The Atoka Formation, formed in the Pennsylvanian Period, is a sequence of marine, mostly tan to gray silty sandstones and grayish-black shales.
12.
During the Pennsylvanian period, roughly 300 million years ago, the coastline of the Gulf of Mexico ran through the central parts of Arkansas.
13.
They are also found in marine bands of the Carboniferous coal measures in Europe and in marine rocks of the Pennsylvanian period in Arkansas.
14.
This material marks the uncertain transition between the Devonian and Pennsylvanian periods in the region and is also an important source of local fossils.
15.
The exposed portion of the mountain is made up entirely of limestone and dolomite from the Pennsylvanian period, and is about 300 million years old.
16.
Chepiwanoxet sits atop the western edge of the Rhode Island Formation of the stratified Narragansett Bay Group of the Pennsylvanian period ( between 323 and 290 million years ago ).
17.
Another, closely related species, lived in the Pennsylvanian period in North America . " Diplovertebron " is an important link in evolution, because its body structure resembled that of a reptile.
18.
Early in the succeeding Pennsylvanian Period, the area dropped to near sea level and for more than 50 million years continued to sink at about the same rate that deposition was taking place.
19.
The creature, believed to have been 3 to 4 feet-( 0.9 to 1.2 meters-) long, is " new to science but we know it belongs to fairly terrestrial-adapted amphibians living in the Pennsylvanian Period, about 300 million years ago, " said Christopher Beard, curator of vertebrate paleontology at the museum.
20.
The creature, believed to have been 3 to 4 feet-( 0 . 9 to 1 . 2 meters-) long, is " new to science but we know it belongs to fairly terrestrial-adapted amphibians living in the Pennsylvanian Period, about 300 million years ago, " said Christopher Beard, curator of vertebrate paleontology at the museum.
