Allometry and sexual dimorphism in the primate innominate bone

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Abstract
Allometric growth in the innominate bone has been studied in eight primate taxa. A total of 266 skeletons were examined and the lengths of the ischial and pubic rami of the right innominate bone and the bicondylar length of the right femur were measured. These data were converted to natural logarithms and the allometric relationships were studied. The taxa could be divided into two groups on the basis of the allometric coefficients.Slopes were similar in Homo, Colobus, Presbtis, and Ceropithecus; in these taxa mean ischial length was greater in male skeletons but pubic length showed either no significant increase in the larger males or mean pubic length was greater in the smaller female skeletons.A second group of taxa, Gorilla, Pan, Papio and Cerecocebus all showed a similar pattern of allometric coefficints, a pattern which contrasted with those in Homo etc. Ischial and pubic length in the second group increased in the larger males but the rate of increase in ischial length always exceeded the rate of increase in pubic length. The net effect of these two different mechanisms is to produce sexual differences in the “ischium‐pubic” index, but in the first group of taxa, which show selective pubic growth in the female, sexual dimorphism in the index is greater. Concentration in earlier studies on the “ischium‐pubic” index to study sexual differences in innominate growth have masked these relative growth differences.