Off-campus UMass Amherst users: To download dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.
Non-UMass Amherst users, please click the view more button below to purchase a copy of this dissertation from Proquest.
(Some titles may also be available free of charge in our Open Access Dissertation Collection, so please check there first.)
Cranial morphology, systematics, and evolution of neogene Tayassuidae (Mammalia)
I investigated cranial and dental morphology in 37 species of fossil and living peccaries, Family Tayassuidae, from North and South America. PAUP analysis of 94 apomorphous character states among 33 species represented by adequate samples produced a set of trees (C.I. = 0.74) which unequivocally support the monophyly of several clades within the Tayassuidae. The subfamily Tayassuinae comprises the three living species of peccary and 23 Miocene and younger species. The Miocene taxa Hesperhys, "Thinohyus" siouxensis, Floridachoerus, "Cynorca" sociale, and two unnamed species form a clade which is the sister group of the Tayassuinae. The Oligocene species Perchoerus probus is the sister group of the clade comprising Hesperhys and the Tayassuinae; another Oligocene species, Thinohyus lentus, is the sister group of all tayassuids surveyed. Analysis of a set of predominantly tayassuine taxa yielded a set of trees (C.I. = 0.84) which resolve relationships among several tayassuine clades. Tayassu is the sister group of a clade comprising Prosthennops (restricted to P. serus), Mylohyus, and Platygonus. Catagonus and Dicotyles are sister groups, and together form a clade which is the sister group of the clade which unites Tayassu and Platygonus. Progressively distant sister groups of that clade include three unnamed Miocene species, Macrogenis, "Prosthennops" xiphidonticus, "Prosthennops" niobrarensis, "Cynorca" occidentale, and Dyseohyus.^ Miocene and younger tayassuids possess within their nasal cavities an elaborate complex of bony structures that is unique among mammals. The floor of the nasal cavity is developed into a pneumatic, labyrinthine structure. The vomer is also pneumatic, and is developed into a pair of large, bilaterally symmetrical chambers. Many members of the clade of late Miocene and younger tayassuines that includes Macrogenis and its sister taxa have wing-like zygomatic processes; possession of these processes is primitive for that clade. Primitively both sexes (diagnosed by discretely bimodal canine diameters) possessed them, but they are sexually dimorphic in some species of Platygonus. Zygomatic processes were reduced in size in as many as five clades; their reduction was accompanied by reduction in the degree of canine dimorphism. A minimum of four dispersal events is required to account for the diversity of South American Tayassuidae. ^
David Brian Wright,
"Cranial morphology, systematics, and evolution of neogene Tayassuidae (Mammalia)"
(January 1, 1991).
Electronic Doctoral Dissertations for UMass Amherst.