchids.

The palatines are triangular and contact the maxilla anteriorly. They border two elongated suborbital fenestrae positioned anteriorly. A large anteroposteriorly directed depression is present on each palatine between the mid line and the suborbital fenestra. In CPP 1234 and CPP 1236, these depressions end in a oval foramen, located immediately anterior to the transverse palatine-maxillar suture.

Mandible. The mandible is partially preserved and still in articulation with the skull in the holotype (CPP 1235), CPP 1234, and CPP 1237. In general morphology, it is sub-triangular in lateral view, becoming shallower anteriorly. The splenials participate in the mandibular symphysis. A transverse depression on the ventral surface of the splenials is present at the symphysis, posterior to the dentary-splenial suture. In ventral view, the dentary-splenial suture is anteriorly convex within the symphysis. In lateral view, the mandibular outline varies in its height along its length. There is a slight elevation of the dorsal margin dorsal to the mandibular fenestra. The external surface of the mandible is sculptured the same manner as the skull.

The dentary forms the majority of the mandibular length and contains ten teeth. Anteriorly, the dentary is overhung by the premaxilla, the first tooth creating an occlusal pit between the first and second premaxillary teeth. The fourth dentary tooth is extremely enlarged in comparison with the other teeth and fits into a partially enclosed notch in the rostrum at the premaxilla-maxilla contact. This tooth has a rounded transverse section and possesses serrated carinae on the mesial and distal edges. Posteriorly, the dentary extends as far as the mandibular fenestra, forming the anterodorsal edge of the fenestra. The dentary does not extend beneath the fenestra. The fused dentary symphysis is long and extends posteriorly as far as the level of the sixth dentary tooth. The splenials contribute extensively to the symphysis, meeting the dentary along an anteriorly convex suture. The posterior margin of the mandibular symphysis is at the level of the ninth dentary tooth. Posteriorly the splenials border the anterior margins of the mandibular fenestrae.

The angular contacts the dentary anteriorly and posteriorly meets the surangular and articular. It delimits the ventral margin of the mandibular fenestra. This fenestra is large, with its main portion located posterior to the orbit, roughly at the the level as the infratemporal fenestra. The angular is elongated with the dorsal and ventral borders nearly parallel to the jaw margins.

The surangular is relatively straight. It borders the mandibular fenestra dorsally, contacting the dentary anteriorly and the angular posteroventrally. The suture with the angular is straight. The left articular of the holotype (specimen CPP 1235) is complete. The glenoid consists of two distinct fossae for articulation with the quadrate condyles. The lateral fossa is anteroposteriorly larger than the medial one, faces dorsally, and has a posterior sharp crest. The medial fossa is smaller and inclined to face dorsomedially. The retroarticular process is sub-triangular in dorsal view, and is directed posterolaterally.