Cephalic morphology of Pythonichthys macrurus (Heterenchelyidae: Anguilliformes): specializations for head‐first burrowing

The Heterenchelyidae, a family of Anguilliformes, are highly specialized fossorial eels. This study was conducted to evaluate the cranial specialization in relation to head‐first burrowing behavior in the heterenchelyid, Pythonichthys macrurus . Thereby, detailed descriptions are provided of the cranial myology and osteology of P. macrurus and its differences with that of representatives of three families: the Moringuidae ( Moringua edwardsi ), a head‐first burrower; the Anguillidae ( Anguilla anguilla ), a nonburrowing representative and the Ophichthidae ( Pisodonophis boro ), a head and tail‐first burrower. This comparison may help to get a better understanding of the cranial specialization of head‐first burrowers in heterenchelyids and moringuids. We recognize as morphological adaptations to burrowing: reduced eye size, a caudoventral orientation of the anteromedial section of the adductor mandibulae muscle complex, the posterior position of the quadrate‐mandibular joint, a solid conical skull, large insertion sites of epaxial and hypaxial muscle on the neurocranium, a widened cephalic lateral line canals extending into the dermal cavities, and a ventral position of the gill opening. J. Morphol. 271:1053‐1065, 2010. © 2010 Wiley‐Liss, Inc.