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Early Triassic (Spathian) post-extinction microconchids from western Pangea

Published online by Cambridge University Press:  20 May 2016

Michał Zatoń
Affiliation:
University of Silesia, Faculty of Earth Sciences, Będzińska Street 60, PL-41-200 Sosnowiec, Poland,
Paul D. Taylor
Affiliation:
Natural History Museum, Department of Palaeontology, Cromwell Road, London SW7 5BD, United Kingdom,
Olev Vinn
Affiliation:
Department of Geology, University of Tartu, Ravila 14A, 50411 Tartu, Estonia,
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Abstract

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A new microconchid tentaculitoid, Microconchus utahensis new species, is described from the Lower Triassic (Spathian) Virgin Formation of two localities (Hurricane Cliffs and Beaver Dam Mountains) near St George, Utah. This small encrusting tubeworm, previously referred to erroneously as Spirorbis, has a laminated shell microstructure containing minute pores (punctae). The population from deeper water facies of the Beaver Dam Mountains is more abundant than that from Hurricane Cliffs and the tubes are significantly larger in size. Although represented by only one species (M. utahensis), microconchids are by far the most dominant component of the otherwise impoverished sclerobiont assemblage of the Virgin Formation, which also includes rare cemented bivalves and probable foraminifers. Whereas the remainder of the Virgin fauna is quite diverse, the low diversity of encrusters suggests a slow recovery from end-Permian mass extinctions. Indeed, more typically Mesozoic sclerobiont assemblages dominated by cyclostome bryozoans and serpulid polychaetes did not appear until the Late Triassic, probably Rhaetian.

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Type
Research Article
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Copyright © The Paleontological Society