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.
Many
metamorphic,
igneous and
sedimentary rock units are exposed in the north-central part of Wisconsin. Although they are mostly barren of fossils, some of the sedimentary ones contain
stromatolites.[1][2]
Exposures of Cambrian rock units, many of which are fossiliferous, occur in western and central Wisconsin, especially along the banks of the Mississippi, Saint Croix and Wisconsin Rivers. Most of the rocks are Upper Cambrian; however, others are thought to be Middle Cambrian. Fossils of many groups of organisms have been found including stromatolites,
conulariids,
brachiopods,
gastropods,
monoplacophorans,
trilobites,
graptolites, and
conodont elements. Wisconsin’s Cambrian rocks have also produced fossils of more
aglaspidid (a grouping of arthropods closely related to trilobites) species (around 12) than those of any other state. A portion of central Wisconsin known as
Blackberry Hill is a
Konservat-Lagerstätte famous for its many types of trace fossils, mass strandings of
jellyfish, and especially for producing fossils of one of the first animals to emerge from the sea and walk on land (i.e., a species of
euthycarcinoid).[3][4]
Climactichnites wilsoni, these trails were made by a large, slug-like mollusk at
Blackberry Hill. These examples are about 10 cm wide.
The trackway Protichnites from
Blackberry Hill. These are believed to be some of the first footprints made on land. They were made by the euthycarcinoid arthropod Mosineia
The
euthycarcinoidMosineia macnaughtoni---the presumed maker of some of the Protichnites at
Blackberry Hill, and hence one of the first animals to emerge from the sea and walk on land.
A conceptual drawing of M. macnaughtoni producing the Protichnites tracks.
Many fossiliferous Lower to Upper Ordovician rock units are exposed in the southwestern portion of Wisconsin. During this time, most of Wisconsin was covered in a shallow tropical ocean that teemed with an abundance of life. These include many species of stromatolites,
fungi,
sponges, conulariids,
rugose corals,
tabulate corals,
bryozoans, brachiopods, gastropods, monoplacophorans,
bivalves,
nautiloids, trilobites,
ostracods,
crinoids, graptolites, and conodont elements.[1]
The Ordovician trilobite Isotelus, found in Wisconsin.
Fossiliferous Silurian rocks are exposed in eastern Wisconsin, from the
Door County peninsula to the
Illinois border. Fossils include stromatolites,
stromatoporoids, sponges, conulariids, rugose and tabulate corals, bryozoans, brachiopods, gastropods, monoplacophorans, bivalves, nautiloids, trilobites, ostracods,
phyllocarids,
cystoids, crinoids, graptolites, conodont elements, and jawless fish bones. During the Middle-Late Silurian, the area around modern
Milwaukee contained a massive
reef system. The
fauna that lived there at that time is among the most diverse for its age on the entire continent. Donald G. Mikulic has called it "a textbook example of ancient reefs."[5] Also of much significance is the
Waukesha Biota, which is a Konservat-Lagerstätte famous for its superbly preserved fossils of strange
arthropods,
worms, and other organisms not previously recorded from Silurian rocks. Among the Waukesha Biota's fossil organisms seldom preserved in other Silurian occurrences are a
synziphosurine, a possible
cheloniellid, a
thylacocephalan, a bizarre arthropod called Parioscorpio,
an enigmatic bivalved arthropod,
conodonts,
lobopods,
palaeoscolecids, a
cycloneuralian and other 'worms,'
graptolites, and
chordates.[6][7][8]
Drawing of the Silurian
encrinurid trilobite Mackenziurus lauriae Gass, Edgecombe, Ramskold, Mikulic, and Watkins, 1992.
Venustulus, a synziphosurine arthropod and a distant relative to modern
horseshoe crabs from the Waukesha Biota.
Parioscorpio, an enigmatic arthropod from the Waukesha biota that has been thought of as a crustacean, a trilobite relative, or a
scorpion.
Thylacares, a thylacocephalan arthropod from the Waukesha Biota. Unlike most other members of its grouping, Thylacares had small eyes, and a smaller stomach.
A specimen of the “Waukesha Butterfly Animal”, an unnamed enigmatic arthropod from the Waukesha biota, nicknamed due to its carapace resembling the wings of a butterfly (which it is not related to).
Rocks of Permian to Neogene age were either rarely deposited in Wisconsin or were eroded away by the Pleistocene
glaciers and other erosional agents. As a result,
dinosaurs and other organisms of this age did not leave many fossils in Wisconsin.[1] Some ammonite fossils originating from the
Coleraine Formation and dating to the middle
Turonian epoch of the
Late Cretaceous have been found reworked in glacial till, showing that some fossils from this time are present in Wisconsin. These include the species Placenticeras pseudoplacenta and Scaphites carlilensis.[10]
During the Quaternary, deposition resumed; however, the local climate was cold and glaciers would come to cover nearly all of the state's land area. Wisconsin contains sediment from all of the Pleistocene glacial stages, especially the stage that bears the state's name.
Hemlock and
spruce trees formed forests inhabited by creatures like
giant beavers,
horses, and
woolly mammoths.
