Application of shell spiral deviation methodology to fossil brachiopods: Implications for obtaining specimen ontogenetic ages

作者：Clark Joanna V^*; Aldridge Anthony E; Reolid Matias; Endo Kazuyoshi; Perez Huerta Alberto

来源：Palaeontologia Electronica, 2015, 18(3): 54A.

DOI：10.26879/577

• spiral deviations
• fossil brachiopods
• ontogenetic age
• digitizing
• R code

Knowledge of specimen ontogenetic ages of fossil brachiopods has great utility in paleoecological and paleoclimatic studies, but there is currently no efficient means of obtaining this information. Previous studies have shown that shell spiral deviations correspond to ontogenetic ages and seasonal growth in modern brachiopods, but this approach has not been tested on fossil specimens. Here, we analyze the application of this methodology using four species of fossil brachiopods, including Laqueus rubellus, Terebratula terebratula, Platystrophia ponderosa, and Pseudoatrypa sp., each of which possesses different shell outlines and surface ornamentation patterns. The computer programs Vextractor and R were used for digitizing and morphometric analyses, respectively. Our results indicate that smooth biconvex shells produce spiral deviation graphs similar to those generated from modern brachiopods that yield plausible ontogenetic ages, but without providing by themselves information on seasonal growth and factors controlling shell growth.

• 出版日期2015