This is Mazon Monday post #241. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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Eucryptocaris asherorum is a species of extinct shrimp-like animals from Mazon Creek. They are members on the suborder Tanaidacea, a minor group within the class Malacostraca. Extant members of Tanaidacea are mostly marine, but a few species live in freshwater. They live in the bottom sediments, sometimes in self-built tubes.
E. asherorum was described by Frederick R. Schram in "Designation of a new name and type for the Mazon Creek (Pennsylvanian, Francis Creek Shale) tanaidacean", which was published in the Journal of Paleontology in 1989. It was named for Helen and Charles Asher. You might remember that Helen is the namesake for the Mazon Creek Cnidarian Essexella asherae. In the article's Extract. Schram explains why the holotype (PE 51405) of E. asherorum was originally classified as Cryptocaris hootchi in Scharm's "Paleozoic Peracarida of North America", whcih was published in Fieldiana in 1974.
Extract
When i described the Mazon Creek tanaidacean crustacean and named it Cryptocaris hootchi Schram, 1974, two problems presented themselves. First, all specimens but one were in private collections, and none of their owners then seemed inclined to donate them to an established natural history museum. Second, the collections of the Field Museum of Natural History in Chicago at that time contained only a single specimen, P32053, of what appeared to be the Mazon Creek tanaidacean. This specimen is peculiarly preserved and of only mediocre quality. Consequently, I based the description of the Mazon Creek tanaidacean almost entirely on the privately held specimens, noting their numbers and private repositories, but designated the Field Museum specimen, P32053, as the holotype. A subsequent review of all fossil tanaidaceans (Schram et al., 1986) focused exclusively on the privately held specimens collected from Mazon Creek sites.
E. asherorum is very rare. All known specimens have come from Peabody Coal Company's Pit 11. A brief description and remarks can be found on page 84 of Jack Wittry's "The Mazon Creek Fossil Fauna".
Eucryptocaris asherorum Schram, 1989
Eucryptocaris asherorum has a wide and flattened carapace which covers only the first couple of segments of the tho- rax. The carapace is the widest part of the animal. The body is compressed dorsoventrally. Six thoracic segments are visible and all are decorated with longitudinal ridges along the mid- line. The pleon segments lack ridges, but have well-developed side lobes. The tail has two sets of rounded appendages. The legs are unknown at this time.
E. asherorum is a member of the suborder Tanaidacea, a present-day marine group usually found in freshwater coastal habitats or estuaries. The majority of extant species are bottom-dwellers in shallow water environments, but a few live in very deep water, exceeding for some species 9,000 meters. In some deep sea environments, they represent the most abun- dant and diverse fauna found.
Specimens
Field Museum Specimen PE 51405, the holotype
