Rebbachisaurus (meaning "Aït Rebbach lizard") is a genus of sauropod dinosaur that lived in what is now Africa during the Late Cretaceous period, between 99 and 97 million years ago. The only valid species is R. garasbae. However, two other species have been assigned to the genus; R. tessonei, now Limaysaurus tessonei, and the nomen dubium R. tamesnensis. Known from a single, incomplete skeleton, much of R. garasbae's anatomy is unknown. The skeleton, discovered in 1948, was unearthed in the Errachidia Province of Morocco from strata of the Kem Kem Beds.
Like other rebbachisaurids, Rebbachisaurus was a four-legged herbivore with a long neck ending in a relatively large head. Although once thought to be as long as in length, more recent estimates place it at long and weighing . This would make it among the largest known rebbachisaurids. Its dorsal vertebrae are characterized by their tall and large , which held extensive air sacs. Its vertebrae are very tall and reach up to tall, while those of South American rebbachisaurids get to only around . Its humerus is somewhat robust for a rebbachisaurid, with an estimated complete length of and a greatly expanded proximal (towards body) end.
Rebbachisaurus is the type genus of the family Rebbachisauridae, though its exact relation to other members is uncertain. Being a rebbachisaurid, Rebbachisaurus was likely a generalist or ground-height browser. Many gigantic theropods are known from North Africa during this period, including Carcharodontosaurus, Spinosaurus, and Deltadromeus, while Rebbachisaurus is the only named sauropod from the Kem Kem Beds. North Africa at the time was blanketed in mangrove forests and wetlands, creating a hotspot of fish, crocodyliform, and pterosaur diversity
Discovery and species Fossils assigned to Rebbachisaurus were first discovered in the Gara Sbaa locality in Errachidia Province, southeastern Morocco between 8 October 1948 and 1 April 1949 by French paleontologist René Lavocat. Lavocat was on his second expedition to the Cretaceous-aged outcrops of the "Continental intercalaire" of the Sahara Desert, which was then under French colonial administration. Over two additional expeditions, researchers recovered a fragmentary, partially articulated skeleton. It included a complete posterior (towards back) (backbone), fragments from four dorsal , two damaged dorsal neural spines, dorsal rib shaft fragments, fused neural spines from two and an incomplete neural spine of a third, two (tail vertebrae) neural spines, the right (shoulder blade), the right humerus (upper arm bone), the right ischium (back lower pelvic bone), and many neural spine fragments. However, the specimen initially included six caudal vertebrae in articulation, two of which have been missing, the sacrum, and much of the ribs. By 3 January 1952, the last of the four expeditions to recover the fossils had concluded and the specimen was then brought to the National Museum of Natural History in Paris where it was deposited under specimen number MNHN-MRS 1958. The locality which MNHN-MRS 1958 was found in was later assigned to the Gara Sbaa Formation of the Kem Kem Beds, indicating it dates to the Cenomanian-Albian ages of the middle Cretaceous period.
In 1954, Lavocat scientifically described the remains and assigned them to a new genus and species of sauropod, which he named Rebbachisaurus garasbae.Lavocat, R. (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 Doaura). Comptes Rendus 19th International Geological Congress 1952 1: 65-68. Rebbachisaurus is considered his most famous discovery. Additionally, MNHN-MRS 1958 is the only associated vertebrate skeleton known from the Gara Sbaa Formation and one of only two articulated vertebrate skeletons known from the entire Kem Kem Beds, the other one being the holotype of the enigmatic theropod Deltadromeus. The generic name is a combination of the word Rebbach, in reference to "le territoire des Aït Rebbach", and the Greek word sauros meaning "lizard". "Aït Rebbach" is likely in allusion to the Khebbash tribe, a seminomadic Berber Ait Atta tribe which resisted French occupation during the Pacification of Morocco. The specific name garasbae derives from the Gara Sbaa site where the holotype was unearthed. While Lavocat's description was brief and only figured the scapula and dorsal vertebra, American paleontologist Jeffrey A . Wilson and French paleontologist Ronan Allain described the specimen in more detail in 2015.
In 1996, Canadian paleontologist Dale Russell assigned an isolated posterior dorsal , several isolated teeth, and a (neck) neural spine, all of which had been found by Moroccan fossil hunters in the Kem Kem Beds, to R. garasbae. Although the centrum is still assigned to R. garasbae, the teeth and cervical neural spine cannot be compared with the holotype due to lack of overlap. This led Wilson and Allain (2015) to exclude these fossils from the R. garasbae hypodigm (all of the available specimens that a researcher assigns to a specific species). Several caudal vertebrae and an isolated dorsal vertebra from the Kem Kem Beds have been assigned to R. garasbae, however their statuses are indeterminate according to Wilson and Allain (2015) and cannot be confidently assigned to the species. Additionally, an isolated tooth, MNHN-MRS 1524a, was discovered by Lavocat on an expedition to the Kem Kem Beds, though its exact geographic and geologic origins are unknown. It has been assigned to R. garasbae, though Wilson and Allain (2015) opted not to include it in the R. garasbae hypodigm because of a lack of overlap and the presence of a second, distinct sauropod in the Kem Kem Beds. In a 2020 monograph on the Kem Kem Beds, German-Moroccan paleontologist Nizar Ibrahim and colleagues described an isolated rebbachisaurid tooth that had been found in the Aferdou N’Chaft, which corresponds to the Douira Formation of the Kem Kem Beds. Although coming from a different formation, Ibrahim and colleagues (2020) stated it may come from Rebbachisaurus or a narrow-toothed titanosaurid.
