Portugalosuchus azenhae, 2019

Mateus, Octávio, Puértolas-Pascual, Eduardo & Callapez, Pedro M., 2019, A new eusuchian crocodylomorph from the Cenomanian (Late Cretaceous) of Portugal reveals novel implications on the origin of Crocodylia, Zoological Journal of the Linnean Society 186, pp. 501-528 : 505-513

PORTUGALOSUCHUS AZENHAE GEN. ET SP. NOV.

urn:lsid:zoobank.org:act:1C6E6EB7-4F58-46D2-BCA7-AFA13D647493

Etymology: ‘ azenhae ’ after Matilde Azenha, the geologist that discovered the specimen.

Holotype: ML1818 , partial skull and mandible ( Figs 2–10) recovered in anatomical association and belonging to the same individual (Supporting Information, Fig. S 26). The specimen is housed in the Museu da Lourinhã ( ML), Lourinhã, Portugal. ML1818 is comprised of the posterior part of left maxilla, posterior parts of prefrontals and lacrimal, posterior fragments of the nasals, left jugal, frontal, parietal, incomplete postorbitals, squamosal, supraoccipital, exoccipital, basioccipital, pterygoid, palatines and ectopterygoid. Furthermore, ML1818 also comprises a section of the left mandible, composed by the posterior portion of the dentary, with the last four tooth alveoli (two of which with teeth), coronoid, part of the splenial, angular and surangular.

Diagnosis: Autapomorphic traits are marked with an asterisk: *external mandibular fenestra located at the dentary–angular suture, with a posterior process of the dentary forming its anterior and dorsal margins, the angular forming its posterior and ventral margins, and without the participation of the surangular in the fenestra; absence of splenial process between the angular and coronoid; maxilla broadly separates the ectopterygoid from the maxillary tooth row; massive postorbital bar transversely flattened; ventral margin of postorbital bar flush with lateral jugal surface; *dorsal margin of the infratemporal fenestra very elongated, with the quadratojugal contacting the base of the skull table posteriorly, giving a trapezoidal contour to the fenestra (rather than triangular); and braincase wall lateral to the basisphenoid rostrum smooth, without sulci.

Age and horizon: Lower member of Tentúgal Formation (Unit B with Gyrostrea ouremensis ), Upper Cenomanian, Late Cretaceous (standard Biozone of Calycoceras naviculare , about 95 Myr).

Ty p e l o c a l i t y: L i m e s t o n e q u a r r y o f C a s a l d o s Carecos , near Tentúgal, Portugal (40°15’7.98” N; 8°34’8.09” W) .

Description

Skull: The skull is well-preserved, although incomplete ( Figs 2–3), lacking the rostrum, part of right maxilla and the surface of some posterior-most bones. Its maximum proximodistal length is 166 mm, the maximum width is 146 mm, and maximum dorsoventral height is 93 mm. The dorsal surface is sculpted with pits and grooves (consistent with most crocodylomorphs). Based on regression equations applied to extant species ( Hall & Portier, 1994; Wu et al., 2006; Platt et al., 2009), the total cranial length of the specimen ML1818 is estimated at 30–35 cm and the total body length at 2.5– 3 m.

The posterior part of the left maxilla preserves the last five or six alveoli, which are circular and without teeth. The lateral surface of the maxilla is damaged. The last maxillary alveolus is at the same level as the posterior rim of the orbit. In the lateral view, the ventral rim of the maxilla has a gentle curvature as it converges with the jugal posteriorly. Ventrally, the maxilla is posteriorly pinched between the jugal laterally and the ectopterygoid medially. The maxilla does not participate in the infratemporal bar.

Both prefrontals are preserved and their posterior part form most of the anteromedial margin of the orbit. The prefrontals contact the nasal anteriorly and are separated by the frontal medially. The contact with the maxilla is not preserved. The orbital margin of the prefrontals is flush with the skull surface, without any kind of structure or elevation. On the surface of the lateral wall, within the orbit, the prefrontal bears two small foramina. Although most of the prefrontal pillar is surrounded by matrix, it is possible to determine that its dorsal region is anteroposteriorly expanded. Its medial process is not visible.

The left lacrimal is preserved but, as its anterior part is missing, the contact with the nasal is unknown. The posterior part of the lacrimal forms most of the anterolateral margin of the orbit. It has an extensive contact with the prefrontal medially, with the maxilla lateroventrally, and with the jugal posteroventrally. The preserved dorsal surface lacks any kind of elevation or preorbital structure.

