Paleontology in Illinois

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The location of the state of Illinois Map of USA IL.svg
The location of the state of Illinois

Paleontology in Illinois refers to paleontological research occurring within or conducted by people from the U.S. state of Illinois. Scientists have found that Illinois was covered by a sea during the Paleozoic Era. Over time this sea was inhabited by animals including brachiopods, clams, corals, crinoids, sea snails, sponges, and trilobites.

Contents

Fossils are common from the Ordovician through the Pennsylvanian. Illinois has a reputation for rocks bearing large numbers of trilobite fossils, often of very high preservational quality. [1] There is a gap in Illinois' geologic record from the Mesozoic to the Pleistocene. During the Ice Age, Illinois was subject to glacial activity. At the time the state was home to creatures like giant beavers, mammoths, mastodons, and stag mooses.

Paleontology has a long history in the State of Illinois, stretching at least as far back as the 1850s, when the first Mazon Creek fossils were being found. Early in the ensuing 20th century a Silurian age fossil reef system was discovered in the state. In the 1950s Francis Tully discovered the "monster" that would later be named in his honor. The Pennsylvanian species Tullimonstrum gregarium ("Tully Monster") is the Illinois state fossil. It is one of the few officially designated state fossils that is endemic to the state it represents.

Prehistory

Isotelus. Isotelus brachycephalus.JPG
Isotelus .

No Precambrian fossils are known from Illinois. As such, the state's fossil record does not begin until the Paleozoic. [2] Illinois was covered by a sea during the Paleozoic. Over time this sea would be inhabited by animals like brachiopods, clams, corals, crinoids, snails, sponges, trilobites. [3] 500 million years ago, during the Cambrian, the seas of Illinois resembled those of the modern Bahamas. [4] At the time, Illinois was located near the equator. [5] Illinois was home to trilobites. [3] Cambrian trilobites left their remains in the state's north-central region. [1] In other areas of Illinois Cambrian trilobite fossils have only been found in core samples drilled from deeply buried rocks. [1]

Ordovician

During the Ordovician, Illinois was still located near the equator and still covered by a shallow tropical sea. [5] Graptolites reached their peak abundance in the state's history during this time. [6] They left remains behind in the northern part of the state. [6] Cephalopods were diverse during the Ordovician with some having straight shells and others being coiled. [7] They left behind remains in northern and western Illinois. [7]

Gastropods were common. [7] "Sunflower coral" sponges were also common in north-central Illinois. [7] Trilobites were still present and Ordovician rocks are a better source of trilobite fossils than the state's Cambrian deposits. However, this is due to the Ordovician rocks being more accessible to collectors than the older ones. [1] Ordovician trilobites from Illinois included Isotelus and Ceraurus . [8] Ordovician trilobites left behind remains in northern and southwestern Illinois. [1]

Marine worms flourished in the bottom sediment of the sea that covered Illinois. Their presence is attested to be fossils of their jaws. After the Ordovician trilobite abundance and diversity declined significantly. [3]

Silurian

Tropical marine conditions continued to persist into the Silurian. [5] Trilobites were still present and like the Ordovician Silurian rocks are a better source of trilobite fossils than the state's Cambrian deposits. Also like the Ordovician, the superiority of Silurian rocks as a source of trilobites is due to the Silurian rocks being more accessible to collectors than the older ones. [1] Silurian trilobites from Illinois include Dalmanites and Calymene . [8] Silurian trilobites left behind remains in northern and southwestern Illinois. [1]

Hindia sponges lived in the Silurian near Chicago. [7] Another Silurian resident of the Chicago region were cystoids. Most of the state's cystoid fossils are preserved in deposits that formed in that place and time [7] Jaws left by marine worms are even more common from the Silurian of northeastern Illinois than they were back in the Ordovician. [7] Illinoisan trilobites diversity and abundance suffered further losses after the end of the Silurian Period. [1]

Devonian

During the Devonian Illinois was still covered by the sea and had not drifted far north from the equator. [5] Trilobites were still present. Devonian trilobites from Illinois included Phacops and Odontocephalus . [8]

Mississippian

Illinois was still under seawater during the early Carboniferous. Bryozoans were very common all throughout Illinois during the Mississippian epoch. [7] Brachiopods were also very common in the Mississippian of the Mississippi and Ohio River areas. [7] Mississippian trilobites from Illinois included Brachmetopus . [8]

