Melanosuchus, Gray, 1862

Scheyer, TM & Delfino, M, 2016, The late Miocene caimanine fauna (Crocodylia: Alligatoroidea) of the Urumaco Formation, Venezuela, Palaeontologia Electronica 176 (4), pp. 1-57 : 18

Genus MELANOSUCHUS Gray, 1862 Caimaninae aff. Melanosuchus fisheri Medina, 1976

The genus Melanosuchus was described by Gray (1862), to accommodate the living black caiman Melanosuchus niger ( Spix, 1825) as type species. Medina (1976) described Melanosuchus fisheri based on two fossils from the Urumaco Formation (at the time thought to be Pliocene in age) of Falcón State, Venezuela. The holotype skull MCNC-243 ( Figure 12.1-4 ) and one referred skull, MCZ 4336, both are only partly preserved and suffered some distortion. Medina (1976) mentioned that M. fisheri would represent the first fossil record of the genus and that it is also distinct from the living species M. niger ( Spix, 1825) . The revision of the type material of M. fisheri is currently the subject of a further specific contribution on the South American crocodylians, for which we will refrain from adding to its osteological description here.

An additional specimen from Urumaco, AMU- CURS-234 ( Figure 12.5-8 ), consists of an almost complete skull and associated lower jaw. It was found at the El Hatillo locality, associated with few postcranial remains, within the lowest part of the Upper Member of the Urumaco Formation. The specimen was previously recognised as Melanosuchus fisheri ( Scheyer et al., 2013) , but re-examination showed a lack of clear sutures of the skull and mandible bones. It shares however the slender, triangular skull shape with the holotype, and it lacks closely spaced crushing teeth in the posterior part of the mandibles.The lower jaws are long and gracile. The skull is otherwise dorsoventrally compacted and the quadratojugals and quadrates are missing on both sides, whereas the jugals are damaged and missing the posterior section. The lower jaw consists of both rami in articulation, but the latter are damaged posterior to the craniomandibular articulation with the articular and angular and retroarticular process being incompletely (right side) or not preserved (left side).

Figures

FIGURE 12. Photographs of the holotype skull of Melanosuchus fisheri (MCNC-243; 1-4) and the skull and associated lower jaw assignable to Caimaninae aff. Melanosuchus fisheri (AMU-CURS-234, 5-8). 1, skull in dorsal view. 2, close-up of the sutures between the frontal, prefrontals and posterior portion of nasals. Compare to interpretative drawing in Figure 4.1. 3, skull in left lateral view. 4, skull in occipital view. 5, 6, skull in dorsal and ventral view. 7, 8, lower jaw in dorsal and ventral view. Abbreviations: f, frontal; n, nasal; prf, prefrontal.