CALL FOR PROPOSALS:

ORGANIZERS

  • Harvey Thorleifson, Chair
    Minnesota Geological Survey
  • Carrie Jennings, Vice Chair
    Minnesota Geological Survey
  • David Bush, Technical Program Chair
    University of West Georgia
  • Jim Miller, Field Trip Chair
    University of Minnesota Duluth
  • Curtis M. Hudak, Sponsorship Chair
    Foth Infrastructure & Environment, LLC

 

Paper No. 11
Presentation Time: 4:25 PM

A COMPARISON OF PRE-AND POST-EXTINCTION SCLEROBIONT COMMUNITIES ACROSS THE LATE DEVONIAN MASS EXTINCTION IN NORTH AMERICA


SCHNEIDER, Chris L., Alberta Geological Survey, 4999 98th Av, Edmonton, AB T6B2X3, chris.schneider@ercb.ca

Across the Late Devonian mass extinction, pre- and post-extinction sclerobiont communities in North America were conspicuously dissimilar. Through a synthesis of literature-based review and new research, I compared Middle Devonian through the Late Mississippian sclerobiont communities in order to summarize the changes and similarities in encrustation patterns across the extinction.

In general, taxon richness and abundance of brachiopod-encrusting sclerobionts markedly declined. Branching colonial encrusters were greatly reduced; auloporid corals went extinct, and hederellids became a rare component in most Mississippian sclerobiont communities. Among common Devonian solitary encrusters, cornulitids remained abundant sclerobionts in many Mississippian communities, whereas microconchids often were a smaller proportion of the fauna. Craniate brachiopods and solitary rugose corals remained a minor component of post-extinction sclerobiont communities. Encrusting, sheet-like bryozoans became a more conspicuous portion of the Mississippian sclerobiont fauna, in that they filled a greater proportion of the sclerobiont fauna and occurred in more communities than those in the Devonian.

Most Devonian brachiopod faunas were dominated by finely-ribbed brachiopods, such as atrypids and stropheodonts, whereas smooth and spinose athyrids and productids were common components in benthic Mississippian ecosystems. Meanwhile, spiriferids were common in both pre- and post-extinction communities. Surviving sclerobiont lineages had to contend with changes in substrate morphology and availability.

Despite major pre- and post-extinction differences, several features established in pre-extinction sclerobiont faunas carried over into the Mississippian: (1) sclerobionts continued to preferentially encrust certain shell textures over others by shifting to new brachiopod taxa rather than generalizing on all available substrates; (2) some sclerobiont taxa remained specialists in the commissure-proximal niche; (3) based on preserved, calcified forms, apparent spatial competition was low in most communities; and (4) sclerobiont richness among communities was not controlled by the composition of the brachiopod fauna, but likely by other processes such as larval recruitment.

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