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Functional and evolutionary significance of the recruitment and firing patterns of the jaw adductors during chewing in Verreaux's sifaka (Propithecus verreauxi).

Publication ,  Journal Article
Hylander, WL; Vinyard, CJ; Wall, CE; Williams, SH; Johnson, KR
Published in: American journal of physical anthropology
August 2011

Jaw-muscle electromyographic (EMG) patterns indicate that compared with thick-tailed galagos and ring-tailed lemurs, anthropoids recruit more relative EMG from their balancing-side deep masseter, and that this muscle peaks late in the power stroke. These recruitment and firing patterns in anthropoids are thought to cause the mandibular symphysis to wishbone (lateral transverse bending), resulting in relatively high symphyseal stresses. We test the hypothesis that living strepsirrhines with robust, partially fused symphyses have muscle recruitment and firing patterns more similar to anthropoids, unlike those strepsirrhines with highly mobile unfused symphyses. Electromyographic (EMG) activity of the superficial and deep masseter, anterior and posterior temporalis, and medial pterygoid muscles were recorded in four dentally adult Verreaux's sifakas (Propithecus verreauxi). As predicted, we find that sifaka motor patterns are more similar to anthropoids. For example, among sifakas, recruitment levels of the balancing-side (b-s) deep masseter are high, and the b-s deep masseter fires late during the power stroke. As adult sifakas often exhibit nearly complete symphyseal fusion, these data support the hypothesis that the evolution of symphyseal fusion in primates is functionally linked to wishboning. Furthermore, these data provide compelling evidence for the convergent evolution of the wishboning motor patterns in anthropoids and sifakas.

Duke Scholars

Published In

American journal of physical anthropology

DOI

EISSN

1096-8644

ISSN

0002-9483

Publication Date

August 2011

Volume

145

Issue

4

Start / End Page

531 / 547

Related Subject Headings

  • Strepsirhini
  • Masticatory Muscles
  • Mastication
  • Male
  • Jaw
  • Female
  • Electromyography
  • Biomechanical Phenomena
  • Anthropology
  • Animals
 

Citation

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Chicago
ICMJE
MLA
NLM
Hylander, W. L., Vinyard, C. J., Wall, C. E., Williams, S. H., & Johnson, K. R. (2011). Functional and evolutionary significance of the recruitment and firing patterns of the jaw adductors during chewing in Verreaux's sifaka (Propithecus verreauxi). American Journal of Physical Anthropology, 145(4), 531–547. https://doi.org/10.1002/ajpa.21529
Hylander, William L., Christopher J. Vinyard, Christine E. Wall, Susan H. Williams, and Kirk R. Johnson. “Functional and evolutionary significance of the recruitment and firing patterns of the jaw adductors during chewing in Verreaux's sifaka (Propithecus verreauxi).American Journal of Physical Anthropology 145, no. 4 (August 2011): 531–47. https://doi.org/10.1002/ajpa.21529.
Hylander WL, Vinyard CJ, Wall CE, Williams SH, Johnson KR. Functional and evolutionary significance of the recruitment and firing patterns of the jaw adductors during chewing in Verreaux's sifaka (Propithecus verreauxi). American journal of physical anthropology. 2011 Aug;145(4):531–47.
Hylander, William L., et al. “Functional and evolutionary significance of the recruitment and firing patterns of the jaw adductors during chewing in Verreaux's sifaka (Propithecus verreauxi).American Journal of Physical Anthropology, vol. 145, no. 4, Aug. 2011, pp. 531–47. Epmc, doi:10.1002/ajpa.21529.
Hylander WL, Vinyard CJ, Wall CE, Williams SH, Johnson KR. Functional and evolutionary significance of the recruitment and firing patterns of the jaw adductors during chewing in Verreaux's sifaka (Propithecus verreauxi). American journal of physical anthropology. 2011 Aug;145(4):531–547.
Journal cover image

Published In

American journal of physical anthropology

DOI

EISSN

1096-8644

ISSN

0002-9483

Publication Date

August 2011

Volume

145

Issue

4

Start / End Page

531 / 547

Related Subject Headings

  • Strepsirhini
  • Masticatory Muscles
  • Mastication
  • Male
  • Jaw
  • Female
  • Electromyography
  • Biomechanical Phenomena
  • Anthropology
  • Animals