Pennsylvanian

Amphibamus Amphibamus BW.jpg
Amphibamus
Sphenophyllum Sphenophyllum miravallis.jpg
Sphenophyllum

Illinois was still located near the equator during the Pennsylvanian. Western and central Illinois was covered in swamps bordering the remnants of the shallow sea that once covered the state. [9] Fusulinids are common in Pennsylvanian rocks. [7] Shelled cephalopods were diverse during the Pennsylvanian with some having straight shells and others being coiled. [7] Other inhabitants included the Tully monster, as well as animals recognizably related to modern life like shrimp, jelly fish, sharks and squid. [9] Coelacanths were among the state's Pennsylvanian aquatic vertebrates. [10] Gastropods were common. [7] Clams were common in central Illinois during the Pennsylvanian. [7] Illinoisan horseshoe crab fossils are only known from the Pennsylvanian of the Mazon Creek area. [6] Trilobites were still present in Illinois and included Ameura and Ditomopyge . [8]

325 million years ago Illinois was covered in heavily forested deltaic swamps. [11] The trees composing this Pennsylvanian forest included Cordaites , scale trees, and seal trees. [12] Some of these trees could grow over 100 feet high. [11] The rest of the flora included scouring rushes, Sphenophyllum , ferns, and seed ferns. The fossils they left behind include casts, molds, compressions, and even entire plant preserved in nodules. [12] Rivers running through the ancient swamps swept leaves and plant debris out to sea. [9] The environment of Pennsylvanian Illinois was comparable to the modern Amazon River delta. [9] Almost every Pennsylvanian deposit in Illinois preserves evidence of this ancient flora and such deposits are located in almost every region of the state. [12] The vegetation of these ancient swamps became Illinois' modern coal deposits. [9] [11]

More than 130 kinds of insects inhabited the Pennsylvanian Mazon Creek area. [10] The insects are typical for what one would expect to see in a woodland near the sea. [6] Some of these insects were similar to modern forms like dragonflies, roaches, and damselflies. Others are unlike anything alive today. Other terrestrial invertebrate life included early scorpions and a variety of primitive spiders. Mazon Creek vertebrates included the small amphibian Amphibamus grandiceps , which may be a relative of the amphibian lineage that led up to frogs. [10] Amphibians as large as ten feet in length lived in these swamps. [11] Some early vertebrates preserved in the Mazon Creek's concretionary nodules have fossilized soft tissue. [10]

A gap in the local rock record spans the entire Permian period, so there are no rocks of this age in Illinois in which fossils could have been preserved. [2] However, one notable local event following the Pennsylvanian was the meteor impact that occurred near modern Des Plaines. [13] Another is the extinction of the trilobites at the end of the Permian. [3]

Mesozoic

Most of the Mesozoic era is also missing from the local rock record. This is because during that time sediments were generally being eroded away from Illinois rather than deposited. Nevertheless, a few Cretaceous deposits are known in the state. During the Cretaceous Illinois was home to foraminiferans. Contemporary local plants also left behind leaves that would later fossilize. [2] [14] [15] [16]

Cenozoic

Likewise, there are few rocks dating back to the ensuing Tertiary period of the Cenozoic era. Some wildlife from that time period were preserved in the far southern region of the state, but otherwise little is known about Tertiary Illinois. [2] The fossil record does not become productive again until the Pleistocene. [10] The area where modern Peoria is situated was home to the Mississippi river two million years ago. At the same time, the area where the modern University of Illinois Urbana-Champaign stands was home to the Mahomet River. At that time the Mississippi River flowed through Bureau and Henry counties. The Mahomet River joined it near Havana. [17]

Illinois experienced its main periods of glaciation over the past 1.8 million years. These glaciers filled in the Mahomet River valley. [18] The melting glaciers transported large amounts of sediment that filled in the original course of the Mississippi River, which took on its modern course. Other glacial melt water went on to form large lakes. [19]

The advance and retreat of Illinois' glaciers coincided with cooling and warming spells of climate. During the warm spells Illinois was home to animals like jaguars, peccaries, and armadillos. During cold spells Illinois was home to animals like mammoths, mastodons, stag mooses, and giant beavers. Snowshoe hares also used to make their home in Illinois. [20] The Illinoian (stage) glaciation occurred some 300,000 to 130,000 years ago. The last time glaciers covered Illinois was during the Wisconsin glaciation 25,000 years ago. [18]

History

Restoration of the Tully monster. Tullimonstrum NT small.jpg
Restoration of the Tully monster.

