Development, Structure, and Function of the Zygomatic Bones: What is New and Why Do We Care?

Abstract

This issue of The Anatomical Record is the first of a two-volume set on the zygoma (also called the cheek bone, the zygomatic bone, the malar, or the jugal, the latter term being used in vertebrates other than mammals). The zygoma is an important component of the craniofacial skeleton, in which the zygoma is a connection between the midfacial and the cranial skeletons; has a functional role as the origin of one of the masticatory muscles, the masseter muscle, and several facial muscles; has been considered as an essential buttress of the facial skeleton for resisting masticatory forces; and has importance for determining phylogenetic relationships. In humans, the zygoma is also of aesthetic significance for facial appearance, and its restoration following trauma has resulted in a large clinical literature. In this first volume of this Special Issue, a wide ranging series of papers discuss studies related to issues of development, structure, and function of the zygoma and closely related parts of the craniofacial skeleton in mammals, and in particular primates. This Introductory article provides an overview in which we discuss the primary findings of these studies and some of their implications. The second volume, which will be published as the January 2017 issue of The Anatomical Record, will focus on variation and evolution of the zygoma throughout the vertebrates. Anat Rec, 299:1611-1615, 2016. V C 2016 Wiley Periodicals, Inc.Key words: jugal; craniofacial bones; anatomy; biomechanics; adaptation; evolution; midface This special issue of The Anatomical Record is the first of a two-volume set focused on the cheekbone usually called the zygoma or zygomatic bone (plural: zygomata or zygomatic bones) in mammals, although sometimes referred to as the malar. In reptiles, amphibians, and birds, this bone is called the jugal bone or often just the jugal. This first-volume explores topics related to the development, adaptation, structure, and function of this craniofacial bone primarily in mammals with an emphasis on primates, while the second volume is concerned with its evolution throughout vertebrate history. While difficult to fully separate these topics in the two volumes because most of the studies in the first volume are investigating the zygoma at least in part to shed light on its evolutionary history with concerns relating to evolutionary adaptation, while the second volume looks not only at evolution but also the broad array of forms that this bone has obtained in vertebrates. The latter topic inspired the cover art for these volumes, which illustrates representative vertebrate skulls in a phylogenetic arrangement with the jugal/zygoma highlighted in each case.The left side of the cover art, from bottom to top, are found the sarcopterygian fish Onychodus from Upper

Evolution of the Jugal/Zygomatic Bones

“…Many of the articles in the first volume (December 2016) at least in part included topics that shed light on the evolutionary history of the zygoma, with concerns relating to evolutionary adaptation and function (Dechow and Wang, ). Those articles discussed how development and genetics related to our understanding of evolution in the craniofacial region (Heuzé et al, ), the implications of developmental patterns in perinatal postorbital anatomy in 21 genera of primates (DeLeon et al, ), the vascularization of the zygomatic arch (Herring and Ochareon, ), the effects of hard and soft diet on the morphology of the zygomatic region (Franks et al, ), structure and function of the orbit in some modern and fossil primates (Harvey et al, ; Rosenberger et al, ), the histological structure of soft tissues overlying the zygomatic and facial region (Burrows et al, ), the functional implications of zygomatic structure in primates (Edmonds, ), the structure and elastic properties of the facial skeleton including the zygoma (Gharpure et al, , Pryor MacIntosh et al, ), implications of sutural variation in the zygoma of primates (Wang and Dechow, ), the significance of variation in the shape of the zygomatic arch explored with finite element modeling (Smith and Grosse, ), and a biomechanical assessment of the utility of a pillar and buttress model for evaluating zygomatic function (Prado et al, ).…”

A Jugal in the Rough: The Evolutionary Importance of the Zygoma

“…As I described in my Commentary to the first part (Laitman, ), The Anatomical Record is proudly publishing a two‐part Special Issue for the first time. The first part appeared in our December 2016 issue of the Journal, and focused on the zygoma's “Development, Adaptation, Structure and Function” (Dechow and Wang, ). We now dig under the rocks and look further and deeper into the nooks and crannies to see how the anatomy and biomechanics morphed and changed through the millennia in this, the continuation of our Special Issue, now exploring the zygoma's “Evolution” (Dechow and Wang, , this issue.…”

Understanding the Tie That Binds: Deciphering the World of the Zygoma

“…For the first time, The Anatomical Record will publish a two‐volume Special Issue. This month (December, 2016) will focus on “Development, Adaptation, Structure and Function” of the Zygoma (Dechow and Wang, , this issue) and in January of 2017, the other half of the Special Issue will be devoted to an exploration of its “Evolution” from Agnatha and Tetrapods through dinosaurs to fossil humans to us.…”