PBDB Taxon

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Pachycephalosauridae

Reptilia - Pachycephalosauridae

Taxonomy

Pachycephalosauridae was named by Sternberg (1945). It was considered monophyletic by Sereno (2000), Butler et al. (2008), unknown by Watabe et al. (2011).

It was assigned to Ornithischia by Tatarinov (1964); to Brachypoda by Thulborn (1974), Thulborn (1977); to Ornitophoda by Bonaparte (1978); to Pachycephalosauroidea by Zhao (1983); to Ornithopoda by Sternberg (1945), Romer (1956), Parsch (1963), Kuhn (1964), Estes (1964), Kuhn (1966), Romer (1966), Charig (1967), Swinton (1970), Galton (1971), Galton (1974), Wall and Galton (1979), Sues and Taquet (1979), Benton (1979), Bonaparte (1980), Ostrom (1980), McIntosh (1981), Norman (1984); to Pachycephalosauria by Cooper (1985); to Orbitoscuta by Bakker (1986); to Pachycephalosauria by Maryańska and Osmólska (1974), Rozhdestvensky (1977), Dong (1978), Russell (1984), Sues and Galton (1987), Carroll (1988), Maryanska (1990), Dong (1992), Sereno (1997), Sereno (1998), Goodwin et al. (1998), Sereno (1999), Peng et al. (2001), Williamson and Carr (2003); to Homalocephaloidea by Maryanska et al. (2004); to Ornithischia by Watabe et al. (2011); to Ornithischia by Eberth et al. (2001), Sullivan (2006), Jasinski and Sullivan (2011), Evans et al. (2013); and to Pachycephalosauria by Olshevsky and Ford (1994), Sues (1997), Sereno (2000), Butler et al. (2008), Han et al. (2012), Woodruff et al. (2021).

Subtaxa

Amtocephale, Colepiocephale, Domocephalinae, Gravitholus, Hanssuesia, Pachycephalosaurinae, Pachycephalosaurini, Sinocephale, Texacephale, Tylocephale

Synonyms

Texacephale was named by Longrich et al. (2010). Its type is Texacephale langstoni.

It was considered a nomen dubium by Jasinski and Sullivan (2011), Watabe et al. (2011).

It was assigned to Pachycephalosauridae by Longrich et al. (2010).
Texacephale langstoni was named by Longrich et al. (2010). Its type specimen is LSUMNS 20010, a partial skull (Frontoparietals), and it is a 3D body fossil. Its type locality is WPA Quarry L1, Talley Mountain, which is in a Campanian/Campanian fine channel fill mudstone in the Aguja Formation of Texas. It is the type species of Texacephale.

It was considered a nomen dubium by Jasinski and Sullivan (2011), Watabe et al. (2011).
Gravitholus was named by Wall and Galton (1979). Its type is Gravitholus albertae.

It was synonymized subjectively with Stegoceras by Williamson and Carr (2003), Williamson and Carr (2006); it was considered a nomen dubium by Sullivan (2003); it was considered a nomen dubium by Sullivan (2006), Jasinski and Sullivan (2011).

It was assigned to Pachycephalosauridae by Wall and Galton (1979), Currie (1980), Dodson (1983), Russell (1984), Clemens (1986), Sues and Galton (1987), Carroll (1988), Maryanska (1990), Olshevsky and Ford (1994), Maryanska et al. (2004).
Tholocephalidae was named by Sereno (1986).

It was considered a nomen vanum by Sereno (2000); it was synonymized subjectively with Pachycephalosauridae by Maryanska et al. (2004).

It was assigned to Homalocephaloidea by Sereno (1986).

