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by The.Dark.One » Tue Nov 28, 2006 2:53 pm
Pages 17 - 18 in Kottelat's Indochinese Nemecheilines gives a discussion on the history of familial and sub familial relationships, and some of the problems that are still unresolved. Pages 164-165 of Jayaram's Fishes of the Indian Region also briefly discusses familial placement.
On a very basic level the Nemacheilinae have probably been lumped with Balitorinae, instead of the Cobitids, because the Nemacheilinae do not have the eye/head spine that Cobitids have (but in the past Roberts has included the Nemcheilines with the Cobitines)
It appears that Psilorhynchids, Parapsilorhynchids, and Balitorids have been seperated from each other partly because they all have a different swimbladder structure, and the number (or lack of them) of pairs of barbels. Nemacheilines probably don't have enough differences to warrant their own Family, and therefore because of the structure of the swimbladder being similar to Balitorins, they have been included in the Balitorid family.
I'm sure that at some point a phylogentic paper will be published which will hopefully resolve and answer these questions for you.