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Prehistoric Life/Dinosaurs/Sauropod Predecessors: Difference between revisions
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At a first glance, prosauropods (“before the sauropods”) seem simple variations of a single dinosaur: always with the mixed theropod/sauropod shape that characterize the stock species, ''[[Stock Dinosaurs|Plateosaurus]]''. Actually their resemblance was not necessarily a real sign of relationship: their bodyplan was simply a primitive condition, shared by all most archaic sauropodomorphs. According to recent classifications, the prosauropods in traditional sense can be divided in three ensembles: “core prosauropods”, “near sauropods” and “really basal sauropodomorphs”. The first were typical "prosauropods", large to medium-sized bipedal dinosaurs intermediate between more basal sauropodomorphs and proper sauropods. The second ones were more closely related to sauropods and gave rise to them, and were usually larger than other "prosauropods" as well as being capable of some quadrupedality. The third ones were more primitive than both “core prosauropods” and “near sauropods”. As none of these are natural groupings, there isn’t any external trait which allows to distinguish these groups: both “core prosauropods” and “near sauropods” included small and big animals, for example. Even their period is not indicative: both Late Triassic and Early Jurassic were inhabited by “core prosauropods” and “near sauropods”. However, for the sake of convenience, we put here all the examples of traditionally-intended "prosauropods" together, specifying for each its possible placement in the evolutionary tree.
The little cousin: ''[[wikipedia:Massospondylus|Massospondylus]]''
* The musically-named ''Massospondylus'': is the most well-known "prosauropod" after ''Plateosaurus''. Almost a hundred individuals have been discovered so far in Southern Africa, but some doubtful remains from North America are also known. ''Massospondylus'' was a “core prosauropod” (like ''Plateosaurus'') according to modern classifications. 4-5 m long, smaller than ''Plateosaurus'', ''Massospondylus'' had a smaller head, slimmer neck, nimbler limbs and shorter trunk, in short, was a bit like a ''Plateosaurus'' which has undergone a weight-reducing diet. ''Massospondylus'' lived ''after Plateosaurus'', in the Early Jurassic, and was one of the last "prosauropods". Recently, many nests and hatchlings have been discovered in South Africa from this dinosaur, making ''Massospondylus'' one of the dinosaurs we know the most about. The lacking of teeth among the youngest nestlings has surprised scientists: this makes a concrete proof about active parental care from their parents, since these youngsters couldn't feed on their own with their toothless jaws. Adult ''Massospondylus'' were probably vegetarian, even though they could have also caught some insects occasionally: some gastroliths (gizzard-stones) found in the ribcage of some individuals seem to confirm a mainly herbivorous diet. Like all "prosauropods", ''Massospondylus'' used to be depicted as a quadruped in old paleo-art: [[Science Marches On|now we think it was totally bipedal]] like ''Plateosaurus'' – even though newborn ''Massospondylus'' appear to have been quadrupeds. ''Massospondylus'' has yet to appear in documentaries despite being very well-understood, and probably will never appear in fiction, [[Rule of Cool|not being striking enough to attract pop-writers]].
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An old story: ''[[wikipedia:Anchisaurus|Anchisaurus]]''
* Remember Dino, [[The Flintstones]]’ pet dinosaur? Its shape is very reminding of a prosauropod; more in particular, with its short limbs, it recalls this one: ''Anchisaurus'' - this doesn’t means Dino is really an ''Anchisaurus''… considering the writers’ [[Sarcasm Mode|great love for research]] he’s more probably a [[Funny Animal|funny sauropod]]. Despite its scarce fossil record, ''Anchisaurus'' is one of the most famed sauropod predecessors, thanks to its historical importance. It was the ''very first'' dinosaur ever discovered in North America (1818, ''six years before Megalosaurus''). But was not recognized as a dinosaur at the time: this happened only during the Bone Wars sixty years later. An Early Jurassic animal like ''Massospondylus'', ''Anchisaurus'' was even smaller (only 9 ft long) and one of the most unsauropod-like “prosauropods”, with its rather short neck and limbs. Talking about its modern classification, several scientists now think ''Anchisaurus'' was a “near sauropod”. The larger-sized ''Ammosaurus'' is a less-known relative of ''Anchisaurus'' from the same habitat, although it could simply be another species of ''Anchisaurus''.
Mousesaur: ''[[wikipedia:Mussaurus|Mussaurus]]''
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Ancestor or Non-ancestor: ''[[wikipedia:Melanorosaurus|Melanorosaurus]]'' and ''[[wikipedia:Riojasaurus|Riojasaurus]]''
* ''Riojasaurus'' was the polar opposite of the “mouse reptile”. Its Spanish-sounding name reveals it also lived in Triassic Argentina, but was bigger. More than 10 m long, was one of the largest land animals of the Triassic, even bigger than ''Plateosaurus'' itself; its success is shown by its abundant record (more than 30 individuals). At a first glance, ''Riojasaurus'' resembles more a sauropod, with the same size of many “small” sauropods, massive limbs and stocky body. However, the structure of its feet with distinct digits is typically "prosauropodian"; ironically, ''Riojasaurus'' seems to be a “core prosauropod”. It had also one twin in South Africa, ''Melanorosaurus''. Contemporary to ''Riojasaurus'', the two dinosaurs maybe could have met in life, since Africa and South America were reuned in the “Pangea” at the time. Both the same size, with the same robust sauropodian shape but "prosauropod"-like feet, they were perhaps mainly quadrupedal. Both were candidates for the title of “the ancestor of all sauropods”: [[Science Marches On|recent research]] has shown ''Melanorosaurus was'' indeed a "near sauropod", and the riojasaur’s similar frame was obtained by convergent evolution. However, some “core prosauropods” did live alongside ''Melanorosaurus'' in South Africa: among them, ''Euskelosaurus'' was only slightly smaller than ''Melanorosaurus''.
Mailing With Dinosaurs: ''[[wikipedia:Lufengosaurus|Lufengosaurus]]''
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{{reflist}}
[[Category:Tropesaurus Index]]
[[Category:Prehistoric Life
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