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Geographic sketch map (A) and palaeogeographical location (B) of the fossil locality in Junggar Basin, Xinjiang, China. A, Geographical position and extent of present-day Junggar Basin; B, Palaeogeographical location of Junggar Basin in the Late Triassic and the localities of contemporaneous records of Saurichthys from freshwater sediments. 1. Saurichthys sui sp. nov., Xinjiang, China; 2. Saurichthys orientalis, Madygen, Kyrgyzstan (Kogan et al. 2009); 3. Saurichthys huanshenensis (with questionable age), Shaanxi, China (Zhou and Liu 1957); 4. Saurichthys? sp., Greenland (Jenkins et al. 1994); 5. Saurichthys sp., Arizona, USA (Kligman et al. 2017).
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The iconic saurichthyid fishes (‘lizard fish’) are specialised predators in the aquatic realm of Early Mesozoic era. After a rapid diversification in the Middle Triassic, they seemingly shrank their geographical distribution from a global pattern to that mainly confined to Euramerican region and exhibited increasing rarity in the freshwater environ...
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... the information is limited of the top predators of the freshwater realms, e.g., the large predatory fish from those fossil assemblages, which are important indicators of the presence of complex food webs ( Voigt et al. 2017;Zheng et al. 2018;Zhao et al. 2020). Here, we report the first record of the typically predatory fish Saurichthys from the Late Triassic of western Junggar Basin (Figure 1), which also represents the largest fish known so far from that basin throughout the Triassic. On the basis of this discovery, we evaluate the phylogenetic potential of the new material for its family and highlight its palaeoecological and palaeobio-geographical implications in the context of the recovery of the freshwater ecosystem in the aftermath of the end-Permian mass extinction. ...
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... studied material was collected from Shendigou outcrop in Junggar Basin, northwest to Kelamayi City, Xinjiang Uygur Autonomous Region, China ( Figure 1A) during the Palaeontological Expedition to Xinjiang in the 1980s, and was deposited in Institute of Vertebrate Palaeontology and Palaeoanthropology, Chinese Academy of Sciences (IVPP, CAS). The fish-bearing layer belongs to the lower part of the Baijiantan Formation, which consists mainly of greyish white and yellow fine mudstone and siltstone ( Zheng et al. 2017). ...
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... its geographical position between the Mongol-Okhotsk Ocean and PalaeoTethys during the Late Triassic (Scotese 2014; Xiao et al. 2015) (Figure 1B), the Shendigou fossil site of the Junggar basin provides some biogeographical link between the central Asian lake ecosystem, e.g., the Madygen Biota in central Asia ( Voigt et al. 2017) and that of East Asia, e.g., the Tongchuang and Hengshan Biotas of Ordos Basin in North China ( Zhou and Liu 1957;Zheng et al. 2017Zheng et al. , 2018Zhao et al. 2020), which have all yielded fossils of Saurichthys ( Zhou and Liu 1957;Kogan et al. 2009; personal collections from Tongchuang Biota). And indeed, the majority of these Saurichthys share extensively ornamented flank scales (mid-lateral scales) (see comparison above). ...
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Citations
... Although the study of these fishes is in its earliest stages, it is already clear that multiple genera, and plausibly higher taxa, are represented by the material in layer HJG-44. It is unclear how the Haojiagou Formation fish assemblage relates to the recently decribed material from the Baijiantan Formation of the northwestern Junggar Basin (Fang and Wu 2022) in which the predatory palaeonisciform Saurichthys plays a prominant role. The latter taxon is now known from several fresh water sequences of Triassic age including the Late Triassic Chinle Formation of the US southwest (Kligman et al. 2017) and the ?Middle Triassic Madygen Formation of Kyrgyzstan, Central Asia (Kogan et al. 2009). ...
... The absence of an enameloid cap ( Fig. 9; SI Movie 2) rules out most actinopterygians, as this features may be a apomorphy for the clade containing all but the most basal ray-finned fishes (Friedman and Brazeau 2010). This rules out the Triassic predatory fishes such as Saurichthys [present in the Triassic Baijiantan Formation of Junggar Basin (Fang and Wu 2022)] and Birgeria that have superficially similar ridging on their tooth crowns, although they also have well developed plicidentine. Based on the superficial external morphology, PEO initially thought that the tooth resembled temnospondyl teeth known from the Permian to the Cretaceous, particularly those of Mastodosaurus, Gerrothorax, and Plagiosternum (Preushoft et al. 1991;Hagdorn and Mutter 2011;Schoch et al. 2018). ...
... The fish material described herein from the Haojiagou and Sangonghe formations, along with the recent description of Saurichthys and associated material from the Late Triassic Baijiantan Formation in the northwest Junggar Basin (Fang and Wu 2022), indicates that diligent search will result in entirely new assemblages from the palaeo-Arctic that will add substantially to our understanding of the still poorly resolved, ichthyological Triassic-Jurassic transition. ...
Vertebrate assemblages from the Junggar Basin in Xinjiang, China are the only ones known from palaeoarctic continental strata of Late Triassic and Early Jurassic age. Here we present a preliminary description of these new assemblages, focusing on the underappreciated Arctic palaeolatitude and winter freezing of this coal-bearing sequence. Mostly collected during NIGPAS-led stratigraphic studies in the 2016-2017 field seasons, new assemblages include: 1) small to large, sculptured palaeonisciform cranial elements and scales, small associated palaeonisciforms, a sauropterygian tooth, large-dinosaur bioturbation, and additional as yet unidentified small vertebrate bones from the Haojiagou Formation (?late Norian-Rhaetian); 2) a medium-sized brontozoid dinosaur footprint and a previously described possible Anomoepus track from the Badaowan Formation (Hettangian-?Pliensbachian); and 3) a hybodont shark egg case of the form taxon Palaeoxyris (only the third reported from the Early Jurassic of China), numerous associated and fragmentary small palaeonisciform remains including one partial skull and several small skeletons, and another possible Anomoepus track and associated dinoturbation from the Sangonghe Formation (?Pliensbachian-Toarcian). A possible ash associated with the aforementioned lower Sangonghe fish skull has produced a LA-ICP-MS age of roughly 186 Ma, consistent with a Pliensbachian age. We are optimistic that there will be many additional discoveries in early Mesozoic strata of the Junggar Basin, the importance of which for understanding Earth system processes cannot be overemphasised.
Supplementary material at https://doi.org/10.6084/m9.figshare.c.6729761
