''Burgessia'' is a genus of

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...

known from the mid-

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

aged

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 foss ...

of British Columbia, Canada. It is relatively abundant, with over 1,700 specimens having been collected.

Description

The body had an unsegmented approximately circular carapace that was somewhat convex. It was likely thin and had only weak

sclerotization Sclerotization is a biochemical process that produces the rigid shell of sclerotin that comprises an insect's chitinous exoskeleton. It is prominent in the thicker, armored parts of insects and arachnids, especially in the biting mouthparts and scle ...

. A pair of tapering flexible segmented antennae projected forwards from the head, which were about equal in length to the carapace, these were likely

tactile Tactile may refer to: * Tactile, related to the sense of touch * Haptics (disambiguation) * Tactile (device), a text-to-braille translation device See also * Tangibility, in law * Somatosensory system, where sensations are processed * CD96 CD ...

in function. There are three pairs of

cephalic A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals m ...

appendages An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes from an organism's body. In arthropods, an appendage refers to any of the homologous body parts that may extend from a body segment, including anten ...

excluding the antennae that functioned as walking limbs, as well as seven pairs of

biramous The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, plu ...

walking limbs with

gills A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

, otherwise similar to the cephalic limbs running along the trunk, which decreased in size posteriorly. Although not visible on any specimens, the mouth was almost certainly located on the underside of the body. The circular carapace was largely occupied by the guts, which were divided into two sections on either side of the carapace.Hughes, C.P. 1975 07 15
Redescription of Burgessia bella from the Middle Cambrian Burgess Shale, British Columbia
Fossils and Strata, No. 4, pp. 415-43 5, Pls 1- 1 3 , Oslo. ISSN 0300-9491. ISBN 82-00-04963-9 The body ended with a long

telson The telson () is the posterior-most division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment of the arthropod body, or an additional division that is not a true segment on accou ...

, which was moveable and could either be rigid or flexible, which was likely controlled by the injection/withdrawal of fluid from a cavity within the telson and the corresponding increase/decrease of

hydrostatic pressure Fluid statics or hydrostatics is the branch of fluid mechanics that studies the condition of the equilibrium of a floating body and submerged body "fluids at hydrostatic equilibrium and the pressure in a fluid, or exerted by a fluid, on an imme ...

. It was probably used to turn the animal upright if it became overturned.

Ecology

It was likely a

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

sea floor dweller that probably could not swim. It has been suggested to have been a

deposit feeder Detritivores (also known as detrivores, detritophages, detritus feeders, or detritus eaters) are heterotrophs that obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces). There are many kinds of invertebrates, ...

. The first segments and the coxae of the legs had inward, downward facing projections, which in combination with the projections on the opposite pair of legs was likely used to grip food and in combination with other legs bring it forward towards the mouth.

Taxonomy

''Burgessia'' is not placed as part of any major arthropod group, and its relationships to other arthropods are uncertain.

Sources

* ''The Crucible of Creation: The Burgess Shale and the Rise of Animals'' by Simon Conway-Morris * ''Wonderful Life: The Burgess Shale and the Nature of History'' by Stephen Jay Gould

References

External links

*
''Burgessia''
in the

Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database (PBDB) originated in the NCEAS-funded Phanerozoic Marine Pale ...

Prehistoric arthropod genera Burgess Shale fossils Cambrian arthropods Cambrian genus extinctions Taxa named by Charles Doolittle Walcott Fossil taxa described in 1912 {{paleo-arthropod-stub