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A chordate ( / ˈkɔːrdeɪt / KOR-dayt) is a deuterostomic animal belonging to the phylum Chordata ( / kɔːrˈdeɪtə / 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.
According to a long-standing theory, the origin of chordates may be found in transformed larvae of sea-squirts ( tunicates ). Adult tunicates are sessile, but their larvae are motile, and have some features found in early vertebrates. The process of paedomorphosis, where juvenile features are retained in the adult, is the proposed mechanism.
Mar 29, 2024 · protochordate. chordate, any member of the phylum Chordata, which includes the vertebrates (subphylum Vertebrata), the most highly evolved animals, as well as two other subphyla—the tunicates (subphylum Tunicata) and cephalochordates (subphylum Cephalochordata). Some classifications also include the phylum Hemichordata with the chordates.
Figure 29.5 Urochordate anatomy. (a) This photograph shows a colony of the tunicate Botrylloides violaceus. (b) The larval stage of the tunicate possesses all of the features characteristic of chordates: a notochord, a dorsal hollow nerve cord, pharyngeal slits, an endostyle, and a post-anal tail. (c) In the adult stage, the notochord, nerve ...
Figure 29.1.4 29.1. 4: The lancelet, like all cephalochordates, has a head. Adult lancelets retain the four key features of chordates: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail. Water from the mouth enters the pharyngeal slits, which filter out food particles. The filtered water then collects in the atrium ...
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. The discoverer, Charles Doolittle Walcott, described it ...
