Geological Society of America

T186 Cephalopods through Time (Posters)

Tuesday, 6 November 2018
9:00 AM - 6:30 PM
Halls J-K

SCLEROCHRONOLOGICAL STUDY ON AMMONOID JAWS

Paper number: T186-7
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Isabelle Rouget
Sorbonne Université, Paris
Isabelle Kruta Presenting Author
American Museum of Natural History, New York, NY
Isabelle Kruta Presenting Author
Sorbonne Université, Paris
Vincent Mouchi
Observatoire Océanologique de Banyuls, Banyuls/Mer
Léo Pazzé
Sorbonne Université, Paris
Yannicke Dauphin
Museum National d’Histoire Naturelle, Centre National de la Recherche Scientifique, Ecole Pratique des Hautes Etudes, Sorbonne Université, Paris
Loïc Segalen
Sorbonne Université, Centre National de la Recherche Scientifique : UMR7193, Paris
Neil Landman
American Museum of Natural History, New York, NY
Lukas Baumgartner
University of Lausanne, Lausanne

Abstract

Sclerochonological studies carried out on Recent and fossil mollusks provide a methodological framework that could be applied to ammonite lower jaws. As a challenge for macroevolutionary studies, age estimations based on growth features and chemical compositions of the low Sr aragonitic outer shell have been attempted on few exceptionally preserved specimens, but remain questionable. Compared to the aragonitic shell, the calcitic covering of the lower jaw (called aptychus) is poorly investigated although in Recent cephalopods, chitinous beaks are considered relevant proxies for the age of the animal.

Following these studies, well-preserved aptychi from the Campanian of Alabama (Mooreville Chalk) were investigated to assess their potential for sclerochonological studies. We analyzed growth lines spacing, microstructure, and variation of the chemical composition along the growth direction (∂¹⁸O) and trace elements. Microstructural observations indicate that fine growth features (up to 2 μm thick) are well preserved and that a part of paleobiological information is preserved.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-320336

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