Yohoia on:
[Wikipedia]
[Google]
[Amazon]
''Yohoia'' is an extinct genus of megacheiran arthropod from the
Fossil specimens of ''Yohoia'' range in size from 7 to 23 mm, they have a head shield which is followed by 13 trunk tergites, or plates. On both sides, the bottom side of the first 10 of these ended in backward-pointing, triangular points or projections. The last three plates were complete tubes, circling the entire trunk. At the end of the trunk was a paddle-like tail. There were also a pair of large extensions at the front of the head shield. They had a pronounced "elbow" and ended in four long spines, looking rather like fingers. There were three appendages on the bottom of the head shield on each side, and these are assumed to have supported the creature on the sandy or silty sea bottom. There were also single appendages hanging down under the body plates which were flap-like and fringed with setae, probably used for swimming and respiration. Specimens also show some bulbous formations at the front of the head shield that may have served as eyes.
"Yohoia tenuis"
Burgess Shale Fossil Gallery. Virtual Museum of Canada. 2011. (Burgess Shale species 135) {{Taxonbar, from=Q135578 Burgess Shale fossils Megacheira Prehistoric arthropod genera Burgess Shale animals Taxa named by Charles Doolittle Walcott Cambrian arthropods Cambrian genus extinctions Fossil taxa described in 1912
Cambrian
The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...
period that has been found as fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
s in the Burgess Shale
The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At old (middle Cambrian), it is one of the earliest fos ...
formation of British Columbia
British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...
, Canada. The type species, ''Yohoia tenuis'', was described in 1912 by Walcott, who considered it an anostracan crustacean. 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.
Description
Fossil specimens of ''Yohoia'' range in size from 7 to 23 mm, they have a head shield which is followed by 13 trunk tergites, or plates. On both sides, the bottom side of the first 10 of these ended in backward-pointing, triangular points or projections. The last three plates were complete tubes, circling the entire trunk. At the end of the trunk was a paddle-like tail. There were also a pair of large extensions at the front of the head shield. They had a pronounced "elbow" and ended in four long spines, looking rather like fingers. There were three appendages on the bottom of the head shield on each side, and these are assumed to have supported the creature on the sandy or silty sea bottom. There were also single appendages hanging down under the body plates which were flap-like and fringed with setae, probably used for swimming and respiration. Specimens also show some bulbous formations at the front of the head shield that may have served as eyes.
Classification
''Yohoia'' is one of the " great appendage" arthropods. All taxa have a single pair of large pre-oral jointed limbs with branched spiny ends for grasping, impaling, or filtering food items. "Great appendage" arthropods have been seen as apolyphyletic
A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...
group where the appendage has independently evolved, or as a class Megacheira including ''Yohoia'' (with ''Leanchoilia
''Leanchoilia'' is a megacheiran marine arthropod known from Cambrian deposits of the Burgess Shale in Canada and the Chengjiang biota of China.
Description
''L. superlata'' was about long and had long, whip-like flagellae extending from i ...
'', '' Alalcomenaeus'', '' Oestokerkus'', '' Fortiforceps'', '' Jianfengia'', '' Yawunik'') defined as euarthropods, plus the radiodonts, defined as a sister group to arthropods. ''Yohoia-''like genera are small and have biramous limbs with a walking segment, while radiodonts are larger animals without limbs except for the great appendage. (Although biramous limbs have been described in the Devonian radiodont '' Schinderhannes'', this interpretation is highly questioned and it is more likely to be bands of gill lamellae instead.)
Ecology
''Yohoia'' is assumed to have been a mainly benthic (bottom-dwelling) creature that swam just above the muddy ocean floor, using its appendages to scavenge or capture prey.See also
* Paleobiota of the Burgess ShaleReferences
External links
"Yohoia tenuis"
Burgess Shale Fossil Gallery. Virtual Museum of Canada. 2011. (Burgess Shale species 135) {{Taxonbar, from=Q135578 Burgess Shale fossils Megacheira Prehistoric arthropod genera Burgess Shale animals Taxa named by Charles Doolittle Walcott Cambrian arthropods Cambrian genus extinctions Fossil taxa described in 1912