rayi''
fossil shark, Mazon Creek Lagerstatte. This is the
holotype specimen of the species. Its size and lack of developed
cartilaginous skeletal structures indicate that this is a juvenile. The Mazon Creek fauna has over 320 species of animals that have been identified. The fauna has traditionally been divided into two components: the
marine Essex fauna and the land and purportedly
freshwater Braidwood fauna, that were washed into the deltaic sediments. However, as for many other
Paleozoic fossiliferous localities, the degree of marine influence seems to have been under-estimated, and the latest studies questioned the presence of a truly
freshwater fauna at Mazon Creek and interpreted it instead as deposits from a bay into which some rivers brought some fresh water; no unequivocally freshwater taxon is known there. Thus, the Essex and Braidwood biotas simply represent fossil assemblages preserved far (Essex) or close (Braidwood) to the coast and deltas. Many of the fossils of different plants and animals from the carboniferous that have been found there are on display at the
Illinois State Museum in
Springfield in their changes dynamic Illinois environments exhibit, and at the
Field Museum of Natural History in
Chicago in their evolving planet exhibit.
Essex biota The Essex fauna includes the invertebrates such as a species of
jellyfish called
Anthracomedusa turnbulli, sea
worms (
Nemertea,
Priapulida,
Chaetognatha,
Annelida),
snails, saltwater
scallops, such as
Aviculopecten mazonensis,
crustaceans, such as
Kallidecthes richardsoni,
Belotelson,
Tyrannophontes, and
Cyclidas such as
Americlus americanus, and
Apionicon,
sea scorpions, such as
Adelophthalmus mazonensis,
chaetognaths,
Etacystis communis,
Escumasia roryi,
cephalopods such as
Jeletzkya douglassae and
Pohlsepia mazonensis, two of the three species of
Horseshoe crab found the area known as
Liomesaspis laevi, and the more rare
Paleolimulus mazonensis,
Reticulomedusa grennei, the possible
hemichordate Etacystis, Vertebrate fossils include The
Embolomeri called
Spondylerpeton spinatum which sort of resembled a
Crocodile and was probably the top predator of the area at the time,
temnospondyls such as
Platyrhinops lyelli,
lepospondyls such as
Pseudophlegethontia turnbullorum,
Infernovenator steenae, and
Nagini mazonense, and a
Microsauria called
Diabloroter bolti. Fresh water/brackish water creatures include actinopterygians (
Illiniichthys),
shrimps,
ostracods, and the third species of
horseshoe crab known from the area called
Euproops danae, which was common and probably lived in both saltwater and brackish water. A dubious species of
Acanthodes named
A. beecheri, an unknown species of
Orthacanthus, preserved tetrapod larva fossils,
Mazonova, and
Helenodora inopinata have also been described from the Braidwood fauna. ==See also==