Abstract

Systematic revision of the Late Ordovician brachiopod generaEochonetesReed, 1917 andThaerodontaWang, 1949 was conducted utilizing specimen-based morphometric and species-level phylogenetic analyses. Previous studies had recognizedThaerodontaandEochonetesas either distinct taxonomic entities or synonyms. New multivariate and phylogenetic analyses confirm the synonymy ofThaerodontawithEochonetesand provide a framework to assess evolutionary and ecological patterns within the clade. Multivariate analyses were employed to delineate species in morphospace and provided information on potential species relationships. Phylogenetic analysis was used to produce an evolutionary framework for taxonomic revision and identify character evolution within the clade. Most species previously assigned toThaerodontaare transferred toEochonetes, and three others are excluded fromEochonetesand provisionally referred to other sowerbyellid genera. Three new species (Eochonetes maearumnew species,E. voldemortusnew species,E. minervanew species) are described, one species (Leptaena saxeaSardeson, 1892) is synonymized withE. recedensSardeson, 1892, and one subspecies (Thaerodonta mucronata scabraHowe, 1965) is rejected. This study demonstrates that a combination of complementary approaches and data types has the potential to advance interpretations beyond analyses confined to single analytical tools. Specifically, multivariate analyses provide constraints on species boundaries, whereas species-level phylogenetic analyses provide frameworks to examine morphological, ecological, and biogeographic evolution within a clade.