SAUROPTERYGIA Owen, 1860

PLESIOSAURIA De Blainville, 1835

PLESIOSAUROIDEA Gray and Welles

CRYPTOCLIDIDAE Williston, 1925

Vinialesaurus nov. gen.

Derivation of name: from Viñales, town in western Cuba in which area the fossil was found, and Sauros (Greek), lizard.

Type species: Cryptocleidus ? (sic) cuervoi caroli DE LA TORRE & ROJAS, 1949.

Diagnosis: as for type and only species of the genus, Vinialesaurus caroli (DE LA TORRE & ROJAS, 1949).

Vinialesaurus caroli (DE LA TORRE & ROJAS, 1949), new combination

Cryptocleidus ? (sic) cuervoi caroli DE LA TORRE & ROJAS, 1949, p. 199, pl. 6, figs. 1–2.

Muraenosaurus leedsii SEELEY, 1874 - Welles, 1962, p. 9.

Cryptoclidus caroli (DE LA TORRE & ROJAS, 1949) - Iturralde-Vinent & Norell, 1996, p. 10, fig. 6.

Type specimen: MNHNCu P3008, anterior part of skull and mandible with associated atlas-axis.

Locality and horizon: somewhere between Laguna de Piedra and La Palma, in the Sierra de Los Organos, Pinar del Río Province, western Cuba; Jagua Vieja Member, Jagua Formation, Middle-Late Oxfordian, Late Jurassic (Iturralde-Vinent and Norell, 1996).

Diagnosis: skull with lateral supraorbital process on frontal; large external nares and orbits; small vertical jugal; vomer anteriorly rounded; anterior interpterygoid vacuities lacking; large double internal nares divided by a maxillary-vomer bar; reduced tooth ornamentation.

4. Description

4.1. Preservation

The skull is preserved from the tip of the rostrum to the anterior rims of the temporal fenestrae. The anterior parts of both mandibular rami are preserved, the right one back to the coronoid process of the surangular. They are slightly compressed but not distorted. Most sutures are not visible. This feature may be ontogenetic (if the specimen was an old adult sensu H3>4.2. Skull (Fig. 2 and Fig. 3)

In front of the external nares, the snout is low, short and convex; more posteriorly, the skull gently rises up to the pineal foramen. Between the nares, the premaxillae is markedly convex from side to side and meet the frontal without visible suture in a rugose area exhibiting two deep grooves (Fig. 2 and 3). In ventral view, the premaxillae bears five pairs of alveoli, some of the left side bearing teeth. The first is the smallest whereas the third and the fourth are the largest (anteroposterior diameters of the alveoli in cm: 0.7–1.1–1.4–1.3–1.1). Posteromedially to the main alveoli, are located five replacement ones, some showing teeth in eruption.

Fig. 2. Vinialesaurus caroli (DE LA TORRE & ROJAS, 1949) new combination, MNHNCu P 3008, near Viñales, western Cuba, Jagua Vieja Member, Jagua Formation, Middle to Late Oxfordian, Late Jurassic. A, B, C: skull in dorsal, ventral and right lateral views; D: mandible in right lateral view; E, F: atlas-axis in left lateral and anterior views. Graphic scale: 10 cm. Abbreviations used: ata, atlas arch; atc, atlas centrum; axa, axis arch; axc, axis centrum; cp, coronoid process; de, dentary; en, external nares; fr, frontal; g, frontal groove; hr, hypapophyseal ridge; in, internal nares; ju, jugal; mx, maxilla; nc, neural canal; p, maxillary protuberance; pal, palatine; par, parietal; pf, pineal foramen; piv, posterior interpterygoid vacuity; pmx, premaxilla; pt, pterygoid; s, supraorbital process; sa, surangular; tp, transverse process; vo, vomer.

Fig. 3. Vinialesaurus caroli (DE LA TORRE & ROJAS, 1949) new combination, MNHNCu P 3008, near Viñales, western Cuba, Jagua Vieja Member, Jagua Formation, Middle to Late Oxfordian, Late Jurassic. Photographs of skull, mandible and atlas-axis. A, B: skull in dorsal and ventral views; C: mandible in dorsal view; D, E: atlas-axis in left lateral and anterior views. Graphic scale: 10 cm for A, B, C and 2 cm for D and E.

The premaxillary–maxillary suture is marked by a slight constriction visible in dorsal and ventral views. The teeth around this suture are smaller than the other. Dorsally, this suture is difficult to distinguish but seems to be straight and to run from the lateral border of the snout, behind the fifth premaxillary alveolus to the anterolateral corner of the external naris margin.

