Sunday, 18 August 2013

Early Cretaceous Dinosaur footprints from Sichuan Province, China.

Dinosaur footprints are well documented from a number of sites around the world, and a whole branch of palaeontology (Dinosaur ichnology) is dedicated to their study. This can provide a whole range of data about these animals that would not otherwise be available, particularly with regard to their behavior and environment (finding out where something ended up after it died is not the same as finding out where it lived when it was alive).

In a paper published in the Chinese Science Bulletin on 20 February 2013, a team of scientists led by Lida Xing of the School of the Earth Sciences and Resources at the China University of Geosciences in Beijing discuss a series of Early Cretaceous Dinosaur trackways exposed at the Sanbiluoga Copper Mine in Sichuan Province, China.

The site contains a series of tracks interpreted as Theropod swimming traces (Characichnos). These consist of scratch marks made in the sediments by the tips of the Dinosaur's claws, with only occasional  shallower marks from the rest of the foot, interpreted as marks left by a swimming or floating Theropod Dinosaur propelling itself forwards with footstrokes. This is the first time such traces have been (confidently) documented in China, though similar tracks have previously been described from England, Poland, Spain and Utah.

Theropod swim traces from the Sanbiluoga Copper Mine in Sichuan Province, China. Xing et al. (2013).

The site also contains a number of Theropod walking traces, footprints which imply the animal was putting its full weight on the foot, rather than simply using it to propel itself forwards. Interestingly the spacing of both sets of footprints suggests an animal with a hip joint approximately 90 cm above the ground, which Xing et al. suggest implies the depth of water was not constant at the site when the tracks were being laid down.

Theropod footprints from the Sanbiluoga Copper Mine in Sichuan Province, China. Xing et al. (2013).

The site also contains a set of Sauropod tracks, these apparently being made by a walking animal and running parallel to the Theropod swim traces. However the Sauropod was apparently a much larger animal, with a hip height of 1.7-2.5 m (i.e. an animal that could have walked in 90 cm of water), so little can be inferred from this.

Sauropod walking tracks (left) running parallel to the Theropod swimming traces (right) at the Sanbiluoga Copper Mine in Sichuan Province, China. Xing et al. (2013).

Finally the site contains a number of Ornithopod (Iguanodonts or Hadrosaurs) footprints. These are assigned to the ichnospecies Caririchnium lotus (while not true biological species, trace fossils are often given Latin binomial names in the same way) are interpreted as the hind footprints of animals that may have either walked on two or four feet. The tracks apparently represent a number of individuals of different sizes, interpreted as adult  (tracks 37–40 cm in length), subadult (25–30 cm in length), and tracks of young individuals (19–23 cm in length), which suggests a group of animals moving across the area together. However the tracks are not well preserved, and are largely on a high, steep slope making access difficult, so no further interpretation has been made.

Ornithopod footprints from the Sanbiluoga Copper Mine in Sichuan Province, China. Xing et al. (2013).

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