Andesaurus delgadoi - revised

FORGOTTEN GIANTS: species #3 - Andesaurus delgadoi

*Now revised with more accurate speculative sacrals, new tail data from Mannion and Calvo (2011) and re-scaled.* The previous version was far too big at 30m (100ft.), a bogus figure which has been published many times over in commercial dinosaur books. Based on a careful re-analysis of the fossil measurements, Andesaurus was probably only 61ft. (18.5m) long, at least for the type (and currently only) specimen. The only way this animal could be longer is if it had a crazy-long neck for its size (which isn't out of the ballpark if you consider Phuwiangosaurus, which was almost a titanosaur...) However due to lack of shoulder material, the maturity of the type specimen is unknown, and it's possible this creature might have grown a lot bigger.

This restoration is also the basis of an amazing new 3D model by MrGorsh fav.me/d4yyhje which shows how even relatively slender titanosaurs could be bulky.

Location: El Chocón, Argentina (Río Limay Formation)
Time: Albian-Cenomanian epochs (transition from Early to Late Cretaceous)
Length: 61ft. (18.5m), perhaps more depending on maturity and neck proportions
Probable mass: ~20 tons
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The midsize basal titanosaur Andesaurus delgadoi, fully restored in hi-fi profile and frontal views for the FIRST TIME ever. The skeletal art is also the first ever done for this species.

Andesaurus was described in 1991, but since then very little research has been done on it. It's the founding member of the family Andesauridae, one of the most primitive families of titanosaurs - yet despite being the namesake of the dubious family that once contained its famed contemporary Argentinosaurus, it's obscure and still not well-understood. It was long-bodied, with tall neural spines on its back (which was probably close to horizontal) and very robust hips. It's not an extreme design for a titanosaur - its elegance lies in its subtlety. This animal was the forerunner of all subsequent titanosaur body designs. It's classed as the most primitve true titanosaur in most scientific papers and cladistic analyses, though that distinction likely belongs to a much earlier animal, perhaps Janenschia.

Despite being only a medium-sized sauropod, Andesaurus has often been labeled in books and on websites as a colossus verging on 30m long. In reality, the bones indicate a far smaller animal, and are dwarfed by those of real 100+ footers like Argentinosaurus and Puertasaurus.

Missing bones whose shapes can be reasonably well-approximated are shaded, I did not figure speculative neck bones since we literally have no clue what they would have looked like. Skeletal and accompanying diagrams of specific vertebrae are based on photographs of the fossils and on scale diagrams in Salgado et. al. 1997 and Mannion and Calvo, 2011.

References:

Calvo, J.O. & Bonaparte, J.F. 1991. Andesaurus delgadoi nov. gen. et nov. sp. (Saurischia, Sauropoda) a titanosaurid dinosaur from the Río Limay Formation (Albian-Cenomanian), Neuquén, Argentina.] Ameghiniana. 28: 303-310. [In Spanish]

Mannion, P.D. & Calvo, J.O. 2011. Anatomy of the basal titanosaur (Dinosauria, Sauropoda) Andesaurus delgadoi from the mid-Cretaceous (Albian–early Cenomanian) Río Limay Formation, Neuquén Province, Argentina: implications for titanosaur systematics. Zoological Journal of the Linnean Society onlinelibrary.wiley.com/doi/10…