Evolutionary morphology of the zygomatic gland and lacrimal bulla in roe deer (Capreolus capreolus linnaeus, 1758-Mammalia, Cervidae)

The dissection of the heads of three adult roe deer (Capreolus capreolus) p rovided evidence that this species of the Cervidae, like carnivores, lagomo rphs and certain members of the Bovidae, possesses a zygomatic salivary gla nd. Homology of this salivary gland in ruminants and carnivores is assumed on the basis of its over-all topographic position and the number and course of its excretory ducts. The zygomatic gland of roe deer is a polystomatic gland and amounts to 0.02% of body weight. As in Saiga tatarica and Caprico rnis crispus (Bovidae), its secretions are predominantly serous. Its slight ly alterated position in roe deer (and in bovids) seems to be caused by an evolutionary transformation of orbitotemporal proportions and the formation of a lacrimal bulla, in particular. This is an inflation of the intraorbit al portion of the lacrimal bone providing ventral support to the ocular bul b. The lacrimal bulla is a late evolved character and emerges late in ontog eny. Its postnatal development in roe deer is presented. Comparison with th e neonatal stage of lacrimal morphology in cattle suggests a similar onto-g genetic development in the Bovidae. The adult grysbok (Raphicerus melanoti s, Neotraginae, Bovidae) provides a,model situation' of the primitive chara cter state at the beginning of the evolutionary development of a lacrimal b ulla. Zygomatic gland, lacrimal bulla and other structural elements of the ruminant orbitotemporal region provide an example of the interlocked evolut ionary transformation of a complex system, the morphological result of whic h is a multi-layered compromise between several structurofunctional constra ints.