More than 350 newly discovered tracks made by various dinosaurs, crocodiles and a few pterosaurs, have been identified at the site of the Dinosaur Freeway in Colorado. Many beasts, such as these sauropods, migrated widely to satisfy their gargantuan appetites.
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updated 1/5/2012 2:45:42 PM ET 2012-01-05T19:45:42

Colorado’s bustling thoroughfare 98 million years ago was the Dinosaur Freeway.

More than 350 newly discovered tracks, made by various dinosaurs, crocodiles and a few pterosaurs, were identified at the site, which is now the John Martin Reservoir in Bent County, Colorado. When added to previously found tracks there, the total number of fossilized prints is well over 1,000. The dinosaur freeway is described in the February issue of Cretaceous Research.

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"The Dinosaur Freeway runs from Northeast Colorado, near Boulder, to east central New Mexico, near Tucumcari," co-author Martin Lockley told Discovery News. "It is a trampled zone in Cretaceous rocks representing an ancient coastal plain like the present day Gulf of Mexico."

Reiji Kukihara and Martin Lockley
The Dinosaur Freeway area in Colorado.

Lockley is a professor of geology at the University of Colorado Denver and serves as director of the Dinosaur Tracks Museum. He and colleague Reiji Kukihara found and analyzed the animal tracks.

An ornithopod dinosaur that was probably an Iguanodon-like species made the most common prints. Iguanodons were bulky, large, plant-eating dinosaurs, with some having large thumb spikes that were possibly used for defense against predators.

Based on the prints, other travelers along the Dinosaur Freeway included armored Ankylosaurs and ostrich-like dinos that were probably ornithomimids.

"Sometimes the ornithopod dinosaurs appear to have walked in herds," Lockley said. "Their trackways are parallel and equally spaced, and sometimes they all belong to individuals of similar size."

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Swim tracks for large crocodiles, some over 13 feet long, were also found near the Dinosaur Freeway.

Lockley explained that, back in the dino day, the freeway was the coastal plain to the Cretaceous Western Interior Seaway, which ran north to south and split North America during this period of time.

"It was riddled with waterways and wetlands ideal for crocs," he said. "The crocs were not wimpy."

Dinosaurs therefore probably sped on by, likely migrating to find new forage. The animals may have traveled in groups by age. Juvenile and subadult dinosaurs were more dominant in the south, accounting for almost half of all identified tracks in that region. The proportion of juveniles sharply reduces in the middle area, and almost disappears in the north.

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Lockley shared that other similar dinosaur thoroughfares have been discovered in Utah and Switzerland, both dating to the Jurassic Period.

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"They mainly show that dinosaurs roamed very freely and for long distances along coastal plains," he said.

Spencer Lucas, curator of paleontology at the New Mexico Museum of Natural History and Science, told Discovery News that he believes "the conclusions of this article make eminent sense. They follow up on decades of careful research by Lockley and his collaborators on the track sites of what he calls the "Dinosaur Freeway."

Lucas added, "Significantly, the rocks in question yield very few fossil bones, so what we know about the extinct ecosystem — dinosaurs, pterosaurs, etc. — comes to us from the footprint record."

Lockley and Kukihara hope that future investigations will reveal even more tracks, helping to shed further light on the freeway and dinosaur behavior during the Cretaceous.

© 2012 Discovery Channel

Explainer: The world's seven deadliest dinosaurs

  • Copyright 1985 Mark Hallett, "Awakening of Hunger"

    Yeah, it's cliche to say Tyrannosaurus rex was deadly. But the tyrant king was likely true to the billing. Its bone-crushing jaws could splinter prey like toothpicks, after all. And the beast was big, up to 40 feet long, 20 feet tall, and may have topped the scales at nearly 16,000 pounds.

    The king walked on two legs over a vast territory in western North America at the end of the Cretaceous, about 65 million years ago. Scientists wonder whether T. rex was more a lumbering scavenger or a quick and agile predator, but dead or alive, its meals were big, meaty and bloody.

