Ontogeny of the Postorbital Region in Tarsiers and Other Primates

Valerie B. DeLeon, Timothy D. Smith, Alfred L. Rosenberger

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Bony structure of the postorbital region is a key trait distinguishing major clades of primates. Strepsirrhines share a postorbital bar, and anthropoids share a complete postorbital septum. At issue is whether the partial postorbital septum of tarsiers unites living tarsiers more closely with anthropoids than with certain large-eyed Eocene fossils. Previously we reported incomplete postorbital closure in tarsiers at birth. In this article, we document comparative analyses of the postorbital region in a broad range of perinatal primates. Virtual reconstructions of microCT data were used to study three-dimensional structure of the perinatal cranium in these taxa. We also describe and illustrate formation of the tarsier partial postorbital septum through the perinatal period using a growth series of Tarsius syrichta. Our results support the hypothesis that partial postorbital septation in the tarsier is secondary to eye hypertrophy. Based on these observations, we propose a structural hypothesis for phylogenetic differences observed in the primate postorbital region. Specifically, we propose that key postorbital traits, including the frontal spur in strepsirrhines and the posterior lamina of the zygomatic in anthropoids, develop as a result of the spatial relationships of brain, eyes, and teeth. Haplorhines are united by expansion of the anterior cranial fossa and loss of the frontal spur. Anthropoids are further united to the exclusion of tarsiers by expansion of the temporal lobes and associated formation of the posterior lamina of the zygomatic. Mechanical forces related to these spatial relationships may be modulated by deep fascia of the orbit to induce formation of the postorbital septum. Anat Rec, 299:1631–1645, 2016.

Original languageEnglish (US)
Pages (from-to)1631-1645
Number of pages15
JournalAnatomical Record
Issue number12
StatePublished - Dec 1 2016
Externally publishedYes


  • alisphenoid
  • frontal
  • functional matrix hypothesis
  • orbital fascia
  • postorbital septation
  • zygomatic

ASJC Scopus subject areas

  • Anatomy
  • Biotechnology
  • Histology
  • Ecology, Evolution, Behavior and Systematics


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