Sauroctonus

Nearly complete remains listed from Tanzania have been attributed to a second species, S. parringtoni, which would make this genus the only known gorgonopsian to have lived in both Africa and Russia. However, it has been proven that this assimilation is mistaken, as it is mainly based on superficial resemblances, leaving the latter awaiting a more in-depth study to determine its relationships with other representatives of the group. Moreover, studies published post-2018 prove that S. progressus belongs to a grouping of Russian gorgonopsians, placed alongside the genera Suchogorgon, Pravoslavlevia and Inostrancevia, due to some shared cranial characteristics.

Research history

S. progressus

In 1938, the Soviet paleontologist Alexandra Paulinovna Hartmann-Weinberg described some fossil remains of gorgonopsians having been discovered in Tatarstan, in the present-day Russia. One of the fossils described in his paper is an incomplete but well-preserved skull, cataloged PIN 156/5. Hartmann-Weinberg considers this specimen to belong to a new species of the South African genus Arctognathus, designating it as Arctognathus progressus. The specific epithet progressus is incorrectly named due to its supposed morphological closeness to cynodonts, which have a large number of progressive and more mammal-like features than other gorgonopsians. It quickly became apparent that the species is no more related to these same cynodonts than the other gorgonopsians, and in 1940, only two years after the publication of his article, one of Hartmann-Weinberg's employees, the reputed Ivan Yefremov reclassified the taxon as a new species of the Russian genus Inostrancevia, renaming it as Inostrancevia progressus. In 1955, after the analysis of the material, Alexey Bystrow proposed a separate genus for the species, which he named Sauroctonus, and designates the specimen PIN 156/5 as the lectotype of the taxon a proposal that will be quickly recognized later. The genus name Sauroctonus comes from the Ancient Greek σαῦρος (saûros, "lizard") and κτόνος / (któnos, "murderer" or "killer"), to literally give "lizard killer", in reference to its carnivorous diet. All known specimens are from the type locality where the first known skull was discovered. Among these fossils remains figures PIN 156/6, a specimen containing a crushed skull, some anterior part of the postcranial skeleton and numerous isolated bones.

S.? parringtoni

All confirmed remains of Sauroctonus are only recorded in Russian territory and belong to the species S. progressus, mainly represented by cranial material. In 1950, a relatively complete skeleton, discovered in the Usili Formation in Tanzania, cataloged GPIT/RE/7113, was described by the German paleontologist Friedrich von Huene as a representative of the species Scymnognathus parringtoni, being named in honor of Francis Rex Parrington. In 1970, the skeleton was reidentified by the French paleontologist Denise Sigogneau-Russell as a specimen of Aelurognathus, being renamed Aelurognathus parringtoni. It is from 2007 that the paleontologist Eva V. I. Gebauer reclassifies it as an African representative of the genus Sauroctonus, a claim that she would confirm again in 2014. However, this affiliation is formally rejected in 2018, as new classifications based on cranial anatomical traits show that derived gorgonopsians are separated into two clade of Russian and African origin, leaving GPIT/RE/7113 as an incertae sedis within the latter group.

Other specimens have been attributed to this species, but no concrete affiliation has been worked out to date. For example, the well-preserved skull cataloged SAM-PK-K10034, mentioned briefly in a study concerning the nocturnal vision of non-mammalian synapsids, is referred to as S. cf. parringtoni.