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The oldest centrosaurine: a new ceratopsid dinosaur (Dinosauria: Ceratopsidae) from the Allison Member of the Menefee Formation (Upper Cretaceous, early Campanian), northwestern New Mexico, USA

Authors:
  • New Mexico Museum of Natural History and Science
  • State Museum of Pennsylvania, Harrisburg, PA
  • New Mexico Museum of Natural History and Science

Abstract and Figures

An associated incomplete skeleton of a ceratopsid dinosaur from the Campanian deposits of the Allison Member of the Menefee Formation in New Mexico, USA is described. Although it was originally described over two decades ago, newly prepared portions of the Menefee Formation skeleton and reinterpretations of previously known morphology, in addition to newly described specimens have provided new information on ceratopsids, and centrosaurines in particular. These new data allow for a thorough reassessment of the specimen and the erection of a new taxon: Menefeeceratops sealeyi gen. et sp. nov., potentially the oldest recognized member of Centrosaurinae. Menefeeceratops sealeyi is represented by diagnostic cranial and postcranial skeletal elements. The cranial elements include a portion of the left premaxilla, a nearly complete left postorbital horncore, a parietal fragment, the right and left squamosals, the left jugal, the predentary, and the left dentary. Postcranial material consists of two cervical vertebrae, eight dorsal vertebrae, a partial sacrum with six sacral vertebrae, 11 dorsal ribs, the distal left radius, proximal and distal portions of the left ulna, the left femur, and a left metatarsal II. The taxonomic validity of Menefeeceratops sealeyi is supported by a combination of several morphological characters. These include a lack of epiossifications on the lateroposterior edge of the parietal (shared with Machairoceratops), three epiossifications on the squamosal, and three smaller, secondary undulations as part of episquamosal locus S1. There are also two subequal embayments on the posterior free margin of the squamosal with the more dorsal embayment (between episquamosal loci 1 and 2) distinctly larger than the ventral (= lateroventral) one (between episquamosal loci 2 and 3), three ridges on the lateral (dorsolateral) surface of the squamosal, an elongate posterior portion of the squamosal, the presence of a shallow but distinct groove on the medial surface of the squamosal nearly paralleling the ventrolateral and ventroposterior edges, elongate postorbital (= supraorbital) horns that are anteriorly curved distally, and two elongate ridges on the lateral surface of the dentary that diverge anteriorly, creating a distinct anterior triangular fossa. Phylogenetic analysis of Menefeeceratops sealeyi places this new species as a basal centrosaurine, most closely related to Crittendenceratops krzyzanowskii, thus adding to the growing record of centrosaurines discovered in western North America. It thus provides new information about the diversity of morphologies throughout different species and the temporal and paleobiogeographic distribution of these animals throughout Laramidia during the Late Cretaceous. Its presence as one of the, if not the, oldest members of the Centrosaurinae also suggests centrosaurines originated in the southern portions of western North America and the southern Rocky Mountain region, and subsequently radiated north during the upper middle to late Campanian.
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PalZ
https://doi.org/10.1007/s12542-021-00555-w
RESEARCH PAPER
The oldest centrosaurine: anew ceratopsid dinosaur (Dinosauria:
Ceratopsidae) fromtheAllison Member oftheMenefee Formation
(Upper Cretaceous, early Campanian), northwestern New Mexico, USA
SebastianG.Dalman1· SpencerG.Lucas1· StevenE.Jasinski2,3 · AsherJ.Lichtig1· PeterDodson3,4
Received: 30 April 2020 / Accepted: 9 March 2021
© Paläontologische Gesellschaft 2021
Abstract
An associated incomplete skeleton of a ceratopsid dinosaur from the Campanian deposits of the Allison Member of the
Menefee Formation in New Mexico, USA is described. Although it was originally described over two decades ago, newly
prepared portions of the Menefee Formation skeleton and reinterpretations of previously known morphology, in addition
to newly described specimens have provided new information on ceratopsids, and centrosaurines in particular. These new
data allow for a thorough reassessment of the specimen and the erection of a new taxon: Menefeeceratops sealeyi gen. et
sp. nov., potentially the oldest recognized member of Centrosaurinae. Menefeeceratops sealeyi is represented by diagnostic
cranial and postcranial skeletal elements. The cranial elements include a portion of the left premaxilla, a nearly complete left
postorbital horncore, a parietal fragment, the right and left squamosals, the left jugal, the predentary, and the left dentary.
Postcranial material consists of two cervical vertebrae, eight dorsal vertebrae, a partial sacrum with six sacral vertebrae, 11
dorsal ribs, the distal left radius, proximal and distal portions of the left ulna, the left femur, and a left metatarsal II. The
taxonomic validity of Menefeeceratops sealeyi is supported by a combination of several morphological characters. These
include a lack of epiossifications on the lateroposterior edge of the parietal (shared with Machairoceratops), three epios-
sifications on the squamosal, and three smaller, secondary undulations as part of episquamosal locus S1. There are also two
subequal embayments on the posterior free margin of the squamosal with the more dorsal embayment (between episquamosal
loci 1 and 2) distinctly larger than the ventral (= lateroventral) one (between episquamosal loci 2 and 3), three ridges on the
lateral (dorsolateral) surface of the squamosal, an elongate posterior portion of the squamosal, the presence of a shallow
but distinct groove on the medial surface of the squamosal nearly paralleling the ventrolateral and ventroposterior edges,
elongate postorbital (= supraorbital) horns that are anteriorly curved distally, and two elongate ridges on the lateral surface
of the dentary that diverge anteriorly, creating a distinct anterior triangular fossa. Phylogenetic analysis of Menefeeceratops
sealeyi places this new species as a basal centrosaurine, most closely related to Crittendenceratops krzyzanowskii, thus
adding to the growing record of centrosaurines discovered in western North America. It thus provides new information
about the diversity of morphologies throughout different species and the temporal and paleobiogeographic distribution of
these animals throughout Laramidia during the Late Cretaceous. Its presence as one of the, if not the, oldest members of the
Centrosaurinae also suggests centrosaurines originated in the southern portions of western North America and the southern
Rocky Mountain region, and subsequently radiated north during the upper middle to late Campanian.
Keywords Dinosauria· Ceratopsidae· Centrosaurinae· Late Cretaceous· New Mexico· North America· Taxonomy·
Evolution
Introduction
During the Campanian age of the Late Cretaceous, centro-
saurine ceratopsians were among the most common terres-
trial herbivores in the western landmass of North America
known as Laramidia with a geographic range extending
from Alaska (Fiorillo and Gangloff 2003; Fiorillo etal.
Handling Editor: Hans-Dieter Sues.
* Sebastian G. Dalman
sebastiandalman@yahoo.com
Extended author information available on the last page of the article
S. G. Dalman etal.
1 3
2010; Fiorillo and Tykoski 2012; Tykoski and Fiorillo 2013)
through Alberta, Canada (Lambe 1904, 1913; Sternberg
1950; Ryan and Russell 2005; Ryan 2007; Ryan etal. 2007;
Currie etal. 2008; Farke etal. 2011; Ryan etal. 2012a, b;
Evans and Ryan 2015), Montana (Dodson 1986; Sampson
1995; McDonald and Horner 2010; Ryan etal. 2010; Chiba
etal. 2018), Utah (Kirkland and DeBlieux 2010; Loewen
etal. 2013a; Sampson etal. 2013) Arizona (Dalman etal.
2018), New Mexico (Wolfe and Kirkland 1998; Wolfe 2000),
to Mexico (Murray etal. 1960; Loewen etal. 2010; Rivera-
Sylva and Carpenter 2014; Rivera-Sylva etal. 2016, 2017).
In the past decade, the discovery of new specimens and
species of centrosaurines in the Belly River Group, the Old-
man Formation of southern Alberta (Evans and Ryan 2015;
Ryan etal. 2017), the Fort Crittenden Formation of Arizona
(Dalman etal. 2018), the Wahweap and Kaiparowits forma-
tions of Utah (Sampson etal. 2013; Lund etal. 2016a, b),
the Aguja Formation of Mexico (Rivera-Sylva etal. 2016,
2017), and the Cerro del Pueblo Formation of Mexico
(Loewen etal. 2010) provide new information about both
the morphologic and taxonomic diversity as well as the wide
paleobiogeographic range of the Centrosaurinae throughout
the Late Cretaceous in Laramidia (Ryan etal. 2017; Dalman
etal. 2018). However, at present, the fossil record of the
stratigraphically oldest (early Campanian) centrosaurines is
poorly documented due to the largely fragmentary material
and relatively limited collection history.
The 1996 discovery of a partial, associated centrosaurine
ceratopsid skeleton (Fig.1), in the lower Campanian Alli-
son Member of the Menefee Formation, New Mexico, pro-
vides important new insights into the origin and evolution of
Centrosaurinae in North America. The specimen was briefly
described by Williamson (1997), who identified it only to
the subfamily level Centrosaurinae based on the overall mor-
phology of the left squamosal which has the characteristic
“stepped” squamosal-parietal contact (Ryan 2007), a feature
that is present in almost all known centrosaurines with the
parietal-squamosal sutural surface preserved, including nas-
utoceratopsins (Dalman etal. 2018), although Avaceratops
is a notable exception. The left parietal of the Menefee For-
mation centrosaurine is incomplete and highly fragmentary;
therefore, whether it had or lacked the epiparietal ornamen-
tation is unknown. However, the lack of parietal ornamen-
tation is a common characteristic of juvenile and sub-adult
centrosaurines (Sampson etal. 1997). This characteristic
parietal morphology is present in some centrosaurines, par-
ticularly in some nasutoceratopsins, such as Avaceratops
lammersi (Dodson 1986) from the Judith River Formation
of Montana, and Nasutoceratops titusi (Sampson etal. 2013)
from the Kaiparowits Formation of Utah. The type specimen
of Avaceratops is ontogenetically younger than that of Nasu-
toceratops; however, both genera have unadorned parietals
(Sampson etal. 2013; Ryan etal. 2017). Undulations on the
frill margin are also present outside of the Ceratopsidae in
the protoceratopsid Protoceratops (e.g., Chiba etal. 2019),
although this only occurs in a few individuals and is not
characteristic of the genus. Here, we provide a complete
osteological description of the Menefee Formation centro-
saurine and report on several additional cranial and postcra-
nial skeletal elements not described by Williamson (1997)
and place it in a phylogenetic context for the first time. As a
result, we identify it as a new genus and species, here des-
ignated Menefeeceratops sealeyi gen. et sp. nov., that dates
to the late early Campanian, making it potentially the oldest
member of the Centrosaurinae.
Materials andmethods
Paul Sealey discovered the partial skeleton of this centro-
saurine ceratopsian in the Allison Member of the Menefee
Formation in northwestern New Mexico. All of the collected
fossils are catalogued in the paleontology collection of New
Mexico Museum of Natural History and Science in Albu-
querque, New Mexico (NMMNH) where they were also
prepared. All measurements of the specimens were taken
using a standard metric ruler. TNT (Tree analysis using New
Technology) (Goloboff etal. 2008; Goloboff and Catalano
Fig. 1 Menefeeceratops sealeyi
gen. et sp. nov. skeletal recon-
struction, elements represented
in the material collected from
the bonebed are indicated in
blue (modified from Nasu-
toceratops titusi from Sampson
etal. 2013)
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
2016) was used for the phylogenetic analyses. To assess the
systematic position of Menefeeceratops sealeyi, we coded it
into the character dataset generated by Mallon etal. (2016)
and Dalman etal. (2018) (S1 File). Tree statistics, including
the consistency index (CI), retention index (RI), and Bremer
support values were calculated using TNT under default
parameters (Goloboff etal. 2008; Goloboff and Catalano
2016).
Institutional abbreviations used in the present study are
(including Online Resources): ANSP—Academy of Natural
Sciences, Philadelphia, Pennsylvania, USA; CMN—Cana-
dian Museum of Nature, Ottawa, Ontario, Canada; CPC—
Colección Paleontológica de Coahuila, Saltillo, Mexico;
GPDM—Great Plains Dinosaur Museum, Malta, Montana,
USA; MOR—Museum of the Rockies, Bozeman, Montana,
USA; NMMNH—New Mexico Museum of Natural His-
tory and Science, Albuquerque, New Mexico, USA; ROM—
Royal Ontario Museum, Toronto, Canada; TMP—Royal
Tyrrell Museum of Palaeontology, Drumheller, Alberta,
Canada; UALVP—University of Alberta Laboratory of
Vertebrate Paleontology, Edmonton, Canada; UCMP—
University of California Museum of Paleontology, Berke-
ley, California, USA; UMNH—Utah Museum of Natural
History, Salt Lake City, Utah, USA; YPM—Yale Peabody
Museum of Natural History, New Haven, Connecticut, USA.
Anatomical abbreviations used in figure captions of this
article: aceb, acetabular bar; adpd, anterodorsal predentary
contact surface on dentary; af, anterior fossa; alpr, antero-
lateral (= rostrolateral) process of ulna; altf, anterolateral
triangular fossa; amfc, anteromedial fossa of coronoid pro-
cess; amrc, anteromedial ridge of coronoid process; an c,
angular contact; atetr, anterior terminal end of dentary tooth
row; avpd, anteroventral predentary contact surface on den-
tary; cap, capitulum; cas, carpus articulation surface of the
radius; con, condyle; cot, cotyle; crp, coronoid process; cs,
cornual sinus; dgs, dorsal groove of squamosal; diap, dia-
pophysis; dlr, dorsolateral ridge of squamosal; dppd, dorsal
process of the predentary; dsp, dorsal squamosal process;
dsvc, dorsosacral vertebra centrum; em, embayment; eop
c, exoccipital contact; epj c, epijugal contact surface; esp,
external squamosal protuberance (= dorsal squamosal pro-
cess, = squamosal swelling); fh, femoral head; icf, intercon-
dylar fossa; jc, jugal contact; lc, lateral condyle; ldr, latero-
dorsal ridge of dentary; lf, lateral fossa; lgt, long-grained
texture; llam, lingual lamina of dentary; lr, lateral ridge of
squamosal; lvr, lateroventral ridge of dentary; M-Ic, meta-
tarsal I contact; M-IIIc, metatarsal III contact; mc, medial
condyle; mf, mental foramen; mg, Meckelian groove; mlfd,
midlateral fossa of dentary; mpr, medial process of ulna;
na, neural arch; nc, neural canal; ne, natural edge; ns, neural
spine; or, orbital rim; ol, olecranon; otn, otic notch; osks,
offset swelling for keratinous sheath; pac, parietal con-
tact; papo, parapophysis; path, pathology; pdc, predentary
contact surface; pdlr, primary dorsolateral ridge of squa-
mosal; pmfc, posteromedial (= caudomedial) fossa of coro-
noid process; pmrc, posteromedial (= caudomedial) ridge of
coronoid process; pog, paraoccipital groove; po-sc, postor-
bital-squamosal contact; pp, pubic peduncle; ptetr, posterior
(= caudal) terminal end of tooth row; qc, quadrate contact;
qjc, quadratojugal contact; pozg, postzygapophysis; rcpm,
rostrum contact of the premaxilla; rdg, ridge; rs, rugose
surface; S1–S9, episquamosal loci; sac, surangular contact;
sdlr, secondary (= second) dorsolateral ridge of squamosal;
soh, supraorbital horncore; splc, splenial contact surface; sr,
sacral rib; ss, symphyseal surface of dentary; step, stepped
parietosquamosal contact; t4, 4th trochanter; tdlr, tertiary
(= third) dorsolateral ridge of squamosal; tp, transverse
process; tr, tooth row; trn, trochlear notch; tspd, triturating
surface of predentary; tub, tuberculum; u, undulations; uc,
ulna contact surface of the radius; vasg, vascular grooves;
vg, ventral groove; vgs, ventral groove of the sacrum; vppd,
ventral process of predentary.
