New research on the phylogeny of cyprinidontiform fishes, soon to be published in the Journal Zoologica Scripta, suggests that the Indian Killifish genus Aplocheilus is the sister group to all other cyprinidontiform fishes.
The new insight on the intrarelationships of cyprinidontiform fishes, commonly referred to as killifishes, topminnows, or toothcarps, comes from the detailed anatomical studies of Stefan Hertwig, a researcher at the Natural History Museum, Bern (Switzerland).
Hertwig utilized seventy-eight characters derived from the muscles, connective tissue elements and nervous system of the jaws of ninety-five species of cyprinidontiform fishes to reconstruct the phylogeny of the order.
Species from all currently recognised cyprinidontiform families were examined, including members of the Aplocheilidae, Rivulidae, Profundulidae, Goodeidae, Valencidae, Fundulidae, Cyprinodontidae, Anablepidae and Poeciliidae.
In the resulting phylogeny, members of the Indian Killifish genus Aplocheilus (commonly referred to as blue, golden or lined panchax) were recovered as the most basal member of the order, forming the sister group to all cyprinidontiforms. Members of the Madagascan genus Pachypanchax were the next group to split off, forming the sister group to all other cyprinidontiforms excluding Aplocheilus.
Previous studies of cyprinidontiform relationships, based mostly on skeletal characters and more recently DNA characters, have suggested different patterns of relationship to those discovered by Hertwig.
The results of Hertwig s study are of particular interest because they are in agreement current hypotheses for the break-up of Gondwana (a supercontinent that included most of the landmasses in today s southern hemisphere, including Antarctica, South America, Africa, Madagascar, Australia-New Guinea, and New Zealand).
A similar biogeographic pattern to that discovered by Hertwig for cyprinidontiform fishes has also been discovered in cichlids, whose basal members are also distributed in India and Madagascar.
For more details on the phylogeny of cyprinidontiform fishes see the paper: Stefan T. Hertwig. Phylogeny of the Cyprinodontiformes (Teleostei, Atherinomorpha): the contribution of cranial soft tissue characters. Zoologica Scripta (OnlineEarly Articles).
doi:10.1111/j.1463-6409.2007.00314.x