23-6 Global Morphological Alteration in Late Paleozoic Proetid Trilobites

Session: Phylogenetic and Computational Approaches in Paleobiology and Paleoecology, Part I

Presenting Author:

Authors:

Abstract:

The Devonian Period was a pivotal time of environmental change which contributed to changes in trilobite diversity. By the conclusion of the Devonian, only one order, Proetida, persisted. Understanding how this taxon survived can help elucidate evolutionary dymanics of “Dead-Clades walking.”

Though proetids survived through the biotic crises of the Middle and Late Devonian, these trilobites did not leave the Devonian unscathed. Diversity patterns were undoubtably altered across the order, including the loss of common and common genera, such as Gerastos, and the rise of a new family, Phillipsidae during the Devonian. Additionally, other families, notably the Aulacopleuridae and Brachymetopidae, were lost in the Early Carboniferous. Devonian diversity changes, mostly declines, have been previously correlated with disparity loss. More recently, it has been noted that there may be the persistence of certain “morphotypes” of proetids, such as a “phillipsid morphotype” while others, like the “Gerastos morphotype”, were lost.

The goal of this project is to investigate whether there are statistically discernable morphotypes and, if so, whether certain morphotypes, such as the elongated “phillipsid morphotype” had statistically greater persistence from the End-Devonian to the conclusion of the Paleozoic. To do this, we quantified proetid morphology through time using geometric morphometric techniques and tested whether or not morphospace contracted after the Devonian. Over one hundred and fifty articulated proetid specimens representing seventy species from the Early Devonian through the Early Permian were exampled.  Each specimen was photographed and characterized with landmark data. These data were subsequently statistically analyzed in using the geomorph package in R. Results of this study further elucidate the pathways by which proetids persisted a “Dead-Clade Walking” through the Carboniferous.

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

doi: 10.1130/abs/2025AM-7143

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