1. Cambrian

5. Marella Anomalocaris Hallucigenea

6. Jellyfish? Shrimp? Sponge?

8. Parts of Anomalocaris were at first thought to be three separate animals.

12. Anomalocaris

13. Wiwaxia corrugata

14. Wiwaxia corrugata

15. Marrella splendens

16. Hallucigenia

17. 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

19. 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.).

20. 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.

22. Ordovician Fossils

23. Ordovician Period Algae with Skeletons • Receptaculitesappeared 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.

25. Brachiopods Rhynchotrema dentatum Illinois Onniella meeki Illinois

26. Brachiopods 300 living species of brachiopods

27. Brachiopods-Lampshells

30. Crinoid Pycnocrinus dyeri Cincinnati, Ohio

31. Nautiloid Cephalopod Plectoderas undatus Illinois

32. Corals rugose coral Grewingkia canadensis Cincinnati, Ohio tabulate coral Favistella alveolata Illinois

33. Coral Reconstructions Rugose coral Tabulate Coral

34. Tentaculites - mollusc Tentaculites incurvus Cape Girardeau, Missouri

35. 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.

38. Trilobite Isotelus iowensis Missouri

40. 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 gas-filled sacs, keeping them buoyant. • Lived in water with low oxygen levels • Fed on plankton

41. Graptolites Hemichordates

42. Phyllograptus archaios

43. Spirograptus

44. Graptolite Reconstructions

45. 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, squid-like cephalopods. • Largest animals of the time were 2-meter-long (6.5 ft.) sea scorpions called eurypterids

46. Eurypterids

48. A group of eurypterids (sea scorpions) from Upper Silurian rocks of the Niagara Peninsula.

49. 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.

50. 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