The Lophophorates Flashcards
lophophorate
posses a lophophore
filter feeders
A lophophore
A feeding organism that surrounds the mouth. A ring of hollow tentacles with cillia that generate a feeding current. The anus is outside of the ring
Brachiopods
Have 2 valves but are not “bivalves”
“Arm foot”
Relatively minor phyla in modern oceans.
Low nutrient habitats
Benthic filter feeders
Nearly all sessile epifaunal
Probably the most common fossil-the dominant paleozoic form
Brachiopod morphology
Shell made up of 2 valves secreted by an underlying mantle.
pedicle
Grows at margin valves
Commisure
Posterior end may or may not have a hinge or pedicle
pedicle
Fleshy extension of the body used to attach brachiopods to rocks.
Symmetry of brachiopods
Valves are not symmetrical to eachother, but ther is bilatteral symmetry in the valves themselves
Internal anatomy of a brachiopod
*Most of the interior shell occupied by mantle cavity- not much to eat
*Lophophore sits in mantle cavity, attached to dorsal valve
Lophophore can be supported by a calcareous structure (brachidium)
*Have muscles for both opening and closing
Brachidium
A calcareous structure in bivalves that supports the lophophore
Composition of a brachiopod shell
- Organophosphatic (calcium phosphate and organic matter)
* Calcite
An inarticulate bivalve
A bivalve that lacks an articulation hinge
astrophic
Not having a well defined hinge line.
strophic
Having an elongated well defined hinge line.
pedicle opening
Aperture or slit from which the pedicle extends.
Interarea
Surface of a valve between the beak and hinge line; typically bears the pedicle opening.
teeth of brachiopods
Knob like protrusions (teeth) on the hinge of the pedicle valve fits into the small depressions (sockets) on the hinge of the brachial valve.
lingula
living brachiopod group. Called a “living fossil”
diductor scars
Mark the attachment sites of valve opening muscles in brachiopods.
Cardinal process
Know at the midline of brachial valvve interior to which the diductor muscles attach.
Rhynochonelliforms
Brachiopods. Articulate with a calcareous shell
Linguliforms
Brachiopods. Organophosphatic. Inarticulate.
Craniiformea
Brachiopods. Calcareous, no hinge (inartiuclate). Cement lower valvue to something. “skull” formed by muscle scars
Articulate
Brachiopods with a hinge
Inarticulate
Brachiopods without a hinge
Fossil Record of brachiopods
Start in Cambrian. Bulge from Ordovician-Permean. End of the Permean the number goes way down a never recovers (95% become extinct)
Ancestry of brachiopods
Unclear
Paleontological issues with brachiopods
+ancestry unclear.
+Why were they hurt by the permo-Triassic extinction?
+Why have they not bounced back?
+How are subphyla,classes and orders related?
Speculations of why brachiopods have never bounced back in modern times?
competition? low speciation rates? Increased productivity in oceans? Durophagy (shell eating)?
Bryozoa
Lophophorates. Living groups. Relation to brachiopods is unknown. Live as a colony. Made of asexually proliferated units call zooids. Budded from 1 single ancestral zooid. Filter feeders. Common and diverse in the oceans. Colonies can be immerse, sometimes >1m.
zooid
<1 mm in size. Body wall can be calcified (zoecium)
zoecium
Calcified body wall of a zooid
Lophophore in bryozoa
Can be extruded and retracted. May have an operculum to cover lophophore opening, or they may have muscles that can contract and shoot out the lophophore.
How many bryozoa live in a community?
Can be millions in a colony
Skeletons of bryozoa
Can be completely organic and flexible, or partly mineralized and still flexible, or completely mineralized and therefore rigid.
Bryozoa first appearance in the fossil record
First appear in the late cambrian.
