Paranasal pneumatization in extant and fossil Cercopithecoidea Todd C. Rae Evolutionary Anthropology Research Group, Department of Anthropology, Durham University, 43 Old Elvet, Durham DH1 3HN, UK Received 27 February 2007; accepted 19 July 2007 Abstract Unlike most primates, extant cercopithecoids lack maxillary sinuses, which are pneumatic spaces in the facial skeleton lateral of the nasal cavity proper. Character state analysis of living cercopithecoids across well-supported topologies suggests that the sinus was lost at the origin of the superfamily, only to have evolved again convergently in extant macaques. Recent work has shown that a) the ‘early loss’ hypothesis is supported by the lack of any pneumatization in Victoriapithecus, a stem cercopithecoid, b) like extant macaques, the fossil cercopithecine Para- dolichopithecus shows evidence of presence of the maxillary sinus (MS), and c) unlike extant colobines, the fossil colobine Libypithecus also possesses a maxillary sinus. To more fully assess the pattern of cercopithecoid sinus evolution, fossil taxa from both subfamilies (Colobinae, Cercopithecinae) were examined both visually and by computed tomography (CT). The observations were evaluated according to standard anatomical criteria for defining sinus spaces, and compared with data from all extant Old World monkey genera. Most taxa examined conformed to the pattern already discerned from extant cercopithecoids. Maxillary sinus absence in Theropithecus oswaldi, Mesopithecus, and Rhinocolobus is typical for all extant cercopithecids except Macaca. The fossil macaque Macaca majori possesses a well-developed maxillary sinus, as do all living species of the genus. Cercopithecoides, on the other hand, differs from all extant colobines in possessing a maxillary sinus. Thus, paranasal pneumatization has reemerged a minimum of two and possibly three times in cercopithecoids. The results suggest that maxillary sinus absence in cercopithecoids is due to suppression, rather than complete loss. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Old World monkeys; Paranasal sinuses; Craniofacial evolution Introduction The crania of many vertebrates contain pneumatic struc- tures, the paranasal sinuses, that communicate with the nasal cavity proper. The bony signatures of these epithelial out- growths of the nasal capsule consist of either indentations on the external surface of the craniofacial skeleton in archosaurs or enclosed bony cul-de-sacs in mammals (Witmer, 1999). This type of craniofacial pneumatization is a significant con- tributor to the architecture of the skull and features in discus- sions of the phylogeny, functional anatomy and physiology of many vertebrate groups. There are four recognized paranasal sinuses in the order Primates: the maxillary, sphenoidal, ethmoidal, and frontal sinuses (Cave and Haines, 1940; Negus, 1958). Although the terminology and definitions of these are currently under debate (Rossie, 2006), the traditional arrangement is that the sinuses are identified by the position of their opening (or ostium) into the nasal cavity, and are named after the bone that they most commonly pneumatize (Negus, 1958). Although there is con- siderable variation across mammalian groups, at least the max- illary sinus is thought to have been present in the last common ancestor of Eutheria (Novacek, 1993). Although craniofacial pneumatization in tarsiers and strep- sirrhines is not documented to the same extent, the presence of individual sinuses (and, in some cases, their relative size) is known for extant anthropoid primates (Paulli, 1900; Cave and Haines, 1940; Lund, 1988). For example, extant Hominoi- dea are characterized by between two and four of the sinuses (Cave and Haines, 1940) and there is no substantive variation (independent of body size) in the volume of the maxillary sinus E-mail address: t.c.rae@durham.ac.uk 0047-2484/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jhevol.2007.07.010 Available online at www.sciencedirect.com Journal of Human Evolution 54 (2008) 279e286