Introduction - An Invariant Approach to Statistical Analysis of Shapes - page 10

spaces that the skull serves to protect and support. Understanding the
complex changes that occur during growth of the skull can explain the
basis for morphological differences observed in adult forms. Inter specif-
ic studies of growth can help us to understand the processes responsible
for the production of characteristic features that we use to recognize
species differences. Since small changes in growth pattern can be
responsible for fairly significant differences in adult form (e.g., Gould,
1977; McKinney and McNamara, 1990; McKinney and McNamara, 1991;
McNamara, 1995), studies of growth can provide novel information
about phylogenetic relationships among more closely related species.
Growth can be studied using longitudinal data where data points
have been collected from a single individual over a period of time.
Growth can also be studied using cross sectional data. Cross sectional
data consist of a group of measures for each age, but each individual is
measured only once so that the sample for an age group does not con-
tain any of the individuals in the previous age group. Both types of data
have their limitations and advantages depending upon the research
question (Eveleth and Tanner, 1976; Tanner, 1989; Bogin, 1999). We deal
exclusively with cross sectional growth data in this volume.
Our cross sectional growth data consist of landmark data collected
from skulls of Macaca fascicularis, the crab-eating macaque. Male and
female skulls from the National Museum of Natural History,
Figure 1.2 Adult Macaca fascicularis skull with the location of 6 facial landmarks shown:
1, nasale; 2, intradentale superior; 3, premaxillary-maxillary junction; 4, zygomaxillare
superior; 5, maxillary tuberosity; 6, posterior nasal spine (located on the sagittal plane).