As far back as the late 1850s significant fossil discoveries were occurring in Illinois. At this time fossils were discovered in nodules discovered at natural rock exposures along the Mazon Creek in Grundy County. Early in the 20th century, J. H. Bretz and H. A. Lowenstam studied the Silurian fossil reef systems of the Chicago area following a decline in scientific attention paid to the famous fossil reefs of similar age near Milwaukee, Wisconsin. [21] Later, during the 1920s, strip mining for coal south of Braidwood generated piles of waste rock that would later become popular sites for fossil collection. These waste piles would later serve as the source for most Tully monster finds. [22] During the late 1950s Francis Tully found a fossil he could not identify at the strip mines near Braidwood. He took the specimen to Chicago's Field Museum of Natural History. Researchers at the museum could not identify it either, and the specimen became known as Mr. Tully's monster. In 1966, Eugene Richardson, the Curator of Fossil Invertebrates of the Field Museum formally named the Tully monster Tullimonstrum gregarium . [23] Finally, in 2016, scientists after reviewing over 1,000 fossilized Tully Monsters placed it in the same phylum as, and possibly related to, lampreys. [24] The Tully monster is one of the few officially designated state fossils to be endemic to its state of origins. [23]

People

Births

Deaths

Natural history museums

Notable clubs and associations

See also

Footnotes

  1. 1 2 3 4 Theodor, Scotchmoor, and Springer (2005); "Paleontology and geology".
  2. 1 2 3 4 Kolata (2004); "The Trilobite—An Early Inhabitant of Illinois", page 1.
  3. Vaiden (2004); "Ancient Oceans of Illinois", page 1.
  4. 1 2 3 4 Vaiden (2004); "Ancient Oceans of Illinois", page 2.
  5. 1 2 3 4 Murray (1974); "Illinois", page 135.
  6. 1 2 3 4 5 6 7 8 9 10 11 12 13 Murray (1974); "Illinois", page 134.
  7. 1 2 3 4 5 Kolata (2004); "Timeline", page 2.
  8. 1 2 3 4 5 Mikulic and Kluessendorf (2004); "The Ancient Landscape", page 1.
  9. 1 2 3 4 5 Murray (1974); "Illinois", page 132.
  10. 1 2 3 4 Vaiden (2004); "Delta Swamp", page 3.
  11. 1 2 3 Murray (1974); "Illinois", page 133.
  12. Vaiden (2004); "Delta Swamp", page 4.
  13. Vaiden (2004); "When Dinosaurs Ruled!", page 5.
  14. Dinosaur FAQ.
  15. Animals Past and Present.
  16. Vaiden (2004); "Lost Rivers of Illinois", page 6.
  17. 1 2 Vaiden (2004); "Ice Ages", page 8.
  18. Vaiden (2004); "Ice Ages", page 9.
  19. Vaiden (2004); "Ice Ages: Did You Know", page 8.
  20. Mikulic (2001); "Abstract", page 7.
  21. Mikulic and Kluessendorf (2004); "How the Tully Monster was Preserved", page 2.
  22. 1 2 Mikulic and Kluessendorf (2004); "Mr. Tully Finds a Fossil", page 2.
  23. "Does the mysterious 'Tully Monster' finally have a family? - The Washington Post".
  24. Garcia and Miller (1998); "Appendix C: Major Fossil Clubs", page 198.
  25. Garcia and Miller (1998); "Appendix B: Major Fossil Shows", page 195.

Related Research Articles

The Mazon Creek fossil beds are a conservation lagerstätte found near Morris, in Grundy County, Illinois. The fossils are preserved in ironstone concretions, formed approximately 309 million years ago in the mid-Pennsylvanian epoch of the Carboniferous period. These concretions frequently preserve both hard and soft tissues of animal and plant materials, as well as many soft-bodied organisms that do not normally fossilize. The quality, quantity and diversity of fossils in the area, known since the mid-nineteenth century, make the Mazon Creek lagerstätte important to paleontologists attempting to reconstruct the paleoecology of the sites. The locality was declared a National Historic Landmark in 1997.

