ESL, pažengęs lygis
Mammoths and Mastodons
Nothing is more exciting to a ......... than the discovery of animal bones from a previous era, in particular the awe-inspiring excavation of skulls and tusks of mammoths.
Such was the exhilaration when 58 Columbian mammoth remains were found in a sinkhole, about the size of a regulation size basketball court, in 19 75. Scientists ......... that just as many or more were buried beneath the ground in the South Dakota hills.
Paleontologists speculate that a herd was attracted to the vegetated area, created from the ideal conditions of water from a hot spring, ......... from a sinkhole. Tempted by the allure of abundant food and water, the mammoths fell into the cavernous opening and were unable to get back up the slick walls.
The revelation of this find also brought enthusiastic visitors to the site, resulting in the erection of The Mammoth Site museum. Here tourists can view ......... skeletons beneath a roof, built to protect the site from natural elements, while watching the continual excavation.
Occasionally, a visitor will express astonishment at the find, associating mammoths and mastodons only with Siberia. In fact, Columbian mammoths ......... from coast to coast in the U.S., Alaska, and in some parts of South America. Paleontologists believe half as many mastodons may have roamed the same areas
Some ......... "digs" go back as far as 1705, when a farmer, plowing his field, dug up a 5 pound tooth of an unknown species. Slaves in South Carolina showed a similar tooth, and bones found in the cotton fields, to the owner of the plantation.
Research since the late 1800's has disclosed both mammoths and mastodons wandered across the U.S. plains; hardly anyone was able to make a distinction between the two ..........
However, European anatomists made charts to compare each ......... to determine the precise differences, beginning with a comparison of teeth.
They discovered that the teeth of mammoths and mastodons were remarkably similar, with both having irregular ......... on the surfaces, much like grooved cardboard, while the teeth of mastodons had sharp conical-shaped cusps.
Scientists concluded from this one study that because Mammoths were mainly found in grasslands, it was logical that the teeth would have been flat for grinding grass. Mastodons, on the other hand, had sharp teeth and were ......... flesh-eaters.