History
Polymath naturalist
Increase Allen Lapham is regarded as Wisconsin's first
geologist.[11] During the late 1830s Lapham discovered a wide variety of fossils in great abundance in some rocky hills near Milwaukee.[5] He wondered about the
stratigraphic relationship between the rocks preserving his fossils and those from
New York described in
James Hall's recent research. Lapham sent a sizable sampling of the local fossils to Hall in 1846.[5][11] Hall began researching the area and in 1862 recognized the local
reefs for what they were. The Silurian-aged reefs of the Milwaukee area were the first Paleozoic reefs in the world to be described for the scientific literature. They were also the first fossil reefs in North America to be properly recognized as such. Hall set out to formally describe the fossils of the reef, and found them to be among the most diverse of the period on the entire continent.[5] Lapham died in 1875 and most of his fossils and mineral specimens were sold to the
University of Wisconsin. Sadly, most of his specimens were destroyed nine years later during a fire that consumed the university's science building.[11] During the second half of the 19th century the region was prospected by "gentleman naturalists" who collected fossils on behalf of Hall and other well known paleontologists. Examples include
T. A. Greene and
E. E. Teller who collected near Milwaukee,
P. R. Hoy, who collected near
Racine, and
F. H. Day, who collected in the
Wauwatosa area. In 1877 research by
T. C. Chamberlin uncovered differences in the composition and fossils of the reef-bearing rocks of the Milwaukee area as compared to those that didn't contain reefs. Donald G. Mikulic praised Chamberlin's research on the Milwaukee reefs as "a classic work of
paleoecology and
sedimentology".[5] In the early 20th century the reefs commanded the research attention of figures like
W. C. Alden,
A. W. Grabau, and
R. R. Schrock. Gradually scientific interest in the Silurian reefs of Milwaukee waned along with the decline in local quarrying.[5]
Lapham, Greene, Teller, Day, and another gentleman naturalist,
C. E. Monroe, also gathered extensive collections from the Devonian Milwaukee Formation. The majority of those fossils came from natural cement quarries that operated between 1876 and 1911 along the Milwaukee River in the area now occupied by Estabrook and Lincoln Parks. Greene and some of the others would pay the quarry workers for their fossil finds, resulting in large numbers of high quality fossils. These beds soon became well known for containing one of the most diverse Devonian fish faunas in the United States. Most of that material as well as that collected after closure of the quarries now resides in museums, such as the Thomas A. Greene Geological Museum, Milwaukee Public Museum, Weis Earth Science Museum, Field Museum of Natural History, National Museum of Natural History (Smithsonian), Museum of Comparative Zoology, and Buffalo Museum of Science. Much of that material has not been studied in depth for over one hundred years, but a preliminary study conducted in 2019 indicates that the Milwaukee Formation contains one of the richest and most diverse biotas in North America coming from a single formation of its age.[9]
Other significant, more recent developments in Wisconsin paleontology include the discovery of the
Waukesha Biota and
Blackberry Hill, as discussed above.
Collette, Joseph H.; Kenneth C. Gass & James W. Hagadorn (2012). "Protichnites eremita unshelled? Experimental model-based neoichnology and new evidence for a euthycarcinoid affinity for this ichnospecies". Journal of Paleontology. 86 (3): 442–454.
doi:
10.1666/11-056.1.
S2CID129234373.
Gass, Kenneth C. 2015. Solving the Mystery of the First Animals on Land: The Fossils of Blackberry Hill. Siri Scientific Press., 96 pp.
9780992997953[4]
Gass, Kenneth C., Kluessendorf, Joanne, Mikulic, Donald G. & Brett, Carlton E. 2019. Fossils of the Milwaukee Formation: A Diverse Middle Devonian Biota from Wisconsin, USA. Siri Scientific Press, 224 pp.
9780995749672[5]
Meyer, Ronald C. & Gunderson, Gerald O. (1986). "Discovering a new Silurian soft-bodied fauna Waukesha County, Wisconsin". Rocks and Minerals. 61 (6): 310–319.
doi:
10.1080/00357529.1986.11768462.
Hayes, Paul G. Increase Allen Lapham: Wisconsin's First Geologist. Geoscience Wisconsin. Volume 18. 2001.
[6]
Mikulic, Donald G. The Reefs that Made Milwaukee Famous. Geoscience Wisconsin. Volume 18. 2001.
[7]
Mikulic, Donald G., Briggs, Derek E.G. & Kluessendorf, Joanne. New exceptionally preserved biota from the lower Silurian of Wisconsin, U.S.A. Philosophical Transactions of the Royal Society of London, Series B 311 715-717 (1985).
[8]
Wendruff, Andrew J. 2016. Paleobiology and Taphonomy of Exceptionally Preserved Organisms from the Brandon Bridge Formation (Silurian), Wisconsin, USA. Ph.D Dissertation, Ohio State University.
[9]
Wisconsin Geological and Natural History Survey.
[10]. University of Wisconsin-Madison Division of Extension. Accessed November 15, 2019.