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The subarcuate fossa and cerebellum of extant primates: Comparative study of a skull‐brain interface
Author(s) -
Gan Patrick J.,
Eden Avrim R.,
Laitman Jeffrey T.
Publication year - 1988
Publication title -
american journal of physical anthropology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.146
H-Index - 119
eISSN - 1096-8644
pISSN - 0002-9483
DOI - 10.1002/ajpa.1330770202
Subject(s) - fossa , anatomy , skull , biology , vestibular system , primate , cerebellum , brain size , medicine , neuroscience , magnetic resonance imaging , radiology
The subarcuate fossa of the petrosal bone houses the petrosal lobule of the cerebellar paraflocculus. Although the subarcuate fossa can be extensive, little is known about its relative size and distribution in primates. Studies indicate parafloccular involvement with cerebellar areas coordinating vestibular, visual, auditory, and locomotor systems. Hypotheses have proposed a role for the paraflocculus in vestibular‐oculomotor integration, caudal muscle control, autonomic function, and visual‐manual predation. This study examines the morphology and relative extent of the subarcuate fossa/petrosal lobule in a range of living primates. Methods include study of postmortem specimens representing nine mammalian orders, and quantification of the volume of the subarcuate fossa and endocranial cavity in 155 dry primate crania of 36 genera. Results show that, in mammals, the size and morphology of the petrosal lobule is directly related to that of the subarcuate fossa. Craniometric analysis shows that the ratio of subarcuate fossa volume to endocranial volume is largest in lemuriforms. The largest ratio is in Microcebus and Hapalemur . Lorisids show a significant reduction in the size of the subarcuate fossa to almost 50% below the lemuriform mean. Tarsius is near the lemuriform mean. Among platyrrhines, the ratio is high, but significantly reduced compared to lemuriforms. The highest platyrrhine ratio is seen in Ateles , the lowest in Saimiri and Alouatta . Atelids are significantly elevated compared to cebids. In cercopithecids, the fossa is significantly reduced compared to platyrrhines. The trend toward reduction of the cercopithecid fossa is most pronounced in Theropithecus and least evident in Presbytis . In hominoids, the fossa is present only in Hylobates . In great apes and humans, other than Gorilla , the petromastoid canal occupies a similar location to the subarcuate fossa of other primates, but is not homologous to it. Neither the subarcuate fossa nor the petromastoid canal are present in Gorilla . A graded reduction of the subarcuate fossa/petrosal lobule is evident among primates which evolved later in time. The relative size of this cerebellar lobule within primates may reflect size‐related factors and/or degree of neocortical evolution as these relate to usage of a specific sensory‐mediated locomotor behavior. The subarcuate fossa may serve as an indicator of the differentiation of the petrosal lobule of the paraflocculus in fossil forms.