Synonymy list

Year	Name and author
1945	Pachycephalosauridae Sternberg pp. 535-536
1956	Pachycephalosauridae Romer p. 631
1963	Pachycephalosauridae Parsch p. 4
1964	Pachycephalosauridae Estes p. 144
1964	Pachycephalosauridae Kuhn p. 30
1964	Pachycephalosauridae Tatarinov p. 588
1966	Pachycephalosauridae Kuhn p. 103
1966	Pachycephalosauridae Romer p. 370
1967	Pachycephalosauridae Charig p. 716
1970	Pachycephalosauridae Swinton p. 200
1971	Pachycephalosauridae Galton p. 40
1974	Pachycephalosauridae Galton p. 1064 fig. 6
1974	Pachycephalosauridae Maryańska and Osmólska p. 50
1974	Pachycephalosauridae Thulborn p. 173
1977	Pachycephalosauridae Rozhdestvensky p. 114
1977	Pachycephalosauridae Thulborn p. 726 fig. 1
1978	Pachycephalosauridae Bonaparte p. 331
1978	Pachycephalosauridae Dong p. 225
1979	Pachycephalosauridae Benton p. 143
1979	Pachycephalosauridae Sues and Taquet
1979	Gravitholus Wall and Galton pp. 1180-1181
1979	Pachycephalosauridae Wall and Galton p. 1185
1980	Pachycephalosauridae Bonaparte p. 82
1980	Gravitholus Currie pp. 29-30
1980	Pachycephalosauridae Ostrom p. 22
1981	Pachycephalosauridae McIntosh p. 35
1983	Gravitholus Dodson p. 95
1983	Pachycephalosauridae Zhao p. 301
1984	Pachycephalosauridae Norman pp. 160-162 fig. 2
1984	Gravitholus Russell p. 25
1984	Pachycephalosauridae Russell p. 29
1985	Pachycephalosauridae Cooper p. 291
1986	Pachycephalosauridae Bakker p. 461
1986	Gravitholus Clemens p. 80
1986	Tholocephalidae Sereno
1987	Gravitholus Sues and Galton
1987	Pachycephalosauridae Sues and Galton
1988	Gravitholus Carroll
1988	Pachycephalosauridae Carroll
1990	Gravitholus Maryanska p. 566
1990	Pachycephalosauridae Maryanska p. 566
1992	Pachycephalosauridae Dong p. 166
1994	Gravitholus Olshevsky and Ford p. 91
1994	Pachycephalosauridae Olshevsky and Ford p. 91
1997	Pachycephalosauridae Sereno p. 443
1997	Pachycephalosauridae Sues p. 512
1998	Pachycephalosauridae Goodwin et al. p. 363
1998	Pachycephalosauridae Sereno p. 62
1999	Pachycephalosauridae Sereno p. 2138 fig. 2
2000	Pachycephalosauridae Sereno p. 482
2001	Pachycephalosauridae Eberth et al. p. 57
2001	Pachycephalosauridae Peng et al. p. 36
2003	Pachycephalosauridae Williamson and Carr fig. 11
2004	Gravitholus Maryanska et al. p. 465
2004	Pachycephalosauridae Maryanska et al. p. 465
2006	Pachycephalosauridae Sullivan p. 349
2008	Pachycephalosauridae Butler et al. pp. 22-23 figs. 2-4
2010	Texacephale Longrich et al.
2010	Texacephale langstoni Longrich et al. p. 276 figs. 3-5
2011	Pachycephalosauridae Jasinski and Sullivan p. 202
2011	Pachycephalosauridae Watabe et al. p. 490
2012	Pachycephalosauridae Han et al. p. 1391 fig. 14
2013	Pachycephalosauridae Evans et al. p. 2
2013	Texacephale langstoni Longrich et al. p. 24
2021	Pachycephalosauridae Woodruff et al. p. 588 fig. 14
2024	Texacephale langstoni Wick and Lehman p. 99

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Rank	Name	Author
kingdom	Animalia	()
—	Bilateria
—	Eubilateria	Ax 1987
—	Deuterostomia
phylum	Chordata	Haeckel 1874
subphylum	Vertebrata
superclass	Gnathostomata
—	Osteichthyes	()
subclass	Sarcopterygii	()
subclass	Dipnotetrapodomorpha	(Nelson 2006)
subclass	Tetrapodomorpha	()
—	Tetrapoda
—	Reptiliomorpha
—	Anthracosauria
subclass	Amphibiosauria	Kuhn 1967
—	Cotylosauria	()
—	Amniota
—	Sauropsida
class	Reptilia
subclass	Eureptilia	()

Rank	Name	Author
—	Romeriida
—	Diapsida	()
—	Archosauromorpha	(Huene 1946)
—	Crocopoda
—	Archosauriformes	Gauthier 1986
—	Eucrocopoda
—	Archosauria	()
informal	Avemetatarsalia
—	Ornithodira
—	Dinosauromorpha
—	Dinosauriformes
—	Dinosauria	()
—	Ornithischia	()
—	Genasauria
—	Cerapoda
—	Marginocephalia
—	Pachycephalosauria	()
family	Pachycephalosauridae
family	Pachycephalosauridae

