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.

DNA dream time

So how close are scientists to being able to clone a now-extinct species?

Ideally, scientists would start with a species that has recently gone extinct, and one for which we have tissue samples. Australia’s extinct Tasmanian tiger fits these criteria. The last-known captive animal died in 1936.

A team of scientists have inserted part of a bone-making gene from the Tasmanian tiger into a mouse embryo and found that it functioned properly. This marked the first time that DNA from an extinct species successfully induced a functional response in another living organism.

However, scientists are not making plans to exhibit a cloned Tasmanian tiger anytime soon. Through a gene-by-gene study scientists can hope to learn the functions of the genes from extinct species, but assembling an entire animal from fossil genetic material is still the realm of science fiction.

Reference: Pask, A. Behringer, R.R., and Renfree, M., 2008. Resurrection of DNA function In Vivo from an extinct genome. PloS One 3(5)

Photo credit: http://dsc.discovery.com/news/2008/05/20/gallery/tasmanian-tiger-540x380.jpg

DNA from Museum drawers

Scientists have recovered DNA from mammoth hair that had been stored in a drawer at room temperature for the 200 years since the 1799 discovery of a naturally mummified mammoth.

This discovery raises the prospect of sequencing DNA from the hair and feathers of other specimens from museum drawers.

We are still far from cloning extinct organisms from preserved DNA, and a Jurassic Park scenario is still science fiction, but these discoveries, while controversial, have established a new discipline, creating lab standards and research protocol for rigorous and repeatable results.

The information from fossil DNA helps to clarify the relationships between extinct animals and their living descendants.

Reference: Penn State University Webb Miller. Science, 317 (5846), 1927 (Sept. 28, 2007)

Photo credit: Stephan Schuster Lab, Penn State

Oldest DNA

Fossil DNA hunting is a recent phenomenon, as it was long assumed that the molecules could not survive the vagaries of time and preservation to become fossils.

The current claim for oldest preserved DNA comes from 419-million-year-old salt deposits from Canada. This is an amazing claim, as previous “oldest DNA” reports are from animals only tens of thousand years old.

Every claim of old DNA is subject to intense scrutiny and is accepted only after successful independent trials to replicate the results. The 419 million year old DNA is from salt-loving or halophilic bacteria, representatives of which are still around today and which provide a comparison for the fossil DNA sequences.

The discovery of halophiles gives encouragement to looking for microbes in other unusual places...like Mars. Click on today's title to learn more.

Reference: J.S. Park, et al.,, 2009, Geobiology 7 no. 5, p. 515-523, Haloarchaeal diversity in 23, 121 and 419 MYA salts

Ancient accidental pollinators

Back in the days before plants developed flowers to attract insects to help disperse their pollen, wind was the main agent of pollenation.

However, paleontologists recently argued that some pre-flowering plants had pollen receptors located deep within the plant so that wind-borne pollen would be unlikely to reach them. These scientists suggest that a little-known group of fossil insects called scorpionflies might have served in pollinating these pre-flowering plants.

These fossil scorpionflies (descendants of which are still around today) have narrow, elongate mouthparts suited for reaching far into plants and feeding on fluids, so it is unlikely they could have ingested the large pollen grains. Instead, pollen grains may have stuck to the insect’s head or mouthparts as they fed, and scorpionflies became accidental pollinators—the first known pollinators of pre-flowering plants.

Reference: Ren, D., Labandeira, C., Santiago-Blay, J., Rasnitsyn, A., Shih, C., Bashkuev, A., Logan, M., Hotton, C., & Dilcher, D. (2009). A Probable Pollination Mode Before Angiosperms: Eurasian, Long-Proboscid Scorpionflies Science, 326 (5954), 840-847 DOI: 10.1126/science.1178338)

Photo credit: http://z.about.com/d/animals/1/0/n/g/18149_web.jpg

Serendipity with a backhoe

This is a story of what happens when construction workers have some appreciation for interesting rocks and fossils they come across in the course of their daily tasks:

While excavating oil sands in a mine near the town of Ft. McMurray, Alberta, Canada, a heavy machinery operator uncovered the skeleton of a plesiosaur, the extinct, long-necked reptile that inhabited Mesozoic seas.

