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1 September 2011 Larval to Adult Growth Stages and Paleoenvironment of Odontogryphaea thirsae (Gabb, 1861): A Late Paleocene Oyster from the Northern Gulf Coastal Plain, U.S.A.
Lloyd N. Glawe, Dennis E. Bell, David T. Dockery III, John F. Anderson
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Abstract

Assemblages of the boat-shaped bivalve Odontogryphaea thirsae (Gabb, 1861) from southwestern Alabama are used to define three ontogenetic growth stages that are bounded by major discontinuities in either mineral structure or growth-line prominence. Features of the larval and juvenile stages are described here for the first time and are compared with the well-known morphologic features that distinguish adults (late dissoconchs).

The larval stage is represented by prodissoconch valves which are about 0.4 mm in height with suborbicular outlines, commarginal striations, and ridge-like, opisthogyral beaks. The juvenile (early dissoconch) stage is expressed by dissoconch valves up to 19 mm in height with elliptical outlines (height > length), indistinct commarginal growth lines, flat commissural planes, and tiny attachment areas on left valves; the valve interiors exhibit a posterior adductor muscle scar, a resilifer, and chomata. The adult (late dissoconch) stage is characterized by dissoconch valves >19 mm in height with subtriangular outlines, prominent commarginal growth lines, wavy commissural planes, and a keel-like terebratuloid fold.

Paleonvironmental and stratigraphic studies of the diversely fossiliferous Odontogryphaea thirsae beds indicate 0. thirsae (Gabb, 1861) thrived in a shallow, normal-marine, tropical sea that extended from Texas to Georgia about 57 million years ago.

The Paleontological Society
Lloyd N. Glawe, Dennis E. Bell, David T. Dockery III, and John F. Anderson "Larval to Adult Growth Stages and Paleoenvironment of Odontogryphaea thirsae (Gabb, 1861): A Late Paleocene Oyster from the Northern Gulf Coastal Plain, U.S.A.," Journal of Paleontology 85(5), 977-986, (1 September 2011). https://doi.org/10.1666/09-143.1
Accepted: 1 April 2011; Published: 1 September 2011
JOURNAL ARTICLE
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