[Paleontology • 2025] Zavacephale rinpoche • A domed pachycephalosaur from the early Cretaceous of Mongolia

Zavacephale rinpoche

Chinzorig, Takasaki, Yoshida, Tucker, Buyantegsh, Mainbayar, Tsogtbaatar & Zanno, 2025 

 

DOI: doi.org/10.1038/s41586-025-09213-6

Artwork by Masaya Hattori

Abstract

The dome-headed pachycephalosaurians are among the most enigmatic dinosaurs. Bearing a hypertrophied skull roof and elaborate cranial ornamentation, members of the clade are considered to have evolved complex sociosexual systems. Despite their importance in understanding behavioural ecology in Dinosauria, the absence of uncontested early diverging taxa has hindered our ability to reconstruct the origin and early evolution of the clade. Here we describe Zavacephale rinpoche gen. et sp. nov., from the Lower Cretaceous Khuren Dukh Formation of Mongolia, the most skeletally complete and geologically oldest pachycephalosaurian discovered globally. Z. rinpoche exhibits a well-developed frontoparietal dome and preserves the clade’s first record of manual elements and gastroliths. Phylogenetic analysis recovered Z. rinpoche as one of the earliest diverging pachycephalosaurians, pushing back fossil evidence of the frontoparietal dome by at least 14 Myr and clarifying macroevolutionary trends in its assembly. We found that the earliest stage of dome evolution occurred by means of a frontal-first developmental pattern with retention of open supratemporal fenestra, mirroring proposed ontogenetic trajectories in some Late Cretaceous taxa. Finally, intraskeletal osteohistology of the frontoparietal dome and hindlimb demonstrate decoupling of sociosexual and somatic maturity in early pachycephalosaurians, with advanced dome development preceding terminal body size.

 Zavacephale rinpoche gen. et sp. nov.

Tsogtbaatar Chinzorig, Ryuji Takasaki, Junki Yoshida, Ryan T. Tucker, Batsaikhan Buyantegsh, Buuvei Mainbayar, Khishigjav Tsogtbaatar and Lindsay E. Zanno. 2025. A domed pachycephalosaur from the early Cretaceous of Mongolia. Nature. DOI: doi.org/10.1038/s41586-025-09213-6 [17 September 2025]

https://www.nhm.ac.uk/discover/news/2025/september/new-dome-headed-dinosaur-most-complete-ever-found.html

[Paleontology • 2023] Sphaerotholus lyonsi & S. triregnum • Two New Species of Small-bodied pachycephalosaurine (Marginocephalia: Pachycephalosauria) from the uppermost Cretaceous of North America suggest Hidden Diversity in well-sampled Formations

  Sphaerotholus lyonsi & S. triregnum

Woodruff, Schott & Evans, 2023

DOI: 10.1002/spp2.1535 

 twitter.com/DoubleBeam

Abstract

Here we report two new small-bodied pachycephalosaurines: one from the Dinosaur Park Formation of Alberta and the other from the Hell Creek Formation of Montana, each represented by an isolated squamosal. These two new specimens are approximately the same size as squamosals of Sphaerotholus buchholtzae, and possess several overlapping morphologies with the genus (such as a strongly posteroventrally projecting and laterally tapering parietosquamosal bar). Therefore, these two new specimens are identified as belonging to the genus Sphaerotholus. However, a suite of characters and combinations differentiate these two new specimens from the other three Sphaerotholus species. Most notably, they possess multiple posterior and lateral node rows on the squamosal, and lack a parietosquamosal node (a single row and a parietosquamosal node define these other species in the genus). Specifically, the Alberta specimen possesses two posterior and two lateral node rows, whereas the Montana specimen has three of each. This analysis provides phylogenetic support for the evolutionary hypothesis that a single-rowed and parietosquamosal node-less taxon underwent a cladogenetic event that gave rise to a single-rowed and parietosquamosal node-bearing lineage and a multi-rowed, parietosquamosal node-less lineage (the two taxa described herein). In turn, these two Sphaerotholus lineages possibly underwent anagenetic change throughout the latest Maastrichtian. Additionally, these new taxa suggest that while large-bodied taxa from well sampled formations are to be found with decreasing frequency, the inverse holds true for small-bodied taxa and that pachycephalosaurines were more diverse than previously recognized, and continued to diversify up until the very end of the Cretaceous.

