Timing of ectocranial suture activity in Pan troglodytes as related to cranial volume and dental eruption.

Research has shown that Pan and Homo have similar ectocranial suture synostosis patterns possibly because of their phylogenetic relationship. However, unlike human data, it is unclear if the ontogeny of suture activity for Pan exhibits a relationship with the expanding neurocranium or the masticatory apparatus. These relationships were assessed by examining the associations between ectocranial suture status and morphology and cranial volume (as a proxy for neurocranial expansion) and dental development (as an indicator of adulthood and proxy for masticatory influence) in a large sample of Pan troglodytes skulls. One hundred and fifty-five P. troglodytes dry skulls were examined, and data were collected on ectocranial suture closure status, cranial volume, and dental eruption status. Regression models were calculated for suture status by cranial volumes, and Kendall's tau (a nonparametric measure of association) was calculated for suture status by dental eruption status. Results suggest that suture synostosis activity in P. troglodytes exhibits a period of stasis after neurocranial expansion cessation and does not have a strong relationship with brain development (r(2) ranged from 0.09 to 0.28), as similarly seen in Homo. Instead, suture synostosis has a stronger relationship with dental development (tau ranged from 0.59 to 0.72), where most osseous activity occurs after full adult dental eruption. This suggests that masticatory forces may influence both ectocranial suture morphology and synostosis more than brain expansion does in Pan, as also similarly noted in Homo.

Cray J Jr ，Mooney MP ，Siegel MI 《-》

Timing of ectocranial suture activity in Gorilla gorilla as related to cranial volume and dental eruption.

Research has shown that Pan and Homo have similar ectocranial suture synostosis patterns and a similar suture ontogeny (relative timing of suture fusion during the species ontogeny). This ontogeny includes patency during and after neurocranial expansion with a delayed bony response associated with adaptation to biomechanical forces generated by mastication. Here we investigate these relationships for Gorilla by examining the association among ectocranial suture morphology, cranial volume (as a proxy for neurocranial expansion) and dental development (as a proxy for the length of time that it has been masticating hard foods and exerting such strains on the cranial vault) in a large sample of Gorilla gorilla skulls. Two-hundred and fifty-five Gorilla gorilla skulls were examined for ectocranial suture closure status, cranial volume and dental eruption. Regression models were calculated for cranial volumes by suture activity, and Kendall's tau (a non-parametric measure of association) was calculated for dental eruption status by suture activity. Results suggest that, as reported for Pan and Homo, neurocranial expansion precedes suture synostosis activity. Here, Gorilla was shown to have a strong relationship between dental development and suture activity (synostosis). These data are suggestive of suture fusion extending further into ontogeny than brain expansion, similar to Homo and Pan. This finding allows for the possibility that masticatory forces influence ectocranial suture morphology.

Cray J Jr ，Cooper GM ，Mooney MP ，Siegel MI ... -  《-》

Ectocranial suture closure in Pan troglodytes and Gorilla gorilla: pattern and phylogeny.

The order in which ectocranial sutures undergo fusion displays species-specific variation among primates. However, the precise relationship between suture closure and phylogenetic affinities is poorly understood. In this study, we used Guttman Scaling to determine if the modal progression of suture closure differs among Homo sapiens, Pan troglodytes, and Gorilla gorilla. Because DNA sequence homologies strongly suggest that P. troglodytes and Homo sapiens share a more recent common ancestor than either does with G. gorilla, we hypothesized that this phylogenetic relationship would be reflected in the suture closure patterns of these three taxa. Results indicated that while all three species do share a similar lateral-anterior closure pattern, G. gorilla exhibits a unique vault pattern, which, unlike humans and P. troglodytes, follows a strong posterior-to-anterior gradient. P. troglodytes is therefore more like Homo sapiens in suture synostosis.

Cray J Jr ，Meindl RS ，Sherwood CC ，Lovejoy CO ... -  《-》

Ectocranial suture fusion in primates: as related to cranial volume and dental eruption.

Timing of calvarial suture fusion is important in primate ontogeny. Ages at death are difficult to assess especially for museum collections. 1550 skulls of Hominoid, Hylobatidae, Macaca and Papio were observed for fusion. Calvarial expansion (early) and dental eruption (late) were utilized as indicators of ontogeny. Homogeneity of slopes and ANOVA were used to determine differences in timing of fusion. For calvarial growth the great apes all showed small levels of calvarial suture remodeling prior to full calvarial expansion. For dental eruption, Homo and Macaca share a common pattern of fusion in late adulthood. The other species show early remodeling. Papio was observed to have distinct patterns for suture fusion progression. Thus, suture fusion progression although influenced by evolutionary changes in the robusticity of the craniofacial skeleton can be modeled by the phylogeny among this group. Overall, Homo appears to have a distinct pattern of delayed suture fusion progression.

Cray J Jr ，Cooper GM ，Mooney MP ，Siegel MI ... -  《-》

Brief communication: Ectocranial suture closure in Pongo: pattern and phylogeny.

Ectocranial suture fusion patterns have been shown to contain biological and phylogenetic information. Previously the patterns of Homo, Pan, and Gorilla have been described. These data reflect the phylogenetic relationships among these species. In this study, we applied similar methodology to Pongo to determine the suture synostosis progression of this genus, and to allow comparison to previously reported data on other large-bodied hominoids. We hypothesized these data would strengthen the argument that suture synostosis patterns reflect the phylogeny of primate taxa. Results indicate that the synostosis of vault sutures in Pongo is similar to that reported for Gorilla (excluding Pan and Homo). However, the lateral-anterior pattern of fusion, in which there is a strong superior to inferior pattern, for Pongo is unique among these species, reflecting its phylogenetic distinctness among great ape taxa.

Cray J Jr ，Cooper GM ，Mooney MP ，Siegel MI ... -  《-》