Vol 465 | 27 May 2010 | doi:10.1038/nature09019 LETTERS A Late Cretaceous ceratopsian dinosaur from Europe with Asian affinities Attila O˝si1, Richard J. Butler2 & David B. Weishampel3 Ceratopsians (horned dinosaurs) represent a highly diverse and caudolateral process of the premaxilla is curved along its length abundant radiation of non-avian dinosaurs1–5 known primarily becoming nearly horizontal caudally; (4*) the buccal margins of from the Cretaceous period (65–145 million years ago). This radi- the predentary are sharp and not bevelled. ation has been considered to be geographically limited to Asia and Description. The short rostral bone strongly curves ventrally to a western North America1–3, with only controversial remains reported sharp point, similar to the condition in Archaeoceratops oshimai15, from other continents. Here we describe new ceratopsian cranial Protoceratops andrewsi1 and Magnirostris dodsoni8. Well-developed material from the Late Cretaceous of Iharku´t, Hungary6,froma lateral processes of the rostral extend along more than half of the coronosaurian ceratopsian, Ajkaceratops kozmai. Ajkaceratops is ventral margin of the premaxilla. The surface of the rostral is heavily most similar to ‘bagaceratopsids’ such as Bagaceratops and pitted, indicating high vascularization and a covering keratinous Magnirostris, previously known only from Late Cretaceous east beak. Asia3,5,7,8. The new material unambiguously demonstrates that The body of the premaxilla is shallow, and the narial fossa extends ceratopsians occupied Late Cretaceous Europe and, when con- closer to the oral margin than in other non-ceratopsid ceratopsians1. sidered with the recent discovery of possible leptoceratopsid teeth The premaxillae and rostral bones form a strongly concave, vaulted, oval from Sweden9, indicates that the clade may have reached Europe on secondary palate that is defined laterally by sharp, edentulous cutting at least two independent occasions. European Late Cretaceous dino- margins. The caudal edge of the premaxilla and the caudodorsal process saur faunas have been characterized as consisting of a mix of form the rostral and dorsal margins of a large, fully perforate and oval endemic ‘relictual’ taxa and ‘Gondwanan’ taxa, with typical Asian accessory fenestra between the premaxilla and the maxilla, as in the and North American groups largely absent10,11. Ajkaceratops Asian basal coronosaurian ceratopsians Bagaceratops rozhdestvenskyi6 demonstrates that this prevailing biogeographical hypothesis is and Magnirostris dodsoni15. Although the nasal is not preserved, a overly simplified and requires reassessment. Iharku´t was part of bevelled surface on the medial surface of the caudodorsal process re- the western Tethyan archipelago, a tectonically complex series of presents the articular surface for this bone. The nearly horizontal ori- island chains between Africa and Europe12,andtheoccurrenceofa entation of the caudodorsal process suggests that, as in Bagaceratops and coronosaurian ceratopsian in this locality may represent an early Magnirostris16, the nasal was excluded from the margin of the accessory Late Cretaceous ‘island-hopping’ dispersal across the Tethys Ocean. fenestra. An accessory fenestra between the premaxilla and the maxilla is Ceratopsia Marsh, 1890 also present in the North American non-ceratopsid coronosaurian Neoceratopsia Sereno, 1986 Zuniceratops and in some basal chasmosaurine and centrosaurine 16–18 Coronosauria Sereno, 1986 ceratopsids . However, in these taxa the nasal forms the dorsal mar- Ajkaceratops kozmai gen. et sp. nov. gin of this accessory fenestra, which is proportionally much smaller and is relatively much more dorsally positioned (its ventral margin is far Etymology. Ajka: the town of Ajka, which is close to the type locality; above that of the external naris). This fenestra occurred in several ceratops (Greek): horned face. (Intended pronunciation: oi-ka-sera- lineages of Coronosauria and may have been secondarily lost in derived tops.) The species is named in honour of Ka´roly Kozma. chasmosaurines and centrosaurines16. Holotype. MTM V2009.192.1, fused premaxillae and rostral bones The four predentaries represent different ontogenetic stages of with fragments of the maxillae (Fig. 1a, b); housed in the collections Ajkaceratops (Supplementary Fig. 2). The rostral ends of the preden- of the Hungarian Natural History Museum, Budapest, Hungary. taries are acutely pointed. The largest specimen is more strongly Referred material. MTM V2009.193.1 (Fig. 1c–e), V2009.194.1, curved in lateral