Pietraroiasuchus ormezzanoi, Buscalioni & Piras & Vullo & Signore & Barbera, 2011

Buscalioni, Angela D., Piras, Paolo, Vullo, Romain, Signore, Marco & Barbera, Carmela, 2011, Early eusuchia crocodylomorpha from the vertebrate-rich Plattenkalk of Pietraroia (Lower Albian, southern Apennines, Italy), Zoological Journal of the Linnean Society 163 (5), pp. 644-645 : 644-645

SPECIES PIETRAROIASUCHUS ORMEZZANOI SP. NOV. ( FIGS 1–4 )

Holotype: Specimen PC-1, an almost complete articulated skeleton exposed in ventral view.

Referred material: Specimen PC-2, an almost complete articulated skeleton exposed in dorsal aspect provisionally housed at the Museo di Paleontologia del Centro Museale dell’Università di Napoli Federico II University .

Locality and horizon: From the site known as ‘Civita di Pietraroia Cave’, locality of ‘Civita di Pietraroia’ (Mt Matese, southern Italy). Early Albian in age.

Etymology: The species ormezzanoi honours Daniele Ormezzano, curator of the Museo Regionale di Scienze Naturali di Torino, who diligently cleaned one of the specimens.

Diagnosis: Anterior shape of the dentary terminating roundly; sigmoid dentary tooth row series, with the 10th to 17th teeth inwardly directed; hypotrophy of first mandibular teeth; dentary bearing 17 alveoli; development of platform at the dentary and splenial contact; two glenoid areas in the retroarticular process (character unknown in P. trinquei ); surangular anterodorsal with a dorsal process and medially curved.

DESCRIPTION OF PIETRAROIASUCHUS ORMEZZANOI

GENERAL APPEARANCE

The skull has a rounded and wide premaxillary contour, and the maxillae have a straight, lateral contour although the skull widens laterally in front of the orbits. The dorsal surface of the maxillae seems to be mid-convex. The skull ornamentation is located on the skull table, jugals, and profusely in the osteoderms, contrasting with the rostral bones, which are smooth, with minimal sculpting of the maxillary bone. The skull table width is 52% of the maximum cranial width (between quadratojugals). Orbits are small, 17% of the skull length. The temporal fenestrae are oval with their major axis laterally directed. They are shorter than the orbits, and their antero-posterior length is about 37% of the skull table. The infratemporal fenestrae are triangular and reduced in size. The suborbital fenestrae are not fully exposed, although they are narrow and rather short. The choanal aperture is small, and as long as it is wide. It is located anteriorly and enclosed in the pterygoids, bordered anteriorly by palatines.

P. ormezzanoi is a small, pachyostotic crocodile, with a skull length 11–13% of the total body length. The tail length is longer than the presacral body length. This proportion is unique among eusuchian crocodiles, except for Susisuchus , whose proportion may be similar: it is not possible to be certain as the tail of the specimen is not fully preserved. Caiman is the living crocodilian with the longest tail (as long as the combined length of the skull and presacrum). The forelimb is more slender and shorter than the hindlimb and the humerus is 70% of the femoral length. The forelimb length (humerus and radius) is 76% that of the hindlimb (femur and fibula). The forelimb zeugopod is 50% of the length of the humerus. A ventral dermal skeleton was arranged in a collar and gastral shield. The nuchal shield is separated from the dorsal shield and is made up of six osteoderms. The dorsal dermal skeleton comprises the segmented paravertebral shield plus one accessory osteoderm.

SKULL

The premaxilla is broad and is 38% of the rostral length. It has a rounded contour following that of the maxilla, lacking a lateral notch. The premaxillomaxillary suture is caudally directed although the medial part of the suture is transverse and lacks a posterior medial projection. There is a single external naris, which faces dorsally. It is separated from the anterior contour by a wide premaxillary symphysis, and is rounded, being wider than it is long. There is no detail of the narial fossa. Nasals do not enter the naris and both are separated by premaxilla, which has five teeth, and whose alveoli are homogenously separated by wide interalveolar spaces. The alveolar diameter is small, all alveoli are subequal in size, and teeth are slender and conical ( Fig. 2A, B ). The ventral premaxillomaxillary suture is transverse (orthogonal to the sagittal axis). The foramen incisivum is not clearly preserved in the specimens although it could never constitute more than half the maximum width of the premaxillae.