Keywords: Pachycephalosauria, Sphaerotholus, anagenesis, cladogenesis, Dinosaur Park Formation, Hell Creek Formation

Sphaerotholus triregnum 

Sphaerotholus lyonsi

D. Cary Woodruff, Ryan K. Schott and David C. Evans. 2023. Two New Species of Small-bodied pachycephalosaurine (Dinosauria, Marginocephalia) from the uppermost Cretaceous of North America suggest Hidden Diversity in well-sampled Formations. Papers in Palaeontology. DOI: 10.1002/spp2.1535

  twitter.com/DoubleBeam/status/1725127290143563834

[Paleontology • 2006] Yinlong downsi • A Basal Ceratopsian with Transitional Features from the Late Jurassic of northwestern China

Yinlong downsi 

Xu, Forster, Clark & Mo, 2006

illustration: Andrey Atuchin || doi: 10.1098/rspb.2006.3566

Although the Ceratopsia and Pachycephalosauria, two major ornithischian groups, are united as the Marginocephalia, few synapomorphies have been identified due to their highly specialized body-plans. Several studies have linked the Heterodontosauridae with either the Ceratopsia or Marginocephalia, but evidence for these relationships is weak, leading most recent studies to consider the Heterodontosauridae as the basal member of another major ornithischian radiation, the Ornithopoda. Here, we report on a new basal ceratopsian dinosaur, Yinlong downsi gen. et. sp. nov., from the Late Jurassic upper part of the Shishugou Formation of Xinjiang, China. This new ceratopsian displays a series of features transitional between more derived ceratopsians and other ornithischians, shares numerous derived similarities with both the heterodontosaurids and pachycephalosaurians and provides strong evidence supporting a monophyletic Marginocephalia and its close relationship to the Heterodontosauridae. Character distributions along the marginocephalian lineage reveal that, compared to the bipedal Pachycephalosauria, which retained a primitive post-cranial body-plan, the dominantly quadrupedal ceratopsians lost many marginocephalian features and evolved their own characters early in their evolution.

Keywords: Ceratopsia; Marginocephalia; Ornithischia; Late Jurassic; Shishugou Formation

Systematic palaeontology

Ornithischia Seeley, 1887.

Heterodontosauriformes new taxon.

Marginocephalia, Sereno (1986).

Ceratopsia Marsh, 1890.

Yinlong downsi gen et sp nov.

  Etymology: ‘Yin’ and ‘long’ mean ‘hiding’ and ‘dragon’ in Chinese, respectively, derived from the movie ‘Crouching Tiger, Hidden Dragon’ which was filmed in the locality where the holotype was found; the specific name is in memory of Mr Will Downs, who joined many palaeontological expeditions in China including the one with us in 2003, shortly before his death.

Holotype: IVPP V14530, a nearly complete skeleton missing only the distal tail (figure 1 and figures 1 and 2 of electronic supplementary material).

Locality and horizon: Wucaiwan, Junggar Basin, Xinjiang, China; upper part of Shishugou Formation, correlated with the Oxfordian stage of the early Late Jurassic (Chen 1996; Eberth et al. 2001).

Figure 2: IVPP V14530. (a) Skull and mandible in lateral view. (b) Skull in dorsal view.

Abbreviations: an, angular; d, dentary; emf, external mandibular fenestra; en, external naris; f, frontal; ff, fossa on frontals; fn, fossa on nasals; itf, infratemporal fenestra; j, jugal; m, maxilla; p, parietal; pa, palpebral; pd, predentary; pm, premaxilla; po, postorbital; q, quadrate; qj, quadratojugal; r, rostral bone; sa, surangular; sq, squamosal; stf, supratemporal fenestra; tr, tubercle row; ts, tubercle on surangular. Scale bar, 2 cm.

 Xing Xu, Catherine A. Forster, James M. Clark and Jinyou Mo. 2006. A Basal Ceratopsian with Transitional Features from the Late Jurassic of northwestern China. Proc. R. Soc. B. 273 (1598): 2135–2140.  doi: 10.1098/rspb.2006.3566

http://www2.gwu.edu/~newsctr/fossilfind/paper.pdf

Feng-Lu Han, Catherine A. Forster, James M. Clark & Xing Xu. 2015. Cranial anatomy of Yinlong downsi (Ornithischia: Ceratopsia) from the Upper Jurassic Shishugou Formation of Xinjiang, China.  Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2015.1029579

http://whenpigsfly-returns.blogspot.com/2007/07/yinlong-downsi-and-heterodontosauriform.html

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by ChrisMasna chrismasna.DeviantAr.com