Paleorhinus

Extinct genus of reptiles

Paleorhinus (Greek: "Old Nose") is an extinct genus of widespread basal phytosaur known from the Late Triassic (late Carnian stage). The genus was named in 1904 based on the type species Paleorhinus bransoni, which is known from Wyoming and Texas in the United States. Another valid species, Paleorhinus angustifrons from Bavaria, Germany, is also commonly referred to the genus. Paleorhinus had a length of about
Paleorhinus has had a complicated taxonomic history involving frequent synonymy between diagnostic and undiagnostic material. This is mainly due to the fact that it is a quintessential basal phytosaur, mostly distinguished by a lack of specializations rather than unique traits. Historically, it was common practice to lump all basal phytosaurs into only one or two genera, rendering those genera paraphyletic evolutionary grades ancestral to later phytosaurs. More recently, these grades have been broken up into multiple genera. Hunt and Lucas (1991) referred PPM P217 to P. bransoni. It is an incomplete skull that was collected at Palo Duro Canyon, Randall County, west Texas, from the Carnian aged Camp Springs Member of the Tecovas Formation. Later, Long and Murry (1995) referred additional material, including isolated postcranial remains, to P. bransoni from the Carnian aged Cooper Canyon Formation of the Dockum Group, Howard County, Texas. TMM 31025 172, a complete skull, was collected at Otis Chalk Quarry 1 (also known as SMU 122), TMM 31100 8, 101, 175, 418, 419, 453 were collected at Otis Chalk Quarry 3, and TMM 31185 11, 38 were collected at Otis Chalk Quarry 3A.

P. angustifrons was first described and named by Oskar Kuhn in 1936 as a species of Francosuchus. P. angustifrons is known exclusively from the holotype BSPG 1931 X 502 a partial skull lacking the rostrum and mandibles. It was collected at Ebrach Quarry, bed number 9 of Bavaria, southern Germany, from the late Carnian aged Blasensandstein Member of the Hassberge Formation. Hunt and Lucas (1991) mistakenly referred to F. angustifrons as Ebrachosuchus angustifrons, and considered it and the other two Francosuchus species, F. broilii and F. latus, to be synonyms of Paleorhinus neukami. "Z." arenaceus was suggested to represent the oldest reliably dated phytosaur, and was reassigned to various phytosaur species over the years, including Belodon, Mystriosuchus and Phytosaurus. Although Hungerbühler (2001) redescribed "Z." arenaceus as not belonging to Phytosauria and referred it to Archosauria incertae sedis, Dzik & Sulej (2007) noted that its holotype "does not differ significantly from corresponding parts of the juvenile Krasiejów Paleorhinus, which is clearly a phytosaur". Furthermore, as the Feuerbacher Heide Schilfsandstein, from which "Z." arenaceus was collected, and Krasiejów share species of Metoposaurus, it might be possible that they also share the same species of phytosaur. Even though they agreed that due to the very fragmentary nature of "Z." arenaceus holotype the Krasiejów Paleorhinus can't be referred to it, they tentatively used the name Paleorhinus cf. arenaceus for the Krasiejów Paleorhinus. and Wastphal (1976) referred these species, as well as, E. neukami and P. angustifrons to Paleorhinus subgenus Francosuchus, while Chatterjee (1978) placed the four species in Francosuchus in a different subfamily. Hunt and Lucas (1991) considered these species to be synonymous with Paleorhinus neukami. now referable to Tetrapoda incertae sedis. "Paleorhinus" parvus Mehl, 1928 Hunt and Lucas (1991) considered this species to be synonymous with P. bransoni,
Parasuchus hislopi Lydekker, 1885 P. hislopi was based on a chimeric syntype material a rhynchosaurian basicranium mixed with phytosaurian partial snout, scutes and some teeth. Friedrich von Huene (1940) identified the basicranium as belonging to Paradapedon huxleyi (now known as Hyperodapedon huxleyi), thus he assigned the phytosaurian material to a newly named species "aff." Brachysuchus maleriensis. Later, Edwin Harris Colbert (1958) designated all the Indian parasuchian material as Phytosaurus maleriensis. Gregory (1962) accepted this proposal. Sankar Chatterjee (1978), who described many complete remains of the Indian parasuchian, showed that it is not assignable either to Brachysuchus (which is closely related to or synonymous with Angistorhinus), or to Phytosaurus (a doubtful name, probably the senior synonym of Nicrosaurus). He noted that since the rhynchosaur basicranium is neither the holotype of P. hislopi, nor the lectotype of Paradapedon huxleyi, the suppression of P. hislopi should be avoided. Nevertheless, Hunt and Lucas (1991) considered the species to be a nomen dubium, and provisionally created the combination Paleorhinus hislopi for the diagnosable phytosaur specimens from the Lower Maleri Formation, stating that the Indian species can be distinguished from other Paleorhinus species. As a result, most subsequent studies referred all Paleorhinus species to Parasuchus in accordance with the rules of the ICZN, while others kept referring P. hislopi to Paleorhinus. In light of the complex taxonomic history of Paleorhinus, studies as of 2013 considered the synonymy between the genera to be premature. Promystriosuchus ehlersi Case, 1922 Gregory (1962) and Hunt and Lucas (1991) referred this taxon to Paleorhinus on the genus level, and considered it to be a nomen dubium on the species level, due to the poor preservation of it holotype and only known specimen. Stocker and Butler (2013) suggested that P. ehlersi may not be referable to Paleorhinus and referred it to Phytosauria incertae sedis.

The following cladogram, from Kammerer et al., 2016, shows the relationships of P. bransoni, P. angustifrons, and "P." sawini to other phytosaurs. The authors placed P. bransoni and P. angustifrons into the genus Parasuchus, owing to their close relationship with Parasuchus hislopi.