Tuesday, May 11, 2010

Bird and Pterosaur Feet (4)

Plantigrade or Digitigrade?
Plantigrade: "In terrestrial animals, plantigrade locomotion means walking with the podials and metatarsals flat on the ground."
Digitigrade: "A digitigrade is an animal that stands or walks on its digits, or toes."

"We have found a large, uncrushed, partial skeleton of a new species of the basal pterosaur Dimorphodon in thick-bedded deposits of Tamaulipas, Mexico; this material includes such a three-dimensional foot. The nature of this skeleton contradicts an important part of the cursorial interpretation, that is, that only the toes contacted the ground during terrestrial locomotion2, 3, 4, 5, 6, 7. The flattened metatarsal–phalangeal joint at the base of the first four toes of this specimen would not allow such a digitigrade posture without separating most of the joints. A flat-footed stance is consistent with presumed footprints of pterosaurs8, 9, 10 that show impressions of the entire sole of the foot." (jclark@gwis2.circ.gwu.edu).

However see the reference to Padian here (page 11):


"I can send you images of a digitigrade pterosaur track (anurognathid)from a 1964 paper, and models of digitigrade pterosaur feet (MSNB 8950, Pteranodon, Batrachognathus) that don't break any of Jim Clark's rules about bending at the metatarsophalangeal joint.
Of course there's also Rotodactylus tracks that record pre-pterosaur (fenestrasaur) activity with a digitigrade track that has pedal digit V impressing far behind the others, sometimes quadrupedal, other times bipedal.
You can also access the same info in my Ichnos article
Peters, D. 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods. - Ichnos 7(1): 11-41."

See update dated Nov 7, 2012.

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