Growth changes in internal and craniofacial flexion measurements

Abstract

Growth changes in both internal and craniofacial flexion angles are presented for Pan troglodytes, Gorilla gorilla, and modern humans. The internal flexion angle (IFA) was measured from lateral radiographs, and the craniofacial flexion angle (CFA) was calculated from coordinate data. Stage of dental development is used as a baseline for examination of growth changes and nonparametric correlations between flexion angles and dental development stage are tested for significance. In Gorilla, the IFA increases during growth. The IFA is relatively stable in Pan and modern humans. Pan and Gorilla display an increase in the CFA. However, this angle decreases during growth in modern humans. Flexion angles were derived from coordinate data collected for several early hominid crania. Measurements for two robust australopithecine crania indicate strong internal flexion. It has been suggested that cerebellar expansion in this group may relate to derived features of the posterior cranial base. In general, australopithecine crania exhibit craniofacial flexion intermediate between great apes and modern humans. The "archaic" Homo sapiens specimen from Kabwe is most similar to modern humans.

Exploring artificial cranial deformation using elliptic Fourier analysis of procrustes aligned outlines

“…One reason, however, is that our results are not directly comparable to preceding studies, because we measured the relative flatness of the basioccipital, the foramen magnum , and the nuchal plane, whereas previous reports focused on the basicranial flexion. One has to keep in mind that the orientation of the clivus (relevant for measures of basicranial flexion) may only loosely affect the angle formed by the basioccipital and the foramen magnum (May and Sheffer, 1999), although some degree of relatedness seems inherent. However, even the studies that measured the clivoforaminal angle reported differences compared to undeformed and/or AP deformed crania.…”

“…Ross and Henneberg (1995), Ross and Ravosa (1993). May and Sheffer (1999) claimed that internal and external measures are uncorrelated. In this study, we used the orientation of the external basioccipital relative to the axis of the foramen magnum as an expression of basioccipital flatness, without inferring any strict relationship to internal or anterior cranial base measurements.…”

A comparative analysis of internal cranial anatomy in the hylobatidae

“…The degree of posterior skull base flexion (relative to the anterior skull base) has been hypothesized to be correlated with orbital and facial orientation, brain volume, and posture across primates (e.g., Ross and Ravosa, 1993; Ross and Henneberg, 1995; Strait and Ross, 1999), but these hypotheses are not further tested here. The PCB is typically represented in one of two ways: either as midline construction drawn from basion to a variation of sella (e.g., Dmoch, 1975; Michejda, 1975; George, 1978; May and Sheffer, 1999); or, as a midline tangent anchored at basion and fit to the endocranial surface of the basioccipital clivus (e.g., Hofer, 1952; Biegert, 1957; Angst, 1967; Ross and Ravosa, 1993). The former construction is used in this investigation and is identified as the PCB1 plane (see Fig.…”