Marine Early Triassic Actinopterygii from the Candelaria Hills (Esmeralda County, Nevada, USA)

Abstract

A new locality for low-latitudinal, Early Triassic fishes was discovered in the Candelaria Hills, southwestern Nevada (USA). The fossils are derived from the lower Candelaria Formation, which was deposited during the middle–late Dienerian (late Induan), ca. 500 ka after the Permian-Triassic boundary mass extinction event. The articulated and disarticulated Osteichthyes (bony fishes), encompassing both Actinistia (coelacanths) and Actinopterygii (ray-fins), are preserved in large, silicified concretions that also contain rare coprolites. We describe the first actinopterygians from the Candelaria Hills. The specimens are referred toPteronisculus nevadanusnew species (Turseoidae?),Ardoreosomus occidentalisnew genus new species (Ptycholepidae), the stem neopterygianCandelarialepis argentusnew genus new species (Parasemionotidae), and Actinopterygii indet. representing additional taxa.Ardoreosomusn. gen. resembles other ptycholepids, but differs in its more angulate hyomandibula and lack of an elongate opercular process.Candelarialepisn. gen. is one of the largest parasemionotids, distinguished by its bipartite preopercle and scale ornamentation. Presented new species belong to genera (Pteronisculus) or families (Ptycholepidae, Parasemionotidae) that radiated globally after the mass extinction, thus underlining the striking similarities between Early Triassic (pre-Spathian) osteichthyan assemblages. The current data suggest that the diversity of low-latitudinal, Early Triassic bony fishes may have been greater than indicated thus far by the fossil record, probably due to sampling or taphonomic failure. All 24 fossils from the Candelaria Hills represent mid-sized or large osteichthyans, confirming the obvious absence of very small species (≤ 10 cm adult body length) in the beginning of the Mesozoic Era—even in low latitudes.UUID:http://zoobank.org/6a66ac96-d6b7-4617-94db-5a93cdb14215

The marine conservation deposits of Monte San Giorgio (Switzerland, Italy): the prototype of Triassic black shale Lagerstätten

“…dark sediment, complete skeletons, poor in benthos, rich in clay) have been recognized in many other places. Examples for such deposits have been documented from Europe (eastern Switzerland, Ducan: Furrer, 2004 ; western Austria: Zapfe & König, 1980 ; Wachtler & Perner, 2018 ; Italy: Stefani et al, 1991 ; Slovakia: Čerňanský et al, 2018 ; Slovenia: Hitij et al, 2010 ), Asia (Spiti, India: Romano et al, 2016 ; Myanmar: San et al, 2019 ), and North America (Idaho: Brayard et al, 2017 ; Nevada: Romano et al, 2019 ).…”

A Hiatus Obscures the Early Evolution of Modern Lineages of Bony Fishes

“…Two new localities yielding articulated Dienerian osteichthyan fishes were recently discovered in the Spiti subdistrict (Himachal Pradesh, India; Romano et al, 2016b) and in the Candelaria Hills (southwestern Nevada, United States; Romano et al, 2019). From Spiti, Saurichthys, a parasemionotid, an actinistian and additional, indeterminable actinopterygian remains have been described.…”

“…Neuman and Mutter 2005), Ptycholepidae (Acrorhabdus, Ardoreosomus, Boreosomus, Ptycholepis; Griesbachian-Jurassic; e.g. Romano et al, 2019), Birgeria (Triassic; e.g. Romano et al, 2017), Bobasatrania (Griesbachian-Illyrian; e.g.…”

A Portrait of a Young Fish: Redescription ofPteronisculus gunnari(Nielsen, 1942) from a juvenile specimen from the Early Triassic of East Greenland, with implications for ontogenetic development in early actinopterygians

“…A few years later, Glaucolepis (Stensiö, 1921), initially erected to contain incomplete fossil fish material from the Early Triassic of Svalbard, was synonymized with Pteronisculus (White & Moy-Thomas, 1940). The temporal and geographical range of this genus grew with successive descriptions of new species from the Early Triassic of east Greenland (Nielsen, 1942), north-western Madagascar (Lehman, 1952), Nevada, USA (Romano et al, 2019) and the Middle Triassic of Luoping, China (Ren & Xu, 2021;Xu, Shen, et al, 2014). Fragmentary material has also been referred to the genus from the late Permian of South Africa (Brian George Gardiner & Jubb, 1975) and the Early Triassic of Alberta and British Columbia, Canada (Lambe, 1916;Schaeffer & Mangus, 1976).…”

“…Although 13 species of Pteronisculus are described in the literature (plus two to three more dubious attributions; see e.g., Brian George Gardiner & Jubb, 1975;Romano et al, 2019;Schaeffer & Mangus, 1976), only Ren & Xu (2021) and Caron et al (2023) have included more than one taxon in a phylogenetic analyses, and the latter only consider neurocranial characters. In large part, this can be attributed to the uneven amount of information available for each taxon.…”