Shannon pikka model3/27/2023 ![]() ![]() The fossils of Pikaia gracilens was discovered by Charles Walcott from the Burgess shale member of the Stephen formation in British Columbia, and described it in 1911. Popularly but falsely attributed as an ancestor of all vertebrates, or the oldest fish, a close relative of the ancestor of humans, it is generally viewed as a basal chordate alongside other Cambrian chordates it is close relative of vertebrate ancestors but it is not an ancestor itself. Proposed affinities include those of cephalochordata, craniata, or a stem-chordate not closely related to any extant lineage. The exact phylogenetic position is unclear. Its primitive feature is indicated by the body covering, a cuticle, which is characteristic of invertebrates and some protochordates. A notochord and myomeres (segmented blocks of skeletal muscles) span the entire length of the body, and are considered as the defining signatures of chordate characters. The body structure resembles that of the lancelet and perhaps it swam much like an eel. ![]() Since it initial discovery, more than a hundred specimens have been recovered. ![]() It is estimated to have lived during the latter period of the Cambrian explosion. Whittington and Simon Conway Morris as a chordate, it became the "One of the most famous early chordate fossils," or "famously known as relative the earliest" chordates. Described in 1911 by Charles Doolittle Walcott as an annelid, and in 1979 by Harry B. Pikaia gracilens is an extinct, primitive chordate animal known from the Middle Cambrian Burgess Shale of British Columbia. ![]()
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