Scleractinian and Rugose corallites shown with permission from the U. California Museum of Paleontology

 
Invertebrate Paleontology Lab  #3
Cnidaria
Click on the lab title to see the University of California Museum of Paleontology web page

Read BEFORE Coming to Lab:  Benton & Harper, chapter 11
and see this web link on coral paleoclimatology


Note:  Highlighted words are links to the UCMP webpages on that subject. (To go directly to the UCMP home page click here.)

Introduction

    This week we will be examining fossil record of corals, or Anthozoa, a large class of organisms in the Phylum Cnidaria.  We will also be looking at an extinct,  problematic group currently linked to the Cnidaria, the Conulariida (Middle Ordovician-Triassic).  The Anthozoa are currently classified into three Subclasses, of which one Subclass, the Zoantharia (stony corals and sea anemones) is common as fossils in the geologic record.   The three Orders of the Subclass Zoantharia we will be examining are the Tabulata (tabulate corals) which range from Early Ordovician - Permian), the Rugosa (tetracorals, which range from Middle Ordovician to Permian) and the Scleractinia (hexacorals, which range from Middle Triassic to Recent).   The early fossil record of Anthozoa reaches into the Vendian (latest Precambrian time) as soft-bodied imprints, but the record of reef building corals begins in Ordovician time.  An interesting feature of the coral fossil record is that we can see how the reef biome has persisted through Phanerozoic time, with a few important gaps .  Different groups of organisms have built those reefs (remember the Archaeocyathids and Stromatoporoids we studied in Lab #2) but the biome persists.
 
 
 
 
 
 
 
 

  Phylum Cnidaria, Class Anthozoa (Cambrian-Recent) (see video, approximately 10 minutes, on biology of Cnidaria)
Basic Facts & Terms to Know about Cnidaria:  They are:
1. Eukaryotes 
2.   Metazoans with true tissues, nervous, muscular, and reproductive systems (no organs)
3.   Specialized cells
4.   Radial in symmetry (Rugosa: 4-fold aka Tetracorals, Scleractinians: 6-fold  aka Hexacorals)
5.   free-swimming in larval stage (planula larvae):  sessile (attached)as adults
6.   Reproduce sexually and asexually (by budding)
7.   structurally supported by calcium carbonate (aragonite) exoskeleton called the corrallum 
8.   Marine environments,   Sessile (Attached)or Encrusting and can be Reef Builders or Solitary.
9.   Most reef builders require symbiotic zooxanthellae (dinoflagellate algae)  partners, which photosynthesize and therefore need shallow water (Consider-why is this?).  Many solitary corals live in deeper water, and do not have symbiotic algae.

What ecological factors can you expect to be important to their survival?  Consider the problems of substrate type, respiration, feeding, and avoiding predation.

Part I.  Group Assignment:  Corals and Paleoclimate Records  20 pts.
We will examine oxygen isotope data from coral records around the world and see how corals can be used to track changes in sea surface temperature, including El Niño events, over century scale time frames.  This is just one application of corals in geological science.
 

Part II.  Individual Assignment:  Draw and Label 4 Specimens of Cnidaria 20 pts.
Label the corallum, the corallite, the epitheca,  the tabulae, and the septa, as well as the Order, Genus, and time range for the specimen
 
Part III.  Five Minute Paper (If Time Permits).  Write a short 1 - 2 sentence answer to a proposed question 5 points


Consider the Following Questions as You Examine Each of the Fossil Corals  in Lab:
1.  How can you know that this is a fossil coral (consider symmetry, exoskeleton structure)?

2.  Can you see any useful details with your handlens?

3.  With what kind of marine environment do you think this fossil associated?
 

Phylum Cnidaria
Class Anthozoa
Subclass Zoantharia
Order  Tabulata  Geologic Range Lower Ordovician-Permian
Tabulate coral shown with permission from the U. California Museum of Paleontology

 

Look for the horizontal tabulae, which support and divide the corallites, the individual vertical tubes.
Each polyp or zooid in the colony was nested in its own corallite.
 

