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

Antarctic dinosaurs

Antarctica does not immediately come to mind when thinking about places to go to hunt dinosaur fossils, but there are seven dinosaur species known from the continent that sits over the south pole.

Geological expeditions to Antarctica are of course limited by the continental ice sheet that covers 99% of the land surface, and exposures of potential fossil-bearing rock are limited to exposures along the coastlines and on mountain slopes, so the full extent of Antarctica’s fossil treasures may never be known.

Of course, the continent was not entombed in ice when the dinosaurs roamed Antarctica’s landscape; although Antarctica has been sitting at its polar latitude for the last hundred million years, and dinosaurs would have had to adapt to six months of darkness, the climate during the Cretaceous Period was warmer, and Antarctica hosted cycads, palms and ginkos.

Photo Credit: Nathan Smith. Caption: Kevin Kruger, Peter Barrett and Nathan Smith (from left) excavate dinosaur bones in 2003-04 on Mount Kirkpatrick. http://antarcticsun.usap.gov/antarcticsun/science/images/dinosaur%20excavation.jpg

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

Burrowing Dinosaurs

We tend not to think of dinosaurs as creatures that needed to hide, but a specialist in trace fossils, that is, fossil tracks, trails, and footprints, has identified fossils of a small adult and two juvenile dinosaurs in what he interprets as a fossil burrow in 95-million year old sedimentary rocks in Montana.

Ichnologist Anthony Martin of Emory University in Georgia presumes that the dinosaurs used the burrow to protect themselves from predatory dinosaurs.

More recently Martin identified similar burrow structures in 105-million year old sedimentary rocks from Victoria, Australia. The burrows are about 2 meters long and 30 centimeters in diameter and spiral downward to end in an enlarged chamber.

During the Early Cretaceous Period the average annual temperature in Victoria was probably less than 20 C (68 F). So in addition to serving as protection from predators, a burrowing habit may have served to protect the cold-blooded reptiles from freezing winter temperatures.

Research by Anthony Martin, published in Cretaceous Research (October, 2009)

Dinosaurs Down Under

The Mesozoic Era is more widely known as “The Age of the Dinosaurs” because it was during this time in Earth history that dinosaurs and other reptiles emerged as the dominant life forms, occupying just about every ecological niche and ranging from tropical to near-polar latitudes.

Dinosaurs have been found on every continent, but North America and China enjoy especially diverse and abundant dinosaur faunas, reflecting favorable living conditions for dinosaurs as well as favorable conditions for their preservation.

During the Mesozoic, Australia was located at high latitudes in the southern hemisphere, and was in the process of separating from the supercontinent Pangea. Dinosaur discoveries Down Under are rare, and each new dinosaur find is newsworthy, so the recent discovery of three new Australian dinosaurs is a quantum leap in understanding the geographic range of southern hemisphere dinosaurs.

Reference: Hocknull SA, White MA, Tischler TR, Cook AG, Calleja ND, Sloan T, Elliott E. (2009) New Mid-Cretaceous (Latest Albian) Dinosaurs from Winton, Queensland, Australia. PLoS ONE 4(7): e6190. doi:10.1371/journal.pone.0006190

Photo credit: http://paleonews.files.wordpress.com/2009/07/2009-07-03-australian-dinosaurs.jpg

Whither Jurassic Park?

So will the science of Jurassic Park remain within the realm of fiction, or will someday genetically engineered mammoths, dinosaurs, and trilobites again roam the Earth?

It is unscientific to use terms like “never” except in cases where the realization of a phenomenon would require violation of physical laws of nature, and in paleontology paradigms are often overturned by the discovery of a single, fortuitous fossil, so especially in paleontology is it unwise to use the term.

Michael Crichton’s books were best sellers because they were plausible science fiction—as were Jules Verne’s and Arthur C. Clarke’s imaginings of the future. Some of their visions have been realized, others have not. It is the “possibility of the possible” that attracts writers to science fiction, and scientists to science.

Photo credit: http://www.3dscience.com

S'moa DNA

Scientists from Down Under have extracted DNA from feathers of the extinct moa, the 2.5 meter tall birds that dominated New Zealand’s terrestrial ecosystems until the arrival of humans and non-native mammals about 700 years ago.

Previously, DNA had been extracted from the feathers of modern birds and from museum specimens of birds that have gone extinct in historical time, and only from the base or quill end of the feathers.

The moa study showed that viable DNA could be obtained from older, subfossil feathers and from the distal end of the feather, the rachis and barbs. Scientists are not seeking to use the DNA to clone the moa, but to identify the species of moa that they come from.

The success with moa feathers demonstrates that useful information can be obtained from subfossil feathers and from parts of feathers not previously considered useful in genetic analysis.

Reference: Nicolas J. Rawlence, Jamie R. Wood, Kyle N. Armstrong, and Alan Cooper, 2009, DNA content and distribution in ancient feathers and potential to reconstruct the plumage of extinct avian taxa. Proceedings of the Royal Society, B, October 7, 2009 276:3395-3402; published online before print July 1, 2009, doi:10.1098/rspb.2009.0755

Photo credit: Extinct Monsters by Rev. H. N. Hutchinson, illustrations by Joseph Smit (1836-1929) and others. 4th ed., 1896. Plate XXIII between pages 232 and 233.