title: Betwixt and Between: Intracranial Perspective on Zygomatic Arch Plasticity and Function in Mammals.
abstract: The zygomatic arch is morphologically complex, providing a key interface between the viscerocranium and neurocranium. It also serves as an attachment site for masticatory muscles, thereby linking it to the feeding apparatus. Though morphological variation related to differential loading is well known for many craniomandibular elements, the adaptive osteogenic response of the zygomatic arch remains to be investigated. Here, experimental data are presented that address the naturalistic influence of masticatory loading on the postweaning development of the zygoma and other cranial elements. Given the similarity of bone-strain levels among the zygoma and maxillomandibular elements, a rabbit and pig model were used to test the hypothesis that variation in cortical bone formation and biomineralization along the zygomatic arch and masticatory structures are linked to increased stresses. It was also hypothesized that neurocranial structures would be minimally affected by varying loads. Rabbits and pigs were raised for 48 weeks and 8 weeks, respectively. In both experimental models, CT analyses indicated that elevated masticatory loading did not induce differences in cortical bone thickness of the zygomatic arch, though biomineralization was positively affected. Hypotheses were supported regarding bone formation for maxillomandibular and neurocranial elements. Varying osteogenic responses in the arch suggests that skeletal adaptation, and corresponding variation in performance, may reside differentially at one level of bony architecture. Thus, it is possible that phenotypic diversity in the mammalian zygoma is due more singularly to natural selection (vs. plasticity). These findings underscore the complexity of the zygomatic arch and, more generally, determinants of skull form. Anat Rec, 299:1646-1660, 2016. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Department of Biological Sciences, The University of Notre Dame, Notre Dame, Indiana.
authors.forename: Erin M
authors.initials: EM
authors.lastname: Franks
authors.affiliation: Department of Orthodontics, The University of Iowa, Iowa City, Iowa.|Department of Anthropology, The University of Iowa, Iowa City, Iowa.
authors.forename: Nathan E
authors.initials: NE
authors.lastname: Holton
authors.affiliation: Department of Anthropology, Southern Illinois University, Carbondale, Illinois.
authors.forename: Jeremiah E
authors.initials: JE
authors.lastname: Scott
authors.affiliation: Department of Biological Sciences, The University of Notre Dame, Notre Dame, Indiana.
authors.forename: Kevin R
authors.initials: KR
authors.lastname: McAbee
authors.affiliation: Department of Biological Sciences, The University of Notre Dame, Notre Dame, Indiana.
authors.forename: Jason T
authors.initials: JT
authors.lastname: Rink
authors.affiliation: Department of Biological Sciences, The University of Notre Dame, Notre Dame, Indiana.
authors.forename: Kazune C
authors.initials: KC
authors.lastname: Pax
authors.affiliation: Department of Biological Sciences, The University of Notre Dame, Notre Dame, Indiana.
authors.forename: Adam C
authors.initials: AC
authors.lastname: Pasquinelly
authors.affiliation: Department of Biological Sciences, The University of Notre Dame, Notre Dame, Indiana.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Scollan
authors.affiliation: Department of Biological Sciences, The University of Notre Dame, Notre Dame, Indiana.
authors.forename: Meghan M
authors.initials: MM
authors.lastname: Eastman
authors.affiliation: Department of Biological Sciences, The University of Notre Dame, Notre Dame, Indiana.|Department of Aerospace and Mechanical Engineering, The University of Notre Dame, Notre Dame, Indiana.|Department of Anthropology, The University of Notre Dame, Notre Dame, Indiana.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Ravosa
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology; D001732:Bite Force; D008322:Mammals / Q000033:anatomy & histology* / Q000502:physiology; D011817:Rabbits; D013552:Swine; D015050:Zygoma / Q000033:anatomy & histology* / Q000502:physiology
keywords: dietary plasticity; evolution; function; masticatory loading; zygoma