The Waukesha Biota (also known as Waukesha Lagerstätte, Brandon Bridge Lagerstätte, or Brandon Bridge fauna) refers to a Konservat-Lagerstätte ( a fossil site that preserves soft bodied remains) of Early

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleoz ...

( Telychian to Sheinwoodian) age found within the Brandon Bridge Formation in Waukesha County and Franklin, Milwaukee County, Wisconsin. It is known for the exceptional preservation of its diverse, soft-bodied and lightly skeletonized taxa, including many major

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

found nowhere else in strata of similar age. The sites discovery was announced in 1985, thus leading to a wide plethora of discoveries being made. This biota is one of the few well studied lagerstättes from the Silurian, making it very important in our understanding of Silurian faunas. Some of the taxa found here are not easily classified into known animal groups, showing that there is a great amount of studying that needs to be done on this site. Other taxa that are normally common in other Silurian deposits are rare here, but

Trilobites Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the A ...

are still quite common in the area. This site is also important because it shows that while Wisconsin's paleontology is often overlooked, it still provides exceptional insights concerning the history and diversity of life on

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...

History and significance

Prior to the discovery of the Waukesha Biota, very little was known about the soft-bodied animals that were sure to have lived in the Silurian seas. Thanks to the famous Burgess Shale of the

Canadian Rockies The Canadian Rockies (french: Rocheuses canadiennes) or Canadian Rocky Mountains, comprising both the Alberta Rockies and the British Columbian Rockies, is the Canadian segment of the North American Rocky Mountains. It is the easternmost part ...

, scientists knew that the seas were already teeming with soft-bodied and lightly skeletonized animals as far back as the

Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago ...

, yet relatively few were known to be preserved in later

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ...

rocks. This is because the fossil record is greatly skewed toward biomineralized skeletal remains. The announcement of the Waukesha Biota in 1985 thus marked a major turning point in our knowledge of Silurian life. In his popular book, '' Wonderful Life'',

Stephen Jay Gould Stephen Jay Gould (; September 10, 1941 – May 20, 2002) was an American paleontologist, evolutionary biologist, and historian of science. He was one of the most influential and widely read authors of popular science of his generation. Goul ...

compared the "anatomical disparity" of the Burgess Shale with that of only five other occurrences in the world –one of which was the Waukesha Biota, which he referred to as the "Brandon Bridge fauna"– and none of the others were Silurian. Other “soft-bodied” Silurian sites have turned up in more recent years, but none have produced the high diversity of soft-bodied animals observed in this biota. The exceptional preservation of the fossils of the Waukesha Biota thus provides a window to a significant portion of Silurian life that otherwise may have been undetected and therefore unknown to science. Currently fossils from the biota are on display in the UW–Madison Geology Museum.

Stratigraphy and depositional environment

Most of the Waukesha Biota is preserved within a layer of thinly-laminated, fine-grained, shallow marine sediments of the Brandon Bridge Formation consisting of

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from '' shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology.' ...

and

dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...

deposited in a sedimentary trap at the end of an erosional scarp over the eroded dolomites of the Schoolcraft and Burnt Bluff Formations. A separate thin bed containing the biota is also present about above the interval. Fossils of unambiguous, fully terrestrial organisms are lacking from the Waukesha Biota. Most of the Waukesha Biota fossils were found at a quarry in Waukesha County, Wisconsin, owned and operated by the Waukesha Lime and Stone Company. Other fossils were collected from a quarry in Franklin, Milwaukee County, owned and operated by Franklin Aggregate Inc. That quarry lies south of the quarry in Waukesha. The Franklin fossils were from blasted material apparently originating from a horizon and setting equivalent to that of the Waukesha site. Its biota is similar to that from the Waukesha site, except that it lacks

trilobites Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the A ...

Taphonomy

The Waukesha Biota is unusual in preserving few of the kinds of animals that typically dominate the Silurian fossil record, including in other strata of the same two quarries. Fossils of

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and se ...

echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the ...

brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, w ...

s, bryozoans,

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of marine and freshwater Mollusca, molluscs that have laterally compressed bodies enclosed by a shell consisting of two hing ...

s, and

cephalopods A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, a ...

are rare or absent from the Waukesha Biota, although

trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the ...

s are diverse and common. The exceptional preservation of non-biomineralized and lightly skeletonized remains of the Waukesha Biota is generally attributed to a combination of favorable conditions, including the transportation of the organisms to a sediment trap that was hostile to predators but favorable to the production of organic films that coated the surfaces of the dead organisms, which inhibited decay, sometimes enhanced by promoting precipitation of a thin

phosphatic In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phospho ...

coating, which is observed on many of the fossils.

