Brachiopods• Exclusively marine• Live in environments ranging

from subtidal to the abyss • Brachiopods swim only during

larval stage • Widespread distribution

reflects free-swimming larval stage

• Brachiopods occur throughout the world in both cool and temperate waters (Japan, S. Australia, and New Zealand).

• Most brachiopods found in the neritic zone (waters over the continental shelf), a few are found depths of 5000 m

http://www.humboldt.edu/~natmus/lifeThroughTime/Ordovician.web/52.jpg

Brachiopod

• Brachiopods (brachio=arm; pod = foot)

• valves are opened and closed by contracting muscles called adductor and diductor muscles.

Mode of Life

• Brach sessile and marine• Attached to seafloor by pedicle

at posterior• Inarticulate brachs live in tube• Adult brachiopods are filter

feeders • Filter food particles from water • Food passes from mouth to

the esophagus to stomach • Animals feeding on

brachiopods include starfish, crustaceans, gastropods, and fish.

Brachipod Classes

• Brachiopods are separated into two classes: Articulata and Inarticulata.

• Articulate brachiopods have calcareous hinged valves

• Inarticulate brachiopods have valves held together by muscles and most composed chitin and calcium phosphate.

• Very few inarticulate brachiopods are calcareous

Brachiopod Structure

• Secrete shell composed of two valves (shells)

• Valves are not equivalve (mirror images of each other)

• Valves equilateral (if you split the valves down the middle length-wise, mirror images of each other).

• Consequently, brachiopods (brachio=arm; pod = foot) are bilaterally symmetrical and consist of bivalved shells.

• Brachiopods are not clams. Brachiopods distinguished from pelecypods (clams) by inequal valves and by bilateral symmetry.

• In mollusks such as clams, the plane of symmetry passes between the valves so that each valve is a mirror image of each other.

• Modified from Clarkson (1986)

clam

• Most brachiopods range between 20 and 70 mm, some are up to 370 mm.

• Resemble clams, but clams not attached

Brachiopod Valves

Muriel Gottrop

Brachipod Symmetry

•

Geologic History

• Brachiopods first show up in the early Cambrian• reached a maximum in Silurian and Devonian. • Thereafter, declined and only a few brachiopods made it into the Mesozoic. • Brachiopods not abundant in the Tertiary, and they are not common today. • Inarticulate brachiopods not common after Cambrian, but more common in Cambrian than articulates. • Articulate brachiopods especially common in Ordovician and decline in Carboniferous Permian.

ucmp.berkeley.edu

palaeo.gly.bris.ac.uk

• Phylum Brachiopoda (Cambrian-Recent)• Class Inarticulata (Cambrian-Recent)• Class Articulata (Cambrian-Recent)

– Order Orthida (Cambrian-Permian)– Order Strophomenida (Ordovician-Jurassic)– Order Pentamerida (Cambrian-Devonian)– Order Rhynchonellida (Ordovician-Recent)– Order Spiriferida (Ordovician-Jurassic)– Order Terebratulida (Devonian-Recent)

• This animals are sessile and marine and they secrete a shell composed of two valves (shells) that are not equivalve (mirror images of each other) but which are equilateral (if you split the valves down the middle length-wise, they would be mirror images of each other). Consequently, brachiopods (brachio=arm; pod = foot) are bilaterally symmetrical and consist of bivalved shells. Do not confuse brachiopods for clams. Brachiopods are distinguished from pelecypods (clams) by their inequal valves and by their bilateral symmetry. In mollusks such as clams, the plane of symmetry passes between the valves so that each valve is a mirror image of each other.

• Brachiopod valves are calcareous (composed of carbonate material) or chitinous. The brachiopod is attached to the seafloor by the pedicle at the posterior end (refer to figures). Brachiopods are not especially abundant today.

• Brachiopods are exclusively marine, living in environments ranging from subtidal to the abyss. They live mostly in shallow sea bottoms. Brachiopods swim only during the larval stage. Otherwise, they remain in a fixed position, and they are anchored by a stem-like attachment called a pedicle. Brachiopods are classified as sessile benthos. Their widespread distribution reflects the free-swimming larval stage. Unlike brachiopods, some clams can move around. Brachiopods occur throughout the world in both cool and temperate waters (Japan, S. Australia, and New Zealand). Most brachiopods are found in the neritic zone (waters over the continental shelf), a few are found to depths of 5000 m. Most brachiopods range between 20 and 70 mm, some are up to 370 mm.

• Adult brachiopods are filter feeders. They filter food particles from the water. The food particles pass from the mouth to the esophagus to the stomach. Animals that feed on brachiopods include starfish, crustaceans, gastropods, and fish.

• Brachiopods are separated into two classes: Articulata and Inarticulata. Articulate brachiopods are those with valves that are hinged and which are calcareous. Inarticulate brachiopods have valves that are held together by muscles and most are composed chitin and calcium phosphate. Very few inarticulate brachiopods are calcareous.. The brachiopods eat small organisms in waters, which they filter through their system. The valves are opened in closed by contracting muscles called adductor and diductor muscles.

• GEOLOGIC HISTORY (SEE FIGURE IN HANDOUT)• Brachiopods first show up in the early Cambrian and their numbers reached a maximum in the Silurian and Devonian. Thereafter, they

declined and only a few brachiopods made it into the Mesozoic. Brachiopods are not abundant in the Tertiary, and they are not common today. Inarticulate brachiopods are not common after the Cambrian, but they are more common in the Cambrian than articulate ones. Articulate brachiopods are especially common in the Ordovician and they decline in the Carboniferous and the Permian.

• Some important articulate brachiopods:• Orthids (order orthida) Cambrian to Permian• Strophomerids (order strophomerida) Ordovician to Jurassic• Pentamerids (order pentamerida) Cambrian to Devonian• Rynchonellids (order rhynchonellida) Ordovician to Holocene• Spiriferids (order spiriferida) Ordovician to Jurassic• Terebratulids (order terebratulida) Devonian to Holocene