The left jugal is present but damaged anterolaterally and the infratemporal bar is incomplete posteriorly. In the lateral view, the dorsal margin of the jugal has a dorsal ridge at the posterolateral margin of the orbit. This ridge is anterior to the postorbital bar, which is flush with the lateral surface of the jugal. The dorsal process participates in the postorbital bar and projects itself dorsally until the midpoint of the posterolateral side of the postorbital bar. The base of the jugal part of the postorbital bar bears a large posterior foramen ( Fig. 6). The presence and size of a medial jugal foramen, anterior to the postorbital bar, is unknown due to the matrix in this area. The infratemporal bar is slender and lateromedially flattened with a lens-shaped cross section.

The left postorbital is nearly complete, while only a small and poorly informative portion of the right postorbital is preserved. The dorsal surface at the skull table is sculpted. The contact with the squamosal occurs posteriorly, lateral to the supratemporal fenestra. In the dorsal view, the postorbital–squamosal suture is V-shaped. The postorbital bar is massive, anteroposteriorly longer than transversely wide, and the jugal extends until half of the extension of the bar ( Fig. 6). Although the anterolateral corner of the skull table is partially eroded, the postorbital bar seems to be dorsally inset below the postorbital ( Fig. 6C–D). The postorbital bar bears a dorsoventrally broad process on its anterior face with a spine at the dorsal portion ( Fig. 6C–D). The presence of a second spine in the postorbital bar is unknown due to slight erosion. In the lateral view, the postorbital contacts the squamosal through a ventrally oriented suture. Although the sutures in this region are not very well marked in the ventromedial view ( Fig. 6), the postorbital seems to contact both the squamosal and a long anterior process of the quadratojugal. The quadrate is posteriorly placed as an acute process between the squamosal and quadratojugal, without any contact with the postorbital.

The frontal is a single bone that forms the posteromedial margin of the orbits. It bears a long lanceolate anterior process, between the prefrontals and the posterior region of the nasals that extends beyond the anterior margin of the orbits. This process contacts the prefrontals laterally and the nasals anterolaterally. Although the anterior-most tip of this process was not preserved, it seems it would not surpass the anterior height of the prefrontals and the lacrimals. The dorsal surface of the frontal is well-sculpted. Posterior to the orbits, the frontal contacts the postorbital laterally and the parietal posteriorly. The contact with the latter occurs with a simple transversely linear suture, placed between the supratemporal fenestrae ( Figs 3A, 7). The frontal has an important contribution (about one-third) in the anteromedial margin of the supratemporal fenestra ( Fig. 7). This margin bears two small longitudinal grooves, horizontally parallel to one another ( Fig. 7). However, these grooves seem to be different from the shallow fossa present at the anteromedial margin of the supratemporal fenestra of some eusuchians, such as Allodaposuchidae .

The parietal is cross-shaped in dorsal view, contacting the frontal anteriorly, the squamosal laterally, and extending through a broad posterior projection above the supraoccipital. The parietal comprises the posteromedial margin of the supratemporal fenestra. The intertemporal bar is noticeably narrow, half the width of the interorbital space. The dorsal surface of the squamosal at the skull table is totally flat. Part of its length bears a midline longitudinal line, which is probably a result of taphonomical damage. The parietal wall of the supratemporal fossa is imperforate ( Figs 7, 8).

The left squamosal is partially preserved, as well as a very small part of the right bone, near the contact with the parietal. The squamosal comprises the lateral margin of the supratemporal fenestra, which is transversely thin. In the dorsal view, the squamosal contacts the quadrate posteromedially and the postorbital anteriorly. In the posterior view, it contacts the exoccipital ventrally and the supraoccipital medioventrally. The lateral margins are smooth and the posterior- and lateral-most regions of the squamosal are not preserved, making unknow the morphology of the groove for the ear valve musculature. On the posterior wall of the supratemporal fossa, there is a large aperture for the temporal canal ( Fig. 8). Around this canal, the parietal and squamosal are widely separated by the quadrate, which enters into the temporal canal ( Fig. 8).

The left quadrate is very incomplete, comprising just a small portion around the inner ear. The right quadrate is more complete, but the posterior part that articulates with the mandible was not preserved. As such, the suture patterning of the squamosal and exoccipital around the otic aperture is not distinguishable. The quadrate projects a ventral process between the pterygoid and basisphenoid in the lateral braincase wall ( Fig. 9).