Biota

Green algae

Carbonized fossils of a noncalcified dasycladalean

alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

of the family triploporellaceae have been found at the Waukesha site and were given the name of ''Heterocladus waukeshaensis''.

Arthropods

The fossil record of the Waukesha Biota is dominated by

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...

s, both in number of fossils and number of species. This is even true when excluding

s and

ostracods Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typica ...

, which in most Early

marine biotas are the source of the vast majority or all of the arthropod fossils. This is due to preservational conditions which protect soft and lightly skeletonized tissues from decomposition but select against preservation of biomineralized skeletal remains. Many of the arthropods include

crustaceans Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean g ...

, chelicerates, and some of questionable taxonomy.

Chelicerate

File:20200814 Venustulus waukeshaensis.png, ''

Venustulus ''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 ...

'', a

Synziphosurine Synziphosurina is a paraphyletic group of chelicerate arthropods previously thought to be basal horseshoe crabs (Xiphosura). It was later identified as a grade composed of various basal euchelicerates, eventually excluded form the monophyletic Xi ...

arthropod that is distantly related to modern horseshoe crabs. File:Fossil specimen of Venustulus (Synziphosurina) from the Waukesha lagerstätte.jpg, A fossil of Venustulus from the Waukesha Biota. Well preserved fossils of a

chelicerate The subphylum Chelicerata (from New Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. It contains the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, and mite ...

(the grouping of arthropods including

arachnids Arachnida () is a class of joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, harvestmen, camel spiders, whip spiders and vinegar ...

sea spiders The sea, connected as the world ocean or simply the ocean, is the body of salty water that covers approximately 71% of the Earth's surface. The word sea is also used to denote second-order sections of the sea, such as the Mediterranean Se ...

, etc) have been found in this biota and belong to the

Synziphosurina Synziphosurina is a paraphyletic group of chelicerate arthropods previously thought to be basal horseshoe crabs (Xiphosura). It was later identified as a grade composed of various basal euchelicerates, eventually excluded form the monophyletic Xi ...

(A extinct group distantly related to

horseshoe crab Horseshoe crabs are marine and brackish water arthropods of the family Limulidae and the only living members of the order Xiphosura. Despite their name, they are not true crabs or crustaceans: they are chelicerates, most closely related to ar ...

s). This species was named ''

waukeshaensis''. The genus name ''Venustulus'' derives from

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

and means "charming", while the species name ''waukeshaensis'' is derived from the town of Waukesha. The creature was possibly blind (due to the lack of any noticeable eyes) and is known from eight specimens, three of which are almost complete and the other five only being the

prosoma The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cepha ...

and

opisthosoma The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma (cephalothorax). It is a distinctive feature of the subphylum Chelicerata (arachnids, horseshoe crabs and others). Although it is similar in most respects to ...

of the arthropod. The five-six pair of appendages seen in ''Venustulus'' contrasts the seven usually seen in other synziphosurans, possibly suggesting that this creature represents a more derived form than other members of its grouping. This arthropods taxonomy is not fully understood, but is believed to belong to the family Weinberginidae (alongside ''

Weinbergina ''Weinbergina'' is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Fossils of the single and type species, ''W. opitzi'', have been discovered in deposits of the Devonian period in the Hunsrück Slate, Germany. ...

'', ''

Legrandella ''Legrandella'' is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. ''Legrandella'' was regarded as part of the clade Prosomapoda. Fossils of the single and type species, ''L. lombardii'', have been discovered i ...

'' and '' Willwerathia)''. Interestingly it seems there could be another possible synziphosuran from the same deposits as ''Venustulus'', but the fossils are too fragmentary to consider it a unique genus.

Thylacocephalans

File:Thylacares brandonensis S12862-014-0159-2-1.jpg, alt=, Fossil specimen UWGM 1748 of '' Thylacares brandonensis'' File:Fossil of Thylacares from the Waukesha biota site in Wisconsin.jpg, Fossil specimen of ''Thylacares'' File:Thylacares brandonensis chasing after prey.png, Life reconstruction of ''Thylacares'', chasing a

flatworm The flatworms, flat worms, Platyhelminthes, or platyhelminths (from the Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") are a phylum of relatively simple bilaterian, unsegmen ...

