Phacops rana
Encyclopedia
Phacops rana is a species of trilobite
from the middle Devonian
period. Their fossil
s are found chiefly in the northeastern United States
, southwestern Ontario
, and in Morocco
.
on the outside as protection. Many other trilobites possessed the same ability, but Phacops rana nearly perfected it. The slightest amount of sediment
would trigger their senses, and Phacops rana would be hidden in a tiny shelter made of its own body. Although this safety feature often helped them to evade predators, occasionally it backfired and the trilobite would be buried under heavy sediment. Their fossil
s can still be found in balled-up positions 400 million years later.
during the Devonian.
Because of its abundance and popularity with collectors, Phacops rana was designated the Pennsylvania
state fossil
by the state's General Assembly on December 5, 1988.
of Phacops rana and its relatives is their eyes. These differed from the eyes of most trilobites in having comparatively few lenses spaced between deep sclera
. The lenses themselves were very rounded instead of largely flat. The eyes were mounted on turret-like structures which could swivel, providing the animal with an almost 360 degree field of view. This type of eye is known as the Schizochroal eye.
Trilobite
Trilobites are a well-known fossil group of extinct marine arthropods that form the class Trilobita. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period , and they flourished throughout the lower Paleozoic era before...
from the middle Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
period. Their fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s are found chiefly in the northeastern United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, southwestern Ontario
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
, and in Morocco
Morocco
Morocco , officially the Kingdom of Morocco , is a country located in North Africa. It has a population of more than 32 million and an area of 710,850 km², and also primarily administers the disputed region of the Western Sahara...
.
Physiology
Phacops rana and its related genus can be recognized by its large eyes (which remind some observers of a frog's eyes — the specific name rana is a reference to a common frog), its fairly large size (up to 6 inches long), and its habit of rolling up into a ball like a pill bug. In order to protect themselves from predators, Phacops rana would roll into a ball with its hard exoskeletonExoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
on the outside as protection. Many other trilobites possessed the same ability, but Phacops rana nearly perfected it. The slightest amount of sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
would trigger their senses, and Phacops rana would be hidden in a tiny shelter made of its own body. Although this safety feature often helped them to evade predators, occasionally it backfired and the trilobite would be buried under heavy sediment. Their fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s can still be found in balled-up positions 400 million years later.
Fossilisation
Phacops rana is found both in the northeastern U.S. and in Morocco; North America was attached to the African plateAfrican Plate
The African Plate is a tectonic plate which includes the continent of Africa, as well as oceanic crust which lies between the continent and various surrounding ocean ridges.-Boundaries:...
during the Devonian.
Because of its abundance and popularity with collectors, Phacops rana was designated the Pennsylvania
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...
state fossil
State fossil
Most American states have made a state fossil designation, in many cases during the 1980s. It is common to designate one species in which fossilization has occurred, rather than a single specimen, or a category of fossils not limited to a single species....
by the state's General Assembly on December 5, 1988.
Phacopid eyes
The most striking feature of the morphologyMorphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
of Phacops rana and its relatives is their eyes. These differed from the eyes of most trilobites in having comparatively few lenses spaced between deep sclera
Sclera
The sclera , also known as the white or white of the eye, is the opaque , fibrous, protective, outer layer of the eye containing collagen and elastic fiber. In the development of the embryo, the sclera is derived from the neural crest...
. The lenses themselves were very rounded instead of largely flat. The eyes were mounted on turret-like structures which could swivel, providing the animal with an almost 360 degree field of view. This type of eye is known as the Schizochroal eye.