ORYCTOS,Vol. I : 87-104,Octobre 1998 SMALLTHEROPODS FROM THE LATE CRETACEOUS OFTHE HATEG BASIN OryESTERNROMANIA) . AN UNEXPECTED DIVERSITY AT THE TOP OF THE FOOD CHAIN Zoltan CSIKI & Dan GRIGORESCU Bd. N. BalcescuNr. 1, 70111 Bucharest,Romania ; Laboratoryof Paleontology, Faculty of Geology & Geophysics,University of Bucharest. Abstract : The LateMaastrichtian deposits of the HategBasin have yielded numerousremains of herbivorousdinosaurs (tita- nosaurids,ornithopods, nodosaurids); but thoseof theropodsare scarce, represented mostly by teethand hindlimb elements. New materialallows the recognitionof an unexpecteddiversity of thesepredators in the Hategfauna. Teeth of variousmor- phologiesare reported here to representseveral distinct taxa of small theropods:a velociraptorinedromaeosaurid, a "troo- dontidlike" smalltheropod, cf . Euronychodonand perhaps a fourth,peculiar small theropod with sharp,but unserratedcari- naeon the teeth.Re-examination of previouslypublished theropod material also suggestssuch diversity. Femora, previous- ly refenedto Elopteryx,probably belong to a derivedmaniraptoran. A distalend of a femur seemsto documenta smallcera- tosaur,while sometibiotarsi (holotypes of BradycnemeandHeptasteornis) may representa non-maniraptorantetanuran the- ropod.Without diagnosticremains of smalltheropods, it is inappropriateto give the reportedmaterial generic names; conse- quentlyinformal useof the publishednames 'Elopteryx' and'Bradycneme' is recommended.Moreover, for mostpart of the isolatedtheropod remains from Hategthere are no reasonsto groupthem under the samename; one suchcase may be repre- sented,however, by someskull elementsand the velociraptorineteeth. The diversityof the small theropodsin the Hategfauna, together with the absenceof a large "top" theropod,represents the first suchcase reported for Late Cretaceousfaunas. This phenomenonis probablylinked to the restricted,insular habitat of the Hategfauna, which could not accommodateand supportany largersized predator. Key words : Hateg Basin, I'ate Maastrichtian, ceratosaurs,maniraptorans, dromaeosaurids,Euronychodon, diver- siry.insular habitat. Les petits théropodesdu Crétacéterminal du Bassindu Hateg (Ouestde la Roumanie): une diversité inattendueau sommetde la pyramide trophique Résumé : Les dépôtsd'âge Maastrichtien terminal du Bassinde Hateg ont fourni de nombreuxrestes de dinosauresherbi- vores(titanosauridés, ornithopodes, nodosauridés), mais ceux de théropodessont rares, représentés par desdents et desfrag- mentsde membrespostérieurs. Le nouveau matériela permisde mettreen évidenceune diversitéinattendue de cespréda- teurs dansla fauned'Hateg. Des dentsde morphologiesvariées attestent la présencede différents'l4ronsde petits théro- podes: un dromaeosauridé,un petit théropodeproche des troodontidés, cf. Euronychodonet peut-êtreun quatrièmepetit théropodecurieux avecdes dents à carènessaillantes mais sanscrénelures. Un nouvelexamen des restes des petits théro- podesde Hateg déjà publiésconfirme cette diversité. Les fémurs,rapportés à Elopteryx, appartiennentprobablement à un maniraptorien;I'extrémité distale de fémur sembledocumenter un petit cératosaure,tandis que des tibiotarses (holotypes de Bradycnemeet Heptasteornls)pounaient représenterun théropodetetanurane primitif. En l'absencede restesdiagnosiques des petits théropodes, il sembleprématuré de donnerdes noms génériques; nous recom- mandonspar conséquentI'utilisation informelle des noms publiés 'Elopteryx'et'Bradycneme'.De plus, il n'y a paslieu de regrouperdes restes isolés sous le mêmenom générique;le seulcas où I'on peut sepermettre de le faire concernequelques restesde crânespubliés auparavant et les dentsde dromaeosauridés. La diversitédes petits théropodesdans la fauned'Hateg, ainsi que l'absencede grandsthéropodes, est un casunique dans les faunesdu Crétacéterminal. Ce phénomèneest probablementlié à un habitatinsulaire qui n'a paspermis la colonisation par un grand prédateur. Mots clés : Bassin du Hateg, Maastrichtien terminal, Ceratosauria, Maniraptora, Dromaeosauridae, Euronychodon,div ersité. habitat insulaire. 