Abstract
A new fossil MP111209-1 found in the Barremian beds of Sáchica, a town near Villa de Leiva representing the more complete skeleton found in the region is described here. After a detailed study of its morphological characteristics, it is evident that the new specimen represents a new genus and species of brachauchenine pliosaurid from Central Colombia that we named Sachicasaurus vitae gen. et sp. nov. Sachicasaurus is a large brachauchenine (almost 10 m in length) characterized by the following combination of characters: skull exceeding two meters in length, transverse constriction in the rostrum, caniniform teeth present, pineal foramen in a very advanced position, palatines separated in the midline by the pterygoids, very short mandibular symphysis (bearing four teeth positions), reduced number of mandibular teeth (less than 20), slender hyoid bones, 12 cervical vertebrae, cervical centra showing ventral foramina, single rib facet in all cervical centra, at least 40 pre-caudal vertebrae, and ilium with a long posterior projection. Although it is difficult to clearly establish the phylogenetic position of Sachicasaurus viate within Brachaucheninae due to its combination of primitive and derived features, the morphological comparisons and the cladistic analysis show an evident phylogenetic proximity of Sachicasaurus to the Aptian-Albian genus Kronosaurus.
Highlights
Material and MethodsThe fossil record of pliosaurid plesiosaurs ranges from the Lower Jurassic to the Upper Cretaceous
The Colombian material includes a skull and cervical vertebrae recently identified as Acostasaurus pavachoquensis Gómez-Pérez and Noè, 2017 (Gómez-Pérez, 2001; Gómez-Pérez and Noè, 2017) and two nearly complete three-dimensionally preserved skeletons that represent the holotypes of Stenorhynchosaurus munozi Páramo-Fonseca et al, 2016 (Hampe, 2005; Páramo-Fonseca et al, 2016) and “Kronosaurus” boyacensis Hampe, 1992 (Hampe, 1992)
The Barremian pliosaurid genera known in Colombia, Stenorhynchosaurus and Acostasaurus, are smaller in size and clearly differ from the new specimen MP111209-1: Stenorhynchosaurus has a more elongated snout, isodont dentition, and longer mandibular symphysis (Páramo-Fonseca et al, 2016); and Acostasaurus has a shorter preorbital rostrum, large nasal present in contact with the parietal, anterior interpterygoid vacuity absent, longer mandibular symphysis, different arrangement of the heterodont dentition (Gómez-Pérez and Noè, 2017), cervical rib facets in ventrolateral position and double-headed cervical ribs (Gómez-Pérez, 2001)
Summary
Material and MethodsThe fossil record of pliosaurid plesiosaurs ranges from the Lower Jurassic to the Upper Cretaceous. The Russian specimens comprise a fragmentary skeleton of the holotype of Makhaira rossica Fischer et al, 2015, and a nearly complete, three-dimensionally preserved skeleton, the holotype of Luskhan itilensis Fischer et al, 2017 (Fischer et al, 2015; Fischer et al, 2017). The Colombian material includes a skull and cervical vertebrae recently identified as Acostasaurus pavachoquensis Gómez-Pérez and Noè, 2017 (Gómez-Pérez, 2001; Gómez-Pérez and Noè, 2017) and two nearly complete three-dimensionally preserved skeletons that represent the holotypes of Stenorhynchosaurus munozi Páramo-Fonseca et al, 2016 (Hampe, 2005; Páramo-Fonseca et al, 2016) and “Kronosaurus” boyacensis Hampe, 1992 (Hampe, 1992) (as will be discussed later, the inclusion of “K.” boyacensis in the genus Kronosaurus is considered doubtful, and for this reason it is written in quotes). The Australian material comprises fragmentary remains assigned to Kronosaurus queenslandicus Longman, 1924 (Longman, 1924; 1930; 1935; White, 1935; Romer and Lewis, 1959; Kear, 2003; McHenry, 2009)
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