Their necks were relatively short, for sauropods, and their tails were 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 fossilised 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 with the other giant dinosaurs. There were even some island-dwelling dwarf species, probably the result of allopatric speciation and insular dwarfism.
They were widespread, especially in the southern continents (then part of the supercontinent of Gondwana) and even in Australia, where sauropod remains in Queensland have been determined to be titanosaurid. New remains from an outback town in Queensland, from rocks around 96 million years old, show that Australia too had large titanosaurs, around 25 meters long (82 feet). Four well preserved skeletons of a titanosaur species were found in Italy, a discovery first reported on May 2, 2006. Only Antarctica has yielded no titanosaur remains.Remains have also been recently discovered in New Zealand
The family Titanosauridae was named after and anchored on the poorly known genus Titanosaurus, which was coined by Richard 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 Period. Despite its centrality to titanosaur systematics and biogeography, a re-evaluation of all Titanosaurus species recognises only five as diagnostic. The type species T. indicus is invalid, because it is based on 'obsolescent' characters - once diagnostic features that have gained a broader taxonomic distribution over time. Consequently, use of the genus Titanosaurus has largely been abandoned. The most well known Titanosaurus specimens have since been re-assigned to other genera, including Isisaurus. However, if Titanosaurus indicus is redescribed in the future, on the basis of new finds, Titanosaurus itself becomes provisionally valid.
Some paleontologists (such as Sereno, 2005 ) have contended that Titanosaurus is too poorly known to use as a basis for classification, family names for which it is the type genus (e.g. Titanosaurinae, Titanosauridae, Titanosauroidea) should not have other genera referred to them. Weishampel et al., in the second edition of The Dinosauria, also did not use the family Titanosauridae, and instead used several smaller titanosaur families such as Saltosauridae and Nemegtosauridae.
Relationships within the Titanosauria have historically been extremely variable from study to study, complicated by the fact that clade and rank names have been applied inconsistently by various scientists. One possible cladogram is presented here, and follows a 2007 analysis by Calvo and colleagues. The authors notably used the family Titanosauridae in a broader fashion than other recent studies, and coined the new clade name Lognkosauria.
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