Geologic setting
The Menefee Formation is the middle unit of the Mesaverde
Group and has a broad outcrop belt around the San Juan
Basin of northwestern New Mexico and southwestern Colo-
rado (Fig.2). It encompasses three members (in ascending
order), the Cleary Coal Member, the Allison Member and
an upper coal member that is unnamed (Molenaar 1983;
Beaumont and Hoffman 1992; Mannhard 1997). The Cleary
Coal Member is 31–61m thick and consists of mudstone,
siltstone, sandstone and coal beds. It interfingers with and
overlies the Point Lookout Sandstone (basal formation of
the Mesaverde Group), which represents regressive, shore-
line deposits of the Western Interior Seaway. The Allison
Member is 122–183m thick and consists of mudstone,
sandstone and siltstone beds that mostly represent fluvial
deposition during the regression. However, the transgres-
sion of the overlying Cliff House Sandstone shoreline began
during the deposition of the uppermost Allison Member.
The unnamed upper coal member is as much as 160m thick
and is lithologically similar to the Cleary Coal Member. It
interfingers with and is overlain by the La Ventana Tongue
of the Cliff House Sandstone, a succession of barrier-beach
and nearshore marine sandstone.
Ammonoid biostratigraphy of the bracketing marine units
indicates the Menefee Formation is early Campanian in age
(Obradovich 1993; Lucas etal. 2005). Particularly relevant
to the age of Menefeeceratops is the oldest ammonoid zone
of the overlying Cliff House Sandstone, the zone of Bacu-
lites obtusus, which has an age of 81–80Ma based on the
numerical calibration of Western Interior ammonoid zones
(though, there may be some imprecision in this calibration:
(Obradovich 1993; Ogg and Hinnov 2012). If we accept that
S. G. Dalman etal.
1 3
age, then Menefeeceratops is older than 81–80Ma, though
exactly how much older cannot be determined with current
data.
Lewis etal. (2006, 2007, 2008) used the biostratigra-
phy of the fossil vertebrates to determine an approximate
age of the Allison Member. In particular, they used the co-
occurrence of the shark Scapanorhynchus raphiodon with
several other taxa to derive an age of 83.5–80Ma (Lewis
etal. 2008). Lewis etal. (2006) concluded that the Allison
Member corresponds to the late Aquilan North American
land-vertebrate “age.” Therefore, we conservatively assign
an approximate age of 82–81Ma to Menefeeceratops,
although it may be as old as 83.5Ma or as young as 80Ma.
The Menefee Formation represents a fluvio-deltaic depo-
sitional environment but also encompasses a variety of sub-
environments. Lewis etal. (2008) reported the paleoenvi-
ronment as an alluvial floodplain as part of a deltaic setting
with a southwest–northeast paleoflow, poor drainage, and
commonly swampy environments. Further investigation of
the aquatic fauna reveals it is composed of 73% freshwater or
freshwater-tolerant taxa and 27% marine forms, and, when
combined with the geochemistry of the siderite from the site,
indicates a dominantly freshwater paleoenvironment with
regular marine influence, indicating a depositional setting
of a distal alluvial floodplain to proximal estuary (Lewis
etal. 2008).
Fig. 2 Geographic and
chronostratigraphic position of
Menefeeceratops sealeyi gen.
et sp. nov., NMMNH P-25052.
Chronostratigraphic position of
the Menefee Formation (after
Williamson, 1997) with place-
ment of type locality NMMNH
L-3033 indicated, along with
inset map (upper right) showing
the outcrops of the Menefee
Formation (early Campanian),
Allison Member northwestern
New Mexico, United States and
the location of the Menefeecera-
tops sealeyi gen. et sp. nov. type
locality (NMMNH L-3033)
within the area in northwestern
New Mexico, United States
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
The Menefee Formation is one of several nonmarine ver-
tebrate faunal assemblages of early Campanian age in North
America, which thus far has yielded only fragmentary skel-
etal materials, particularly of dinosaurs, with most of the
specimens only identifiable to the family level (Russell 1964;
Weishampel 1990; Parrish 1991; Hunt and Lucas 1993; Wil-
liamson and Sealey 1995; Williamson 1997; Dalman etal.
2016; Dalman and Lucas 2018). These include the following
families: Ankylosauridae, Ceratopsidae, Dromaeosauridae,
Hadrosauridae, and Tyrannosauridae (Hunt and Lucas 1993;
Williamson 1996; Williamson and Sealey 1996). However,
recently the descriptions of new dinosaur species recovered
from the Allison Member shed new light on the dinosaur
fauna of the Menefee Formation, which include a nodosaurid
ankylosaur Invictarx zephyri (McDonald and Wolfe 2018)
and tyrannosaurid Dynamoterror dynastes (McDonald etal.
2018).
Phylogenetic analysis
To assess the systematic position of Menefeeceratops sea-
leyi gen. et sp. nov., the holotype NMMNH P-25052 was
coded and placed into a matrix modified from the combina-
tion of Mallon etal. (2016) and Dalman etal. (2018) (see
supplemental data). New characters include those dealing
with parietal and squamosal morphology (characters 88, 91,
108, 110, 117), epiossifications (characters 99, 125, 127,
129, 131, 132, 133, 137, 140, 141), supraorbitals (charac-
ters 14, 78, 80), and jugal morphology (characters 55, 56,
57, 58, 59, 60, 61, 62, 66) (see supplemental data). These
new characters were used to better explore the interrelation-
ships of Menefeeceratops with other ceratopsids, particularly
other centrosaurines. The leptoceratopsid neoceratopsian
Leptoceratops gracilis was used as the outgroup due to its
accepted position basally within the Coronosauria and out-
side of the more derived coronosaurs, including Protocera-
topsidae, Zuniceratops, Turanoceratops, and the Ceratopsi-
dae. The data matrix was analyzed in TNT under parsimony
with 99,999 maximum trees; 10,000 Wagner trees replicates
followed by a TBR sequence using default parameters. The
resulting trees were assessed using the tree statistics pack-
age in TNT, with consistency index (CI), retention index
(RI), and Bremer support values calculated (Goloboff etal.
2008; Goloboff and Catalano 2016). Bootstrap values were
calculated using 1000 replicates under standard weighting
and default settings. The phylogenetic analysis includes 53
total OTUs (= operational taxonomic units) with 1 outgroup
and 52 in-group taxa, and 252 total characters.
Nomenclatural acts
The electronic edition of this article conforms to the requirements
of the amended International Code of Zoological Nomenclature,
and hence the new names contained herein are available under
that Code from the electronic edition of this article. This published
work and the nomenclatural acts it contains have been registered
in ZooBank, the online registration system of the ICZN. The Zoo-
Bank Life Science Identifiers (LSIDs) can be resolved and the
associated information viewed through any standard web browser
by appending the LSID to the prefix “http:// zooba nk. org/”.
The LSID for this publication is: urn:lsid:zoobank.org:pub:
11981EB1-444D-4647-98C5-39D16F0DD196. The electronic
edition of this work was published in a journal with an ISSN,
and has been archived and is available from the following digital
repositories: LOCKSS (http:// www . lockss. org); PubMed Central
(http:// www. ncbi. nlm. nih. gov/ pmc).
Systematic paleontology
Ornithischia Seeley, 1887
Ceratopsia Marsh, 1890
Neoceratopsia Sereno, 1986
Ceratopsidae Marsh, 1888
Centrosaurinae Lambe, 1915
Menefeeceratops gen. nov.
Type species. Menefeeceratops sealeyi gen. et sp. nov.
Diagnosis. As for the only species.
ZooBank LSID. urn:lisd:zoobank.
org:act:7D2D366D-8A05-4DBB-8FDA-6E503612F4C3.
Menefeeceratops sealeyi gen. et sp. nov.
Figures4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
22a and 24
Material. Holotype. NMMNH P-25052, a fragmentary skeleton
consisting of the following elements: a left partial premaxilla,
the nearly complete left postorbital horncore, a partial right
squamosal, the left squamosal, an incomplete left parietal, the
left jugal, the predentary, the left dentary, one cervical vertebra,
eight dorsal vertebrae, a partial sacrum consisting of six sacral
vertebrae, 11 dorsal ribs, the left ilium, the distal left radius, the
proximal and distal portions of left ulna, the left metatarsal II,
the left femur, and the distal end left fibula.
The holotype of Menefeeceratops sealeyi was collected
under a permit issued by the U.S. Bureau of Land Manage-
ment to the New Mexico Museum of Natural History and
Science, Albuquerque, New Mexico.
S. G. Dalman etal.
1 3
Etymology. The generic epithet includes “Menefee” in ref-
erence to the Menefee Formation in which the type speci-
men was found. The Greek suffix “ceratops” (= horn-face)
denotes membership in Ceratopsidae, which includes the
new species. The specific epithet honors Paul Sealey, who
discovered the type specimen.
Locality and horizon. NMMNH locality 3033, Allison Mem-
ber of the Menefee Formation, Upper Cretaceous (early
Campanian), Sandoval County, New Mexico, USA (Figs.2,
3). The type material of Menefeeceratops sealeyi gen. et sp.
nov. is an associated incomplete skeleton of a single indi-
vidual (NMMNH P-25052) collected over an area of about
13 m2 (Williamson 1997) (Fig.3). The fossil site is within
a greenish-gray mudstone in the upper part of the Alli-
son Member, ~ 26m below the contact with the overlying
upper coal member (unnamed) of the Menefee Formation
(Fig.2). In addition to NMMNH P-25052, an isolated Tri-
onychidae turtle costal (NMMNH P-25053) and fragments
of fossilized wood were also collected in the same quarry
Fig. 3 Quarry map of NMMNH
locality L-3033, Menefee
Formation (Allison Member), in
Sandoval County, New Mexico,
showing distribution of the
holotype of Menefeeceratops
sealeyi (NMMNH P-25052)
with an isolated trionychid
costal (NMMNH P-25053) and
fossil wood fragments (modified
from Williamson, 1997)
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
(Fig.3). The overlying Cliff House Sandstone is given an
age of 81–80Ma based on the zone of Baculites obtusus
(Obradovich 1993; Ogg and Hinnov 2012), which makes
the Allison Member of the Menefee Formation older, here
conservatively assigned 82–81Ma, but may be as old as
83.5Ma based on biostratigraphy (Lewis etal. 2008). See
“Geologic Setting” above for further discussion.
Diagnosis. NMMNH P-25052 is a centrosaurine ceratopsid
with the following autapomorphies: (1) the lateral margin of
the parietal lacks epiparietal loci (a condition shared with
Machairoceratops); (2) three external squamosal protuber-
ances; (3) the lateral (dorsolateral) surface of the squamosal
has three ridges that are rostroventrally oriented on the bone
and deviate from each other (the secondary and tertiary
ridges are both relatively inconspicuous); (4) the main dor-
solateral ridge of the squamosal curves from the anterome-
dial (= rostromedial) edge to the ventral-most episquamosal
locus (episquamosal locus 3), terminating approximately
4.5cm from it; (5) three elongate and shallow episquamosal
loci; (6) an episquamosal locus 1 with three secondary undu-
lations; (7) two subequal embayments on the posterior mar-
gin of the squamosal with the more mediodorsal embayment
(between episquamosal loci S1 and S2) distinctly larger than
the more lateroventral embayment (between episquamosal
loci S2 and S3); (8) the posterior portion of squamosal is
longer than the anterior portion (defined by sutures for con-
tact between the squamosal and the quadrate and exoccipi-
tal); (9) a shallow, but distinct, groove located on the medial
surface of the squamosal follows along the ventrolateral and
ventroposterior margins of the squamosal; (10) although the
distance between the ridge and the margins is not uniform,
this ridge separates a convex, smooth portion closer to the
margin and a concave, textured portion anterior and dorsal
to the ridge; (11) elongate postorbital horns distally curv-
ing anteriorly; and (12) a dentary with two elongated ridges
(dorsal and ventral) along its lateral surface. The dorsal
ridge is strongly convex and pronounced; whereas the ven-
tral ridge is low and more inconspicuous. The ridges are
separated from each other by a shallow elongated fossa. In
the anterior region, the fossa deviates dorsally and ventrally
forming a distinct triangle.
ZooBank LSID. urn:lsid:zoobank.
org:act:18F6F8B0-3DF1-491A-B1F1-279C8D964A6C.
Description. Williamson (1997) described some of the
material of NMMNH P-25052, including the fragmentary
left postorbital, fragmentary left jugal, the nearly complete
left and fragmentary right squamosals, the predentary, the
nearly complete left dentary, the cervical vertebrae, several
dorsal vertebrae, the incomplete sacrum, several ribs, the
highly fragmentary ilium, and the left femur. Other material
either prepared, or more fully prepared, after his study, are
included in the present study, along with new and fuller
descriptions of material first mentioned in his study.
Premaxilla—An incomplete isolated, highly fragmentary
left premaxilla is preserved (Fig.4). The premaxilla was not
available to Williamson (1997), having been prepared dur-
ing recent study. Portions of the premaxilla are preserved,
although the margins appear to all be broken and incom-
plete. The premaxilla is missing the caudoventral process
that would contact the maxilla and nasal. In addition, as the
premaxilla is incomplete it also does not preserve the cau-
dodorsal portion that would preserve the diagnostic centro-
saurine ventral angle (Sampson etal. 2013). There is a slight
projection on the medial surface at the anterior portion of the
ridge that slightly folds over anterodorsally. This also marks
the contact groove for the ascending and posterior processes
of the rostrum on the anterior and anteromedial surfaces.
The lateral surface of the premaxilla preserves the margin of
the ectonaris as a shallow circular concavity. While incom-
plete in NMMNH P-25052, this still suggests it was less
rounded in Menefeeceratops sealeyi than in Nasutoceratops
titusi (see Lund 2010; Lund etal. 2016b). The medial sur-
face has several low elongate ridges along the medial surface
which represent part of the transition between the endonaris
and ectonaris, with the ridges inferred to be for articulation
between the contralateral premaxillae.
Postorbital—An incomplete right supraorbital horncore is
preserved in two parts, including portions of the horn and
the body of the postorbital (Fig.5a, b). The dorsal surface
of the right postorbital is gently convex and inclined anteri-
orly. The lateral surface of the postorbital is slightly convex,
whereas the medial surface is slightly concave. The cross-
section and morphology of the outer surface of the base
suggests the orientation of the supraorbital horncore and the
resulting anterior inclination distally. Several small vascular
grooves are present on the dorsal surface. The postorbital
contact with the frontal extends from the medial base of the
supraorbital horncore and curves medially and caudally in
an overlapping contact.
