Pholidichthys anguis, a new species of pholidichthyid fish from Northern Territory and Western Australia

Pholidichthys anguis is only the second species known in the family Pholidichthyidae. It differs from P. leucotaenia in having 87-98 dorsal-fin rays (vs. 66-79), 70-81 anal-fin rays (vs. 49-62), 90-101 total vertebrae (vs. 71-79), a more slender body, and a shorter head and maxillary. In addition, the color pattern of juveniles ( similar to 50-103 mm SL) differ in having the depth of the slender dark stripe on midside at vertical from anal-fin origin about 1 mm, usually much less (vs. depth 2.5-3.3 mm). Study of whole specimens and skeletal preparations of P. anguis indicates that the species exhibit the same familial specializations as P. leucotaenia. The two species are distributed allopatrically. We hypothesize that the common ancestor of the two species of Pholidichthys had a Tethyan distribution exclusive of Australia-New Guinea (ANG). When ANG collided with SE Asia, the ancestor invaded ANG. During a subsequent interglacial period, ecological factors contributed to the isolation of the Australian portion of the ancestral population from the New Guinea portion, and permitted divergence of the isolates.