Dwarf False Brook Salamander

Ixalotriton parvus is a small salamander with limited published information on its description. What is published is that I. parvus has a total length of about 77 millimeters. The head of I. parvus is longer than it is wide and one third as deep as it is long.The eyelids are longer than they are wide. Distance between eyes is slightly smaller than between snout and eyes. The distance separating the external nostrils is slightly larger than the distance separating internal nostrils. The distance between the axilla to groin is almost half the length of the tail. The tail width is almost equal to tail depth. The foot is wider than hand. The middle digits are markedly longer than outer digits (Lynch and Wake 1989).Ixalotriton parvus is a relatively small salamander compared to the other salamanders of the Oaxaca region in Southwestern Mexico. With exception to Pseudoeurycea saltator, the combination of size and distinctive color patterns separates I. parvus from other species of Pseudoeurycea genus. Ixalotriton parvus is distinguished from P. saltator due to the absence of a white tail tip that is seen on P. saltator. This distinction if often misidentified due to white or tan iridophore patches along the tail of I. parvus. In general appearance and ecology, I. parvus resembles a large Dendrotriton. They are differentiated by the possession of prefrontal bones and non-enlarged nostrils by I. parvus (Lynch and Wake 1989). Ixalotriton parvus color was described from a preserved specimen. The dorsal ground color is a dark gray brown color, with a lightened mid-dorsal region creating an indistinct medium brown stripe that extends over the length of the tail, where it is superimposed by large, scattered white iridophore patches. Due to a suffusion of small melanophores over unpigmented tissue, the stripe has a “dirty” appearance. The belly is pale gray with scattered inconspicuous flecks and larger more abundant white flecks on the lateral region of the trunk. The ventral surface of the tail is darker than the belly and displays fewer iridophores. The chin is light cream-colored, with a suffusion of tiny melanophores (Lynch and Wake 1989). Although the dorsal ground coloration is fairly similar in all specimens, there is wide variation to the degree of color in the mid-dorsal stripe. Few lack the stripe. Where present, the coloration varied from creamy white to dark brown. This is due to the degree of melanin reduction. The white tail spots vary in size and abundance. In general, those with reduced melanism in the mid-dorsal region, tend to be depigmented in the snout, parietal area, and limb bases. A suffusion white iridophores are invariably present on the venter and lateral region of the trunk. Due to limited sample sizes, sexual dimorphism isn’t evident. Ontogenetic variation does however exist. As compared to standardized juveniles, standardized adults have more maxillary, premaxillary, and vomerine teeth, longer limbs, and longer tails (Lynch and Wake 1989).The species authority is: Lynch, J. F., Wake D. B. (1989). "Two New Species of Pseudoeurycea (Amphibia: Caudata) from Oaxaca, Mexico." Natural History Museum of Los Angeles County, 411, 15-22.Seventeen protein loci were compared to find phylogenetic relationships among some salamanders of the genera Pseudoeurycea, Dendrotriton, Nyctanolis, and Ixalotriton. The proteins of P. saltator and I. parvus, were more similar to each other, than that of the other salamanders examined. This similarity is relatively insignificant, as the degree of genetic differentiation is substantial in comparison to other salamander genera. While P. saltator is more clearly aligned with Pseudoeurycea, I. parvus is more closely related to members of the genus Ixalotriton (Wake and Lynch 1989). Through later genetic analysis of sequences of 544 bp of the 16s mtDNA genes of 63 salamanders from the genera Pseudoeurycea, Ixalotriton, Lineatriton, Thorius, Batrachoseps and Parvimolge it was found that I. parvus and I. niger share the most common ancestor. Followed next by the most common ancestor with salamanders of the genera Pseudoeurycea and Lineatriton. Ixalotriton parvus’ next most related genera are, in order, Parvimolge, Thorius, Batrachoseps (Parra-Olea 2002). The genus Ixalotriton is derived from two Greek words: “ixalos” and “triton”. “Ixalos” translates to bounding or springing, which is in reference to the salamanders observed behavior. “Triton” is the commonly used Greek word for salamander. The species epithet, “parvus”, comes from the Latin word for small (Lynch and Wake 1989). Ixalotriton parvus was previously described as Pseudoeurycea parva and Ixalotriton parva, which are now synonyms (IUCN 2016).

Ixalotriton parvus has only been collected on and around Carro Baul in the Oaxaca region of Southwestern Mexico. Ixalotriton parvus inhabits the lone peak of Carro Baul between the elevational ranges of 1,500 to 1,900 m. They have only been found in bromeliads of the genera Vriesia and Tillandsia in cloud forests (Lynch and Wake 1989).

Ixalotriton parvus was collected inside an arboreal bromeliad. This indicates that the salamander is arboreal, and utilizes in bromeliads (Lynch and Wake 1989).

Ixalotriton parvus is considered “Critically Endangered” by the IUCN Redlist with a decreasing population. The forests on Cerro Baul are disturbed, and have been greatly reduced due to logging and agricultural activities, as well as a devastating fire in 1998 (IUCN 2016).

Ixalotriton parva, the dwarf false brook salamander, is a species of salamander in the family Plethodontidae. It is endemic to a small mountainous area of Mexico where its natural habitat is subtropical or tropical moist montane forests. It is threatened by habitat loss. There is some doubt whether this species should be classified as Pseudoeurycea parva or Ixalotriton parva.