The supraorbital horncore is incomplete and, as for the
premaxilla described above, was not available to Williamson
(1997) for diagnosis. As the supraorbital horncore is incom-
plete, in particular distally, the full length of this element is
uncertain. Most of the medial surface is broken; although
the slight concavity of the medial surface suggests portions
of the cornual sinus (= supracranial sinus) present within
the horncores of at least some ceratopsids (e.g., Farke 2006;
Brown 2018) is preserved in the right supraorbital horn-
core. An offset swelling located at the broken portion of the
supraorbital horncore most likely represents the basal con-
tact for the keratinous sheath that would have covered it in
S. G. Dalman etal.
1 3
life. The supraorbital horncore has numerous longitudinally
oriented grooves and this texture suggests it is from an adult
or sub-adult individual, as the surface in juveniles tends to
be smooth or finely pitted (e.g., Sampson etal. 1997; Ryan
etal. 2001; Mallon etal. 2015). The postorbital horncore
gently curves ventrorostrally (= ventroanteriorly) toward
its distal end and cross-sectionally, it is sub-round with the
lateral surface slightly rounded and the medial surface rela-
tively flatter.
Williamson (1997) described a bone fragment he identi-
fied as the skull roof including parts of the frontal (Fig.5c,
d). However, the bone fragment does not preserve the fron-
tal, which would thus preserve dorsal portions of the brain-
case and/or dorsal regions of the orbit (e.g., Jasinski 2015).
It is identified here as the proximal end (or base) of the left
supraorbital horncore that includes a portion of the body
of the left postorbital and a dorsal portion of the orbit. The
preserved portion of the postorbital terminates at the base of
the supraorbital horncore, which is not preserved with this
fragment. The left postorbital is rounded and dorsolaterally
rugose. The lateral surface is flat. Several small vascular
grooves are present on the dorsal surface of the bone.
Parietal—The parietal material, similar to the premaxilla
and supraorbital horncore material discussed above, was
not prepared until after the study of Williamson (1997), and
therefore, has been previously undescribed. It is a highly
fragmentary portion from the right side of the parietal
(Fig.6). While the preserved parts of the parietal are highly
fractured, portions, specifically those on the dorsal surface,
show at least some of the long-grained texture that is indic-
ative of the frills of more mature ceratopsids (e.g., Ryan
1992; Brown etal. 2009). Based on the preserved morphol-
ogy, the posterior margin of the parietal is inferred to have
formed a semicircular outline in dorsal view that lacked the
median embayment. The parietal fragment is flat. Due to the
Fig. 4 Left premaxilla of Menefeeceratops sealeyi gen. et sp. nov., NMMNH P-25052. Incomplete left premaxilla in a lateral and b medial
views; with c line drawing of the skull showing the position of the incomplete premaxilla in white
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
incompleteness of the parietal, it is difficult to determine if
the parietal was fenestrated, although the medial edge of the
fragment is slightly thicker than the lateral edge.
A small portion of the right posterolateral edge of the
parietal is preserved, with no epiparietal loci present, as the
preserved natural edge is smooth. The natural posterolateral
Fig. 5 Postorbital, including supraorbital horncore, of Menefeeceratops sealeyi gen. et sp. nov., NMMNH P-25052. Right postorbital (with
supraorbital horncore) in a lateral and b medial views. Left postorbital in c lateral and d medial views
S. G. Dalman etal.
1 3
edge is also thinner than the rest of the parietal fragment,
which is relatively thicker and more robust both anteriorly
and medially. If the parietal did, in fact, lack epiparietals
on the lateral margin, Menefeeceratops would share this
characteristic with one other known centrosaurine (Machai-
roceratops). The posterior end of the parietal fragment is
also incomplete, making it difficult to determine if the more
complete parietal contained epiparietal loci or not, specifi-
cally posterodorsally.
Squamosal—Two squamosals, a nearly complete left squa-
mosal and a small fragment of the right (Figs.7, 8, 9, 10),
are preserved. The overall length of the left squamosal is
38.5cm from the distal end of the parietal-squamosal con-
tact to the anterior corner of the free blade posterior to the
Fig. 6 Right parietal of Menefeeceratops sealeyi gen. et sp. nov.,
NMMNH P-25052. Right parietal fragment in a dorsal and b ventral
views; c posterolateral view of the natural edge or margin of the pari-
etal fragment labeled in a and b (dorsal side to the right); d line draw-
ing showing the position of the parietal fragment
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
jugal notch, whereas the maximum width is 26cm. The
width-to-length ratio is 0.68. The right squamosal preserves
a small portion of the posterior blade, with a nearly complete
quadratojugal contact. The left squamosal has the diagnostic
“stepped” squamosal-parietal contact, a feature characteris-
tic of all centrosaurines (Ryan 2007).
The squamosal is a flattened, triangular blade with a thin
posteroventral edge. It is approximately 35cm along its
outer posterior margin, which is well preserved with three
episquamosal loci (Figs.7, 8a, 10a). These episquamosal
loci are poorly preserved, elongate, shallow, and relatively
indistinct with arc lengths of approximately 9cm, 9cm, and
7.5cm for episquamosal loci 1, 2, and 3, respectively. These
episquamosal loci are all convexities along the posterior free
margin (or outer rim) that are effectively separated by two
concave embayments. The embayment between episqua-
mosal loci 1 and 2 is distinctly longer (about 5.5cm) than
that between episquamosal loci 2 and 3 (about 2.3cm). Dif-
ferent size embayments on the squamosal have also been
found in Coronosaurus brinkmani and Centrosaurus aper-
tus, although the difference in these taxa is minor compared
to Menefeeceratops sealeyi. Episquamosal locus 1 has three
small but distinct secondary undulations. These secondary
undulations are not inferred as episquamosal loci due to the
distinct nature of their morphology versus that on the other
two, more ventral, episquamosal loci. It is more likely that
they represent one episquamosal locus with secondary undu-
lations (for a total of three episquamosal loci) rather than
three small dorsal loci with two larger ventral loci (for a
total of five episquamosal loci) based on the episquamosal
morphology commonly seen in other ceratopsids. These
secondary undulations are compact and rugose with obtuse
triangular shapes. The elongate, shallow, and well-separated
episquamosal loci suggest the episquamosals would have
also been relatively discrete.
The anterolateral surface of the squamosal is convex and
marked by numerous vascular grooves. The medial side of
the squamosal preserves the contact for the parietal posteri-
orly, with a marked step distal to the contact for the paroc-
cipital process, as it is in other centrosaurines. An elongate
dorsal groove of the squamosal lies close to and sub-paral-
lels the parietal contact. The groove is straight and nearly
10cm long.
The dorsal surface of the squamosal has a distinct, well-
developed dorsolateral ridge that extends throughout most
of its length, here considered the primary dorsolateral ridge
(Figs.7, 8c, d, 9a). The ridge is pronounced at its anterior
end. As the ridge extends posteriorly, it slopes laterally and
nearly parallels the lateral margin of the squamosal. The
ridge then terminates approximately 4.5cm from episqua-
mosal locus S3. The ridge has gentle, sloping sides. At the
mid-length of the ridge, two other less distinct ridges deviate
from the primary ridge (Figs.7, 8c, d, 9b, c). These other
two ridges are offset from each other and not inferred to be
one continuous, bisected, ridge. The second ridge extends
posterodorsally (= caudodorsally) from midway through the
primary ridge and is directed toward episquamosal locus
S1 (Figs.7, 8c, d, 9c). This second ridge gives the dorsal
surface a general convexity. This ridge has a gently raised
portion approximately 6cm from the main ridge. A second-
ary dorsolateral ridge is also present in most other centrosau-
rine species to at least a degree and is more well developed
in Wendiceratops pinhornensis (see Evans and Ryan 2015,
Fig.7a). However, the orientation is slightly different with
this ridge in W. pinhornensis, in which it creates a sharper
angle nearer episquamosal locus S1. A third ridge is short,
deviating anterolaterally from midway along the main ridge
(Figs.7, 8c, d, 9b). This ridge is much lower and arches
nearly 3cm dorsal to the ventral margin of the squamosal.
However, the ridge is more pronounced at the point where it
deviates from the primary ridge and is less pronounced and
low at the anterior end. Anteriorly, the primary ridge and the
third ridge are separated by a shallow triangular depression.
A similar, but smaller, depression is located directly ventral
to the third smaller ridge and dorsal to the lateral margin
of the squamosal. This tertiary ridge has not been noted in
other centrosaurines.
The larger, primary dorsolateral ridge in Menefeecera-
tops sealeyi is formed by the coalescence of three rugose,
lateral, external squamosal protuberances. These protuber-
ances are similar to those present in Avaceratops, although
not as prominent. Indeed, these protuberances are also pre-
sent, to some degree, in Crittendenceratops krzyzanowskii,
Yehuecauceratops mudei, Nasutoceratops titusi, Wendicera-
tops pinhornensis, Coronosaurus brinkmani, Centrosaurus
apertus, Styracosaurus albertensis, and Albertaceratops
nesmoi, in addition to Avaceratops lammersi, with only
Wendiceratops pinhornensis and Albertaceratops nesmoi
also possessing three external squamosal protuberances. The
posterior-most protuberance is small, but the most prominent
and distinct of these three structures. The tertiary dorsolat-
eral squamosal ridge, which is asmaller and less prominent
ridge than the other two, is formed by the coalescence of
at least four small, rugose bumps (Figs.7, 8c, d, 9b). The
postquadrate embayment (otic notch) is elongate and broad
and lies anterior to a sharp caudolateral angle facing epis-
quamosal locus S3.
The dorsolateral surface of the squamosal contains three
distinct neurovascular foramina. The two anterior foramina
form a line parallel to the anterior edge of the squamosal and
are approximately 5cm apart. The dorsally oriented fora-
men lies on the long axis of the primary dorsolateral ridge,
whereas the other is directly ventral to the smaller ridge.
The third foramen is located where the primary dorsolateral
ridge terminates.
S. G. Dalman etal.
1 3
Fig. 7 Left and right squamosals of Menefeeceratops sealeyi gen. et sp. nov., NMMNH P-25052. Left squamosal in a lateral and b medial views.
Right squamosal fragment in c lateral and d medial views
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
Fig. 8 Left squamosal of Menefeeceratops sealeyi gen. et sp. nov.,
NMMNH P-25052. Left squamosal in a lateral view and b close-up
of the episquamosal loci and posterolateral margin in lateral view.
Highlighting the dorsolateral ridges and external protuberances
of Menefeeceratops, c highlighting the dorsolateral ridges (boxed
in) and protuberances of Menefeeceratops, with the dorsal groove
marked by a dashed line; d illustrated drawing with ridges (lines
marking the ridge crest) and protuberances
S. G. Dalman etal.
1 3
The medial surface of the squamosal is divided by two
vertical ridges that parallel each other and define two
grooves (or sulci), one for the contact with the exoccipi-
tal and the other for contact with the quadrate. The ridges
divide the squamosal into anterior and posterior portions.
The contact for the quadrate is relatively short and is ante-
rior to a shallow, ovoid depression. In contrast, the contact
for the exoccipital is posterior to the quadrate articulation
and is distinctly elongate dorsoventrally and wider than that
for the quadrate. Directly posterior to the exoccipital and
quadrate contacts are two distinct muscle scars, which are
striated and have raised rugose surfaces (Fig.10b). However,
the medial muscle scar posterior to the exoccipital contact
is not raised to the same extent as the lateral one. Directly
between the posterior margin of the exoccipital contact and
the muscle scar is an elongate, shallow fossa. This fossa
extends dorsoventrally and parallels the posterior margin of
the exoccipital contact. The length of the fossa is 4cm, with
an anteroposterior width of 0.8cm. The surface of the fossa
is striated, and likely represents a muscle scar. These muscle
scars probably correspond to the m. depressor mandibulae
for opening the jaws during feeding (e.g., Holliday 2009;
Nabavizadeh 2020a, b) and are more prominent than those
of other centrosaurines.
Similarly, between the posterior margin of the exoccipi-
tal contact and the muscle scar, the bone surface exhibits
numerous elongate grooves and ridges that vary in length
between 2 and 5cm. The longest groove lies closer to the
posterior margin of the exoccipital contact and extends down
to the quadratojugal process of the squamosal. Further, the
muscle scar posterior to the exoccipital contact has a char-
acteristically wide, elongate groove that extends anteropos-
teriorly through the muscle scar. This elongate groove is
approximately 2cm long, with a width of 0.8cm at the
anterior end, tapering to 0.4cm at the posterior end. The
groove lies on a concave surface and is deeper anteriorly
than posteriorly. At the anterodorsal margin of the groove
and perpendicular to it are two smaller grooves that are
in close proximity to each other. Both grooves have equal
lengths (1.2cm) and widths (0.3cm). Directly ventral to the
grooves is another groove that is approximately 1.5cm long
and 0.3cm wide. This smaller groove parallels the larger
ones. There is a concavity anterior to the exoccipital sutural
contact that is relatively thick at 2.3cm. These grooves all
combine to create a generally rugose area between the more
Fig. 9 Left squamosal of Menefeeceratops sealeyi gen. et sp. nov.,
NMMNH P-25052. Highlighting the various ridges on the lateral sur-
face of the squamosal. Left squamosal in a lateral view highlighting
(with dashed line) the primary dorsolateral ridge; in b anterolateral
view highlighting (with dashed line) the tertiary dorsolateral ridge; in
c ventral view highlighting (with dashed line) the secondary dorsolat-
eral ridge. Upper scale bar is for a and b, lower scale bar is for c
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
Fig. 10 Left squamosal of
Menefeeceratops sealeyi gen.
et sp. nov., NMMNH P-25052.
Left squamosal in medial view
highlighting the ventral groove
(dashed line) and lateral ridge
in a medial view; b illus-
trated drawing of medial view
displaying ventral groove and
separating anterior and posterior
portions; and c ventral view
(lateral to top of page, posterior
to the right)
S. G. Dalman etal.
1 3
distinct raised muscle scars (labeled as rugose surfaces in
Fig.10b) and the exoccipital contact region, and this rugose
area may also contribute to the attachment area for the m.
depressor mandibulae.
Ventral to the muscle scar and posterior to the exoccipital
contact is a small, shallow fossa that is approximately 3cm
long and 1cm wide. This fossa is dorsal to the ventral mar-
gin of the squamosal and directly perpendicular to it such
that it follows the contour of the margin. The surface of this
fossa is striated and likely represents a muscle scar.
Directly posterior to the quadratojugal contact, the lat-
eral margin of the squamosal has a low ridge that is nearly
3cm long (Fig.10a, c). The ridge emerges from the base
of the quadratojugal contact and extends caudoventrally as
it tapers into the bone. The bone is smooth ventral to this
ridge in the postquadrate embayment (otic notch). Directly
posterior to the ridge the bone has a smooth convex surface.
An elongated low posteromedial groove is located between
the concave medial surface and the posterolateral margin
of the squamosal and originates approximately 3.5cm pos-
terior to the quadratojugal contact (Figs.7b, 10a, b). The
groove extends posteriorly toward the episquamosal margin.
