The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)

Facial shape in trigonocephaly: a metric and geometric morphometric assessment


1Integrative Biology, UC Berkeley, 2Anthropology, CSU Chico, 3Molecular and Cell Biology, UC Berkeley, 4Biology, St. Mary's College, 5Biomedical Sciences, A.A. Dugoni School of Dentistry, University of the Pacific

March 27, 2015 , Archview Ballroom Add to calendar

Archaeologically, individuals with prematurely fused sutures are plentiful, excepting those with trigonocephaly. When coupled with the fact that clinical descriptions are limited to late fetal-early postnatal stages, this leaves knowledge of later-stage growth changes unknown. We hypothesize that shape changes seen in the face of trigonocephalics are driven by anterior brainmalformations and that with growth this results in a cascading series of morphological changes in the face that spare the nasal capsule.

A trigonocephalic skull deriving from Santa Rosa Island (CA-SRI-24: 1500-1650 AD) and housed at UC Berkeley (PHMA) was compared to 35 skulls from the Institute for Craniofacial Study, UOP. Developmental ages of 8.0 years and 6.0-8.0 years±24 months were assessed for the trigonocephalic and normal skulls, respectively. Landmark data comprise 93 points collected from normal skulls with a Microscribe 3D digitizer and from a CT scan of the trigonocephalic using Amira 5.5.Facial shape was explored using Principal Components Analysis on Procrustes-aligned shape variables.

Metric and geometric morphometric analyses confirm that thenasal capsule is essentially normal. Alternatively, significant narrowing and wedging of the frontal result in increased frontal and orbital heights, demonstrating compensatory changes in theanterior cranial fossa and lateral face, respectively. Upper facialelongation is associated with an increased breadth of the lower face, while lower face length shows only slight involvement.Causative factors resulting in trigonocephaly are obscure.Consideration of endocranial shape, along with the resultsabove, supports suggestions that brain malformations mayunderlie the complex trigonocephalic phenotype.