ENTERING ANOTHER DIMENSION: 2D AND 3D SHAPE ANALYSIS OF CLASSES RHYNCHONELLATA AND STROPHOMENATA (PHYLUM BRACHIOPODA)

The outline, body size, and overall shape of brachiopod shells are of great significance in visual recognition and are important for classification purposes, however, traditional morphometric studies are based on linear measurements that cannot capture the distinctive contours of a brachiopod shell. These distance measurements of shell morphology, such as height, width, length, or relative geometric locations of certain well-defined characters, known as ‘landmarks’, make up the majority of quantitative shape analysis of brachiopod shells. These traditional measurements may fail to capture the complex shape and curve of the brachiopod shell that can be examined utilizing modern shape analysis techniques. These modern techniques have been applied to morphological studies of other organisms, yet have been used little with fossil brachiopods. This study aims to investigate the 2D outline and 3D shape of brachiopods.

The Texas A&M University Invertebrate Paleontology Teaching collection contains 1681 individuals among 235 species of Brachiopoda. The classes Rhynchonellata and Strophomenata are well represented, 27 and 13 species having ten or more individuals, totaling 538 and 291 individuals respectively (125 and 55 species have nine or fewer individuals). The selected collection will be analyzed with multivariate outline analysis using SHAPE ver 1.3 and R, packages geomorph and Momocs, to determine shape differences between genera, families and orders. For a subset of this collection, representing 57 families of Rhynchonellata and 25 families of Strophomenata, high-resolution 3-D data of brachiopod external shell surfaces will be scanned with Nextengine 3D HD 2020i laser scanner and analyzed with R, package geomorph. The second aim of this study is to establish a digital collection of 3D fossil models of a variety of brachiopod shapes for educational use in paleobiology labs. Although there are some 3D scans of brachiopods available online, a comprehensive collection of high quality scans of shell shape variety among the classes, orders, and families in Rhynchonellata and Strophomenata for teaching is not available. 3D printing of teaching models will enhance the identification learning process for students and is useful when there is a limited number of fossil specimens in lab.