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

Fm. †Pachycephalosauridae Sternberg 1945

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G. †Amtocephale Watabe et al. 2011

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†Amtocephale gobiensis Watabe et al. 2011

G. †Colepiocephale Sullivan 2003

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†Colepiocephale lambei Sternberg 1945

G. †Hanssuesia Sullivan 2003

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†Hanssuesia sternbergi Brown and Schlaikjer 1943

Subfm. †Pachycephalosaurinae Sereno 1997

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G. †Acrotholus Evans et al. 2013

†Acrotholus audeti Evans et al. 2013

G. †Foraminacephale Schott and Evans 2017

†Foraminacephale brevis Lambe 1918

G. †Platytholus Horner et al. 2023

†Platytholus clemensi Horner et al. 2023

G. †Sphaerotholus Williamson and Carr 2003

†Sphaerotholus buchholtzae Williamson and Carr 2003

†Sphaerotholus edmontonensis Brown and Schlaikjer 1943

†Sphaerotholus goodwini Williamson and Carr 2003

†Sphaerotholus lyonsi Woodruff et al. 2023

†Sphaerotholus triregnum Woodruff et al. 2023

Unr. †Pachycephalosaurini Sullivan 2003

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G. †Alaskacephale Sullivan 2006

†Alaskacephale gangloffi Sullivan 2006

G. †Sinocephale Evans et al. 2021

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†Sinocephale bexelli Bohlin 1953

G. †Tylocephale Maryańska and Osmólska 1974

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†Tylocephale gilmorei Maryańska and Osmólska 1974

Invalid names: Gravitholus Wall and Galton 1979 [nomen dubium], Texacephale Longrich et al. 2010 [nomen dubium], Tholocephalidae Sereno 1986 [synonym]

Diagnosis

Reference	Diagnosis
C. M. Sternberg 1945	Abdominal cuirass of segmented ribs; premaxillae with (or without) teeth; teeth in a single row (faces of crowns vertically ribbed, edges denticulate, base expanded); domelike thickening of parietal and frontal bones (occipetal condyle strongly deflected, neck probably strongly arched as in the Hadrosauridae); dorsal vertebrae having zygapophyses with tongue and groove articulation; pelvic bones resembling the Ceratopsia in the horizontal widening of the preacetabular portion of the ilium and ischium without obturator process and with an elongated pubic process.
T. Maryańska and H. Osmólska 1974	Bipedal, highly specialized ornithischians, small to moderate in size. Pubis does not take part in formation of acetabulum. Skull roof thickened, flat to dome-like. Supratemporal fenestra usually closed in highly domed forms. Antorbital fenestra occasionally present. Maxilla penetrated by extensive intramaxillary sinus. Epipterygoid present and being in contact with the prootic. Orbits anteriorly and medially closed by accessory sphenethmoidal ossifications. Quadrate with tendency to oblique po sition ofits dorsal portion. Jugal excluded from posterior boundary ofinfratemporal fenestra and together with quadratojugal strongly expanded ventrally to level ofarticular surface ofquadrate. Basicranial region strongly shortened (sag.), nearly completely separated from palatal and suborbital regions by extension of quadrate and pterygoid and by juncture of basisphenoid and prootic with quadrate wing of the pterygoid. Basal tubera thin, plate-like. Occipital and basicranial regions usually placed almost in the same vertical plane. Premaxillary dentition present, heterodonty more or less pronounced. Dentition weak, teeth arranged in one row, enameled on both sides. External skull bones strongly ornamented. Dorsal vertebrae mostly with tongue and groove articulation of zygapophyses. Caudal ribs strongly developed on anterior caudals. Tibia shorter or equal in length to femur. Pes tetradactyl.
R. M. Sullivan 2006	Ornithischian dinosaurs with thickened, fully-flat or incipiently to fully-domed frontoparietals, broad and flattened postorbital-squamosal bar; supratemporal fenestrae absent to well-developed; broad exposure of the occiput; quadrate and ventral surface of squamosal (occipital plate) directed anteroventrally; squamosals developed into deep plates on the occiput with greatly enlarged upper-outer corners; two supraorbital elements lateral to the frontal; arched premaxillary-maxillary diastema; broad postorbital-jugal bar, plate-shaped basal tubera, variably developed nodes on the squamosal (either in rows or clusters), nasals and other parts of the skull.