Brachiopods
Some of history's most gorgeous shells.
As a young boy I was blessed with a family who owned limestone quarries and a father who was a paleontologist.
So, when we visited our grandparents, we visited the quarry close in to Moline, Illinois, and it was there I first fell in love with lamp-shells, or rather Brachiopods, as I roamed about the edges of the walls and terraces, amongst boulders and debris.
Figure 1. Thornton Quarry: America’s largest commercial limestone quarry and the second largest limestone quarry in the world.
Brachiopods (brack'-i-oh-pods) are marine animals with two shells (called valves), an upper and lower one.
If you were to look down on the outside top of each shell, you would notice that the right and left halves mirrored each other. You'd also notice how beautiful, and almost wing like, some of the shells can be.
Figure 2. Copyrighted by Rick Schrantz, 1998, 1999, 2000.
However, if you were to look at them sideways, you'd also love their other beautiful differences. Here's a general illustration:
Figure 3. Morphology of a brachiopod shell. Drawn by Muriel Gottrop in May 2005.
Most brachiopods live attached to the sea floor by a flesh stalk that is an extension of the soft internal body. As you can see above, this stalk is called a Pedicle.
Some types of brachiopods lose this stalk when they become adults and either attach themselves directly to the sea floor or lie loose in the mud or sand. Some also have spines that serve as anchors.
Because of where they live, Brachiopods can be called benthic (bottom dwelling) marine (sea or ocean) bivalves (because of their two shells).
History
The earliest brachiopods in the fossil record occur in the early Cambrian, and Brachiopods are extremely common fossils throughout the Paleozoic Era (See the Geologic chart). However, a major shift came about with the Permian extinction.
Before this extinction event, brachiopods were more numerous and diverse than bivalve mollusks. Afterwards, in the Mesozoic, their diversity and numbers were drastically reduced, and they were largely replaced by bivalve mollusks.
Mollusks continue to dominate today, and the remaining orders of brachiopods survive largely in fringe environments.
It's All In The Shell
Brachiopod shells are quite different from bivalve shells, and the animals within are very different.
Figure 4.
Brachiopod shells may be made of either Calcium Phosphate or — much more commonly — Calcium Carbonate (CaCO3), as mollusks generally are, and a few of the shells were made up of a horny substance.
Brachiopods are not common in most oceans today, but at times in the past they were the most abundant shellfish and sometimes formed large shell banks, as oysters do.
However, while they may seem similar, they are not like oysters or clams or any other mollusks. They belong to a group of animals called Lophophorata and are related to bryozoans, cousins so to speak which are also filter feeders.
Filter feeders eat microscopic organisms and bits of organic matter.
They gather their food from the water that flows by them, and they do this with a specialized organ called a lophophore – a tube like structure with cilia (hair like projections).
The cilia move food particles down the lophophore to the mouth.
The lophophore takes up about 2/3 of the space inside the shell, with the body of the animal occupying the remaining third.
Here's a cut-away view of a brachiopod:
Figure 5. The lophophore is supported by the brachium and sweeps food particles into the mouth.
Because brachiopods are still living today, they are considered “living fossils.
Here's a photo of a living brachiopods.
Figure 6. Smooth-shelled Liothyrella Neozelanica covered with epibionts. Photographer Franz Smith.
Just The Specs
Taxonomy and Age Range
Phylum Brachiopoda — earliest Cambrian-Recent
– Subphylum Linguliformea (Early Cambrian-Recent)
• Class Lingulata (Early Cambrian-Recent):
• Class Paterinata (Early Cambrian-Late Ordovician)
– Subphylum Craniiformea (Early Cambrian-Recent)
– Subphylum Rhynchonelliformea (Early Cambrian-Recent)
• Class Chileata (Early Cambrian only)
• Class Obolellata (Early-Mid. Cambrian)
• Class Kutorginida (Early-Mid. Cambrian)
• Class Strophomenata (Mid. Cambrian-Triassic)
• Class Rhynchonellata (Early Cambrian-Recent) (Includes the orders: Orthida, Rhynchonellida, Pentamerida, Athyrida, Atrypida, Spiriferida, Spiriferinida, and Terebratulida)
Links
Here's a link to a chinese crushing plant, one similar to the crusher plant at the Collinson Stone Company:
www.crusherinc.com
Here's a great site about Brachiopods:
www.palaeos.com
Here's a site that shows living brachiopods:
www.safossils.com
Definition of Epibiont
An epibiont is an organism that lives on the surface of another living organism. An epibiont is usually considered harmless to the host; in this sense, the relationship between the two organisms can be considered neutralistic or commensalistic.
Typical epibionts are barnacles, remoras, and algae, all of which live on many larger marine organisms, such as whales, sharks, and sea turtles.
en.wikipedia.org
Figures & Acknowledgments
Figures
Figure 1. www.iun.edu
Figure 2. www.uky.edu
Figure 3. commons.wikimedia.org
Figure 4. www.palaeos.com
Figure 5. www.palaeos.com
Figure 6. www.treasuresofthesea.org.nz
Acknowledgments
- Taufiq
- Micropaleontologist/Geologist
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- http://www.brachiopods.co.cc/
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- Rick Schrantz
- Photographer and member of the Kentucky Paleontological Society
http://www.uky.edu/OtherOrgs/KPS/
References
Sokiran, EV (2002), Frasnian–Famennian extinction and recovery of rhynchonellid brachiopods from the East European Platform. Acta Pal. Pol. 47: 339–354.
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