DOI: 10.15468/cqp6hy
title: The westernmost occurrence of Gnathorhiza in the Triassic, with a discussion of the stratigraphic and palaeogeographic distribution of the genus

description: This dataset contains the digitized treatments in Plazi based on the original journal article Skrzycki, P. (2016): The westernmost occurrence of Gnathorhiza in the Triassic, with a discussion of the stratigraphic and palaeogeographic distribution of the genus. Fossil Record 19 (1): 17-29, DOI: 10.5194/fr-19-17-2016, URL: http://dx.doi.org/10.5194/fr-19-17-2016Abstract. The paper refines the taxonomic assignment of the only representative of the dipnoan genus Gnathorhiza from the Lower Triassic of Poland. It is assigned here to Gnathorhiza otschevi on the basis of morphological and biometrical similarity with the tooth plates from coeval strata of the European part of Russia. The material is comprised solely of tooth plates, both the upper and the lower ones. It comes from karst deposits of the Czatkowice 1 locality (southern Poland) dated to late Olenekian, Lower Triassic. The presence of G. otschevi in southern Poland widens its palaeobiogeographic Triassic record by more than 2000 km to the west. Czatkowice 1 locality is the only known occurrence of gnathorhizids within the Germanic Basin. G. otschevi from Czatkowice 1 shows petrodentine in the tooth plate. Its presence is proved for the first time in a Triassic gnathorhizid. Gnathorhiza was most widely distributed during the Permian and restricted to Europe in the Triassic. Tooth plates of both Early Triassic European and Late Permian Brazilian gnathorhizids are more similar to each other than to Permo-Carboniferous American ones.1 IntroductionGnathorhiza Cope, 1883 is so far the only dipnoan genus known from both Palaeozoic and Mesozoic sediments. This genus is of great interest due to its supposed close affinities with lepidosirenids (Romer and Smith, 1934) and aestivation capability (Campbell and Barwick, 1988). Gnathorhiza is known from the Upper Carboniferous to Lower Triassic strata of various localities around the world (Schultze, 1992, 2004). The Late Carboniferous and Early Permian fossils of this genus were found at different localities in the USA (Dalquest et al., 1989), Germany (Boy and Schindler, 2000) and Oman (Schultze et al., 2008). In the Late Permian, Gnathorhiza occurred in Russia (Minikh, 1989; Minikh and Minikh, 2006) and Brazil (Toledo and Bertini, 2005). The youngest fossils of Gnathorhiza are known from the Lower Triassic freshwater sediments of Russia (Minikh, 1977, 2000; Minikh and Minikh, 2006; Newell et al., 2010) and Poland (Borsuk-Białynicka et al., 2003).The Polish findings of Gnathorhiza come from karst deposits of the Czatkowice 1 locality situated near Cracow, southern Poland. The sediments were deposited just before the Röt transgression (Paszkowski, 2009), and their age is estimated at early late Olenekian (Shishkin and Sulej, 2009). The dipnoan material comprising of four tooth plates (Fig. 1) was found together with remains of other fishes, procolophonids, temnospondyls, stem frogs, archosauriforms, lepidosauromorphs and kuehneosaurids (Borsuk-Białynicka et al., 1999). The tooth plates have been so far assigned to Gnathorhiza sp. (Borsuk-Białynicka et al., 2003). The present study provides their detailed morphological description and their specific assignment. The first evidence of the presence of petrodentine in a Triassic gnathorhizid is provided here for Gnathorhiza from Poland.Czatkowice 1 in southern Poland is the westernmost occurrence of Gnathorhiza known so far from the Triassic. The tooth plates belong to a species known until now only from uppermost Permian and Lower Triassic sediments of Russia (Minikh, 1977; Minikh and Minikh, 1997, 2006). The Polish material and tooth plates of other known members of Gnathorhiza are compared. This brings new insight to the systematic affinities of the genus members. The geographic and stratigraphic distribution of Gnathorhiza was never subject to a broad study, and therefore the present revision may serve as a useful background for further studies.