Bivalves (Chapter 13) Flashcards
1
Q
Bivalvia
A
- class of phylym Mollusca
- 2 valves joined at dorsal hinge line (commonly with teeth & ligament)
- lacking head
- well-developed muscular foot
- elaborate gill system
- notably marine but can adapt to brackish & freshwater (Since mid-Paleozoic)
- Lower Cambrian to Recent
2
Q
Bivalvia - soft tissues
A
3
Q
Bivalvia - hard structures
A
4
Q
pallial line
A
- point of attachment of soft tissue to interior of shell
- may be indented posteriorly with extension of siphons
- located ventrally
5
Q
beak
A
- earliest part of shell formed
- usually pointed
- located near hinge line
6
Q
adductor scar
A
impression on interior of shell where adductor muscles (contract to close) were attached
7
Q
hinge plate
A
- shelly internal flatform bearing hinge teeth
- below beak
8
Q
infauna shallow burrower
A
- equivalve
- adductor of equaled size
- commonly has strong external ornaments
9
Q
infauna deep burrower
A
- elongated valve
- often lacking teeth
- permanent gape
- marked pallial sinus
10
Q
epifauna with byssus
A
- elongated valves
- flat ventral surface
- reduction in anterior part of valve + anterior adductor scar
- attached to substrate by thread-like byssus
11
Q
epifauna with cementation
A
- markedly different shaped valves
- sometimes crenulated commisures
- large, single adductor muscle
12
Q
unattached recumbents
A
- includes heteromorphic
- sometimes spines with spines
- ontop soft sediments
- e.g. Cretaceous Exogyra
13
Q
swimmers
A
- different shaped & sized shell
- very large, single adductor muscle
- hinge line extended as ears
- e.g. Miocene Pecten
14
Q
borers & cavity dwellers
A
- elongated cylindrical shell
- strong, sharp ornaments
- cavity dwellers - commonly in dimly lit conditions, follw contour of cavity
