Torosaurus perforated lizard .

Описание: Torosaurus ("perforated lizard", in reference to the large openings in its frill) is a genus of ceratopsid dinosaur that lived during the late Maastrichtian stage of the Cretaceous period, between 66.8 and 65.5 million years ago.[1] Fossils have been discovered across the Western Interior of North America, from Saskatchewan to south Texas. Torosaurus possessed one of the largest skulls of any known land animal. The frilled skull reached 2.6 metres (8.5 ft) in length. From head to tail, Torosaurus is thought to have measured about 9 m (30 ft) long[1] and weighed 4 to 6 tonnes (4.4 to 6.6 tons). Torosaurus is distinguished from the contemporary Triceratops by an elongate frill with large openings (fenestrae), long squamosal bones of the frill with a trough on their upper surface, and the presence of five or more pairs of hornlets (epoccipitals) on the back of the frill.[citation needed] Torosaurus also lacked the long nose horn seen in Triceratops prorsus, and instead resembled the earlier and more primitive Triceratops horridus in having a short nose horn.[citation needed] Two species have been named, Torosaurus latus and T. gladius. T. gladius is no longer considered a valid species, however.

Recently[2] the validity of Torosaurus' has been disputed. A 2010 study of fossil bone histology concluded that Torosaurus probably represented a mature form of the Triceratops, with the bones of Triceratops specimens still immature and showing signs of the development of the Torosaurus's distinct frill holes.[3][4][5] 2011 and 2012 studies of external features of known specimens, however, claim that external morphological differences between the two genera preclude their synonymy.[6][7]