Adamantisaurus
A poorly-known titanosaur from the Late Cretaceous of Brazil.
Adamantisaurus (pronounced AD-ə-MAN-tiss-OR-əs) is a little-known genus of titanosaurian sauropod from the Late Cretaceous of South America. Only six tail vertebrae have been found, but because it is a sauropod, it was likely a very large animal with a long neck and tail. Like many titanosaurs, Adamantisaurus is poorly understood, which makes its exact evolutionary relationships hard to determine. However, it shares some features with Aeolosaurus and with the titanosaur from the Bauru Group once called the "Peiropolis titanosaur," now known as Trigonosaurus.
The species Adamantisaurus mezzalirai is known only from the front part of the tail, so little is known about its overall anatomy. It was probably a medium-sized titanosaur. In 2010, Gregory S. Paul estimated its length at about 13 meters (43 feet) and its weight at 5 tonnes (5.5 short tons). In 2020, Molina-Pérez and Larramendi gave a larger estimate of 18 meters (60 feet) and 14.4 tonnes (15.8 short tons).
The remains were first mentioned in print in 1959, but the dinosaur was not named until 2006, when Brazilian paleontologists Rodrigo Santucci and Reinaldo Bertini described it. The type specimen—the only known material—includes the second through seventh tail vertebrae and two chevrons. Adamantisaurus is known only from the Adamantina Formation in Brazil, part of the Bauru Group. The exact age of the Bauru Group is uncertain, but the Adamantina Formation likely dates from the Turonian to early Maastrichtian stages of the Late Cretaceous (about 93 to 70 million years ago). Adamantisaurus shared this formation with another titanosaur, Gondwanatitan. The genus name comes from the Adamantina Formation in São Paulo state, combined with the Greek word *sauros* (lizard). The only species, *Adamantisaurus mezzalirai*, honors Brazilian geologist Sérgio Mezzalira, who originally found the specimen and first mentioned it in print.
The phylogenetic position of Adamantisaurus has not been rigorously tested. Based on the ball-and-socket joints in its tail vertebrae, it appears to be more derived than Malawisaurus. All titanosaurs at least as derived as Malawisaurus belong to the clade Lithostrotia, but within that group, Adamantisaurus's relationships are unclear. It resembles Aeolosaurus, a close relative of its contemporary Gondwanatitan, in some ways. Adamantisaurus
- Name meaning
- Adamantina lizard
- Time period
- Late Cretaceous (Turonian to early Maastrichtian, ~93–70 million years ago)
- Length estimate
- 13–18 meters (43–60 ft)
- Weight estimate
- 5–14.4 tonnes (5.5–15.8 short tons)
- Known from
- Adamantina Formation, Brazil
- Type species
- Adamantisaurus mezzalirai
- Described by
- Rodrigo Santucci and Reinaldo Bertini (2006)
Lore & Background
Phylogenetically, Adamantisaurus appears more derived than Malawisaurus based on ball-and-socket caudal vertebrae, placing it within the clade Lithostrotia. It resembles Aeolosaurus in some respects but cannot be directly compared to Brasilotitan, another genus from the same formation. Its exact relationships remain unclear.
Reader's Guide
Adamantisaurus is significant primarily as one of several titanosaurian sauropods from the Late Cretaceous of Brazil, adding to the known diversity of South American sauropods. Its discovery highlights the paleontological richness of the Adamantina Formation, part of the Bauru Group, whose stratigraphy and exact age remain unsettled. Although known only from six tail vertebrae, the genus provides data on caudal morphology and evolutionary relationships within Lithostrotia. The uncertainty surrounding its size—ranging from 13 to 18 meters in length—reflects the challenges of reconstructing fragmentary sauropod remains. Its naming in 2006 as the first dinosaur of that year underscores the ongoing pace of paleontological discovery. Comparisons with Aeolosaurus and Trigonosaurus suggest possible affinities, but rigorous phylogenetic testing is still needed. Adamantisaurus thus serves as a reminder of how much remains unknown about Cretaceous ecosystems in South America, and how each new specimen can refine our understanding of titanosaur evolution.
Did You Know?
- Adamantisaurus was named in 2006, but it was not the first dinosaur named that year—several others, like Sinocalliopteryx, were described earlier.
- It is known only from six tail vertebrae and two chevrons.
- The species name mezzalirai honors Brazilian geologist Sérgio Mezzalira, who first mentioned the remains in 1959.
- Size estimates vary widely, from 13 meters and 5 tonnes to 18 meters and 14.4 tonnes.
More in Dinosaur genera 1-24
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record