A new pachycephalosaurid skull (Ornithischia) from the Cretaceous Hell Creek Formation of Montana

Giffin, Emily B.; Gabriel, Diane L.; Johnson, Rolf E.

doi:10.1080/02724634.1988.10011672

Cited by 14 publications

(2 citation statements)

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“…In addition to MPM 8111, MPM 7111 (Giffin et al ., 1987), YPM 335 (Sues and Galton, 1987), and UCMP 119433 (Sues and Galton, 1987), the following specimens are referred to Stygimoloch spinifer:…”

Section: Referred Specimensmentioning

confidence: 97%

Cranial anatomy and diagnosis ofStygimoloch spinifer(Ornithischia: Pachycephalosauria) with comments on cranial display structures in agonistic behavior

Goodwin

Buchholtz

Johnson

1998

Journal of Vertebrate Paleontology

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A new skull of Stygimoloch spinifer (MPM 8111) from the Upper Cretac eou s Hell Creek Form ation of North Dakota is the most complete specimen discove red to date. It allows much of the skull and braincase of this unusual pachycephalosaurid to be desc ribed for the first time and confirms a suite of diagnostic characters for the species. The skull is long with a vaulted, tran sver sely narrow frontoparietal dome and a robust squamosal forming a prominent posterior shelf. The shelf is ornamented by three to four large, low-angle horn s and mult iple clusters of smaller bony nodes. The orientation of the squamosal is preserved along an unambiguous contact with the frontoparietal suture, allowing definitive determination of the orientation of the squamosal horns . The se cranial features indicate a different mode of agonistic behavior than previously suggested for Stegocera s and Pachycephalosaurus . The high, narr ow dome of S. spinifer is not suited for head-butting, and the orientation of its squamosal horns and ornamental nodes strongly suggest display functions . Several additional specimens are described and referred to S. spinijer. INTRODUCTIONStygimoloch spinifer, an Upper Cretaceous (Maastrichtian) pachycephalosaurid ornithischian from western North America, has a high-domed, transversely narrow skull, distinguished by a unique cluster of well developed horns and bony nodes preserved along the posterodorsal surface of a thickened squamosal shelf. Prior to this report, the published record of Stygimoloch spinijer was limited to two isolated squamosals and one partial cranium. Galton and Sues (1983) named Stygimoloch spinijer from an unusual partial left squamosal ornamented with well-developed horns and robust bony nodes . This specimen (UCMP 119433) was collected from the Hell Creek Formation, McCone County, Montana. Galton and Sues referred an additional squamosal collected by J. B. Hatcher from the Lance Formation, Niobrara County Wyoming (YPM 335) to Stygimoloch spinijer. YPM 335 was first described by Marsh (1896) and refigured by Hatcher et al. (1907) as a dermal ossification of Triceratops. Brown and Schlaikjer (1943) referred this squamosal to Pachycephalosaurus sp . In 1987, Giffin et al. described a tall, narrow. domed pachycephalosaurid skull (MPM 7111) from the Hell Creek Formation of eastern Montana. They noted that it was significantly different from any previously known pachycephalosaurid, and named it a new species, Stenotholus kohleri, primarily on the basis of the markedly different shape of the cranium. Gabriel and Berghaus (1988) formally synonymized Stenotholus kohleri with Stygimoloch spinijer. Their comparison of MPM 7111 and MPM 8111 confirmed that both specimens shared the distinctive frontoparietal dome and cranial features characteristic of S. sp inijer.This study provides, for the first time, an extensive description of the cranial anatomy of Stygimoloch sp inifer and confirms the diagnostic characters for the species. Many aspects of pachycephalosaurid behavioral evolution hav...

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Section: Referred Specimensmentioning

confidence: 97%

Cranial anatomy and diagnosis ofStygimoloch spinifer(Ornithischia: Pachycephalosauria) with comments on cranial display structures in agonistic behavior

Goodwin

Buchholtz

Johnson

1998

Journal of Vertebrate Paleontology

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“…Their skulls are characterized by a cluster of swollen tubercles on the posterolateral corners of the dome. In Stygimoloch, three of these tubercles extend from the cluster as short horn cores (Brown & Schlaikjer 1943, Giffin et al 1987.…”

Section: Ornithischiamentioning

confidence: 99%

The Origin and Evolution of Dinosaurs

Sereno

1997

Annu. Rev. Earth Planet. Sci.

370

251

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▪ Abstract Phylogenetic studies and new fossil evidence have yielded fundamental insights into the pattern and timing of dinosaur evolution and the emergence of functionally modern birds. The dinosaurian radiation began in the Middle Triassic, significantly predating the global dominance of dinosaurs by the end of the period. The phylogenetic history of ornithischian and saurischian dinosaurs reveals evolutionary trends such as increasing body size. Adaptations to herbivory in dinosaurs were not tightly correlated with marked floral replacements. Dinosaurian biogeography during the era of continental breakup principally involved dispersal and regional extinction.

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Headbutting through time: A review of this hypothesized behavior in “dome‐headed” fossil taxa

Woodruff,

Ackermans

2024

The Anatomical Record

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Headbutting is a combative behavior most popularly portrayed and exemplified in the extant bighorn sheep (Ovis canadensis). When behaviorally proposed in extinct taxa, these organisms are oft depicted Ovis‐like as having used modified cranial structures to combatively slam into one another. The combative behavioral hypothesis of headbutting has a long and rich history in the vertebrate fossil literature (not just within Dinosauria), but the core of this behavioral hypothesis in fossil terrestrial vertebrates is associated with an enlarged osseous cranial dome—an osteological structure with essentially no current counterpart. One confounding issue found in the literature is that while the term “headbutting” sounds simplistic enough, little terminology has been used to describe this hypothesized behavior. And pertinent to this special issue, potential brain trauma and the merits of such proposed pugilism have been assessed largely from the potential deformation of the overlying osseous structure; despite the fact that extant taxa readily show that brain damage can and does occur without osteological compromise. Additionally, the extant taxa serving as the behavioral counterpart for comparison are critical, not only because of the combative behaviors and morphologies they display, but also the way they engage in such behavior. Sheep (Ovis), warthogs (Phacochoerus), and bison (Bison) all engage in various forms of “headbutting”, but the cranial morphologies and the way each engages in combat is markedly different. To hypothesize that an extinct organism engaged in headbutting like an extant counterpart in theory implies specific striking:contacting surfaces, speed, velocity, and overall how that action was executed. This review examines the history and usage of the headbutting behavioral hypothesis in these dome‐headed fossil taxa, their respective extant behavioral counterparts, and proposes a protocol for specific behavioral terms relating to headbutting to stem future confusion. We also discuss the disparate morphology of combative cranial structures in the fossil record, and the implications of headbutting‐induced brain injury in extinct taxa. Finally, we conclude with some potential implications for artistic reconstructions of fossil taxa regarding this behavioral repertoire.

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A new pachycephalosaurid skull (Ornithischia) from the Cretaceous Hell Creek Formation of Montana

Cited by 14 publications

References 9 publications

Cranial anatomy and diagnosis ofStygimoloch spinifer(Ornithischia: Pachycephalosauria) with comments on cranial display structures in agonistic behavior

Cranial anatomy and diagnosis ofStygimoloch spinifer(Ornithischia: Pachycephalosauria) with comments on cranial display structures in agonistic behavior

The Origin and Evolution of Dinosaurs

Headbutting through time: A review of this hypothesized behavior in “dome‐headed” fossil taxa

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