Paleozoic Era
Cambrian
545 million, extensive oceans cover North America (N. A.) warm seas.
An explosion of shallow marine organisms with greater varieties of body plans (invertebrates) than is now extant..
540 million, lampreys.
Marine arthropod called Anomalocaris (at left and below from Burgess shale fossils) is a seaside predator of some immense size and speculated ferocity. It fed in waters where salt water algae, sponges, brachiopods, cnidarians, mollusks, trilobites, crustaceans, starfish, and stromatolite reef building species spread in the warm tropical seas.
This predator was a large creature feeding on bottom dwelling denizens, or animals classified by where they live and are called called benthic fauna. Anomalocaris was a free swimming animal, unlike the corals and anemones.
A far greater diversity of body forms existed in this period, than now, since the evidence in the Burgess Shale (Cananda) formations is extensive:
530 m. y. a. : The BURGESS SHALE FORMATION:
"By recognizing so many unique anatomies in the Burgess, and by showing that familiar groups were then experimenting with designs so far beyond the modern range, they have inverted the" way we think about the diversity of life on earth. "The sweep of anatomical variety reached a maximum right after the initial diversification of multicellular animal. The later history of life proceeded by elimination, not expansion. The current earth may hold more species than ever before, but most are iterations on a few basic body plans."
"Compared with the Burgess seas, today's oceans contain many more species based upon many fewer anatomical plans."
"The maximum range of anatomical possibilities arises with the first rush of diversification. Later history is a tale of restriction, as most of the early experiments succumb and life settles down to generating endless variants upon a few surviving models. "
Stephen J. Gould, Wonderful Life, p. 47.
520 Avalonian continent finally broken up.
510 million, Closing of the ancient Iapetus Sea (the proto-atlantic Ocean)
extensive & massive extinctions of sea-life; worldwide ecological collapse.
********************************************1****************************************** Ordovician over half of North America covered by ocean water.
505 million, early shelled (calcium carbonate) organisms such as
Anomalocaris and fishes.
500 million, early mountain building (Orogeny) in Eastern N. A.
- Cephalopods like the chambered nautilus' ancestors called ammonites are varied and dominant. The earliest vertebrates are extensively preserved in limestone dominant rock (slate and marble sources). Huge deposits of once living creatures form oil and gas deposits associated with the rocks of the Cincinnati Arch; Tapeats Sandstone and Bright Angel formations of Grand Canyon.
Silurian first land arthropods and land plants. 438 million,
- early vascular plants, ancestral mosses and liverworts, northern APPALACHIANS formed from the collision of two continents: Laurentia and Baltica during the TACONIC OROGENY.
Devonian
408 million,
Coelacanths and other jawless fishes emerged, the earliest evergreen forests began to dominate the land. And in the seas there were sharks. The planet's land masses were divided into Gondwanaland in the south and Laurasia in the north divided by the shallow circum-equatorial water body called the proto-Thethys Sea.
- Life in the Devonian sea was quite diverse including giant eurypterids or 'sea scorpions' pursued early
jawed fishes, including acanthodians (sometimes called 'spiny sharks', though not related to true sharks) and shield-headed fishes called placoderms (which probably shared a common ancestor with the sharks). Rugose and halysite corals built great reefs, providing food and living spaces for many different kinds of creature. The sea floor supported a rich variety of crinoid 'sea lilies', stalked clam-like animals called brachiopods, bizarre colonial critters known as graptolites, and early versions of mollusks - such as chitons, tusk shells, and straight-shelled cephalopods related to modern-day nautiloids. The first plants - small, leafy pioneers known as rhinophytes - colonized the land, followed shortly thereafter by joint-limbed creatures such as scorpions, centipedes, and millipedes.
400 million,
- fishes dominate seas; early amphibians; vascular plants: club mosses, horsetails, Gymnosperms, seed ferns and other green plants.
375 million,
- Mangrove swamps, fish on mud flats, ACADIAN OROGENY formation of a Appalachian/ Pennine/ Scandinavian single Mt. chain stretching along the equator.
Global climatic changes lead eventually to a "great period of extinctions."