Only a small portion of the left quadratojugal is present, lateral to the supratemporal fenestra and contacting the squamosal at the dorsal roof of the infratemporal fenestra. This contact is very posteriorly placed in relation to the postorbital bar, so the dorsal roof of the infratemporal fenestra is horizontal, giving the fenestra a trapezoidal, rather than triangular, contour ( Fig. 3D).

The supraoccipital is hexagonal in the posterior view due to the broad horizontal ventral contact with the exoccipitals. In the occipital view, the supraoccipital is posteriorly projected, forming a sagittal vertical ridge associated with two lateral concavities. Although the sutures in this region are not clearly visible, there is minimal participation of the supraoccipital on the dorsal surface of the skull table.

The right exoccipital, lacking the paroccipital process and its ventral-most part, is preserved. In the posterior view, lateral to the foramen magnum, there are three foramina. The medial-most corresponds to the foramen for the cranial nerve XII, and the other two correspond to the foramen vagi. The exoccipital is damaged ventrally, so its participation in the basioccipital tuberosity cannot be confirmed.

The basioccipital is very damaged, so the occipital condyle and the eustachian canals are not preserved. Only a small region of the basioccipital in the right ventral area was preserved, demonstrating that the external surface of the basioccipital, ventral to the occipital condyle, is vertical and posteriorly oriented.

The basisphenoid rostrum is a vertical thin sheet, dorsoventrally elongated, occupying the midline portion of the posterior cavity, below the laterosphenoid ( Fig. 9). In the lateroventral region of the basisphenoid rostrum there is a groove ( Fig. 9), which seems to be the result of erosion rather than a real sulcus, and the rostrum and the pterygoids are not recessed inward. Lateral to the basisphenoid rostrum, there are two perforations that also seem to be breakages rather than true foramina. Ventrolaterally, there is a foramen that may correspond to the palatine ramus of the cranial nerve VII ( Fig. 9). In the lateral braincase wall, the basisphenoid is a thin lamina bordered by the quadrate dorsolaterally, the pterygoid ventrolaterally, the exoccipital dorsomedially and the basioccipital ventromedially ( Fig. 9). The position of this lamina relative to the lateral carotid foramen cannot be determined. Although the occipital region of the basisphenoid is not well preserved, a broad exposure of the basisphenoid ventral to the basioccipital can be inferred, due to the shape and position of the posterior pterygoid process and the preserved parts of the basioccipital.

Only the left laterosphenoid remains. It is very elongated anteroposteriorly, and is x-shaped. It is located below the anteromedial margin of the supratemporal fossa. The anterior-most region and the lateral branch of the capitate process are not completely preserved, so its orientation can not be determined. Ventrally, it has a longitudinal ridge along its entire body. The foramen ovale is placed in the lateral braincase wall ( Fig. 9). This foramen is surrounded by the laterosphenoid anteriorly and the quadrate posteriorly. There is an extensive exposure of the prootic around the trigeminal foramen ( Fig. 9).

Both pterygoids are preserved, but the right one is incomplete laterally and the left one is incomplete posteriorly. This bone contacts the palatine anteriorly, the ectopterygoid laterally, the quadrate dorsally, and comprises the secondary choanae. The ventral surface of the pterygoid is nearly horizontal, except for a gentle transverse concavity towards the midline. The pterygoidal surface, lateral and anterior to the secondary choanae, is flush with the choanal margin. The choana is located very close to the posterior pterygoidal margin. The pterygoid posterior process is tall and prominent.

Both palatines are present, but incomplete anteriorly. The sutures with the maxillae are not distinguishable and, therefore, the morphology and extension of the anterior process of the palatine cannot be determined. The bones form a long bar bordered by the suborbital fenestrae. They contact the pterygoids posteriorly, at the end of the bar, anterior to the posterior margin of the fenestra. The lateral borders are almost parallel along their length and only gently narrower posteriorly. The vomers are only visible in section and are placed in the midline, dorsal to the palatines, totally obscured in the palatal view.

