Titanosaur
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? Titanosaurs Conservation status:
Fossil
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Titanosaurs, were sauropod dinosaurs such as Saltasaurus and Isisaurus. 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 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.
Browsing and grazing diet
Fossilized dung associated with late Cretaceous titanosaurids has revealed phytoliths, silicified plant fragments, that offer clues to a broad, unselective plant diet. Besides the plant remains that might have been expected such as cycads and conifers, discoveries published in 2005 [1] revealed an unexpectedly wide range of monocotyledons including palms and grasses ( Poaceae), including ancestors of rice and bamboo, suggesting that herbivorous dinosaurs and grasses co-evolved.
Nesting grounds
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 behaviour, 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
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 and no longer considered a valid taxon.
[Titanosauria is named after the poorly known genus "Titanosaurus", which was coined by Lydekker in 1877 on the basis of a partial femur and two incomplete caudal vertebrae. Fourteen species have since been referred to "Titanosaurus", which distribute the genus across Argentina, Europe, Madagascar, India and Laos, and throughout 60 million years of the Cretaceous. Despite its centrality to titanosaur systematics and biogeography, the genus "Titanosaurus" has never been revised. A re-evaluation of all "Titanosaurus" species recognises as diagnostic only .ve. The type species T. indicus is invalid because it is based on 'obsolescent' characters - once diagnostic features that have gained abroader taxonomic distributionover time. Consequently, the genus "Titanosaurus" and its co-ordinated rank-taxa (e.g. Titanosaurinae, Titanosauridae, Titanosauroidea) must be abandoned. source* DinoData [2]]
Taxonomy
- Infaorder
Macronaria
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Titanosauria
- Andesaurus
- Epachthosaurus
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Argentinosaurus
- Antarctosaurus
- Malawisaurus
- Family
Nemegtosauridae
- Dyslocosaurus
- Quaesitosaurus
- Bonitasaura
- Rapetosaurus
- Nemegtosaurus
- Argyrosaurus
- Gondwanatitan
- Aeolosaurus
- Alamosaurus
- Isisaurus
- Family
Saltasauridae
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Opisthocoelicaudia
- Subfamily
Saltasaurinae
- Neuquensaurus
- Saltasaurus
- Subfamily
Saltasaurinae
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Opisthocoelicaudia
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Titanosauria