How did bird-like carnivorous dinosaurs lose their fingers?



Johannesburg, 24 August (IANS) An international team of paleontologists has discovered that a carnivorous species of dinosaurs, which have many similarities with birds, have lost their fingers.

The fossils of "Xiyunykus pengi" and "Bannykus wulatensis", discovered in China, are a mysterious group of theropods known as alvarez saurians.

Their bodies appeared to be slender, with a bird-like skull and many small teeth instead of the usual large, sharp teeth of their carnivorous family members.

"Alvarezsaurs are weird animals, with their strong, clawed hands and weak jaws they seem to be the dinosaur analogue to the aardvarkens and anteaters of today," said Jonah Choiniere, associate professor at Wits University in South Africa.

However, "the new fossils have long arms and show that alvarezsaurians developed short arms only later in their evolutionary history, in species with small body sizes.This is very different from what happens in the classic example of tyrannosaurs, who have short arms and gigantic size, "said co-author Professor Roger Benson of Oxford University in Great Britain.

According to the researchers, the alvarez saurians did not always look like this. Early members of the group had relatively long arms with strongly clawed hands and typical carnivorous teeth. Over time, they evolved into dinosaurs with mole-like arms and a single claw.

Bannykus and Xiyunykus are important because they show transitional steps in the process of alvarez sauruses that adapt to new diets, according to the researchers, in the article in the journal Current Biology.

The new Alvarezsaurian dinosaurs are among the most bizarre groups of theropods, with extremely short, robust front legs with a single functional claw and gracile, birdlike skulls and hind limbs.

These specializations led to a controversy about their phylogenetic placement, biogeographical history and ecological role in Mesozoic ecosystems, the team noted.

– IANS

rt / anp / mag / sed


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