Prosauropoda

From Palaeos

Jump to: navigation, search
Parent taxa:
(check the following menu and phylogeny - the taxon in bold refers to the topic on this page)


SAUROPODOMORPHA
Taxonomy Phylogeny 
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


Prosauropoda



Contents

Information

Range: Late Triassic to Early Jurassic

Phylogeny: Sauropodomorpha ::: "Anchisauria" + * : ((Plateosauridae + (Massospondylidae + Yunnanosaurus)) + Riojasaurus). NB: despite considerable recent interest, the subdivision of * may amount to no more than "small, medium and large" The taxonomy here is based in part on a simplification of Galton (1990).

Characters

  • $ Articular with a narrow, prong-shaped retroarticular process and a marked medial embayment behind the glenoid in dorsal view.
  • $ Distal ends of anterior dorsal neural spines with centrally placed lateral processes.
  • $ Skull about 1/2 length of femur; supposed keratinous beak and fleshy cheek.
  • $ Jaw articulation slightly below maxillary teeth (brings teeth to bear serially in slicing, scissor-like motion).
  • $ Marked ascending process of maxilla.
  • Uniform foliate teeth with coarse marginal serrations.
  • $ Distal ischial process triangular.
  • $ Distal part of pubes "apron-shaped" (see Lecture 11).
  • Manus I with large, pointed ungual.
  • Manus IV and V reduced;
  • Pes V vestigial.
  • No display structures known.
  • Herbivorous.
  • Tended to increase size and become more quadrupedal.
  • Extremely successful in upper Triassic.

Discussion

Originally considered the most primitive suborder of Sauropodomorpha, the Prosauropoda are now either considered a paraphyletic assemblage of early sauropodamorpha, or, more usually a sister clade to the sauropoda proper. While there is considerable evidence on both sides of the question, but many workers favor the idea that sauropods branched off from basal saurischian stock, rather than being descended from prosauropods. Research by Adam Yates now indicates that both Prosauropods and Sauropods diverged from an early "thecodontiosaurid" ancestor, with Anchisaurus (previously considered a primitive "prosauropod" or basal sauropodamorph) representing the most primitive (but not the earliest) known Sauropod. To avoid confusion with the conventional concept of Sauropods as massive quadrapedal herbivores, I have used the term "Anchisauria" to designate Sauropoda sensu Yates. In view of this rearrangement, some of the following synapomorphies should now be considered plesiomorphic.

The Prosauropoda (now minus the "Thecodontosauridae" and Anchisaurus) are first known from the latest Carnian or early Norian Caturrita Formation of Brazil, if the 2.5 meter long Unaysaurus tolentinoi does indeed turn out to belong here [Leal et al. (2004). They quickly dominated the large plant-eater ecological niche previously filled by dicynodonts and rhynchosaurs up until the Carnian (however Dicynodonts still continued in some areas). Within a few short million years they had grown into very large forms like Plateosaurus, Euskelosaurus, and Riojasaurus, which attained lengths of 6 to 10 metres and weights of up to 2 tonnes, and had become an obligatory quadraped due to large size. Despite the superficial similarity, these animals were only distantly related to the Vulcanodont sauropods.

Links

Credits

Retrieved from "http://www.palaeos.org/Prosauropoda"
Personal tools