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1. Vol 465|27 May 2010|doi:10.1038/nature09019
©2010 Macmillan Publishers Limited. All rights reserved
LETTERS
A Late Cretaceous ceratopsian dinosaur from Europe
with Asian affinities
Attila Ősi1
, Richard J. Butler2
& David B. Weishampel3
Ceratopsians (horned dinosaurs) represent a highly diverse and
abundant radiation of non-avian dinosaurs1–5
known primarily
from the Cretaceous period (65–145 million years ago). This radi-
ation has been considered to be geographically limited to Asia and
western North America1–3
, with only controversial remains reported
from other continents. Here we describe new ceratopsian cranial
material from the Late Cretaceous of Iharkút, Hungary6
, from a
coronosaurian ceratopsian, Ajkaceratops kozmai. Ajkaceratops is
most similar to ‘bagaceratopsids’ such as Bagaceratops and
Magnirostris, previously known only from Late Cretaceous east
Asia3,5,7,8
. The new material unambiguously demonstrates that
ceratopsians occupied Late Cretaceous Europe and, when con-
sidered with the recent discovery of possible leptoceratopsid teeth
from Sweden9
, indicates that the clade may have reached Europe on
at least two independent occasions. European Late Cretaceous dino-
saur faunas have been characterized as consisting of a mix of
endemic ‘relictual’ taxa and ‘Gondwanan’ taxa, with typical Asian
and North American groups largely absent10,11
. Ajkaceratops
demonstrates that this prevailing biogeographical hypothesis is
overly simplified and requires reassessment. Iharku´t was part of
the western Tethyan archipelago, a tectonically complex series of
island chains between Africa and Europe12
, and the occurrence ofa
coronosaurian ceratopsian in this locality may represent an early
Late Cretaceous ‘island-hopping’ dispersal across the Tethys Ocean.
Ceratopsia Marsh, 1890
Neoceratopsia Sereno, 1986
Coronosauria Sereno, 1986
Ajkaceratops kozmai gen. et sp. nov.
Etymology. Ajka: the town of Ajka, which is close to the type locality;
ceratops (Greek): horned face. (Intended pronunciation: oi-ka-sera-
tops.) The species is named in honour of Ka´roly Kozma.
Holotype. MTM V2009.192.1, fused premaxillae and rostral bones
with fragments of the maxillae (Fig. 1a, b); housed in the collections
of the Hungarian Natural History Museum, Budapest, Hungary.
Referred material. MTM V2009.193.1 (Fig. 1c–e), V2009.194.1,
V2009.195.1, V2009.196.1: four predentary bones.
Horizon and locality. Csehba´nya Formation (Upper Cretaceous,
Santonian13
), Iharku´t, Veszpre´m County, Bakony Mountains, Trans-
danubian Range, western Hungary. Iharku´t has previously yielded a
typical European Late Cretaceous dinosaur assemblage of endemic
rhabdodontid ornithopods and basal nodosaurid ankylosaurs6,14
.
Diagnosis. Differs from all other coronosaurian ceratopsians in the
following character combination (* indicates autapomorphies): (1)
large oval accessory fenestra are present between the premaxilla and
maxilla, with the nasal excluded from its margin; (2*) the part of the
premaxilla ventral to the external naris and the accessory fenestra is
dorsoventrally shallow relative to its rostrocaudal length; (3*) the
caudolateral process of the premaxilla is curved along its length
becoming nearly horizontal caudally; (4*) the buccal margins of
the predentary are sharp and not bevelled.
Description. The short rostral bone strongly curves ventrally to a
sharp point, similar to the condition in Archaeoceratops oshimai15
,
Protoceratops andrewsi1
and Magnirostris dodsoni8
. Well-developed
lateral processes of the rostral extend along more than half of the
ventral margin of the premaxilla. The surface of the rostral is heavily
pitted, indicating high vascularization and a covering keratinous
beak.
The body of the premaxilla is shallow, and the narial fossa extends
closer to the oral margin than in other non-ceratopsid ceratopsians1
.
The premaxillae and rostral bones form a strongly concave, vaulted, oval
secondary palate that is defined laterally by sharp, edentulous cutting
margins. The caudal edge of the premaxilla and the caudodorsal process
form the rostral and dorsal margins of a large, fully perforate and oval
accessory fenestra between the premaxilla and the maxilla, as in the
Asian basal coronosaurian ceratopsians Bagaceratops rozhdestvenskyi6
and Magnirostris dodsoni15
. Although the nasal is not preserved, a
bevelled surface on the medial surface of the caudodorsal process re-
presents the articular surface for this bone. The nearly horizontal ori-
entation of the caudodorsal process suggests that, as in Bagaceratops and
Magnirostris16
, the nasal was excluded from the margin of the accessory
fenestra. An accessory fenestra between the premaxilla and the maxilla is
also present in the North American non-ceratopsid coronosaurian
Zuniceratops and in some basal chasmosaurine and centrosaurine
ceratopsids16–18
. However, in these taxa the nasal forms the dorsal mar-
gin of this accessory fenestra, which is proportionally much smaller and
is relatively much more dorsally positioned (its ventral margin is far
above that of the external naris). This fenestra occurred in several
lineages of Coronosauria and may have been secondarily lost in derived
chasmosaurines and centrosaurines16
.
