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Revision of the southern Andean genus Sadocus Sorensen, 1886 (Opiliones, Gonyleptidae, Pachylinae).

ABSTRACT: Species of the genus Sadocus Sørensen, 1886 are conspicuous gonyleptids that occur in Chile and Argentina. Here, the genus is revised for the first time and the cladistic analysis based on morphological characters does not corroborate its monophyly unless a phylogenetically unrelated species is excluded (explained further on). A new classification is proposed for the seven species left in the genus and considered valid, of the 13 nominal species previously recognized. Two out of the seven valid species are considered as species inquirendae: Sadocus allermayeri (Mello-Leitão, 1945) [= Carampangue allermayeri Mello-Leitão, 1945] and Sadocus nigronotatus (Mello-Leitão, 1943) [= Carampangue nigronotatum Mello-Leitão, 1943]. The following synonymies are proposed: Sadocus bicornis (Gervais, 1849) [original combination = Gonyleptes bicornis Gervais, 1849] is a junior synonym of Sadocus asperatus (Gervais, 1847) [= Gonyleptes asperatus Gervais, 1847]; Sadocus conspicillatus Roewer, 1913, Sadocus exceptionalis (Mello-Leitão, 1946) [= Araucanoleptes exceptionalis Mello-Leitão, 1946] and Sadocus guttatus Sørensen, 1902 are junior synonyms of the valid name Sadocus polyacanthus (Gervais, 1847) [= Gonyleptes polyacanthus Gervais, 1847]; and Sadocus calcar (Roewer, 1913) [= Lycomedes calcar Roewer, 1913] is a junior synonym of the valid name Gonyleptes horridus Kirby, 1819. Sadocus brasiliensis Soares & Soares, 1949 is not congeneric with Argentinean/Chilean species of the genus according to the cladistic analysis and is here synonymized with Discocyrtus catharinensis (Mello-Leitão, 1923 [= Sadocus catharinensis Mello-Leitão, 1923]).

SUBMITTER: Pessoa-Silva M

PROVIDER: S-EPMC8007552 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The crocodylian fossil record from the Cenozoic of Australasia is notable for its rich taxonomic diversity, and is primarily represented by members of the clade Mekosuchinae. Reports of crocodylian fossils from Australia date back to the late nineteenth century. In 1886, Charles Walter de Vis proposed the name Pallimnarchus pollens for crocodylian fossils from southeast Queensland-the first binomen given to an extinct crocodylian taxon from Australia. Pallimnarchus has come to be regarded as a large, broad-snouted crocodylian from Australia's Plio-Pleistocene, and numerous specimens, few of which are sufficiently complete, have been assigned to it by several authors throughout the twentieth century. In the late 1990s, the genus was expanded to include a second species, Pallimnarchus gracilis. Unfortunately, the original syntype series described as Pallimnarchus pollens is very fragmentary and derives from more than one taxon, while a large part of the subsequently selected lectotype specimen is missing. Because descriptions and illustrations of the complete lectotype do not reveal any autapomorphic features, we propose that Pallimnarchus pollens should be regarded as a nomen dubium. Following this decision, the fossil material previously referred to Pallimnarchus is of uncertain taxonomic placement. A partial skull, formerly assigned to Pallimnarchus pollens and known as 'Geoff Vincent's specimen', possesses many features of diagnostic value and is therefore used as basis to erect a new genus and species-Paludirex vincenti gen. et sp. nov. A comprehensive description is given for the osteology of 'Geoff Vincent's specimen' as well as aspects of its palaeoneurology, the latter being a first for an extinct Australian crocodyliform. The newly named genus is characterized by a unique combination of premaxillary features such as a distinctive arching of the anterior alveolar processes of the premaxillae, a peculiar arrangement of the first two premaxillary alveoli and a large size disparity between the 3rd and 4th premaxillary alveoli. These features presently allow formal recognition of two species within the genus, Paludirex vincenti and Paludirex gracilis comb. nov., with the former having comparatively more robust rostral proportions than the latter. The Paludirex vincenti holotype comes from the Pliocene Chinchilla Sand of the Darling Downs, south-eastern Queensland, whereas the material assigned to Paludirex gracilis is from the Pleistocene of Terrace Site Local Fauna, Riversleigh, northwest Queensland. Phylogenetic analyses recover Paludirex vincenti as a mekosuchine, although further cladistic assessments are needed to better understand the relationships within the clade.

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Revision of the southern Andean genus Sadocus Sorensen, 1886 (Opiliones, Gonyleptidae, Pachylinae).

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