Less time separates us from Tyrannosaurus rex than separated T. Consider how much life has changed in the past 66 million years. Saber-fanged, knobbly-headed herbivores such as Uintatherium , lemur-like primates called adapiforms , razor-jawed carnivores known as creodonts and many other strange forms proliferated and disappeared.
Even lineages familiar to us today, such as horses, rhinos and elephants, evolved and diversified and are now represented by just remnants of what once existed. The time between the last Triceratops and now has seen radical evolutionary changes. Now think of the 83 million years between the Jurassic and Cretaceous titans.
During that time, the first flowering plants bloomed; the fish-like ichthyosaurs disappeared as plesiosaurs and mosasaurs became the predominant predators of the seas; vast herds of hadrosaurs and ceratopsids occupied places once dominated by sauropods; tiny tyrant dinosaurs transformed into apex predators, and early birds established themselves in ever-greater variety alongside their dinosaurian kin.
For perspective, the later-arriving T. This deadly combo probably equipped Allosaurus to take down their fair share of hefty creatures, including, perhaps, the spiky-tailed Stegosaurus. Assigning specimens to the Allosaurus family tree has long been a point of contention in the field, according to a statement. While some have argued that as many as 12 separate species exist, the new study recognizes only two— A.
Both were top predators in their respective ecosystems and represent some of the best-known dinosaurs in paleontology. But the older A. Allosaurus feasted mostly on large herbivore dinosaurs, and paleontologists have long thought the dinosaur tussled with Stegosaurus.
In , paleontologist C. Gilmore described three Stegosaurus tail spikes that broke or became malformed during the dinosaur's life, suggesting it whacked other dinosaurs hard enough to break its spikes, Mossbrucker told Live Science. More recently, researchers have unearthed more direct evidence of these epic battles. For instance, paleontologists have found an Allosaurus tail vertebra with a puncture wound that matches the shape of a Stegosaurus tail spike, and a Stegosaurus neck bone bearing a U-shaped bite mark that corresponds to the shape of Allosaurus jaws, according to a paper published in The Carnivorous Dinosaurs Indiana University Press, At the annual meeting of the Geological Society of America, Mossbrucker and his colleagues reported an allosaur pelvis bone stab wound that was in the conical shape of a stegosaur tail spike.
The bone showed no evidence of healing , suggesting the stab wound was fatal to the carnivore, Mossbrucker said. Allosaurus was capable of killing healthy medium-sized sauropods long-necked herbivores or large sauropods, such as Apatosaurus , that were sick or injured. It was a fierce and aggressive predator, as indicated by the tooth marks discovered on the vertebrae of an Apatosaurus. The dinosaur may have been able to take on a healthy, fully grown Apatosaurus if it hunted in packs, though it's debated whether the dinosaurs could cooperate in this fashion they may have been aggressive towards each other.
Like T. Despite its large skull, Allosaurus had a bite that was weaker than alligators, lions and leopards, a study in the journal Nature found. Because of this, some researchers believe the dinosaur may have used its skull as a hatchet, slamming its upper jaws into its prey and then tearing out flesh with its slashing teeth.
A study in the journal Palaeontologia Electronica found the dinosaur was capable of the head and neck movements necessary for this type of feeding, and further suggested that Allosaurus stripped meat from carcasses by pulling its head straight up and back, similar to the way small falcons feed.
This specimen offered just a few fragments of the dinosaur. Marsh went on to name other, seemingly unique dinosaur specimens, which, with time, were discovered to also be Allosaurus fossils, causing quite a bit of confusion in the early documentation of this dinosaur.
A more complete Allosaurus skeleton was discovered in by H.
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