87 ORYCTOS,Vol. 1, 1998 INTRODUCTION PREVIOUS REPORTS ON LATE CRETACEOUS THEROPOD DINOSAURS The vertebrate fauna of the Hateg Basin (Late FROM TRANSYLVANIA Cretaceous : Latest Maastrichtian; Antonescu et al 1983) was discoveredin 1895 and first describediÏ l- Megalosaurus hungaricus - a problematic and 1900 by Nopcsa. The fauna comes mostly from the misinterpreted theropod from Tbansylvania fluviatile, continental deposits of the Densus-Ciula Nopcsa (1901, cited by Le Læuff &, Buffetaut, and Sinpetru formations, cropping out in the north- 1991) erectedMegalosaurus hungaricu,son the basis western and central parts of the basin respectively of two (cf. Nopcsa, I9I5; contra Le Loeuff & (Grigorescu, 1992 : fig. 1). Isolated or associated Buffetaut, I99I) small, isolated teeth (MAFI Ob. remains of herbivorous dinosaurs (the titanosaurid 3106, not found in 1982; Weishampel, pers. comm.). sauropod Magyarosaurus dacus, the ornithopod of Megalosaurus hungaricus is currently regarded by uncertain affinities Rhabdodon robustus, the basal most authors (Le Læuff 8. Buffetaut, I99I; Le hadrosaurid Telmatosaurus transsylvanicus and the Loeuff, 1992) as an indeterminate theropod of (?) nodosaurid Struthiosaurus transilvanicus) are wides- Late Campanian Maastrichtian age. However, as pread, along with those of turtles and crocodilians. In Nopcsa ( 1915) noted, the teeth were found at contrast, the remains of the top predators (theropod Nagybâr1d (today Borod, Bihor County, Romania); dinosaurs) are very scarce, despite the intensive col- according to the label once accompanying the teeth, lecting effort conducted over two periods: the first they came from the "Gosau coal outcrops near two decades of the century by F. Nopcsa and in the Nagybfu6d locality". last two decades by teams from the Faculty of In the Borod basin, the Upper Cretaceous out- Geology and Geophysicsof the BucharestUniversity cropping rocks are represented by mostly detritic (FGGUB) led by D. Grigorescu and those of the deposits: sandstones and marls with interbedded Muzeul Civili zatiei Dacice si Romane, Deva microconglomerates and charophyte-bearing lacus- (MCDRD; formerly Deva County Museum); in the trine limestones, followed by a sandstone conglo- last four years fieldwork was done jointly with D. merate unit with rudist bivalve-bearittg limestones Weishampel from the Johns Hopkins University in and rudist reefs, a thin, discontinuoussandstone-silts- Baltimore, USA. tone unit with tuffits and rhyolitic tuffs; the Upper Cretaceous sequence ends with a marly unit with Inoceramlts (Mutihac & Ionesi, I97 4). In the eastern part of the outcropping area, the lower paft of these deposits laterally grade into a typical coal-bearing "Gosaufacies"(Ianovici et al., 1976;Mutihac, 1990). The whole sequencecan be characterized as a trans- gressive unit overlaying older deposits and the crys- talline basement of the Plopis Mts. (to the north); the deposition reflects changing paleoenvironmental conditions from nearshore continental-lacustrine and litoral environments to inner shelf ones. The deposits arehighly fossiliferrous. The basal,terrigenous depo- sits contain a fauna with Corbula striatula, Cardium subdinense, Turritella dupiniana, Melanopsis dubia and are considered of a Coniacian-early Santonian age (Ianovici et al., 1976). The overlying calcareous deposits yielded a rich association dominated by FIGURE 1 - The geographicalsetting of the Hateg Basin and suffounding regions. Hippurites praecursor, Vaccinites gosaviensis, U a - outcrop areaof the Sinpetru Formation; oppeli santonianus in the lower part (indicating alate b - outcrop areaof the Densus-CiulaFormation Santonian age) and Vaccinites oppeli, V archiaci, V 88 CSIKI & GRIGORESCU- ROMANIAN THEROPODS inequicostatus in the upper part (indicating an early part of a left tibiotarsus (BMNH A.4358, formerly Campanian age; Ianovici et al., I9J6). under the same specimen number as the femur); The Borod Senonian sequenceis diachronous in referred material includes another proximal femur its terminal part. In the eastern part of the outcrop (BMNH A.1235) and two more distal tibiotarsi area, the uppermost limestone deposits yielded (BMNH A.1588, A.1528). All the referred material Lepidorbitoides mamillata, L. minor Orbitoides gen- comes from the Sibisel Valley (Weishampel, pers. sanicus, an assemblage of late Campanian comm.), but no further details are known about their Maastrichtian age (op.cit.), while in the northern part precise locality or possible co-occurrence. the overlying marls yielded clams (Inoceramus balti- Subsequently,Harrison and Walker (1975) sepa- cus) and a micropaleontological association with rated the tibiotarsi and erected for them the new stri- Globotruncana lapparenti lapparenti, G. lapparenti giform bird genera Bradycneme draculae (A. 1588) bulloides, G. elevata elevata, G. bulloides, indicating and Heptasteornis andrewsi (A. 1528, A.4358). The an early Campanian age (Th. Neagu, pers. comm.). avian nature of all these remains were questioned by As M. hungaricus came from the "Gosau coal" numerous authors, who noted their reptilian (and (i.e.the lower, terrigenous part of the Senonian more exactly dinosaurian) affinity (ex. Elzanowski, sequence), although it may represent a (dwarf , cf . 1983; Grigorescu, I984a as "coelurosaurians"). Nopcsa, I9l5) theropod, it is more probably member Further suggestionswere made on their relationships of a stratigraphically