Boreal earliest Triassic biotas elucidate globally depauperate hard substrate communities after the end-Permian mass extinction.

Michał Zatoń,Grzegorz Niedźwiedzki,Henning Blom,Benjamin P. Kear

doi:10.1038/srep36345

Michał Zatoń, Grzegorz Niedźwiedzki + Show 2 more

Open Access

https://doi.org/10.1038/srep36345

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Journal: Scientific Reports	Publication Date: Nov 8, 2016
Citations: 21	License type: CC BY 4.0

Affiliation: University of Silesia, Uppsala University

Abstract

The end-Permian mass extinction constituted the most devastating biotic crisis of the Phanerozoic. Its aftermath was characterized by harsh marine conditions incorporating volcanically induced oceanic warming, widespread anoxia and acidification. Bio-productivity accordingly experienced marked fluctuations. In particular, low palaeolatitude hard substrate communities from shallow seas fringing Western Pangaea and the Tethyan Realm were extremely impoverished, being dominated by monogeneric colonies of filter-feeding microconchid tubeworms. Here we present the first equivalent field data for Boreal hard substrate assemblages from the earliest Triassic (Induan) of East Greenland. This region bordered a discrete bio-realm situated at mid-high palaeolatitude (>30°N). Nevertheless, hard substrate biotas were compositionally identical to those from elsewhere, with microconchids encrusting Claraia bivalves and algal buildups on the sea floor. Biostratigraphical correlation further shows that Boreal microconchids underwent progressive tube modification and unique taxic diversification concordant with changing habitats over time. We interpret this as a post-extinction recovery and adaptive radiation sequence that mirrored coeval subequatorial faunas, and thus confirms hard substrate ecosystem depletion as a hallmark of the earliest Triassic interval globally.

Highlights

The end-Permian mass extinction constituted the most devastating biotic crisis of the Phanerozoic
The prevalence of microconchids in offshore and lower shore-face settings bordering Western Pangaea provided the original basis for positing global impoverishment of hard substrate marine ecosystems during the earliest Triassic[33]
The only other hard substrate faunal element in our samples was the Entobia-like ichnite, which equates to the possible phoronid boring Talpina from Western Pangaea[33]; these traces are extremely rare suggesting that endoliths, when present, constituted a minute component of the entire biotic assemblage

Summary

Introduction

The end-Permian mass extinction constituted the most devastating biotic crisis of the Phanerozoic. Biostratigraphical correlation further shows that Boreal microconchids underwent progressive tube modification and unique taxic diversification concordant with changing habitats over time We interpret this as a post-extinction recovery and adaptive radiation sequence that mirrored coeval subequatorial faunas, and confirms hard substrate ecosystem depletion as a hallmark of the earliest Triassic interval globally. The most informative fossils derive from the subequatorial shallow Panthalassic basins bordering Western Pangaea[33], and the Tethyan margin of the South China Craton[34,35] These collectively infer disappearance of rich latest Permian encrusting benthos, and its subsequent replacement in the earliest Triassic by monogeneric colonies of microconchid tubeworms – an extinct suspension-feeding clade possibly related to ‘lophophorates’[36,37]. Our new fossils reveal compatible microconchid predominance, but with a unique Boreal signature of morphological diversification across changing depositional settings; this elucidates distinctive regional endemism, and opportunistic ecosystem expansion during the initial recovery phase after the P-T boundary

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