New Quantitative Methods For Analyzing Brachiopod Shell Shape: An Exploratory Study Of The Morphology Of Cincinnatian Rhynchonelliformea During The Late Ordovician Richmondian Invasion

The external valve morphology of Brachiopoda is a common focus within the field of invertebrate paleontology and previous studies have been largely focused on the morphological features that are indicators of functional adaptations, but there is a need for comprehensive descriptions of the entire external morphology of brachiopods to fill the gaps in systematic descriptions and studies of morphology. This study established a Multilevel Morphological Index composed of 18 characters each with 5 character states structured that allows for coding and analysis in multi-dimensional space where the relative relationship of each brachiopod’s morphology can be observed. To test the validity of the Multilevel Morphological Index, this approach was applied to species from Stigall (2010)’s study on the paleobiogeographic distribution of Cincinnati-type brachiopods from the Cincinnati-Arch.Species were analyzed for morphological variability with and without a priori groups based on niche tolerance and bio-stratigraphic occurrence across the Richmondian Invasion during the late Ordovician. Results support the new approach as a viable and effective mode of morphological analysis, providing insight into patterns in distribution based on changing environmental conditions and habitat tolerance including support of delayed niche occupation revealed by morphological consistencies between locally extinct species and invasive species in the Richmondian.