187-2 Estimating the phylogenetic paleoecology of Paleozoic echinoderms (Diploporita: Blastozoa)

Session: Phylogenetic and Computational Approaches in Paleobiology and Paleoecology (Posters)

Poster Booth No.: 75

Presenting Author:

Elizabeth Altier

Authors:

Altier, Elizabeth Bickley¹, Sheffield, Sarah L.², Lamsdell, James Christopher³, Bauer, Jennifer E⁴, Lam, Adriane R.⁵

(1) Binghamton University, Freeville, NY, USA, (2) Binghamton University, Binghamton, NY, USA, (3) West Virginia University, Morgantown, WV, USA, (4) University of Michigan, Ann Arbor, Michigan, USA, (5) Binghamton University, Binghamton, NY, USA,

Abstract:

The fossil record of echinoderms, the group including sea stars and crinoids, spans the entire Phanerozoic. Many of the now-extinct early groups show high morphological diversity and disparity that make it challenging to understand echinoderm evolutionary history and paleoecology. Diploporan blastozoans (Ordovician – Devonian), defined largely by their distinct diplopore (“double pore”) respiratory structures, represent such a highly disparate group. Recent published phylogenies suggest that diploporans are polyphyletic, and diplopore respiratory structures have re-evolved numerous times throughout their evolutionary history. Understanding the biotic and abiotic factors behind both this convergent evolution in respiratory structures and the variety of morphologies within this group provides insight into drivers of both diploporan and broader echinoderm evolution, especially with respect to environmental variables that have influenced their biogeography and paleoecology. Here, we use phylogenetic paleoecology among diploporan phylogeny, ecology, and biogeography. Incorporating environmental characteristics such as water depth, substrate lithology, and energy of their environment into a rigorous phylogenetic framework allows for a holistic look at the evolutionary history and drivers underlying the development of  these echinoderms. We inferred Bayesian phylogenetic trees in RevBayes and used the resulting topology in biogeographic and paleoecologic analyses. We took the resulting phylogenetic estimation and performed a biogeographic analysis using R package ‘BioGeoBEARS’ to identify the direction and magnitude of dispersal throughout the study period. We then took the environmental data and performed a phylogenetic paleoecological analyses utilizing the R package ‘phytools’ and measured the phylogenetic signal through various statistical methods to inform us about the distribution of environmental occupation across the phylogeny to determine whether closely related species are likely to inhabit similar environments. Our findings indicate that, largely, environmental preferences are distinct between species and do not show strong phylogenetic conservatism, with occupied environments being dispersed across the phylogeny with multiple cases of ecological convergence. Most of the studied taxa here show low niche conservatism, which is inconsistent with other related echinoderm groups. Our results provide additional evidence that diploporans do not represent a natural evolutionary group. One group of diploporans that do represent a strongly supported monophyletic clade, the holocystitids, show much higher niche conservatism, which may lend insight into factors that may have contributed to survival of certain echinoderms groups across the Late Ordovician Mass Extinction.

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

doi: 10.1130/abs/2025AM-6513

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