VII Jornadas Internaciones sobre Paleontología de Dinosaurios y su Entorno. Salas de los Infantes, Burgos The Gondwanan rhabdodontomorphans and the origins of the Rhabdodontidae DIEUDONNÉ, P.E.1, TORTOSA, T.2, DÍAZ‐MARTÍNEZ, I.3, RUIZ‐OMEÑACA, J.I.1, TORCIDA FERNÁNDEZ‐BALDOR, F.4, CANUDO, J.I.1 1 Grupo Aragosaurus−IUCA, Área de Paleontología, Facultad de Ciencias, Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain, [email protected], [email protected], [email protected] 2 Réserve Naturelle Nationale Sainte‐Victoire, Conseil Départemental des Bouches‐du‐Rhône, 52 Avenue de Saint‐Just, 13256 Marseille Cedex 20, France, [email protected] 3 CONICET—Instituto de Investigación en Paleobiología y Geología, Universidad Nacional de Río Negro, General Roca 1242, 8332 Fisque Menuco, General Roca, Argentina, [email protected] 4 Museo de Dinosaurios de Salas de los Infantes and Colectivo Arqueológico−Paleontológico Salense (CAS), Plaza Jesús Aparicio 9, 09600 Salas de los Infantes, Burgos, Spain. [email protected] Keywords: Gondwana, Rhabdodontomorpha, Rhabdodontidae, synapomorphies The fossil record of small bipedal ornithopods is almost invisible at the beginning of the Cretaceous in Western Europe. However, an increasing number of sites record basal ornithopod remains from the Barremian onwards. Examples are reported from England (Galton, 1974), France (Néraudeau et al., 2012) and Spain (Ruiz‐Omeñaca et al., 1995; 2012; Rauhut, 2002). This increment in diversity is particularly significant by observing the teeth, of which a minority bears a distinct “rhabdomorphan” morphology (e.g. Canudo et al., 2010). However, no post‐cranial skeleton has ever been described in association with these teeth. Incomplete and disarticulated remains from at least five small‐bodied ornithopods of three distinct ontogenetic stages were collected at the Vegagete dig‐site. This material comes from the Barremian‐Albian of the Castrillo de la Reina Formation (Dieudonné et al., 2016 and references herein). The Vegagete taxon appears to bear some very surprising characters which ・ despite its slender and gracile appearance place it as the most primitive member of Rhabdodontidae (Dieudonné et al., 2016). This clade was recently diagnosed by three forearm synapomorphies: 1) a humerus lacking a bicipital sulcus, 2) a humerus of which the lateral side is concave between the head and the deltopectoral crest, and 3) a prominent olecranon process on the ulna (Dieudonné et al., 2016). The presence of a comparatively larger primary ridge on the dentary teeth is very probable, though its greater prominence should be verified in more primitive ornithopods. A crest‐ like fourth trochanter is very likely present, but this process is broken in the Vegagete ornithopod, so this apomorphy could not be assessed at the base of the clade. The informal group “Rhabdomorpha” was recently redefined and renamed within the new superfamily “Rhabdodontomorpha” (Dieudonné et al., 2016), which contrary to previous conceptions (Ruiz‐Omeñaca, 2001; Pincemaille, 2002) excludes any relation with the American genus Tenontosaurus and strengthens the kinship of Rhabdodontidae with the Australian ornithopod Muttaburrasaurus. Their synapomorphies are 1) a subrectangular maxillary process of 65 VII Jornadas Internaciones sobre Paleontología de Dinosaurios y su Entorno. Salas de los Infantes, Burgos the jugal (Fig. 1A, B, C); 2) a strongly bowed humerus in antero‐posterior view; 3) a significant lateral deflection of the preacetabular process (Fig. 2A, C); 4) the dorsal margin of the preacetabular process is transversely expanded to form a narrow shelf (Fig. 2A, 2C); 5) the dorsal margin of the ilium is mediolaterally thickened above its ischiac peduncle (Fig. 2A, 2C). A combined character that could be plesiomorphic is a femur that has a non‐constricted trochanteric fossa. Leaellynasaura amicagraphica is made a member of this group by the anterior maxillary process of its jugal bearing parallel superior and inferior borders (Herne, 2013, fig 5.41, Fig. 1B), and the combined presence of a femur which has a shallow trochanteric fossa (Rich & Vickers Rich, 1989, fig. 6, 7). Figure 1: Rhabdodontomorphan synapomorphies. Left reconstruction of the skull of Muttaburrasaurus langdoni (1A) (Bartholomai & Molnar, 1981, fig. 2A), Leaellynasaura amicagraphica (1B) (Herne, 2013, fig. 5.41), and left lateral view of the jugal of Zalmoxes robustus (1C) (Weishampel et al., 2003, fig. 6A). Right ilia of M. langdoni (2A) (photo courtesy of M. Herne) and Zalmoxes shqiperorum (2C) (Godefroit et al., 2009, fig. 18C, D) in dorsal (above) and lateral (below) views; left ilium of the Vegagete ornithopod in posterior view (2B). Right metatarsal I of Hypsilophodon foxii (3A, Galton, 1974, fig. 