The maxillae are dorsoventrally flattened, with a mid-convex surface. They have a minimum dermal sculpture that is otherwise aligned along the lateral margins. The maxillae are wide and expand laterally (at the level of the nasofrontal suture) to contact the jugals. Thus, the lateral contour of the rostrum becomes rather concave in front of the orbits. The posteromedial edge of the maxilla apparently forms the margin of a depressed area that is limited medially by the lachrymal and posteriorly by the jugal, which is more visible on the right side of the specimen. The middle of the fossa probably features a tiny ‘foramen’ ( Fig. 4A, B ). In ventral aspect, the maxillary bears 14 teeth. The tooth row ends anterior to the suborbital fenestra. The alveoli are medially placed, bordered laterally by a planar maxillary surface. This trait is described as a ‘maxillary lip’ in Pachycheilosuchus ( Rogers, 2003) , to connote the ventral folding of the lateral margin of the maxilla. The ‘lip’ is more conspicuous at the posterior maxillary part in such a way that the last three teeth are medially distributed ( Fig. 2B ). The curvature of the tooth row is laterally concave. Alveoli are of similar size, although the 12th and 13th and the second to fourth of the anterior series have a slightly greater diameter. Several teeth are located in situ, and are as slender as those of the premaxilla. The apical region of one tooth crown of the posterior series is preserved, and is the same shape as the anterior teeth. Teeth are well spaced, separated by interalveolar walls. The last three or four teeth are set in a laterally crested eminence but in separated alveoli. A posterior maxillary process without dentition and with a rough texture ends in a depressed area that is laterally bordered by the jugal ( Fig. 2B ). The ventral sutures with the jugal and ectopterygoid are not clear, as the mandible covers the area.

Nasals are not sculptured by pits but are ridged. They form an anterior narrow spine and widen posteriorly. Their lateral contours are straight, converging to contact the prefrontals and frontal. Lachrymals do not contact nasals, and the maxilla sends a short caudal process between the lachrymal and prefrontal.

The prefrontal and lachrymal are about the same length. They do not surpass the lateral expansion of the nasals anteriorly. The lachrymal is triangular and broader than the prefrontal. It makes up almost all the anterior orbital border, so that the prefrontal only forms the anteromedial corner of the orbital contour. Allodaposuchus also has wide lachrymals that occupy the anterior orbital border of the orbits ( Buscalioni et al., 2001; Delfino et al., 2008). The lachrymo-jugal contact is located at the lateral contour of the orbit. Jugals are caudally retracted, and thus do not surpass the anterior orbital border. An extreme condition of this trait is evident in the basal Eusuchia Iharkutosuchus from the Upper Cretaceous of Hungary ( Ösi et al., 2007) and in P. trinquei . The orbital contour is subtrapezoidal, with a rectilinear, almost orthogonal (to the sagittal plane), anterior edge.

The postorbital is anteriorly rounded and is dorsally narrow, forming a narrow bar with the anterior contour of the supratemporal fenestra. Most of its frontal suture is located at the supratemporal fossa. A stout bar (not as robust as that of Hylaeochampsa , see character 70) is inset dorsally. The bar has an anterolateral protuberance.

The frontal probably has a short anterior projection. The suture with the nasal is acuminated in the middle. The projection does not extend beyond the prefrontal suture. The surface is profusely sculptured and the orbital rims are not elevated. It forms the lateroposterior corner of the orbits medially. It contacts the postorbitals laterally in a parasagittal suture. The frontal enters the supratemporal fenestra and participates deeply in the fossa, avoiding broad contact between the parietal and postorbital. The frontal contacts the parietal in a rectilinear suture.

The parietal has an indented posterior contour and laterally is slightly convex. The interfenestral and interorbital widths are equal. The parietal expands laterally, developing a broad medial supratemporal fossa.

Squamosals have convex lateral margins and a flat dorsal surface. The rim bordering the fenestra is thick. They are lateromedially short, and anteriorly they narrow at their dorsal contact with the postorbitals. The squamosal lobule is short and bends posteriorly. A rim for the earflaps is visible at its posterolateral extreme (similar to that in Allodaposuchus precedens ). The otic area is posteriorly conformed by the relation between the squamosal and the exoccipital; the quadrate is not involved due to its shortness.