Posterior to the premaxillary–maxillary constriction, the maxilla is slightly sinuous from the first to the fifth maxillary alveolus and then becomes straight up to the posteriormost and smallest alveolus. The maxilla's anterior orbital margin exhibits a small protuberance (Figs 2 and 3). A similar structure has been observed in Cryptoclidus eurymerus SEELEY (Brown, 1993, fig. 1b). Below the orbit, the maxilla is slender as in cryptoclidids and in contrast to `plesiosaurids' and elasmosaurids (excepting Muraneosaurus) where it forms a wide bar. The maxilla bears 10–11 alveoli but it is incomplete. The first alveolus is small and marks the beginning of the slight curvature previously mentioned. This undulation bears five alveoli of which the three median are the largest (diameters in cm: 0.6–0.9–1.1–1.2–0.6). Posteriorly, there are five or six small alveoli equisized, but difficult to observe because of poor preservation in this area. As in the premaxillae, replacement alveoli are also present on the maxilla, posteromedially to the main ones.

The frontal is roughly quadrangular so that the interorbital bar is wide. It is deeply grooved along its dorsal midline so that it seems composed of two bones not completely united, a condition often observed in plesiosaurs. Laterally, at about the middle of the orbit, the frontal shows a small supraorbital process (Fig. 2 and 3). Because of the absence of a clear suture in this area, there is no evidence for the presence or absence of prefrontal and postorbital.

The nares are of different sizes, which could be due to preservation and/or preparation. The better preserved left naris is circular and relatively large compared to the size of the snout and orbit, as is typical for cryptoclidids (Brown, 1993).

The orbits are relatively large compared to the length of the snout as in cryptoclidids (orbit length = 2/3–1 snout length) and in contrast with `plesiosaurids' and elasmosaurids (orbit length = 1/2 snout length). It is dorsolaterally oriented, and pear-shaped (posterior transverse diameter about 5 cm, anterior transverse diameter about 2.5 cm).

The jugal appears a delicate L-shaped bone, vertically oriented and expanded anteriorly where it contacts the maxilla (Fig. 2C).

Only the anterior portion of the parietal is preserved, enclosing the pineal foramen and delineating the anterior border of the temporal fenestrae. Its sutural contact with the frontal is not identifiable.

In ventral view, the suture between premaxillae and vomer is almost rounded in outline and not V-shaped as is typical for other plesiosaurs (Fig. 2 and 3). The vomer forms a strong bar between the internal nares, convex from side to side and projecting ventrally below the level of the maxilla. The vomer expands posterior to the internal nares and its suture with palatine and pterygoid is also rounded. The premaxillary–maxillary suture ends in the anterolateral corner of the anterior pair of internal nares, whereas the vomero-palatine suture ends in the posterolateral corner of the posterior pair of internal nares. The maxilla enters the lateral margin of the internal nares.

The pterygoid–palatine region is slightly convex. It has not been possible to identify the sutures of these two bones with the maxilla or with the ectopterygoid. The pterygoids enclose large posterior interpterygoid vacuities, but anterior interpterygoid vacuities are absent.

The internal nares are located medially on the palate, separated by the wide vomer. They are characteristically very large and divided by a superficial maxillary-vomer transversal bar, so that they appear as double internal nares, although they communicate below the bar (Fig. 2 and 3). This is considered here as an autapomorphy of this genus. It should be noted that these large and divided into two parts internal nares are not the result of an artifact of preservation or preparation because they are symmetrical and bear natural margins. The anterior openings are elliptical, posterolaterally oriented and larger than the posterior ones which are circular. Some pliosaurs show specializations around the internal nares, comparable to but not identical with that of Vinialesaurus. In Rhomaleosaurus megacephalus (STUTCHBURY), there is a pair of grooves on each side of the palate. The medial one runs to the internal naris and the lateral one to a large, posteriorly located foramen (Cruickshank, 1994). In Rhomaleosaurus thorntoni ANDREWS, there are two closed foramina located in front of the internal naris, both lying in the same groove (Cruickshank, 1996). Finally, Pliosaurus brachyspondylus (OWEN) also exhibits two foramina located in the same groove but behind the internal nares (Taylor and Cruickshank, 1993). In all of these species, both the choanae and the additional foramina remain very small. In MNHNCu P3008, there is no groove around the internal nares which are very large and divided into two by a maxillary-vomer bar although remaining in connection below this bar. The communication between the anterior and posterior part of the nares excludes the possibility of being large nutritive foramina.

4.3. Mandible (Fig. 2 and Fig. 3)

The mandible is narrow. The symphysis reaches the anterior border of the fourth alveolus dorsally and the anterior border of the fifth alveolus ventrally.

The right dentary is complete and bears 17 alveoli with teeth, some of them damaged during preparation when separating the skull from the mandible. The first five teeth are about equal in size (diameter from 1 to 1.3 cm). The sixth to the 17th alveoli gradually decrease in size to 0.5 cm.

The splenial is a very thin, vertical plate of bone, which reaches the symphysis but does not enter it. Posteriorly, it rises up from the level of the 10th alveolus to form the internal face of the coronoid process together with the surangular. The coronoid process is incomplete but appears to be low. Remains of the angular are preserved on the right mandibular ramus, below the coronoid process.

The teeth are conical, acute, slightly recurved and procumbent. The enamel crown ornamentation is reduced and consists of very dense fine striations. Because the teeth have been damaged, more details are not available.