Friday, April 8, 2016

Barbour's Hexagonal Scaled Bachia, Bachia trinitatis (Family Gymnophthalmidae)

Bachia alleni Barbour 1914:315
Bachia alleni — Mertens 1972.
Bachia heteropa alleni Dixon, 1973:32.
Bachia heteropus alleni Schwartz and Thomas 1975:109.
Scolecosaurus trinitatis Barbour 1914
Bachia alleni trinitatis — Donoso-Barros 1968

Dixon (1973) considered populations in northern Venezuela, Trinidad, Tobago, Gre­nada and the Grenadines Bachia heteropa despite dramatic variation in numerous morphological traits: 5–12 longitudinal rows of hexagonal, imbricate, smooth scales on the dorsum; 16–22 longitudinal rows of quadrangular, juxtaposed, lateral and ventral scales; 24 –31 scale rows around mid-body, 24–36 transverse ventral rows, some have prefrontal scales some do not. Perhaps most telling was the number of digits. Bachia heteropa could have two, three, or four toes on each hind foot and the number of digits is geographically concordant. Dixon positioned Scoleocosaurus trinitatis Barbour, S. alleni Barbour, B. lineata Boulenger, B. marcelae Donoso-Barrios and Garrido, as subspecies of B. heteropa. Most recently Rivas et al. (2012) wrote, “Bachia heteropa is a polytypic species composed of five subspecies, four of which are present in Venezuela.” The literature on Bachia heteropa was summarized by John et al. (2012) they followed Dixon’s (1973) arrangement of subspecies and noted B. anomala Roux, placed in the synonymy of B. lineata by Burt and Burt (1933), may be a valid species as noted by Shreve (1947).

Above. Bachia trinitatis from Tobago.

Bachia heteropa
(sensu Dixon 1973) is composed of two morphological groups, species with prefrontal scales (mostly island species) and species without prefrontal scales (mostly mainland species). The mainland species Dixon synonymized under B. heteropa Ruthven are B. lineata Boulenger, B. anomala Roux, and B. marcelae Donoso-Barros and Garrido. Morphologically the mainland and island groups are readily distinguished. Mainland species usually have no prefrontals, two or three supraocular scales (as opposed to four in island species), two or three toes on the feet (as opposed to four in eastern Caribbean species); and quadrangular scales on the tail (as opposed to hexagonal tail scales in the island species).

Given the molecular evidence (Kohlsdorf & Wagner 2006; Kohlsdorf et al, 2010) Bachia heteropa (sensu Dixon, 1973) is polyphyletic.

Bachia alleni is found in Grenada, the Grenadines. Bachia trinitatis occurs on Trinidad, Tobago, Little Tobago, and in the Bocas. It inhabits the leaf litter and moves using a side to side motion of its body and tail.

Barbour T. 1914. A Contribution to the Zoögeography of the West Indies, with Especial Reference to Amphibians and Reptiles. Memoirs of the Museum of Comparative Zoology 44 (2): 205-359

Barbour T. 1933. Notes on Scolecosaurus. Copeia 1933 (2): 74-77.

Dixon, J.R. (1973) A systematic review of the teiid lizards, genus Bachia, with remarks on Heterodactylus and Anotosaura. Miscellaneous Publications of the University of Kansas Museum of Natural History, 57, 1–47.

John, R.R., Bentz, E.J., Rivera Rodriguez, M.J., Bauer, A.M., & Powell, R. (2012) Bachia heteropa (Lichtenstein and von Martens). Earless Worm Lizard. Catalogue of American Amphibians and Reptiles, 894:1–9.

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