Cranial anatomy of the Late Triassic phytosaurMachaeroprosopus, with the description of a new species from West Texas

Abstract

The skull anatomy of a new species of the phytosaur Machaeroprosopus is described for the first time on the basis of two specimens from the Upper Triassic Cooper Canyon Formation of Texas. Additional information is provided by a third specimen referred to Machaeroprosopus sp. A paranasal bone, an additional paired element of the narial region, is identified. Important new data are presented for the braincase, including the morphology of the epipterygoid and presphenoid, an anterior process of the prootic, an anteroventral process of the laterosphenoid, and a parasphenoid process. Machaeroprosopus lottorum n. sp. is characterised by four apomorphies: a supratemporal fenestra closed on the skull roof with bevelled anterior rim, a comparatively short squamosal, a flat and rugose narial rim, and medially extended palatines that come close to form an ossified secondary palate. With respect to the supratemporal fenestra, the supraoccipital–parietal complex and several features of the squamosal, Machaeroprosopus lottorum n. sp. bridges the morphological gap between species previously referred to the genera Pseudopalatus and Redondasaurus. A parsimony analysis of known species of Machaeroprosopus supports the hypothesis that the development of the rostral crest in Machaeroprosopus is a sexually dimorphic feature, and questions the validity of the genus Redondasaurus. Consequently, Redondasaurus is here considered a junior synonym of Machaeroprosopus.

The braincase ofMesosuchus browni(Reptilia, Archosauromorpha) with information on the inner ear and description of a pneumatic sinus

“…The deeply recessed nature of the fenestra ovalis of Mesosuchus is similar to Stenaulorhynchus (Benton, 1983) and Teyumbaita (Montefeltro, Langer & Schultz, 2010), but contrasts with Hyperodapedon (Benton, 1983), and Rhynchosaurus (Benton, 1990). Outside Rhynchosauria, recessed fenestrae are found in the archosauriforms Erythrosuchus (Gower, 1997) and Sarmatosuchus (Gower & Sennikov, 1997), but also in phytosaurs (Hungerbühler et al, 2012). The implications of a recessed fenestra ovalis are not clear.…”

Relationships of the Indian phytosaur Parasuchus hislopi Lydekker, 1885

“…This is a node‐based taxon using the type species of each currently recognized (Hungerbühler et al . ) mystriosuchin (= pseudopalatine) genus as an internal specifier. These taxa have been used as specifiers to retain consistency in composition as much as possible with the traditional ‘Pseudopalatinae’, but follow recommendations for phylogenetic nomenclature in prioritizing the use of type species in definitions.…”

A new phylogenetic analysis of Phytosauria (Archosauria: Pseudosuchia) with the application of continuous and geometric morphometric character coding

“…The monophyly of the newly diagnosed Machaeroprosopus with respect to ‘ Redondasaurus ’ was tested by Hungerbühler et al (2013); the two species of ‘ Redondasaurus ’ were previously found to nest paraphyletically within Machaeroprosopus (Hungerbühler, Chatterjee & Cunningham, 2003). The primary purpose of the analysis was, however, to test the phylogenetic position of the newly described species Machaeroprosopus lottorum .…”