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Cambrian Marella Anomalocaris Hallucigenea Jellyfish? Shrimp? Sponge? Parts of Anomalocaris were at first thought to be three separate animals. Anomalocaris Wiwaxia corrugata Wiwaxia corrugata Marrella splendens Hallucigenia GLB in the Paleozoic Era Central North America experienced repeated transgressions and regressions of shallow, tropical seas during Paleozoic Midwest is below equator Large areas of tropical coral reefs Seas deposited layers of materials that became sedimentary rocks Limestone, shales, sandstone, gypsum Thornton Quarry, Sagawau Canyon limestone Ordovician Period 490 - 443 Million Years Ago Shallow, shifting seas covered most of North America Biodiversity increasing rapidly Corals, bryozoans, crinoids, cephalopods, a great variety of new brachiopods, trilobites First fish appear in fossil record Squid-like cephalopods were the largest creatures in Ordovician seas. Cone-shaped shells sometimes reached a length of 5 meters (about 16 ft.). Ordovician Period Sea floor covered by calcium carbonate mud produced by the breakdown of "stony" algae and animal remains. Bryozoans and algae trapped the sediment to form small mounds. Mounds protected animals, such as brachiopods, corals, crinoids, starfish, mollusks, and trilobites. Receptaculitids are common in the rocks from this area. Ordovician Fossils Ordovician Period Algae with Skeletons • Receptaculites appeared around 488 million years ago in the Lower Ordovician and disappeared 250 million years ago in the Lower Triassic. • Their modern-day cousins, the Dasycladaceae, are algae that also form calcareous skeletons. Brachiopods Rhynchotrema dentatum Illinois Onniella meeki Illinois Brachiopods 300 living species of brachiopods BrachiopodsLampshells Crinoid Pycnocrinus dyeri Cincinnati, Ohio Nautiloid Cephalopod Plectoderas undatus Illinois Corals rugose coral Grewingkia canadensis Cincinnati, Ohio tabulate coral Favistella alveolata Illinois Coral Reconstructions Rugose coral Tabulate Coral Tentaculites - mollusc Tentaculites incurvus Cape Girardeau, Missouri Tentaculites oswegoensis Waubonsee Creek in Oswego, IL Rock called Brainerd Formation Shale and thin dolomite Upper Ordovician and Silurian Tentaculites oswegoensis Fossils found only known in Illinois Animal ranged from Oswego, IL (Kendall County) to possibly Kankakee River State Park in Will County. Trilobite Isotelus iowensis Missouri Graptolites ‘Graptolite' means 'writing in rock‘ Hemichordate – related to echinoderms & chordates Most graptolites are thought to have been planktonic, floating or slowly sinking through the water. The spiral shape of some was probably an adaptation to slow sinking. Other graptolites may have been connected to gasfilled sacs, keeping them buoyant. Lived in water with low oxygen levels Fed on plankton Graptolites Hemichordates Phyllograptus archaios Spirograptus Graptolite Reconstructions Silurian Period 443 - 417 Million Years Ago — Silurian Period Shallow, tropical sea covered Illinois (then south of the equator) Reefs, corals, crinoids, and shelled invertebrates flourished Delicate corals, bryozoans, and crinoids were in protected pockets and along the sides of the reefs. Brachiopods, snails, clams, and trilobites were hidden in the tangle of the complex branches of these animals These shelled animals were eaten by predatory, squidlike cephalopods. Largest animals of the time were 2-meter-long (6.5 ft.) sea scorpions called eurypterids Eurypterids A group of eurypterids (sea scorpions) from Upper Silurian rocks of the Niagara Peninsula. Silurian Period Ocean reefs occurred in a band 30 degrees to the north and south of the equator. Most widespread distribution of reefs in the history of North America during Silurian Reefs ranged from less than a meter (3.3 ft.) to several kilometers in diameter and less than 3 meters (about 10 ft.) to nearly 304 meters (about 1000 ft.) high. Silurian Period Rich fossil deposits in Illinois and lower Midwest from this period Many fossils from ancient Silurian reefs e.g. Trilobites, Ammonites, Eurypterids, Corals, Crinoids, Brachiopods, Jawless Fish, Primitive Sharks Be sure to visit the online Silurian Reef exhibit from the Milwaukee Public Museum! Plants and wingless insects arose But GLB fossils of these are rare since entire region was under water Silurian Period Silurian rocks are exposed Along the Kennedy Expressway at Addison (southbound lanes) In the Thornton Quarry at Homewood In the Sag Bridge abandoned quarries (Cook County Forest Preserves) Along Rock Creek in the Kankakee River State Park Along the Illinois River Near the towns of Lemont, Romeoville and Joliet. Silurian Seat at Navy Pier Thornton Quarry: Then and Now Chicago is built upon a vast Silurian Reef. Silurian Reef Diorama at the Field Museum of Natural History in Chicago Fossil Crinoids, Brachiopods, Trilobites, Ammonoids, Gastropods and Corals are found in Thornton Quarry rock. Modern reef environments are found in warm, shallow oceans. The water is usually clear of silt and wind-blown sediments. Many of the reef inhabitants are filter feeders and sediment prevents feeding. Scene from a Silurian sea Silurian Fossils Bryozoan Fenestrellina elegans Chicago Crinoids Scyphocrinites sp Eucalyptocrimus crassus Indiana Diorama of a Silurian Reef Living Crinoids Cephalopods Nautaloid Cephalopod Michelinoceras Illinois Ammonoid Living Chambered Nautilus Silurian Trilobites Calymene celebra Milwaukee Slab of Upper Ordovician Tyndall Limestone at the quarry in Garson, north of Winnipeg showing a large Receptaculites (calcareous algae) and mottles produced by Thalassinoides burrows. Sponges Astylospongia praemosa Modern Sponges Sponge Fossils Corals tabulate coral Cladopora reticulata Louisville, Kentucky Tabulate Coral Living Corals Living Coral Polyps Trilobites Dicranurus monstrosus Note: defensive spines In the late Silurian, the first-known land plants (Cooksonia) and air-breathing animals (millipedes, centipedes and scorpions) appeared. Cooksonia Psilotum Arthropleura Myriopoda Pleurojulus steuri millipede Pleurojulus steuri