At the level of episquamosal locus S3, the ridge begins to
curve gently, continues to ascend dorsally, and terminates
near episquamosal locus S1. The distance of the groove from
the episquamosal margin is not uniform. The groove lies
closer to the episquamosal margin at the mid-height of the
bone and farthest from it as it begins to curve at the level of
episquamosal locus S3. The surface texture nearer the ven-
tral and posterior margin to this ridge is smooth while the
concave surface nearer the anterior and medial portions of
the squamosal (proximal) possesses a distinct surface textur-
ing. Surface texture transitions are present in other animals,
such as the transition from the body cavity to the keratinized
scutes of turtle shells, potentially suggesting a similar tran-
sition on the squamosal of this animal, with the proximal
portion covered by flesh and the distal portion keratinized,
ossified, or having a different external covering. In addition,
since the medial portion of the ventral surface is distinctly
concave with a groove separating it from the margin, it is
possible this is a resorption feature, which would suggest
an older ontogenetic stage. Different portions of the same
element exhibiting both smooth and rugose regions are
indicative of resorption and suggestive of ontogenetically
older (i.e., more mature) individuals (e.g., Brown etal. 2009;
Scannella and Horner 2010; Tumarkin-Deratzian 2010).
The posterior portion of the squamosal is distinctlylonger
than the anterior portion, with a ratio of approximately 5:1.
This ratio is quite distinct from those of othercentrosaurines,
which are often closer to 3:2. Both the anterior and poste-
rior portions of the squamosal are slightly concave on the
medial surface. Posterior to the contact surface of the exoc-
cipital and the quadrate and the muscle scars, the surface of
the squamosal is slightly concave and smooth. This surface
becomes more convex distally at the episquamosal margin
beyond the ventral groove near the posterior (or caudal)
margin. This concave portion, making up most of the mid-
dle portion of the ventral surface, may be a resorption fea-
ture. The jugal notch is wide; however, the jugal process is
incomplete.
Jugal—A fragment of the left jugal is preserved (Fig.11),
namely the jugal flange. The jugal flange is plate-like and
slightly convex, in dorsal aspect. Dorsoventrally, the jugal
fragment is 17cm long and anteroposteriorly, at the mid-
length, is 8cm wide. It preserves the contact surface for
the epijugal (albeit not well preserved), but is missing the
ventral margin of the orbit, most of the maxillary process,
and the contact surfaces for the postorbital and squamosal.
The anterior margin of the jugal is marked by a convex ridge,
whereas the ventral margin is V-shaped. Directly adjacent to
this ridge is a shallow fossa which parallels the ridge. The
contact surface for the epijugal is located on the caudola-
teral side of the V-shaped margin and consists of numerous
densely packed grooves and ridges, although the surface is
poorly preserved. The dorsal surface of the jugal is convex
and smooth, and several dorsoventrally oriented vascular
grooves are clearly distinguishable, while the ventral surface
of the bone is slightly concave and smooth. Although bro-
ken, the caudoventral corner of the bone preserves the ovoid
contact surface for the quadratojugal that is mediolaterally
4.5cm thick and anteroposteriorly 3cm wide. It contains
four distinct, low grooves and ridges that parallel each other.
The lateral surface of the bone adjacent to the quadratojugal
contact is strongly convex.
The ventral surface of the jugal flange consists of numer-
ous densely packed, elongated ridges which are most distinct
in the anteroventral region. The ridges parallel each other
with a dorsoventral orientation; however, they do not extend
to the ventral margin of the jugal. At the mid-dorsoventral
length the ridges are interrupted by a single sinuous ridge
marking the anterior margin of the quadratojugal facet. The
surface near the quadratojugal contact is roughened with
randomly oriented short, but thick, ridges. The ridges are
most pronounced near the ventral margin of the quadratoju-
gal contact region.
Predentary—The predentary is preserved and broken into
two halves along its ventral apex (Figs.12, 13, 14). The left
portion of the predentary is more complete than the right,
which is missing the posterior end. The maximum length
of the complete left portion is 17cm; dorsoventral depth in
the posterior region is 11.2cm. The anteriormost tip is not
preserved. The lateral surface of the better-preserved left
portion has numerous vascular grooves. One distinct elon-
gated groove parallels the cutting edge of the predentary and
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
Fig. 11 Left jugal of Menefeeceratops sealeyi gen. et sp. nov., NMMNH P-25052. Incomplete left jugal in a lateral and b medial views; c place-
ment of the left jugal flange in a generalized line drawing of a skull in left lateral view. Upper scale bar is for a and b, lower scale bar is for c
S. G. Dalman etal.
1 3
located within it are three closely spaced foramina for vascu-
lature, including those for the mental artery and nerve (see
Nabavizadeh and Weishampel 2016, for discussion of foram-
ina of the predentary and their affinities). A single mental
foramen is located anteroventral to this elongate groove. The
triturating surface is rugose and terminates dorsolaterally
at a sharp edge, with the lateral edge canted dorsally com-
pared to the medial edge (or inclined steeply laterally), a
feature noted for centrosaurines by Dodson etal. (2004).
The dorsolateral cutting edge is inclined (higher than the
medial edge) and concave along the anteroposterior length.
The dorsal process of the predentary is short, whereas the
ventral process is elongate and longer than the abbreviated
dorsal process. These processes contact concave surfaces on
the anterior portion of the dentary. A cleft on the posterior
surface of the predentary accepts the dentary (see Fig.12f).
Dentary—A nearly complete left dentary is preserved
(Figs.13, 14). The maximum length of the dentary is
36.5cm, although the posterior portion is not preserved. In
lateral view, the dentary is rectangular to sub-rectangular.
The tooth row is slightly damaged in the posterior region,
where a small portion is missing, but has an overall pre-
served length of 29cm. It terminates posterior to the apex of
the coronoid process and preserves 21 alveoli with partially
preserved teeth, although a few more alveoli may have been
present if the element was complete. The edentulous anterior
end of the dentary is linguoventrally flat and slightly concave
Fig. 12 Predentary of Menefeeceratops sealeyi gen. et sp. nov.,
NMMNH P-25052. Left predentary in a lateral and b medial (= lin-
gual) views. Right predentary in c lateral and d medial (= lingual)
views. Associated left and right halves of the predentary in e dorsal
and f posterior views. Left dentary, focusing on the triturating surface
in g medial (= lingual) and h occlusal (= dorsal) views; i close-up of
triturating surface in occlusal (dorsal) view (boxed area in h high-
lighting rugose surface)
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
anteriorly, specifically anterolaterally. The concave surface
of the edentulous anterior end represents the contact sur-
face for the caudodorsal process of the predentary (= dorsal
process of the predentary). A short and slightly depressed
facet is anteroventrally oriented on the anteroventral por-
tion of the lateral surface of the dentary and overlaps the
ventral process of the predentary. The lateral surface of the
dentary is smooth. There are two elongate ridges on the lat-
eral surface: dorsal and ventral, that cover approximately the
anterior two-thirds of the element. Several other ceratopsids
have a single ridge present on the lateral surface of the den-
tary (e.g., Dodson etal. 2004), including Albertaceratops
nesmoi, Kosmoceratops richardsoni, Spiclypeus shipporum,
Utahceratops gettyi, and Wendiceratops pinhornensis. The
dorsal ridge is strongly convex and prominent; whereas
the ventral ridge is low and less pronounced. The ridges
are separated by a shallow elongate fossa. In the anterior
region the ridges deviate dorsally and ventrally resulting in
the fossa being distinctly triangular. The ventral margin of
the dentary is slightly rugose and weakly convex in lateral
view. The coronoid process, located in the posterior region
of the dentary, is robust, short, and vertically oriented. It
emerges from the lateral surface of the dentary and projects
vertically 12.5cm above the medially inset tooth row. The
Fig. 13 Dentary of Menefeeceratops sealeyi gen. et sp. nov., NMMNH P-25052. Left dentary in a and b lateral; c and d medial (= lingual)
views; e posterior; f dorsal; and g ventral views; h dentary tooth. 10-cm scale bar applies to ag, 1-cm scale bar applies to h
S. G. Dalman etal.
1 3
anteroposterior length at the base of the coronoid process is
11.5cm. Dorsally, the coronoid process narrows, with the
apex flat and mediolaterally thin. The posterior expansion
of the coronoid process is convex and the surface where
the external adductor musculature was attached in life is
rugose (Mallon and Anderson 2015). The anterior surface
of the coronoid process has a prominent fossa separating
the anterolateral margin from the anteromedial margin. This
fossa, the anterior fossa of the coronoid process (= man-
dibular fossa), is present in other ceratopsids. A similar
fossa extends dorsoventrally along the posterior surface
of the coronoid process. The anterior fossa is best seen in
anteromedial aspect and the posterior fossa is best seen in
caudomedial aspect. On the medial surface of the coronoid
process are two elongate ridges adjacent to their respective
fossae: an anteromedial ridge and a posteromedial ridge.
The anterior ridge is concave anteriorly, whereas the poste-
rior ridge is concave posteriorly in medial view, giving the
medial surface of the coronoid process a subtle but charac-
teristic “X”-shape. Ventromedially, a shallow adductor fossa
opens between the coronoid process and the posterior end
of the tooth row. The fossa does not reach all the way to
the ventromedially exposed Meckelian groove, which pro-
gressively shallows anteriorly and terminates at the level
of alveolus 3. Directly dorsal to the Meckelian groove is
a pronounced lingual lamina that is anteriorly flared. The
flaring of the lingual lamina originates at the level of alveo-
lus 13. The bone surface of the lingual lamina is concave
and smooth. The dorsal surface of the lingual lamina that
underlines the tooth row is gently concave. As the posterior
border of the dentary is poorly preserved, little can be said
of its contacts with the surangular and angular. In addition,
Fig. 14 Articulated left mandibular elements of Menefeeceratops sea-
leyi gen. et sp. nov., NMMNH P-25052. Articulated left predentary
and dentary in a lateral and b medial (= lingual) views. Predentary
has been rearticulated based on the corresponding morphology of the
predentary and dentary
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
as the outer surface is highly fractured, the sutural contacts
of the coronoid bone are not visible.
Cervical vertebra—Two coalesced vertebral centra repre-
senting cervical vertebrae ?5–?6 are preserved in NMMNH
P-25052 (Fig.15a) and were first described by Williamson
(1997). The centra are deformed and laterally flattened,
missing the neural arches and accessory processes. The
rounded ends (cotyle and condyle) of the centra suggest
they are cervical vertebrae (see e.g., Holmes etal. 2005;
Holmes and Ryan 2013; Holmes 2014). The syncervical of
ceratopsids is often made up of the fusion of the first three
(or four) cervical vertebrae (see Ostrom and Wellnhofer
1986; Lehman 1989; Dodson 1996; Penkalski and Dodson
1999; Dodson etal. 2004; Campione and Holmes 2006;
Holmes 2014; equals the cervical bar of Langston 1975).
Although Williamson (1997: 56) described this element as
“two coalesced cervical vertebrae,” there is no evidence of
a dividing synostosis. However, the element is quite elon-
gate (anteroposteriorly approximately 11.25cm long), sug-
gesting it is made up of multiple cervical centra. This is
similar in size to the combined lengths (12.8cm) of cervical
vertebrae 5 (6.6cm) and 6 (6.2cm) of a specimen of Sty-
racosaurus albertensis (CMN 344, holotype, see Holmes
etal. 2005) and the coalesced cervical vertebrae 5 and 6
(12.7cm) of a specimen of Centrosaurus apertus (YPM
2015, originally identified “Centrosaurus flexus”, see Lull,
1933, later synonymized with C. apertus). We agree with
Williamson (1997) that there is no evidence of sutures on the
ends of the centra, suggesting it is not part of the syncervi-
cal. Williamson did mention its similarities with the coa-
lesced ?fifth–?sixth cervical vertebrae in YPM 2015 (“Cen-
trosaurus flexus”). Lull (1933: 40–41, Fig.8) described and
identified these vertebrae as pathologic. Indeed, pathologies
in the vertebrae of ceratopsids have been reported numer-
ous times in the literature (e.g., Erickson and Olson 1996;
Fowler and Sullivan 2006; Tanke and Rothschild 2010; Sul-
livan etal. 2011c; Canoy Illies and Fowler 2020), including,
but not limited to, bite marks from theropod dinosaurs (e.g.,
Erickson and Olson 1996; Chure etal. 1998; Jacobsen 1998;
Fowler and Sullivan 2006; Robinson etal. 2015). We accept
Williamson’s (1997) identification that these two coalesced
cervical vertebrae (?fifth–?sixth cervical vertebrae) are
likely pathologic, obscuring other features.
Dorsal vertebrae—Williamson (1997) mentioned at least
six dorsal vertebrae; we recognize seven, all of which are
distorted, and most are missing the majority of their acces-
sory processes (Fig.14b–h). Additional vertebral fragments
may represent portions of other vertebrae. The centra have
the distinctive ceratopsian “pear-shape” (e.g., Dodson etal.
2004; Holmes etal. 2005). The pronounced deformation of
the vertebrae prevents most meaningful measurements of
height, width, and length and determination of the original
orientation of the transverse processes and neural spines.
The centra are axially shortened. Of the more complete
vertebrae, major portions of dorsal vertebrae ?6 through 12
are identified. Dorsal vertebra ?6 consists of a centrum and
separate neural spine (Fig.15b). It measures approximately
6.6cm long, with a centrum height of around 9cm, but
it has undergone significant lateral deformation, making
measurements of the centrum faces untrustworthy. Most of
the features, including all accessory processes, are missing,
although the anteroposterior length of the neural spine is
short, suggesting it is either anterior or posterior in the dor-
sal vertebral series rather than a mid-dorsal vertebra. Dorsal
vertebra 7 is better preserved than dorsal vertebra ?6 but
taphonomically deformed and is missing most of its pro-
cesses, including its neural spine (Fig.15c). The centrum is
approximately 4cm long, with the anterior surface (cotyle)
around 9.9cm tall by 7.8cm wide, while the centrum and
neural arch are 22cm high (to the base of the neural spine).
Dorsal vertebra 8 is also slightly taphonomically deformed,
with portions of the processes still preserved. Similar to
the preceding vertebra, the centrum is oval with a length
of approximately 5.7cm, with the cotyle end 9.5cm tall
by 8.2cm wide. Dorsal vertebra 9 is significantly crushed
laterally, although it does preserve the lower portion of the
neural spine (Fig.15e). The centrum is 5.7cm long, with
the anterior surface (cotyle) approximately 12cm tall by
3cm wide, although due to the taphonomic deformation,
the dimensions of the cotyle can only be approximated. The
neural spine projects posterodorsally, and there is a signifi-
cant caudal overhang, with the postzygapophyses extending
beyond the posterior surface of the centrum (condyle). The
prezygapophyseal surface is broken. Only the left transverse
process is preserved, which is significantly angled laterodor-
sally, and the neural canal has been crushed completely shut.
Dorsal vertebra 10 is similar in morphology and preserva-
tion to dorsal vertebra 9 (Fig.15f). The centrum is 7.3cm
long, with the anterior surface (cotyle) approximately 8cm
tall by 3.9cm wide, although the centrum has again been
significantly crushed, making these measurements only
approximate. The neural spine, while missing its dorsal
portion, is angled more posteriorly than that of dorsal ver-
tebra 9, with a longer caudal overhang in dorsal vertebra 10
compared to more anterior vertebrae. The postzygapophyses
extend farther posteriorly in dorsal vertebra 10 compared to
more anterior vertebrae as well. The prezygapophyses are
preserved as well, with both slightly angled laterodorsally.
The proximal portions of the transverse processes are pre-
served, with the preserved portions directed dorsolaterally,
and are more robust than that preserved in dorsal vertebra 9.
