These CSIs provide molecular means to reliably distinguish chordates from all other metazoan. In addition to the morphological characteristics used to define chordates, analysis of genome sequences has identified two conserved signature indels (CSIs) in the proteins cyclophilin-like protein and mitochondrial inner membrane protease ATP23, which are exclusively shared by all vertebrates, tunicates and cephalochordates. Chordates are also bilaterally symmetric, have a coelom, possess a circulatory system, and exhibit metameric segmentation. The name “chordate” comes from the first of these synapomorphies, the notochord, which plays a significant role in chordate structure and movement. These five synapomorphies include a notochord, dorsal hollow nerve cord, endostyle or thyroid, pharyngeal slits, and a post-anal tail. All chordates possess five synapomorphies, or primary characteristics, at some point during their larval or adulthood stages that distinguish them from all other taxa. Example of chordates: Branchiostoma lanceolatum ( Cephalochordata), Polycarpa aurata ( Tunicata), as well as a Tiger shark and a Siberian tiger ( Vertebrata).Ī chordate ( / ˈ k ɔːr d eɪ t/) is an animal of the phylum Chordata ( / k ɔːr ˈ d eɪ t ə/).
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