232 D29. Recent Developments in Phylogeny and Morphological Patterns (Posters)

Wednesday, 18 October 2023
8:00 AM - 5:30 PM
Hall B

COMPARATIVE HISTOLOGY OF IDIOGNATHODUS PA ELEMENTS: DOES GERONTIC MORPHOLOGY HAVE A MICROSTRUCTURAL SIGNATURE?

Paper number: 232-2
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

  • Neo McAdams Presenting Author
    Texas Tech University Department of Geosciences, Lubbock, TX

Abstract

Conodont elements were the first mineralized feeding structures in vertebrate history. Elements record the growth history and dynamics of the individual across the successive deposition of lamellae, including episodes of accretion, remodeling, and damage repair. Growth shapes the appearance of the element, including the development of characteristic morphology, or sometimes “gerontic” or pathological features. Gerontic elements are relatively common in collections, but their genesis is not well understood, although they are thought to belong to relatively old individuals due to their typically larger size. This research investigates whether gerontic elements develop microstructural differences over their lifetimes, such as changes in the amount or spatial arrangement of growth centers, spatiotemporal changes in relative rates of growth, or relationships between damage, remodeling, and “gerontic” features.

The specimens used in this study are both normal and gerontic (large, thickened, unusually sculptured) Pa elements of Idiognathodus from the Hushpuckney Shale of the Swope cyclothem (Late Pennsylvanian, Missourian/ Kasimovian; I. cancellosus Zone). Choosing one stratigraphic level protects against possible interference from signals of biotic or seawater geochemical evolution.

Elements were embedded in epoxy, ground to the plane of interest, and imaged with backscattered electrons to visualize the growth layers. Initial results demonstrate possible roles for addition of growth centers and changes in rates of growth, but extensive remodeling concentrated near both the oral and aboral surface of the specimens obscures microstructural details, and may represent the dominant factor in the morphology of gerontic individuals.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-396137

© Copyright 2023 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.