The jaw musculature of Dendroaspis angusticeps and Dendroaspis polylepis polylepis (Ophidia, Proteroglypha) with some remarks on the venom apparatus

Abstract

The venom apparatus in both species of Dendroaspis shows great similarity to that described in other proteroglyphs. There is a posterior bulbous portion or main gland and an anterior narrower portion, the accessory gland, that surrounds the secretory duct. The gland is enclosed in a very tough connective tissue capsule. Fibres from the m. adductor externus superficialis insert on the connective tissue capsule on the dorsal aspect of the venom gland. They serve to compress the gland and expel the venom when the snake strikes. Ventrally, fibres of the m. pterygoideus are also inserted on the investing sheath. This muscle supports the gland ventrally and also appears to play some role in venom ejection. The arrangement of the jaw musculature is similar in both species of Dendroaspis. Since the m. adductor externus superficialis is closely associated with the venom gland it has become highly specialized and exhibits great variation among snakes. This muscle in Dendroaspis differs from that in other proteroglyphs in the extension of its origin in a ventral direction over the postorbital bone to the maxilla. As in other elapids, the m. levator anguli oris is absent in both species of Dendroaspis.