'' Thylacares brandonensis'' is the name given to one of the oldest known unequivocal Thylacocephalans, which were an enigmatic group of possible

having a pair of raptorial appendages and a bivalved shield that enclosed most of the body, and survived until the

upper Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

. This species is distinguishable from other thylacocephalans by its smaller raptorial appendages and compound eyes. All of the known specimens are kept in the UW geology museum. The body is fully encased in a bivalved shell, with only the eyes protruding on stalks. ''Thylacares'' means "Small pouch" in reference to the small eyes and stomach seen in the species. The species' trunk is composed of about 22 segments. Originally this genus was thought to have been the oldest known thylacocephalan, however recently two new genera from the

czech republic The Czech Republic, or simply Czechia, is a landlocked country in Central Europe. Historically known as Bohemia, it is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the southeast. The ...

, ''Pseudoprotozoea'' and ''Bohemiacaris'' from the upper

Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. T ...

now hold this record. This creature represents one of the few known thylacocephalan species from the Silurian, with one of the few being the Scottish genus '' Ainiktozoon''.

Mandibulate

alt=Reconstruction of Acheronauta stimulapis based on "Morph A" specimens, 220x220px, Reconstruction of '' Acheronauta stimulapis'' based on "Morph A" specimens Fossils of a vermiform arthropod have been known from the biota since 1985. In 2022 these fossils were properly described and given the name of '' Acheronauta stimulapis''. The paper describing this creature found it to be a possible basal mandibulate (the grouping of arthropods including

insects Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of j ...

and crustaceans). This creature had a long worm like body, a shielding carapace covering its head, a pair of antennae coming off the head, and a set of appendages coming from below the carapace. Currently it is thought that this arthropod forms a previously unknown

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

with the

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wh ...

stem-group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

arthropod ''Captopodus'', and the thylacocephalans. ''A. stimulapis'' has been recognized as one of the most common animals of the biota, with over 20 specimens being known. ''Acheronauta'' derives from the

latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

word ''Acheronta'', which is a Latinizing of the Greek river '' Acheron'', which itself is another name for the River of Woe, a

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of ...

of the

Greek underworld In mythology, the Greek underworld, or Hades, is a distinct realm (one of the three realms that makes up the cosmos) where an individual goes after death. The earliest idea of afterlife in Greek myth is that, at the moment of death, an individu ...

. The last part of the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

name ''-nauta'' means "sailor". This name is a reference to the harsh environments of Silurian Waukesha that allowed for this site to be preserved. The

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

name ''Stimulapis'' derives from the latin words ''Stimulas'' which means sting, and ''apis'' which means

bee Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyletic lineage within the superfami ...

. The specific

epithet An epithet (, ), also byname, is a descriptive term (word or phrase) known for accompanying or occurring in place of a name and having entered common usage. It has various shades of meaning when applied to seemingly real or fictitious people, di ...

translates to ‘sting like a bee’, which according to the authors of the paper is in honor of the American boxer

Muhammad Ali Muhammad Ali (; born Cassius Marcellus Clay Jr.; January 17, 1942 – June 3, 2016) was an American professional boxer and activist. Nicknamed "The Greatest", he is regarded as one of the most significant sports figures of the 20th century, ...

Marrellomorphs

In 2015, paleontologists announced the discovery of a marrelomorph, a bizarre grouping of arthropods that first originated in the Cambrian whose taxonomic relationships are currently uncertain, from the biota. About five specimens are known with each having a varying level of completion, with some preserving the cephalic and trunk regions of the body. Certain characteristics of the fossils suggest a possible relation with "'' Furca mauretanica''" from the Fezouata biota in

Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to A ...

, and a

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

preformed seemed to confirm this thought. Appendages are rare, but some of the specimens seem to preserve antennae and trunk appendages. This discovery is significant as the only other known Silurian marrellomorph is '' Xylokorys chledophilia'' from the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and ...

. This means that this creature was the first known post-

marrellomorph from the

United states The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

, and

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

in general.

Phyllocarids

FMIB 46280 Ceratiocaris papilio, one of the fossil Phyllocarda

Phyllocarids are a group of primitive

that first appeared in the

period and have survived to the modern day. Three species of phyllocarids are part of the Waukesha Biota, consisting of '' Ceratiocaris macroura'', ''C. papilio'', and ''C. pusilla''. Although these bivalved crustaceans are not new to science, their fossils preserve the delicate appendages and further show the diversity of the lightly biomineralized fossils of the Waukesha Biota.

Myriapods

Several fossils appearing to be

myriapod Myriapods () are the members of subphylum Myriapoda, containing arthropods such as millipedes and centipedes. The group contains about 13,000 species, all of them terrestrial. The fossil record of myriapods reaches back into the late Silurian, ...

s (the group that includes

millipede Millipedes are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derived from this feature. Each double-legged segment is a resu ...

s and

centipede Centipedes (from New Latin , "hundred", and Latin , " foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', lip, and New Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, ...

s) are part of the Waukesha Biota.