In addition, the posterior surface of the neural arch, ventral
to the postzygapophyseal surface, shows a convex curvature,
a gentle posterior projection, that is not present in dorsal
S. G. Dalman etal.
1 3
vertebra 9. A nearly complete dorsal vertebra is question-
ably identified as the 11th (Fig.15g). The centrum of dorsal
vertebra ?11 is incomplete, particularly missing larger por-
tions of the left side. It is 4.6cm long and, although incom-
plete, the anterior surface (cotyle) has preserved dimensions
of 9cm tall by 6.3cm wide. The neural canal is partially
crushed but would have been roughly oval. The neural arch
and incomplete neural spine have been taphonomically
deformed to have a general sigmoidal curvature. The right
transverse process is complete, preserving the diapophysis as
Fig. 15 Elements of the axial skeleton of Menefeeceratops sealeyi
gen. et sp. nov., NMMNH P-25052. Two coalesced Cervical verte-
brae ?5–?6 (a) in a1 anterior; a2 posterior; a3 left lateral; and a4 right
lateral views. Dorsal vertebrae (bh), including dorsal vertebra ?6 in
b1 right lateral; and b2 left anterior oblique views, dorsal vertebra 7
in c1 left anterior oblique; and c2 right posterior oblique views; dor-
sal vertebra 8 in d1 anterior; and d2 posterior views; dorsal vertebra
9 in e1 right lateral; and e2 left lateral views; dorsal vertebra 10 in f1
right lateral; and f2 left lateral views; dorsal vertebra ?11 in g1 ante-
rior; and g2, posterior views; and dorsal vertebra 12 in h1 right lat-
eral; and h2 left lateral views
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
well. Crushing makes measurements of the transverse pro-
cess difficult, but the right diapophysis is 2.9cm by 2.5cm.
Dorsal vertebra 12 is nearly complete, albeit taphonomically
deformed laterally and sheared (Fig.15h). The centrum has
an approximate length of 5.7cm, with the anterior surface
(cotyle) having preserved dimensions of 11.3cm high by
5cm wide. The neural canal is deformed but appears to have
been sub-round. The neural spine is less angled than the
spines of those vertebrae anterior to it. The left transverse
process is poorly preserved, with the diapophysis missing.
An abnormally textured lump on the neural spine may be a
pathology.
Sacrum—Williamson (1997) described a partial sacrum,
which includes the centra of at least four (I–IV), to poten-
tially five, sacral vertebrae (Fig.16). Williamson (1997)
reported six sacral vertebrae, but at least the anteriormost
centrum on the sacrum represents the dorsosacral verte-
bral centrum fused to the rest of the sacral vertebrae. The
fused sacra have a total length of approximately 67cm. The
sacrum is also taphonomically deformed, with the dorsal
portions above the centra shifted and bent toward the right
lateral surface, resulting in the dorsal processes being in a
similar plane to the right lateral side of the centra. The por-
tions of the dorsal spinous processes that are preserved are
fused with a total preserved length of approximately 50cm.
A portion of the parapophysis with the cranial portion of the
acetabular bar is present on the right side. An inconspicuous
medial groove is present ventrally on sacral vertebrae II–III.
This ventral groove is similar in placement and morphology
to those in some other ceratopsids such as Styracosaurus
albertensis and Vagaceratops (“Chasmosaurus”) irvinensis
(e.g., Holmes and Ryan 2013; Holmes 2014).
Ribs—Two incomplete cervical ribs and 11 incomplete tho-
racic ribs and rib fragments are preserved (Fig.17), which
Williamson (1997) also briefly cited. The more complete
of the two preserved cervical ribs is missing the distal end
and the tubercular facet, although the capitulum is preserved
(Fig.17a). The rib is “T”-shaped, with the capitular process
at a right angle to the shaft. It has a preserved proximodistal
length of approximately 22cm.
Two larger ribs have well-developed and pronounced
tubercular facets, indicating that they most likely represent
the anterior dorsal ribs (Fig.17b, c). Some of the dorsal ribs
preserve the capitulum and tuberculum, whereas others pre-
serve only the shaft. All preserved ribs exhibit a form similar
to those of other ceratopsids, with no distinguishing mor-
phology. The tuberculum in the thoracic ribs is somewhat
reduced. The shafts are slightly bent and rounder in cross-
section; however, the capitular processes are not confluent
with the shaft, which indicates that the ribs are likely from
the cranial thoracic region. The characteristic morphology
of the ribs indicates that Menefeeceratops has a narrow chest
with a wider, more barrel-shaped abdomen, which has been
reported for other genera (e.g., Agujaceratops, Lehman
1989; “Brachyceratops”, Gilmore 1917).
Radius—The left radius is only represented by the distal
portion (Fig.18a, b). This element was not cited by Wil-
liamson (1997). The bone is poorly preserved but appears
to be columnar with a rounded distal end that is moder-
ately expanded. The fragment preserves part of the surface
that contacts the ulna. The distal expansion of the radius
also exhibits a long, narrow articular surface for the carpus.
The incompleteness of the bone prohibits a more thorough
description.
Ulna—The left ulna was not mentioned by Williamson
(1997) but is preserved and represented by the proximal
and distal ends (Fig.18c, d). The bone is crushed; but some
morphological features are distinguishable, including the
olecranon process, the anterolateral process of the ulna, the
base of the medial process of the ulna, and the trochlear
notch. Due to the breakage and poor preservation of the
ulna, particularly the proximal end, little can be said of the
morphology. Although the olecranon is incomplete, the base
is distinctly triangular in cross-section. The full extent of
the olecranon is unknown. The craniolateral process of the
ulna is well defined and forms a broadly rounded crest that
extends onto the lateral surface of the olecranon. The medial
process is not well preserved making it difficult to determine
if the proximal articulation for the humerus (trochlear notch)
was deeply or shallowly concave.
Ilium—A badly damaged bone most likely represents the
cranial (= anterior) portion of a left ilium with a partial
pubic peduncle and acetabulum (Fig.19a–c). It was briefly
mentioned but not described Williamson (1997). The speci-
men has undergone significant deformation, including crush-
ing and breakage. If undeformed, the element would have
been blade-like. It has a total preserved length of 56cm,
but is it not possible to determine how long the ilium would
have been when complete. A rugose portion of the bone
that sticks out from the rest is identified as the pubic pedun-
cle, although nothing distinct can be determined about its
morphology.
Femur—A left femur is preserved, but is extremely crushed,
deformed anteroposteriorly, and missing part of its proximal
end (Fig.19d, e). Several anatomical features are clearly
distinguishable, such as the morphology of the head, the
fourth trochanter, the distal condyles, in addition to the
overall shape of the femur (Williamson 1997). The femur is
relatively robust and has a length of 69.6cm. Comparatively,
the left femur of YPM 2015 (holotype of “Centrosaurus
S. G. Dalman etal.
1 3
flexus” [= Centrosaurus apertus]) is 78.9cm long, the left
femur of CMN 344 (holotype of Styracosaurus alberten-
sis) is approximately 86.3cm long, the left femur of TMP
1989.097.001 (identified as a younger or sub-adult Styra-
cosaurus albertensis) is approximately 40.8cm long, the
nearly complete right femur of CMN 41,357 (holotype of
Chasmosaurus” (= Vagaceratops) irvinensis) is 76.0cm
long, and the right femur of ANSP 15800 (holotype of
Avaceratops lammersi) is 38.5cm. Proximally, the maxi-
mum width of NMMNH P-25052 is 19.3cm, with a distal
maximum width of 16.8cm across the condyles. The width
at midshaft is approximately 10.3cm. The femur is gener-
ally oval in cross-section, with flatter anterior and poste-
rior surfaces, although this may have been exacerbated by
Fig. 16 Sacrum of Menefeeceratops sealeyi gen. et sp. nov., NMMNH P-25052. Sacrum in a right dorsolateral (dorsal processes, including
sacral ribs viewed dorsally, while centra viewed laterally to dorsolaterally); and b ventral views
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
Fig. 17 Ribs of Menefeeceratops sealeyi gen. et sp. nov., NMMNH
P-25052. Incomplete cervical rib (a) in a1 anterior and a2 posterior
view; anterior dorsal ribs (b–c) in (b1–c1) anterior; and (b2–c2) pos-
terior view; and incomplete dorsal ribs (d–l) in (d1–l1) anterior; and
(d2–l2) posterior view
S. G. Dalman etal.
1 3
taphonomic deformation. The fourth trochanter maintains
its original shape and size, which is small and reduced to a
low prominence. Rugosity on the surface of the femur near
the fourth trochanter continues proximally for approximately
11–12cm. The fourth trochanter is found laterally, approxi-
mately 31.9cm from the proximal end and 37.7cm from
the distal end, placing it approximately 54% of the way up
the femur (from the distal end). The fourth trochanter is less
elongate compared to that of some other ceratopsids (e.g.,
Avaceratops lammersi, Styracosaurus albertensis, Vagacera-
tops (“Chasmosaurus”) irvinensis; Penkalski and Dodson,
1999; Holmes and Ryan, 2013; Holmes, 2014). The medial
distal condyle is smaller than the lateral distal condyle.
The condyles are separated from each other by a shallow
Fig. 18 Appendicular skeletal
elements of the forelimb of
Menefeeceratops sealeyi gen.
et sp. nov., NMMNH P-25052.
Left radius fragment (a–b) in
a lateral and b medial views.
Left ulna, with proximal and
distal ends preserved (c–d), in c
lateral and d medial views
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
intercondylar fossa. Comparison of the femur with other
ceratopsids, including those of Styracosaurus albertensis,
Vagaceratops (“Chasmosaurus”) irvinensis, and particular
of Centrosaurus apertus where the size estimate is around
5m (see Dodson 1996), provides a size estimate of around
4 to 4.5m long for NMMNH P-25052.
Fibula—The distal end of the left fibula (Fig.19j, k) is well
preserved, triangular in distal view, and was not cited by
Williamson (1997). The distal portion of the element is
wider than the proximal preserved portion. Not enough is
of this element is preserved to provide further details.
Fig. 19 Appendicular skeletal elements of the hindlimb of Men-
efeeceratops sealeyi gen. et sp. nov., NMMNH P-25052. Incomplete
left ilium (ac) in a lateral; b dorsal; and c ventral views. Nearly
complete left femur (de) in d anterior; and e posterior views. Incom-
plete left metatarsal II (fi) in f anterior; g lateral; h posterior; and i
medial views. Left distal fibula (jk) in j lateral; and k medial views.
Upper scale bar for ae, lower scale bar for fk
S. G. Dalman etal.
1 3
Metatarsal—An incomplete left metatarsal II (Fig.19f–i) is
preserved and was not cited by Williamson (1997). The bone
is robust, missing small portions of the proximal and distal
ends. The metatarsal has a preserved proximodistal length
of 15.6cm and a midshaft width of approximately 4.8cm.
The proximal end is expanded dorsoplantarly, with a width
of 6.6cm, whereas the distal end is expanded transversely
with a width of 7.7cm. The medial surface of the proximal
end has a shallow concavity for articulation with metatarsal
I. The lateral side of the metatarsal is slightly convex and
articulates with the concave surface of metatarsal III.
Taxonomic distinctiveness
ofMenefeeceratops sealeyi
The holotype specimen of Menefeeceratops sealeyi
(NMMNH P-25052) is confidently referred to a centrosau-
rine ceratopsid and placed within the Centrosaurinae clade
based on the morphology of the squamosal, which is trian-
gular in outline and has the “stepped” squamosal-parietal
contact characteristic of the Centrosaurinae (Ryan 2007),
and the canted triturating surface of the predentary (Samp-
son and Loewen 2010). While the ventral angle of the cau-
doventral portion of the premaxilla (Sampson etal. 2013)
was probably present, the incompleteness of the preserved
premaxilla of M. sealeyi makes it impossible to confirm this
feature. Menefeeceratops sealeyi is considered a mature,
adult individual due to the rugose, textured nature of the
postorbital horncore and squamosal, along with the potential
fusion of the episquamosals onto the squamosal (discussed
further below). Menefeeceratops sealeyi represents a cen-
trosaurine about 4m long based on comparison of available
elements to other centrosaurines.
Menefeeceratops sealeyi has a relatively ornate squa-
mosal, particularly on the anterolateral surface, but it is
not as extensively ornate as in other centrosaurine spe-
cies such as Centrosaurus apertus, Diabloceratops eatoni,
Machairoceratops cronusi, Styracosaurus albertensis, and
Wendiceratops pinhornensis. In Centrosaurus apertus, the
episquamosals and external squamosal protuberances are
more numerous and/or pronounced than in Menefeecera-
tops sealeyi. In Machairoceratops cronusi and Styracosau-
rus albertensis, the squamosal is more elongate with a much
wider otic notch. While in Wendiceratops pinhornensis, the
posterior squamosal rim, with its episquamosals, is more
ornate than in Menefeeceratops sealeyi. In addition, all
these other centrosaurines tend to have a more distinct and
conspicuous primary dorsolateral ridge of the squamosal,
even if some of them, such as Diabloceratops eatoni and
Machairoceratops cronusi, do not have external squamosal
protuberances as part of that ridge.
Possessing three episquamosal loci is not uncommon
in centrosaurines, although the secondary undulations at
episquamosal locus 1, with three distinct but low second-
ary undulations, in Menefeeceratops sealeyi are not found
in other centrosaurines. In general, known centrosaurine
species have large episquamosals, and their count is two in
Diabloceratops eatoni, the Last Chance species (UMNH VP
16699), and the Nipple Butte species (UMNH VP 16,702);
three in Achelousaurus horneri, Einiosaurus procurvi-
cornis, and Yehuecauhceratops mudei; four in Avaceratops
lammersi, Centrosaurus apertus, Crittendenceratops krzyz-
anowskii, Machairoceratops cronusi, Nasutoceratops titusi,
Pachyrhinosaurus canadensis, and Wendiceratops pin-
hornensis; and five in Styracosaurus albertensis and TMP
1965.23.26 (Oldman Formation near Hilda, Alberta, referred
to “Centrosaurus”). The number of episquamosal loci does
not seem to change in ceratopsids through ontogeny. Instead,
the episquamosals will fuse to the loci through ontogeny
(see Mallon etal. 2015). Fusion of the episquamosals of
Menefeeceratops sealeyi is uncertain, as fully fused epis-
quamosals would suggest the adult condition (Dodson and
Currie 1988), but the rugose nature of the episquamosal loci
suggests the episquamosals may be completely fused to the
squamosal rim. In addition, the mottled to mostly rugose tex-
ture of the squamosal suggests M. sealeyi was adult to nearly
adult (see Brown etal. 2009). It is noted that Brown etal.
(2009) determined surface texture changes through ontog-
eny of centrosaurines using the parietal, but these changes
should continue onto the squamosal as well. However, we
also note that the timing of which surface texture would
change first (on the squamosal versus on the parietal) is not
currently known, and this may also vary interspecifically, or
even intraspecifically.
