Paleofauna of the Mazon Creek fossil beds

This is a list of the fauna of the Mazon Creek fossil beds, a Carboniferous lagerstätte located in Grundy County, Illinois. The site is famous for its exceptional preservation of soft bodied fossils inside of ironstone concretions, and was one of the first fossil sites discovered to preserve soft bodied fossils.

The Mazon Creek fossil beds are around 309-307 million years old, being approximately Moscovian in age. During the Carboniferous, this area was a lush, tropical delta system, about 10° north latitude of the equator. This ecosystem was formed by at least one river system that flowed in from the northeastern united states and met the ocean to form an Estuarine environment. This large amount of habitat led to the creation of a very diverse ecosystem, which has been divided into two main sections, the marine Essex fauna, and the terrestrial/freshwater Braidwood fauna. Since the site's discovery in the early 20th century, more than 700 species of flora and fauna have been discovered, some of which have only been found at this site. Because of the diverse habitat types, many different groups, such as arthropods, mollusks, hemichordates, cnidarians, chondrichthyans, actinopterygians, tetrapods and various other groups are represented..

Fauna

Cnidaria A number of Cnidarians are known from Mazon Creek, and show the diversity of taxa in the ecosystem. CnidariaGenusGroupHigher taxonSpeciesNotesImagesEssexellaCnidariaActiniaria E. asheraeOne of the most abundant taxa from Mazon Creek, Originally described as a scyphozoan in 1979, but was later re-described as an actiniarian in 2023ReticulomedusaCnidariaIncertae sedis R. greeneiAnother cnidarian once described as a scyphozoan, but most likely represents a synonym of EssexellaAnthracomedusaCnidariaCubozoa A. turnbulliA jellyfish, though not a member of the Scyphozoa (true jellyfish) but instead a cubozoan (box jellyfish)OctomedusaCnidariaCoronatae? O. pieckorumA bizarre scyphozoan, originally considered to be a basal coronatan (crown jellyfish), however this has been questioned by later studiesDrevotellaCnidariaHydroidolina D. proteanaA cnidarian, and a member of the Hydroidolina within the HydrozoaMazohydraCnidariaHydroidolina M. megaberthaAnother hydrozoan, and one of the first fossil taxa from the class to be discovered

Annelida A number of annelid worms are known from Mazon Creek. AnnelidaGenusGroupHigher taxonSpeciesNotesImagesCoprinoscolexAnnelidaEchiura C. ellogimusOriginally considered to be the oldest definitive echiuran (spoon worms), before the discovery of taxa from Castle BankRhaphidiophorusAnnelidaAmphinomida R. hystrixA member of the Amphinomida, and one of the earliest known members of the group, nicknamed the 'Oliver Hardy Worm'EsconitesAnnelidaEunicida E. zelusA member of the Eunicida, showing the distinctive mouthparts, of the group, and reaches around 14 cm.Thompson, I., & Johnson, R. G. (1977). New fossil polychaete from Essex, Illinois. Fieldiana. Geology, 33(25), 471–487. http://doi.org/10.5962/bhl.title.5176MazovermesAnnelidaincertae sedis M. magnaterminusA bizarre annelid featuring broad posterior parapodia and segments, giving it a very distinctive appearance compared to other fossil polychaetesMazopherusaAnnelidaTerebellida M. prinosiA member of the Flabelligeridae family (fan worms), and one of the few known fossil taxa from the familyDidontogasterAnnelidaPhyllodocida D. cordylinaA phyllodocid often nicknamed the 'Tummy Tooth Worm', named after the swollen section of its body containing the worms mouthpartsLevisettiusAnnelidaPhyllodocida L. campylonectusA phyllodocid often nicknamed the 'Riccardo Worm'AstreptoscolexAnnelidaPhyllodocida A. anasillosusA phyllodocid often nicknamed the 'Plain Worm'RutellifronsAnnelidaPhyllodocida R. wolfforumA phyllodocid often nicknamed the 'Shovel Nose Worm'PieckoniaAnnelidaPhyllodocida P. helenaeA phyllodocid often nicknamed the 'Fish Worm'FossundecimaAnnelidaPhyllodocida F. konecniorumA phyllodocid often nicknamed the 'Simple Jaw Worm', one of the most common worms of the Essex FaunaDryptoscolexAnnelidaPhyllodocida D. matthiesaeA phyllodocid often nicknamed the 'Rat Worm'HystriciolaAnnelidaPhyllodocida H. delicatulaA phyllodocid often nicknamed the 'Baby Tooth Worm'FastuoscolexAnnelidaPhyllodocida F. gemmatusA phyllodocid often nicknamed the 'Papillae Worm'

Mollusca A very large number of Mollusks are known from Mazon Creek, with Multiple classes being represented.

