Development and Three-Dimensional Morphology of the Zygomaticotemporal Suture in Primate Skulls

Abstract

Cranial sutures are an essential part of the growing skull, allowing bones to increase in size during growth, with their morphology widely believed to be dictated by the forces and displacements that they experience. The zygomaticotemporal suture in primates is located in the relatively weak zygomatic arch, and externally it appears a very simple connection. However, large forces are almost certainly transmitted across this suture, suggesting that it requires some level of stability while also allowing controlled movements under high loading. Here we examine the 2- and 3-dimensional (3D) morphology of the zygomaticotemporal suture in an ontogenetic series of Macaca fascicularis skulls. High resolution microcomputed tomography data sets were examined, and virtual and physical 3D replicas were created to assess both structure and general stability. The zygomaticotemporal suture is much more complex than its external appearance suggests, with interlocking facets between the adjacent zygomatic and temporal bones. It appears as if some movement is permitted across the suture in younger animals, but as they approach adulthood the complexity of the suture's interlocking bone facets reaches a level where these movements become minimal.

Beyond the functional matrix hypothesis: a network null model of human skull growth for the formation of bone articulations

“…In addition, external forces and movements related to functional matrices influence the internal complexity of sutures (Curtis et al. ).…”

“…Other epigenetic factors that affect the formation of sutures include hormonal signals (Karsenty, 1999) and biomechanical mechanisms (Shwartz et al 2012;Khonsari et al 2013). In addition, external forces and movements related to functional matrices influence the internal complexity of sutures (Curtis et al 2014).…”

Stem members of Platyrrhini are distinct from catarrhines in at least one derived cranial feature

“…Our objective in this process was to identify continuous surfaces of bone. Similar approaches have been taken in investigations of the cranial osteology in fossils in the past (Curtis et al, 2014;Krause et al, 2014). At least three orthogonal views were taken as necessary to distinguish between postmortem breaks and actual sutures.…”

“…To help clarify the interpretation of the fossil evidence, we reassess pterion pattern in the fossil platyrrhines Dolichocebus, Homunculus, Tremacebus, and Antillothrix and the North African anthropoids Simonsius and Proteopithecus through the use of μCT (micro-computed tomography) scans of crania from each taxon. μCT has proven useful in detecting differences in texture and internal structure in fossil material that may not be visible through external examination (Ketcham and Carlson, 2001;Tafforeau et al, 2006;Scherf, 2013;Weber, 2015), including in the tracing of sutural boundaries and evaluation of suture patency in primates (Reinholt et al, 2009;Curtis et al, 2014) This technique may allow more reliable determination of the pattern of pterion contact in these important taxa. We incorporate new information provided by this approach into a phylogenetic analysis of platyrrhine relationships and an ancestral state reconstruction of the pterion configuration at the last common ancestors of platyrrhines and haplorhines, respectively.…”

A comparison of metrics for quantifying cranial suture complexity

“…When comparing suture to suture, those in the facial region have been reported to have straight morphologies compared to the interdigitated sutures of the braincase [ 30 ]. Looking across development, sutures have been suggested to progress from straight to highly interdigitated morphologies [ 31 ]. Sexual dimorphism of sutures has also been identified, with males exhibiting greater levels of complexity for facial sutures, thought to reflect the pressures of head-to-head fighting [ 32 ].…”