Comprehensive DescriptionRead full entry
Ixalotriton niger is a scansorial (climbing) and very active plethodontid salamander belonging to the supergenus Bolitoglossa. In fact ixalos is greek for bounding or springing, referring to its behavior. At the time of its discovery in 1973 (see Wake and Johnson 1989), it was thought to belong to the genus Pseudoeurycea or the (at that time) recently described monotypic genus Nyctanolis (which it only differs from in having a signle premaxillary bone and in lacking dorsal markings on its jet black body coloration). Morphologically, no other member of the supergenus resembles Ixalotriton in possessing large protuberant eyes, long legs, hands, and feet. I. niger most closely resembles members of the genus Pseudoeurycea in skeletal characters, but differs from them in the presence of the above mentioned traits which are adaptive for climbing.
I. Niger is long and slender, males reaching a maximum of 59.7 mm and females reaching 58.9. The tail is long and strongly tapered. Head is broad and flat with a large amount of very small premaxillary-maxillary teeth (ranging from 78-150). Vomerine teeth are also high in number, ranging from 31-52. The small vomerine teeth are arranged in a long series that is a flattened curve lying almost perpendicular to the midline. Males have a round mental gland that never reaches a diameter of more than one-third the width of the head. Head is broader than the body. A postorbital groove is present posteriorly behind the eye and meets with the nuchal groove. The tongue is not attached anteriorly and is the typical boletoid form found in the supergenus Bolitoglossa.
Coloration in this species is a solid glossy black (by day) to brown (at night). There is a small amount of white pigment in the snout region with red-tinted toe tips (may not be pigment, but rather a lack of pigment which allows for the vascularized tissue underneath to be seen more easily). Nasolabial protuberances are white-tipped.