Dinosaur National Monument

In 1909 Earl Douglass, a vertebrate paleontologist from the Carnegie Museum of Pittsburgh, Pennsylvania, mounted an expedition to northeastern Utah to prospect for dinosaurs for his Museum.

Douglass chose his prospecting site carefully, knowing that dinosaurs were likely to be found in the preserved sediments of ancient river systems. The expedition was a resounding success, and in 1915 President Woodrow Wilson proclaimed the Douglass quarry Dinosaur National Monument.

The Monument preserves the remains of more than 1500 fossil bones in place in the sandstone in which they were preserved. Thanks to tectonics, the originally flat-lying sedimentary rock layers were tilted upwards so that the fossil bone bed forms a wall of the visitor’s center, a kind of paleontological bas relief.

More information from the National Parks Service here.

T. rex: Top predator for Road Kill King?

Despite its fearsome, pointed, serrated teeth and portrayal in the movies, some scientists suspect that T. rex scavenged carcasses instead of hunted down prey.

This conclusion comes from studies of modern predator/prey ecosystems, estimating the number of prey needed to support an animal of T. rex size. One group of researchers estimate that in Africa’s Serengeti grasslands, enough herbivores die daily to feed a 6,000 kg T. rex, if the dinosaur was cold-blooded, spent half a day foraging and had senses to detect carrion up to 80 meters away.

But what if T. rex were warm-blooded and had to maintain a higher metabolism? It would need more food, but it would also be able to more faster and cover more ground.

Original work: Graeme D. Ruxton and David C. Houston, 2003. could Tyrannosaurus rex have been a scavenger rather than a predator? An energetics approach. Proceedings of the Royal Society of London. B. Download their article here.

Was Sue sick?

Sue, the largest, most complete Tyrannosaurus rex found to date may have been laid low by microscopic parasites.

Paleontologists have puzzled over smooth, round holes in Sue’s jaws. Originally thought to be bite marks from another T. rex, a new analysis concludes that the holes were the result of a parasitic infection that is known to affect modern avian raptors like hawks and eagles.

The infection probably caused lesions and swelling in Sue’s mouth and throat, prompting one researcher to speculate that the infection may have killed Sue as she found it increasingly hard to swallow as the infection spread, and she may have starved to death.

It is difficult to determine the cause of death for an animal that died millions of years ago, but this finding suggests that modern birds may owe their susceptibility to this parasite to their therapod ancestors.

Research from Ewan D.S. Wolff, et al., Common avian infection plagued the tyrant dinosaurs. PLoS One

Veggie rex

Tyrannosaurus rex belongs to a group of dinosaurs called theropods. These dinosaurs generally have serrated, knife-like teeth that are typical of meat-eating carnivores.

The discovery of a small theropod dinosaur in China, however, shows that this group had more diversified dietary habits. This new dinosaur, named Incisivosaurus, for its large front teeth, shows wear marks on its teeth that are typical of tooth wear seen in plant-eaters.

Incisivosaurus teeth also lack the serrations typical of carnivore teeth. The discovery of a plant-eating theropod indicates that these dinosaurs were more diverse that previously thought, and occupied a variety of ecological roles in ecosystems 60 million years ago.

Source: Xu, X., Cheng, Y.-N. Wang, X.-L., and Chang, C.-H. (2002). "An unusual oviraptorosaurian dinosaur from China." Nature, 419: 291-293. For more information, click on the title of today's post.

Dino Dads

Analysis of adult dinosaur bones found near nests of dinosaur eggs suggests that the male dinosaur parent was caring for the eggs.

Paleontologists from Montana State University examined the adult dinosaur bones found by these nests and discovered that they lacked a distinctive layer called medullar bone, a bone type that characterizes many species of female birds and that has been found in other dinosaurs, including Tyrannosaurus and Allosaurus.

If dino dads were in fact caring for their young, this could explain the origin of male parental care that we see in the descendents of these dinosaurs—birds. The large number of eggs found in these dinosaur nests--up to 30—also compares with the clutch size of modern birds in which the dads care for the young.

A reminder that Father's Day is coming up soon!

Summary in sciencenews.org Jan. 17, 2005 (Laura Sanders). Illustration of dino dad from here. Original research article: David J. Varricchio, et al., 2008. Avian paternal care had dinosaur origin. Science 322:1826-1828.

Modeling dinosaur "flight"

An unusual feathered dinosaur discovered in China raises questions about the origin of flight.

Other small dinosaurs have been found with traces of feathers on the front two legs but Microraptor had feathers on the back legs, as well. Its asymmetrical feathers indicate that the animal was capable of gliding or flying, so it assumed that Microraptor made its home in trees and glided, or flew from tree to tree like modern flying squirrels.

To test these ideas, researchers at the University of Kansas constructed a model of Microraptor, using pheasant feather for its wings, and designed a slingshot to launch it. The Microraptor model glided 24 meters, or 26 yards.

Of course, a plastic model with pheasant feathers may not be an accurate model of an extinct feathered dinosaur, but it is a first step in attempting to understand how this unique animal lived.

Summarized in Earth, May, 2009, p. 13 (Emily Lant); research by David Alexander & David Burnham, University of Kansas. Click here for a video of the model's flight!

Original report on Microraptor: Xu, X., Zhou, Z., Wang, X., Kuang, X., Zhang, F. and Du, X. (2003). "Four-winged dinosaurs from China." Nature, 421(6921): 335-340, 23 Jan 2003. http://www.nature.com/nature/journal/v421/n6921/full/nature01342.html

Bulking up on veggies

Sauropod dinosaurs, like Diplodocus and Brachiosaurus, hold the record for the largest land animals, weighing up to 80 tons, and stretching more than 60 meters from head to tail.

