Tetrapod-four-limbed vertebrates; the group includes amphibians, reptiles, birds and mammals.
Double circulation-a blood-transport system having a distinct pulmonary circuit of blood vessels separate from the circuit of blood vessels serving the remainder of the body.
Caecilians-limbless burrowing creatures in tropical forests of South America, Africa and Southeast Asia.
Spermatophore-capsule or packet enclosing sperm, produced by males of a few vertebrates.
Direct development-a postnasal ontogeny featuring primarily growth in size rather than a major change in body shape or organs present; a life history that lacks metamorphosis.
Paedomorphosis-displacement of ancestral juvenile features to later stages of the ontogeny of descendants.
Amplexus-the copulatory embrace of frogs and toads.
Spiracle-exhalant aperature of tadpole gill chamber.
Ectothermic-having a variable body temperature derived from heat acquired from the environment.
Axolotl-salamanders of the species Ambystoma mexicanum which do not metamorphose and retain aquatic larval characteristics throughout adulthood.
Ichthyostega-early ancestor with fully formed tetrapod limbs; hindlimb bore seven toes; resembled aquatic forms in retaining a tail complete with fin rays and opercular (gill covering) bones.
Lissamphibia-early ancester which diversified during the Carboniferous to produce ancestors of the three major groups of Amphibians alive today.
Order Apoda or Gymnophiona(without foot)-160 species with elongated body; limbs absent; mesodermal scales present; tail short or absent.95-285 vertebrae. Ex: caecilians.
Order Caudata or Urodela (tail evident)-500 species with body, head, trunk and tail; no scales; usually two pairs of equal limbs; 10 to 60 vertebrae. Ex: salamanders.
Order Anura or Salientia (without tail)-4840 species with head and trunk fused; no tail; no scales; two pairs of limbs; 6-10 vertebrae. Ex: frogs and toads.