The geology of Illinois includes extensive deposits of marine sedimentary rocks from the Palaeozoic, as well as relatively minor contributions from the Mesozoic and Cenozoic. Ice age glaciation left a wealth of glacial topographic features throughout the state.

<i>Calymene blumenbachii</i> Extinct species of trilobite

Calymene blumenbachii Brongniart in Desmarest (1817), sometimes erroneously spelled blumenbachi, is a species of trilobite discovered in the limestone quarries of the Wren's Nest in Dudley, England. Nicknamed the Dudley Bug or Dudley Locust by 18th-century quarrymen it became a symbol of the town and featured on the Dudley County Borough Council coat-of-arms. Calymene blumenbachii is commonly found in Silurian rocks and is thought to have lived in the shallow waters of the Silurian, in low-energy reefs. This particular species of Calymene is unique to the Wenlock series in England, and comes from the Wenlock Limestone Formation in Much Wenlock and the Wren's Nest in Dudley. These sites seem to yield trilobites more readily than any other areas on the Wenlock Edge, and the rock here is dark grey as opposed to yellowish or whitish as it appears on other parts of the Edge, just a few miles away, in Church Stretton and elsewhere. This suggests local changes in the environment in which the rock was deposited.

<span class="mw-page-title-main">Paleontology in Michigan</span>

Paleontology in Michigan refers to paleontological research occurring within or conducted by people from the U.S. state of Michigan. During the Precambrian, the Upper Peninsula was home to filamentous algae. The remains it left behind are among the oldest known fossils in the world. During the early part of the Paleozoic Michigan was covered by a shallow tropical sea which was home to a rich invertebrate fauna including brachiopods, corals, crinoids, and trilobites. Primitive armored fishes and sharks were also present. Swamps covered the state during the Carboniferous. There are little to no sedimentary deposits in the state for an interval spanning from the Permian to the end of the Neogene. Deposition resumed as glaciers transformed the state's landscape during the Pleistocene. Michigan was home to large mammals like mammoths and mastodons at that time. The Holocene American mastodon, Mammut americanum, is the Michigan state fossil. The Petoskey stone, which is made of fossil coral, is the state stone of Michigan.

<span class="mw-page-title-main">Paleontology in West Virginia</span>

Paleontology in West Virginia refers to paleontological research occurring within or conducted by people from the U.S. state of West Virginia. West Virginia's fossil record begins in the Cambrian. From that time through the rest of the early Paleozoic, the state was at least partially submerged under a shallow sea. The Paleozoic seas of West Virginia were home to creatures like corals, eurypterids, graptolites, nautiloids, and trilobites at varying times. During the Carboniferous period, the sea was replaced by lushly vegetated coastal swamps. West Virginia is an excellent source of fossil plants due to these deposits. These swamps were home to amphibians. A gap in the local rock record spans from the Permian to the end of the Cenozoic. West Virginia was never the site of glacial activity during the Ice Age, but the state was home to creatures like mammoths, mastodons, and giant ground sloths. One local ground sloth, Megalonyx jeffersonii, was subject to the scholarly investigations of Thomas Jefferson, who misinterpreted the large-clawed remains as belonging to a lion-like predator. In 2008, this species was designated the West Virginia state fossil.

<span class="mw-page-title-main">Paleontology in Ohio</span>

Paleontology in Ohio refers to paleontological research occurring within or conducted by people from the U.S. state of Ohio. Ohio is well known for having a great quantity and diversity of fossils preserved in its rocks. The state's fossil record begins early in the Paleozoic era, during the Cambrian period. Ohio was generally covered by seawater from that time on through the rest of the early Paleozoic. Local invertebrates included brachiopods, cephalopods, coral, graptolites, and trilobites. Vertebrates included bony fishes and sharks. The first land plants in the state grew during the Devonian. During the Carboniferous, Ohio became a more terrestrial environment with an increased diversity of plants that formed expansive swampy deltas. Amphibians and reptiles began to inhabit the state at this time, and remained present into the ensuing Permian. A gap in the local rock record spans from this point until the start of the Pleistocene. During the Ice Age, Ohio was home to giant beavers, humans, mammoths, and mastodons. Paleo-Indians collected fossils that were later incorporated into their mounds. Ohio has been the birthplace of many world famous paleontologists, like Charles Schuchert. Many significant fossils curated by museums in Europe and the United States were found in Ohio. Major local fossil discoveries include the 1965 discovery of more than 50,000 Devonian fish fossils in Cuyahoga County. The Ordovician trilobite Isotelus maximus is the Ohio state invertebrate fossil.

