Pikaia is an extinct animal known from the Middle Cambrian fossil found near Mount Pika in the Burgess Shale of British Columbia. It was discovered by Charles Walcott and was first described by him in 1911. Based on the obvious and regular segmentation of the body, Walcott classified it as a Polychaete worm. It resembles a living chordate commonly known as the lancelet. The Cambrian is a major division of the geologic timescale that begins about 542 million years before the present (BP) at the end of the Proterozoic eon and ended about 490 million years BP with the beginning of the Ordovician period. ... A fossil Ammonite Fossils are the mineralized remains of animals or plants or other traces such as footprints. ... The Burgess shale (named after Mount Burgess, near where the shale was found) is a black shale found high up in the Canadian Rockies in Yoho National Park near the town of Field, British Columbia. ... Motto: Splendor Sine Occasu (Splendour without diminishment) Other Canadian provinces and territories Capital Victoria Largest city Vancouver Lieutenant Governor Iona Campagnolo Premier Gordon Campbell (BC Liberal) Area 944,735 km² (5th) Land 925,186 km² Water 19,549 km² (2. ... Charles Doolittle Walcott (March 31, 1850 _ February 9, 1927) was an eminent American invertebrate paleontologist. ... Orders Amphinomida Capitellida Chaetopterida Cirratulida Cossurida Ctenodrillidae Eunicida Flabelligerida Magelonida Myzostomida Nerillida Opheliida Orbiniida Orweniida Phyllodocida Pisionidae Polygordiida Protodrilida Psammodrilidae Sabellida Spionida Spintheridae Sternaspida Terebellida The Polychaeta or Polychaetes are a class of annelid worms, generally marine, with a pair of fleshy protrusions on each body segment called parapodia that... Families Asymmetronidae Branchiostomidae The lancelets (subphylum Cephalochordata, and traditionally known as the amphioxus) are a group of primitive chordates. ...

During his re-examination of the Burgess Shale fauna in 1979, Paleontologist Conway Morris placed Pikaia gracilens in the chordates, making it perhaps the oldest known ancestor of modern vertebrates. A paleontologist carefully chips rock from a column of dinosaur vertebrae. ... Typical Classes Subphylum Urochordata - Tunicates Ascideiacea Thaliacea Larvacea Subphylum Cephalochordata - Lancelets Subphylum Myxini - Hagfishes Subphylum Vertebrata - Vertebrates Petromyzontida - Lampreys Placodermi (extinct) Chondrichthyes - Cartilaginous fishes Acanthodii (extinct) Actinopterygii - Ray-finned fishes Actinistia - Coelacanths Dipnoi - Lungfishes Amphibia - Amphibians Reptilia - Reptiles Aves - Birds Mammalia - Mammals Chordates (phylum Chordata) include the vertebrates, together with... Typical classes Petromyzontidae (lampreys) Placodermi - extinct Chondrichthyes (cartilaginous fish) Acanthodii - extinct Actinopterygii (ray-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) Amphibia (amphibians) Reptilia (reptiles) Aves (birds) Mammalia (mammals) Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ...

Averaging about 40 mm in length, Pikaia swam above the seafloor using its body and an expanded tail fin. Pikaia may have filtered particles from the water as it swam along. Only 60 specimens have been found to date.