The four predentaries represent different ontogenetic stages of
Ajkaceratops (Supplementary Fig. 2). The rostral ends of the preden-
taries are acutely pointed. The largest specimen is more strongly
curved in lateral view than smaller specimens, with a strongly
upturned rostral tip. Unusually, the edges of the predentary are
sharp, and not bevelled as occurs in many ceratopsians. Caudally,
the predentary has a flattened and very broad, parallel-sided ventral
process. The surfaces of the predentaries are heavily ornamented by
pits and grooves, similar to the surface of the rostral.
Three unambiguous synapomorphies demonstrate the ceratopsian
affinities of Ajkaceratops: the presence of a neomorphic rostral bone
(unique to ceratopsians); the presence of a strongly vaulted premaxillary
palate; and the presence of a ventral process of the predentary that is
more than half of the transverse width of the predentary1,3,5
. In
Ceratopsia, the presence of a strongly pointed rostral bone with well-
developed lateral processes supports referral to Neoceratopsia3
. The
1
Hungarian Academy of Sciences, Hungarian Natural History Museum, Research Group for Paleontology, Ludovika te´r 2, Budapest 1083, Hungary. 2
Bayerische Staatssammlung fu¨r
Pala¨ontologie und Geologie, Richard-Wagner-Straße 10, Munich 80333, Germany. 3
Center for Functional Anatomy and Evolution, Johns Hopkins University, Baltimore, Maryland
21205, USA.
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2. NATURE|Vol 465 |27 May 2010 LETTERS
©2010 Macmillan Publishers Limited. All rights reserved
5 cm
Figure 1 | Anatomy of Ajkaceratops kozmai gen. et sp. nov. a, b, Holotype
MTM V2009.192.1, fused rostral and premaxillae in lateral (a) and ventral
(b) views. c–e, Referred material MTM V2009.193.1, predentary in lateral
(c), ventral (d) and dorsal (e) views. acf, inferred position of accessory
fenestra between the premaxilla and maxilla; asn, articular surface for nasal;
em, edentulous margin of premaxilla; en, external naris; mp, fragments of
rostral processes of maxillae; r, rostral bone; rlp, lateral process of rostral;
smp, sharp margin of predentary; vp, ventral process of predentary; vpp,
vaulted premaxillary palate.
fully perforate accessory opening between the premaxilla and maxilla is
present in a number of Late Cretaceous coronosaurians, such as the
Asian Bagaceratops (including several bagaceratopsids that are probably
synonymous with this genus3,5,7
) and Magnirostris8
(possibly synony-
mous with Bagaceratops7
), as well as the North American Zuniceratops18
and basal ceratopsids16,17
. This opening is absent in earlier and more
basal ceratopsians (including non-coronosaurians and leptocera-
topsids)1,3,4
. The proportionally large size of the accessory opening
and the exclusion of the nasal from its margin are most similar to the
bagaceratopsids Bagaceratops and Magnirostris (some recent work
questions whether bagaceratopsids form a distinct clade as generally
hypothesized16
). These similarities suggest that Ajkaceratops is a
coronosaurian, close to bagaceratopsids and basal to the
Zuniceratops 1 Ceratopsidae clade.
Evidence for Gondwanan ceratopsians19,20
is highly controversial and
most reviews have assumed that ceratopsians were restricted to central
and east Asia and western North America1,3
. Two recent papers report
putative ceratopsians on the basis of scarce isolated teeth from Late
Cretaceous northern Europe9,21
. The identification of ceratopsians based
on isolated teeth must be treated with caution because ornithischian
dinosaur dentition is well-documented as highly homoplastic, with
particularly striking evolutionary convergence observed between cera-
topsian and ornithopod ornithischians2,21–23
. Only a few dental charac-
ters support the probable ceratopsian affinities of several teeth from the
Campanian of Sweden (see Supplementary Information). These char-
acters indicate referral of this material to Leptoceratopsidae9
, although
non-dental remains are required to establish this identity with certainty.
