The New World Monkeys: The Dwarfing Hypothesis
THE NEW WORLD MONKEYS: THE DWARFING HYPOTHESIS
Introduction I will consider support for the dwarfing hypothesis in New World monkeys. Since evolution has shown to result in a general increase in body size, the case of reduced body size in the New World primates is quite unusual. To explain the phenomenon, the dwarfing hypothesis has been proposed (Martin, 1992). The dwarfing hypothesis implies that there must have been selective pressure that favored a reduction in body size. Phyletic dwarfing is then presumed to be fundamental to the further development of the species ' characters (Martin, 1992). Callitrichids are not the only primates that are thought to have undergone phyletic dwarfing. For example, there are also dwarf lemurs and dwarf bushbabies (Martin, 1990). I will consider the dwarfing hypothesis in the context of analyzing whether the morphological features of the callitrichids are primitive or derived. Although the callitrichids have many common features (including twinning, small body size, reduction of the molar tooth row, simplification of the upper molars, and claws) in this paper I will focus on the morphological features: body size, claws and the dental features of the Callitrichidae (twinning is an important common character of the callitrichids, but will not be considered here). One important hindrance to finding support for the dwarfing hypothesis has been gaps in the fossil record. However, using the available fossil data and modern studies of callitrichids I will show why each feature is primitive or derived, and how it applies to the dwarfing hypothesis.
The New World Monkeys The New World monkeys (Platyrrhines) can be divided into two families: the Cebidae and the Callitrichidae (the Callimico is also a Platyrrhine and shares many of the characteristics of the callichitrids, but the position of the Callimico within the Platyrrhines will not be considered here). The Callitrichidae family includes the marmosets and the
Introduction I will consider support for the dwarfing hypothesis in New World monkeys. Since evolution has shown to result in a general increase in body size, the case of reduced body size in the New World primates is quite unusual. To explain the phenomenon, the dwarfing hypothesis has been proposed (Martin, 1992). The dwarfing hypothesis implies that there must have been selective pressure that favored a reduction in body size. Phyletic dwarfing is then presumed to be fundamental to the further development of the species ' characters (Martin, 1992). Callitrichids are not the only primates that are thought to have undergone phyletic dwarfing. For example, there are also dwarf lemurs and dwarf bushbabies (Martin, 1990). I will consider the dwarfing hypothesis in the context of analyzing whether the morphological features of the callitrichids are primitive or derived. Although the callitrichids have many common features (including twinning, small body size, reduction of the molar tooth row, simplification of the upper molars, and claws) in this paper I will focus on the morphological features: body size, claws and the dental features of the Callitrichidae (twinning is an important common character of the callitrichids, but will not be considered here). One important hindrance to finding support for the dwarfing hypothesis has been gaps in the fossil record. However, using the available fossil data and modern studies of callitrichids I will show why each feature is primitive or derived, and how it applies to the dwarfing hypothesis.
The New World Monkeys The New World monkeys (Platyrrhines) can be divided into two families: the Cebidae and the Callitrichidae (the Callimico is also a Platyrrhine and shares many of the characteristics of the callichitrids, but the position of the Callimico within the Platyrrhines will not be considered here). The Callitrichidae family includes the marmosets and the
References: Ford, S.M. (1980). Callitrichids as phyletic dwarfs, and the place of the Callitrichidae in Platyrrhini. Primates 21, 31-43 Martin, R.D. (1992). Goeldi and the dwarfs: the evolutionary biology of the small New World monkeys. Journal of Human Evolution (1992) 22, 367-393 Sussman, R.W., Kinzey, W.G. (1984). The ecological role of the Callitrichidae: a review. American Journal of Physical Anthropology. 64, 419-449 Rosenberger, A.L. (1977). Xenothrix and ceboid phylogeny. Journal of Human Evolution. 6, 461-481