The primate cranial base: ontogeny, function and - Harvard University

118 YEARBOOK OF PHYSICAL ANTHROPOLOGY [Vol. 43, 2000
Brain volume and posterior cranial fossa shape .......................................................... 138
Associations Between Cranial Base and Face .................................................................. 138
Anterior cranial fossa shape and upper facial growth ................................................. 138
Middle cranial fossa shape and midfacial growth ........................................................ 140
Basicranial width and overall facial shape in humans ................................................ 144
The Cranial Base and Posture ........................................................................................... 148
Major Unresolved Issues of Cranial Base Variation in Primate Evolution ................... 151
Primate origins, encephalization, and circumorbital form .......................................... 151
Anthropoid origins and cranial base-face interactions ................................................. 152
Variation in hominin cranial base angle ....................................................................... 153
Cranial base flexion and vocal tract shape in hominins .............................................. 154
Cranial base shape and facial projection in Homo ....................................................... 156
Cranial base characters in phylogenetic analyses ........................................................ 158
Conclusions .......................................................................................................................... 159
What major factors generate variation in the cranial base? ....................................... 160
What role does the cranial base play in craniofacial integration? .............................. 160
Correlation ................................................................................................................... 161
Constraint .................................................................................................................... 162
Ontogenetic sequence .................................................................................................. 162
Future research ............................................................................................................... 163
Acknowledgments ............................................................................................................... 163
Literature Cited .................................................................................................................. 163
GLOSSARY
Basioccipital clivus: midline “plane” of the
posterior cranial base formed by the superior
(endocranial) aspects of the basioccipital
and the posterior sphenoid.
Brain stem: the ventral parts of the brain,
excluding the telencephalon. Specifically, in
this paper, the brain stem consists of the
medulla oblongata and mesencephalon (
optic tectum and tegmentum) of Stephan et
al. (1981; see also Butler and Hodos, 1996).
Chondrocranium: cartilaginous precursors
to the basicranium.
Constraint: a limitation or bias on processes
and/or patterns of evolution, growth, form,
and function.
Cranial base angulation: a series of events
by which bone or cartilage deposition in the
midline cranial base changes the angle between
intersecting prechordal (see below)
and postchordal (see below) lines. This causes
the inferior cranial base angle to become more
acute (flexion) or more obtuse (extension).
Displacement: a series of events by which
an osseous region “moves” relative to another
osseous region through bone deposition
(primary displacement), or through
bone deposition in an adjoining bone (secondary
displacement).
Drift: a series of events by which an osseous
wall “moves” relative to another anatomical
region through bone deposition on one surface
and bone resorption on its opposing
surface.
Ethmomaxillary complex: the upper part of
the face, mostly comprising the ethmoid, the
nasal capsule, and the maxilla.
Facial projection: degree to which face
projects in front of cranial base; measured
here by nasion-foramen caecum.
Integration: the genetic, epigenetic, or functional
association among elements via “a set
causal mechanisms so that change in one
element is reflected by change in another”
(Smith, 1996). The results of integration are
most often recognized as a pattern of significant,
hierarchical covariation among the
components of a system.
Kyphosis: angle of some aspect of facial orientation
relative to the neuro- and/or basicranium,
measured here using angle of facial
kyphosis (AFK) for the orientation of
the palate, and angle of orbit axis orientation
(AOA) for orientation of the orbital axis.
Planum sphenoideum: midline “plane” of
the anterior cranial base from the sphenoidale
(Sp) to the planum sphenoideum (PS)
point (see below).