Waukesha Biota

The Waukesha Biota (also known as Waukesha Lagerstätte, Brandon Bridge Lagerstätte, or Brandon Bridge fauna) is an important fossil site located in

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 scavengers 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 coating, which is observed on many of the fossils.^{[1][2][6][7][5][3]}

Biota

Alga

One genus of dasycladalean alga is known from the lagerstätte.^[8]

Hemichordata

Many of the

Hemichordata
Genus	Phylum	Higher taxon	Abundance	Notes	Images
Desmograptus	Hemichordata	Graptolithina		A graptolite of the order Dendroidea that is characterized by its unique branching pattern and conical rhabdosomes.
Dictyonema	Hemichordata	Graptolithina		A graptolite of the order Dendroidea. These colonial organisms are characterized by a conical, net-like structure. The colonies (known as rhabdosomes) are branched and may vary from almost discoidal to almost cylindrical. They were stationary suspension feeders .
Oktavites	Hemichordata	Graptolithina		A graptolite of the order Bireclinata that formed a spiral-like pattern.
Thallograptus?	Hemichordata	Graptolithina		A graptolite of the order Dendroidea that formed branching structures, and often incrusted other organisms.

Porifera

Poriferans, also known as sea sponges, are rare in this locality, with only one specimen known.^[12]

Cnidaria

The cnidarians of the site are mainly represented by conulariids, but coral are also known.^[10]

Cnidaria
Genus / Taxon	Phylum	Higher taxon	Abundance	Notes	Images
Metaconularia	Cnidaria	Staurozoa		A genus of conulariid, which are a somewhat enigmatic group that are now considered possible members of the group Staurozoa. In this image, figures A and B show specimens of Metaconularia.
Conularia	Cnidaria	Staurozoa		Conularia is the type genus of the conulariid group, and the main species found at this site is Conularia niagarensis.
Sphenothallus	Cnidaria	Staurozoa		A problematic genus lately attributed to the holdfasts (attachment points) of conulariids. This fossil is found throughout rocks of the Paleozoic.
Tabulata	Cnidaria	Anthozoa		Fossils of undetermined tabulate corals are rare in this biota, but their poor preservation prevents precise identification.

Echinodermata

Echinoderm fossils are rare at the site, but crinoids have been found here.^[10]

Brachiopoda

Like many of the hard shelled organisms known from this site, the brachiopods found here are poorly preserved and rare.^[10][11]

Cephalopoda

Normally common in Silurian deposits, nautiloid cephalopods are known from only a handful of specimens from the Waukesha biota.^[10][11][13]

"Worms"

Multiple soft bodied fossils of "worms" and other vermiform animals are known from the site.^[11][10]

"Worms"
Genus	Phylum	Higher taxon	Abundance	Notes	Images
To be determined	Annelida	Polychaeta		Many fossils of multiple polychaete worms are known from the site, and represent many different groups. Some fossils represent members of the family Aphroditidae, and others have bodies covered in spines.
To be determined	Palaeoscolecida	To be determined		Specimens of vermiform nature from the site have been found and interpreted as members of the palaeoscolecida grouping (which were extinct priapulids ). These are some of the most common worms from this locality, with up to 30 fossils known.
To be determined	Lobopodia	To be determined		Lobopodians are not "traditional" worms, but are instead panarthropods with stubby legs. Some of these fossils were at one point attributed to myriapods. Over 40 specimens are known, which show that the animal was around 4 cm long, and possessed short legs.
To be determined	Uncertain	Cycloneuralia	At least one specimen	An annulated worm. It was thought that it might represent a fossil record, although available characters are limited so it is hard to identify.[14] Shcherbakov et al. (2020) considered it to be a cycloneuralian, possibly a member of the family Ancalagonidae.[15] The specimen was found with a circular structure at one end interpreted as a sucker; however, Braddy, Gass & Tessler (2023) reinterpreted the purported suckered end as a breakage, and consider the specimen to be a molt of a member of Cycloneuralia of uncertain affinities, possibly a priapulid.[16] Its large size, at up to 24-mm wide suggests a predatory lifestyle.[12]

Arthropoda

Arthropods dominate the fauna of the Waukesha biota in both number of specimens and diversity. A wide variety including crustaceans, trilobites, chelicerates, and less familiar groups like thylacocephalans, cheloniellids and marrellomorphs are known. Also found are enigmatic arthropods whose taxonomy has puzzled paleontologists since the sites discovery.^[13][10][11]

