Phylogeny and Evolution of Mecochiridae (Decapoda: Reptantia: Glypheoidea): An Integrated Morphometric and Cladistic Approach

Abstract

This study provides a systematic and phylogenetic overview of the extinct reptant decapod family Mecochiridae. Mecochiridae are distinguished from both their traditional out-groups, Glypheidae and Erymidae, using cladistic and geometric morphometric techniques. Cladistic analysis of 12 species using 21 traditional and new characters verifies the in-group genera Mecochirus and Pseudoglyphea. Glyphea emerges as a sister group to Pseudoglyphea, suggesting a re-assignment of the genus to Glypheidae. The genus Meyeria is recovered as paraphyletic, suggesting the establishment of a new taxonomic group for species of Meyeria that exhibit a posterior tuberculated ridge, a well-developed hepatic bulge or ridge, and unornamented pleura. Both relative warp and Eigenshape analysis of the carapace and groove patterns that have long been used as descriptive morphological features succeeded in highlighting modes of shape change that when subjected to a discriminant analysis proved useful in distinguishing members of Mecochiridae. This study shows that landmark geometric morphometric methods and eigenshape analysis can be used to investigate the fidelity of existing taxonomic groupings based on other methods, and that an integrated cladistic and morphometric methodology has the potential to aid in resolving relationships among other unknown or problematic fossil taxa.