<span class="mw-page-title-main">Paleontology in Kentucky</span>

Paleontology in Kentucky refers to paleontological research occurring within or conducted by people from the U.S. state of Kentucky.

<span class="mw-page-title-main">Paleontology in Indiana</span>

Paleontology in Indiana refers to paleontological research occurring within or conducted by people from the U.S. state of Indiana. Indiana's fossil record stretches all the way back to the Precambrian, when the state was inhabited by microbes. More complex organisms came to inhabit the state during the early Paleozoic era. At that time the state was covered by a warm shallow sea that would come to be inhabited by creatures like brachiopods, bryozoans, cephalopods, crinoids, and trilobites. During the Silurian period the state was home to significant reef systems. Indiana became a more terrestrial environment during the Carboniferous, as an expansive river system formed richly vegetated deltas where amphibians lived. There is a gap in the local rock record from the Permian through the Mesozoic. Likewise, little is known about the early to middle Cenozoic era. During the Ice Age however, the state was subject to glacial activity, and home to creatures like short-faced bears, camels, mammoths, and mastodons. After humans came to inhabit the state, Native Americans interpreted the fossil proboscidean remains preserved near Devil's Lake as the bones of water monsters. After the advent of formal scientific investigation one paleontological survey determined that the state was home to nearly 150 different kinds of prehistoric plants.

<span class="mw-page-title-main">Paleontology in Virginia</span>

Paleontology in Virginia refers to paleontological research occurring within or conducted by people from the U.S. state of Virginia. The geologic column in Virginia spans from the Cambrian to the Quaternary. During the early part of the Paleozoic, Virginia was covered by a warm shallow sea. This sea would come to be inhabited by creatures like brachiopods, bryozoans, corals, and nautiloids. The state was briefly out of the sea during the Ordovician, but by the Silurian it was once again submerged. During this second period of inundation the state was home to brachiopods, trilobites and entire reef systems. During the mid-to-late Carboniferous the state gradually became a swampy environment.

<span class="mw-page-title-main">Paleontology in Tennessee</span>

Paleontology in Tennessee refers to paleontological research occurring within or conducted by people from the U.S. state of Tennessee. During the early part of the Paleozoic era, Tennessee was covered by a warm, shallow sea. This sea was home to brachiopods, bryozoans, cephalopods, corals, and trilobites. Tennessee is one of the best sources of Early Devonian fossils in North America. During the mid-to-late Carboniferous, the state became a swampy environment, home to a rich variety of plants including ferns and scale trees. A gap in the local rock record spans from the Permian through the Jurassic. During the Cretaceous, the western part of the state was submerged by seawater. The local waters were home to more fossil gastropods than are known from anywhere else in the world. Mosasaurs and sea turtles also inhabited these waters. On land the state was home to dinosaurs. Western Tennessee was still under the sea during the early part of the Cenozoic. Terrestrial portions of the state were swampy. Climate cooled until the Ice Age, when the state was home to Camelops, horses, mammoths, mastodons, and giant ground sloths. The local Yuchi people told myths of giant lizard monsters that may have been inspired by fossils either local or encountered elsewhere. In 1920, after local fossils became a subject of formal scientific study, a significant discovery of a variety of Pleistocene creatures was made near Nashville. The Cretaceous bivalve Pterotrigonia thoracica is the Tennessee state fossil.

<span class="mw-page-title-main">Paleontology in Pennsylvania</span>

Paleontology in Pennsylvania refers to paleontological research occurring within or conducted by people from the U.S. state of Pennsylvania. The geologic column of Pennsylvania spans from the Precambrian to Quaternary. During the early part of the Paleozoic, Pennsylvania was submerged by a warm, shallow sea. This sea would come to be inhabited by creatures like brachiopods, bryozoans, crinoids, graptolites, and trilobites. The armored fish Palaeaspis appeared during the Silurian. By the Devonian the state was home to other kinds of fishes. On land, some of the world's oldest tetrapods left behind footprints that would later fossilize. Some of Pennsylvania's most important fossil finds were made in the state's Devonian rocks. Carboniferous Pennsylvania was a swampy environment covered by a wide variety of plants. The latter half of the period was called the Pennsylvanian in honor of the state's rich contemporary rock record. By the end of the Paleozoic the state was no longer so swampy. During the Mesozoic the state was home to dinosaurs and other kinds of reptiles, who left behind fossil footprints. Little is known about the early to mid Cenozoic of Pennsylvania, but during the Ice Age it seemed to have a tundra-like environment. Local Delaware people used to smoke mixtures of fossil bones and tobacco for good luck and to have wishes granted. By the late 1800s Pennsylvania was the site of formal scientific investigation of fossils. Around this time Hadrosaurus foulkii of neighboring New Jersey became the first mounted dinosaur skeleton exhibit at the Academy of Natural Sciences in Philadelphia. The Devonian trilobite Phacops rana is the Pennsylvania state fossil.

