Nevada’s Devonian Sea
During the entire Devonian Period (ca. 420 – 360 million years ago) much of modern-day western North America lay beneath a warm, saltwater sea. In a condensed space, this diorama shows back-reef (shoreward waters), reef, and fore-reef (deeper waters) that existed 365 Mya over what would become Nevada. For the most part, these habitats were composed of different kinds of organisms than their modern-day counterparts.
Crinoids
These creatures looked somewhat like current-day starfish on stalks. During the Paleozoic Era (ca. 540 – 252 Mya) these echinoderms were very abundant in shallow water environments where they lived attached to the bottom. Some of the specimens seen here have pink and white stripped snails (genus Platyceras) nestled within their arms. These snails, which are now extinct, are thought to have fed on the crinoid’s waste.
The stalks of these animals were formed of stacked disks. Their fossilized and separated remains look like cheerios and are common in limestone of the Great Basin. The modern counterparts of these animals, sea lilies, live mostly in very deep water.
Nautiloid
The straight shelled nautiloid was a kind of Cephalopoda (represented today by octopus, cuttlefish & nautilus). Other Devonian nautiloids had shells that were loosely curved or tightly coiled. Once extremely abundant, these animals have all but died off today.
Brachiopods
While looking like clams, they are actually quite different. These marine animals reached their highest numbers and diversity in the Devonian. At the end of the Paleozoic, around 252 Mya, most types were extinct. Today most brachiopods live in the cold waters of polar regions or at great depths.
Trilobites
These hard-shelled, segmented creatures with jointed legs look like modern-day “sowbugs”. Like these latter animals, they could probably escape predators by rolling into a ball, but they could probably also bury themselves in the sand. Trilobites were the most primitive arthropods (group of animals with a hard outer shells/exoskeletons and jointed appendages). They flourished on earth’s early sea floors, but most groups disappeared by the end of the Devonian.
Fish
The Devonian Period is called the “Age of Fishes” because of the vast diversity of fish living during this time. Bottom dwelling, armored fish called placoderms, such as the pink, squat-bodied Asterolepis, inhabited what was a shallow tropical sea in central Nevada. The ray-finned fish (related to modern ones such as the trout), like the orange colored, pointy-nosed Cheirolepis, also arose during the Devonian. Another important group to develop then was lobed-finned fish (represented today by the living fossil coelacanth). Compared to the ray-finned fish, lobed-fin fish have more robust, fleshy fins. A group of lobed-finned fish called the rhipidisteans (like the large Eusthenopteron to your right) gave rise to the first amphibians during the Devonian.