24 Nisan 2013 Çarşamba

State Fossil of Pennsylvania

State Fossil of Pennsylvania

Trilobite (common name)
Phacops rana
(scientific name)
Phacops rana is a species of trilobite that lived in the middle Devonian period of the Paleozoic era, approximately 365 to 405 million years ago. Trilobites are extinct marine arthropods, a phylum that includes modern crabs, horseshoe crabs, lobsters, scorpions, centipedes, spiders, and insects.
Phacops rana inhabited the bottom of the sea that covered most of present-day North America. In the Devonian period, North America was attached to the African tectonic plate, making trilobite fossils common in the northeastern United States, southwestern Ontario, and Morocco. Because trilobites shed their exoskeletons several times in a lifetime, and because these hard outer shells fossilized easily, trilobite fossils are fairly abundant.
Phacops rana is found in Devonian-age rocks and sediments in Pennsylvania. Following a proposal from an elementary school class, a bill was passed on December 5, 1988, designating Phacops ranathe Pennsylvania state fossil.
Because trilobites shed their exoskeletons several times in a lifetime, and because these hard outer shells fossilized easily, trilobite fossils are fairly abundant in what is now the northeastern United States, southern Ontario, southern Quebec, and northwestern Manitoba. The largest known species of trilobite is Isotelus rex.
The word trilobite means "three-lobed" and comes from the Greek words τρία (tria) and λοβός (lobos). This refers to the three general divisions of a trilobite’s body. The word "arthropod" comes from the Greek words αρθρον (arthron), meaning "joint," and ποδός (podos), meaning "foot," referring to an arthropod’s jointed appendages.
The genus name Phacops is derived from the Greek word φακός (fakos), which means "lens." The species name rana (Latin for "frog") refers to the organism’s eyes, which resemble those of a frog.
Like all arthropods, Phacops rana had an exoskeleton, a segmented body, and jointed appendages. Phacops rana protected itself by rolling its hard, segmented shell into a ball. This arthropod grew up to six inches (15.24 cm) in length.
Phacops rana and other members of the order Phacopida are distinguished among trilobites by their schizochroal eyes, which were composed of many rounded lenses and could swivel almost completely around.
Trilobites lived throughout the Paleozoic age, first appearing early in the Cambrian period. Approximately 251 million years ago, a mass extinction event called the Permian–Triassic Extinction Event took place. This event occurred at the end of the Permian period of the Paleozoic era and the beginning of the Triassic period of the Mesozoic era, wiping out nearly 96 percent of all marine species and almost 70 percent of all terrestrial vertebrates living at the time. It is not known exactly what caused this event, but most theories include some form of catastrophe having a global impact.
Humans discovered trilobite fossils many centuries ago. Trilobite fossils have been found on necklaces in 15,000-year-old rock shelters in present-day Europe. The Ute Indians of the western United States used trilobites as amulets.
The largest complete trilobite ever found is an Isotelus rex specimen 28 inches (72 cm) long and 16 inches (40 cm) wide. This specimen was discovered in 1999 in Churchill, Manitoba, and is now displayed at the Manitoba Museum in Winnipeg.

Click to enlarge an image
State Prehistoric Creature
State Prehistoric Creature
Collection of Trilobites Embedded in Rock
State Prehistoric Creature
Phacops Rana

Species:P. rana
Author: World Trade Press

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