Cranio-mandibular morphometry of selected Philippine mammalian species: Pteropus vampyrus (Linnaeus, 1758), cynocephalus volans (Linnaeus, 1758), macaca fascicularis (raffles, 1821), and tarsitus syrichta (Linnaeus, 1758)

The Orders Chiroptera, Dermoptera, and Primates were traditionally grouped to the superorder Archonta. The chiropteran Pteropus vampyrus (bats), dermopteran Cynocephalus volans (flying lemurs), and the primates Macaca fascicularis (macaques), and Tarsius syrichta (tarsiers) were utilized in the study to show the relationships between and among them using cranio-mandibular morphometry. A total of 32 morphometric characters of the skull were considered for the cluster analysis using Euclidean Distance Measure and Nearest Neighbor Linkage, including the generation of scatter diagrams. The Two-way Indicator Species Analysis (TWINSPAN) was also performed to determine the morphometric characters useful in clustering them. The results of the statistical analyses revealed the following six distinct clusters: 2 Macaca and 2 Pteropus groups, the Cynocephalus group, and the Tarsius group. The most closely related groups were the flying lemurs and the bats. The two also shared similarities with the macaques and since altogether shown to be a sister group to the tarsiers, suggest relatedness with the primates. The tarsiers, however, also exhibited several more unique morphometric characters that makes it distantly related to the macaques and the other mammals, as well. All the morphometric characters of the skull, except for the mandibular ramus height, and the orbital diameter length and height, provided useful information in delineating genera or groups of genera. Also, the total skull length (premaxilla to superior nuchal line), condylobasal length (premaxilla to occipital condyle), and the basal length (premaxilla to foramen magnum) consistently exhibited the widest variation among the four genera. The present study showed that cranio-mandibular morphometry can help determine the relationships between and among the three mammalian orders. It can even be a valuable addition in identifying the genera, and possible subpopulations of the species of particular taxa i.e. Macaca fascicularis and Pteropus vampyrus. Although molecular studies also suggest the grouping of the flying lemurs, macaques, and tarsiers, there were incongruences with their relationships. Also, the present study does not support the separation of the chiropterans from the other orders as implied by molecular studies