PBDB Taxon

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

Stegoceras

Reptilia

Taxonomy

Stegoceras was named by Lambe (1902). It is not extant. Its type is Stegoceras validus.

It was synonymized subjectively with Troodon by Gilmore (1924), Hay (1930).

It was assigned to Reptilia by Huene (1909); to Acanthopholididae by Nopcsa (1915); to Psalisauridae by Lambe (1918); to Ceratopsidae by Lambe (1902), Lambe (1905), Hatcher et al. (1907), Lambe (1911), Hennig (1915), Huene (1927); to Acanthopholidae by Nopcsa (1923), Nopcsa (1928), Nopcsa (1928); to Pachycephalosauroidea by Zhao (1983); to Pachycephalosauria by Maryanska and Osmólska (1985); to Tholocephalidae by Sereno (1986); to Eupachycephalosauria by Dieudonné et al. (2020); and to Pachycephalosauridae by Sternberg (1945), Romer (1956), Parsch (1963), Tatarinov (1964), Kuhn (1964), Romer (1966), Charig (1967), Russell and Chamney (1967), Swinton (1970), Maryańska and Osmólska (1974), Thulborn (1974), Galton (1974), Dong (1978), Wall and Galton (1979), Wolberg (1980), Molnar (1980), Rage (1981), Sues and Galton (1982), Dodson (1983), Russell (1984), Clemens (1986), Sues and Galton (1987), Carroll (1988), Maryanska (1990), Goodwin (1990), Olshevsky and Ford (1994), Sues (1997), Eberth (1997), Sereno (1997), Sereno (1998), Sereno (1999), Sereno (2000), Eberth et al. (2001), Sullivan (2003), Williamson and Carr (2003), Maryanska et al. (2004), Ryan and Evans (2005), Sullivan (2006), Williamson and Carr (2006), Sullivan and Lucas (2006), Longrich (2008), Butler et al. (2008), Schott et al. (2009), Jasinski and Sullivan (2011), Jasinski (2015), Woodruff et al. (2021).

Species

S. novomexicanum, S. validum (syn. Ornatotholus browni)

Synonyms

Ornatotholus was named by Galton and Sues (1983).

It was considered a nomen dubium by Williamson and Carr (2003); it was synonymized subjectively with Stegoceras by Sullivan (2003), Goodwin et al. (2004), Ryan and Evans (2005), Sullivan and Lucas (2006), Williamson and Carr (2006), Longrich et al. (2010), Jasinski and Sullivan (2011), Goodwin and Evans (2016).

It was assigned to Pachycephalosauridae by Russell (1984), Clemens (1986), Sues and Galton (1987), Carroll (1988), Maryanska (1990), Olshevsky and Ford (1994), Sues (1997); to Pachycephalosauria by Sereno (2000); and to Homalocephaloidea by Maryanska et al. (2004).
Hanssuessia was named by Sullivan (2003). It is not extant.

It was replaced with Hanssuesia by Sullivan (2003); it was synonymized subjectively with Stegoceras by Maryanska et al. (2004), Ryan and Evans (2005), Williamson and Carr (2006); it was corrected as Hansuessia by Longrich (2008).

It was assigned to Pachycephalosaurinae by Sullivan (2003); and to Pachycephalosauridae by Longrich (2008).

Synonymy list

Year	Name and author
1902	Stegoceras Lambe p. 68
1905	Stegoceras Lambe p. 49
1907	Stegoceras Hatcher et al. p. 97
1909	Stegoceras Huene p. 18
1911	Stegoceras Lambe p. 9
1915	Stegoceras Hennig p. 14
1915	Stegoceras Nopcsa p. 13
1918	Stegoceras Lambe p. 32
1923	Stegoceras Nopcsa p. 198
1927	Stegoceras Huene p. 261
1928	Stegoceras Nopcsa p. 73
1945	Stegoceras Sternberg pp. 535-6
1956	Stegoceras Romer p. 632
1963	Stegoceras Parsch p. 8
1964	Stegoceras Kuhn p. 31
1964	Stegoceras Tatarinov p. 589
1966	Stegoceras Romer p. 370
1967	Stegoceras Charig p. 716
1967	Stegoceras Russell and Chamney p. 11
1970	Stegoceras Swinton p. 231
1974	Stegoceras Galton p. 1064 fig. 6
1974	Stegoceras Maryańska and Osmólska p. 47
1974	Stegoceras Thulborn p. 173
1978	Stegoceras Dong p. 227
1979	Stegoceras Wall and Galton p. 1179
1980	Stegoceras Molnar p. 138
1980	Stegoceras Wolberg p. 50
1981	Stegoceras Rage p. 68
1982	Stegoceras Sues and Galton p. 188
1983	Stegoceras Dodson p. 95
1983	Ornatotholus Galton and Sues p. 469
1983	Stegoceras Zhao p. 304
1984	Ornatotholus Russell p. 25
1984	Stegoceras Russell p. 25
1985	Stegoceras Maryanska and Osmólska p. 141
1986	Ornatotholus Clemens p. 80
1986	Stegoceras Clemens p. 80
1986	Stegoceras Sereno
1987	Ornatotholus Sues and Galton
1987	Stegoceras Sues and Galton
1988	Ornatotholus Carroll
1988	Stegoceras Carroll
1990	Stegoceras Goodwin p. 191
1990	Ornatotholus Maryanska p. 566
1990	Stegoceras Maryanska p. 566
1994	Ornatotholus Olshevsky and Ford p. 91
1994	Stegoceras Olshevsky and Ford p. 91
1997	Stegoceras Eberth p. 201
1997	Stegoceras Sereno p. 443
1997	Ornatotholus Sues p. 512
1997	Stegoceras Sues p. 512
1998	Stegoceras Sereno p. 62
1999	Stegoceras Sereno p. 2138 fig. 2
2000	Stegoceras Sereno p. 482
2000	Ornatotholus Sereno p. 497 fig. 25.8
2001	Stegoceras Eberth et al. p. 57
2003	Stegoceras Sullivan p. 185
2003	Hanssuessia Sullivan p. 193 figs. 4-5
2003	Stegoceras Williamson and Carr fig. 11
2004	Ornatotholus Maryanska et al. p. 465
2004	Stegoceras Maryanska et al. p. 465
2005	Stegoceras Ryan and Evans p. 317
2006	Stegoceras Sullivan p. 357
2006	Stegoceras Sullivan and Lucas p. 329
2006	Stegoceras Williamson and Carr p. 323
2008	Stegoceras Butler et al. p. 8
2008	Hansuessia Longrich p. 994
2008	Stegoceras Longrich p. 994
2009	Stegoceras Schott et al. p. 781 fig. 8
2011	Stegoceras Jasinski and Sullivan p. 215
2015	Stegoceras Jasinski p. 79
2020	Stegoceras Dieudonné et al.
2021	Stegoceras Woodruff et al. p. 588 fig. 14

