Cranial morphology and systematics ofChasmosaurus(Dinosauria: Ceratopsidae) from the Upper Cretaceous of western Canada

Godfrey, Stephen J.; Holmes, Robert B.

doi:10.1080/02724634.1995.10011258

Cited by 58 publications

(128 citation statements)

References 8 publications

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“…The results presented here are therefore only preliminary, pending further investigation of individual variation in the ceratopsian postcranial skeleton. Finally, previous detailed reviews of the frill morphology of either specimen seem to suggest that CMN 2245 and CMN 2280 may, in fact, belong to separate species (C. belli and C. russelli, respectively), as first put forth by Godfrey and Holmes (1995). This view is further supported by the stratigraphic segregation of the two specimens within the Dinosaur Park Formation of Alberta.…”

Section: Resultssupporting

confidence: 64%

“…This observation was made previously by Godfrey and Holmes (1995) and Holmes et al (2001), and more recent quarry data support this claim, with C. russelli confined to the lower part of the formation and C. belli located much higher in the section (Ryan and Evans 2005). These independent lines of evidence strongly suggest that the variation between CMN 2245 and CMN 2280 is interspecific in nature, negating Sternberg's case for sexual dimorphism.…”

Section: Two-species Hypothesissupporting

confidence: 74%

“…However, the lateral parietal bars of AMNH 5402 used by Lehman are not illustrated as being complete as they are in the original specimen, which creates the false impression that the frills exhibit graded variation. Correcting for this splits the series into two discrete groupings of frill morphologies (Figure 6), the contents of which agree with the original hypodigms of Godfrey and Holmes (1995).…”

Section: Two-species Hypothesismentioning

confidence: 66%

“…In a review of the systematics of the genus Chasmosaurus (Godfrey and Holmes 1995), two species were diagnosed based on differences in parietosquamosal frill structure. C. belli was defined as possessing a "parietal frill with nearly straight transverse posterior bars, each bearing one large 408 THE CANADIAN FIELD-NATURALIST Vol.…”

Section: Two-species Hypothesismentioning

confidence: 99%

“…Sternberg attributed the difference in robustness between the two specimens to sexual dimorphism, stating, "it is thought that they represent male and female as it is common, among reptiles, for the female to be larger than the male" (Stern berg 1927: 67). This assumption has gone largely unchallenged in the literature (e.g., Lull 1933;Carpenter and Currie 1990;Dodson 1996), except for an implication by Godfrey and Holmes (1995) that the reported differences between the specimens do not reflect sexual dimorphism because they pertain to two separate species of Chasmosaurus.…”

mentioning

confidence: 99%

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A Reevaluation of Sexual Dimorphism in the Postcranium of the Chasmosaurine Ceratopsid Chasmosaurus belli (Dinosauria: Ornithischia)

Mallon

Holmes

2006

Can Field Nat

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The sexual dimorphism attributed to Chasmosaurus belli by Sternberg (1927) is revisited and reevaluated. A reexamination of the two specimens originally considered by Sternberg reveals that they are less complete than first suggested, with only a moderate amount of overlapping material between them. Only a few of the postcranial elements (humeri, sternal plates, and presacral vertebrae) show evidence of dimorphism, the significance of which is either doubtful or equivocal. Instead of representing sexual dimorphs, it is likely that the two specimens belong to separate species, C. belli and C. russelli, as evidenced by their distinct frill morphologies and by their stratigraphic segregation within the Dinosaur Park Formation of Alberta. These findings emphasize the need to remain sceptical about claims advocating sexual dimorphism in the fossil record in the absence of statistical significance or stratigraphic control.

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Section: Resultssupporting

confidence: 64%

Section: Two-species Hypothesissupporting

confidence: 74%

Section: Two-species Hypothesismentioning

confidence: 66%

Section: Two-species Hypothesismentioning

confidence: 99%

mentioning

confidence: 99%

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A Reevaluation of Sexual Dimorphism in the Postcranium of the Chasmosaurine Ceratopsid Chasmosaurus belli (Dinosauria: Ornithischia)

Mallon

Holmes

2006

Can Field Nat

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

Dechow

Wang

2016

The Anatomical Record

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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

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Morphological Diversity and Evolution of the Jugal in Dinosaurs

Sullivan

2016

The Anatomical Record

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In dinosaurs, as in other reptiles, the homologue of the mammalian zygomatic bone is the jugal. The dinosaurian jugal was primitively triradiate, with posterior, dorsal and anterior processes that respectively contacted the quadratojugal, the postorbital, and the maxilla and lacrimal. However, the jugal evolved along different lines in the three major dinosaurian clades. In theropods this cranial element remained relatively conservative in morphology, apart from being reduced to a rod-like structure in most birds and a few non-avians. In sauropodomorphs the jugal eventually became small, plate-like and nearly restricted to the area below the orbit, even being excluded from the ventral margin of the skull in many derived taxa. Among ornithischians the jugal was highly variable, but in many cases became large and/or adorned with ornamental features such as horns, flanges, and rugosities. The jugal does not appear to have been a site of muscle attachment in most non-avian dinosaurs, but represented an important structural element in the akinetic dinosaurian skull. The conspicuous jugal ornaments seen in many ornithischian dinosaurs, like the less striking ones documented in some saurischians, may have played an important role in the social behavior of the species that possessed them. In many cases they have a weapon-like aspect suggesting use in aggressive displays, if not actual combat, adding to the evidence that agonistic behavior was likely widespread among ornithischians in particular. Anat Rec,

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Cranial morphology and systematics ofChasmosaurus(Dinosauria: Ceratopsidae) from the Upper Cretaceous of western Canada

Cited by 58 publications

References 8 publications

A Reevaluation of Sexual Dimorphism in the Postcranium of the Chasmosaurine Ceratopsid <em>Chasmosaurus belli</em> (Dinosauria: Ornithischia)

A Reevaluation of Sexual Dimorphism in the Postcranium of the Chasmosaurine Ceratopsid <em>Chasmosaurus belli</em> (Dinosauria: Ornithischia)

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

Morphological Diversity and Evolution of the Jugal in Dinosaurs

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