Yohoia is an extinct genus of fossil megacheiran arthropod from the Cambrian period. The type species, Yohoia tenuis, has been found in the Burgess Shale formation of British Columbia. 711 specimens of Yohoia are known from the Greater Phyllopod bed, where they comprise 1.35% of the community. In 2015, Conway Morris et al. reported another species, Y. utahana, from the Marjum Formation, Utah.

The head possess a pair of large eyes and a pair of great appendages at the front. The great appendages had a pronounced "elbow" and 4 distal segments ended in four long spines, looking rather like fingers. In the case of Y. tenuis, the appendages showing a "slender" and a "stout" morphotypes. Serrated fingers similar to Parapeytoia and Fortiforceps are evident in some specimens as well. There were another 13 pairs of subequal appendages on the bottom of the body, 3 pairs below the head shield and 10 pairs below all but the last 3 trunk segments. Each of these appendages compose of a leg-like endopod and a flap-like exopods fringed with setae.

Classification

thumb|left|Fossils described by Walcott (1912)

The genus and type species was first described in 1912 by Walcott, who considered it an anostracan crustacean. Upon late 1990s, Yohoia is re-classify under Megacheira (great appendage arthropods), a class of extinct arthropod which has controversial phylogenetic position either as stem chelicerates or a distinct lineage basal than both chelicerates and mandibulates. Within megachierans, Yohoia is generally considered to be part of a clade including Haikoucaris and leanchoiliids, collectively known as Cheiromorpha. Some recent studies suggest alternative positions, for example closer to other megacheirans or Yohoia itself represent a distinct lineage.

See also

  • Paleobiota of the Burgess Shale

References

  • "Yohoia tenuis" . Burgess Shale Fossil Gallery. Virtual Museum of Canada. 2011. (Burgess Shale species 135)