To support their size, these herbivorous dinosaurs must have spent most of their time eating and searching for food.

They had a mouthful of incisors, good for clipping off plants, but not designed for chewing. They had no molars for pulverizing their food, so they must have swallowed their food whole.

The giant bulk of these dinosaurs is more puzzling when considering their relatively tiny heads, but their small heads were supported by long necks, which may have been critical to the sauropod’s success.

Their long necks allowed these dinosaurs to stand in one place and browse vegetation from a large radius, allowing them to collect a lot of food without expending much energy.

Based on research by P. Martin Sander and Marcus Clauss, 2008. Sauropod Gigantism. Science 322: 20-201

Illustration from http://www.scorcher.ru/journal/art/art_pic/diplodocus_2.jpg

Thwarting T. rex

How can an herbivore protect itself from carnivorous predators?

Strategies seen today among predators and prey of the African Serengeti apparently existed among dinosaurs in ancient ecosystems.

Paleontologists from Ohio University counted growth lines in the legbones of hadrosaurs, a group of herbivivorous duck-billed dinosaurs. By counting the number and spacing of growth rings, paleontologists can determing the animals’ age and its relative growth rate—the fast growth seen in juveniles is characterized by widely-spaced growth rings; growth slows or stops at adulthood, shown by close spacing of the growth rings.

The scientists found that hadrosaurs reached their adult size by age 13. In contrast, the carnivorous Albertosaurus reached full size at 20-30 years. Maturing quickly gave hadrosaurs an advantage over their predators, as they could produce offspring at an earlier age, and their offspring grew quickly to maturity.

Source: Drew Lee, Royal Society London B, Aug 5, 2008

Filling an empty niche

Despite the occupation by reptiles of almost every ecological niche during the Mesozoic Era, there were no large planktivorous marine reptiles, the niche filled today by baleen whales.

Recent discoveries in museum drawers may hold the answer to this gap in Mesozoic reptile ecology. Fossils that had lain unstudied or incorrectly identified have been newly identified as suspension-feeding pachycormids, a group of giant bony fish.

These fish were previously thought to have been a short-lived group, limited to the Jurassic Period. Mesozoic marine reptiles may have been excluded from the large-bodied, suspension-feeding trophic niche by these supersized fish.

The pachycormids were extinct by the end of the Cretaceous Period, opening up the planktivorous niche to a new group--the whales.

Matt Friedman, et al., 100-Million-year dynasty of giant planktivorous bony fishes in the Mesozoic Seas. Science 327

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

World turned upside-down

Workers with the Paleo Division of New Mexico State Resources recently uncovered a fossil that sent shock waves through the scientific community and that will require the re-writing of textbooks on paleontology, evolution, and the history of life.

Working in the 140 million-year-old Morrison Formation the team discovered a skull and partial skeleton of the dinosaur Allosaurus with a fossil hominid trapped between its gaping jaws.

Of course, this find is evidence that humans and dinosaurs did in fact live at the same time, and it casts doubt on many other aspects of evolution, which of course, is only a theory, anyway. The discovery was announced by Lirpa Loof, which should explain any remaining confusion on the significance of the event.

The full story is at http://www.nmsr.org/Archive.html

Explanation at http://www.nmsr.org/april_fool.html

New Mexicans for Science and Reason http://www.nmsr.org/

First dino from Bulgaria

When it comes to dinosaurs, North America, China, and South America have decided advantages over other countries—they are large and have vast quantities of sedimentary rock deposited in ancient river or floodplain environments during the Mesozoic Era, the age of dinosaurs.

Recently the first dinosaur fossil from Bulgaria was described. It’s no Sue, the most complete T. rex ever found, but a single bone 10 cm long and 5 cm wide interpreted as the left humerous—the upper bone in the forelimb--of a Late Cretaceous Theropod—a European cousin to Sue.

The bone was found in limestone—a sedimentary rock usually deposited in a marine environment, but the isotopic signature of the bone differs from that of the limestone, indicating that the bone was probably transported into the shallow sea after burial and fossilization.

Source: MATEUS, OCTÁVIO; DYKE, GARETH J.; MOTCHUROVA-DEKOVA, NEDA; KAMENOV, GEORGE D.; IVANOV, PLAMEN. The first record of a dinosaur from Bulgaria. Lethaia, Volume 43, Number 1, March 2010 , pp. 88-94(7)

An egg-celent discovery

Every now and then an exceptionally preserved fossil sheds light on the biology of an extinct organism.

One such specimen was the remains of a dinosaur from Cretaceous sedimentary rocks in China. The pelvic area of the dinosaur contains two 17-cm long, potato shaped eggs that were ready to be laid when the dinosaur died.

The two eggs fill the pelvic cavity and are similar in size, suggesting that the dinosaur had two oviducts that simultaneously produced one egg each. Modern reptiles like sea turtles, have two oviducts, but produce multiple eggs; birds have single oviducts and produce only one egg at a time.

The egg-laying behavior of the Chinese combines elements seen in both these modern groups, evidence of a common ancestry in the geologic past.

Science, April 15, 2005. Tamaki Sato. Photo from the article

Discovering Dinosaurs

If it seems that a new species of dinosaur is announced every other week, you are correct.

In recent years new finds in China and Argentina have doubled the number of dinosaurs known from those two countries. Over a 14-year period China added 52 new genera to its list of dinosaurs.

At this rate, are we in danger of running out of new dinosaurs to discover? The experts say no, based on an analysis of the locations the finds are coming from. There are still plenty of strata to explore, and good news for aspiring paleontologists, we have probably only scratched the surface of dinosaur diversity.

Photo credit: http://www.indiaonrent.com/forwards/d/dinosaurs-evolution/res/hd3szn.jpg

Science News 10 Nov. 2004, p. 334

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