Craniofacial growth in fetal Tarsius bancanus: brains, eyes and nasal septa

Abstract

The tarsier skull has been of particular interest in studies of primate taxonomy and functional morphology for several decades. Despite this, there remains no comprehensive data on how the tarsier skull develops, especially in relation to the soft-tissues of the head. Here we have documented for the first time fetal development of the skull and brain as well as the nasal septum and eyes in T. bancanus . We have also tested for the possible influence of these tissues in shaping skull architecture. Nineteen post-mortem specimens were imaged using high-resolution magnetic resonance imaging and magnetic resonance microscopy. Landmarks and volume data were collected and analysed. Findings demonstrated massive increases of brain size and eye size as well as flattening of the midline cranial base, facial projection and orbital margin frontation. Little evidence was found to support the notion that growth of the brain or nasal septum physically drives the observed changes of the skull. However, increases in the size of the eyes relative to skull size were associated with orbital margin frontation. With the possible exception of the results for eye size, the findings indicate that rather than forcing change the soft-tissues form a framework that physically constrains the morphogenetic template of the skeletal elements. This suggests, for example, that the degree of cranial base angulation seen in adulthood is not directly determined by brain expansion bending the basicranium, but by brain enlargement limiting the extent of cranial base flattening (retroflexion) in the fetus.

Prenatal ontogeny of subspecific variation in the craniofacial morphology of the Japanese macaque (Macaca fuscata)

“…5e, 6). In the fetal ontogeny of the tarsier, pigtailed macaque, and howler monkey, the CBA is reported to retroflex (Jeffery 2003;Jeffery et al 2007). The same trend is also observed in modern human fetuses (Kvinnsland 1971;Jeffery andSpoor 2002, 2004;Morimoto et al 2008).…”

Biological spacetime and the temporal integration of functional modules: A case study of dento–gnathic developmental timing

“…As such, for better or for worse, developmental perturbations in a given module (i.e., cell population or tissue) can have significant downstream impacts on counterpart modules. A well-established example of this is the influence of brain growth and cranial base length and flexure on adult craniofacial shape (Lieberman et al, 2000a,b;Richtsmeier et al, 2006;Hallgrímsson et al, 2007b;Jeffery et al, 2007). In terms of development, integration of developmental architectures may offer an economy of process, but with latent high costs to the individual organism: should a critical component go awry, the phenotypic effect can be lethal.…”

Nasal Septum Morphology in Unilateral and Bilateral Cleft Lip and Palate Determined by 3D Cephalometry

“…They found that the effects decreased as the distance from the maxilla increased, and that there were almost no effects near the cranial base. Jeffery et al 12 reported that tarsier skulls do not adequately re ect this concept. Our study suggested that clefts only reach the cranial base at the point where the superior edge of the vomer fuses to the posterior portion of the cranial base.…”