Sauropoda
From Palaeos
| SAUROPODOMORPHA | |
| Taxonomy | Phylogeny |
Class: Reptilia/Sauropsida
|
o Saurischia `--o SAUROPODOMORPHA |--Saturnalia tupiniquim `--+--Thecodontosaurus `--+--Efraasia minor |--o Prosauropoda | `--+--+--Plateosauridae | | `--+--Massospondylidae | | `--Yunnanosaurus | `--Riojasaurus `--o--Anchisaurus `--+--Melanorosauridae `--o Sauropoda (sensu stricto) `==Vulcanodontidae `==Cetiosauridae `--o--Diplodocomorpha `--Macronaria |
Contents |
[edit] Introduction
The sauropods are the gigantic long-necked plant-eating dinosaurs, and include such well-known names as Apatosaurus ("Brontosaurus"), Brachiosaurus, Cetiosaurus, and Diplodocus, as well as numerous other species and genera. They were the largest of all land animals, and among the most successful and long-lived of the dinosaurs. The earliest known species, the small Vulcanodon (6 1/2 metres) dates back to the Sinemurian epoch, while the latest include a number of species such as the small Titanosaurus indicus and Hypselosaurus priscus (lengths about 12 metres), and the large Alamosaurus sanjuanensis (20 metres), were still flourishing right up until the terminal Cretaceous extinction. It was at one time thought (on the basis of the North American fossil record) that the sauropods became rare after the Late Jurassic, but in most parts of the world they continued as a common element of the megafauna until the very end of the Cretaceous. Throughout their long history they continued to evolve and branch out new species and families. There are at least three peaks of sauropod diversity in the Late Jurassic, late Early Cretaceous and latest Cretaceous, corresponding to high sea levels and increased speciation resulting from geographical isolation.
Sauropods were long believed to be semi-aquatic swamp wallowers, relying on the bouyancy of water to support their massive bodies. But analysis of their skeletons, in comparison with those of large terrestrial and semi-aquatic animals, and of sedimentation where their fossils have been found, show that sauropods were fully terrestrial:
- "The deep thorax of sauropods is an adaption to problems of terrestrial weight-bearing. Sauropod foot and limb structure is generally comparable to elephants...(S)edimentological evidence does not suport immersion in deep lakes as....frequently pictured..."
[Walter Coombs, p.1]
Not only were sauropods as terrestrial as elephants, but fossil trackways indicate that they lived in herds, again like elephants today. It must have been a truely awesome sight to watch a herd of brontosaurs crossing a Mesozoic floodplain; evoking the same sense of awe, and puniness in one's own being in comparison, as one would feel when observing whales close up.
The Sauropoda include the largest animals ever to walk on land. These gigantic herbivores reaches lengths of 15 to 25 metres or more (the very largest may have reached 45 metres) and weights of 15 to 30 or even 50 or 60 tonnes. Previous estimates of 87 to 150 tonne animals are unrealistic and physiologically impossible. No sauropod ever equalled in size the greatest of the baleen whales.
Sauropods were superbly adapted creatures, the Mesozoic equivalent of the elephant. They had an advanced (not a lizard-like) metabolism, inhabited every continent and continued to evolve and diversify right up until the terminal Mesozoic extinction. It has been suggested that they were cold-blooded like conventional reptiles; that they could not possibly have been endothermic, because they were too big to eat enough food to fuel their bodies. This argument falls apart when you realise most weight estimates have been overstated. An analysis of the load-bearing capacity of Giraffatitan ("Brachiosaurus") brancai limb bones show that this creature could only have weighed 15 tonnes, not the 50 to 80 tonnes that had previously been estimated Russell et al. (1980). Combine that with a huge stomach full of gastric stones (giving a food-grinding ability greater than any elephant's) and a gut full of symbiotic bacteria, and the possibility they were at least partially endothermic is not too unreasonable. Whether they had the full endothermy of birds, mammals, or small theropod dinosaurs is another question. The most likely explanation is that (and this would be true of most large dinosaurs) they started out as active fully endothermic youngsters and settled down into a gigantothermic metabolism as they approached adult size.
There are currently eight valid families of sauropods: Vulcanodontidae, Cetiosauridae, Brachiosauridae, Camarasauridae, Diplodocidae, Euhelopodidae, Dicraeosauridae and Titanosauridae. However, this is certainly an underdestimate of the true diversity of these amazing beasts. Ironically, despite their great size (which would one would think would enable more frequent preservation of remains) the fossil record is quite poor, perhaps due to the large skeletons being scattered before sediment settles to cover them. Most sauropod remains are actually scattered and isolated bones and teeth.
| SAUROPODA | |
| Taxonomy | Phylogeny |
Class: Reptilia/Sauropsida
|
o Sauropodomorpha `--o--Anchisaurus `--+--Melanorosauridae `--o SAUROPODA `--+--Vulcanodon `--o Eusauropoda |==Cetiosauridae |--Omeisauridae `--+--Jobaria tiquidensis |?-Haplocanthosaurus `--o Neosauropoda |--o Diplodocomorpha `--o Macronaria |--Brachiosauridae `--o Somphospondylii |?--Euhelopodidae `--o Titanosauria |--Nemegtosauridae `--Saltosauridae |
[edit] Information
Range: Worldwide, Upper Triassic to Upper Cretaceous.
Phylogeny: Sauropodomorpha: Prosauropoda + Sauropoda : Vulcanodon + Eusauropoda.
[edit] Characters
- Very large (7-40 m), quadrupedal herbivorous forms;
- Small head;
- Blunt teeth; nares located high up on the skulls close to orbits;
- Very long neck; long tail;
- Caudal transverse processes dorsoventrally expanded [S+05];
- Erect, graviportal elephant-like limbs;
- Digits 5/5;
- Some with partial body armor.
[edit] Links
- DinoData: Sauropoda
- Sauropoda
- sauropoda cladogram
- Basal Sauropoda
- Sauropods - Paleontology and Geology Glossary
- ?????? Sauropoda
- Witmer's Lab Dinosaur Skull Collection: Sauropoda
- Literature - Sauropoda
- The Natural History Museum's Dino Directory
- Sauropodomorpha
- sauropoda
[edit] References
- Salgado, L, S Apesteguía & SE Heredia (2005), A new specimen of Neuquensaurus australis, a Late Cretaceous saltasaurine titanosaur from North Patagonia. J. Vert. Paleontol. 25: 623-634.
- Russell et al. (1980);
[edit] Credits
- Placeholder page MAK061025
- Palaeos.com
