The Evolution of Jaws in Jawed Vertebrates

These flashcards cover key vocabulary related to the evolution and anatomical structures of jawed vertebrates, specifically focusing on the transition from gill arches to jaws.

Gnathostomata

A monophyletic group that includes all jawed vertebrates.

Gill arch

A structural formation that can evolve into a jaw in gnathostomes.

Olfactory system

The sensory system used for the sense of smell, located on the nasohypophysial plate in non-gnathostomes.

Median adenohypophysis

A structure arising from the development of paired nasal sacs in gnathostomes.

Spiracular pouch

A developmental structure that gives rise to respiratory structures in early jawed vertebrates.

Hyoid arch

An arch that contributes to the muscles and skeleton associated with the hyoid.

Branchial arches

The structures that give rise to the gill arches.

Homeobox (HOX) genes

A group of genes that specify the anterior-posterior axis and body segmentation during development.

Exoskeleton

The external skeletal structure made of dermal tissue in gnathostomes.

Endoskeleton

The internal skeletal structure that first forms as cartilage and can later mineralize into bone.

Placoderms

A paraphyletic group that contains some of the earliest lineages of jawed vertebrates.

Dunkleosteus

The most famous placoderm known for its significant size and bite force.

Ventrolateral fin fold hypothesis

The hypothesis suggesting that paired fins arose from keels extending along the trunk.

Archipterygium hypothesis

The hypothesis proposing that paired fin girdles are derived from ancestral gill arches.

Gnathal plates

Structures found in placoderms that represent early forms of jaw bones.

Acanthodians

An early group of jawed vertebrates believed to be closely related to chondrichthyans.

Chondrichthyes

The class of jawed vertebrates that includes sharks and rays.

Osteichthyes

The class of jawed vertebrates known as bony fishes.

Hyomandibular

The second gill arch that provides support for the jaw bones.

Gill slit

An opening that is retained in some fishes, serving as a spiracle or eustachian tube.

Suction feeding

A feeding technique utilized by gnathostomes to draw in prey through rapid jaw movement.