Crocodylus acutus, FROM LAGO ENRIQUILLO

Morgan, Gary S., Albury, Nancy A., Rímoli, Renato, Lehman, Phillip, Rosenberger, Alfred L. & Cooke, Siobhán B., 2018, The Cuban Crocodile (Crocodylus rhombifer) from Late Quaternary Underwater Cave Deposits in the Dominican Republic, American Museum Novitates 2018 (3916), pp. 1-1 : 1-

C. ACUTUS FROM LAGO ENRIQUILLO

We examined, measured, and photographed five modern skulls of the American crocodile Crocodylus acutus from Lago Enriquillo in the southwestern Dominican Republic, housed in the MNHNRD in Santo Domingo. The most complete of these skulls of C. acutus (MNHNRD1) is illustrated in fig. 11. All five of the skulls are adults, four are from large individuals, and one is somewhat smaller, in the same size range as the largest fossil skull of C. rhombifer from Oleg’s Bat Cave (see table 1 for measurements of the skulls of C. acutus from Lago Enriquillo ). All five of these skulls of C. acutus lack associated lower jaws and postcranial skeletons. The following comparisons are limited to the samples of modern skulls of C. acutus from Lago Enriquillo and fossil skulls of C. rhombifer from Oleg’s Bat Cave and Ni-Rahu in the Dominican Republic (specimens examined listed in the appendix). The following section provides comparisons of the fossil skulls of Dominican C. rhombifer with modern skulls of C. acutus from localities outside of Hispaniola, as well as skulls of Morelet’s crocodile, C. moreletii , from the Gulf of Mexico and Caribbean coasts of Mesoamerica.

The rostrum of the modern skulls of Crocodylus acutus from Lago Enriquillo is much longer and narrower than in C. rhombifer . The Lago Enriquillo skulls of C. acutus have a prominent convexity, the midrostral boss, located along the midline anterior to the orbit. The midrostral boss is primarily situated on the posterior third of the nasals, but also incorporates small portions of the posteromedial portion of the maxilla, and the anterior portion of the lacrimals and prefrontals. C. rhombifer also has a midrostral boss on the nasals, but it is lower and less prominent. In lateral view, C. acutus has a steep angle in the dorsal margin of the rostrum anterior to the midrostral boss, at about the level of the 7th maxillary tooth. The anterior portion of the rostrum, including both the maxilla and premaxilla, is much shallower in this species compared to C. rhombifer , in which the rostrum is much deeper anteriorly. The orbit is not as prominent in lateral view in C. acutus , owing to a narrower maxilla and weak interorbital ridges. The orbit in C. rhombifer appears larger because of the deep maxilla and anterior process of the jugal below the orbit and strongly upraised ridges on the internal margin of the orbit.

Crocodylus acutus lacks a lacrimal boss and a low transverse ridge on the lacrimals anterior to the orbits, both of which occur in the skulls from Oleg’s Bat Cave. The large midrostral boss is located farther anteriorly along the midline in C. acutus . The American crocodile also lacks the rhomboid- or diamond-shaped structure anterior to the orbits characteristic of C. rhombifer , which is defined by prominent ridges that extend anteriorly from the lacrimals to the nasals and posteriorly from the lacrimals to the prefrontals. C. acutus has low, weak ridges on the medial edge of the lacrimals and also has ridges on the internal margin of the orbits, but these ridges are not nearly as high or prominent as in C. rhombifer . The interorbital region, especially the frontals, is considerably broader and only weakly concave in C. acutus , compared to the narrower and strongly concave interorbital region of C. rhombifer . The low interorbital ridge continues posteriorly to the posteromedial margin of the orbits on the postorbital in C. acutus , where the ridge terminates. Unlike C. rhombifer , there are essentially no ridges on the lateral edges of the cranial table in C. acutus, and no protu-