Plateosauridae

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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


Plateosauridae


Contents

Information

Plateosauridae: Plateosaurus

Range: Upper Triassic to Lower Jurassic.

Phylogeny: Prosauropoda :::: (Massospondylidae + Yunnanosaurus) + *.

Characters

  • Medium to large size.

NB: As the boundaries of the clade are vague, the following are the characters of Plateosaurus:

  • Skull narrow.
  • Postorbital portion curved ventrally; nostrils large.
  • Jaw articulation well below teeth.
  • Teeth regularly replaced.
  • No wear facets on teeth.
  • Teeth do not articulate.
  • Cervical ribs delicate and oriented post.
  • 10 caudal, 15 trunk vertebrae.
  • Thin gastralia present.
  • 3 sacrals.
  • Clavicle present.
  • Radius about 50% length of humerus, ulna 75%(?).
  • Proximal carpals unknown, perhaps cartilaginous (thus manus not weight-bearing?!).
  • Manus I at 45 deg to axis of hand.
  • Anterior process of ilium pointed.
  • Acetabulum perforate, with crest.
  • 4th trochanter very prominent and located in distal half of femur (indicates quadrupedality).
  • Tibia length 75% of femur (slow).
  • Distal tarsals III and IV disk-like and triangular.
  • All metatarsals of similar thickness.
  • Common in Norian Europe.

Discussion

Galton (2001, 2002) has shown that the type specimen of Plateosaurus engelhardti is distinct from the well-known specimens usually placed under that name, and has reinstated Plateosaurus longiceps as the next available name for these animals. Plateosaurus longiceps (= P. trossingensis) is thus a valid species, but P. erlenbergiensis is generically indeterminate. Most specimens (from Halberstadt, Trossingen, Stuttgart-Degerloch, France, Switzerland and Greenland belong to P. longiceps, but the Bavarian ones are P. engelhardti. [synopsis Mortimer 2001]. The less well known P. engelhardti is more heavily built and quadrupedal; P. longiceps is more lightly built and represents most specimens of Plateosaurus, including the famous Trossingen remains [ref. Justin Tweet - Sauropodomorpha]. Adam Yates considers that Galton has not gone far enough in the paper, as the two species share no synapomorphies, and suggests that a generic name needs to be applied to P. longiceps. For the present, we have retained the name Plateosaurus.

A third species - Plateosaurus gracilis Huene 1907-08, more usually placed in a separate genus Sellosaurus, is less derived and occurs slightly earlier (Middle Stubensandstein). It was a large animal for its time, 4 to 6 meters long. Galton (2001) suggested Sellosaurus is more than one species- Efraasia diagnostica and Sellosaurus gracilis. [synopsis Mortimer 2001]. According to Yates 2003 Sellosaurus gracilis contains a substantial amount of variation, and it has been found that there are two discrete taxa . The more common one is a generalised (plesiomorphic) species called Efraasia minor; the less common one shares a number of synapomorphies with Plateosaurus engelhardti and is placed in this genus as Plateosaurus gracilis . It represents the beginning of the Plateosaur lineage, a group that evolved parallel to the main sauropod ancestry, and quickly evolved to large size.

Links

References

  • Galton, 2001. Valid species of prosauropod dinosaurs from the Upper Triassic of Germany. JVP 21(3) 52A.
  • Galton, Peter M., 2002 The prosauropod dinosaur Plateosaurus Meyer, 1837 (Saurischia: Sauropodomorpha; Upper Triassic). II. Notes on the referred species. – Revue Paléobiol., 20 (2) (2001): 435-502; Genève.
  • Mickey Mortimer, 2001 DML.
  • Yates A.M. 2000 Dinosaur Mailing List
  • Yates, A.M. & Kitching, J. W. (2003) The earliest known sauropod dinosaur and the first steps towards sauropod locomotion. Proc. R. Soc. Lond.: B DOI 10.1098/rspb.2003.2417.

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