Impact of increased character sampling on the phylogeny of Cetartiodactyla (Mammalia): combined analysis including fossils

Abstract

The phylogenetic position of Cetacea (whales, dolphins and porpoises) is an important exemplar problem for combined data parsimony analyses because the clade is ancient and includes many well-known and relatively complete fossil species. We combined data for 71 terminal taxa (43 extinct/28 extant) to test where Cetacea fits within Cetartiodactyla, and where various fossil hoofed mammals (e.g., †entelodonts, "†anthracotheriids" and †mesonychians) are positioned. We scored 635 phenotypic characters (osteology, dentition, soft tissue, behavior), approximately three times the number of characters in the last major analysis of this clade, and combined these with > 40 000 molecular characters, including new data from 10 genes. The analysis supported a topology consistent with the majority of recently published molecular studies. Cetacea was the extant sister taxon of Hippopotamidae, followed successively by Ruminantia, Suina and Camelidae. Several extinct taxa were phylogenetically unstable, upsetting resolution of the strict consensus and limiting branch support, but the positions of several key fossils were consistently resolved. The wholly extinct †Mesonychia was more closely related to Cetacea than was any "artiodactylan.""†Anthracotheriids" were paraphyletic, and, with the exception of one species, were more closely related to Hippopotamidae than to any other living taxon. The total evidence analysis overturned a highly nested position for Moschus supported by molecular data a…