The skeleton had been fragmented by its excavation by backhoe rather than small hammers, chisels and brushes, but when pieced back together, it was judged to be 80% complete.

The find is significant because it is the earliest North American occurrence of a plesiosaur, extending the known geologic range of these animals to the early part of the Cretaceous Period and this find also expands the known geographic range of plesiosaurs in North America.

Reference: Journal of Paleontology November, 2009, Earliest North American occurrence of a plesiosaur

Photo credit: http://www.dinosaurjungle.com/focus_plesiosaur.jpg. For more on plesiosaurs, go to this site or click on today's title.

The first beetle

The oldest known fossil beetle has been discovered not in an outcrop, but in a museum drawer. A 296 million year old insect has been reclassified as a beetle, pushing back the origin of beetles by millions of years.

The evolutionary success of beetles is traditionally explained by their two-stage life style—they pass through ecologically distinct larval and adult stages that allow them to exploit different niches.

However, the new find creates a large gap between the first appearance of beetles and the diversification of beetles that occurred 65 million years later, and suggests that the innovation of the two-stage lifestyle was not the initial cause of beetle diversity.

This opens the door to other explanations for beetle success, such as the proliferation of the plant species that was favored by the beetle larvae.

Reference: Journal of Paleontology November, 2009, The Earliest Beetle identified (Olivier Bethoux)

Photo credit: This is a much younger fossil beetle from the Eocene (15 million-year-old) Florissant Fossil Beds of Colorado, which preserves a wide variety plant and animal life. Click on today's title for more information.

A New Last Occurrence

Headlines in paleontology usually center on the oldest or first find of a fossil species. However, determining the youngest or last occurrence of a now-extinct species is just as important.

A youngest occurrence was recently confirmed for an extinct group of echinoderms, the phylum that includes starfish, sand dollars, and brittle stars.

Edrioasteroids are one of a number of bizarre echinoderms that went extinct by the end of the Paleozoic Era for reasons not yet understood. These silver-dollar sized, disc-shaped animals lived attached to shells or other hard surfaces on the sea floor.

This discovery comes as paleontologists focus their energy on looking for these fossils in younger rocks to answer questions about the reason for their demise.

Photo credit: drydredgers.org

For more pictures of edrioasteroids click on today's title.

Reference: Journal of Paleontology November, 2009, First definite record of Permian Edrioasteroids: Neoisorophusella from Russia

Great Fossil Faunas, V: The La Brea Tarpits

All the previously described lagerstatte are deposits of organisms from a marine environment. The fifth and final pick for "greatest fauna" is something completely different: The fossils encased in the La Brea tarpits were land-dwellers who became entrapped in a natural asphalt spring, and if for no other reason, the unique environment and fossilizing agent earn the La Brea tarpits a place on our list of top 5 fossil faunas.

How can an animal be so stupid as to fall into an asphalt pool? These were probably not steaming or bubbling pits like the mudpots and geysers of Yellowstone, but still pools of dense oil muck camoflaged by plant debris and perhaps even holding a pool of water.

Animals that came to take a drink got stuck, their distress cries were heard by predators who themselves became ensnared, and finally scavengers that came along for the easy pickings became mired in the muck—leaving a record of the whole food chain, from plants to insects to mammoths to saber tooth tigers and vultures—650 species of plants and animals so far identified, on the basis of 3.5 million fossils recovered, an astonishing diversity of animals that gives us an unprecedented window into an ice-age ecosystem.

Photo from www.papermag.com/blogs/2008/11/mr_mickeys_mustsee_guide_to_la_1.php

Great Fossil Faunas, IV: Solnhofen Limestone

This famous lagerstatte from southern Germany is an obvious choice for a “greatest fossil fauna” list because it is in these fine-grained limestones representing the deposits of an ancient lagoon that the fossils of Archaeopteryx were found.

Archaeopteryx was the first evidence for a link between birds and reptiles, and the discovery of the first specimen came only a few months after Charles Darwin published Origin of Species, in which he made the case for a common ancestry for all organisms.

One of Darwin’s most vexing problems was the apparent lack of the transitional forms between major groups that his theory predicted, and the discovery of Archaeopteryx was an answer to this dilemma.