58A), Tenontosaurus tilleti (3B, Forster, 1990, fig. 22B), Camptosaurus dispar (3C, left reversed, USNM 5473), the Vegagete ornithopod (3D), and Rhabdodon sp. (3E, Chanthasit, 2010, fig. 4.34A) in anterior (3A‐C, 3D to the left), posterior (3D to the right), and medial (3E) views. Abbreviations: mpj, maxillary process of jugal; mlth, 66 VII Jornadas Internaciones sobre Paleontología de Dinosaurios y su Entorno. Salas de los Infantes, Burgos mediolateral thickening above the ischiac peduncle on the dorsal margin of the ilium; ppsh, preacetabular process shelf. Scales: 10cm (1A, 2A), 1cm (1B), 5mm (2B, 3D), 5cm (1C, 2C, 3A‐C, 3E). Unexpectedly, the distal end of the first metatarsal appears to bear one character which could be plesiomorphical for the rhabdodontids, the origins of which may lie amongst Gondwanan ornithopods. In the Vegagete ornithopod (MDS‐VG,171, Fig. 3D), and possibly too in Rhabdodon sp. based on illustrations (MDE‐C3.510, Fig. 3E) the distal ligamentary fossae of the first metatarsal are oriented antero‐posteriorly, with the plantar posterior surface laid laterally against the second metatarsal. A “planto‐lateral” orientation was also described for the Early Cretaceous Australian ornithopod VOPC III (MV P221080, see Herne, 2013 to fig. 10.18B). This configuration largely contrasts with the usual planto‐posterior orientation observed in most other ornithischians (e.g. in Galton, 1974; Galton et al., 2015; Forster, 1990, Fig. 3A‐C). Evidence points towards an affinity between the rhabdodontids and a very specific – yet very diverse – group of southeastern Gondwanan ornithopods that comprise Muttaburrasaurus and Leaellynasaura. All of these taxa are grouped together into the Rhabdodontomorpha. It is worth noting that this superfamily includes taxa that are very distant both temporally and spatially. What is more, rhabdodontomorphan remains are rather incomplete. As a consequence, it is not surprising that still very few synapomorphies could be attributed to this group for the moment. References Canudo J.I., Gasca J.M., Aurell M., Badiola A., Blain H.A., Cruzado‐Caballero P., Gómez‐ Fernández D., Moreno‐Azanza M., Parrilla J., Rabal‐Garcés R., Ruiz‐Omeñaca J.I. (2010): La Cantalera: An exceptional window onto the vertebrate biodiversity of the Hauterivian‐Barremian transition in the Iberian Peninsula. Journal of Iberian Geology, (36, 2), 205‐224. Chanthasit P. (2010): The ornithopod dinosaur Rhabdodon from the Late Cretaceous of France: anatomy, systematics and paleobiology. Unpublished PhD Thesis, Université Claude Bernard, Lyon, 195 pp. Dieudonné P.E., Tortosa T., Torcida Fernández‐Baldor F., Canudo J.I., Díaz‐Martínez J.I. (2016): An unexpected early rhabdodontid from Europe (Lower Cretaceous of Salas de los Infantes, Burgos province, Spain) and a re‐ examination of basal Iguanodontian relationships. PLoS ONE, (11,6), e0156251. Forster C.A. (1990): The postcranial skeleton of the ornithopod dinosaur Tenontosaurus tilletti. Journal of Vertebrate Paleontology, (10, 3), 273‐94. Galton P.M. (1974): The ornithischian dinosaur Hypsilophodon from the Wealden of the Isle of Wight. Bulletin of the British Museum (Natural History), Geology Series, (25,1), 3‐152. Galton, P.M., Carpenter, K., Dalman, S.G. (2015): The holotype pes of the Morrison dinosaur Camptonotus amplus MARSH, 1879 (Upper Jurassic, western USA) – is it Camptosaurus, Sauropoda or Allosaurus? Neues Jahrbuch für Geologie und Paläontologie‐Abhandlungen, (275,3), 317‐335. Godefroit P., Codrea V., Weishampel D.B. (2009): Osteology of Zalmoxes shqiperorum (Dinosauria, Ornithopoda), based on new specimens from the Upper Cretaceous of Nălaţ‐Vad (Romania). Geodiversitas, (31,3), 525‐53. Herne M.C. (2013): Anatomy, systematics and phylogenetic relationships of the Early Cretaceous ornithopod dinosaurs of the Australian‐Antarctic rift system. Unpublished PhD Thesis, University of Tasmania, Murdoch University. Néraudeau D., Allain R., Ballevre M., Batten D.J., Buffetaut E., Colin J.P, (2012): The Hauterivian‐Barremian lignitic bone bed of Angeac (Charente, south‐west France): stratigraphical, palaeobiological and palaeogeographical implications. Cretaceous Research, (37), 1‐14. 67 VII Jornadas Internaciones sobre Paleontología de Dinosaurios y su Entorno. Salas de los Infantes, Burgos Pincemaille‐Quillevere M. (2002): Description d'un squelette partiel de Rhabdodon priscus (Euornithopoda) du Crétacé supérieur de Vitrolles (Bouches du Rhône, France). Oryctos, (4), 39‐70. Rauhut O.W.M. (2002): Dinosaur teeth from the Barremian of Uña, Province of Cuenca, Spain. Cretaceous Research, (23), 255‐263. Rich T.H.V., Vickers Rich, P. (1989): Polar dinosaurs and biotas of the Early Cretaceous of southeastern Australia. National Geographic Research,