Wednesday 8 January 2014

Avian footprints from the Early Cretaceous of Victoria State, Australia.

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). The preserved footprints of Birds (which are a form of Dinosaur), are much rarer, as Birds are smaller and lighter than other forms of Dinosaur, and in many cases move by flying or swimming rather than walking.

In a paper published in the journal Palaeontology on 25 October 2013, Anthony Martin of the Department of Environmental Studies at Emory University in Atlanta and the School of Geosciences at Monash University in Clayton, Victoria, Patricia Vickers-Rich, also of the School of Geosciences at Monash University, Thomas Rich of Museum Victoria and Michael Hall, again of the School of Geosciences at Monash University, describe three footprints from a slab eroded from a cliff at Dinosaur Cove, to the west of Cape Otway in Victoria State, Australia.

Overall view of slab recovered from Dinosaur Cove, Victoria, with circles around Track 1 (T1), Track 2 (T2) and Track 3 (T3). Arrow indicates where sample was cut and examined for sedimentological content.  Scale bar is 10 cm. Martin et al. (2013).

The three footprints are referred to as Track 1, Track 2 and Track 3. They do not appear to represent a record of movement, but rather three prints made by separate feet, two of which may come from the right and left foot of the same animal. The prints are preserved in a fine grained fluvial (river) sandstone.

Tracks one and two appear to have been made by the right and left foot of a Bird (or two Birds). They are 10.8-11.4 cm across and 10.6-10.7 cm in length, and appear to represent a narrow foot with three forward pointing claws and a reduced, backward pointing, hind claw. The prints could have been produced by a Enantiornithine (an extinct group of Mesozoic Birds with wing claws and teeth) or Ornithurine Bird (the group that comprises modern Birds and their ancestors), potentially a shorebird with a lifestyle similar to that of a Heron or Crane.

Avian track (Track 1) from Eumeralla Formation, Dinosaur Cove, Victoria. (A) Overall view of track. (B) Line drawing of track and associated pressure-release structures, with digits labelled from I to IV. Grey silhouette indicates inferred foot morphology, not the outline of the track. Thick arrow (below right) points in direction of initial foot movement before abrupt stop, and thin arrow (upper left) points in direction of movement after stop. Missing part of surface denoted by black area between digits III and IV, but fracture omitted. Scale bars are 5 cm. Martin et al. (2013).

Avian track (Track 2) 
from Eumeralla 
Formation, Dinosaur Cove, Victoria. (
A) Overall view of track. (B) Line 
drawing of track and associated 
pressure-release structures, with digits 
labelled from I to IV. Grey silhouette 
indicates inferred foot 
morphology, not of outline of the 
track. Ta = Taenidium isp., crosssection 
of invertebrate burrow. Scale 
bars are 5 cm. 
Martin et al. (2013).

The third print (Track 3) does not appear to come from a Bird. It is another right footprint, but thicker, apparently from a heavier animal and lacking a backward pointing hind toe. Martin et al. suggest that this comes from a small non-avian Theropod Dinosaur, possibly a Coelurosaur.

Theropod track (Track 3) from Eumeralla Formation, Dinosaur Cove, Victoria. (A) Overall view of track. (B) Line drawing of track and associated pressure-release structures, with digits labelled from II to IV. Grey silhouette indicates inferred foot morphology and not the outline of the track. Scale bars are 5 cm. 
Martin et al. (2013).

If the interpretation of these tracks is correct, then they represent the oldest known avian tracks in Australia, and possibly in the southern hemisphere (potential older Bird tracks in Argentina are now thought to be considerably younger, while the avian origin of others in South Africa is disputed).

See also Early Cretaceous Dinosaur footprints from Sichuan Province, ChinaA fossil Vulture from the Miocene of NebraskaA new Long-tailed Bird from the Early Cretaceous of ChinaA fossil Bird from the Eocene of Guangdong Province China and Dinosaur footprints from the Early Cretaceous of Ganzu Province, China.

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