<span class="mw-page-title-main">Paleontology in Wisconsin</span>

Paleontology in Wisconsin refers to paleontological research occurring within or conducted by people from the U.S. state of Wisconsin. The state has fossils from the Precambrian, much of the Paleozoic, some a parts of the Mesozoic and the later part of the Cenozoic. Most of the Paleozoic rocks are marine in origin. Because of the thick blanket of Pleistocene glacial sediment that covers the rock strata in most of the state, Wisconsin’s fossil record is relatively sparse. In spite of this, certain Wisconsin paleontological occurrences provide exceptional insights concerning the history and diversity of life on Earth.

<span class="mw-page-title-main">Paleontology in Missouri</span>

Paleontology in Missouri refers to paleontological research occurring within or conducted by people from the U.S. state of Missouri. The geologic column of Missouri spans all of geologic history from the Precambrian to present with the exception of the Permian, Triassic, and Jurassic. Brachiopods are probably the most common fossils in Missouri.

<span class="mw-page-title-main">Paleontology in Minnesota</span>

Paleontology in Minnesota refers to paleontological research occurring within or conducted by people from the U.S. state of Minnesota. The geologic record of Minnesota spans from Precambrian to recent with the exceptions of major gaps including the Silurian period, the interval from the Middle to Upper Devonian to the Cretaceous, and the Cenozoic. During the Precambrian, Minnesota was covered by an ocean where local bacteria ended up forming banded iron formations and stromatolites. During the early part of the Paleozoic era southern Minnesota was covered by a shallow tropical sea that would come to be home to creatures like brachiopods, bryozoans, massive cephalopods, corals, crinoids, graptolites, and trilobites. The sea withdrew from the state during the Silurian, but returned during the Devonian. However, the rest of the Paleozoic is missing from the local rock record. The Triassic is also missing from the local rock record and Jurassic deposits, while present, lack fossils. Another sea entered the state during the Cretaceous period, this one inhabited by creatures like ammonites and sawfish. Duckbilled dinosaurs roamed the land. The Paleogene and Neogene periods of the ensuing Cenozoic era are also missing from the local rock record, but during the Ice Age evidence points to glacial activity in the state. Woolly mammoths, mastodons, and musk oxen inhabited Minnesota at the time. Local Native Americans interpreted such remains as the bones of the water monster Unktehi. They also told myths about thunder birds that may have been based on Ice Age bird fossils. By the early 19th century, the state's fossil had already attracted the attention of formally trained scientists. Early research included the Cretaceous plant discoveries made by Leo Lesquereux.

<span class="mw-page-title-main">Paleontology in Texas</span>

Paleontology in Texas refers to paleontological research occurring within or conducted by people from the U.S. state of Texas. Author Marian Murray has said that "Texas is as big for fossils as it is for everything else." Some of the most important fossil finds in United States history have come from Texas. Fossils can be found throughout most of the state. The fossil record of Texas spans almost the entire geologic column from Precambrian to Pleistocene. Shark teeth are probably the state's most common fossil. During the early Paleozoic era Texas was covered by a sea that would later be home to creatures like brachiopods, cephalopods, graptolites, and trilobites. Little is known about the state's Devonian and early Carboniferous life. Evidence indicates that during the late Carboniferous the state was home to marine life, land plants and early reptiles. During the Permian, the seas largely shrank away, but nevertheless coral reefs formed in the state. The rest of Texas was a coastal plain inhabited by early relatives of mammals like Dimetrodon and Edaphosaurus. During the Triassic, a great river system formed in the state that was inhabited by crocodile-like phytosaurs. Little is known about Jurassic Texas, but there are fossil aquatic invertebrates of this age like ammonites in the state. During the Early Cretaceous local large sauropods and theropods left a great abundance of footprints. Later in the Cretaceous, the state was covered by the Western Interior Seaway and home to creatures like mosasaurs, plesiosaurs, and few icthyosaurs. Early Cenozoic Texas still contained areas covered in seawater where invertebrates and sharks lived. On land the state would come to be home to creatures like glyptodonts, mammoths, mastodons, saber-toothed cats, giant ground sloths, titanotheres, uintatheres, and dire wolves. Archaeological evidence suggests that local Native Americans knew about local fossils. Formally trained scientists were already investigating the state's fossils by the late 1800s. In 1938, a major dinosaur footprint find occurred near Glen Rose. Pleurocoelus was the Texas state dinosaur from 1997 to 2009, when it was replaced by Paluxysaurus jonesi after the Texan fossils once referred to the former species were reclassified to a new genus.