Other distinct features in the squamosal of Menefeecer-
atops sealeyi that set it apart from other centrosaurines
include three dorsolateral (or lateral) ridges which branch
off from each other. Sampson etal. (2013) suggested that
the dorsolateral squamosal ridge in Nasutoceratops titusi
is an autapomorphy of this genus. However, this ridge can
be found to varying degrees of development on many other
ceratopsid squamosals but is most prominent in basal cen-
trosaurines (Evans and Ryan 2015). Currently, this morpho-
logic feature has been considered a symplesiomorphy of
basal centrosaurines, as the ridge is present in Achelousaurus
horneri, Albertaceratops nesmoi, Avaceratops lammersi, the
Oldman Formation indeterminate species (CMN 8804), Crit-
tendenceratops krzyzanowskii, Einiosaurus procurvicornis,
the Malta centrosaurine (GPDM 63), TMP 1965.23.26 (Old-
man Formation near Hilda), Wendiceratops pinhornensis,
and Yehuecauhceratops mudei (Sampson 1995; Ryan 2007;
Evans and Ryan 2015; Rivera-Sylva etal. 2016, 2017; Dal-
man etal. 2018). Although other known ceratopsians and,
in particular, centrosaurines possess a dorsolateral ridge,
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
the curvature and position of the dorsolateral ridge on the
squamosals differs from that of Menefeeceratops (Figs.20,
21, 22). Rivera-Sylva etal. (2016) suggested that the dorso-
lateral ridge of the squamosal is short in NMMNH P-25052
(Menefeeceratops). However, in M. sealeyi the primary
dorsolateral ridge is elongate, extending across most of the
bone’s length and terminating approximately 4.5cm from
episquamosal locus S3. In Crittendenceratops krzyzanow-
skii, Nasutoceratops titusi, and Yehuecauhceratops mudei
the dorsolateral ridge is pronounced. However, in N. titusi
and Y. mudei the ridge extends throughout most of the length
of the squamosal; whereas in C. krzyzanowskii the ridge
is short (Dalman etal. 2018: fig.15). Interestingly, in C.
krzyzanowskii and Y. mudei most of the posterior portion of
the ridge is directly at the lateral margin of the squamosal,
whereas in N. titusi the ridge is clearly dorsal to the lat-
eral margin of the squamosal; however, it does not closely
resemble the ridge of Avaceratops lammersi (Dalman etal.
2018: fig.15). The primary dorsolateral ridge of the squa-
mosal in A. lammersi follows the squamosal-parietal contact
more closely before angling toward the caudoventral edge of
the squamosal, while that in M. sealeyi almost immediately
deviates from the squamosal-parietal sutural surface (see
Fig.22a, d).
In other ceratopsians (i.e., chasmosaurines), the dorsolat-
eral ridge is present; however, its position on the squamosal
differs from that of centrosaurines and, in particular, from
basal species. In juveniles of Chasmosaurus belli (UALVP
52613) (see Currie etal. 2016: fig.4) and juveniles of Tri-
ceratops horridus (UCMP 154452) (see Goodwin etal.
2006: fig.1), the dorsolateral ridge is situated close to the
squamosal-parietal contact (Fig.20). The ridge in the juve-
niles of both species is formed by the coalescence of several
external squamosal protuberances (= squamosal swellings
of Currie etal. 2016; = dorsal squamosal processes of Dal-
man etal. 2016). The external squamosal protuberances
are absent in adult-sized specimens of Chasmosaurus and
Triceratops (see Forster 1996: fig.7; Campbell etal. 2016:
fig.9). In adult-sized Triceratops and Arrhinoceratops speci-
mens, the dorsolateral squamosal ridge is absent; whereas in
Fig. 20 Squamosal ridges in Triceratops and Chasmosaurus through
ontogeny. Skulls of Triceratops (ab) and Chasmosaurus (cd) in
left lateral view; a reconstructed skull of baby Triceratops (UCMP
154452) with the primary dorsolateral ridge lying close to and nearly
parallel to the squamosal-parietal contact; b skull of Triceratops pror-
sus (YPM 1822, holotype); c skull of juvenile Chasmosaurus belli
(UALVP 52613) showing the primary dorsolateral ridge close to the
squamosal-parietal contact; and d skull of Chasmosaurus belli (ROM
839, holotype of Chasmosaurus brevirostris) showing the primary
dorsolateral ridge
S. G. Dalman etal.
1 3
Chasmosaurus (C. belli, C. russelli) and in closely related
species such as Agujaceratops mariscalensis, Mojoceratops
(“Chasmosaurus”) perifania, Pentaceratops sternbergi,
Spiclypeus shipporum, and Torosaurus latus the dorsolat-
eral squamosal ridge is pronounced and well developed.
In addition to Triceratops and Chasmosaurus, juveniles of
Arrhinoceratops brachyops also possess the primary dor-
solateral ridge (CMN 8882), where it is made up of two
external squamosal protuberances (see Mallon etal. 2015:
fig.5), while in adults such as ROM 796 (holotype) and
ROM 1439 (see Mallon etal. 2014: fig.7), the ridge is also
absent. Furthermore, the dorsolateral squamosal ridge in
centrosaurines and chasmosaurines may not suggest com-
mon ancestry, but instead may be a feature that evolved
independently in both groups, as it does not appear to be
homologous in both groups. However, its presence in some
juvenile chasmosaurines is suggestive of a more ancestral
state. More study with potential common ancestors of these
two subfamilies is needed to determine the ancestral char-
acteristics of these features.
In Menefeeceratops sealeyi, the primary dorsolateral
ridge is formed by the coalescence of three rugose, exter-
nal squamosal protuberances (= dorsal squamosal pro-
cesses, = squamosal swellings) and not by a single one as
suggested by Rivera-Sylva etal. (2016). In contrast, the
squamosals of Crittendenceratops krzyzanowskii, Nasutocer-
atops titusi, and Yehuecauhceratops mudei have a single
pronounced external squamosal protuberance located at the
posterior end of the dorsolateral ridge (Dalman etal. 2018).
The presence of this pronounced process on the dorso-
lateral ridge of the squamosals of Crittendenceratops krzyz-
anowskii, Nasutoceratops titusi, and Yehuecauhceratops
mudei (Dalman etal. 2018: fig.15) is a distinctive feature
(Fig.22); however, a specimen attributed to Centrosaurus
apertus (TMP 1995.401.0007) also possesses a small exter-
nal squamosal protuberance (Dalman etal. 2018: fig.17).
In C. apertus, the external squamosal protuberance is close
to the lateral margin of the squamosal and directly postero-
dorsal to the quadratojugal contact. Avaceratops lammersi
has four external squamosal protuberances that form part
of, or the majority of, the dorsolateral squamosal ridge
(Fig.22d, see also Dalman etal. 2018: fig.15a). Similarly,
four external squamosal protuberances are present in Coron-
osaurus brinkmani and in the isolated right squamosal TMP
1965.23.26 (Fig.21), referred to Centrosaurus by Dalman
etal. (2018: figs.18c, 19a). The isolated fragmentary squa-
mosal of the Oldman Formation indeterminate “nasutocer-
atopsin” (CMN 8804) preserves three external squamosal
protuberances on the dorsolateral squamosal ridge (Dalman
etal. 2018: fig.19b), although if complete there would prob-
ably be more, and if TMP 1965.23.26 represents the same
taxon, then both would have four (Fig.21). The overall mor-
phology and the position of the dorsolateral squamosal ridge
and the protuberances in CMN 8804 closely resemble that
of TMP 1965.23.26 (Dalman etal. 2018: fig.19a). Further-
more, based on overall morphology, TMP 1965.23.26 more
closely resembles a “nasutoceratopsin” than Centrosaurus
(Dalman etal. 2018). Indeed, it is noted here that, although
Fig. 21 Centrosaurine squamosals from the Oldman Formation in
right dorsal view; aCentrosaurus” (TMP 1965.23.26); b indetermi-
nate Oldman Formation centrosaurine CMN 8804. These squamosals
potentially represent the same taxon, with Ryan etal. (2016) referring
CMN 8804 to an indeterminate “nasutoceratopsin”
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
Fig. 22 Squamosals of Centrosaurinae. Left squamosals of various
members of the Centrosaurinae highlighting the dorsolateral squa-
mosal ridges and external squamosal protuberances (= dorsal squa-
mosal processes or squamosal swellings) in lateral view. Right squa-
mosals have been reversed, lines are dorsolateral squamosal ridges
and circles signify external squamosal protuberances. Grey areas
represent missing material: a Menefeeceratops sealeyi (NMMNH
P-25052, holotype); b Crittendenceratops krzyzanowskii (NMMNH
P-34906, holotype); c Yehuecauhceratops mudei (CPC 274, holo-
type); d Avaceratops lammersi (ANSP 15800, holotype); e Nasu-
toceratops titusi (UMNH VP 16800); f Wendiceratops pinhornensis
(TMP 2011.051.0001); g Einiosaurus procurvicornis (MOR 456,
right squamosal reversed); h Achelousaurus horneri (MOR 485);
i Coronosaurus brinkmani (TMP 2002.68.14), right squamosal
reversed); j Centrosaurus apertus (TMP 1995.401.0007); k Styraco-
saurus albertensis (TMP 66.10.34); l Diabloceratops eatoni (UMNH
VP 16699, holotype); m Machairoceratops cronusi (UMNH VP
20550, holotype); n Albertaceratops nesmoi (TMP 2001.26.1, holo-
type)
S. G. Dalman etal.
1 3
the squamosal of CMN 8804 is incomplete, that of TMP
1965.23.26 closely resembles its morphology, and they may
represent the same taxon, particularly as both come from
the Oldman Formation (sensu stricto). In some other cen-
trosaurine genera, such as Achelousaurus horneri and Eini-
osaurus procurvicornis, the dorsolateral squamosal ridge
is weakly developed; whereas in Albertaceratops nesmoi
the ridge is formed by the coalescence of three distinctive,
low external squamosal protuberances (Dalman etal. 2018:
fig.18b). In Coronosaurus brinkmani, there are four external
squamosal protuberances; however, the fourth protuberance
is not a part of the dorsolateral squamosal ridge (Dalman
etal. 2018: fig.18c). Similarly, in Avaceratops lammersi,
the fourth external squamosal protuberance is offset from
the third protuberance in the dorsolateral squamosal ridge,
giving the ridge a kink (Fig.22d, see alsoDalman etal.
2018: fig.15a). In contrast, in Menefeeceratops sealeyi, all
three external squamosal protuberances are part of one dor-
solateral squamosal ridge (primary dorsolateral squamosal
ridge). In Avaceratops lammersi, Nasutoceratops titusi, and
Yehuecauhceratops mudei, the external squamosal protuber-
ance is close to the quadratojugal contact; whereas, in Crit-
tendenceratops krzyzanowskii and Menefeeceratops sealeyi,
the protuberance is farther away posteriorly from the quad-
ratojugal contact (Dalman etal. 2018: fig.15). Furthermore,
we suggest that the presence of a single external squamosal
protuberance on centrosaurine squamosals is most likely a
derived character.
The second dorsolateral squamosal ridge in Menefeecera-
tops sealeyi extends caudomedially from midway through
the primary dorsolateral ridge and is directed toward epis-
quamosal loci S1 (Figs.7, 18). This ridge gives the dorsal
surface of the squamosal a general convexity. This ridge
also seems to be present, at least to a degree, in most cen-
trosaurine species. Although not mentioned by Evans and
Ryan (2015), this ridge is well developed and pronounced
in Wendiceratops pinhornensis (Dalman et al. 2018:
fig.16b). Furthermore, in W. pinhornensis the ridge also
extends caudomedially as in M. sealeyi. In M. sealeyi, the
secondary dorsolateral squamosal ridge nearly parallels the
parietal-squamosal contact, while in W. pinhornensis, the
ridge creates a sharper angle toward episquamosal locus
S1(Fig.22d). This slight difference in angle is probably
mostly due to the different general shapes of the squamosals
of these two genera. In addition, M. sealeyi can be differenti-
ated from other derived centrosaurines, as well as the basal
centrosaurines Avaceratops lammersi, Crittendenceratops
krzyzanowskii, Nasutoceratops titusi, W. pinhornensis, and
Xenoceratops foremostensis, by the lack of a dorsoventral
groove between the “stepped” anterior and posterior portions
of the squamosal, as this characteristic groove is only present
in derived centrosaurines (Ryan 2007; Ryan etal. 2012a,
b) and some basal centrosaurines. A third, unobtrusive
dorsolateral squamosal ridge is present from mid-length
through the primary dorsolateral ridge and extending ros-
trally (= anteriorly) and is absent in other known centrosau-
rine species (Figs.7, 18).
The squamosal of Menefeeceratops sealeyi is distinctly
wider (maximum width is 57% of maximum length) than
those of other closely related centrosaurines such as Avac-
eratops lammersi (47%), Nasutoceratops titusi (47%), and
Yehuecauhceratops mudei (52%). Furthermore, the squa-
mosal of M. sealeyi is distinct in possessing a relatively long
posterior portion and significantly shorter anterior portion,
separated by the sutures for the insertion of the quadrate
and exoccipital (Figs.6, 8). In general, in centrosaurines
the anterior portion of the squamosal is usually long and
subequal in length to the posterior portion (Dodson and Cur-
rie 1988; Penkalski and Dodson 1999). In some centrosau-
rines, including a young juvenile of “Monoclonius” (TMP
82.16.11), the posterior portion is longer by approximately
3:2 (Dodson and Currie 1988). In Menefeeceratops, the ratio
is 5:1, which could indicate a young ontogenetic age for the
animal. Alternatively, this feature is plesiomorphic and is
seen only in early growth stages of stratigraphically younger
species (i.e., heterochrony). However, fusion in cranial ele-
ments (including potentially those of the episquamosals),
fusion in the dorsal vertebrae (in particular a posterior dor-
sosacral to the sacrum), and a rugose surface texture of the
squamosal are adult characteristics. This set of characteris-
tics suggests that the significantly longer posterior portion
and considerably shorter anterior portion of the squamosal is
a distinct adult character of Menefeeceratops, and not indica-
tive of a juvenile or sub-adult age of the holotype individual.
The lateral postquadrate embayment (otic notch) in Men-
efeeceratops sealeyi is elongate and gently curved, similar
to Crittendenceratops krzyzanowskii and Yehuecauhcera-
tops mudei, but distinct from Avaceratops lammersi and
Nasutoceratops titusi. The postquadrate embayment in
Menefeeceratops extends to the caudolateral angle of the
squamosal and episquamosal locus S3. This angle is sharp in
M. sealeyi, but broader in C. krzyzanowskii, Wendiceratops
pinhornensis and Y. mudei. Anteriorly in the postquadrate
embayment, near the contact for the quadratojugal, the sur-
face is smooth and continuous in M. sealeyi, whereas there
is a distinct concavity in C. krzyzanowskii and Y. mudei. The
quadrate contact in M. sealeyi is elongate but relatively shal-
low, while in C. krzyzanowskii and Y. mudei, the contact is
shortened but distinctly deep. The shape of the lateral post-
quadrate embayment (otic notch) can vary slightly through
ontogeny (see Mallon etal. 2015), although changes often
are mainly with the amount of curvature and angle of the
notch rather than it significantly changing its shape through
maturity. The squamosal is thickened and robust anterior to
the exoccipital sutural contact, partly due to the position of
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
the primary dorsolateral ridge, although the same region in
C. krzyzanowskii and Y. mudei is thin and relatively gracile.
On the ventral surface of the squamosal of Menefeecer-
atops sealeyi is a distinct low groove that approximately
follows the posterior margin, although it is not uniform
throughout its length (Figs.6, 8). As stated before, the tex-
ture is different on opposite sides of the groove. In addi-
tion, the position ventral and medial to the groove shows a
distinct concavity, while the posterior portion is distinctly
convex. This groove is present in some other centrosaurine
species such as Centrosaurus apertus, Crittendenceratops
krzyzanowskii, Diabloceratops eatoni, and Einiosaurus
procurvicornis, but absent in others centrosaurines such
as Pachyrhinosaurus canadensis, and Yehuecauhceratops
mudei (Dalman etal. 2018). The concavity of the squamosal
proximal to this groove potentially represents a region of
resorption (Tanke and Farke 2006), which would also be
indicative of an older ontogenetic stage for M. sealeyi.
