Your Friends The Titanosaurs, part 31.5: Garrigatitan meridionalis

Santa brought along one more titanosaur to place under the tree. It's not a super-titanosaur, although it still probably wouldn't fit too comfortably in your house. Welcome Garrigatitan meridionalis, joining us from the late Campanian of southern France.

Unrelated: Rare miniature boreal sauropods. This unnamed taxon is also notable for its unusual osteoderms and short tail with well-developed caudofemoralis muscles.

Genus and Species: Garrigatitan meridionalis. The genus name is derived from the Occitan "garriga" ("garrigue" in French), which in turn comes from the Provencal "garric", in reference to the "typically Mediterranean low vegetation composed mainly of drought-resistant shrubs which is abundant in the environment of the Velaux-La Bastide Neuve locality" (Díez Díaz et al. 2020). The species name is the Latin word "meridionalis", which means "southern", in this case referring to southern France (Díez Díaz et al. 2020). Together we get something meaning roughly "southern garric titan", or, taking a bit of liberty, "garric titan of southern France".

Citation: Díez Díaz, V., G. Garcia, X. Pereda Suberbiola, B. Jentgen-Ceschino, K. Stein, P. Godefroit, and X. Valentin. 2020. A new titanosaur (Dinosauria: Sauropoda) from the Upper Cretaceous of Velaux-La-Bastide Neuve (southern France). Historical Biology (advance online publication). doi:10.1080/08912963.2020.1841184. (Thank you to Verónica Díez Díaz for sending me a copy!)

Stratigraphy and Geography: G. meridionalis comes from the La Bastide Neuve locality which also yielded Atsinganosaurus velauciensis and Matheronodon provincialis. To reiterate, this site is located near Velaux in the Aix-en-Provence Basin, within the Bouches-du-Rhône Department of Provence-Alpes-Côte d'Azur, southeastern France. Geologically, the site is described as "Begudian" (local stage) sandstones of late Campanian age (Díez Díaz et al. 2020). There is at least one instance in print of the stratigraphy being described as the Argiles et Grès à Reptiles Formation, in the abstract of Díez Díaz et al. (2018), but the "Begudian" sandstones description is definitely preferred in various publications (Garcia et al. 2010; Cincotta et al. 2015; Godefroit et al. 2017; Díez Díaz et al. 2018, 2020).

Holotype: MMS/VBN.09.170 (Musée Moulin Seigneurial, Velaux-La Bastide Neuve specimens, Velaux), a sacrum and partial left ilium (Díez Díaz et al. 2020).

The La Bastide Neuve site includes nine vertical sequences made up of five facies of a fluvial (river) depositional system. Fossil bones were found low in sequences 1, 2, and 3 (the sequences are numbered 0 to 8 rather than 1 to 9). Most of them were found in sequence 2, which hosts a bonebed including remains of sharks, turtles, crocs, pterosaurs, theropods, titanosaurs, and ornithopods (Cincotta et al. 2015). The type specimen of G. meridionalis comes from level B3 in sequence 2, while most material referred to it comes from B2, although there isn't much stratigraphic separation (sequence 2 being about 1 m or 3 ft thick) (Díez Díaz et al. 2020). The position of the type in the bonebed is marked in figure 1B in the earlier publication Díez Díaz et al. (2018), in the upper right; look for "170". This does lead me to a somewhat discordant note: it seems like Atsinganosaurus is becoming less and less together. In the description of Atsinganosaurus, "the bones were recovered in partial anatomical connexion" (Garcia et al. 2010), whereas in this article, "It is important to state that none of the titanosaurian remains recovered from sequence 2 were found in articulation or association" except for the four dorsal vertebrae making up the type of Atsinganosaurus (Díez Díaz et al. 2020). With this information, and the demonstrated presence of two titanosaur species, it does make me somewhat nervous about specimen attribution. The specimens separated as G. meridionalis are distinct from those assigned to Atsinganosaurus, but in the absence of clear association of the Atsinganosaurus material, is it possible that some of the bones placed in one belong to the other? I guess that's what comes of dealing with too many "von Huene's puzzles". (You know, there really ought to be a way to distinguish individuals in a bonebed, some kind of stable isotope or histological fingerprinting. I assume it would be impractically expensive, though.)