Is something missing? Join the Paleobiology Database and enter the data

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	()
—	Eupachycephalosauria
genus	Stegoceras

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.

G. †Stegoceras Lambe 1902

show all | hide all

†Stegoceras novomexicanum Jasinski and Sullivan 2011

†Stegoceras validum Lambe 1902

hide

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

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

Diagnosis

Reference	Diagnosis
C. M. Sternberg 1945	Small to medium-sized; thickness and position of dome variable: face short; skull more or less ornamented; premaxillae with teeth; premaxillary teeth pointed, with trenchant edges, faint marginal denticulations, faces of crown ribbed, posterior "heel"; maxillary and dentary teeth with well-pronounced denticulations extending onto both faces as flutings; supratemporal fossa nearly or quite closed; infratemporal fossa much reduced; premaxilla nearly excluded from lateral view; fore limb much reduced; four digits in the pes, first reduced.
S. E. Jasinski and R. M. Sullivan 2011	Differs from all other pachycephalosaurid genera in having a pronounced parietosquamosal shelf with an incipient frontoparietal dome; nasals inflated; postorbital situated posterolaterally on the dome; ornamentation consisting of numerous minute tubercles on lateral and posterior sides of squamosals with a prominent dorsal row of up to six tubercles on each squamosal adn as many as two nodes on the posteromedial extension of the parietal. Posteromedial extension of the parietal either sub-rectangular or trapezoidal in shape. Supratemporal fenetrae closed or open and relatively small, and positioned either adjacent or lateral to the midline. Stegoceras (sensu stricto) is late middle Campanian through early late Campanian (late Judithian-early Kirtlandian).

Measurements

No measurements are available

Composition:

hydroxyapatiteo

Entire body:

yesg

Adult length:

10 to < 100o

Adult width:

1.0 to < 10o

Adult height:

1.0 to < 10o

Maximum body mass:

100 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:

2005-08-25 05:49:46

Modified:

2005-08-25 07:49:46

Source: g = genus, o = order

References: Peczkis 1995, Marsh 1875

Age range: base of the Judithian to the top of the Late/Upper Maastrichtian or 83.60000 to 66.00000 Ma

Collections (42 total)

Time interval	Ma	Country or state	Original ID and collection number
Campanian	83.6 - 72.2	Canada (Alberta)	Psalisauridae indet. (64647 64657 64662) S. sp. (64661) S. validus (64646 64652 64658 64660) Troodon validus (64659 64663 64665)
Judithian	83.6 - 72.2	USA (Texas)	S. sp. (151416)
Late/Upper Campanian	83.6 - 72.2	Canada (Alberta)	Ornatotholus browni (47629 48619) S. validum (230768) S. validus (48618 60876) Stygimoloch sp. (76752) Troodon validus (53976 59107)
Late/Upper Campanian	83.6 - 72.2	USA (New Mexico)	Sphaerotholus goodwini (53514) S. novomexicanum (144518 144519 144520) S. validum, S. novomexicanum (76714)
Middle Campanian	83.6 - 72.2	USA (Montana)	S. sp. (14437)
Middle Campanian - Late/Upper Campanian	83.6 - 72.2	USA (Montana)	Ornatotholus browni (50829) Pachycephalosauridae indet. (50830) S. sp. (48620 50828 50906 50907) S. validum (14470 14491 50825 50826 50827 61452) S. validus (14446)
Middle Campanian - Late/Upper Campanian	83.6 - 72.2	Canada (Saskatchewan)	S. sp. (14494)
Late/Upper Maastrichtian	72.2 - 66.0	USA (Montana)	S. sp. (52903 72143)