Other arthropods

File:Meroperyx.jpg, The styginid trilobite '' Meroperyx'' File:Dalmanitid trilobite.jpg, An unnamed Dalmanitid trilobite; the most abundant arthropod of the biota Other kinds of arthropods having varying degrees of biomineralization of their skeletal elements are also present in the Waukesha Biota, including leperditicopid

ostracod Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typic ...

s (

crustacea Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group c ...

), and about thirteen species of

s, several of which are new. Some trilobite taxa preserve their digestive tracts. An unnamed dalmanitid is commonly found with its dorsal exoskeleton intact and sometimes seen in such numbers that they cover large surfaces of sediment. Some other

do not readily fit within existing arthropod groups, such as the very common “Butterfly animal”, a small enigmatic arthropod that has stumped paleontologists since it was discovered along with the biota in 1985. Despite this animal being named after a

butterfly Butterflies are insects in the macrolepidopteran clade Rhopalocera from the order Lepidoptera, which also includes moths. Adult butterflies have large, often brightly coloured wings, and conspicuous, fluttering flight. The group compris ...

, it is not actually an

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...

. This creatures nickname derives from two large wing like projections that extended from the sides of its body. Whether the extensions flapped like wings or were a

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

shield protecting the arthropod's body is uncertain. The largest known specimens have a width of around 20 centimeters (7.8 inches) in width. One of the more supported

hypotheses A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obse ...

that paleontologists have made on this arthropods taxonomy is that it is some kind of

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapoda, decapods, ostracoda, seed shrimp, branchiopoda, branchiopods, argulidae, fish lice, krill, remipedes, isopoda, isopods, barnacles, copepods, ...

, with some suggesting it could be related to phyllocarids, but whether these similarities are just superficial is currently up in the air. File:Parioscorpio fossil.png, Multiple specimens of the enigmatic arthropod '' Parioscorpio venator'' File:20211029 Parioscorpio venator.png, Reconstruction of ''P''. ''venator'' as a non-scorpion arthropod File:20211104 Parioscorpio raptorial appendages mobility.gif, The suggested movement of the raptorial appendages of ''P. venator'' Another enigmatic arthropod from the Waukesha Biota is ''Parioscorpio'' ''venator'' (Wendruff et al., 2020). Having a pair of sub-chelate great appendages, multiramous anterior trunk appendages, filamentous fan-like rear trunk appendages, and a lack of antennae, this peculiar species has been classified over the years under different arthropod groups. In 1985 when it was first discovered, it was thought to have either been a

remipede Remipedia is a class of blind crustaceans found in coastal aquifers which contain saline groundwater, with populations identified in almost every ocean basin so far explored, including in Australia, the Caribbean Sea, and the Atlantic Ocean. The ...

branchiopod Branchiopoda is a class of crustaceans. It comprises fairy shrimp, clam shrimp, Diplostraca (or Cladocera), Notostraca and the Devonian '' Lepidocaris''. They are mostly small, freshwater animals that feed on plankton and detritus. Descript ...

crustacean. In that same year, the arthropod was given the unofficial nickname of the "Hellgrammite animal" due to its close resemblance to a Hellgrammite, which is the

larvae A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. T ...

of modern day dobsonflies. In 2020 when it was first described it was interpreted as the oldest known

scorpion Scorpions are predatory arachnids of the order Scorpiones. They have eight legs, and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always en ...

, hence its name meaning “Progenitor scorpion”. In 2021 it was reinterpreted as either an arthropod of uncertain placement, or a cheloniellid (a grouping of arthropods close in relation to trilobites). Further study appears to have reaffirmed a possible affinity with the Cheloniellida, however this interpretation was denied in a later study, making this

taxon In biology, a taxon ( back-formation from '' taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular n ...

enigmatic again. In 2014, scientists described ''Latromirus tridens'', a supposed cheloniellid from the biota, but because the naming of the animal did not meet the standards of the

ICZN The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. It is also informally known as the ICZN Code, for its publisher, the I ...

, its name was considered a

nomen nudum In taxonomy, a ''nomen nudum'' ('naked name'; plural ''nomina nuda'') is a designation which looks exactly like a scientific name of an organism, and may have originally been intended to be one, but it has not been published with an adequate desc ...

. Later on it was revealed that many of the fossils of ''L. tridens'' were actually those of ''P. venator'', possibly rendering ''L. tridens'' as a

junior synonym The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. * In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linn ...

