Systematics, biostratigraphy and significance of discoid and partly discoid corals from the Devonian of northwestern Canada, Ural Mountains Russia and southeastern Australia

 

Authors: Pedder AEH

Published in: Bulletin of Geosciences, volume 94, issue 2; pages: 137 - 168; Received 9 November 2018; Accepted in revised form 21 March 2019; Online 17 June 2019

Keywords: Devonian, discoid corals, Canada, Urals, Australia, biostratigraphy, palaeozoogeography,

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Abstract

Subfamily Microcyclinae Plusquellec, 2006 is promoted to family rank. A new family, genus and species, Devonodiscidae, Devonodiscus and D. latisubex are named. Combophyllum multiradiatum Meek, 1868, which is based on a specimen from an unknown Mackenzie Valley location and formation, is assigned to Devonodiscus and redescribed using specimens from accurately known formations and locations. Glossophyllum discoideum Soshkina, 1936, from the Eifelian of the Ural Mountains, is also assigned to Devonodiscus. Six other species, previously placed in either Combophyllum, Palaeocyclus, Microcyclus, Hadrophyllum or Chonophyllum, may belong to Devonodiscus. New topotypic material of one of these, Hadrophyllum wellingtonense Packham, 1954 is illustrated. In late ontogeny Devonodiscus latisubex and D. discoideum (Soshkina) commonly modified their corallum to become cylindrical with a cystiphylloid-like interior. Glossophyllum discoideum may regain a discoid morphology, making the corallum pulley-shaped. Such changes were probably caused by disruptions to bedding surfaces on which the corals developed. An unrelated coral, originally named Actinocystis versiformis is discoid becoming cylindrical after disruptions caused by increased water-depth. New specimens from the type locality in the central Western Urals are described and illustrated as Digonophyllum versiforme (Markov, 1923). The species’ complicated taxonomy and synonymy are attempted. High resolution stratigraphy indicates Devonodiscus multiradiatus to be confined to the middle Eifelian Eoschuchertella adoceta benthic assemblage and australis conodont zones, and D. latisubex to the late Eifelian upper Carinatrypa dysmorphostrota benthic assemblage and upper kockelianus conodont zones. Canadian discoid corals add further evidence that northwestern continental Canada and Northern Urals belonged to the same faunal province in late Eifelian time.