PBDB Taxon

Basic info	Taxonomic history	Classification	Included Taxa
Morphology	Ecology and taphonomy	External Literature Search	Age range and collections

Pachycephalosauria

Reptilia

Taxonomy

Pachycephalosauria was named by Maryańska and Osmólska (1974). It was considered monophyletic by Butler et al. (2008).

It was reranked as the infraorder Pachycephalosauria by Cooper (1985); it was reranked as the unranked clade Pachycephalosauria by Sereno (2000), Buchholz (2002), Butler et al. (2008), Han et al. (2012), Dieudonné et al. (2020).

It was assigned to Neornithopoda by Cooper (1985); to Ornithischia by Maryańska and Osmólska (1974), Zhao (1983), Russell (1984), Maryanska and Osmólska (1985), Carroll (1988), Peng et al. (2001); and to Marginocephalia by Sereno (1986), Sues and Galton (1987), Benton (1990), Dodson (1990), Olshevsky and Ford (1994), Sereno (1997), Sereno (1998), Sereno (1999), Sereno (2000), Buchholz (2002), Weishampel (2004), Xu et al. (2006), Butler et al. (2007), Butler et al. (2008), Han et al. (2012), Dieudonné et al. (2020).

Subtaxa

Eupachycephalosauria, Goyocephale, Goyocephalia, Homalocephalidae, Pachycephalosauridae (syn. Tholocephalidae), Pachycephalosauroidea, Qiyunshanpus, Tianchungosauroidea, Tianyulong, Wannanosaurus

Synonymy list

Year	Name and author
1974	Pachycephalosauria Maryańska and Osmólska p. 50
1983	Pachycephalosauria Zhao pp. 299-300
1984	Pachycephalosauria Russell p. 29
1985	Pachycephalosauria Cooper p. 291
1985	Pachycephalosauria Maryanska and Osmólska p. 143 fig. 1
1986	Pachycephalosauria Sereno
1987	Pachycephalosauria Sues and Galton pp. 36-37
1988	Pachycephalosauria Carroll
1990	Pachycephalosauria Benton p. 19
1990	Pachycephalosauria Dodson p. 562
1994	Pachycephalosauria Olshevsky and Ford p. 91
1997	Pachycephalosauria Sereno p. 443
1998	Pachycephalosauria Sereno p. 62
1999	Pachycephalosauria Sereno p. 2138 fig. 2
2000	Pachycephalosauria Sereno p. 482
2001	Pachycephalosauria Peng et al. p. 36
2002	Pachycephalosauria Buchholz p. 20
2004	Pachycephalosauria Weishampel p. 323
2006	Pachycephalosauria Xu et al. p. 2139 fig. 3
2007	Pachycephalosauria Butler et al. p. S18 fig. S2
2008	Pachycephalosauria Butler et al. pp. 21-22
2012	Pachycephalosauria Han et al. p. 1391 fig. 14
2020	Pachycephalosauria Dieudonné et al.

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Rank	Name	Author
kingdom	Animalia	()
—	Bilateria
—	Eubilateria	Ax 1987
—	Deuterostomia
phylum	Chordata	Haeckel 1874
subphylum	Vertebrata
superclass	Gnathostomata
—	Eugnathostomata
—	Teleostomi	(Bonaparte 1836)
subclass	Sarcopterygii	()
subclass	Dipnotetrapodomorpha	(Nelson 2006)
subclass	Tetrapodomorpha	()
—	Tetrapoda
—	Reptiliomorpha
—	Anthracosauria
subclass	Amphibiosauria	Kuhn 1967
—	Cotylosauria	()
—	Amniota
—	Sauropsida
class	Reptilia

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

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.

Unr. †Pachycephalosauria Maryańska and Osmólska 1974

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Unr. †Eupachycephalosauria Dieudonné et al. 2020

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G. †Homalocephale Maryańska and Osmólska 1974

†Homalocephale calathocercos Maryańska and Osmólska 1974

G. †Pachycephalosaurus Brown and Schlaikjer 1943

†Pachycephalosaurus wyomingensis Gilmore 1931

Invalid names: Dracorex hogwartsia Bakker et al. 2006 [synonym], Pachycephalosaurus grangeri Brown and Schlaikjer 1943 [synonym], Pachycephalosaurus reinheimeri Brown and Schlaikjer 1943 [synonym], Stygimoloch spinifer Galton and Sues 1983 [synonym], Tylosteus ornatus Leidy 1872 [synonym]

Invalid names: Dracorex Bakker et al. 2006 [synonym], Stygimoloch Galton and Sues 1983 [synonym], Tylosteus Leidy 1872 [synonym]

G. †Prenocephale Maryańska and Osmólska 1974

†Prenocephale prenes Maryańska and Osmólska 1974

G. †Stegoceras Lambe 1902

†Stegoceras novomexicanum Jasinski and Sullivan 2011

†Stegoceras validum Lambe 1902

Invalid names: Ornatotholus browni Wall and Galton 1979 [synonym]

Invalid names: Hanssuessia Sullivan 2003 [synonym], Ornatotholus Galton and Sues 1983 [synonym]

