A New Rebbachisaurid Sauropod from the Isle of Wight.

Fig 1.- Reconstruction of Rebbachisaurus. 

Rebbachisaurids are a rather obscure and poorly understood group of sauropod dinosaurs so far known only from the Early Cretaceous period of Africa, South America and Europe. A new find described in an article by Philip D. Mannion, Paul Upchurch and Stephen Hutt in this month issue of Cretaceous Research confirms the presence of this group on the Isle of Wight during the Early Cretaceous. The paper reports of a an anterior caudal vertebra from the Wessex Formation of Barremian age, discovered at Brightstone Bay on the Southwest coast of this little Island of the English Channel. No species name has been assigned to the fossil.

The type genus of the Rebbachisaurids, Rebbachisaurus was a sauropod, big plant-eating dinosaur similar to the famed Diplodocus, and member of the Diplodocoidea superfamily. It lived during the Early Cretaceous in what is now North Africa. It was first described in 1954 by R. Lavocat from fragmentary remains, consisting of a tail vertebra, a humerus (upper arm bone), a scapula (shoulder blade) and a sacrum, and collected from the Tegana Formation of Morocco. The species name is Rebbachisaurus garasbae. In 1960, A.F. de Lapparent described a second species, R. tamesnensis from various fragments of the Farak Formation of Niger, but this one is a bit dubious and can well belong to a completely different sauropod. More complete material from the Rio Limay Formation of Argentina including a partial skull has been referred to a third species, R. tessonei (Calvo & Salgado, 1995), and was used as proof of a land connection between Africa and South America in the Early Cretaceous, but the species has since been transferred to its own genus, Limaysaurus. So as today, the only species referable with certainty to the genus Rebbachisaurus is the Moroccan one described by Lavocat.

Fig 2.- Nigersaurus taqueti.

However, several closely related taxa have been described since then, mostly from South America, and a family, the Rebbachisauridae, has been erected by P. Sereno and co-workers in 1999 to regroup them. Although only known from Cretaceous strata, they appear to be basal members of the Diplodocoidea and therefore more primitive than the earlier Diplodocus and Apatosaurus from the late Jurassic period, indicating "a ghost lineage" from the Middle to Late Jurassic. Besides Rebbachisaurus and Limaysaurus, the Rebbachisaurids include the odd sauropod Nigersaurus taqueti, known from several well-preserved skeletons from the “Middle” (Aptian-Albian) Cretaceous of Niger, and described in the media as the “dinosaur with a vacuum cleaner mouth”. From the ten or so Rebbachisaurid taxa named so far, only Limaysaurus and Nigersaurus are known from relatively complete materials. All the others are very fragmentary so it is difficult to get a complete picture of this enigmatic family. One characteristic and common trait of this clade is the paddle-shaped scapular blade.

Besides Africa and South America, Rebbachisaurids were also living in Europe. The species Histriasaurus boscarottii, has been erected based on a few vertebrae from the Early Cretaceous (Hauterivian-Barremian) of Croatia (Dalla Vecchia, 1998), the most ancient member of the family so far and some materials from the Castrillo de la Reina Formation (Barremian-Aptian) of Spain have been reported by Pereda Superbiola et al. in 2003 and recently described in details under the name Demandasaurus darwini by Fernández-Baldor et al., in 2011. Finally, rebbachisaurids are also known from the Isle of Wight of England. A characteristic scapula (shoulder blade) collected by Nick Case in 1989 from the Wessex Formation on the southwest coast of the Isle of Wight has been described by Philip Mannion in 2009. In a recent cladistic analysis by Carballido et al., (2010), this British scapula comes, oddly, as a sister taxon of the South American Limaysausus tessonei. It is possible that the newly described caudal vertebra does belong to the same animal, even if the phylogenetic analysis placed it in a close kinship with the Spanish Demandasaurus and the African Nigersaurus, rather than with Limaysaurus. However, conclusions based on single incomplete bones are probably not to be entirely trusted until new discoveries are added to the analysis.

Original artworks on Paleoexhibit are copyrighted to Nobu Tamura. Do not use without permission (Email: nobu dot tamura at yahoo dot com)

References:

J. O. Calvo and L. Salgado. 1995. Rebbachisaurus tessonei sp. nov. a new Sauropoda from the Albian-Cenomanian of Argentina; new evidence on the origin of the Diplodocidae. GAIA 11:13-33.

J. L. Carballido, A. C. Garrido, J. L. Canudo and L. Salgado. 2010. Redescription of Rayososaurus agrioensis Bonaparte (Sauropoda, Diplodocoidea), a rebbachisaurid from the early Late Cretaceous of Neuquén. Geobios 43:493-503.

F. M. Dalla Vecchia. 1998. Remains of Sauropoda (Reptilia, Saurischia) in the Lower Cretaceous (Upper Hauterivian/Lower Barremian) limestones of SW Istria (Croatia). Geologica Croatica 51(2):105-134.

F. Torcida Fernández-Baldor, J. I. Canudo, P. Huerta, D. Montero, X. Pereda Suberbiola and L. Salgado. 2011. Demandasaurus darwini, a new rebbachisaurid sauropod from the Early Cretaceous of the Iberian Peninsula. Acta Palaeontologica Polonica 56(3):535-552

A. F. d. Lapparent. 1960. Les Dinosauriens du "Continental intercalaire" du Saharal central [The dinosaurs of the "Continental Intercalaire" of the central Sahara]. Mémoires de la Société géologique de France, nouvelle série 39(88A):1-57

R. Lavocat. 1954. Sur les dinosauriens du Continental Intercalaire des Kem-Kem de la Daoura [On the dinosaurs from the Continental Intercalaire of the Kem Kem of the Doura]. Comptes Rendus 19th Intenational Geological Congress, 1952 1:65-68.

P. D. Mannion. 2009. A rebbachisaurid sauropod from the Lower Cretaceous of the Isle of Wight, England. Cretaceous Research 30:521-526.

P. D. Mannion, P. Upchurch, and S. Hutt. 2011. New rebbachisaurid (Dinosauria: Sauropoda) material from the Wessex Formation (Barremian, Early Cretaceous), Isle of Wight, United Kingdom. Cretaceous Research 32:774-780

X. Pereda Suberbiola, F. Torcida, L. A. Izquierdo, P. Huerta, D. Montero and G. Pérez. 2003. First rebbachisaurid dinosaur (Sauropoda, Diplodocoidea) from the early Cretaceous of Spain: palaeobiogeographical implications. Bulletin de la Societé Géologique de France 2003(5):471-479

L. Salgado, A. Garrido, S. E. Cocca and J. R. Cocca. 2004. Lower Cretaceous rebbachisaurid sauropods from Cerro Aguada del León (Lohan Cura Formation), Neuquén province, northwestern Patagonia, Argentina. Journal of Vertebrate Paleontology 24(4):903-912.

P. C. Sereno, A. L. Beck, D. B. Dutheil, H. C. E. Larsson, G. H. Lyon, B. Moussa, R. W. Sadleir, C. A. Sidor, D. J. Varricchio, G. P. Wilson, and J. A. Wilson. 1999. Cretaceous sauropods from the Sahara and the uneven rate of skeletal evolution among dinosaurs. Science 286:1342-1347.