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All chordates share a common ancestor which lost its echinoderm stereom calcite skeleton. However, later revisions of the theory had each separate lineage losing its calcitic skeleton independently, [ 6 ] as it evolved from its own mitrate ancestor, making the chordates a paraphyletic group [ citation needed ] .
The Cambrian chordates are an extinct group of animals belonging to the phylum Chordata that lived during the Cambrian, between 538 and 485 million years ago. The first Cambrian chordate known is Pikaia gracilens , a lancelet -like animal from the Burgess Shale in British Columbia , Canada.
A chordate (/ ˈ k ɔːr d eɪ t / KOR-dayt) is a deuterostomal bilaterian animal belonging to the phylum Chordata (/ k ɔːr ˈ d eɪ t ə / kor-DAY-tə).All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics (synapomorphies) that distinguish them from other taxa.
Stylophorans have played a major role in debates over the origin of chordates, as under the calcichordate hypothesis they were interpreted as being stem-group chordates. However, multiple lines of evidence argue against the calcichordate hypothesis, and stylophorans are now widely agreed to belong to the echinoderm total group. Debate remains ...
Download as PDF; Printable version; In other projects ... This category consists all articles on taxa at the subphyla and class levels in the Chordata phylum. ...
The notochord is the defining feature (synapomorphy) of chordates, and was present throughout life in many of the earliest chordates. Although the stomochord of hemichordates was once thought to be homologous or from a common lineal origin, it is now viewed as analogous, convergent , or from a different lineal origin. [ 22 ]
Ambulacraria / ˌ æ m b j uː l ə ˈ k r ɛər i ə /, or Coelomopora / s iː l ə ˈ m ɒ p ə r ə /, is a clade of invertebrate phyla that includes echinoderms and hemichordates; [1] a member of this group is called an ambulacrarian.
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