Abstract
AbstractAn increasing number of unexpectedly diverse benthic communities are being reported from microbially precipitated carbonate facies in shallow-marine platform settings after the end-Permian mass extinction. Ostracoda, which was one of the most diverse and abundant metazoan groups during this interval, recorded its greatest diversity and abundance associated with these facies. Previous studies, however, focused mainly on taxonomic diversity and, therefore, left room for discussion of paleoecological significance. Here, we apply a morphometric method (semilandmarks) to investigate morphological variance through time to better understand the ecological consequences of the end-Permian mass extinction and to examine the hypothesis that microbial mats played a key role in ostracod survival. Our results show that taxonomic diversity and morphological disparity were decoupled during the end-Permian extinction and that morphological disparity declined rapidly at the onset of the end-Permian extinction, even though the high diversity of ostracods initially survived in some places. The decoupled changes in taxonomic diversity and morphological disparity suggest that the latter is a more robust proxy for understanding the ecological impact of the extinction event, and the low morphological disparity of ostracod faunas is a consequence of sustained environmental stress or a delayed post-Permian radiation. Furthermore, the similar morphological disparity of ostracods between microbialite and non-microbialite facies indicates that microbial mats most likely represent a taphonomic window rather than a biological refuge during the end-Permian extinction interval.
Highlights
The end-Permian mass extinction was the most catastrophic biotic crisis of the Phanerozoic, with the extinction of more than 80% of marine invertebrate species (Stanley 2016), and it occurred over a short interval (∼60 kyr) that spans the Permian/Triassic boundary (Burgess et al 2014; Wang et al 2014)
The pre-extinction ostracod assemblages show higher morphological disparity by a shift in morphospace occupation because of the presence of some species with extreme shapes that are not recorded from the extinction interval (Fig. 5C)
Two declines in morphological disparity occurred with the endPermian mass extinction: the major decline at the onset of the end-Permian extinction, except at Zuodeng, and a minor one at the end of the extinction interval
Summary
The end-Permian mass extinction was the most catastrophic biotic crisis of the Phanerozoic, with the extinction of more than 80% of marine invertebrate species (Stanley 2016), and it occurred over a short interval (∼60 kyr) that spans the Permian/Triassic boundary (Burgess et al 2014; Wang et al 2014). The pattern of extinction is, still disputed and often described as a single pulse (Jin et al 2000), multiple pulses (Song et al 2013), an extinction interval (Wang et al 2014), or with long-term environmental deterioration starting before the main extinction pulse (Kiessling et al 2018). In part, these different interpretations are due to sea-level changes overprinting on our understanding of the timing and pattern of extinction (Yin et al 2014; Holland and Patzkowsky 2015). The co-occurrence of microbialites and ostracods led Forel et al (2013b) to suggest that microbial mats provided favorable settings, or refuges, during the extinction interval that could support diverse and abundant ostracod communities
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