The jugal is a relatively short bone and is laterally bowed. It is plate-like with a wider anterior than posterior part. Its dorsal margin is elevated at the postorbital bar, forming a curved contour at the orbit that ends in a reduced anterior notch. It forms the base of the postorbital bar, which exposes its base posteriorly in the area where the jugal has a concave dorsal edge that shapes the ventral margin of the infratemporal fenestra. Dorsally, the jugal features a short and blunt posterior process ( Fig. 4B , right side). Ventrally, the jugal contacts the maxilla at the level of the last tooth ( Fig. 2B ). A ventral portion of the ectopterygoid is visible in ventral view ( Fig. 2B ), and in dorsal aspect the ectopterygoid is visible inside the orbit ( Fig. 4B ).

Dorsally, the quadrate branch is extremely short, extending to the level of the paraoccipital process. The dorsal suture between the quadrate and the quadratojugal is situated in a furrow; in other words, the quadrate and quadratojugal are not at the same level, the latter being more dorsally situated. The quadrate lateral edge that contacts the quadratojugal is depressed and laterally concave, shaping the contour of a medial expansion of the quadratojugal that overlaps the quadrate. The anterior suture of the quadrate and quadratojugal is not clear and it is difficult to determine whether the quadrate forms the posterodorsal margin of the infratemporal fenestra or is a narrow dorsal spine of the quadratojugal. P. trinquei lacks the foramen aereum ( Rogers, 2003) but this feature is unclear in the quadrate of the Pietraroia specimen. The craniomandibular articulation is one of the singular traits of P. ormezzanoi , with a rather equivalent construction to other basal eusuchians such as Hylaeochampsa and Iharkutosuchus (see below). The ‘compound’ condyle is made up of a medial quadrate portion and a lateral quadratojugal condyle. It is distributed in two angles: the quadratojugal ‘condyle’ (i.e. a round protuberance) is almost parallel to the sagittal plane and the quadrate is at about 75 ° to it. The whole structure (quadrate and quadratojugal) forms a broad arch that extends medially to occupy a large part of the occipital area, and its width may be appreciated over the glenoid retroarticular surface (see retroarticular in shadow, Fig. 4B ). The quadrate condyles are posteroventrally oriented. The medial condyle is deeper than the lateral condyle (note in data matrix ‘N’ for character 112). The articular contour is expanded in the middle between the two condyles and a depressed area lies in front of the lateral quadrate condyle. Ventrally the quadrate surface bears a boss aligned with the quadratojugal condyle and located parallel to the quadratojugal suture ( Fig. 5 ).

The ventral quadratojugal protuberance has a rough bony texture, it is vertically deflected and placed at the lateral edge of the quadratojugal, and lateral and anterior to the quadrate articular surface. Thus, contrary to Hamadasuchus rebouli ( Larsson & Sues, 2007) , the ‘condyle’ is not continuous with the distal articular surface of the quadrate. The contour of the quadratojugal overlapping part of the dorsal surface of the quadrate can be seen in Figure 5. A concave area rostral to the ‘condyle’ has been interpreted as the anterior ventral branch of the quadratojugal. In dorsal aspect ( Fig. 4B ), the left quadratojugal ‘condyle’ is displaced and rotated, exposing a furrow between the quadrate and the quadratojugal. The quadratojugal is laterally bowed, short, and dorsally sculptured. It is laterally crested at the level where the skull reaches its maximum width, and its ventral contour probably overhangs the dorsal margin of the mandible covering the craniomandibular area laterally. Its dorsal suture with the jugal is clearer in PC-2 than in PC-1. The quadratojugal forms the inferior posterior margin of the infratemporal fenestra.

The palatine forms the lateral margin of the suborbital fenestra. The anterior extension of the palatomaxillary suture cannot be fully determined, although it is anteriorly acute and short. The palatine bar has straight to convex lateral borders (although they are deformed by compression) and is wide. The palatine projects a posterior process at the pterygoid where it borders the choana, overlying the pterygoid. At the posterior suture between the pterygoid and palatine, the posterior palatine processes are set in a depressed area of the pterygoid that can be traced from the margin of the suborbital fenestra up to the middle of the pterygoideal lamina ( Fig. 6 ).

The pterygoidean plate is trapezoidal; its anterior margin is shorter and has medially convergent lateral sides. The anterior border of the pterygoid is notched, forming the posterior margin of the narrow suborbital fenestra. The choana is separated by an internal septum and has a rounded posterior contour. It has a typical shape of a eusuchian choana (i.e. without any anterior depression) although its anterior margin is formed by an inverted V-shaped palatine processeses. The pterygoidean flanges are thickened at their posterior tips. P. ormezzanoi shares with Iharkutosuchus and Hylaeochampsa the reduced extension of the pterygoidean flanges, which do not extend laterally as far as the medial condyle of the quadrate ( Fig. 2 , left). The posterior pterygoidean contour is not clear, although it may bear two short parasagittal posterior prolongations.

