The pitter-patter of thunder lizard feet

A dozen tiny, three-toed footprints were discovered in rocks about 120 million years old in coastal South Korea.

The tracks, no bigger than one and a half centimeters long, were originally made in mud, now hardened to shale, along a Jurassic riverbank. The tracks resemble those of therapod dinosaurs, the bipedal carnivores.

These tracks are not necessarily evidence of a new species of diminuative dinosaur; paleontologists previously found larger fossil footprints in the area and so these miniature tracks were probably made by a hatchling.

The size of the tracks can be used to estimate the size of the hatchling, which was probably no more than 4 centimeters at the hip. For now, these are the smallest dinosaur tracks known.

Photo credit: Kyung Soo Kim of Chinju National University of Education in Jinju, South Korea

First footprints, revisited

GeoLog has previously reported on the first footprints made on land, tracks in 530-million year old sandstone made by some sort of invertebrate animal, probably an arthropod—a millipede, perhaps. Now comes word of the oldest known footprints of a four-legged vertebrate, or tetrapod, in rocks 395 million years old.

This find is significant because the tracks predate the oldest known tetrapod body fossils by 18 million years, and if these tracks are indeed made by tetrapods, the find would push back the timing of the vertebrate transition from water to land.

In the absence of accompanying body fossils, it is difficult to definitively match trackways with track-makers, and one alternative explanation is that these trackways could have been made by lobe-finned fishes, precursors to the tetrapods.

[One more note: The trackways represent several different animals ranging from an estimated 50 centimeters long to 2 and a half meters long—quite a large animal for so early in tetrapod evolution.]

Sources: Grzegorz Niedźwiedzki, Piotr Szrek, Katarzyna Narkiewicz, Marek Narkiewicz & Per E. Ahlberg ^{Nature 463, 43-48 (7 January 2010) Tetrapod trackways from the early Middle Devonian period of Poland}

Perkins, S., 2010, Fossil footprints could push back origin of first four-limbed animals. Science News January 30, 2010.

Walking with dinosaurs

How do you make sense of footprints made by extinct animals millions of years ago?

In the case of dinosaurs, analogy with their living avian cousins provides information. For the bipedal theropod dinosaurs, the group that includes T. rex, emus appear to be the best candidates for study.

A fossil dinosaur trackway in northern Wyoming comprises thousand of tracks with a curious gait. Watching emus made sense of these tracks in which the dinosaurs appeared to have crossed one leg over the other.

Emus tend to look around, and this “scanning behavior” causes them to cross their legs when they walk. It is likely that the Jurassic dinosaurs did the same thing.

The Wyoming trackways suggest that the dinosaurs that made them traveled in groups, and may have cared for their young, as juvenile and adult tracks are found together.

Research by Brett Breithaupt, presented at Philadelphia meeting of the Geological Society of America

Kiwi Dinosaurs

Dinosaurs in New Zealand are known only from fragments of bone and a few vertebrae, all from New Zealand’s North Island. The announcement of the discovery of dinosaur footprints on New Zealand’s South Island is the first evidence for dinosaurs on this land mass.

The South Island discovery comes from 70-million year old sandstone and the footprints are spread over 10 km. The footprints were discovered by a geologist exploring for oil and gas. Other geological and biological explanations had to be ruled out and the impressions compared with prints from similar-aged rocks in other parts of the world before their identity as footprints could be confirmed.

The South Island footprints are similar to those of sauropods, the huge plant-eating dinosaurs of the Mesozoic Era, and their discovery raises the possibility of finding more evidence of dinosaurs in New Zealand.

Source: http://www.abc.net.au/science/articles/2009/11/09/2737189.htm

Photo credit: http://gbweekly.co.nz/2009/11/11/dinosaur-prints-confirmed-whanganui-inlet-reveals-a-new-zealand-first