∞ generated and posted on 2016.09.01 ∞

Animals characterized first and foremost by the secondary embryonic formation of their mouth versus their anus.

Deuterostome literally means second mouth, that is, a mouth that forms from an embryoís blastopore. See by contrast protostome.

Deuterstome animals additionally possess early cleavage characteristics that are both radial cleavage relative to the embryo and what is known as indeterminate cleavage, meaning that every cellís fate is determined from the outset of development (contrasting cleavage that instead occurs spiral and is determinate). These animalís body cavities (coelom) further form as outgrowths from the archenteron as too does the mesodermal tissue.

Included among the deuterostomes are phylum Echinodermata and phylum Chordata.