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The smallest of the three groups of tunicates is the Appendicularia. They retain tadpole-like shapes and active swimming all their lives, and were for a long time regarded as larvae of the other two groups. [29] The other two groups, the sea squirts and the salps, metamorphize into adult forms which lose the notochord, nerve cord, and post anal ...
Order Pterocliformes, sandgrouse (this enigmatic group was traditionally treated as a family in any of three different orders: Charadriiformes, Ciconiiformes, and Columbiformes) Order Columbiformes, doves, pigeons and dodos; Order Psittaciformes, parrots and allies; Order Cuculiformes, cuckoos; Order Strigiformes, owls
The calcichordate hypothesis, formulated by British Museum paleontologist Richard Jefferies, holds that each separate lineage of chordate (Cephalochordates, Urochordates, Craniates) evolved from its own lineage of mitrate, and thus the echinoderms and the chordates are sister groups, with the hemichordates as an out-group. [1]
All chordates, such as vertebrates, eel-like lancelets, and tunicates, or sea squirts, at some point in their lives have a flexible, rod-shaped nerve structure called a notochord in their backs. A ...
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.
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Chordate genomics is the study of the evolution of the chordate clade based on a comparison of the genomes of several species within the clade. The field depends on whole genome data (the entire DNA sequence) of organisms.
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