G. †Goyocephale Perle et al. 1982

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†Goyocephale lattimorei Perle et al. 1982

Infraor. †Goyocephalia Sereno 1986

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Invalid names: Homalocephaloidea Sereno 1986 [empty]

Fm. †Pachycephalosauridae Sternberg 1945

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G. †Amtocephale Watabe et al. 2011

†Amtocephale gobiensis Watabe et al. 2011

G. †Colepiocephale Sullivan 2003

†Colepiocephale lambei Sternberg 1945

G. †Hanssuesia Sullivan 2003

†Hanssuesia sternbergi Brown and Schlaikjer 1943

Subfm. †Pachycephalosaurinae Sereno 1997

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

G. †Alaskacephale Sullivan 2006

†Alaskacephale gangloffi Sullivan 2006

G. †Sinocephale Evans et al. 2021

†Sinocephale bexelli Bohlin 1953

G. †Tylocephale Maryańska and Osmólska 1974

†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]

G. †Qiyunshanpus Yu 1998

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Invalid names: Qiyunshanpus xiaohutianensis Yu 1998 [nomen nudum]

G. †Tianyulong Zheng et al. 2009

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†Tianyulong confuciusi Zheng et al. 2009

G. †Wannanosaurus Hou 1977

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†Wannanosaurus yansiensis Hou 1977

Invalid names: Homalocephalidae Dong 1978 [empty], Pachycephalosauroidea Zhao 1983 [empty], Tianchungosauroidea Zhao 1983 [empty]

Diagnosis

No diagnoses are available

Measurements

No measurements are available

Composition:

hydroxyapatiteo

Entire body:

yeso

Adult length:

10 to < 100o

Adult width:

1.0 to < 10o

Adult height:

1.0 to < 10o

Maximum body mass:

1000 kgg

Minimum body mass:

10 kgg

Architecture:

compact or denseo

Ontogeny:

accretion, modification of partso

Grouping:

gregariouso

Environment:

terrestrialo

Locomotion:

actively mobileo

Life habit:

ground dwellingo

Diet:

herbivoreo

Reproduction:

oviparouso

Dispersal:

direct/internalo

Dispersal 2:

mobileo

Created:

2004-12-14 12:50:52

Modified:

2004-12-14 14:50:52

Source: g = genus, o = order

References: Peczkis 1995, Marsh 1875

Age range: base of the Late/Upper Bathonian to the top of the Lancian or 168.20000 to 66.00000 Ma

Collections (162 total)

