Epiphyseal Fusion in Pan troglodytes Relative to Dental Age Conrad S. Brimacombe,* Kevin L. Kuykendall, and Pia Nystrom Department of Archaeology, University of Sheffield, Sheffield, South Yorkshire S1 4ET, UK KEY WORDS epiphyseal fusion; developmental sequences; chimpanzee; Pan troglodytes ABSTRACT Previous studies on different aspects of chimpanzee growth and development have documented dental eruption and development, long bone and somatic growth, and to a lesser extent, skeletal fusion. Such data are useful in comparative and evolutionary studies of growth and some aspects of life history evolution in apes and early hominids. However, few studies have integrated dental development and other aspects of skel- etal development, and none of these have been able to incorporate a large study sample. This study documents dental mineralization and skeletal epiphyseal fusion in a mixed-sex sample of 155 Pan troglodytes skeletons, and aims to: a) document the pattern of dental and skeletal developmental in chimpanzees; b) compare male and female developmental patterns in chimpanzees; and c) compare these chimpanzee developmental patterns to general patterns of dental and skeletal development in published human studies. The analysis of both dental and skeletal development in this sample demonstrates clearly that dental development is complete before the fusion of the many skeletal epiphyses, in contrast to the pattern observed in humans. Age estimates for individu- als were calculated using previously published regres- sion equations for dental development and used to estimate fusion ages. These appear to be accurate in that our estimates are similar to published ranges. These data improve our understanding about chimpan- zee dental and skeletal development and provide a basis for further comparison between extant apes and humans, as well as those extinct species represented by fossil partial skeletons. Am J Phys Anthropol 000:000– 000, 2014. V C 2014 Wiley Periodicals, Inc. Research about ontogenetic aspects of skeletal and dental biology in extant apes has a long history (Krog- man, 1930; Schultz, 1940; Simpson et al., 1990; Anem- one et al., 1991; Zihlman et al., 2007, among others), and is relevant to questions about comparative growth (Leigh, 2001; Cobb and O’Higgins, 2004), sexual dimor- phism (Shea, 1985, 1986), and evolution (Conroy and Kuykendall, 1995; Dean and Lucas, 2009; Dean and Smith, 2009). Previous studies of skeletal and dental development in chimpanzees have usually focused indi- vidually on features such as dental emergence or stages of dental mineralization (e.g., Anemone et al., 1991, 1996; Kuykendall et al., 1992; Kuykendall and Conroy, 1996; Kuykendall, 1996) epiphyseal fusion (e.g., Hamada et al., 1998; Hamada and Chatani, 2003; Zihlman et al., 2007; Bolter and Zihlman, 2012), or growth in long-bone length (e.g., Shea, 1983, 1984, 1985), but few have stud- ied both dental and skeletal growth or maturity in the same study samples (but see Zihlman et al., 2007). In an ideal comparative study, it would be possible to docu- ment both the chronological ages at which developmen- tal events are attained and the relative developmental patterns both within and between dental and skeletal variables of different species. However, this would require access to large known-age skeletal samples that are simply not available for most nonhuman primates. Even in human studies involving large samples, the parameters for assessing skeletal development are often restricted to single regions with clinical application in age assessment such as hand-wrist or cervical vertebrae (e.g., Krailassiri et al., 2002; Usal et al., 2004; Chen et al., 2010). Dental development has been well-documented in Pan troglodytes (e.g., Anemone et al., 1991, 1996; Kuykendall et al., 1992; Kuykendall and Conroy, 1996; Kuykendall, 1996) and we currently have a good basic understanding of both the pattern and timing of chimpanzee dental development. Perhaps, the most notable difference in chimpanzee and human growth and development is that the schedule in humans extends to 20 or more years, while chimpanzees are generally skeletally and dentally mature at about 12 years of age (Kuykendall, 1996; Dean, 2006; Zihlman et al., 2007). Within this develop- mental timeframe, differences in the dental developmen- tal pattern between species have been characterized in general terms as a delay in anterior tooth development relative to the M1 in chimpanzees, and a progressive delay in crown initiation between successive molar teeth in humans, sometimes involving agenesis of the M3 (Anemone et al., 1996; Kuykendall, 1996; Dean, 2006). Prior studies of epiphyseal fusion in Pan troglodytes include Schultz, 1940; Kerley, 1966; Watts, 1993; Ham- ada and Chatani, 2003; Zihlman et al., 2007; Bolter and Zihlman, 2012. A number of studies have focused on the wrist (e.g., Nissen and Riesen, 1949a,b; Hamada et al., Grant sponsor: Primate Society of Great Britain Charles A. Lock- wood Memorial Grant 2010. *Correspondence to: Conrad Stephen Brimacombe, Department of Archaeology, University of Sheffield, Northgate House, West Street, Sheffield S1 4ET, United Kingdom. E-mail: ConradBrimacombe@ gmail.com Received 6 April 2014; revised 13 November 2014; accepted 2 December 2014 DOI: 10.1002/ajpa.22684 Published online 00 Month 2014 in Wiley Online Library (wileyonlinelibrary.com). Ó 2014 WILEY PERIODICALS, INC. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 00:00–00 (2014)