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Archive for the ‘Paleobiology’ Category

 

Ever since its discovery, Tyrannosaurusrex, paleontologists and laypeople have been mesmerized by the sheer enormity of this giant carnivore. Every time a new discovery or debate concerning T-rex pops up, it attracts fans from every field; very few historical things have enjoyed such phenomenal popularity – the Titanic, the Pyramids etc are a few on the list.

T-rex has been bestowed with the titles of the most ferocious animal that ever walked the earth and the largest predator on land. But is the story of T-rex, a bit over-hyped? Is it worth these titles any longer?

 

New evidences on the predatory behaviour of dinosaurs are coming up, thanks to the bionic technology that uses computer simulations merging paleontological findings with physics of animal body.

Why is this tyrant-lizard so popular?

 

The first Tyrannosaurus rex fossil was discovered by Barnum Brown in 1902. By the time T- rex was named by Henry Osborn in 1905, news about this strange and seemingly formidable “predator” was out and names that captured the popular fantasy of a “dragon” like ferocious lizard became a necessity. (Dynamosaurus imperiosus, was a synonymous name Osborn later suggested for Tyrannosaurus !). T-rex soon was seen as the materialization of the mythological dragon; the ultimate killing machine. And Hollywood was quick enough to take this fantasy to its extremes, Jurassic Park being the ultimate reference.
After all that popular appeal and fan-following, its now become difficult for both scientists and the masses to see T-rex as a huge, awkward, lumbering beast that waddled out of the bushes to pick off the remains of a carcass.

 

Not the largest predator.

T-rex now has only the fourth position with regard to size among predatory land animals, Spinosaurus being the first, Giganotosaurus being the second and Carcharodontosaurus being the third. Discussions and comparisons on the predatory capabilities of these four dinos had heated up the paleobiology circles recently; the debate is still on. Spinosaur, as depicted almost correctly in Jurassic park III, is currently the largest carnivore. But compared to T-rex, the other three dinos had weaker build and teeth designed for slicing up flesh. T-rex brain case is larger, has solid teeth to crush bones, and supposedly has a better build.

 

These points gave T-rex an edge over the others and T-rex fans finally had some reason for consolation.

 

Stiff spine, sharp senses : hyena or lion ?

 

Then came the expositions about the spine. A US team has used detailed computer models to work out the weight of a typical “king of the dinosaurs”, and determine how it ran and turned. The results indicate a 6 to 8-tonne T. rex was unlikely to have topped 40km/h (25mph) and would take a couple of seconds to swivel 45 degrees. The study indicates the animal would have changed direction incredibly slowly because of its massive inertia, taking more than two seconds to make a quarter-turn. The species certainly could not have pirouetted rapidly on one leg, as popular illustrations have sometimes pictured it, and other large dinosaurs, doing. The more agile prey would have given the slip to a marauding T. rex quite easily, it seems.
A massive blow to the “predatory” nature!

 

But that wasn’t the end of controversial findings. Dr. Lawrence Witmer, from Ohio University, used the medical scanning technique of computed tomography (CT scanning) to reconstruct the shape of the animal’s brain, including its inner ear, which is involved not only in hearing but also body-balance.

 

T. rex has the inner ear comparable to that of a much smaller, very agile animal. It had a heightened sense of equilibrium and balance and employed rapid turning movements of its eyes and head to track its prey.

 

But Dr. Jack Horner, the leading scientist who supports the “Scavenger T-rex” theory, carried out microscopic analysis of the dinosaur’s vertebrae. His team found tissue remnants related to the animal’s nuchal ligament, which provides passive support for the head and neck. The study also points at how rigid it was from the neck all the way back to the tail.

 

The teeth that crush bones are typical of a scavenger… the puny fore-legs are very unlikely evolutionary weapons for a hunter…the extraordinarily latge olfactory lobes of the T-rex brain is typical of a scavenger that sniffed for its food…the massive hind legs are those of a walker, not a sprinter….thus goes the evidence against the “hunter T-rex” theory.

 

We like our T. rex to be the monster from hell, threatening to rip the heads off poor, screaming kids when their jeep gets stuck in Jurassic Park. But evidences are throwing light on a scavenger-lizard now, claims Dr Jack Horner.

 

The simplest way to come to terms with this new reality is to compare an ideal predator like the Velociraptor or the Cheetah with T-rex and see the voids for yourself.

 

“We want people to do what scientists do, which is to take all that in, think about it, and then come to a conclusion….my own view is that the truth lies somewhere in the middle. We know it wasn’t a fast-running creature like a cheetah, but I certainly think it would have been capable of killing a small, old or weak animal.” says Horner.

 

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A new bird from the family of Oviraptors (the egg-stealers among dinos) has been discovered by paleontologist Xing Xu and team of the Beijing’s Institute of Vertebrate Paleontology and Paleoanthropology in the Gobi Desert in north-central China.

 

Initially thought have belonged to the T-rex family (see artists scale- drawing), this giant “bird of prey” is now grouped under the family of smaller raptors – an unusual reunion.!

 

The finding complicates the evolutionary descent of birds from dinosaurs. Progressively from within advanced theropods as you come to birds, their size gets smaller and smaller. But after some species originate and spring off the bird line, you get secondary gigantism.

“Big size has some advantages such as having fewer predators and having more food resources that are unavailable for small animals,” Xu notes. He is joined by Thomas R. Holtz Jr., a vertebrate paleontologist at the University of Maryland at College Park who adds “ Gigantoraptors grew muc h faster and reached adulthood more quickly than did tyrannosaurs. There was an incentive [for such a creature] to get big really soon” Size is certainly a defense. And there is ample evidence to believe that these giant-birds lived at a time when T-rex ruled the earth.

The length and proportions of Gigantoraptor’s leg bones hint at another of the dinosaur’s survival skills – its speed. The bird-like femur suggests it would have been among the fastest dinosaurs of its body size.

It also is not clear whether the creature was feathered, though Xu speculates it was like most other animals in its lineage. If so, it would be by far the largest known feathered animal of all time.

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