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Squirrels are familiar to almost everyone. More than 200 squirrel species live all over the world, with the notable exception of Australia.
The tiniest squirrel is the aptly named African pygmy squirrel—only five inches (thirteen centimeters) long from nose to tail. Others reach sizes shocking to those who are only familiar with common tree squirrels. The Indian giant squirrel is three feet (almost a meter) long.
Like other rodents, squirrels have four front teeth that never stop growing so they don't wear down from the constant gnawing. Tree squirrels are the types most commonly recognized, often seen gracefully scampering and leaping from branch to branch. Other species are ground squirrels that live in burrow or tunnel systems, where some hibernate during the winter season.
Ground squirrels eat nuts, leaves, roots, seeds, and other plants. They also catch and eat small animals, such as insects and caterpillars. These small mammals must always be wary of predators because they are tasty morsels with few natural defenses, save flight. Sometimes groups of ground squirrels work together to warn each other of approaching danger with a whistling call.
Tree squirrels are commonly seen everywhere from woodlands to city parks. Though they are terrific climbers, these squirrels do come to the ground in search of fare such as nuts, acorns, berries, and flowers. They also eat bark, eggs, or baby birds. Tree sap is a delicacy to some species.
It comes from fossil-rich amber deposits discovered in the Aragon region of northeastern Spain about seven years ago .
According to the authors, the new find is not only the oldest but also the first known substantial fossilized section of spider web.
The partial web includes 26 strands of silk, some of them joined by cross links, Grimaldi says, which are typical of orb-weaving spider webs.
The only sample comparable to the find is a piece of Lebanese amber 130 million years old that holds a single strand of spider silk.
Both specimens formed during the early Cretaceous period, a time when creatures such as iguanadons were on the scene but well before the arrival of Tyrannosaurus rex.
While there was no spider present in the latest find, the amber did contain a mite, a beetle, a leg from a wasp, and a fly caught by the spider's silk.
The discovery, Grimaldi says, helps researchers understand the evolution of both spiders and their prey.
For example, a long history of hanging webs would mean spiders have been influencing the evolution of flying insects for millions of years.
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