The ear region of the Philippine flying lemur Cynocephalus volans (Placentalia, Dermoptera)

The placental order Dermoptera, which includes two extant species, the Philippine and Sunda flying lemurs, Cynocephalus volans and Galeopterus variegatus, respectively, is generally held to be the sister group of Primates. Yet, little has been reported on their cranial anatomy. Here, the anatomy of the ear region is described and illustrated for a juvenile and adult C. volans based on CT scans. The inclusion of a juvenile is essential as nearly all cranial sutures are fused in the adult. Soft tissues are reconstructed based on sectioned histological pre- and postnatal specimens previously reported by the author. Numerous unusual features are identified, including: a small parasphenoid beneath the basisphenoid, a tensor tympani fossa on the epitympanic wing of the squamosal, a cavum supracochleare for the geniculate ganglion of the facial nerve that is not enclosed in the petrosal bone, a secondary facial foramen between the petrosal and squamosal, a secondary posttemporal foramen leading to the primary one, a subarcuate fossa that is floored in part by a large contribution from the squamosal, a body of the incus larger than the head of the malleus, and a crus longum of the incus that lacks an osseous connection to the lenticular process. Documentation of the anatomy of the Philippine flying lemur ear region is an essential first step in morphological phylogenetic analyses where features of the basicranium are widely sampled.

Automated summary

This study describes and illustrates the anatomy of the ear region for a juvenile and adult Philippine flying lemur. Several unusual features are identified, including a small parasphenoid, a tensor tympani fossa, a cavum supracochleare, secondary facial and posttemporal foramina, a subarcuate fossa, an oversized body of the incus, and a disconnected crus longum of the incus. Documenting the anatomy of the ear region in the Philippine flying lemur is important for morphological phylogenetic analyses.