Image: Triceratops and mammals
Mark Hallett
In this artist's conception, three small primitive mammals walk over the skeleton of a Triceratops, one of the last dinosaurs to exist before the mass extinction that gave way to the age of mammals.
By Contributor
updated 7/12/2011 7:47:50 PM ET 2011-07-12T23:47:50

A dinosaur horn is now pointing to a catastrophic end for the Age of Dinosaurs, not a gradual one as some researchers have claimed.

The leading culprit for the end of the Age of Dinosaurs is a catastrophic meteor strike about 65 million years ago. Although it is now widely accepted that a cosmic impact took place about then — a time known as the Cretaceous-Tertiary, or K-T boundary — it was unclear if the mass extinctions started gradually before the hit, perhaps due to volcanoes or other factors.

Helping drive this controversy was a zone spanning 10 feet (3 meters) wide in the earth right below the K-T boundary that purportedly lacked dinosaur fossils. A number of scientists have claimed this gap, seen in the western interior of North America, was evidence that dinosaurs might have died off well before any impact. Other researchers have contested the notion, suggesting this layer only appeared devoid of fossils because fossils can get easily destroyed over millions of years. Also, the placement of the K-T boundary can be uncertain, meaning that dinosaurs might have actually been found in this zone before but not reported as such. [Image Gallery: Dinosaur Fossils]

  1. Science news from NBCNews.com
    1. NOAA
      Cosmic rays may spark Earth's lightning

      All lightning on Earth may have its roots in space, new research suggests.

    2. How our brains can track a 100 mph pitch
    3. Moth found to have ultrasonic hearing
    4. Quantum network could secure Internet

Now scientists have discovered a fossil in this supposedly barren zone — a dinosaur horn no more than 5 inches (13 centimeters) below the impact layer, making it the specimen closest to the end of the Age of Dinosaurs found yet. The horn, nearly 18 inches (45 cm) long, most likely belonged to a Triceratops, the most common dinosaur in the layer of rock in which it was found last year, called the Hell Creek Formation of southeastern Montana.

Just because "we have one dinosaur in the gap doesn't necessarily falsify the idea that dinosaurs were gradually declining in numbers," researcher Tyler Lyson, a vertebrate paleontologist at Yale University, told LiveScience. "However, this find indicates that at least some dinosaurs were doing fine right up to the K-T boundary."

"We need to do more field work to find more dinosaurs within the 3-meter gap," Lyson said. "I'm confident that with more field work, we will find more dinosaurs within this interval."

The scientists detail their findings tomorrow (July 13) in the journal Biology Letters.

Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

© 2012 LiveScience.com. All rights reserved.

Interactive: Are dinosaurs alive?

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.

Discuss:

Discussion comments

,

Most active discussions

  1. votes comments
  2. votes comments
  3. votes comments
  4. votes comments