Comprehensive DescriptionRead full entry
Pseudohynobius puxiongensis is a relatively small, smooth-skinned salamander with well-developed limbs. The head is depressed; the body is slightly depressed, with a cylindrical trunk. Palms and soles lack horny coverings. Four fingers are present on each hand and five toes on each foot. This species has thirteen distinct costal folds. No labial fold is present. The tail is slender, and is shorter than the snout-vent length (SVL). No obvious tail fin fold is present. Vomerine teeth occur in two obliquely arched series, which are relatively short. Coloration is uniformly grayish (Fei and Ye 2000; Raffaëlli 2007).
This species is the only five-toed hynobiid salamander found in the Hengduan Mountains, Tibetan Plateau, where four-toed species of Batrachuperus have been known for many years (see Peng et al. 2010). Based on the presence of a unique internasal bone, Fei and Ye (2000) placed this species in a new subfamily, Protohynobiinae, thought to be the most basal within the family Hynobiidae. The presence of the internasal bone was thought to be a primitive character retained in this species but lost by a common ancestor of all other hynobiid salamanders (Fei and Ye 2000). However, this placement was based on a single specimen, collected in 1965 and described in 2000. More recently, Peng et al. (2010) have reported finding more specimens at the type locality. These authors note that the new specimens match all characters mentioned in the description of the holotype except for two. First, in contrast to the holotype, the new specimens all lack the internasal bone, suggesting that the presence of this bone in the holotype was due to individual variation (Peng et al. 2010). Second, the holotype lacks a premaxillary fontanelle, but a very small fontanelle was present in one of the specimens examined; however, premaxillary fontanelles are known to vary in both presence/absence and size between individuals of the same species (Peng et al. 2010). These authors also sequenced the complete mitochondrial genome for this species plus two additional species of Pseudohynobius; these new sequences were used along with eighteen previously published hynobiid mitochondrial genome sequences to reconstruct a phylogeny of the family Hynobiidae and showing that Protohynobius puxiongensis is deeply nested within Hynobiidae. Peng et al. (2010) found that there was thus no support for the validity of the subfamily Protohynobiinae, and proposed changing the genus from Protohynobius to Pseudohynobius.
The karyotype is 2n=52, as is the case for the genus Pseudohynobius (Peng et al. 2010).