Arthropoda
Genus	Phylum	Higher taxon	Abundance	Notes	Images
To be determined	Arthropoda	Trilobita		A currently unnamed species of dalmanitid trilobite. This species is commonly found with its dorsal exoskeleton intact and is sometimes seen in such large numbers that they cover immense surfaces of sediments. It is one of the most abundant arthropods from the site. Other trilobite taxa found in this biota include: Stenopareia, Meroperix, Leonaspis, Scotoharpes, Arctinurus, Distyrax, a calymenid, a phacopid, an otarionid, a cheirurid, and a proetid.
To be determined	Arthropoda	Cheloniellida		A fossil of a possible cheloniellid (a group of arthropods close to trilobites) has been found in the Waukesha biota. This and other fossils were given the name of "Latromirus tridens" in 2014, but the name was not accepted by the ICZN due to its naming not complying with its guidelines. Later on, all but one of those fossils were reassigned to unrelated genera from this site, leaving only one fossil (UWGM 2439) as a possible cheloniellid.
Ceratiocaris	Arthropoda	Phyllocarida		Phyllocarids are a group of primitive crustaceans that first appeared in the Cambrian period and survived to the present day.[17] 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.[18]
Multiple species	Arthropoda	Ostracoda		Aside from trilobites, the other most abundant arthropods from this site are unnamed leperditicopid ostracods that are often preserved as splayed valves. At least two species are present, with the larger of the two reaching about 12-mm in length.
Venustulus	Arthropoda	Chelicerata	Eight specimens	Venustulus is a genus of paraphyletic group of fossil chelicerate arthropods. Venustulus was regarded as part of the clade Prosomapoda. This arthropod appears to be blind due to the lack of eyes on its carapace, suggesting it lived either in deep water or buried in the sediments. Unlike modern horseshoe crabs, the prosomal appendages of Venustulus covered less of the total carapace length. The animal's carapace is semi-circular in shape and has a procurved posterior area.
To be determined	Arthropoda	Chelicerata		There is another possible synziphosurine known from these deposits, but because of the fragmentary state of the remains, they cannot be confidently described as a separate genus from Venustulus.
Thylacares	Arthropoda	Thylacocephala	Six specimens	Thylacares is a genus of thylacocephalan (a grouping of primitive mandibulate arthropods) that most likely lived as a nektonic predator. This animal shares many features with other thylacocephalans (like raptorial appendages, a bivalved carapace, and compound eyes). 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.
To be determined	Arthropoda	Incertae sedis	At least one specimen (UWGM 2450)	A rare vermiform arthropod is known from the biota. It is around 10 cm in length, and possesses a pair of antenniform appendages on its head.
Acheronauta	Arthropoda	Mandibulata	Twenty-three specimens	Acheronauta is a vermiform arthropod that has a multisegmented trunk region, a cephalic carapace, raptorial appendages, a pair of antennae, and two compound eyes. This animal was interpreted as a sister taxa to the thylacocephalans. Acheronauta has also been assessed as a possible basal mandibulate, which are distinguished from other arthropods due to the presence of mandibles . While its specific placement in the mandibulate family tree has not been fully known, it is accepted to occupy a position near the base of the grouping.
To be determined	Arthropoda	Myriapoda?		There are several arthropod fossils known from the biota that have been questionably assigned as myriapods (the grouping including centipedes and millipedes). If the fossils do turn out to be myriapods, then it would make them the first known terrestrial fossils from the site.
Parioscorpio	Arthropoda	incertae sedis		Parioscorpio is an enigmatic arthropod from this site that has stirred up scientific debate since it was first described in 1985, decades before it was named. The groups that this creature has been included in are (remipedia, branchiopoda, cheloniellida, and arachnida). This creature's name stems from its initial description in 2020 when it was described as a primitive scorpion. The animal reached a length of around 1.6–4.5 cm (0.63–1.77 in) long. It is characterized by a trapezoidal head with a pair of eyes located antero-medially, a pair of enlarged raptorial appendages (previously thought to be scorpion's clawed pedipalps), as well as another pair of small appendages. Central to the head was a mouth-covering hypostome and a pair of muscular blocks articulated to the raptorial appendages. Based on its gnathobases, it seems that it hunted prey like trilobites and worms.[12]
To be determined	Arthropoda	Marrellomorpha		In 2015, paleontologists announced the discovery of a Furca mauretanica" from the Fezouata biota in Morocco. Appendages are rare, but some of the specimens seem to preserve antennae and trunk appendages.
To be determined	Arthropoda	incertae sedis		One of the more mysterious organisms from this site is a currently unnamed bivalved arthropod. This creature has been given the nickname of the "Butterfly animal" by some subsequent studies on the sites fauna.[13] This is due to the appearance this creature has to the completely unrelated lepidopteran insects. The largest known specimens have a width of around 20 centimeters (7.8 inches) in width. One of the more supported hypotheses that paleontologists have made on this arthropod's taxonomy is that it is some kind of crustacean, with some suggesting it could be related to phyllocarids, but whether these similarities are just superficial is still being studied.[11] Most specimens known preserve the "Open-valve position", but one specimen does preserve the lateral view.[12]

Chordata

Multiple chordate fossils (possibly belonging to conodonts) are known from this site.^[13][11]

Chordata
Genus	Phylum	Higher taxon	Abundance	Notes	Images
Panderodus	Chordata	Conodonta		A bedding plane assemblage of Panderodus conodont elements and associated soft tissues including myomeres was found in the Waukesha Biota. Grooves on the elements were suggested to possibly accommodate the flow of venom, but this function is not supported by other evidence. At the time of its discovery, the Waukesha Biota was only the second occurrence known to produce the soft parts of a conodont. The fossil belonged to the species P. unicostatus, and revealed that this species was most likely a macrophagous predator.
To be determined	Chordata	Conodonta?		Numerous, well-preserved chordate fossils that may also be conodont animals were later found in the Waukesha Biota at Franklin Quarry.

See also

• Eramosa lagerstätte, a middle Silurian aged lagerstätte in Ontario, Canada
• Soom Shale lagerstätte, an Upper Ordovician aged lagerstätte in South Africa

References