Descriptive Osteology of the Family Chaudhuriidae (Teleostei, Synbranchiformes, Mastacembeloidei), with a Discussion of Its Relationships

Abstract
The little known earthworm eel family Chaudhuriidae consists of nine small to minute species of Asian freshwater fishes. In this paper, the osteology of seven representatives of the family is described in detail for the first time. We propose a list of 21 synapomorphies to support chaudhuriid monophyly. Reductive characters are: loss of basisphenoid, pterosphenoid, endopterygoid, dermopalatine, pars autopalatina, posttemporal, gill rakers, toothplate on pharyngobranchial two, distal pectoral radials, lateral line canals, dorsal- and anal-fin spines and their supporting pterygiophores, epurals, uroneurals, parhypural, and reduction in numbers of epicentrals and hypurals. Progressive characters are: presence of a long membrane bone process on autosphenotic, a boomerang-shaped ectopterygoid with a long preorbital extension, an anterior process of membrane bone of the metapterygoid, a unique arrangement of dorsal gill arch elements, separate foramina for the three trigeminal branches, and a ventromedian keel on the first vertebra. The new information is used to critically reevaluate previous hypotheses of chaudhuriid relationships. Finally, the issue of miniaturization in chaudhuriid fishes is addressed and discussed.