Polyplacophora and Gastropoda Various polyplacophorans (chitons) and gastropods (snails and their relatives) are known from the area. Polyplacophora and GastropodaGenusGroupHigher taxonSpeciesNotesImagesGlaphurochitonPolyplacophoraLepidopleuridae P. concinnusA chiton found with a very well-preserved radula, which is almost identical to that of modern speciesEuphemitesGastropoda (?)Euphemitidae E. richardsoniA bizarre mollusk belonging to the Bellerophontida, whose taxonomy has not yet been fully resolvedHypeselentomaGastropodaGosseletinidae H. cf. perhumerosaA gosseletinid gastropod known from various other localitiesStraparollusGastropodaStraparollinidae S. sp.NaticopsisGastropodaNeritopsidae N. sp.A gastropod who still has modern relatives in the same familyLozouet, P. (2009). "A new Neritopsidae (Mollusca, Gastropoda, Neritopsina) from French Polynesia". Zoosystema 31(1): 189-198. PDF.StrobeusGastropodaSoleniscidae S. cf. primigenius

Bivalvia A large number of bivalves are known from Mazon Creek, and by far represent the most diverse and abundant group of mollusks from the area. {| class="wikitable sortable mw-collapsible" ! colspan="7" align="center" |Bivalvia |- !Genus !Group !Higher taxon !Species !Notes !Images |- |Mazonomya |Solemyida |Solemyidae | M. mazonensis |A solemyid, and one of the most abundant bivalves from Mazon Creek, known from the Chowder Flats locality among others, and often nicknamed 'Clam-Clam'

|Posidonia(PDF) Paleobiology, Paleoecology, and Systematics of Solemyidae (Mollusca: Bivalvia: Protobranchia) from the Mazon Creek Lagerstätte, Pennsylvanian of Illinois |Pteriida |Myalinidae | P. fracta|

Cephalopoda A number of cephalopods are known from Mazon Creek, including shelled taxa, and basal coleoids. CephalopodaGenusGroupHigher taxonSpeciesNotesImagesSaundersites ColeoideaBelemnoidea S. illinoisiensis A genus of basal coleoid within the Belemnoidea, however it is too poorly understood for a more specific placement, known from arms and radulasPaleocadmusNautiloideaIncertae sedis P. herdinae P. pohliA nautiloid from mazon creek known mainly from isolated radulas and beaks, however, the species P. pohli is known from a body outline. The controversial taxon Pohlsepia, which was originally interpreted as an octopus of the Cirrina suborder, has since been synonymized with this taxonBactritesNeocephalopodaBactritidae B. sp.A straight shelled (orthoconic) cephalopod, and a member of the BactritidaWiedeyocerasAmmonoideaWiedeyoceratidae W. sp.A member of the Ammonoidea, more specifically a goniatite. Fossils of this genus have been tentatively reported from Mazon CreekUnidentified schistoceratidAmmonoideaSchistoceratidae Schistoceratid. spFossils from this site have been placed within the goniatite family Schistoceratidae, however genus level identification has not been foundStearocerasNautiloideaGrypoceratidae S. sp.A coil-shelled nautiloid, and a distant relative of modern nautilidsTitanocerasNautiloideaGrypoceratidae T. sp.A fairly large sized member of the Grypoceratidae, with a shell diameter of around 8 in (20 cm) being recorded

Brachiopoda A small number of brachiopods are known from Mazon Creek. BrachiopodaGenusGroupHigher taxonSpeciesNotesImagesLingula (?)BrachiopodaLingulida L. sp.A common brachiopod in the fossil record, however the majority of specimens most likely represent unrelated species, and definitive specimens of the genus are only known from the CenozoicOrbiculoideaBrachiopodaDiscinida O. sp.Another common brachiopod in the fossil record, known for its near circular, disk-shaped shellUnidentified chonetoidsBrachiopodaStrophomenidaVarious speciesSeveral undescribed brachiopods in Strophomenida order are known from the site

Echinodermata Echinoderms are an undiverse faunal component of Mazon Creek.''' BrachiopodaGenusGroupHigher taxonSpeciesNotesImagesAchistrumHolothuroideaAchistridae A. sp.A taxon of footless (without tube feet) sea cucumber known from various species from both North America and EuropeTriassic Holothurian Sclerites from Tatra Mountains Krystyna Zawidzka.Unidentified crinoidsCrinoideaVarious groupsVarious speciesA number of undescribed crinoids with stalks (sea lilies) are known from the area

Non-arthropod panarthropoda A small number of non-arthropod panarthropods (notably lobopodians and similar taxa) are known from Mazon Creek. Non-arthropod panarthropodaGenusGroupHigher taxonSpeciesNotesImagesCarbotubulusPanarthropodaHallucigeniidae? C. waloszekiA long-legged lobopodianns originally assigned to Hallucigeniidae, however this has been questioned by later studiesHelenodoraPanarthropodaIndeterminate Lobopodia H. inopinataControversial animal that may be an onychophoran (velvet worm), was previously considered (albeit controversially) a synonym of the contemporary IlyodesIlyodesPanarthropodaIncertae sedis I. divisa I. elongataOriginally named as a myriapod in 1890. However, it may represent a nomen dubium, due to neither species being properly diagnosedPalaeocampaPanarthropodaAysheaiidae P. anthraxFirst known freshwater and toxic lobopodian, and the youngest known aysheaiid. Bears spines unlike any other known animal

Artiopoda

Paleofauna of the Mazon Creek fossil beds

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