| Hanssuesia Temporal range: Late Cretaceous,
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|---|---|
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| Computed tomography images of specimen TMP 79.14.853, showing lesions | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | †Ornithischia |
| Clade: | †Neornithischia |
| Clade: | †Pachycephalosauria |
| Family: | †Pachycephalosauridae |
| Genus: | †Hanssuesia Sullivan, 2003 |
| Type species | |
| †Troodon sternbergi Brown & Schlaikjer, 1943
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| Species | |
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†Hanssuesia sternbergi | |
| Synonyms | |
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Troodon sternbergi | |
Hanssuesia is a genus of pachycephalosaurid dinosaurs from the late Cretaceous period. It lived in what is now Alberta and Montana, and contains the single species Hanssuesia sternbergi.
Hanssuesia is based on a skull dome originally named Troodon sternbergi by Barnum Brown and Erich Maren Schlaikjer in 1943. The specific name honoured Charles Mortram Sternberg who found the dome in 1928 near Steveville in south Alberta.[1] In 1945, it was transferred to Stegoceras by C.M. Sternberg himself, as a Stegoceras sternbergi.[2]
The genus Hanssuesia was first named by Robert M. Sullivan in 2003. The generic name honours paleontologist Hans-Dieter Sues.[3] The spelling variant "Hanssuessia" appeared in the publication, but the same year Sullivan chose for Hanssuesia as the valid name.[4] Its type species is Troodon sternbergi, and the combinatio nova is Hanssuesia sternbergi.
H. sternbergi is known from the holotype NMC 8817 and six referred specimens (mainly frontoparietals) which were collected from two formations of the Belly River Group of Alberta, Canada, the Dinosaur Park Formation (late Campanian, 76.5–75 ma) in the Dinosaur Provincial Park, and the Oldman Formation (middle Campanian, 77.5–76.5 ma), as well as from the upper Judith River Formation of Montana, United States (late Campanian, 76–75 ma).[3]
Like other pachycephalosaurs, Hanssuesia had a thick skull roof. However, Hanssuesia is distinguished from other pachycephalosaurs by having a depressed parietal region, a frontoparietal dome that is wide in front as well as in the rear, a broad nasal boss on the frontals, reduced but swollen prefrontal lobes, and a reduced parietosquamosal shelf at the dome rear.[3] These traits were based on misinterpretations, according to Dyer et al. (2023), who consequently referred Hanssuesia back to Stegoceras.[5]
Hanssuesia was initially described as one of several pachycephalosaurids known from Dinosaur Park, including Stegoceras validum, Gravitholus albertae, and Foraminacephale brevis. It is unclear whether all of these species would have lived in the area at the same time. Dyer et al. also found Gravitholus to be synonymous with Stegoceras, thus decreasing the diversity of Dinosaur Park pachycephalosaurids to only two valid taxa.[5]
- ^ B. Brown and E.M. Schlaikjer, 1943, "A study of the troödont dinosaurs with the description of a new genus and four new species", Bulletin of the American Museum of Natural History 82(5): 115-150
- ^ C.M. Sternberg, 1945, "Pachycephalosauridae proposed for dome-headed dinosaurs, Stegoceras lambei, n. sp., described", Journal of Paleontology 19(5): 534-538
- ^ a b c Robert M. Sullivan (2003). "Revision of the dinosaur Stegoceras Lambe (Ornithischia, Pachycephalosauridae)". Journal of Vertebrate Paleontology. 23 (1): 181–207. doi:10.1671/0272-4634(2003)23[181:rotdsl]2.0.co;2.
- ^ Sullivan R.M. (2003). "Hanssuesia, the correct generic name for 'Hanssuessia' Sullivan, 2003". Journal of Vertebrate Paleontology. 23 (3): 714. Bibcode:2003JVPal..23..714S. doi:10.1671/03010. S2CID 84466393.
- ^ a b Dyer, Aaron D.; Powers, Mark J.; Currie, Philip J. (2023). "Problematic putative pachycephalosaurids: Synchrotron µCT imaging shines new light on the anatomy and taxonomic validity of Gravitholus albertae from the Belly River Group (Campanian) of Alberta, Canada". Vertebrate Anatomy Morphology Palaeontology. 10 (1): 65–110. doi:10.18435/vamp29388. ISSN 2292-1389.