    T. rex wasn't the only deadly dino, however. The globe was filled vicious killers. Click the arrows above to see more.

    — John Roach, msnbc.com contributor

  • Family diner

    Demetrios M. Vital

    Family meals for Majungasaurus crenatissimus were often bloody affairs of the grimmest sort: Kin were the main course. The evidence of its cannibalistic ways comes from telltale tooth marks on Majungasaurus bones that match up perfectly with the size and spacing of teeth in its jaws.

    The 20-foot-long dinosaur stalked the plains of Madagascar about 70 million years ago. At that time, the crime-scene investigators said, pickings were often slim. Their data indicate Majungasaurus fed on dried out "dino jerky" from its plant-eating compatriots as well as members of its own species. Cannibalism was likely just as common among dinosaurs as it is among living animals, but the evidence is rare.

  • Brow beater

    Todd Marshall

    Eocarcharia dinops' brow was swollen into a massive band of bone. The menacing head piece may have been used as a battering ram against rivals and to attract potential mates. Its blade-shape teeth were reserved for disabling live prey and severing their body parts.

    The 110-million-year-old beast and its snout-nosed, gut-and-carcass-scavenging relative Kryptops palaios were discovered in Africa's Sahara Desert. The approximately 7-foot-tall and 25-foot-long duo likely teamed up with a third carnivore and feasted on the long-necked plant-eater Nigersaurus.

  • Vicious rocker

    Parsons

    The toothy Masiakasaurus knopfleri likely speared prey with its forward projecting front teeth and then sliced and tore the captives into chewy chunks with its bladelike rears. This type of tooth arrangement is otherwise unknown in predatory dinosaurs.

    Scientists believe the German Shepherd sized beast feasted on fish, lizards, and other critters on the southern supercontinent Gondwana in the Late Cretaceous period, about 65 to 70 million years ago.

    The first part of this dinosaur's name means "vicious lizard" and the second part is derived from the Dire Straits singer and guitarist Mark Knopfler, whose music inspired the discoverers as they toiled on the African island nation of Madagascar.

  • Biggest carnivore?

    Prof. Rodolfo Coria / Ap

    At about 40 feet long and weighing an estimated 6 tons, Mapusaurus roseae was one of the biggest meat-eating dinosaurs to ever stalk the Earth. Bones of several individuals were discovered in one place, suggesting the giants may have hunted in packs that could have toppled perhaps the largest dinosaur that ever lived — a 100-foot-long plant eater called Argentinosaurus.

    Mapusaurus lived about 100 million years ago and was bigger than well known Tyrannosaurus rex and possibly larger than its older cousin, Gigantosaurus. Its teeth were narrow and blade like, made for slicing its prey. The bones were discovered in the Patagonia region of Argentina.

  • Going green

    MWS

    Falcarius utahensis is the living image of a vicious meat eater trying to go vegetarian. Scientists aren't sure if the bird-like relative of Velociraptor had fully kicked its taste for flesh, but its meat-cutting teeth had shrunk to leaf-cutting size and its gut had expanded sufficiently to ferment plants.

    Falcarius walked on two legs and stood about 4.5 feet tall. Head to tail, it was about 13 feet long and wielded sharp, curved, four-inch long claws — perhaps to grab a bite when it fell off the wagon? The dinosaur lived during the Early Cretaceous, about 125 million years ago, in what is today Utah.

  • Plant ripper

    utah.edu

    No plants were safe from Gryposaurus monumentensis, a big boned, duck-billed dinosaur that could have eaten any vegetation it stumbled across. Its massive skull packed more than 300 teeth for slicing up fibrous greens. Hundreds more replacement teeth rested in its jawbone for the call-up to action.

    The dinosaur lived in the Late Cretaceous, about 75 million years ago on the western side of a giant, shallow ocean that split North America at that time. The plant-munching beast may have reached 30 feet long as an adult and had a 3-foot-long head.

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