Aegyptosaurus
Andesaurus
Antarctosaurus
Argentinosaurus
Argyrosaurus
Bruhathkayosaurus
Paralititan
Saltasaurus
Titanosaurus

Titanosaurids, or members of the family Titanosauridae, are sauropod dinosaurs such as Saltasaurus and Titanosaurus . This family includes some of the heaviest creatures ever to walk the earth, such as the Argentinosaurus and the Paralititan — which might have weighed up to 100 tonnes (110 short tons), or perhaps even double that, if some poorly-described data is believed (see the Bruhathkayosaurus).

Characteristics

Titanosaurs had small heads, even when compared to other sauropods. The head was also wide, similar to the heads of the Camarasaurus and the Brachiosaurus, but more elongated. Their nostrils were large ("marcronarian"), and they all had crests formed by these nasal bones. Their teeth were either somewhat spatulate (spoon-like), or like pegs or pencils, but were always very small.

Their necks were relatively short, for sauropods, and their tail was whip-like but not as long as a diplodocid. While the pelvis (hip area) was slimmer than some sauropods, the pectoral (chest area) was much wider, giving them a uniquely "wide-gauged" stance. As a result, the fossiled trackways of titanosaurs are distinctly broader than than other sauropods. Their forelimbs were also stocky, but their rear limbs were longer. Their vertebrae (back bones) were solid (not hollowed-out), which may be a throwback to more primitive saurischians. Their spinal column was more flexible, so they were probably more agile than their cousins, and better at rearing up.

From skin impressions found with the fossils, it has been determined that their skin was armored with a small mosaic of small, bead-like scales around a larger scale. One species has even been discovered with bony plates, like the Ankylosaurus.

While they were all huge, many were fairly average in size compared to the other giant dinosaurs. There were even some island-dwelling dwarf species, probably the result of allopatric speciation.

Nesting grounds

This is the largest nesting ground ever discovered, with just miles and miles of eggs buried in the dirt and rock.

—Luis Chiappe, Natural History Museum of Los Angeles County

A large titanosaurid nesting ground was recently discovered in Auca Mahuevot, in Patagonia, Argentina, and another colony has reportedly been discovered in Spain. The small eggs, about 11–12 cm (4–5 in.) in diameter, contained fossiled embryos, complete with skin impressions (though there was no indication of feathers or dermal spines). Apparently several hundred female saltosaurs dug holes, laid their eggs, and then buried them under dirt and vegetation. This gives evidence of herd behavior, which along with their armor, may have been a defense against large predators like the Abelisaurus .

Range

The titanosaurs were the last great group of sauropods before the Cretaceous-Tertiary extinction event, about 65–90 million years ago, and were the dominant herbivores of their time. The other sauropods, like the diplodocids and the brachiosaurids , died out between the late Jurassic and the mid-Cretaceous, while the titanosaurs appeared in the early Cretaceous, and grew in strength until the end.

They were widespread, especially in the southern continents that were then part of the supercontinent of Gondwana. Only Central and North America (then part of the Laurasia supercontinent), and Antarctica appear to have never been populated by titanosaurs.

Classification

We are always finding bodies without heads. For some reason the heads just seem to come off.

—Matthew Carrano, Curator of Dinosaurs, Smithsonian Institution's National Museum of Natural History

For a such a wipespread and successful group (they represent roughly a third of the total sauropod diversity known to date), the fossil record of titanosaurs is poor. Only recently have skulls or relatively complete skeletons (see Rapetosaurus) of any of the roughly 50 species of titanosaur been discovered. Many are poorly known, and much of the material may be deemed invalid, or reclassified as understanding of the clade grows. The anchor taxon, the Titanosaurus, is particularly poorly known.

External links

• The Geological Society article Best ever titanosaur skeleton discovered in Madagascar
• National Geographic article, Eggs Hold Skulls of Titanosaur Embryos
• Channel 4 article, Titanosaur eggs in France.
• The Dinosauricon's Titanosauria cladogram.