The geological history of North America comprises the history of geological occurrences and emergence of life in North America during the interval of time spanning from the formation of the Earth through to the emergence of humanity and the start of prehistory. At the start of the Paleozoic Era, what is now "North" America was actually in the Southern Hemisphere. Marine life flourished in the country's many seas, although terrestrial life had not yet evolved. During the latter part of the Paleozoic, seas were largely replaced by swamps home to amphibians and early reptiles. When the continents had assembled into Pangaea, drier conditions prevailed. The evolutionary precursors to mammals dominated the country until a mass extinction event ended their reign.

The geology of Ohio formed beginning more than one billion years ago in the Proterozoic eon of the Precambrian. The igneous and metamorphic crystalline basement rock is poorly understood except through deep boreholes and does not outcrop at the surface. The basement rock is divided between the Grenville Province and Superior Province. When the Grenville Province crust collided with Proto-North America, it launched the Grenville orogeny, a major mountain building event. The Grenville mountains eroded, filling in rift basins and Ohio was flooded and periodically exposed as dry land throughout the Paleozoic. In addition to marine carbonates such as limestone and dolomite, large deposits of shale and sandstone formed as subsequent mountain building events such as the Taconic orogeny and Acadian orogeny led to additional sediment deposition. Ohio transitioned to dryland conditions in the Pennsylvanian, forming large coal swamps and the region has been dryland ever since. Until the Pleistocene glaciations erased these features, the landscape was cut with deep stream valleys, which scoured away hundreds of meters of rock leaving little trace of geologic history in the Mesozoic and Cenozoic.

<span class="mw-page-title-main">Waukesha Biota</span> Lagerstätte Fossil site in Waukesha County, Wisconsin, U.S.

The Waukesha Biota is an important fossil site located in Waukesha County and Franklin, Milwaukee County within the state of Wisconsin. This biota is preserved in certain strata within the Brandon Bridge Formation, which dates to the early Silurian period. It is known for the exceptional preservation of soft-bodied organisms, including many species found nowhere else in rocks of similar age. The site's discovery was announced in 1985, leading to a plethora of discoveries. This biota is one of the few well studied Lagerstätten from the Silurian, making it important in our understanding of the period's biodiversity. Some of the species are not easily classified into known animal groups, showing that much research remains to be done on this site. Other taxa that are normally common in Silurian deposits are rare here, but trilobites are quite common.

<i>Venustulus</i> Extinct genus of chelicerate from Wisconsin

Venustulus is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Venustulus was regarded as part of the clade Prosomapoda. Fossils of the single and type species, V. waukeshaensis, have been discovered in deposits of the Silurian period in Wisconsin, in the United States. Venustulus is one of the few synziphosurine genera with fossil showing evidence of appendages, the other ones being Weinbergina, Anderella and Camanchia. Despite often being aligned close to horseshoe crabs, it has been found that Venustulus and its relatives form a group made up of various basal euchelicerate arthropods more distant to the xiphosurans.

<span class="mw-page-title-main">Weis Earth Science Museum</span> Museum in Menasha, Wisconsin, US

Weis Earth Science Museum, located at 1478 Midway Rd, on the University of Wisconsin–Oshkosh, Fox Cities Campus in Menasha, Wisconsin, USA, was opened in 2002. It focuses on Wisconsin geology and its mining history. As such, it was designated as the Official Mineralogical Museum of Wisconsin by then-Governor Tommy Thompson in 2000, prior to its construction.

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