Read the text below. Match the headings i-viii to the paragraphs A-H in the boxes 1-7 below.
Although the name dinosaur is derived from I he Crock for “terrible lizard“ dinosaurs were not, in fact, lizards at all. Like lizards, dinosaurs are included in the class Roptilin, or reptiles, one of the five main elasscs of Vertebrata, Einimals with backbones. However, at the next level of classification, within reptiles, significant differences in the skeletal anatomy of lizards and dinosaurs have led scientists to place these groups of animals into two different superorders: Lepidosauria, or lepidosaurs, and Archosauria, or archosaurs.
Classified as lepidosaurs are lizards and snakes and their prehistoric ancestors. Included among the archosaurs, or “ruling reptiles”, are prehistoric and modern crocodiles, and the now extinct thecodonts, pterosaurs anti dinosaurs. Palaeontologists believe that both dinosaurs and crocodiles evolved, in the later years of the Triassic Period (c, 248-208 million years ago), front creatures tailed pseudosuchian thecodonts. Lizards, snakes and different types of thecodont are believed lo have evolved earlier in the Triadic Period from reptiles known as eosuchians.
The most important skeletal differences between dinosaurs and other anchosaurs are in the hones of the skull, pelvis and limbs. Dinosaur skulls are found in a great range of shapes and sixes, reflecting the different eating habits anti lifestyles of a large and varied group of animals that dominated life on Earth for an extraordinary 165 million years. However, unlike the skulls of any other known animals, the skulls of dinosaurs had two long bones known as vomers. These bones extended on either side of the head, from the front of the snout to the level of the holes in the skull known as the antorbital fenestra, situated in fro ill of the dinosaur’s orbits or eyesockets.
All dinosaurs, whether large or small, quadrupedal or bipedal, fleet -footed or s low-moving, shared a common body plan. Identification of this plan makes it possible to differentiate dinosaurs from any other types of animal, even other archosaurs. Most significantly, in dinosaurs, the pelvis and femur had evolved so that the hind limbs were held vertically beneath the body, rather than sprawling out to the sides like the limbs of a lizard. The femur of el dinosaur hutl a sharply in-turned ncck and a halt-shaped bead, which slotted into a fully open acetabulum or hip socket. A supra-acetabular crest helped prevent dislocation of the femur. The position of the knee joint, aligned below the acetabulum, made it possible for the whole hind limb to swing backwards and forwards. This unique combination of features gave dinosaurs what is known as a “fully improved gait”. Evolution of this highly efficient method of walking also developed in mammals, but among reptiles it occurred only in dinosaurs.
For the purpose of further classification, dinosaurs are divided into two orders: &iurisehia, or saurischian dinosaurs, and OrnithIschia, or ornithiscluati dinosaurs. This division Is made on the basis of their pelvic anatomy- All dinosaurs bad el pelvic girdle with each side comprised of three hones: the pubis, ilium and ischium. However, ihc orientation of these bones follows one of two patterns In saurischian dinosaurs, also known as lizard-hipped dinosaurs, the pubis points forwards, as is usual In most types of reptile, By contrast, In oruithisehian, or bird-hipped, dinosaurs, the puhls points backwards towards the rear of tEic animal which is also true of birds.
Of the two orders of dinosaurs, the Stiurischia was the larger mid the first to evolve, It is divided into two suborders: Therapoda, or therapods, and Sauropodomorpha, or sauropodomorphs. The therapods, or “beast feet”, were bipedal, predatory carnivores. They ranged in size from the mighty Tyrannosaurus rex, 12m long, 5.6m tall and weighing an estimated 6.4 tonnes, to the smallest known dinosaur, Compsognathus, a mere 1,4m long and estimated 3kg in weight when fully grown. The sauropodomorphs, or “lizard feet forms”; included both bipedal and quadrupedal dinosaurs. Some sauropodomorphs were carnivorous or omnivorous but later species were typically herbivorous. They included some of the largest and best-known of all dinosaurs, such as Diplodocus, a huge quadruped with an elephant-like body, a long, thin tail and neck that gave it a total length of 27m, and a tiny head.
Ornithischian dinosaurs were bipedal or quadrupedal herbivores, They are now usually divided into three suborders: Ornithipodu, Thyrcopborii and Margmoccphalia. The ornithopods, or “bird feet1’, both large and small, could walk or run on their lung hind legs, balancing their body by holding their tails stiffly off the ground hchind them. An example is Iguanodon, up to 9m long, 5m tall and weighing 4.5 tonnes. The thyreophorans, or “shield bearers”, also known as armoured dinosaurs, were quadrupeds with rows of protective bony spikes, studs, or plates along their backs and tails. They included Stegosaurus, 9m long and weighing 2 tonnes.
The margirtucephalians, or “margined heads”j were bipedal Or quadrupedal omithischians with a deep bony frill or narrow shelf at the back of the skull. An example is Triceratops, a rhinoceros-like dinosaur, 9m long, weighing 5,4 tonnes and bearing a prominent neck frill and three large horns.
List of headings
I. 165 million years
II. The body plan of archosaurs
III. Dinosaurs – terrible lizards
IV. Classification according to pelvic anatomy
V. The suborders of Saurischia
VI. Lizards and dinosaurs – two distinct superorders
VII. Unique body plan helps identify dinosaurs from other animals
VIII. Herbivore dinosaurs
X. Prills and shelves
XI. The origins of dinosaurs and lizards
XII. Bird-hipped dinosaurs
XIII. Skull bones distinguish dinosaurs from other archosaurs
Example: Paragraph H Answer: x