Phylogenetic systematics of the Homalonotidae (Trilobita): taxonomic reassessment and implications for Devonian trilobites

Homalonotidae is a morphologically distinctive trilobite family well known in systematics studies, yet phylogenetic studies remain scarce. This study investigated internal relationships among taxa within the Homalonotidae family and reassessed the classification of problematic species. A phylogenetic analysis was conducted using a matrix composed of 36 taxa and 56 morphological characters of the trilobite exoskeleton. Analysis under the TBR algorithm recovered eight most parsimonious trees, from which a strict consensus tree was obtained. The results revealed substantial inconsistencies in the diagnosis of several genera and species, particularly due to the presence of paraphyletic and polyphyletic groupings. Some taxa, such as Burmeisteria fontinalis, Dipleura dekayi, and Burmeisterella braziliensis, remained phylogenetically stable and well-supported. Conversely, certain species traditionally assigned to Burmeisteria, including B. oiara and B. antarcticus, behaved as wild-cards within the trees, leading to their reclassification as Burmeisteria sp. Moreover, strong phylogenetic correlations were identified between species from different genera. These findings challenge the current taxonomic framework and allow for the proposal of new taxonomic arrangements. Furthermore, the relationships among the taxa indicate that Devonian Homalonotidae reflect a complex palaeobiogeographic system and further suggests that the Gondwana basins functioned as a dynamically connected network during the Devonian period.