T204 Biotic Interactions through Time II

Thursday, 29 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

ECOLOGICAL AND PALEOECOLOGICAL IMPLICATIONS OF MARGINAL TRACES IN ECHINOIDS FROM THE GULF OF MEXICO

Paper number: T204-14
Program: Technical Sessions
Time: 4:05 PM – 4:15 PM

Authors

Abstract

Crustaceans and several fish species have been observed to produce marginal predatory traces on sand dollar (Echinoidea: Clypeasteroida) tests in modern environments. These traces appear to be non-lethal and they are commonly observed in live-collected echinoid specimens. Traces comparable in morphology and location to those found in Recent sand dollars are also observed in fossil specimens. Although non-lethal marginal traces may provide quantifiable data on biotic interactions affecting both modern and fossil sand dollars, they remain underexplored. Here, we characterize non-lethal marginal traces on live-collected sand dollars (n = 735) from the northeastern Gulf of Mexico. These include four species: Encope aberrans, Encope michelini, Clypeaster subdepressus, and Mellita tenuis. Marginal traces were identified in the live-collected specimens and diagnostic characteristics, including trace morphology, number of traces, location on the sand dollar test were recorded. The frequency of traces was higher in the case of sand dollars with flatter tests (53.0% for E. aberrans, 69.4% for E. michelini, and 60.6% for M. tenuis) compared to sand dollars with thick-margined tests (10.9% for C. subdepressus). The flatter sand dollar specimens also appeared to have a higher frequency of multiple traces per specimen (62.1% of trace bearing specimens identified as Encope spp. and M. tenuis had two or more traces on the test). The marginal traces were cuspate in shape, healed, and located along the ambitus of the tests. The traces rarely extend into the petals, suggesting that injuries that involve petals may be lethal. Marginal traces comparable to the non-lethal traces documented here for Recent sand dollar specimens have also been observed in post-Miocene fossil specimens from Florida. Characteristics of modern traces represent a useful protocol for identifying non-lethal predation on fossil sand dollars. Marginal traces provide a valuable proxy of biotic interactions that can augment our understanding of the evolutionary history of non-lethal predation.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-357410

© Copyright 2020 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.