The anatomy and systematics of<i>Colepiocephale lambei</i>(Dinosauria: Pachycephalosauridae)

Schott, Ryan K.; Evans, David C.; Williamson, Thomas E.; Carr, Thomas D.; Goodwin, Mark B.

doi:10.1671/039.029.0329

Cited by 33 publications

(36 citation statements)

References 15 publications

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“…Hypertrophied nodes indicative of a parietosquamosal node row are absent on the parietal. The dorsal surface of the parietal is slightly depressed above of the posterior region of the temporal chambers, as in Sphaerotholus goodwini and Prenocephale prenes, but it lacks a stepped transition to a prominent parietosquamosal shelf, as in Colepiocephale lambei 29 and variably present in Stegoceras validum 24,30 . The lateral profile of the parietal suggests a weakly developed parietosquamosal shelf intermediate in morphology between the horizontal posteromedian extension of the parietal of Stegoceras validum and the smoothly rounded parietal morphology (sometimes referred to as 'down-turned') of Sphaerotholus and Prenocephale 24,25 .…”

Section: Dinosauriamentioning

confidence: 99%

The oldest North American pachycephalosaurid and the hidden diversity of small-bodied ornithischian dinosaurs

et al. 2013

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Taphonomic biases dictate how organisms are represented in the fossil record, but their effect on studies of vertebrate diversity dynamics is poorly studied. In contrast to the high diversity and abundance of small-bodied animals in extant ecosystems, small-bodied dinosaurs are less common than their large-bodied counterparts, but it is unclear whether this reflects unique properties of dinosaurian ecosystems or relates to taphonomic biases. A new, fully domed pachycephalosaurid dinosaur, Acrotholus audeti, from the Santonian of Alberta predates incompletely domed taxa, and provides important new information on pachycephalosaur evolution and the completeness of the ornithischian fossil record. Here we provide the first empirical evidence that the diversity of small-bodied ornithischian dinosaurs is strongly underestimated based on ghost lineages and the high proportion of robust and diagnostic frontoparietal domes compared with other pachycephalosaur fossils. This suggests preservational biases have a confounding role in attempts to decipher vertebrate palaeoecology and diversity dynamics through the Mesozoic.

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Section: Dinosauriamentioning

confidence: 99%

The oldest North American pachycephalosaurid and the hidden diversity of small-bodied ornithischian dinosaurs

et al. 2013

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“…As the frontoparietal increases in size, the dome becomes relatively thicker and wider posteriorly, resulting in the distinctive pear-shaped dome that characterizes Stegoceras . A similar growth pattern may also characterize Colepiocephale , given the similar shape of its cranial dome [5]. These growth-related changes in the proportions of the frontoparietal suggest that the use of frontoparietal ratios in systematic assessments of specimens and in phylogenetic analyses [17] should be considered carefully.…”

Section: Discussionmentioning

confidence: 88%

“…These two morphological types have been recognized as separate clades: the flat-headed Homalocephalidae and the domed Pachycephalosauridae [2]–[4]. Other studies, including most recent phylogenetic analyses, do not recognize Homalocephalidae and instead the flat-headed taxa are found to form successive sister taxa to Pachycephalosauridae, which remain a monophyletic group [1], [5]–[10]. Despite this, placement of flat-headed and domed pachycephalosaurs into separate taxa may not always be accurate.…”

Section: Introductionmentioning

confidence: 99%

Cranial Ontogeny in Stegoceras validum (Dinosauria: Pachycephalosauria): A Quantitative Model of Pachycephalosaur Dome Growth and Variation