Although the parietal of Menefeeceratops sealeyi is
incomplete, the preserved fragment does include an intact
portion of the lateral border and lacks epiparietal loci
(Fig.5). The presumed lack of epiparietal loci on the lateral
border distinguishes M. sealeyi from almost all other known
centrosaurine species except Machairoceratops cronusi. As
the lack of parietal ornamentation is a common character-
istic of juvenile and sub-adult centrosaurines, its potential
absence in a basal member of the subfamily may reflect het-
erochrony, in particular through peramorphosis, within more
derived centrosaurines. If epiparietal loci were present they
were most likely present only along the posterior margin
of the parietal, although that portion is not preserved in M.
sealeyi. In general, the parietals of adult centrosaurines are
extensively ornate (Evans and Ryan 2015). Some of the best
examples of centrosaurine species with extensively ornate
parietals include Crittendenceratops krzyzanowskii, Dia-
bloceratops eatoni, Stellasaurus ancellae, Styracosaurus
albertensis, and Wendiceratops pinhornensis. Although
members of the Chasmosaurinae often have simpler orna-
mentation, as in Agujaceratops mariscalensis, Anchicera-
tops ornatus, Arrhinoceratops brachyops, Chasmosaurus
belli, C. russelli, Mojoceratops (“Chasmosaurus”) perifania,
Pentaceratops sternbergi, and Utahceratops gettyi, some
species such as Vagaceratops (“Chasmosaurus”) irvinensis
(Holmes etal. 2001), Kosmoceratops richardsoni (Sampson
etal. 2010), Regaliceratops peterhewsi (Brown and Hender-
son 2015), and Spiclypeus shipporum (Mallon etal. 2016)
do not follow this trend and are examples of chasmosaurine
ceratopsians with extensively ornate frills. Nevertheless,
members of the Triceratopsini clade such as Eotriceratops
xerinsularis, Nedoceratops hatcheri, Ojoceratops fowleri,
Titanoceratops ouranos, Torosaurus latus, and Triceratops
horridus, have simple, less ornate frills. Although little of
the parietal margin is preserved, the current lack of evidence
for more extensive ornamentation in the parietal of M. sea-
leyi potentially helps distinguish it from other centrosaurines
and, in particular, from other “nasutoceratopsins” such as C.
krzyzanowskii. However, in members of the “Nasutocera-
topsini” the parietals are known only in Avaceratops lam-
mersi, C. krzyzanowskii, and Nasutoceratops titusi, and are
only partially preserved in the Oldman Formation indetermi-
nate species (CMN 8804) and in Yehuecauhceratops mudei.
Avaceratops lammersi, Menefeeceratops sealeyi, and the
Oldman Formation indeterminate species (CMN 8804) have
thin parietals. In Nasutoceratops titusi (UMNH VP 16800),
the parietal thins towards the margins of the fenestrae,
whereas in the Malta centrosaurine (GPDM 63) it thins adja-
cent to the thickened rami (Ryan etal. 2017). In Crittend-
enceratops krzyzanowskii, the parietal is robust and thick
along the lateral ramus and the posterior bar. The parietal of
M. sealeyi is incomplete; therefore, it is unclear whether the
frill was fenestrated, as in other centrosaurines. Penkalski
and Dodson (1999) argued that the specimens referred to
A. lammersi (ANSP 15800 and MOR 692) lack parietal
fenestrae. However, as pointed out by Ryan etal. (2017),
it is difficult to determine if A. lammersi (ANSP 15800 and
MOR 692) lacked the fenestrae because both specimens pre-
serve incomplete parietals and because the holotype (ANSP
15800) is a sub-adult.
The left dentary of Menefeeceratops sealeyi preserves
several mental foramina on the lateral surface, of which the
two anterior ones are above and below (= dorsal and ventral
to) each other and perpendicular to the long axis of the den-
tary (Fig.14). In general, the dentaries of ceratopsians have
a single anteriormost foramen, whereas all other foramina
are located ventral to the tooth row margin, along the long
axis of the dentary and dorsal to the ventral margin of the
dentary. This feature varies among species of centrosaurines,
suggesting interspecific, rather than intraspecific, variation.
However, more work is needed to determine the amount of
intraspecific variation of these features, and to determine if
that variation changes between different subgroups of cera-
topsids (e.g., centrosaurines or centrosaurins). As described
before, there are two elongated ridges on the lateral surface
of the dentary of M. sealeyi: dorsal and ventral. The dorsal
ridge is strongly convex and pronounced; whereas, the ven-
tral ridge is low and more inconspicuous. The ridges are
separated from each other by a shallow elongate fossa. In
the anterior region the ridges deviate dorsally and ventrally,
causing the fossa to expand anteriorly, forming a distinct tri-
angle. In general, the dentaries of other centrosaurines have
only a single ridge on the lateral surface and a single fossa
dorsal to it and ventral to the tooth row, as in Albertacera-
tops nesmoi, Utahceratops gettyi, Kosmoceratops richard-
soni, Spiclypeus shipporum, and Wendiceratops pinhornen-
sis (Ryan 2007; Sampson etal. 2010; Evans and Ryan 2015;
Mallon etal. 2016). Thus, the characteristic position of these
S. G. Dalman etal.
1 3
first two mental foramina in the dentary, the two ridges on
the lateral surface, and the fossa that separates the ridges are
potentially all distinctive features of M. sealeyi.
Phylogenetic analysis results
Our analysis resulted in 1780 most parsimonious trees (tree
length of 738 steps), a consistency index (CI) of 0.680, and
a retention index (RI) of 0.892 under default parameters in
TNT (“Tree analysis using New Technology”) (Fig.23).
Some of the major groupings within the Centrosaurinae
agree with those of previous studies, including those of
Sampson etal. (2013), Evans and Ryan (2015), Lund etal.
(2016a, b), Rivera-Sylva etal. (2016), Ryan etal. (2017),
Chiba etal. (2018), Dalman etal. (2018), and Tykoski etal.
(2019). These include the recovery of Pachyrhinosaurini and
Centrosaurini, although it is noted that Centrosaurini does
not completely agree among these previous studies and the
current phylogenetic analysis.
In our analysis, a monophyletic “Nasutoceratopsini” is
not recovered, although all species considered part of this
clade are present at or near the base of the Centrosaurinae.
This includes an unresolved clade of (Menefeeceratops
sealeyi + Yehuecauhceratops mudei + Malta centrosau-
rine + Crittendenceratops krzyzanowskii). This clade is
united by several synapomorphies, including: the presence
of a step, represented by an abrupt deflection along the
parietal-squamosal suture; episquamosal undulations very
shallow, resulting in a nearly smooth posterior squamosal
margin; epiparietal P1 oriented in the plane of the frill (not
bent or angled); and the base of epiparietal P4 positioned
at the caudodorsal (or posterodorsal) edge of the parietal
and angled dorsally. However, these last two features of the
epiparietals are not currently known in M. sealeyi. These last
three OTUs have previously been considered members of the
“Nasutoceratopsini” (Rivera-Sylva etal. 2016; Ryan etal.
2017; Chiba etal. 2018; Dalman etal. 2018). In addition,
MOR 692, Avaceratops lammersi (here referring to ANSP
15800), Nasutoceratops titusi, and CMN 8804 group near
each other in the analysis. The present study finds the first
three OTUs (minus CMN 8804) as part of an unresolved
polytomy derived from the basal clade containing Mene-
feeceratops, with these first seven OTUs (including Mene-
feeceratops) as consecutive sisters to CMN 8804. Therefore,
in the present study, the presumed members of the “Nasu-
toceratopsini” are not monophyletic, but are all found basally
within the Centrosaurinae. While Wendiceratops pinhorn-
ensis and Sinoceratops zhuchengensis do not form a clade,
they form successive sister taxa and are found outside of
other major recognized centrosaurine clades (“Nasutocera-
topsini”, Pachyrhinosaurini, Centrosaurini), with the latter
placement often recovered in other phylogenetic analysis
(Evans and Ryan 2015; Rivera-Sylva etal. 2016; Ryan etal.
2017; Chiba etal. 2018; Dalman etal. 2018). The members
of the Pachyrhinosaurini also agree with other studies, with
Pachyrhinosaurus being monophyletic. Previous studies
have found Centrosaurus apertus, Coronosaurus brinkmani,
Rubeosaurus ovatus, Spinops sternbergorum, and Styraco-
saurus albertensis within the Centrosaurini, and the present
analysis also recovers them within this clade, with the latter
two as sister taxa. Note that a recent study found Rubeosau-
rus ovatus to be a junior subjective synonym of Styracosau-
rus albertensis (Holmes etal. 2020), so the sister relation-
ships between the two OTUs in the current analysis thus
makes sense in this regard. However, Dalman etal. (2018:
fig.13) found Xenoceratops foremostensis as part of this
clade, namely as sister to Spinops sternbergorum. Several
other species that have traditionally been hard to place are
found within the Centrosaurini in the present study, includ-
ing Albertaceratops nesmoi, Diabloceratops eatoni, Machai-
roceratops cronusi, Medusaceratops lokii, and Xenoceratops
foremostensis. Although support of these clades is not as
high as desired, this still suggests the centrosaurins (and
centrosaurines) are more diverse than previously considered.
Bremer support yields relatively low decay values for
several portions of the Centrosaurinae in the current phylo-
genetic analysis. Decay values of 1 are present in the basal
parts of the Centrosaurinae, and only rise to 2 with species
more derived than those considered members of the “Nasu-
toceratopsini”. In particular, the Pachyrhinosaurini have the
highest decay values among the centrosaurines, with a decay
value of 3 for the clade containing ((Einiosaurus procurvi-
cornis + Achelousaurus horneri) + (Pachyrhinosaurus lakus-
trai + (Pachyrhinosaurus canadensis + Pachyrhinosaurus
perotorum))). Bootstrap values were generally higher among
the chasmosaurines, while all values within the Centrosauri-
nae were relatively low, with none above the 50% threshold.
Bootstrapping is a method of resampling data where values
exhibit relative confidence in the relationships represented
by various nodes, with those over 50% usually being consid-
ered as having relatively higher confidence values. Bremer
decay values, on the other hand, provide information on the
number of additional steps required to collapse nodes, with
higher values suggesting more confidence. While Bremer
decay values potentially provide better relationships among
the pachyrhinosaurins than bootstrap values, other relation-
ships are less certain. However, while the 50% majority rule
consensus tree is the one reported and figured here (Fig.23),
the strict consensus provided almost all of the same rela-
tionships. The only ones that differed were the “nasutocera-
topsins” + Menefeeceratops, which formed a large polytomy
sister to all other centrosaurines, but within the Centrosauri-
nae, and Rubeosaurus ovatus and Styracosaurus albertensis,
which are less resolved and no longer recovered as distinct
sister taxa (S2 File). The majority rule consensus tree is
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
Fig. 23 Phylogenetic relationships of Menefeeceratops sealeyi gen.
et sp. nov., within Ceratopsidae, focusing on Centrosaurinae with
Leptoceratops gracilis as the outgroup. 50% majority rule consensus
tree from 1780 most parsimonious trees (tree length = 738 steps, con-
sistency index = 0.680, retention index = 0.892) using 252 characters
across 53 species. Note: numbers listed at the nodes indicate Bremer
decay values (above) and bootstrap proportions (below). Bootstrap
values listed include those values found to be over 50%. Additional
information available in supplemental data (SF2)
S. G. Dalman etal.
1 3
provided here to show better resolution in portions of the
resulting tree, namely the possible phylogenetic relation-
ships of Menefeeceratops sealeyi.
Menefeeceratops sealeyi is a member of an unresolved
polytomy with Yehuecauhceratops mudei + Malta centro-
saurine + Crittendenceratops krzyzanowskii, with this clade
sister to all other centrosaurines. Previous phylogenetic
analyses of Lund (2010), Sampson etal. (2013), and Lund
etal. (2016b) found Avaceratops lammersi + Nasutocera-
tops titusi as sister species; however, their analyses did not
recover a previously unrecognized new clade “Nasutocera-
topsini” (see Ryan etal. 2017) within Centrosaurinae, partly
because of the unresolved placement of the basal centrosau-
rine Diabloceratops eatoni (Kirkland and DeBlieux 2010).
In contrast, the phylogenetic analysis of Ryan etal. (2012a,
b) recovered Xenoceratops foremostensis as the basal-most
member of Centrosaurinae, and basal in relation to D.
eatoni. The phylogenetic analysis of Ryan etal. (2017) found
X. foremostensis to be more derived than D. eatoni and the
ancestor to the Centrosaurini and Pachyrhinosaurini clades
with basal members Albertaceratops nesmoi, Sinoceratops
zhuchengensis, and Wendiceratops pinhornensis. The recent
analysis by Tykoski etal. (2019: fig.8) found X. foremos-
tensis outside of the Centrosaurini (and Eucentrosaura). In
addition, their study did not have X. foremostensis as sister
to the Centrosaurini or the Eucentrosaura, with several taxa
more closely related to these groups, including Wendicera-
tops pinhornensis + Sinoceratops zhuchengensis, A. nesmoi,
and Medusaceratops lokii (Tykoski etal. 2019: fig.8). Fur-
thermore, in the phylogenetic analysis of Ryan etal. (2017),
the clade Nasutoceratopsini is recovered in a polytomy.
However, this study finds D. eatoni and X. foremostensis
to be members of the Centrosaurini and instead finds the
“Nasutoceratopsini”, or at least members considered part of
it, to be basal to other centrosaurines.
Relationships ofMenefeeceratops sealeyi
While some of the topology of the Centrosaurinae in the
current phylogenetic analysis (Fig.23) is distinct from those
of previous studies (Sampson etal. 2013; Evans and Ryan
2015; Lund etal. 2016a, b; Rivera-Sylva etal. 2016; Ryan
etal. 2017; Chiba etal. 2018; Dalman etal. 2018; Tykoski
etal. 2019), most of the resulting relationships, particularly
those of higher levels, are very similar. Among centrosau-
rines, the presumed members of the “Nasutoceratopsini” are
found in close proximity to each other at the base of the
Centrosaurinae. The pachyrhinosaurins form a clade, with
Pachyrhinosaurus as a derived member. The centrosau-
rins form a group, with some previously determined basal
members recovered within it, including Albertaceratops
nesmoi, Diabloceratops eatoni, Machairoceratops cronusi,
Medusaceratops lokii, and Xenoceratops foremostensis.
Even though it is stratigraphically one of the oldest known
centrosaurines, the relatively ornate nature of the frill orna-
mentation may make D. eatoni a more derived member of
the group. Regardless of the topology of the other centro-
saurines, Menefeeceratops sealeyi is found basally within
centrosaurines, particularly within a clade sister to all other
centrosaurines. The relatively simple morphology of the
squamosal and parietal places M. sealeyi at or near the base
of the Centrosaurinae with other members with similar frill
morphology. It is noted that missing data may be influencing
the position of M. sealeyi within the Centrosaurinae, and
more material, particularly more parietal material, may help
further resolve its evolutionary position and relationships.
