Crinoids Flashcards
What is their phylum and class
Echinodermata
Crinoidea
What kind of plates do they have
Calcareous
What kind of symmetry do they have
Five-fold symmetry
What are the four main parts of a Crinoid
Holdfast
Stem
Calyx
Brachia
What does the calyx contain most of
The soft parts (soft tissue)
What is the calyx supported on and what is it made of
The stem
Made of plates called ossicles (calcite plates)
What are the calyx arms called
The brachia
What does the brachia do
Gather food particles and pass it to the mouth in the upper surface of the calyx
What kind of groove do the brachia have
V-groove on the upper surface along which the food particles are moved by cillia
What is the holdfast
Act as roots for attachment to substrate
Where is the anal tube
Protruding from the calyx, gets rid of waste material without mixing it with fresh water
What is their mode of life
They are either sessile or nektonic
Found at almost any water depth
Filter feeder
Geological timeline
First appeared in the Ordovician and are alive today
Why are they an important fossil recors
They are abundant in the upper Paleozoic, where bioclastic limestone can be largely composed of fragmented Crinoids
