Cnidarians Flashcards
Why should be study fossil corals?
a) Corals are very simple organisms that are voracious predatorsb) corals are excellent indicators of warm, shallow, marine paleoenvironmentsc) some coral taxa were major reef-builders d) coral reefs are (and were) among the diverse ecosystems on Earthe) some coral taxa are important biostratigraphic index fossils, especially rugose & tabulate corals in the Paleozoic
Phylum Cnidaria Three classes:
Class ScyphozoaClass HydrozoaClass Anthozoa
Class Anthozoa Subclasses:
Subclass CeriantipatheriaSubclass OctocoralliaSubclass Zoantharia
Subclass Zoantharia Three Orders:
Order TabulataOrder RugosaOrder Scleractinia
Class Scyphozoa:
true jellyfish; very poor fossil record
Class Hydrozoa:
“fire corals” and their kin; sparse fossil record
Class Anthozoa:
true corals and sea anemones; rich fossil record
Subclass Zoantharia:
6 orders of hard corals + 3 orders of soft sea anemones
Order Tabulata:
(tabulate corals), Early Ordovician to Permian
Order Tabulata Geologic Range:
Early Ordovician to Permian
Order Rugosa:
(horn corals), Middle Ordovician to Permian
Order Rugosa Geologic Range:
Middle Ordovician to Permian
Order Scleractinia:
(modern corals), Middle Triassic to Present
Order Scleractinia Geologic Range:
Middle Triassic to Present
Medusa:
Pelagic, sac-like body form or growth stage (Cnidarians)
Polyp:
Benthic, barrel-like body form or growth stage (Cnidarians)
Radial symmetry:
Multiple vertical symmetry planes radiating outward from the center (Cnidarians)
Basal Disc:
Flattened top portion of the polyp, on which the mouth occurs (Cnidarians).
Oral Disc:
Flattened top portion of the polyp, on which the mouth occurs. (Cnidarians)
Mouth:
The single opening to the central cavity (enteron) (Cnidarians)
Pharynx:
Throat-like tube leading from mouth into the central cavity (enteron). (Cnidarians)
Tentacles:
Arm-like, cnidoblast-bearing structures surrounding the mouth. (Cnidarians)
Enteron:
Central body cavity, which contains mesentery and digestive tissues. (cndarians)
Mesenteries:
Radiating vertical sheets of tissue (Cnidarians)
Cnidoblasts:
“stinging cells”, which contain the poisonous nematocysts (Cnidarians)
Nematocysts:
Toxin-bearing sacs within the cnidoblasts (Cnidarians)
Corallum:
Skeleton of the entire coral colony
Corallite:
Skeleton of a single coral polyp.
Theca:
Outer wall of corallite
Calice:
Bowl-shaped top surface of corallite.
Fossula:
Deep, slot-like indentation in calice.
Columella:
Pillar (axis) in center of corallite.
Septa:
Radiating, vertical, blade-like partitions inside corallite.
Tabulae:
Stacked, horizontal, platform-like partitions inside corallite.
Dissepiments:
Multiple domed plates connecting the septa inside corallite.
Reef:
Biologically produced prominence on the sea floor
Tabulate Corals:
(order tabulata), Early Ordovician to Permian (Syringopora & Favosites are colonial)
Tabulate Corals Geologic Range:
Early Ordovician to Permian
Horn Corals:
Order Rugosa, MIDDLE ORDOVICIAN TO PERMIAN, Heliophyllum & Cystiphyllum are solitary; Pachyphyllum & Hexagonaria are colonial
Horn Corals Geologic Range:
Middle Ordovician to Permian
Modern Corals:
Order Scleractinia, Middle Triassic to Present:(Montastraea & Septastrea are colonial)
Modern Corals Geologic Range:
Middle Triassic to Present
Coral ecology and paleoecology:
Corals are sessile, benthic carnivores that capture, poison, kill and devour tiny worms, crustaceans, etc. They typically are fully marine animals (no fresh water forms).
Hermatypic:
(=reef-building) corals live in warm, shallow, clear, agitated, normal marine water. They house symbiotic algae (zooxanthellae) in their tissues, so they requrei sunlight.
Ahermatypic:
(=non-reef-bulding) corals may live in cold, deep, marine water. They do not have zooxanthellae, so they do not require sunlight in their habitat.
Geologic importance of Tabulate corals:
important reef-builders in Middle Ord. to Dev.
Geologic importance of Rugose corals:
important facies and age indicators through their range.
Geologic importance of Scleractinian corals:
Important reef-builders through their entire range.
Reef formation: DRAW DIAGRAM A-D
Successive stages in the development of modern (scleractinian) coral reefs on subsiding volcanic islands (seamounts), as proposed by Charles Darwin from his observations made while sailing through the South Pacific on the voyage of the H.M.S. Beagle in the 1830’s. A,B, Volcanic island skirted by a fringing reef. C, Volcanic island with a lagoon and barrier reef encircling it. D, Coral atoll with a central lagoon and no vestige of an emergent island above sea level.
