Morphological diversity of the genus Telmatochromis from the Lake Tanganyika drainage with the description of a new riverine species and the generic reassignment of the Malagarasi River lamprologine.

The lamprologine cichlid genus Telmatochromis was long considered primarily lacustrine and endemic to Lake Tanganyika until an undescribed Telmatochromis species was reported from the Lufubu River (Lake Tanganyika drainage, Zambia). A phylogenomic study in 2021 confirmed the association of Telmatochromis sp. "lufubu" with Telmatochromis along with another riverine species, Neolamprologus devosi (Malagarasi drainage, Tanzania). Here, we quantify the morphological diversity of the genus Telmatochromis and the two associated riverine species using a multivariate dataset combining geometric and classical morphometrics, as well as meristics. We identify three distinct morphological clusters: the "Telmatochromis vittatus complex" with highly elongated bodies and short heads, the "Telmatochromis temporalis complex" with deeper bodies, and the two riverine species with intermediate body elongation and large heads. Further, we formally describe the species endemic to the lower Lufubu River as Telmatochromis salzburgeri sp. nov. and reassign N. devosi to Telmatochromis. Telmatochromis devosi comb. nov. differs from all congeners by the absence of bi- and tricuspid teeth in the inner tooth rows of the oral dentition. T. salzburgeri sp. nov. can be distinguished from all other Telmatochromis species by a prominent orange stripe along the base of the dorsal fin and from T. devosi comb. nov. by the relatively smaller size of the lower pharyngeal jaw. Both riverine species differ from all lacustrine Telmatochromis by a lower number of dorsal-fin spines. Additionally, the riverine species can be distinguished from the T. vittatus complex by having larger heads and longer oral jaws, and from the T. temporalis complex by their lower relative body depth. With the inclusion of new riverine members, the genus Telmatochromis is revealed to be more morphologically and ecologically diverse than previously recognized.