As stated above, Menefeeceratops groups within the clade
(Menefeeceratops sealeyi + Crittendenceratops krzyzanow-
skii + Yehuecauhceratops mudei + Malta centrosaurine),
with this clade sister to all other centrosaurines. These other
members have often been recovered basally within Centro-
saurinae in other phylogenetic analyses (Rivera-Sylva etal.
2016; Ryan etal. 2017; Chiba etal. 2018; Dalman etal.
2018; Tykoski etal. 2019). However, usually Diablocera-
tops eatoni, and sometimes Machairoceratops cronusi, are
found to be more basal in relation to the “Nasutoceratopsini”
within the Centrosaurinae. The current study recovered these
two species as members of the Centrosaurini, partially due
to their ornate parietals. Regardless, more data, particularly
of highly diagnostic elements such as a more complete pari-
etal, are needed to better clarify the phylogenetic position of
Menefeeceratops sealeyi within the Centrosaurinae and the
interrelationships of centrosaurines.
Centrosaurine evolution inNorth America
The three currently recognized groups within the subclade
Centrosaurinae (“Nasutoceratopsini”, Centrosaurini, and
Pachyrhinosaurini) are characterized by their cranial orna-
mentation (Ryan etal. 2017). This is because the current
phylogenetic analysis focused not only on cranial charac-
ters (90% of total characters), but especially those of the
parietal, squamosal, and frill (46% of total characters),
where we found the majority of variation in Menefeecera-
tops sealeyi. Members of “Nasutoceratopsini”, including;
Avaceratops lammersi, MOR 692, Crittendenceratops
krzyzanowskii, Nasutoceratops titusi, the Oldman Forma-
tion species (CMN 8804), the Malta centrosaurine (GPDM
63), and Yehuecauhceratops mudei are characterized by the
lack of a median embayment along the posterior frill mar-
gin and well-developed epimarginals that are modified as
taxonomically distinctive ornamentation (Ryan etal. 2017).
Some of the species, such as A. lammersi and N. titusi, which
are represented by nearly complete specimens, retained the
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
plesiomorphic elongate postorbital horncores seen in Dia-
bloceratops eatoni and Zuniceratops christopheri (Wolfe
and Kirkland 1998; Wolfe 2000; Kirkland and DeBlieux
2010; Ryan etal. 2017). Other plesiomorphic characters of
“Nasutoceratopsini” include unadorned frills and modestly
developed nasal ornamentation, as seen in N. titusi (Lund
2010; Sampson etal. 2013; Lund etal. 2016b). The OTUs
present in the Centrosaurini clade tend to have short postor-
bital horncores, ornamented frills, and relatively larger nasal
horncores as in Centrosaurus apertus, Rubeosaurus ovatus,
Sinoceratops zhuchengensis, and Styracosaurus albertensis.
Members of the Pachyrhinosaurini, such as Achelousaurus
horneri and three species of the genus Pachyrhinosaurus,
P. canadensis, P. lakustai, and P. perotorum, have pachyos-
totic bosses instead of horns, although Einiosaurus procur-
vicornis is an exception within this clade with a well-devel-
oped nasal horncore (Sampson 1995). The parietosquamosal
frill in pachyrhinosaurins is ornamented, but not to the same
extent as in centrosaurins (Ryan etal. 2010, 2017).
In recent years, several new ceratopsian species have been
discovered in Asia and western North America, with some
new specimens from eastern North America, also adding
new data (Wick and Lehman 2013; Tanoue and Okazaki
2014; Brown and Henderson 2015; Evans and Ryan 2015;
Mallon etal. 2016; Rivera-Sylva etal. 2016; Longrich 2016;
Farke and Phillips 2017; Lehman etal. 2017; Rivera-Sylva
etal. 2017; Ryan etal. 2017; Dalman etal. 2018). The dis-
coveries, especially those in western North America, include
species nested within the two major clades Centrosaurinae
and Chasmosaurinae. These new species shed new light
on the evolution and diversity of Ceratopsidae by provid-
ing more data to investigate the evolutionary pathways of
the various lineages within the family and conveying higher
biodiversity among this group during the Late Cretaceous.
However, the origin of various clades and groups within the
Ceratopsidae is currently unresolved (Ryan etal. 2017). Xu
etal. (2010) suggest the Ceratopsidae most likely originated
in Asia and radiated to North America during the Late Creta-
ceous, though this hypothesis was not made until the discov-
ery of the large basal centrosaurine ceratopsian Sinoceratops
zhuchengensis (Xu etal. 2010) from the Upper Cretaceous
Wangshi Group of Zhucheng, Shandong Province, China.
However, S. zhuchengensis most likely is a migrant from
North America to Asia (Ryan etal. 2017), and it most likely
is Late Campanian in age, making numerous western North
American species older than it.
The major clades of Ceratopsidae, the centrosaurines and
chasmosaurines evolved in North America and, during the
last 20 million years of the Late Cretaceous, members of
both clades underwent an explosive diversification (Ryan
etal. 2011). Xu etal. (2010) suggest that the mostly absent
status of the Ceratopsidae in Asia is partially due to the
insufficient sampling of various Upper Cretaceous deposits
and possibly to the absence of paleoenvironments favora-
ble to ceratopsians. Most other Late Cretaceous dinosaur
clades are found in Asia and North America, including the
Ankylosauridae, Alvarezsauridae, Dromaeosauridae, Elmi-
sauridae, Hadrosauridae, Leptoceratopsidae, Nodosauridae,
Ornithomimidae, Oviraptoridae, Pachycephalosauria, Tita-
nosauridae, Troodontidae, and Tyrannosauridae (Russell
1993; Hutchinson and Chiappe 1998; Sullivan 1999, 2000;
Kirkland and Wolfe 2001; Hurum and Sabath 2003; Currie
2003, 2005; Wilson 2005; Zanno 2006, 2010a, b; Xu etal.
2007, 2010, 2011; Longrich and Currie 2009a, b; Prieto-
Márquez 2010; Carr etal. 2011, 2017; D’Emic etal. 2011;
Fowler and Sullivan 2011; Jasinski and Sullivan 2011, 2016;
Jasinski etal. 2011, 2020; Lucas etal. 2011, 2016; Ryan
etal. 2011; Sullivan etal. 2011a, b; Turner etal. 2012; Evans
etal. 2013a, b; Arbour etal. 2014; Longrich 2014, 2016;
Hedrick etal. 2015; Jasinski 2015; Brusatte and Carr 2016;
Dalman etal. 2017; Wiersma and Irmis 2018; Zanno etal.
2019). Clearly, the presence of these groups in both North
America and Asia has been well established through many
recent studies, but the place of origin and the method of
dispersal have been less well understood for these groups.
The apparent dearth of ceratopsids in Asia remains to be
explained.
Xu etal. (2010) suggest that during the Cretaceous, mul-
tiple dispersal events occurred in ceratopsians and that all
the dispersals might be from Asia to North America. This
was largely implied not only by the basal phylogenetic posi-
tion they recovered for Sinoceratops zhuchengensis within
Centrosaurinae, but also the position of Turanoceratops
tardabilis as sister to the Ceratopsidae and the number of
neoceratopsians (basal in relation to coronosaurians) and
basal ceratopsians from Asia (Xu etal. 2010). Other workers
(Ji etal. 2003; Holtz 2004; Brusatte etal. 2010; Brusatte and
Carr 2016; Carr etal. 2017; Zanno etal. 2019) have sug-
gested a similar pattern of dispersal for some other dinosaur
groups such as the derived Ornithomimosauria and Tyran-
nosauridae. However, more recent work suggests the oldest
tyrannosaurids are from North America (Larson 2010; Dal-
man etal. 2016; Dalman and Lucas 2018; McDonald etal.
2018), and they subsequently dispersed to Asia during the
Late Campanian (Loewen etal. 2013b; Dalman and Lucas
2016, 2018).
Current evidence in the fossil record shows that some
of the first centrosaurines, such as Diabloceratops eatoni
from the Wahweap Formation (~ 80Ma) of southern Utah,
originated in southern Laramidia and dispersed northward
(Kirkland and DeBlieux 2010). Other specimens referred to
Diabloceratops from the lower Wahweap Formation support
this hypothesis (Kirkland and Deblieux 2010; Loewen etal.
2013a; Fowler 2017). This hypothesis is further supported
by the presence of Menefeeceratops sealeyi in the Upper
Cretaceous deposits of the Menefee Formation (~ 83Ma)
S. G. Dalman etal.
1 3
of northwestern New Mexico. While there are few well-
sampled strata in northern Laramidia around 80Ma, the
lower part of the Foremost Formation in southern Alberta
and the lower portion of the Two Medicine Formation in
western Montana both span this time period, with more
recent remains of hadrosaurids (Acristavus gagslarsoni and
Gryposaurus latidens) recovered from the lower Two Medi-
cine Formation in Montana (the latter from the base of litho-
facies 3), making both of these approximately between 81
and 80Ma (Gates etal. 2011; Freedman-Fowler and Horner
2015; Fowler 2017). In addition, the Milk River Formation
in southern Alberta, which is slightly older than the Men-
efee Formation, has evidence of leptoceratopsids (Ryan etal.
2012a, b; Evans etal. 2013a, b), but no definitive evidence
of centrosaurines. Russell (1935) reported tooth fragments
he attributed to “cf. Brachyceratops”; however, these speci-
mens should more accurately be referred to indeterminate
ceratopsids, as they are too fragmentary for further identifi-
cation. In addition, based on the revised biostratigraphy and
recalibrated ages (Fowler 2017), M. sealeyi represents the
oldest known member of the Centrosaurinae. Based on its
oldest members being present in southern Laramidia, this
suggests the clade first evolved in this region before dispers-
ing to northern Laramidia.
Conversely, Ryan etal. (2017) suggest that Centrosau-
rinae first evolved in northern Laramidia and then dis-
persed south. This argument is based on the presence of
Avaceratops lammersi (Dodson 1986) in the Upper Creta-
ceous deposits of the lower Judith River Formation, Mon-
tana. However, Menefeeceratops sealeyi is ~ 5 million years
older than A. lammersi (see revised biostratigraphic range
and age for A. lammersi in Fowler 2017). According to the
phylogenetic analysis of Ryan etal. (2017), the two sub-
clades Centrosaurini and “Nasutoceratopsini” split in the
late Santonian and continued into the Late Campanian. The
recent analysis by Tykoski etal. (2019: fig.8) suggests an
early Campanian split between Centrosaurini and Pachy-
rhinosaurini, with the more derived centrosaurines split-
ting off from the “Nasutoceratopsini” during the Santonian.
Aside from isolated teeth from the Santonian Milk River
Formation previously assigned to a centrosaurine by Rus-
sell (1935), which again should instead be referred to an
Fig. 24 Menefeeceratops sealeyi gen. et sp. nov. Life reconstruction of Menefeeceratops sealeyi (artwork by S. Krasovskiy)
A new ceratopsid dinosaur from the Upper Cretaceous of northwestern New Mexico, USA
1 3
indeterminate ceratopsid, good evidence for centrosaurines
prior to the Campanian is lacking. Most evidence of cen-
trosaurines from the lower Campanian and lower middle
Campanian comes from southern Laramidia, further sug-
gesting the clade’s origin in the south. The presence of Cam-
panian strata (around 80Ma) to the north, which currently
lack definitive evidence of centrosaurines, also suggests their
absence in this region at that time. There is no current evi-
dence from this time of centrosaurines in the north, and the
oldest centrosaurines are still currently found to the south,
which agrees with our hypothesis of the origin of the sub-
family to the south and subsequent dispersal to the north.
In addition, evidence for the co-existence of the Centrosau-
rini and “Nasutoceratopsini” in the Campanian is supported
by the discovery of the indeterminate “nasutoceratopsin”
species CMN 8804 (Ryan etal. 2017) and the presence of
TMP 1965.23.26 (referred to “Centrosaurus” by Dalman
etal., 2018) from the Campanian of the Oldman Formation
of Alberta. Furthermore, the data presented by Ryan etal.
(2017) show that, during the Late Cretaceous, centrosaurins
and “nasutoceratopsins” briefly overlapped temporally and
paleobiogeographically. The known members of the Cen-
trosaurini from the Oldman Formation include Albertacera-
tops nesmoi (Ryan 2007), Centrosaurus apertus (Chiba etal.
2015), Coronosaurus brinkmani (Ryan etal. 2012a, b), and
Wendiceratops pinhornensis (Evans and Ryan 2015), thus
leading to the possibility that centrosaurins co-existed with
“nasutoceratopsins” in at least some regions of Alberta dur-
ing some of the intervals of deposition of the Oldman For-
mation. However, extensive sampling of various Cretaceous
deposits, particularly those in the Santonian and early to
middle Campanian, is still needed for the recovery of addi-
tional specimens and for a better understanding of the origin
and evolution of Centrosaurini and “Nasutoceratopsini” in
North America.
Conclusions
Menefeeceratops sealeyi is a new genus and species that rep-
resents the oldest current record of centrosaurine ceratopsid
in North America (Fig.24). It is basal to Centrosaurini and
Pachyrhinosaurini and potentially is a member of the “Nasu-
toceratopsini”. Recognition of Menefeeceratops sealeyi adds
to the growing species diversity of the Centrosaurinae in
North America, and its presence in southern Laramidia fills
in part of the evolutionary gap between the earlier Zunicera-
tops christopheri (~ 90Ma) and the more derived ceratop-
sids known from the late Campanian in North America. The
phylogenetic analysis suggests that derived members of the
Centrosaurinae evolved rather quickly and lived at the same
time as basal members. The presence of the oldest members
of the Centrosaurinae in southern Laramidia suggests the
clade evolved in the south and radiated north through the late
Campanian. This is further corroborated by the presence of
Campanian strata (~ 80Ma) to the north (Alberta and Mon-
tana) that currently lacks evidence of centrosaurines. More
material is needed, particularly of the parietal, to determine
a more confident phylogenetic position of M. sealeyi and
other potential “nasutoceratopsins” at, or near, the base of
the Centrosaurinae.
Supplementary Information The online version contains supplemen-
tary material available at https:// doi. org/ 10. 1007/ s12542- 021- 00555-w .
Acknowledgements We thank Paul Sealey for the discovery of the
holotype specimen of Menefeeceratops sealeyi. The Bureau of Land
Management provided the permits and access to the collecting locali-
ties described herein. We thank Andy A. Farke for sharing pictures
of various specimens of centrosaurine ceratopsians and Héctor E.
Rivera-Sylva for sharing the pictures of Yehuecauhceratops. Robert
Giegengack and Joan Bucilli provided support and travel was partially
funded by the Walker Endowment Research Grant and the University
of Pennsylvania Paleontology Research Grant. We are most grateful
to the reviewers of earlier versions of this paper, including; Victoria
Arbour, Andrew A. Farke, Catherine A. Forster, Denver Fowler, Mark
A. Loewen, Nicholas R. Longrich, Michael J. Ryan, and an anonymous
reviewer who all provided critical comments that greatly improved all
aspects of the manuscript. Thanks also to Hans-Dieter Sues and Mike
Reich for editorial help and comments that also improved this paper.
Great thanks to the paleoartist Sergey Krasovskiy for the life recon-
struction of Menefeeceratops sealeyi.
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