Haile-selassie, Yohannes (PhD)Gebreyesus, Hailay2018-07-052023-11-092018-07-052023-11-092011-09http://10.90.10.223:4000/handle/123456789/6658Members of the Family Suidae (Artiodactyla, Mammalia) are among the most studied in the Plio-Pleistocene vertebrate fossil record of Africa. However, a number of disagreements remain in terms of their taxonomy and phylogenetic relationships. There were also some disagreements in relation to the tempo and mode of evolution of Notochoerus euilus. The contemporaneous presence of both Nyanzachoerus jaegeri and Notochoerus euilus in the Pliocene Woranso-Mille site, Central Afar, Ethiopia, has allowed a better understanding of the phylogenetic relationships between the two taxa. The fossil evidence from the Woranso-Mille indicates that Not.euilus appeared as early as 3.76 Ma and Ny. jaegeri persisted until about 3.72 Ma. This means that both Ny.jaegeri and primitive Not.euilus have co-existed between 3.76-3.72 Ma. Morphological and metric comparisons of the Woranso-Mille Not.euilus specimens with those from the slightly younger Hadar and Koobi Fora localities clearly show that the Woranso-Mille specimens are more primitive. There is now strong evidence for the possibility of a cladistic mode of origin for Not.euilus. However, the cranial and dental morphological similarities still maintain their ancestral-descendant relationships. Furthermore, some workers reassigned Ny.jaegeri into genus Notochoerus based on description of complete mandibles from Kanapoi (KNM-KP 30178 and KNM-KP 30452). However, the argument was not supported by cranial characters, mainly due to the lack of complete crania of Ny. jaegeri. A detailed description and comparison of a newly discovered complete cranium of the species from the Woranso-Mille site suggests that Ny. jaegeri best fits into the genus Nyanzachoerus. Key words: Notochoerus euilus, Nyanzachoerus jaegeri, Woranso-Mille, Ethiopia, Phylogeny, Cladistics.enNotochoerus euilusNyanzachoerus jaegeriWoranso-MilleEthiopiaPhylogenyCladisticsThesis