Cnidarians Flashcards
How are solitary corallites formed?
polyps which live an individual existence and do not form part of a colony
Where can many solitary corals be found among?
Rugosa and Scleractinia (extinct solitary corals)
How are colonies produced from an individual founding polyp?
asexual reproduction
What is the advantage to coral colonies forming?
capacity for increased size and stability and greater efficiency in feeding and other major life processes
What are the skeletons secreted by colonial corals said to be?
Compound (leading to widely variable morphology)
What are some examples of Cateniforms?
Halysites; Tabulate
What are Canteniforms like?
corallites are joined laterally to form palisades
Would do horizontal section of canteniforms resemble?
links in a chain
What are some examples of Cerioids?
Lonsdaelia; Rugosa
What are Cerioids?
walls of the adjacent corallites are joined to produce a polygonal pattern in cross section
What is an example of a phaceloid?
Syringopora; Tabulata
What are phaceloids?
a type of fasciculate coral in which the cylindrical corallites are approximately parallel with each other
What is an example of Thamnasteroid?
Phillipsastraea; Rugosa
What are Thamnasteroids?
absence of Epithecal so the septa (walls/plates) adjacent corallites join each other
What is the common growth forms of Thamnasteroids?
Scleractinian corals (also in extinct rugose corals)
What do rugose corals show?
degree of bilateral symmetry since the metasepta are only inserted in 4 areas
What can obscure the bilateral symmetry of rugose corals?
the large number of septa
What are the characteristics of most rugosa corals?
Well developed septa
Dessepiments and tabulae
Columella or other axial structure
What is the epitheca (upper of coral) like for rugosa corals?
almost always prominent and generally thick and wrinkled
What were rugosa like between the middle Ordovician and the lower Llandovery?
Most species small and solitary
When did rugosa occur?
Middle Cambrian
(but typical examples not till middle Ordovician)
What took place in the Silurian regarding rogusa?
diversification that meant rugosa became an important element of reef faunas
When did rugosa start to decline?
in the later carboniferous and then persisted till extinction at the end of the Permian
Are Tabulates solitary or colonial?
Colonial
What are the characteristics of Tabulates?
corallites are usually small with prominent tabulae
Septa reduced or absent
What is coenosteum?
skeletal tissue between the corallites secreted by a sheet of tissue that joined the polyps in life
When are Tabulates thought to have occured?
Cambrian but undoubted presence in the lower Ordovician
When were are tabulates extinct?
By the end of the permian
What corals does the Scleractinia order cover?
All post lower Triassic corals
How can Scleractinia be distinguished from Rugosa?
Septal insertion
What is septa insertion like for Scleractinia?
Inserted in multiples of six each insertion cycle must be completed before the next cycle
What is the epitheca like in Scleractinia?
poorly developed or absent
What is the skeletal composition of Scleractinia?
Aragonites (with other corals being low-Mg calcite)
What did Scleractinia evolve from?
A soft bodied organism instead of Rugosa or Tabulate
