# Orsten

The Orsten fauna are fossilized organisms preserved in the Orsten lagerstätte of Cambrian (Late Miaolingian to Furongian) rocks, notably at Kinnekulle and on the island of Öland, all in Sweden.
The initial site, discovered in 1975 by Klaus Müller and his assistants, exceptionally preserves soft-bodied organisms, and their larvae, who are preserved uncompacted in three dimensions. The fossils are phosphatized and silicified, thus the delicate chitinous cuticle and soft parts are not affected by acids, which act upon the limestone nodules within which the fossils have survived. Acids dissolve the limestone, revealing the microfossils in a recovery process called "acid etching". To recover the fossils, more than one and a half tons of Orsten limestone have been dissolved in acid, originally in a specifically designed laboratory in Bonn, more recently moved to Ulm. The insoluble residue is scanned by electron microscope. The phosphorus used to replace the fossils with calcium phosphate is presumed to be derived from fecal pellets.
The Orsten fauna has improved the understanding of metazoan phylogeny and evolution, particularly among the arthropods, thanks in part to unique preservation of larval stages. The Orsten sites reveals the oldest well-documented benthic meiofauna in the fossil record. For the first time, fossils of tardigrades ("water bears") and apparently free-living pentastomids have been found.
The Cambrian strata consist of alum shales with limestone nodules (the Alum Shale Formation), which are interpreted as the products of an oxygen-depleted ("dysoxic") marine bottom water habitat of a possibly offshore seashelf at depths of perhaps 50–100 m. The bottom was rich in organic detritus, forming a soft muddy zone with floc in its surface layer.
Other Orsten-type preservation fauna have been found in Nevada, eastern Canada, England, Poland, Siberia, China and the Northern Territory of Australia.

## Paleobiota

Based on data from C.O.R.E. website and subsequent studies.
Animals :
| Genus | Notes |
| Agnostus | An agnostid |
| Cambropycnogon | A larval sea spider |
| Cambropachycope | A monocular arthropod of uncertain affinities, possibly placed in stem-Mandibulata |
| Goticaris | A monocular arthropod of uncertain affinities, possibly placed in stem-Mandibulata |
| Rehbachiella | A pancrustacean |
| Martinssonia | A pancrustacean |
| Dala | A pancrustacean |
| Musacaris | A pancrustacean |
| Bredocaris | A pancrustacean |
| Paulinecaris | A pancrustacean |
| Skara | A pancrustacean |
| Sandtorpia | A pancrustacean |
| Henningsmoenicaris | A pancrustacean |
| Walossekia | A pancrustacean |
| Aengapentastomum | A pentastomid parasitic crustacean |
| Boeckelericambria | A pentastomid parasitic crustacean |
| Heymonsicambria | A pentastomid parasitic crustacean |
| Haffnericambria | A pentastomid parasitic crustacean |
| Oelandocaris | A stem-group crustacean or stem-group mandibulate or megacheiran |
| Hesslandona | A bivalved arthropod belonging to Phosphatocopina |
| Trapezilites | A bivalved arthropod belonging to Phosphatocopina |
| Waldoria | A bivalved arthropod belonging to Phosphatocopina |
| Veldotron | A bivalved arthropod belonging to Phosphatocopina |
| Falites | A bivalved arthropod belonging to Phosphatocopina |
| Vestrogothia | A bivalved arthropod belonging to Phosphatocopina |
| Orstenotubulus | A lobopodian |
| Arthropoda indet. | Several nauplius-like larvae that cannot be associated with any of the other arthropods. The various larvae have been termed A1, A2, B and C. Formerly included among them was “larva D”, now Cambropycnogon. |

### Orsten-type fauna found elsewhere

Animals :
| Genus | Notes |
| Skara | Two additional species known from Poland and China |
| Heymonsicambria | One additional species known from Ordovician of Canada |
| Vestrogothia | Two additional species known from China |
| Markuelia | A possible member of Cycloneuralia, known from Australia |
| Shergoldana | A possible member of Cycloneuralia, known from Australia |
| Dietericambria | A pentastomid known from Greenland |
| Orstenoloricus | A loriciferan larva from Australia |
| Austromarrella | A marrellomorph from Australia |
| Cambrocaris | A crustacean, known only from Poland |
| Unnamed tardigrade | Only known from Siberia |
| Wujicaris | A pancrustacean known from China |
| Yicaris | A pancrustacean known from China |
| Dabashanella | A member of Phosphatocopina from China |
| Klausmuelleria | A member of Phosphatocopina from England |