Amniote Origins and Characteristics

This set of vocabulary flashcards covers the evolutionary origins of amniotes, early fossil formations, anatomical characteristics such as skin and skull morphology, and the major lineages of reptiles.

Anthracosaur amphibians

The group from which the Amniota is derived, which were already very amniote-like in their general characters.

Gephyrostegus

An anthracosaur amphibian noted for being very amniote-like in its general characters.

Joggins Formation

A location in Nova Scotia containing an ancient swamp forest of mid-Pennsylvanian age, or about $300\,myo$, where the earliest amniote fossils are found.

Hylonomus

The earliest known and one of the most primitive amniotes, characterized by having an anapsid skull.

Carbonodraco

An early amniote fossil found in Ohio.

Pareiasaurs

A group of terrestrial terrestrial species within the parareptiles that represent stem reptiles evolved prior to the derivation of modern groups.

Mesosaurs

A primitive group of aquatic marine reptiles of Permian age with narrow, elongate snouts and long, interlocking teeth.

Parareptiles

Stem reptiles on the branch below the split between archosaurs and lepidosaurs; includes terrestrial forms like the pareiasaurs.

Cleidoic egg

An egg characteristic of Amniota that contains four membrane layers: the Amnion, Chorion, Allantois, and Yolk sac.

Alpha keratin

A type of keratin in reptile skin that is pliable and supple; it is found throughout the skin and is the only kind found in the hinge region.

Beta keratin

A tough and hard type of keratin that is abundant in the scale area of the reptile epidermis.

Stratum germinativum

The lower layers of the epidermis which produce upper skin layers through mitosis.

Outer generation

In Lepidosauria, the distinct layer of epidermal cells that is shed all at once during ecdysis.

Anapsid

A skull morphology found in primitive amniotes like Hylonomus and certain parareptiles.

Diapsid

The skull morphology characteristic of most animals considered to be reptiles, which early on divided into the Lepidosauria and Archosauria lineages.

Lepidosauria

A lineage of diapsids (including lizards and snakes) characterized by a transverse cloacal opening, periodic ecdysis, and autotomy planes in the tail.

Archosauria

A lineage of diapsids (including crocodilians and birds) characterized by a longitudinally oriented cloacal opening, continuous ecdysis, and a lack of autotomy planes.