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1042


Journal of Paleontology 91(5):1025–1046


further inferred too high sea surface temperatures (~38°C, possibly over 40°C), because the presence of fishes in the USA and China suggests that a 36°C physiological limit was not crossed (Motani and Wainwright, 2015).


Spathian Osteichthyes


Of interest is the presence of vertebrate fossils in Spathian strata in the western USA. The Spathian had a duration of ~3 myr, therefore longer than the first three stages of the Early Triassic combined (~2 myr; Ovtcharova et al., 2006, 2015; Galfetti et al., 2007a; Fig. 8). However, only a few, well-dated Spathian sites yield articulated osteichthyan fossils (Romano et al., 2016a). Apart from the new material from Crittenden Springs


(NMMNH P-77357, PIMUZ A/I 4641), articulated actino- pterygian remains (a perleidid and a saurichthyid) have been described from Spathian deposits of Anhui Province, China (Sun et al., 2013; Tintori et al., 2014b). In addition, largely complete marine osteichthyan fossils have also been docu- mented from beds close to the Smithian-Spathian boundary at localities in Anhui, Hubei and Jiangsu provinces, China (e.g., Tong et al., 2006 and references therein). A saurichthyid (Saurichthys elongatus?) with a short postorbital skull portion was found slightly above the Smithian ‘Fischniveau’ of Spitsbergen, thus being of possible Spathian age (Stensiö, 1925; Kogan and Romano, 2016b). Two saurichthyids and a colobo- dontid were found in the Gogolin beds of Upper Silesia, Poland, whose age is close to the Spathian-Anisian boundary (e.g., Eck, 1865; Frech, 1903–1908; Nawrocki and Szulc, 2000; Szulc and Becker, 2007). Aldinger (1931) mentioned undescribed actinistian material from Gogolin. Marine and freshwater osteichthyan remains of presumable Spathian age have been described from localities in Canada, Russia, Kazakhstan, northern China, and South Africa (e.g., Jubb and Gardiner, 1975; Minikh, 1981; Mutter and Neuman, 2006), although often with limited biochronostratigraphic constraints. Besides, there are several Spathian occurrences of isolated fish remains (e.g., Stensiö, 1921; Mutter and Rieber, 2005; Kogan and Romano, 2016b; Brayard et al., 2017), but such material often provides little taxonomic information. Griesbachian–Smithian fishes differ notably from post-


Spathian ones. Earliest Triassic sites are characterized by cosmo- politan taxa, whereas Middle Triassic assemblages comprise many endemic taxa, with a distinct neopterygian component (Tintori et al., 2014a; Romano et al., 2016a). This suggests an ichthyofaunal turnover either during the Spathian or in conjunc- tionwith the end-Smithian event. This extinction event decimated nektopelagic clades such as ammonoids and conodonts (Galfetti et al., 2007b; Orchard, 2007) and saw the replacement of trema- tosauroid ‘amphibians’ by reptiles among the marine tetrapod apex predators (Scheyer et al., 2014).However, the impacts of the end-Smithian event on fishes remain elusive, particularly with regard to the timing of the radiation of the ‘Triassic Middle Fish Fauna’ of Tintori et al. (2014a). The sparse Spathian actinopter- ygians known thus far show more affinities withMiddle Triassic taxa than with Griesbachian–Smithian ones (Sun et al., 2013; Tintori et al., 2014b). There is a need for more research on Spathian Osteichthyes, emphasizing the importance of the


discovery of articulated osteichthyans in the Spathian of Nevada and Idaho (Brayard et al., 2017; this study).


Conclusions


The presented material from three new sites in Elko County (Nevada, USA) notably improves the fossil record of Early Triassic fishes from the western USA. Although Early Triassic fish remains occur in several places in the United States, most of them have not been studied. We introduce a new Spathian fish occurrence. Spathian Osteichthyans are preserved in several sites in the western USA and their study may provide vital clues concerning the post-Paleozoic evolution of fishes. The Smithian material studied here includes two large-


sized individuals of the predatory actinopterygian Birgeria, providing the first fossil evidence that birgeriids expanded their distribution into the western USA Sea, even during the Smithian thermal maximum (Goudemand et al., 2013; Romano et al., 2013). One specimen can be ascribed to a new species, Birgeria americana n. sp., which is characterized by three rows of teeth on the maxilla and dentary, and a less reduced oper- culogular series compared to other taxa. We further describe material of the ambush predator Saurichthys that, together with other late Smithian occurrences in Idaho (PIMUZ A/I 3900, PIMUZ A/I 4621, NMMNH P-77359), suggests that this taxon was relatively common in the western USA basin. The presented fishes from low paleolatitudes, along with other Smithian vertebrate occurrences in the United States and South China (Tong et al., 2006), invalidate the alleged ‘equatorial vertebrate eclipse’ of Sun et al. (2012). These low-latitude occurrences imply that a 36°C temperature tolerance was not permanently exceeded during the Smithian thermal maximum (Motani and Wainwright, 2015). The presence of the acti- nopterygian top predators Birgeria and Saurichthys also con- tradicts anew the claim of missing apex predators and truncated food chains during the Early Triassic made by Chen and Benton (2012).


Acknowledgments


We appreciate information from and insightful discussions with T. Argyriou, M. Leu, D. Ware, T. Brühwiler, M. Brosse, C. Klug, M. Hautmann, W. Brinkmann (all PIMUZ), I. Kogan (Technische Universität Bergakademie Freiberg, Germany), P. Skrzycki and R. Skrzycka (Krakow, Poland), A. Brayard (Université de Bourgogne, Dijon, France), R. Hofmann (Museum für Naturkunde Berlin), and A. Trintori (MPUM). E.E. Maxwell (Staatliches Museum für Naturkunde Stuttgart, Germany) and the editor are thanked for comments that improved this paper. I. Kogan and A. Tintori are also thanked for photographs. M. Leu, C. Kolb, and F. Blattmann (all PIMUZ) are thanked for lab support. CR thanksM.Hebeisen, R. Roth, and T. Argyriou for advice during preparation of fossils, and M. Véran, G. Clément (both MNHN.F), and J.O. Ebbestad (PMU) for help during collection visits. Fossils were collected under BLM permit number N-92672 and we thank B. Hockett (Bureau of Land Management Nevada) for swift administrative processing.Wedeeply acknowledge past and present support by


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