et al. 2011

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Historically, studies of pachycephalosaurs have recognized plesiomorphically flat-headed taxa and apomorphically domed taxa. More recently, it has been suggested that the expression of the frontoparietal dome is ontogenetic and derived from a flat-headed juvenile morphology. However, strong evidence to support this hypothesis has been lacking. Here we test this hypothesis in a large, stratigraphically constrained sample of specimens assigned to Stegoceras validum, the best known pachycephalosaur, using multiple independent lines of evidence including conserved morphology of ornamentation, landmark-based allometric analyses of frontoparietal shape, and cranial bone histology. New specimens show that the diagnostic ornamentation of the parietosquamosal bar is conserved throughout the size range of the sample, which links flat-headed specimens to domed S. validum. High-resolution CT scans of three frontoparietals reveal that vascularity decreases with size and document a pattern that is consistent with previously proposed histological changes during growth. Furthermore, aspects of dome shape and size are strongly correlated and indicative of ontogenetic growth. These results are complementary and strongly support the hypothesis that the sample represents a growth series of a single taxon. Cranial dome growth is positively allometric, proceeds from a flat-headed to a domed state, and confirms the synonymy of Ornatotholus browni as a juvenile Stegoceras. This dataset serves as the first detailed model of growth and variation in a pachycephalosaur. Flat-headed juveniles possess three characters (externally open cranial sutures, tuberculate dorsal surface texture, and open supratemporal fenestrae) that are reduced or eliminated during ontogeny. These characters also occur in putative flat-headed taxa, suggesting that they may also represent juveniles of domed taxa. However, open cranial sutures and supratemporal fenestrae are plesiomorphic within Ornithischia, and thus should be expected in the adult stage of a primitive pachycephalosaur. Additional lines of evidence will be needed to resolve the taxonomic validity of flat-headed pachycephalosaur taxa.

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“…We divided the data into intermontane (n = 2), alluvial (n = 9) and coastal plain (n = 11) palaeoenvironments primarily using the classification scheme of Sampson & Loewen (2005. However, the Foremost Formation was reclassified as a coastal plain deposit because most fossils derive from its coastally influenced upper unit (Peng et al 2001;Brinkman et al 2004;Schott et al 2009;Ryan et al 2012). We tested for equal distribution of pachycephalosaurid remains across palaeoenvironments using chi-squared tests and for differences in relative abundance between palaeoenvironments using Kruskal-Wallis tests.…”

Section: Relative Abundancementioning

confidence: 99%

“…The morphology of this structure has proved crucial to both pachycephalosaurid systematics and phylogenetics (e.g. Williamson & Carr 2003;Sullivan 2003Sullivan , 2006Marya nska et al 2004;Schott et al 2009;Schott & Evans 2012;Evans et al 2013a). The majority of pachycephalosaurids are known from isolated domes, the common preservation of which has been hypothesized to result from their taphonomically resistant nature (Dodson 1983;Evans et al 2013a).…”

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confidence: 99%

Taphonomy and habitat preference of North American pachycephalosaurids (Dinosauria, Ornithischia)

Mallon

Evans

2014

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The traditional view of North American pachycephalosaurids holds that their domes are typically worn, as though they had undergone extensive fluvial transport, and that these animals therefore inhabited upland environments (e.g. piedmont/intermontane settings) relative to where their remains are typically found. Using a statistically robust sample of domes from Alberta, Canada, we subject these hypotheses to various forms of quantitative testing and show that: (1) domes typically exhibit minimal rounding; (2) dome roundness does not positively correlate with distance from the presumed intermontane origin; and (3) pachycephalosaurid remains are not relatively more abundant in intermontane than in alluvial or coastal plain palaeoenvironments. These findings contradict the traditional view of North American pachycephalosaurid dome taphonomy and support the argument that pachycephalosaurids frequented alluvial and coastal lowlands.

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The anatomy and systematics ofColepiocephale lambei(Dinosauria: Pachycephalosauridae)

Cited by 33 publications

References 15 publications

The oldest North American pachycephalosaurid and the hidden diversity of small-bodied ornithischian dinosaurs

The oldest North American pachycephalosaurid and the hidden diversity of small-bodied ornithischian dinosaurs

Cranial Ontogeny in Stegoceras validum (Dinosauria: Pachycephalosauria): A Quantitative Model of Pachycephalosaur Dome Growth and Variation

Taphonomy and habitat preference of North American pachycephalosaurids (Dinosauria, Ornithischia)

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