An armoured jawless fish (a Cephalaspis, which is a kind of osteostracan). This creature evolved as it adapted to the transition from open sea to freshwater conditions in the Ludlow area towards the end of the Silurian.
A fossil butterfly from nymphalid, today the largest family of butterflies (and perhaps then, too). Its fossilized remains were entombed in paper shale that has risen to the surface at what is now the Florissant Fossil Beds National Monument in Colorado.
Rock Layers: Timeline of Life on EarthEvolution is a complicated subject. While everybody understands that black bears are related to grizzly bears and we can even figure they are related to extinct bears, lots of people wonder how scientists can be so su
Bones & fossilized heart of a old dinosaur skeleton, at the NC Mus of Nat. Sciences in Raleigh, NC. The fossilized heart - w/two ventricles & a single aortic stem, between an apex of shoulder bones, is the first one ever found in a dinosaur
Helicoprion is a long-lived genus of extinct, eugeneodontid holocephalid fish. Almost all fossil specimens are of spirally arranged clusters of the individuals' teeth, called "tooth whorls." This fossilized jaw shows the spiral dentures.