Biology » Vertebrates » Chordates

Introducing Chordates

Introducing Chordates

Vertebrates are members of the kingdom Animalia and the phylum Chordata (see the figure below). Recall that animals that possess bilateral symmetry can be divided into two groups—protostomes and deuterostomes—based on their patterns of embryonic development. The deuterostomes, whose name translates as “second mouth,” consist of two phyla: Chordata and Echinodermata.

Echinoderms are invertebrate marine animals that have pentaradial symmetry and a spiny body covering, a group that includes sea stars, sea urchins, and sea cucumbers. The most conspicuous and familiar members of Chordata are vertebrates, but this phylum also includes two groups of invertebrate chordates.

The deuterostome phylogenetic tree includes Echinodermata and chordata. Chordates possess an notochord and include chephalochordates (lancelets), urochordata (tunicates) craniata, which have a cranium. Craniata includes the Myxini (hagfish) and vertebrata, which possess a vertebral column. Vertebrata includes the Petromyzontida (lampreys) and Gnathostomes, which possess a jaw. Gnathostomes include Actinopterygii (ray finned fishes) and animals with four limbs. Animals with four limbs include Actinistia (coelacanths) , dipnoi (lungfishes) and tetrapods, or animals with four legs. Tetrapods include amphibian (frogs and salamanders) and Amniotic, which possess an amniotic egg. Amniota includes reptilian (turtles, snakes, crocodiles and birds) and mammalia, or animals that produce milk.

All chordates are deuterostomes possessing a notochord.

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