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Geology F795 > Bivalves > Flashcards

Flashcards in Bivalves Deck (14):

Phylum and class



Time period:

Cambrian to present


Describe morphology

Calcareous valves m, equal size, plane of symmetry along hinge line, left or right valve depending on in one direction, sits above hinge line, where valves are joined. Hinge of Cardinal teeth and sockets, joined by ligament covering hinge plate. Some valves close completely, some gape if siphon extends


What is the palliative line?

Marks the limit of attachment to the shell, palliative sinus indentation if siphon present


How do the valves close?

Adductor muscles contact to keep closed, when muscles relaxes, external ligament pulls valves open. Some may have one central muscle, monomyarian


What is the mode of life?

Evolved to fill many niches, can be bentgonic vagrant, sessile, free lying or attached, or can be burrowers. Can be found in high to low energy environments, fresh or brackish water.


How to bivalves feed?

Feed using siphons, extend from shell, inhale the and exhale by, bring in water, filter feeders, particles removed from water by gills. Burrowing have long siphons


How can bivalves move on the sediment?

Vagrant, muscular foot.


How has mytilus adapted to its environment?

Byssus present, shell covered in periostracum
Sting shell, streamlined and unornamented, large adductor muscles to keep closed in high energy


How are Ostrea type bivalves adapted?

Type of oyster, cement secreted to attach to dw floor, sting thick shell and adductor muscles, inequivalve, to form lid, one shell irregular growth with seabed.


How are graphaea type bivalves adapted?

Extinct oyster, large and convex left valve for resting area so does t sink, small right valve forms lid, sting thick shell, curved to keep above sediment


How are cytherea type bivalves adapted?

Shallow burrowers
Ribs and growth lined to grip sediment, small Palouse sinus and no gape so can close, unornamented streamlined shells so can move through sediment, large adductor muscles, can completely close valves for protection


How are solen type bivalves adapted?

Deep burrowers, large pallial sinus indicates long siphon, unornamented and streamlined, small adductor muscles, anterior and posterior gape


How are pecten bivalves adapted?

Ribbed, thin valves so sting but light, one valve curbed the other flattened to give hydrofoil effect, wars extend hinge line to direct currents, monomyarian adductor muscles to open close valves, tiny eyes on edge of mantle