The occipital arch is short and concave. It is distorted by compression and the sutures are difficult to delimit, the dorsoventral dimension being more affected. The supraoccipital is a wide bone that is slightly exposed at the skull table. Part of the postemporal fenestra is visible, and has reduced postemporal processes that are not dorsocaudally expanded. The squamosal forms a concave ventral suture with the exoccipitals. The lateral paraoccipital process is vertically tall, although it is not caudally projected. The posterior squamosal lobes are reduced and aligned with the paraoccipital process.

The exoccipitals are broad and particularly deep. They may have a mid-crest at the level of the foramen magnum, dividing the exoccipital surface into a dorsal surface and a ventral plane (compressed in specimen PC-1). The specimens exhibit a prominent lateral expansion of the exoccipitals that develops a thick, oblique, lateroventrally directed protuberance. The posterolateral margin of the exoccipitals slightly overhangs the medial border of the quadrate ( Fig. 2B ).

The basioccipital is partially damaged in both specimens. The occipital condyle is broken. The basioccipital is rather narrow and has not developed strong basitubera. The basisphenoid plate is thin and barely exposed (if at all) in ventral view in front of the basioccipital.

MANDIBLE

The mandible of P. ormezzanoi is greatly modified in comparison with Crocodylia ( Fig. 7 ). The PC- 1 specimen exposes the ventral view of the mandible, as well as an occlusal view of the right dentary. The mandibular rami are medially placed relative to the maxillary contour, especially at its anterior portion. The dentary does not match anteriorly with the premaxillae. All the dentary teeth occlude lingually to the maxilla, and maxillary teeth occlude the labial to the dentary tooth row. The only location where the mandible and maxillary seem to be complementary is the posterior region where the posterior maxillary teeth are set in an eminence ( Fig. 2B ). There is no festooning of the labial margin. The mandibular rami progressively increase in height, which can be estimated from the splenial lamina, which is twice the height of the anterior part posteriorly.

The symphysis is short, extending to the anterior margin of the fourth alveolus. Anterior teeth are apparently rostrally directed and the alveolar contours are labially displaced. Rogers (2003) suggested that the anterior dentary teeth in P. trinquei would protrude beyond the dentary edge. The symphysial area is curved and the dentary has a rounded outline. The tooth row is sigmoidal, with the posterior series inwardly directed. The tooth alignment means that the dentary has two occlusal areas: a medial lingual expanded margin and a posterolateral labial margin behind the 10th alveolus. These expansions might be boosted by the dorsal compression. A line of successive foramina is medially set along the third to the tenth alveoli. The dentary caudally ends in an acute projection that extends lateroventrally ( Figs 2B , 7 ), and so is not forked. The articular facet for the surangular extends to the dorsolateral margin of the dentary. The anterior part of the surface is located at the level of the final two atrophied dentary alveoli (see ‘d-san’ in Fig. 7 ). Therefore, there is no anterior surangular spine medial to the tooth row; instead the bone adjoined to the last dentary tooth is the posterior extension of the splenial. The ventral part of this acute caudal projection can be recognized in the left dentary ( Fig. 2 ), situated between the surangular and angular. The mandible does not possess an external mandibular fenestra.

The dentary bears 17 alveoli and three others that are apparently atrophied. The latter are widely separated (interalveolar distance is slightly less than the alveolar diameter). Alveoli for dentary teeth 3 and 4 are the same size but separated. This trait is similar in P. trinquei . The mandibular teeth are hypotrophied (especially the anterior ones); their crowns are half the length of those of the maxilla. However, the alveoli are bigger than the tooth diameter. Mandibular teeth and alveoli are homodontic. Labial to the dentary tooth row the maxillary teeth have left abundant pits, especially from the 14th tooth backwards. The last three atrophied alveoli are located in an elevated area with a rough texture. At this level, medial and caudally, the specimen keeps part of the splenial attached that corresponds to the dorsal expansion of the splenials (see also left splenial in Fig. 2 ) forming a buttress surface. The final teeth of the dentary and the splenial platform are consistent with a ‘crushing area’ ( Fig. 7 ) that would match the posterior maxillary eminence.