Formerly assigned species R. tamesnensis Between 1946 and 1959, nine expeditions were mounted to explore Cretaceous-aged outcrops of the Continental Intercalaire Formation. In 1960, French paleontologist Albert de Lapparent described a new species of Rebbachisaurus, R. tamesnensis, supposedly on the basis of two humeri and two femora, but he failed to pick a holotype specimen. This specimen was unearthed from the Gall locality, an outcrop of the Jurassic-aged Tiourarén Formation in Niger. The material assigned to R. tamesnensis also included four isolated teeth, a dentary fragment with three teeth, over 100 vertebrae, six chevrons, twelve ribs, five scapulae, an ilium, two ischia, and numerous limb elements. The material of this taxon was collected from multiple localities across the Sahara, such as several sites in the Elrhaz Formation of Niger, and its referral to one species was not justified by Lapparent.de Lapparent A. F. (1960) "The dinosaurs of the "Continental Intercalaire" of the central Sahara". Memoirs of the Geological Society of France 39: 1-60. In 1995, Argentine paleontologists Jorge Calvo and Leonardo Salgado stated that R. tamesnensis was not a species or even a diplodocoid, but instead a camarasaurid based on its spatulate teeth, distally expanded ischium, and the presence of a hyposphene-hypantrum in the dorsal vertebrae. This was also proposed by American paleontologist John C. McIntosh in a 1990 issue of The Dinosauria. However, in 2009 British paleontologist Philip D. Mannion hypothesized that R. tamesnensis was actually a chimera (a species named based on fossils of several different species) of Jobaria and Nigersaurus fossils, which was supported by other studies.
In 2025, Mannion and American paleontologist Andrew J. Moore analyzed the material of R. tamesnensis and found that only one specimen, an anterior (towards front) caudal vertebra that Lapparent had identified as a dorsal vertebra, bore rebbachisaurid synapomorphies. This fossil was collected from the Djoua Valley of Algeria in an outcrop likely deriving from the Gara Samani Formation. It lacks overlap with any specimens of R. garasbae, though it is comparable to an isolated rebbachisaurid vertebra that had been found in the Kem Kem Beds. Additionally, their study stated that R. tamesnensis is an indeterminate rebbachisaurine and a nomen dubium.
R. tessonei In 1988, a well-preserved sauropod skeleton including much of the posterior region of the skull and postcranial material was unearthed from a locality of the Cenomanian-aged Candeleros Formation in Neuquén Province, Patagonia, Argentina. This skeleton was made the holotype of a new species of Rebbachisaurus, R. tessonei, by Argentine paleontologists Jorge Calvo and Leonardo Salgado in 1995. However, in 2004 Salgado and colleagues placed R. tessonei in its own genus, Limaysaurus.Salgado, L., Garrido, A., Cocca, S. E., and Cocca, J. R. (2004). "Lower Cretaceous rebbachisaurid sauropods from Cerro Aguada Del León, Neuquén Province, northwestern Patagonia, Argentina." Journal of Vertebrate Paleontology, 24(4): 903-912, December 2004.
Description
Rebbachisaurus is a medium-sized sauropod, though it is among the largest rebbachisaurids known. Previous studies estimated Rebbachisaurus was around long,Upchurch, P., Mannion, P. D, & Barrett, P. M. (2011b). Sauropod dinosaurs. In: Batten, D. J., Ed.), Field Guide to English Wealden Fossils. Palaeontological Association, London, 476–525. comparable in size to Apatosaurus. Recent studies state that Rebbachisaurus was around long and weighed . Being a rebbachisaurid sauropod, Rebbachisaurus likely possessed a relatively short neck and long tail, tall neural spines, highly pneumatised (air containing) skeleton, robust limbs, longer hindlimbs than forelimbs, long, thin teeth, and possibly a highly specialized skull, like Nigersaurus. Only one dorsal vertebra from the holotype is relatively complete. Its estimated total height is , as it is missing the distal most 5% of its length. This makes it significantly taller than those observed in South American rebbachisaurids, which are only around in height. The centrum is relatively small, making up only 1/5 of the total height. Likewise the neural canal (a gap in the vertebra for the spinal cord to travel through) is small relative to the vertebral height, whereas the (projections of vertebrae that connect to others in the vertebral column) and the neural spines are very tall relatively. The (area running between the , projections of bone that articulate with the (top head) of the rib) region of the (the posterior bony projection that encloses the spinal cord) is blanketed in a complex web of (ridges on vertebrae that divide pneumatic chambers), many of which have features unique to the genus. The condyle (a protuberance at the anterior end of the centrum) is concave but extends only from the condylar rim (where the condyle ends and the rest of the vertebra starts). Its lower portion is much flatter than its top portion, which projects strongly dorsally (from the top), like in the condyles of Diplodocus, Apatosaurus, and Haplocanthosaurus. In contrast, the condyles of macronarians are strongly convex while those of non-neosauropods are flat. As for its proportions, the centrum measures in length, in height, and in width, resulting in nearly subequal lengths and a square shape. Its centrum is (anteriorly convex and posteriorly concave) with large, subtriangular (large fossae on the lateral (side) faces of centra), which held extensive air sacs. Rebbachisaurus is unique amongst sauropods in that the infrazygapophyseal region of the neural arch is subequal in height to the centrum.