''Skania'' is a Cambrian fossil

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

. The type species, ''S. fragillis'', is known from the Burgess Shale of British Columbia, Canada. A second possible species ''"S." sundbergi'' is known from the Kaili Formation of China, but its placement within the genus has been questioned.

Description

Specimens of ''S. fragillis'' range in length from The cordiform dorsal shield/carapace covers the entire body, with its midline having a raised keel. The shield curls around the front to form a doublure, with the posterior edge of the doublure having a pair of lateral spines. A pair of spines is also present on the posterior of the dorsal shield. A hypostome was present on the underside of the head. There are two sets of appendages, the first 5 pairs of appendages are elongate, the first one of which is described as an antenna and has small subquadrate segments/podomeres, while the others have elongate subrectangular segments. These appendages are somewhat curved and extend beyond the shield. In contrast, the trunk appendages are shorter (not extending beyond the shield) and are less curved, and the segments are not preserved. There was a diverticular (digestive) network running through the carapace, along with a central gut tract. Specimens of ''"S." sundbergi'' are on average in length. The midline keel is more strongly pronounced in ''"S." sundbergi.'' The spines present in ''S. fragillis'' are either more weakly developed or absent.

Taxonomy

While previously enigmatic, it is now thought to be a marrellomorph, with both species, regardless of generic placement, belonging to Acercostraca. The resemblance with the

Ediacaran The Ediacaran ( ) is a geological period of the Neoproterozoic geologic era, Era that spans 96 million years from the end of the Cryogenian Period at 635 Million years ago, Mya to the beginning of the Cambrian Period at 538.8 Mya. It is the last ...

organism An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...

'' Parvancorina,'' to which ''Skania'' had previously been suggested to be closely related as part of the proposed clade "Parvancorinomorpha",'''' is superficial and they are probably not related.

References

External links

* Burgess Shale fossils Cambrian arthropods Marrellomorpha Cambrian genus extinctions {{paleo-arthropod-stub