I mentioned additional specimens. Díez Díaz et al. (2020) also referred a cervical vertebra, two humeri, a left ilium, and a right ischium to the new species, and more tentatively attributed a cervical rib, another humerus, a right ulna, and a femur to it. These four tentatively attributed bones are all noticeably larger than the more confidently attributed bones, but are not Atsinganosaurus. Díez Díaz et al. (2020) preferred to regard them as specimens of large G. meridionalis individuals rather than a third taxon. In the phylogenetic analysis, G. meridionalis was found to be the sister taxon to Ampelosaurus atacis within Lirainosaurinae (Díez Díaz et al. 2020). It is possible that some of the Bellevue material attributed to Ampelosaurus is actually the similar Garrigatitan (Díez Díaz et al. 2020).

There is something odd going on ontogenetically. The three humeri and femur were sectioned for histological study. All four were found to be at the upper end of growth (histologic ontogenetic stages [HOS] 12 to 14). One of the humeri, the one tentatively referred to the species (MMS/VBN.12.82) is substantially larger than the other two humeri while being of an equivalent HOS (approximately 700 mm long [or 28 in] versus 487 and 585 mm long [or 19.2 and 23.0 in]). Using the other two humeri and the femur, the body size of these approximately adult specimens was calculated as between 4.37 and 5.31 m long (14.3 to 17.4 ft), and 1.85 to 2.45 metric tons in mass (2.04 to 2.70 US tons) (Díez Díaz et al. 2020). If the large humerus is also G. meridionalis, this may imply sexual dimorphism or some kind of pathology (Díez Díaz et al. 2020). There is also an even larger ulna, approximately 66 cm long (26 in), making it the largest titanosaurian ulna from Europe. This ulna indicates an animal the size of Diamantinasaurus, around 12 to 16 m long (39 to 52 ft) (Díez Díaz et al. 2020). Of course, I have not been there and seen the material, but with the evidence of the more-or-less adult small-bodied individuals, I'm admittedly suspicious that there *is* a third, larger taxon. Another possibility is that G. meridionalis had proportionally long forearms. (Or, hey, in the realm of very-very-difficult-to-prove, this is a Mammuthus columbi/Mammuthus exilis situation, and we're seeing a larger individual from a larger landmass within a smaller-bodied population.)

References

Cincotta, A., J. Yans, P. Godefroit, G. Garcia, J. Dejax, M. Benammi, S. Amico, and X. Valentin. 2015. Integrated paleoenvironmental reconstruction and taphonomy of a unique Upper Cretaceous vertebrate-bearing locality (Velaux, southeastern France). PLoS ONE 10(8):e0134231. doi:10.1371/journal.pone.0134231.

Díez Díaz, V., G. Garcia, X. Pereda Suberbiola, B. Jentgen-Ceschino, K. Stein, P. Godefroit, and X. Valentin. 2018. The titanosaurian dinosaur Atsinganosaurus velauciensis (Sauropoda) from the Upper Cretaceous of southern France: new material, phylogenetic affinities, and palaeobiogeographical implications. Cretaceous Research 91:429–456. doi:10.1016/j.cretres.2018.06.015.

Díez Díaz, V., G. Garcia, X. Pereda Suberbiola, B. Jentgen-Ceschino, K. Stein, P. Godefroit, and X. Valentin. 2020. A new titanosaur (Dinosauria: Sauropoda) from the Upper Cretaceous of Velaux-La-Bastide Neuve (southern France). Historical Biology (advance online publication). doi:10.1080/08912963.2020.1841184.

Garcia, G., S. Amico, F. Fournier, E. Thouand, and X. Valentin. 2010. A new titanosaur genus (Dinosauria, Sauropoda) from the Late Cretaceous of southern France and its paleobiogeographic implications. Bulletin de la Societe Geologique de France 181(3):269–277.

Godefroit, P., G. Garcia, B. Gomez, K. Stein, A. Cincotta, U. Lefèvre, and X. Valentin. 2017. Extreme tooth enlargement in a new Late Cretaceous rhabdodontid dinosaur from southern France. Scientific Reports 7:13098. doi:10.1038/s41598-017-13160-2.