Time interval	Ma	Country or state	Original ID and collection number
Late/Upper Bathonian - Early/Lower Kimmeridgian	168.2 - 152.21	China (Liaoning)	Tianyulong confuciusi (92421)
Cenomanian - Santonian	100.5 - 83.6	Mongolia (Omnogov)	Pachycephalosauria indet. (127666)
Late/Upper Santonian	85.7 - 83.6	Canada (Alberta)	Acrotholus audeti (125521) Stegoceras sp. (68656)
Santonian - Maastrichtian	85.7 - 66.0	Mongolia (Omnogov)	Goyocephale lattimorei (13284)
Campanian	83.6 - 72.2	Canada (Alberta)	Psalisauridae indet. (64647 64657 64662) Stegoceras brevis (64649 64650 64651) Stegoceras sp. (64661) Stegoceras validus (64646 64652 64658 64660) Troodon sternbergi (64648 64656) Troodon validus (64659 64663 64665)
Early/Lower Campanian	83.6 - 72.2	Mexico (Coahuila)	Pachycephalosauridae indet. (113768)
Early/Lower Campanian - Middle Campanian	83.6 - 72.2	USA (Utah)	Pachycephalosauridae indet. (230891)
Judithian	83.6 - 72.2	USA (Texas)	Stegoceras sp. (151416) Troodon sp. (14488 14489)
Late/Upper Campanian	83.6 - 72.2	Canada (Alberta)	Ornatotholus browni (47629 48619) Pachycephalosauridae indet. (22697 45261 45262 45264 45671 45898 45899 47816 67871 67873 89604 89605) Pachycephalosaurus sp. (59222) Sphaerotholus lyonsi (233410) Stegoceras brevis, Stegoceras validus (60877) Stegoceras validum (230768) Stegoceras validus (48618 60876) Stygimoloch sp. (76752) Troodon validus (53976 59107)
Late/Upper Campanian	83.6 - 72.2	USA (Montana)	Pachycephalosauridae indet. (59373)
Late/Upper Campanian	83.6 - 72.2	USA (Texas)	Stegoceras sp. (96599 96600 96601) Texacephale langstoni (94373)
Late/Upper Campanian	83.6 - 72.2	USA (New Mexico)	Pachycephalosauria indet. (53515) Pachycephalosauridae indet. (36541 53517) Prenocephale sp. (47821) Sphaerotholus goodwini (53514) Stegoceras novomexicanum (144518 144519 144520) Stegoceras validum, Stegoceras novomexicanum (76714)
Middle Campanian	83.6 - 72.2	Canada (Alberta)	Gravitholus albertae (72144) Pachycephalosauridae indet. (45240 45560 45564 45566 45567 47794 47795 47809 67884 181024) Stegoceras sp. (59378 59379) Troodon sp. (64654)
Middle Campanian	83.6 - 72.2	USA (Montana)	Pachycephalosauridae indet. (22691) Stegoceras sp. (14437)
Middle Campanian - Late/Upper Campanian	83.6 - 72.2	Canada (Alberta)	Pachycephalosauridae indet. (45819 45821)
Middle Campanian - Late/Upper Campanian	83.6 - 72.2	USA (Texas)	Pachycephalosauridae indet. (68001 68003) Texacephale langstoni (22709)
Middle Campanian - Late/Upper Campanian	83.6 - 72.2	USA (Montana)	Ornatotholus browni (50829) Pachycephalosauridae indet. (50830) Stegoceras sp. (48620 50828 50906 50907) Stegoceras validum (14470 14491 50825 50826 50827 61452) Stegoceras validus (14446)
Middle Campanian - Late/Upper Campanian	83.6 - 72.2	Mongolia (Omnogov)	Pachycephalosauridae indet. (181419)
Middle Campanian - Late/Upper Campanian	83.6 - 72.2	Canada (Saskatchewan)	Stegoceras sp. (14494)
Campanian - Maastrichtian	83.6 - 66.0	China (Anhui)	Qiyunshanpus xiaohutianensis (60502)
Campanian - Maastrichtian	83.6 - 66.0	China (Nei Mongol)	Troodon bexelli (50733)
Late/Upper Campanian - Early/Lower Maastrichtian	83.6 - 66.0	Canada (Alberta)	Pachycephalosauridae indet. (162136)
Late/Upper Campanian - Maastrichtian	83.6 - 66.0	Canada (Alberta)	Troodon edmontonensis (64653)
Early/Lower Maastrichtian	72.2 - 66.0	Canada (Alberta)	Pachycephalosauridae indet. (229870)
Early/Lower Maastrichtian	72.2 - 66.0	USA (Alaska)	Pachycephalosaurinae indet. (53494)
Early/Lower Maastrichtian	72.2 - 66.0	China (Anhui)	Wannanosaurus yansiensis (24904)
Lancian	72.2 - 66.0	USA (Wyoming)	Pachycephalosaurus sp. (72145) Stygimoloch spinifer (14544)
Lancian	72.2 - 66.0	USA (North Dakota)	Pachycephalosauridae indet. (137712 137715)
Lancian	72.2 - 66.0	USA (South Dakota)	Pachycephalosauria indet. (48235) Pachycephalosauridae indet. (14537 192251)
Lancian	72.2 - 66.0	USA (Montana)	Pachycephalosaurus sp. (14616) Stygimoloch spinifer (14550)
Late/Upper Maastrichtian	72.2 - 66.0	USA (South Dakota)	Pachycephalosaurus sp., Dracorex hogwartsia (224484) Pachycephalosaurus wyomingensis, Pachycephalosaurus reinheimeri (47628)
Late/Upper Maastrichtian	72.2 - 66.0	USA (Wyoming)	Pachycephalosauridae indet. (22638 239131) Pachycephalosaurus grangeri (14585) Pachycephalosaurus sp. (26760) Pachycephalosaurus wyomingensis (64644) Triceratops sp. (64645) Troodon wyomingensis (52106)
Late/Upper Maastrichtian	72.2 - 66.0	Canada (Alberta)	Pachycephalosaurus sp. (168404)
Late/Upper Maastrichtian	72.2 - 66.0	USA (Colorado)	Pachycephalosaurus sp. (49539)
Late/Upper Maastrichtian	72.2 - 66.0	Canada (Saskatchewan)	Pachycephalosauridae indet. (54105) Pachycephalosaurinae indet. (223799) Sphaerotholus buchholtzae (170675)
Late/Upper Maastrichtian	72.2 - 66.0	USA (Montana)	Pachycephalosauridae indet. (13142) Pachycephalosaurus sp. (183110) Pachycephalosaurus wyomingensis (52904 161171) Pachycephalosaurus wyomingensis, Sphaerotholus triregnum (152397) Platytholus clemensi (230093) Stegoceras sp. (52903 72143) Tylosteus ornatus (91359)
Maastrichtian	72.2 - 66.0	USA (South Dakota)	Dracorex hogwartsia (58813) Pachycephalosauria indet. (74175)
Maastrichtian	72.2 - 66.0	Mongolia (Omnogov)	Ornithischia indet. (180473) Pachycephalosauria indet. (55257 127670 127675 127679 168810) Pachycephalosauridae indet. (127681 180706) Pachycephalosauridae indet., Homalocephale calathocercos (37019)
Maastrichtian	72.2 - 66.0	USA (North Dakota)	Stygimoloch spinifer (48843)
Maastrichtian	72.2 - 66.0	USA (Montana)	Pachycephalosauridae indet. (85498 85499) Pachycephalosaurus grangeri (47627) Pachycephalosaurus sp. (88987 88988) Predentata indet. (48848) Stegoceras edmontonense (53516) Stenotholus kohleri (12977) Stygimoloch spinifer (47626 48844 48845 48846)