view than smaller specimens, with a strongly V2009.195.1, V2009.196.1: four predentary bones. upturned rostral tip. Unusually, the edges of the predentary are Horizon and locality. Csehba´nya Formation (Upper Cretaceous, sharp, and not bevelled as occurs in many ceratopsians. Caudally, Santonian13), Iharku´t, Veszpre´m County, Bakony Mountains, Trans- the predentary has a flattened and very broad, parallel-sided ventral danubian Range, western Hungary. Iharku´t has previously yielded a process. The surfaces of the predentaries are heavily ornamented by typical European Late Cretaceous dinosaur assemblage of endemic pits and grooves, similar to the surface of the rostral. rhabdodontid ornithopods and basal nodosaurid ankylosaurs6,14. Three unambiguous synapomorphies demonstrate the ceratopsian Diagnosis. Differs from all other coronosaurian ceratopsians in the affinities of Ajkaceratops: the presence of a neomorphic rostral bone following character combination (* indicates autapomorphies): (1) (unique to ceratopsians); the presence of a strongly vaulted premaxillary large oval accessory fenestra are present between the premaxilla and palate; and the presence of a ventral process of the predentary that is maxilla, with the nasal excluded from its margin; (2*) the part of the more than half of the transverse width of the predentary1,3,5.In premaxilla ventral to the external naris and the accessory fenestra is Ceratopsia, the presence of a strongly pointed rostral bone with well- dorsoventrally shallow relative to its rostrocaudal length; (3*) the developed lateral processes supports referral to Neoceratopsia3.The 1Hungarian Academy of Sciences, Hungarian Natural History Museum, Research Group for Paleontology, Ludovika te´r 2, Budapest 1083, Hungary. 2Bayerische Staatssammlung fu¨r Pala¨ontologie und Geologie, Richard-Wagner-Straße 10, Munich 80333, Germany. 3Center for Functional Anatomy and Evolution, Johns Hopkins University, Baltimore, Maryland 21205, USA. 466 ©2010 Macmillan Publishers Limited. All rights reserved NATURE | Vol 465 | 27 May 2010 LETTERS asn abem r en r mp acf 1 cm vpp rlp vp smp vp cd e Figure 1 | Anatomy of Ajkaceratops kozmai gen. et sp. nov. a, b, Holotype em, edentulous margin of premaxilla; en, external naris; mp, fragments of MTM V2009.192.1, fused rostral and premaxillae in lateral (a) and ventral rostral processes of maxillae; r, rostral bone; rlp, lateral process of rostral; (b) views. c–e, Referred material MTM V2009.193.1, predentary in lateral smp, sharp margin of predentary; vp, ventral process of predentary; vpp, (c), ventral (d) and dorsal (e) views. acf, inferred position of accessory vaulted premaxillary palate. fenestra between the premaxilla and maxilla; asn, articular surface for nasal; fully perforate accessory opening between the premaxilla and maxilla is related and near contemporaneous coronosaurians such as present in a number of Late Cretaceous coronosaurians, such as the Protoceratops and the largest Asian bagaceratopsids. Although several Asian Bagaceratops (including several bagaceratopsids that are probably features are potentially consistent with some degree of osteological synonymous with this genus3,5,7) and Magnirostris8 (possibly synony- maturity, ontogenetic stage cannot be assessed with certainty at pre- mous with Bagaceratops7), as well as the North American Zuniceratops18 sent. Further discoveries are thus required to determine whether and basal ceratopsids16,17. This opening is absent in earlier and more Ajkaceratops is a dwarfed taxon, as has been proposed for other Late basal ceratopsians (including non-coronosaurians and leptocera- Cretaceous dinosaurs from the western Tethyan archipelago24–27. topsids)1,3,4. The proportionally large size of the accessory opening Ajkaceratops seems to be part of a Late Cretaceous radiation of and the exclusion of the nasal from its margin are most similar to the coronosaurian ceratopsians otherwise known only from Asia and bagaceratopsids Bagaceratops and Magnirostris (some recent work North America. The historical biogeography of coronosaurian cer- questions whether bagaceratopsids form a distinct clade as generally atopsians is complex, with several inferred dispersal events between hypothesized16). These similarities suggest that Ajkaceratops is a coronosaurian, close to bagaceratopsids and basal to the Zuniceratops 1 Ceratopsidae clade. a b 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 5 cm 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 c particularly striking evolutionary convergence observed between cera- topsian