Cichlidist's Library: 'A phyletic study of the Lake Tanganyika cichlid genera Asprotilapia, Ectodus, Lestradea, Cunningtonia, Ophthalmochromis and Ophthalmotilapia'

" Liem, K.F. 1981. A phyletic study of the Lake Tanganyika cichlid genera Asprotilapia, Ectodus, Lestradea, Cunningtonia, Ophthalmochromis and Ophthalmotilapia. Bulletin of the Museum of Comparative Zoology. 149(3):191-214.

Abstract
On the basis of comparative osteology and myology, Asprotilapia, Ectodus, Lestradea, Cunningtonia, Ophthalmochromis, and Ophthalmotilapia of Lake Tanganyika are hypothesized to be members of a monophyletic lineage of cichlid fishes. All members share the following suite of characters:
(1) the entopterygoid is widely separated from the palatine;
(2) the posterior and dorsal margins of the palatine form a 90° angle;
(3) the slender hyomandibula has a long symplectic process and a very reduced hyomandibular flange;
(4) the anterior margin of the petrosphenoid is notched;
(5) the vertical depth of the metapterygoid is shallow;
(6) the operculum has a distinct auricular process;
(7) the transversus dorsalis muscle is reduced; and (8) the obliquus posterior muscle is enlarged.
These characters are considered specialized when compared with the accepted generalized morphology of Astatotilapia. The phyletic relationship of this lineage are documented by synapomorphies that distinguish subunits of decreasing levels of universality within the assemblage. Asprotilapia represents a highly specialized branch with six major skeletomuscular specializations. The remaining five genera are pictured as a second lineage, of which Ectodus is the most generalized taxon. On the basis of recency of common descent, Ophthalmochromis is synonymized with the genus Ophthalmotilapia. Although there is no doubt that the Ophthalmotilapia lineage has undergone extensive morphological radiation in both skull structure and dentition, the data on morphology, function, trophic ecology, and behavior of this and other cichlid lineages have failed to establish unequivocally that the morphological radiation is also adaptive. The morphological and functional pattern in this lineage reinforces the paradox that morphologically and phylogenetically most specialized cichlid taxa are not only remarkable specialists but also jacks-of-all-trades "