The Early Triassic Jurong fish fauna, South China: Age, anatomy, taphonomy, and global correlation

Abstract

As the higher trophic guilds in marine food chains, top predators such as larger fishes and reptiles are important indicators that a marine ecosystem has recovered following a crisis. Early Triassic marine fishes and reptiles therefore are key proxies in reconstructing the ecosystem recovery process after the end-Permian mass extinction. In South China, the Early Triassic Jurong fish fauna is the earliest marine vertebrate assemblage in the recovery period. It is constrained as mid-late Smithian in age based on both conodont biostratigraphy and carbon isotopic correlations. The Jurong fishes are all preserved in calcareous nodules embedded in black shale of the Lower Triassic Lower Qinglong Formation, and the fauna comprises at least three genera of Paraseminotidae and Perleididae. The phosphatic fish bodies often show exceptionally preserved interior structures, including network structures of possible organ walls and cartilages. Microanalysis reveals the well-preserved micro-structures (i.e. collagen layers) of teleost scales and fish fins. Abundant small pyrite framboids, 2−5 μm in diameter, are detected from the nodules and fish body surfaces, indicating a calm, euxinic burial environment. Coccoid-like microspheroids are also very abundant in the host rocks and near the fish fossil surfaces, implying that microbes may have participated in the burial process of the fishes. Taphonomic analysis uncovers the four-step formation process of the fish nodules. (1) Fishes lived in the oxic seawater in the upper ocean, and (2) their bodies sank to the anoxic seabed after death, with the body surface being wrapped by bacteria. (3) Microbial biofilms sealed body surfaces to prevent or delay the decay of the fleshy body. The decomposition of the body cavity and interior organs produced some CO 2 and H 2 S gases. The former formed bicarbonate ions in seawater and attracted calcium ions to facilitate the precipitation of calcium carbonate, while the H 2 S combined with iron ions in seawater to form pyrite framboids. (4) The fish nodule gradually grew by precipitation of calcium carbonate in layers and embedding with pyrite framboids, and later the fish fossil nodule was compacted during diagenesis. Global faunal correlations indicate that the Jurong fishes are closely related to the Early Triassic fish faunas from Chaohu, Anhui Province and Madagascar.

Exceptional fossil assemblages confirm the existence of complex Early Triassic ecosystems during the early Spathian

“…Aside from the Paris Biota, the known record of diversified marine assemblages from the Early Triassic, and especially from the Smithian-Spathian interval, is particularly poor worldwide. It is limited either to a few essentially shallow benthic communities [22][23][24][25][26] or to a few nekton-dominated communities, i.e., fish and marine reptiles [27][28][29][30][31][32] . This apparent absence of co-occurring complex benthic and nektonic communities has often been interpreted as the result of a relatively slow and trophic step-by-step recovery of marine ecosystems 8,14,33 .…”

An expanded Smithian–Spathian (Lower Triassic) boundary from a reefal build‐up record in Oman: implications for conodont taxonomy, high‐resolution biochronology and the carbon isotope record

“…2019; Qiu et al . 2019). Hence, its range was here reduced up to RT22a in the Radio Tower section and up to WBK05/14 in the Wadi Bani Khalid section.…”

“…3.4, 3.12 (only).2019 Scythogondolella milleri (Müller); Qiu et al ., p. 38, fig. 5.4.2019 Scythogondolella lachryformis (Müller); Qiu et al ., p. 38, fig. 5.1, 5.3.2020 Scythogondolella milleri (Müller); Liu et al ., p. 11, pl.…”

“…3.3, 3.10, 3.11.2019 Scythogondolella lachryformis (Müller); Chen et al ., fig. 3.4, 3.12 (only).2019 Scythogondolella milleri (Müller); Qiu et al ., p. 38, fig. 5.4.2019 Scythogondolella lachryformis (Müller); Qiu et al ., p. 38, fig.…”

A Unitary Association-based conodont biozonation of the Smithian–Spathian boundary (Early Triassic) and associated biotic crisis from South China

“…Jiang et al, 2007 ), North Pingdingshan (Zhao et al, 2007 ) and West Pingdingshan (Liang et al, 2011 ). Other conodont-rich sections from the northern part of the South China Block include Huangzhishan (Chen et al, 2008 ), Chaotian (Ji et al, 2011 ), Shangsi (Jiang et al, 2011 ), Daxiakou (Zhao et al, 2013 ) Jianshi (Lyu et al, 2019 ), Ganxi (Lyu et al, 2019 ), South Majiashan (Zhao et al, 2007 ), Qingshan (Liu et al, 2019 ; Qiu et al, 2019 ), Longtan (Liu et al, 2019 ) and Yiwagou (Li et al, 2019 ).…”