1Centre for Research in Evolutionary, Social & Inter-Disciplinary Anthropology, University of Roehampton, 2Graduate Center & New York Consortium in Evolutionary Primatology, CUNY
April 17, 2020 , Platinum Ballroom
Skeletal features diagnosing clades are essential for determining the phylogenetic relationships of fossil taxa. Hominoids (extant and fossil) have been hypothesised to share a synapomorphy of a wide frontal at the coronal suture; alternatively, this condition has also been explained via allometry. These proposals are tested here via analysis of the angle of the coronal suture at bregma.
Coronal suture angle at bregma was measured from photographs of primate crania in norma superioris. Variation across higher taxa was determined via ANOVA and Tukey’s Posthoc test. Allometry was tested at the level of genus, with mean angle correlated with body and brain weight, respectively. Character state reconstruction was achieved via homogeneous subset coding and traced across the extant primate topology.
Mean bregmatic angle for genera is not significantly correlated with body or brain weight. Significant variation is present between higher taxa, however, with Platyrrhini and Hylobatidae possessing a narrow frontal. Character state reconstruction by genus shows the narrow condition is derived within Primates; platyrrhines and hylobatids evolved the narrow condition convergently, although variation within Platyrrhini renders reconstruction of their last common ancestor equivocal.
The wide frontal in Hominoidea is thus the primitive condition for Catarrhini and does not indicate propinquity of descent, nor is it a passive consequence of size. The presence of the derived narrow condition in platyrrhines and hylobatids has implications for the interpretation of the fossil record.