Correlation of Reproductive and Digestive Strategies in the Evolution of Cranial Appendages
Cranial appendages are characteristic of most living and fossil pecoran genera, where they consist of bony outgrowths from the skull that may or may not be covered by skin or keratin. Cranial appendages have also evolved in other ungulate lineages: as bony protruberances from the head [in the extinct families Uintatheriidae (order Dinocerata) Brontotheriidae (Perrisodactyla), and Protoceratidae (Artiodactyla], or as dermal structures (in the Rhinocerotidae). Fossil record evidence shows that bony cranial appendages have also arisen in certain taxa in other families; for example, in the Suidae (Kubanochoerus), in the Rhinocerotidae (Diceratherium and Menoceras), in the Merycoidondontidae (Cyclopideus), and even in the Rodentia (Mylagaulus). Bony cranial appendages are also found in certain dinosaurs, most notably in the Ceratopsia. In addition, other ungulate lineages have modified canine or incisor teeth into enlarged tusks, which may function in an analogous fashion to outgrowths from the skull; this is apparent in the Elephantidae (and also in extinct proboscidean families), the Suidae, the Tragulidae (and in other extinct traguloid families), and to a less pronounced extent in the Equidae, Tapiriidae, Camelidae, Procaviidae (Hyracoidea), Tayassuidae, and Hippopotamidae (Kiltie 1985).
KeywordsCellulose Migration Fermentation Europe Cretaceous
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