Deuterostomes Key terms

Deuterostomes

A major animal clade defined by the embryological characteristic where the blastopore becomes the anus

Radial Cleavage

A pattern of cell division during embryonic development characteristic of deuterostomes

Echinodermata

A phylum of exclusively marine deuterostomes (e.g., sea stars, sea urchins) characterized by pentaradial symmetry as adults and a calcified endoskeleton

Water-Vascular System

A radially organized system in echinoderms used for movement, feeding, and gas exchange, where water enters through the madreporite

Notochord

A flexible rod present in all chordates at some stage of their life cycle; may be replaced by the vertebral column in vertebrates

Somites

Segmented blocks in which chordate muscles are arranged

Amniotic Egg

A watertight egg structure, possessing membranes like the amnion and chorion, that allowed reptiles, birds, and mammals (Amniotes) to reproduce without the need for a water environment

Craniata

A clade of chordates defined by the presence of a head

Gnathostomes

A clade of vertebrates defined by the presence of a jaw

Ray-finned fishes (Actinopterygii)

The most diverse group of vertebrates, characterized by paired fins supported by bony rays

Endothermy

The ability to generate heat internally to maintain a stable body temperature, a characteristic of Birds (Aves) and Mammals

Dorsal Hollow Nerve Cord

Unique to chordates; develops into the central nervous system (brain and spinal cord).

Pharyngeal Slits

Openings in the pharynx used for filter feeding in non-vertebrate chordates and fish (gills); vestigial in terrestrial vertebrates.

Postanal Tail

A tail that extends posterior to the anus; reduced or vestigial in many adult vertebrates (e.g., humans).

Chordata

Defined by the four hallmarks above. Includes Cephalochordata (Lancelets) and Urochordata (Tunicates).

Vertebrata

Craniates that possess a Vertebral Column (backbone), which encloses and protects the dorsal hollow nerve cord.

Agnathans

Jawless vertebrates. Includes Myxini (Hagfish) and Petromyzontida (Lampreys, which possess rudimentary vertebrae).

Chondrichthyes

Cartilaginous fishes (sharks, rays).

Actinopterygii

Ray-finned fishes (most diverse vertebrate group).

Sarcopterygii

Lobe-finned fishes (fleshy, muscular fins). Includes Actinistia (coelacanths) and Dipnoi (lungfishes).

Tetrapods

Gnathostomes with four limbs. Includes Amphibia and Amniotes.

Amniota

Tetrapods possessing an Amniotic Egg. Includes Reptiles, Birds (Aves), and Mammals.

Mammals (Mammalia)

Defined by hair and mammary glands.

Monotremes

Mammals that lay eggs (e.g., platypus).

Marsupials

Give birth to tiny, underdeveloped young that complete development in an external pouch (e.g., kangaroo).

Eutherians

Placental mammals that retain the young for long-term gestation inside the mother's body.