The splenial does not occupy the symphysial area. Splenials are laminar and have a thick occlusal expansion at their posterior part. It features a rostral perforation for the mandibular ramus of cranial nerve V.

In specimen PC-1 a stout process with a round tip lies on the top of palatines and has been interpreted as being part of the mandible. The base of the process connects with the dorsal surface of the surangular. This indicates that the dorsal contour of the surangular expands dorsally to form a rather high and stout process that is internally concave ( Fig. 2 ). This surangular condition is similar to that of Iharkutosuchus ( Ösi et al., 2007: fig. 6; Ösi, 2008). The process is inset medially to the jugal arch, as can also be seen in the left mandibular ramus of the same specimen. The surangular descends posteriorly and contacts the articular laterally, tapering almost to the tip of the retroarticular process. The region of the cranio-mandibular articulation is not clear in specimen PC-1. Nonetheless, the surangular seems to exhibit a medial surangular rim lateral to the glenoid fossa ( Figs 2B , 4 ). The dorsal medial surface of the surangular where the coronoid articulates is exposed on the right side of specimen PC-1. The coronoid appears to lie just ventral to it and is disarticulated, exposing its dorsal process and a long posterior projection that should be covered by the angular. Anterior to this element there is a wide concave contour that conforms the anterior corner of the mandibular adductor fossa.

The angular exposes its inner and dorsal views. It contacts the posterior projection of the dentary anteriomedially with a relatively short spine. The right angular is detached from the mandible in PC-1. At the cranial end of this isolated element, the exposed notch denotes the contact with the splenial. The angular exposes its concave internal aspect. The angular would probably cover the retroarticular process ventrally.

The articular is exposed in the two specimens, although neither its glenoid fossa nor anterior tip is fully exposed. The retroarticular is apparently placed above the level of the dentary margin. It is dorsally curved so that its posterior tip faces dorsally. The retroarticular has a triangular contour that is slightly wider than it is long. The retroarticular is unusual in having a complex glenoid area ( Fig. 4B ). A large and transversely wide anterior fossa houses the ‘compound’ quadratojugal and quadrate condyles. The broadness of the fossa is comparable with that described in Iharkutosuchus ( Ösi, 2008) , which is formed by a small depression of the surangular dorsal to the articulation of the articular. A transverse rim delimits the posterior glenoid wall. Behind the thick rim is a narrow ventrally sloping surface that ends in two thick, dorsally developed tubercles that form the posterior wall of this caudal area. Posterior to the tubercles the retroarticular develops a concave surface, ending in a round and thickened tip.

Figures

Figure 1. A, Pietraroiasuchus ormezzanoi from the Lower Albian of Pietraroia Plattenkalk (specimen PC-1). B, illustration of the skeleton based on photographs of the specimen and drawn using Adobe Illustrator. Fractures have been filled in grey. Fracture 1 is original; fracture 2 is a broken area that fits perfectly in the specimen, so the centrum on both sides of the fracture is the same element. Scale bar = 150 mm. Ant, anterior; post, posterior. The cartilaginous sternal ribs are depicted in light grey. Thoracic vertebrae 1–10.

Figure 2. Skull of Pietraroiasuchus ormezzanoi (Lower Albian of Pietraroia, Italy) specimen PC-1 exposed in ventral aspect. A, photograph. B, illustration of the skull based on photographs of the specimen and drawn using Adobe Illustrator. Bottom left, magnified cervical centrum in posterior view.

Figure 3. Photograph of Pietraroiasuchus ormezzanoi (Lower Albian of Pietraroia Plattenkalk, Italy) specimen PC-2 exposed in dorsal aspect. The illustration of the skeleton is based on photographs of the specimen and drawn using Adobe Illustrator. 1, 2, and 3, ribs; I–VIII, osteoderms of the dorsal armour.

Figure 4. Skull of Pietraroiasuchus ormezzanoi from the Lower Albian of Pietraroia (specimen PC-2). A, photograph. B, illustration of the skull based on photographs of the specimen and drawn using Adobe Illustrator.

Figure 5. Photograph and interpretation of quadrate and quadratojugal in Pietraroiasuchus ormezzanoi.

Figure 6. Detail of the choana of Pietraroiasuchus ormezzanoi, photograph and interpretation.

Figure 7. Composite figure with a mounted photograph of the mandible and illustration of Pietraroiasuchus ormezzanoi.