Be sure to see the Syringopora specimen from the Mississippian age Pahasapa Formation, a common sight for Black Hills field camp students!
Also, be sure to look at Favosites (the "honeycomb coral") , an important Silurian-Devonian reef builder
and at Halysites (the "chain coral"), a common Silurian reef builder

Phylum Cnidaria
Class Anthozoa
Subclass Zoantharia
Order Rugosa Geologic Range Middle Ordovician - Permian

Solitary Rugose horn corals shown with permission from the U. California Museum of Paleontology


Be sure to examine both the solitary rugose horn corals AND the colonial rugose corals.  Can you tell the difference between a Rugose and Scleractinian Colonial Coral?
 

Rugose Corals vs. Scleractinian Corals:  Differences in the Arrangement of the Septa


shown with permission from the U. California Museum of Paleontology
 
 

Phylum Cnidaria
Class Anthozoa
Subclass Zoantharia
Order Scleractinia  Geologic Range Middle Triassic - Recent

NOAA Photo Library Image ID: reef2564, The Coral Kingdom Collection
                       Photographer: Florida Keys National Marine Sanctuary Staff
                       Credit: Florida Keys National Marine Sanctuary
 

NOAA Photo Library Image ID: reef2502, The Coral Kingdom Collection  Location: Florida   Photo Date: 1851Field Studies  Figures 1 and 2, Oculina robusta Pourtales. Figures 3 and 4, Oculina varicosa Leseuer. Figures 5-7, Astrocoenia pectinata Pourtales. In: "Report on the Florida Reefs", 1880, by Louis Agassiz. Memoirs of the Museum of Comparative Zoology at Harvard College, Vol. VII, No. 1. Plate II. These plates help document the oldest studies of the Florida Reefs.


For More Information...
Want to Find Great Images of Corals and Coral Reefs?
Check out the NOAA photo library at www.photolib.noaa.gov/reef

Interested in what can be done with fossilized corals?  Want to know more?
Here are some recent papers (published on-line) on the subject...
 

Chen, Chaolun Allen; Wallace, Carden C.; Wolstenholme, Jackie, 2002.   Analysis of the mitochondrial 12S rRNA gene supports a two-clade hypothesis of the
 evolutionary history of scleractinian corals.   Molecular Phylogenetics and Evolution Volume: 23, Issue: 2, May 2002. pp. 137 - 149.

Chen, Jun-Yuan; Oliveri, Paola; Gao, Feng; Dornbos, Stephen Q.; Li, Chia-Wei; Bottjer, David J., 2002.  Precambrian Animal Life: Probable Developmental and Adult Cnidarian Forms from Southwest China.   Developmental Biology Volume: 248, Issue: 1, August 1, 2002. pp. 182-196.

Feist, Raimund; Ivanov, Kirill S.; Sapelnikov, Vadim P.; Ancigin, Nicolay Y.Y.; Ivanov, Sviatoslav N., 1997.  Correlations between the evolution of benthic faunal communities and convergent  movements of lithospheric blocks from the Silurian to the Late Devonian in the mid-Palaeozoic Uralian basin.   Tectonophysics Volume: 276, Issue: 1-4, July 30, 1997. pp. 301-311.

Klein, R.; Tudhope, A.W.; Chilcott, C.P.; Pätzold, J.; Abdulkarim, Z.; Fine, M.; Fallick, A.E., 1997.  Evaluating southern Red Sea corals as a proxy record for the Asian monsoon.  Earth and Planetary Science Letters Volume: 148, Issue: 1-2, April, 1997. pp. 381-394.

Stanley, Jr., George, D., 2003.  The evolution of modern corals and their early history, Earth-Science Reviews Volume: 60, Issue: 3-4. pp. 195-225.