. Specimen UWGM 2439, once described invalidly as a fossil of ''Latromirus'', still has a possibility to be a distinct cheloniellid, but could also be a specimen of ''Parioscorpio''. Other arthropods are either not yet described or cannot be confidentially classified. One example of this is the specimen UWGM 2339, which is an arthropod appendage discovered in the biota. Currently it is thought to be the grasping appendage of a

Radiodont Radiodonta is an extinct order of stem-group arthropods that was successful worldwide during the Cambrian period. They may be referred to as radiodonts, radiodontans, radiodontids, anomalocarids, or anomalocaridids, although the last two original ...

, a group of primitive

arthropods that thrived in the oceans of the

, with some

and

specimens.Van Roy, P.; Briggs, D. E. G. (2011). "A giant Ordovician anomalocaridid". Nature 473 (7348): 510–513. doi:10.1038/nature09920. edit If this classification is correct, this would not only be the first radiodont known from Wisconsin, it is also would be the first one known from Silurian rock layers.

Lobopods

Several unnamed species of lobopods (worm-like panarthropods with annulated appendages) are known from the Waukesha Biota. One of these was originally thought to be a

arthropod until further study revealed key lobopod characteristics.

"Worms"

Many exquisitely preserved vermiform fossils, some preserving digestive tracts, are part of the Waukesha biota. These include

annelid The annelids (Annelida , from Latin ', "little ring"), also known as the segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecol ...

s, such as an aphroditid polychaete, a spiny polychaete, and an annelid that appears to have a sucker disc at one end. If this proves to be a

leech Leeches are segmented parasitism, parasitic or Predation, predatory worms that comprise the Class (biology), subclass Hirudinea within the phylum Annelida. They are closely related to the Oligochaeta, oligochaetes, which include the earthwor ...

, it would be the first unequivocal fossil leech ever recorded. Another worm-like taxon in the biota is identified as a

palaeoscolecid The palaeoscolecids are a group of extinct ecdysozoan worms resembling armoured priapulids. They are known from the Lower Cambrian to the late Silurian; they are mainly found as disarticulated sclerites, but are also preserved in many of the Camb ...

. Scolecodonts, which are the fossilized jaws of polychaete worms, have also been found in this biota.

Hemichordates

Several genera of the hemichordates known as graptolites, including ''Oktavites'', ''Desmograptus'', '' Dictyonema'', and ''Thallograptus''?, are reported from this biota.

Chordates

A body fossil of a Panderodus unicostatus (Branson & Mehl, 1933) from the Waukesha Lagerstätte of Wisconsin, USA

A fossil of '' Panderodus,'' a genus of

conodont Conodonts ( Greek ''kōnos'', " cone", + ''odont'', "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, whi ...

animal, which were primitive, eel-like

chordate A chordate () is an animal of the phylum Chordata (). All chordates possess, at some point during their larval or adult stages, five synapomorphies, or primary physical characteristics, that distinguish them from all the other taxa. These fi ...

s now known to be the source of certain small, phosphatic, tooth-like structures long-used in the dating of strata and now known as " conodont elements," has also been found. An assemblage of conodont elements were found associated with this fossil. The fossil reveals that this conodont was a macrophagous predator (meaning it fed on large prey items.) It also showed that this creature had a more tapering, larger body compared to most other conodonts. A certain groove on the elements of ''Panderodus'' has been suggested to accommodate the flow of

venom Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a st ...

, meaning that this genus may have been one of the first venomous animals. The Waukesha Biota was only the second occurrence to produce a conodont animal. Numerous, well-preserved chordate fossils that may also be conodont animals were later found in the Waukesha Biota at Franklin Quarry.

Other animal taxa

The Waukesha Biota includes fossils of many fragmentary, unidentifiable, nonbiomineralized and lightly biomineralized skeletal elements that may belong to additional taxa. It also includes fossils of

conulariid Conulariida is a poorly understood fossil group that has possible affinity with the Cnidaria. Their exact position as a taxon of extinct medusozoan cnidarians is highly speculative. Members of the Conulariida are commonly referred to as conularii ...

s and certain biomineralized taxa that are common in typical Silurian marine occurrences, but are rare or uncommon here, including

tabulate coral Tabulata, commonly known as tabulate corals, are an order of extinct forms of coral. They are almost always colonial, forming colonies of individual hexagonal cells known as corallites defined by a skeleton of calcite, similar in appearance to ...

cephalopod A cephalopod is any member of the molluscan class Cephalopoda ( Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head ...