A New Species Of Troodontid Dinosaur From Cretaceous Era Utah

A reconstruction of Talos sampsoni with the known skeletal element shown in red

Troodontid dinosaurs are a group of reptiles that lived from the late Jurassic to the late Cretaceous. These dinosaurs were small. Some were covered in feathers, some were scavengers while others were true hunters. They are mainly known from incomplete or fragmentary remains. However palaeontologists have recently discovered a troodont skeleton which is, like many dinosaur skeletons before it, known from a few bones, yet it is a completely new species.

The 75 million year old fossil, named Talos sampsoni, was discovered in 2008 by Michael.J.Knell of the University of Utah at the Kaiparowits Formation in the Grand Staircase Escalante National Monument, Utah. The species name was given by Lindsay.E.Zanno, David.J.Varricchio, Patrick.M.O'Conor, Alan.L.Titus and Michael.J.Knell in honour of the palaeontologist Scott.D.Sampson, who frequently collected from the Kaiparowits Formation. However its species name is rather more interesting as it hints at its morphology.

The sickle shaped, switch-blade claw of Talos sampsoni

The team's current estimates, based upon leg weight ratios, show that the creature was around 2 metres long and weighed around 38 kilograms, making it around the size of a human. The name Talos is derived directly from the ancient Greek name for a giant bronze automaton which could run at the speed of lightning. It is also a pun of the word talon, due to the large sickle shaped fore-finger which it would have used to latch onto prey. A scan of the holotype specimen's claw shows that it was damaged, possibly by a bite, and then it succumbed to a localised infection.

If the infection had prevented it from using its claw, then it would have had great difficulty feeding. The claw itself is connected to an elaborate structure composed of tendons, which makes its action similar to a flick knife or switch-blade. This would have kept the claw safe when not in use. It remains uncertain what Talos might have eaten. 'Many are still debating over what its relatives ate,' Zanno said. 'My recent research suggests it was probably either a carnivore or an omnivore, eating some degree of prey.'

Talos lived in a warm greenhouse world devoid of polar ice caps. In what is now North America, a shallow seaway ran from the Gulf of Mexico through to the Arctic Ocean dividing the continent into two landmasses, East America or Appalachia, and West America or Laramidia, for several million years. 'The area was basically the complete antithesis of what it is now,' Zanno said. While the area is now quite dry, then it was an extremely wet, very lush environment, almost swampy; regularly bombarded by massive storms coming in off the seaway dividing North America.