The lagoon that preserved Archaeopteryx down to its feathers also preserved insects, crustaceans, and echinoderms in exquisite detail, and give us a glimpse into a 150-million-year-old nearshore ecosystem.

For more info on Archaeopteryx click on the title of today's blog.

Great Fossil Faunas, III: The Burgess Shale

You have to love an animal named Hallucigenia, an animal so strange that paleontologists have flipped the original reconstruction of the animal (lower picture, tottering on stiff spines) upside-down (upper picture, with the spines on the back).

Hallucigenia is only one of a menagerie of odd animals known from the Middle Cambrian Burgess Shale of British Columbia. It keeps company with the five-eyed Opabinia, skeletal trilobite-like Marella, and Wiwaxia, a strange enough animal with a truly weird name.

The discovery of the Burgess Shale fauna was another paradigm-breaker. This fauna represented a virtual explosion of body plans early in the history of multicellular life, some of which were culled as experiments in evolutionary design, others that can be traced to groups that left descendents.

new Hallucigenia pic copyright 2003 by Karen Carr

For more information on the Burgess Shale animals, click on today's blog title.

Great Fossil Faunas, II: The Ediacara Fauna

The oldest known fossils of multicellular organisms are known from rocks of what was formerly called the Precambrian Eon.

The Precambrian was long regarded as a time before life appeared, as there were no known fossils from the ancient rocks. The appearance of abundant shelly fossils was taken to mark the end of the Precambrian and the beginning of the subsequent Cambrian Period.

Because of the presumption that Precambrian rocks contained no fossils, the first discovered Ediacarian organisms were not recognized as being organic remains. It was only after multiple similar faunas from Newfoundland, Africa, Australia, and England were discovered that the true significance of these strange creatures was appreciated.

For smashing one of the earliest paradigms of fossil distribution, the Ediacara biota earns a spot on our list of 5 great fossil faunas.

For more information on the Ediacaran organisms click on the title, above.

Great Fossil Fauna, I: Gunflint Chert Flora

The Gunflint chert is part of a sequence of 1.8 billion-year-old rocks exposed in the Gunflint Range of northern Minnesota and western Ontario along the north shore of Lake Superior.

These rocks contain stromatolites, organo-sedimentary structures formed by cyanobacteria trapping and binding sediment, and when examined under the microscope, small spheres, rods and filaments less than 10 micrometers in size are visible in the chert layers--microfossils preserved in near-pristine 3-D.

The discovery of the Gunflint chert caused a paradigm shift in paleontology, as it proved that under exceptional conditions, even very ancient lifeforms could be preserved.

For its role in opening our eyes to the presence of life in very ancient rocks, the Gunflint chert earns a place on our list of “top 5 fossil lagerstatte”

Photo credit: http://www.fas.org/irp/imint/docs/rst/Sect20/A12.html

Fossil "Mother Lodes"

The history of life on Earth is a story told in photographs made of stone--the rocks and fossils preserved when and where conditions were favorable. Some of these photos are time exposures in which events blur together, others, much rarer, are snapshots of an instant in time. These snapshots commonly are the result of the sudden, rapid burial of the organisms living in the environment, as through an ocean storm surge or river flood or avalanche or entrapment in a mucky bog or sticky pit of natural asphalt. These snapshots are characterized by exquisite preservation of anatomical details not usually fossilized, and fossil deposits of this sort are referred to by a German word, lagerstatte, which is a mining term that refers to a "mother lode" or abundance of ore. Fossil lagerstatte are "mother lodes" of exceptionally preserved fossils. The Pennsylvanian (320-286 million year old) Mazon Creek fauna, from which the bizarre Tullymonstrum (the state fossil of Illinois, seen here from the side of a U-Haul truck) is known is one example.

This week's GeoLog challenge is to describe the 5 most significant fossil faunas or lagerstaette, fossil "mother lodes." Despite the relative rarity of exceptional preservation, the list of lagerstaette, for example the list posted on the Wikipedia website, takes up a whole page, so some selection criteria need to be imposed. My "top 5" lagerstaette were chosen to include different geological periods, different depositional or geological environments, and a variety of organisms, from microfossils to dinosaurs, and for their historical significance.

Paleontologically, all lagerstaette are important, because we've learned things from each of them about the variety and diversity of life that we would not have known otherwise.