70-9 Paleontological studies on Devonian invertebrate fossils sheds new light on the paleobiogeography of eastern and northwestern North America

Session: Paleontology, Biogeography/Biostratigraphy & Phylogenetic/Morphological Patterns (Posters)

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Abstract:

The past two decades have witnessed a marked decline in the number of Devonian paleontologists in North America, leaving very few active students involved in this research. Both of us have undertaken collaborative research in this interval to renew ongoing studies which we hope will utilize new concepts to further illuminate existing problems related to the Devonian paleobiogeography of our continent. Our combined paleontological skills in brachiopods and gastropods, two of the most important paleobiogeographic groups in this interval, have yielded promising results. The Lower Devonian (late Pragian) Glenerie Formation fauna and its equivalents in eastern North America are currently under study and show, among the brachiopod faunas, the near complete absence of atrypid and gypidulid brachiopods which are better represented in underlying the Helderberg Group and post-Glenerie strata of the Lower Devonian in eastern North America. By Early Devonian time these faunas were very close to those of northern South America.

The Glenerie fauna is characteristic of the southern and eastern margins of Laurentia and belongs to the Eastern Americas Realm (EAR). In contrast, the coeval Pragian brachiopod fauna from cratonic east-central Alaska and Yukon Territory, as well as accreted terranes of Alaska, differ markedly in the abundance of gypiduloid brachiopods (notably belonging to the genus Ivdelinia) and atrypoid brachiopods. These faunas paleobiogeographically belong to the Old World Realm (OWR).  The Emsian brachiopods in this latter area likewise contain distinctive brachiopods of the same basic generic composition, including the Siberian rhynchonellid genus Sibirirhynchia.

Gastropods from Eastern North America of Lower and Middle Devonian are characterized by the exotic spinose genus Spiniplatyceras which is known from the EAR, but which is absent completely from western and Arctic North America. The EAR, based on its faunal and lithologic character, appears to represent slightly cooler waters than those bathing the OWR.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10293

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