The historic tooth taxon Craspedodon from the Late Cretaceous of
Belgium was recently reinterpreted as possibly ceratopsian, but may
instead represent a hadrosauroid ornithopod21
. The comparably much
better sampled Late Cretaceous terrestrial sites of southern Europe have
previously failed to yield ceratopsian material11. The presence of
Ajkaceratops kozmai in the island chains of southern Europe and the
probable presence of a phylogenetically distinct lineage of leptoceratop-
sids on the northern Europe craton indicates at least two independent
occupations of the continent by horned dinosaurs.
The largest specimens of Ajkaceratops are considerably smaller
(body length estimated at approximately 1 m) than other closely
related and near contemporaneous coronosaurians such as
Protoceratops and the largest Asian bagaceratopsids. Although several
features are potentially consistent with some degree of osteological
maturity, ontogenetic stage cannot be assessed with certainty at pre-
sent. Further discoveries are thus required to determine whether
Ajkaceratops is a dwarfed taxon, as has been proposed for other Late
Cretaceous dinosaurs from the western Tethyan archipelago24–27
.
Ajkaceratops seems to be part of a Late Cretaceous radiation of
coronosaurian ceratopsians otherwise known only from Asia and
North America. The historical biogeography of coronosaurian cer-
atopsians is complex, with several inferred dispersal events between
Figure 2 | Late Cretaceous palaeogeography and bagaceratopsid skull
outlines. a, b, Skull outlines, to scale, for Ajkaceratops kozmai (a) (preserved
bones in black, remainder of skull based upon Magnirostris) and the Asian
bagaceratopsid Magnirostris (b). Although the exact phylogenetic position
of Ajkaceratops is unclear it is probably closely related to the Asian
bagaceratopsids Magnirostris and Bagaceratops. c, Late Cretaceous
palaeogeographical map showing locations of Ajkaceratops and Asian
bagaceratopsids (map courtesy of R. Blakey).
467
asn
em
r
en
r
acf
1 cm

3. LETTERS NATURE|Vol 465 |27 May 2010
©2010 Macmillan Publishers Limited. All rights reserved
western North America and Asia3
. However, the similarities between
Ajkaceratops and the Asian bagaceratopsids Bagaceratops and
Magnirostris indicate that the presence of a ceratopsian in the western
Tethyan archipelago probably results from an early Late Cretaceous
dispersal event from Asia, possibly by island-hopping across the
Tethys Ocean (Fig. 2). This dispersal would have been facilitated
by subduction of the Tethys Ocean along the southern Asiatic margin
with resultant insular island arches in this region12
. Previous biogeo-
graphical hypotheses have suggested isolation of European vertebrate
faunas from Asia and North America during the Early Cretaceous,
followed by the development during the Late Cretaceous of an
endemic and supposedly relictual dinosaur fauna (including rhabdo-
dontid ornithopods and basal nodosaurid ankylosaurs) influenced
by immigration of Gondwanan forms such as bothremydid turtles,
titanosaurian sauropods and abelisauroid theropods10,11,28
. By contrast,
the discovery of Ajkaceratops kozmai indicates that the European island
faunas of the western Tethys comprised not only endemic and
Gondwanan forms, but also taxa typical of the Late Cretaceous of
Asia and North America. An emerging and unexpected pattern of
European/Asian faunal links in the Late Cretaceous may also be sup-
ported by the possible leptoceratopsids from Sweden9
and by recent
descriptions of European hadrosauroids and hadrosaurids26,29,30
.
Ajkaceratops kozmai thus adds new complexity to our understanding
of Late Cretaceous dinosaur faunas and demonstrates the need for re-
evaluation of current biogeographical hypotheses.
Received 17 November 2009; accepted 17 March 2010.
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Supplementary Information is linked to the online version of the paper at
www.nature.com/nature.
Acknowledgements We thank L. Kocsis, P. Barrett, D. Norman, P. Dodson,
J. Kirkland, P. Makovicky, S. Sampson, P. Godefroit, Z. Csiki, J. Pa´lfy and R. Sissons
for discussion, R. Blakey for the use of the palaeogeographical reconstruction,
P. Gulya´s for preparation, J. Kirkland for unpublished data and U. Go¨hlich for
logistical support. Research was supported by the Hungarian Scientific Research
Fund (OTKA PD 73021) and the Hantken Foundation (A.O˝.), and a Humboldt
Postdoctoral Fellowship (R.J.B.). This is MTA–MTM Paleo contribution 109.
Author Contributions A.O˝. collected the material. A.O˝. and R.J.B. carried out the
anatomical description. A.O˝. prepared the figures. All authors discussed the results
and contributed to the manuscript.
Author Information Reprints and permissions information is available at
www.nature.com/reprints. The authors declare no competing financial interests.
Correspondence and requests for materials should be addressed to A.O˝.
(hungaros@freemail.hu).
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