Extinct land reptile(reptil
de tierra) of the Mesozoic era . The dinosaurs, which were
egg-laying animals(animales
que ponían huevos), ranged in length(cuya
longitud oscilaba) from 2 1/2 ft (91 cm) to about 127 ft (39
m). Recognized discoveries(descubrimientos)
of fossilized dinosaur bones(huesos)
date(proceden, están
fechados) only to the 1820s; Sir Richard Owen, a Victorian
anatomist, coined(acuñó)
the term(término)
dinosaur.
Many explanations(explicaciones)
have been offered for the worldwide(en
todo el mundo) extinction of the dinosaurs after 160 million
years of existence.
The most popular theory is that one or more asteroids or comets hit(golpearon)
the earth, lifting(levantando)
massive amounts(cantidades)
of debris(escombros)
and sulfur in the air and blocking the sunlight from reaching the earth's
surface. The 1991 discovery of the Chicxulub crater on the Yucatán peninsula
in Mexico lent support(prestó
apoyo, apoyó) to this idea.
The second currently(actualmente)
popular theory is that the extinctions followed(siguieron
a) the huge volcanic eruptions that created the lava flows of
the Deccan Traps in what is now India. (See mass extinction(extinción
masiva) for more information.)
No theory perfectly describes why dinosaurs, pterosaurs, and many marine
organisms were affected by the extinction, when many mammals(mamíferos)
and other animals (e.g., turtles and crocodiles) survived. |
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