''Canadia'' (meaning ''of Canada'' or ''after Canada'') is a genus of extinct annelid worm present in Burgess Shale type Konservat-Lagerstätte. It is found in strata dating back to the Delamaran stage of the Middle

Cambrian The Cambrian Period ( ; sometimes symbolized 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 years ag ...

around 505 million years ago, during the time of the Cambrian explosion. It was about in length.

Charles Doolittle Walcott Charles Doolittle Walcott (March 31, 1850February 9, 1927) was an American paleontologist, administrator of the Smithsonian Institution from 1907 to 1927, and director of the United States Geological Survey.Wonderful Life (book) by Stephen Jay G ...

named ''Canadia'' in 1911 after

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...

, the country from which its remains have been found. 28 specimens of ''Canadia'' are known from the Greater

Phyllopod bed The Phyllopod bed, designated by USNM locality number 35k, is the most famous fossil-bearing member of the Burgess Shale fossil '' Lagerstätte''. It was quarried by Charles Walcott from 1911–1917 (and later named Walcott Quarry), and was ...

, where they comprise 0.05% of the community.

Description

With length up to , the animal's most notable feature is the many notosetae (rigid

seta In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. T ...

e extending from dorsal branches of notopodia) along the back of the animal that are characteristic of

polychaete Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are ...

worms. A 1998 paper suggested that it may have been

iridescent Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change color as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, feathers, butterfl ...

due to the supposed presence of

diffraction grating In optics, a diffraction grating is an optical component with a periodic structure that diffracts light into several beams travelling in different directions (i.e., different diffraction angles). The emerging coloration is a form of structural ...

s, however other studies have interpreted these structures as internal

microvilli Microvilli (singular: microvillus) are microscopic cellular membrane protrusions that increase the surface area for diffusion and minimize any increase in volume, and are involved in a wide variety of functions, including absorption, secretion, ...

Tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

s extended from the

prostomium The prostomium (From Ancient Greek, meaning "before the mouth"; plural: prostomia; sometimes also called the "acron") is the cephalized first body segment in an annelid worm's body at the anterior end. It is in front of (but does not include) th ...

and may have served as sensory organs. The gut of ''Canadia'' was straight and had the ability to extend out of the body in the form of a

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elonga ...

, suggesting that the animal was carnivorous. This is further evidenced by the lack of sediments found in the gut that would be present in a benthic

detritivore 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 invertebrate ...

. ''Canadia'' is thought to have swum above the seafloor as a primary means of locomotion by beating its numerous notosetae. It would also have had the ability to creep along the seafloor using the ventral counterpart of the notopodia, which are termed neuropodia (in reference to the proximity to the paired,

ventral nerve cord The ventral nerve cord is a major structure of the invertebrate central nervous system. It is the functional equivalent of the vertebrate spinal cord. The ventral nerve cord coordinates neural signaling from the brain to the body and vice versa, in ...

s characteristic of annelids).

Classification

There has been some debate as to the placement of ''Canadia'' within the Annelida phylum. Although it is commonly accepted to be within Annelida, it is uncertain how it relates to modern annelids. Most paleontologists agree that it belongs to the class Polychaeta due in part to the presence of Parapodium. It has been proposed to be a member of the order

Phyllodocida Phyllodocida is an order of polychaete worms in the subclass Aciculata. These worms are mostly marine, though some are found in brackish water. Most are active benthic creatures, moving over the surface or burrowing in sediments, or living in cr ...

along with ''

Wiwaxia ''Wiwaxia'' is a genus of soft-bodied animals that were covered in carbonaceous scales and spines that protected it from predators. ''Wiwaxia'' fossils – mainly isolated scales, but sometimes complete, articulated fossils – are known from ear ...

'', another organism from the Burgess Shale. Both were placed in a new superfamily called Canadiacea, and were thought to be of closer relationship to each other than to modern annelids.Butterfield, N.J., 1990b. A reassessment of the enigmatic Burgess Shale fossil Wiwaxia corrugata (Matthew) and its relationship to the polychaete Canadia spinosa Walcott. Paleobiology, v.16, no.3, p.287-303 However, ''

'' is no longer believed to have been an annelid and there is currently dispute as to whether or not ''Canadia'' should be classified as belonging to anything more derived than Polychaeta.Eibye-Jacobsen, D. (September 2004). "A reevaluation of Wiwaxia and the polychaetes of the Burgess Shale. Lethaia, v.37, no.3, p. 317-335

References

* Parker, Steve. Dinosaurus: the complete guide to dinosaurs. Firefly Books Inc, 2003. Pg. 37

External links

"Canadia spinosa"
Burgess Shale Fossil Gallery. Virtual Museum of Canada. 2011. (Burgess Shale species 33) {{DEFAULTSORT:Canadia (animal) Burgess Shale animals Cambrian invertebrates Cambrian genus extinctions