page_title: Argentinosaurus
section_title: Vertebrae
hierarchical_section_title: Argentinosaurus / Description / Vertebrae
caption_attribution_description: English: Argentinosaurus dorsal vertebra cast, with Matt Wedel. LACM
context_page_description: Argentinosaurus is a genus of giant sauropod dinosaur that lived during the Late Cretaceous period in what is now Argentina. Although it is only known from fragmentary remains, Argentinosaurus is one of the largest-known land animals of all time, if not the largest, with length estimates ranging from 30 to 39.7 metres and weight estimates from 50 to 100 tonnes. It was a member of Titanosauria, the dominant group of sauropods during the Cretaceous.
  The first Argentinosaurus bone was discovered in 1987 by a farmer on his farm near the city of Plaza Huincul. A scientific excavation of the site led by the Argentine palaeontologist José Bonaparte was conducted in 1989, yielding several back vertebrae and parts of a sacrum—fused vertebrae between the back and tail vertebrae. Additional specimens include a complete femur and the shaft of another. Argentinosaurus was named by Bonaparte and the Argentine palaeontologist Rodolfo Coria in 1993; it contains a single species, A. huinculensis. The generic name Argentinosaurus means "Argentine lizard", and the specific name huinculensis refers to its place of discovery, Plaza Huincul.
context_section_description: Argentinosaurus likely possessed 10 dorsal vertebrae, like other titanosaurs. The vertebrae were enormous  even for sauropods; one dorsal vertebra has a reconstructed height of 159 centimetres (63 in) and a width of 129 centimetres (51 in), and the vertebral centra are up to 57 centimetres (22 in) in width. In 2019, Paul estimated the total length of the dorsal vertebral column at 447 centimetres (176 in) and the width of the pelvis at 0.6 times the combined length of the dorsal and sacral vertebral column. The dorsals were opisthocoelous (concave at the rear) as in other macronarian sauropods. The pleurocoels (excavations on the sides of the centra) were proportionally small and positioned in the front half of the centrum. The vertebrae were internally lightened by a complex pattern of numerous air-filled chambers. Such camellate bone is, among sauropods, especially pronounced in the largest and longest-necked species. In both the dorsal and sacral vertebrae, very large cavities measuring 4 to 6 centimetres (1.6 to 2.4 in) were present. The dorsal ribs were tubular and cylindrical in shape, in contrast to other titanosaurs. Bonaparte and Coria, in their 1993 description, noted the ribs were hollow, unlike those of many other sauropods, but later authors argued this hollowing could also have been due to erosion after the death of the individual. Argentinosaurus, like many titanosaurs, probably had six sacral vertebrae (those in the hip region), although the last one is not preserved. The centra of the second to fifth sacral vertebrae were much reduced in size and considerably smaller than the centrum of the first sacral. The sacral ribs curved downwards. The second sacral rib was larger than the other preserved sacral ribs, though the size of the first is unknown due to its incompleteness.
  Because of their incomplete preservation, the original position of the known dorsal vertebrae within the vertebral column is disputed. Dissenting configurations were suggested by Bonaparte and Coria in 1993; Fernando Novas and Martín Ezcurra in 2006; and Leonardo Salgado and Jaime Powell in 2010. One vertebra was interpreted by these studies as the first, fifth or third; and another vertebra as the second, tenth or eleventh, or ninth, respectively. A reasonably complete vertebra was found to be the third by the 1993 and 2006 studies, but the fourth by the 2010 study. Another vertebra was interpreted by the three studies as being part of the rear section of the dorsal vertebral column, as the fourth, or as the fifth, respectively. In 1993, two articulated (still connected) vertebrae were thought to be of the rear part of the dorsal column but are interpreted as the sixth and seventh vertebrae in the two later studies. The 2010 study mentioned another vertebra that was not mentioned by the 1993 and 2006 studies; it was presumed to belong to the rear part of the dorsal column.
  Another contentious issue is the presence of hyposphene-hypantrum articulations, accessory joints between vertebrae that were located below the main articular processes. Difficulties in interpretation arise from the fragmentary preservation of the vertebral column; these joints are hidden from view in the two connected vertebrae. In 1993, Bonaparte and Coria said the hyposphene-hypantrum articulations were enlarged, as in the related Epachthosaurus, and had additional articular surfaces that extended downwards. This was confirmed by some later authors; Novas noted the hypantrum (a bony extension below the articular processes of the front face of a vertebra) extended sidewards and downwards, forming a much-broadened surface that connected with the equally enlarged hyposphene at the back face of the following vertebra. In 1996, Bonaparte stated these features would have made the spine more rigid and were possibly an adaptation to the giant size of the animal. Other authors argued most titanosaur genera lacked hyposphene-hypantrum articulations and that the articular structures seen in Epachthosaurus and Argentinosaurus are thickened vertebral laminae (ridges). Sebasti
caption: Dorsal vertebra cast in front view at the NHMLAC, with the palaeontologist Matthew Wedel for scale
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