Zur Ontogenese Der Bulla Tympanica Von Tupaia Glis Diard 1820 (Prosimiae, Tupaiiformes

Abstract

The bulla tympanic of Tupaia glis develops from an independent cartilaginous entotympanicum. A very small processus tympanicus petrosi caudal is comprises part of the bullar wall. Early in ontogeny the entotympanicum fuses with the petrosum at two points (tegmen tympani and processus tympanicus petrosi caudalis). All fusions of the entotympanicum with other elements of the skull are regarded as secondary. It is suggested that the entotympanicum (and also the cartilage of the auditory tube) is a new acquisition of mammals, with no genetic relations to any other structures. The author''s opinion is that the bulla of the malagassy prosimians was developed from a tupaioid bulla by "fusio primordialis" of the entotympanicum and petrosum. This bulla follows the form of the tupaioid entotympanic bulla.