Only the left ectopterygoid is preserved. In ventral view, it contacts the pterygoid posteromedially, the maxilla anterolaterally and the jugal laterally. The anterior ectopterygoid process tapers to a point and the lateral border of the ectopterygoid is separated by the maxilla, avoiding contact with the last tooth alveolus. It gently curves medially, creating a small, subtle projection into the suborbital fenestra, and a bowed lateral margin of the fenestra. The posterior-most end of the ectopterygoid is not preserved. However, only the tip is missing and thus the ectopterygoid does not reach the posterior tip of the lateral pterygoid flange. Dorsally, the ectopterygoid extends along the medial face of the lower half of the postorbital bar.

The supratemporal fenestra is circular and nearly the same size as the orbit. The margins do not upturn, nor form any distinctive lip, and do not overhang the supratemporal fossa. The orbits have a sub-triangular outline, with a broader posterior half. The margins of the orbits are flush with the skull surface, not upturned or forming any different structure. The suborbital fenestra is three times longer than wide, being straight medially and curved laterally. The posterior part of the fenestra is broader than the anterior one, which ends in an acute shape. The fenestra’s rim curvature is gentle and does not bear a posterior notch. The otic region is badly damaged and, therefore, it is impossible to see its sutural patterning. The secondary choana is a small, round, undivided fenestra slightly asymmetrically placed at the posterior margin of the pterygoids. The choana is damaged at its posterior section, but it is clear that the aperture is ventroposteriorly directed.

Mandible: The left mandible ( Figs 4, 5) is partially preserved and is comprised of the posterior region of the dentary, the last four alveoli (two of them with teeth), the posterior part of the splenial, the anterior parts of both angular and surangular, and the coronoid.

The splenial is broad and occupies almost all of the medial surface of the preserved mandible. The splenial contacts the foramen intermandibularis caudalis and the angular posteroventrally, the coronoid posteriorly, the surangular posterodorsally and the dentary anteriorly. The medial surface is not perforated. However, as the region of the splenial anterior to the last four teeth is damaged, the presence of the exit for the cranial nerve V can not be determined. There is no posterior process of the splenial separating the angular and the coronoid.

The coronoid is badly preserved. It has a ‘boomerang’ shape and is placed in the anterior rim of the mandibular adductor fossa or Meckelian fossa. The anterior edge is damaged, so it is not clear where the foramen intermandibularis medius is located. The superior edge of the coronoid slopes strongly anteriorly, at an angle of about 45º from the horizontal plane. As the posterior region of the inferior process of the coronoid is broken, it can be seen in cross-section, showing the overlaps with the angular and the Meckelian fossa. The inferior process of the coronoid overlaps strongly into the inner surface of the Meckelian fossa. As the medial surface of the coronoid is partially damaged, it is impossible to know if it is perforated.

The dentary bears the last four alveoli, two of them with teeth. Posteriorly, the dentary is wedged between the angular and surangular, in the lateral view. The lateroventral area of the dentary is crossed by a welldefined longitudinal groove.This groove starts anteriorly at the height of the last dental alveolus and runs posteriorly to intersect the anterior margin of a small-sized and narrow, slit-shaped fenestra ( Fig. 10). This fenestra, here interpreted as the external mandibular fenestra, is between the dentary–angular suture, with the dentary forming its anterior and dorsal margins, and the angular forming its posterior and ventral margins. The fenestra is not laterally coincident with the Meckelian fossa, as it is slightly more anterior than the latter. The preserved teeth are conical and ornamented with fine longitudinal striations ranging from the base to the apex. The mesial and distal carinae are very smooth and almost as lightly marked as the enamel striation.

The angular covers most of the ventral aspect of the mandible. At the lateral surface of the mandible, the surangular contacts the angular posterior to the dentary’s posteriormost portion. In the medial view, and below the inferior process of the coronoid, the anterior process of the angular is visible. Although the surface is partially broken, this process extends dorsally towards a cavity, covered by matrix that is likely the foramen intermandibularis caudalis. The foramen is small, ellipsoidal and posteriorly placed relative to the Meckelian fossa, without reaching or surpassing the height of the anterior margin of the fossa.

The surangular is incomplete and only the anterior-most portion of the bone is preserved. This bone covers most of the dorsal aspect of the mandible posterior to the toothrow and reaches anteriorly to the posterior margin of the last tooth alveolus, without surpassing it. In the lateral and dorsal views, the surangular anterior processes are unequal in their contact with the dentary; the dorsal is much longer than the ventral. The surangular does not participate in the external mandibular fenestra. Dorsal to the mandibular adductor fossa, the surangular bears a conspicuous process that produces a dorsal concavity.