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The Waukesha Biota (Brandon Bridge Formation Lagerstätte) is a diverse assemblage of early Silurian (437 Ma) shallow marine fossils from Wisconsin, USA. Their exceptional preservation, in finely laminated dolomitic mudstones, was mediated by tidally‐influenced conditions and/or microbial entombment. Shelly biomineralized animals are rare, but soft‐bodied organisms are common. Arthropods dominate, including trilobites, phyllocarids, ostracodes, a thylacocephalan, a synziphosurine and various enigmatic groups. The fauna also includes evolutionary 'holdovers', such as palaeoscolecids and a lobopodian. [ABSTRACT FROM AUTHOR]

An unusual worm, previously interpreted as the earliest leech, is described from the early Silurian (Llandovery, Telychian) Brandon Bridge Formation Lagerstätte (Waukesha Biota) of Wisconsin (~437 Ma). Lacking preserved internal organs, it is up to ~16 cm long, 8.2 mm wide, with ~250 annulations and a circular structure at one end, interpreted here as the broken end of a molt. It is therefore referred to Cycloneuralia incertae sedis. [ABSTRACT FROM AUTHOR]