Chapter 9 - Origin of Lissamphibia and Amniota

Temnospondyls

this lineage of tetrapods lead to the formation of modern amphibians

Reptiliomorphs

this lineage of tetrapods lead to the formation of modern amniotes

stem tetrapods

a group of evolutionary rhipidistian ancestors and transitional species more closely related to modern four-legged vertebrates

Caecilians, Salamanders, Frogs, and Amniotes

What are the different synapomorphies of crown tetrapods?

Occipital condyles

Rounded projections on the back of the skull that allow for head movement.

Paired limbs

a derived feature of the tetrapods

ex:

• forelimbs with digits, carpals, radius+ulna, humerus

• hindlimbs with digits, tarsals, tibia+fibula, femur.

mobile neck

a derived feature of the tetrapods. Has a pectoral girdle separated from the skull. In ancestors the pectoral girdle attached directly to the skull.

First cervical vertebra (atlas)

a derived feature of the tetrapods. articulates with occipital condyles, specialized to allow the skull to nod.

Second cervical vertebra (axis)

a derived feature of the tetrapods allows for head rotation

stapes

a hyomandibular bone that was previously used to support the jaw is now used in hearing and conducts sound in the ear

Temnospondyli

Includes Lissamphibia and all tetrapods more closely related to Lissamphibia than to Reptiliomorpha

cleidoic egg

freed the amniotes from the need to reproduce in water that hampered the amphibians ability to spread into harsh environments

shell

a part of the amniotic egg that is leathery/flexible or calcified/rigid, used for mechanical protection, and allows “breathing” through surface

albumin

a part of the amniotic egg that is the “egg white” which is the cushion, and is used for protein and water storage

yolk

a part of the amniotic egg that is the main energy storage for the embryo

amnion

an extraembryonic membrane that develops the embryo

allantois

an extraembryonic membrane that is a storage place for nitrogenous wastes

yolk sac

What does the embryo feed on?

chorion

lies together with the allantois against the shell, and is being richly supplied with blood vessels; exchange gases with the outside through the pores in the shell

monophyletic

Are amphibians monophyletic, paraphyletic, or polyphyletic?

True

True or False: amniotes lack a larval stage and after hatching develop directly into the adult form

traditional classification

recognizes three classes based on clade features
ex:

• Reptilia: reptiles

• Aves: birds

• Mammalia: mammals

Cladistic classification

groups the amniotes on the basis of common ancestry

paraphyletic

Are reptiles monophyletic, paraphyletic, or polyphyletic?

fenestra

openings in the temporal region of the skull

Anapsids

amniotes from the Carboniferous period that have a solid skull with no openings; include turtles and their ancestors

Synapsids

amniotes from the Carboniferous period that have one pair of openings in the skull associated with the attachment of jaw muscles; includes mammals and their ancestors

Diapsids

amniotes from the carboniferous period that have two pairs of openings in the skull roof; includes lizards, snakes, crocodilians, birds, and ancestors

astragalus

an ankle bone shared in amniotes which evolved by fusion of three formerly independent proximal tarsal bones as shown in this basal tetrapod

mesotarsal joint

The original ankle joint of amniotes passed between the astragalus and calcaneus proximally and the smaller distal tarsal bones. This is is suited for limb extension powered by muscles within the limb and marks the change from lateral undulation to limb-based locomotion