Life history, enamel formation, and linear enamel hypoplasia in the ceboidea

Elizabeth A. Newell, Elizabethtown College
Debbie Guatelli-Steinberg, The Ohio State University
Michelle Field, Elizabethtown College
Catherine Cooke, Elizabethtown College
Robin N.M. Feeney, Elizabethtown College


Linear enamel hypoplasia (LEH), a developmental defect of enamel, increases in frequency from prosimian to monkey to lesser ape to great ape grades (Guatelli-Steinberg [2000] Am. J. Phys. Anthropol. 112:395-410, [2001] Evol. Anthropol. 10:138-151; Newell [1998] Ph.D. dissertation, Temple University). This taxonomic pattern in the distribution of LEH is closely related to maturation length across the primate order (Newell [1998] Ph.D. dissertation, Temple University, [2000] Am. J. Phys. Anthropol. [Suppl.] 30:236). Longer maturation periods are associated with higher LEH frequencies; they appear to provide greater opportunity for defects to form. The present study explores the relationship between maturation length and LEH frequency within the Ceboidea. Because of its prolonged period of growth, Cebus is predicted to manifest LEH at a higher frequency than the more rapidly maturing ceboid genera. To test this hypothesis, two separate researchers (E.A.N. and D.G.-S.) examined LEH in non-overlapping museum series of ceboids. The results support the hypothesis: in 13 genera (n = 1,276), E.A.N. found that LEH frequencies ranged from 0% in Callicebus, Cebuella, and Saimiri to 20% in Cebus. D.G.-S. found similar frequencies among five genera (n = 107), from 0% in Saimiri to 32% in Cebus. Thus, the broad pattern of LEH distribution evident across major taxonomic groups of primates is repeated within the Ceboidea. We also examined a related hypothesis linking the spacing of perikymata, which is influenced by enamel extension rates (Shellis [1998] J. Hum. Evol. 35:387-400), to LEH. The most likely areas of tooth crowns to exhibit LEH in human teeth are those in which perikymata are most closely spaced (Hillson and Bond [1997] Am. J. Phys. Anthropol. 104:89-103). We hypothesized that the longer-maturing Cebus, with its elevated LEH frequency, will also exhibit more closely spaced perikymata than other ceboids. Analysis of a small microscopic subsample (n = 8) lends limited support to this second hypothesis. © 2006 Wiley-Liss, Inc.