D) S Use the following paragraph for questions 24-27 Fossils of Lystrosaurus , a
ID: 270463 • Letter: D
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D) S Use the following paragraph for questions 24-27 Fossils of Lystrosaurus , a dicynodont therapsid, are most common in parts of modern-day South America, South Africa, Madagasca India, South Australia, and Antarctica. The animal apparently lived in arid regions, and was mostly herbivorous. It originated during the mid-Permian period, survived the Permian extinction, and dwindled by the late Triassic, though there is evidence of a relict population in Australia during the Cretaceous period. Some dicynodonts had two large tusks, extending down from their upper jaws The tusks were not used for food gathering, and in some species were limited to males. Food was gathered using an otherwise toothless beak. Judging from the fossil record in sedimentary rocks, these pig-sized organisms were the most common mammal-like reptiles of the Permian. 24.) Which features of Lystrosaurus helps explain why these organisms fossilized so abundantly? I. the presence of hard parts, such as tusk II. its plant-eating diet III. its persistence across at least two geological eras IV. its widespread geographic distribution V. its mixture of reptilian and mammalian features. A) I and III B) III and V C) II, II1, and V D) I, III, and IV 25.) The observation that tusks of Lystrosaurus were limited to males in several species, and were apparently not used in food- gathering, is evidence that the tusks probably A) served to dissipate heat B) were maintained as a result of sexual selection C) were not significant to the survival and/or reproduction of these dicynodonts D) are homologous to the horns on a rhinocerosExplanation / Answer
24. (D) I , III & IV
25. (B) were maintained as a result of sexual selection
26. (A) Genetic drift
27. (B)
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