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Placoderms
| Scientific Classification |
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Infraphylum |
Gnathostomata |
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Placoderms are a group of extinct armored fish. They are noted for
their heavily armored head and thorax, which are covered with armor
plates (whereas the rest of the body either has scales or is unarmored
depending on the particular species). Additionally, Placoderms
are noteworthy for using sharp bony plates as teeth
(recent research suggests that Placoderms may have evolved
their jaws independently from other jawed vertebrates).
The earliest known fossils
date from the mid-Silurian period of the Paleozoic Era
(about 430 million years ago) and are found in
China.
During this time, Placoderms are not believed to have been uncommon,
although fossils
from rocks of this age seem to be relatively rare - paleontologists
attribute this to Placoderms living in environments where
fossilization
was unlikely.
During the following Devonian period (beginning about 408 million years
ago), a diverse array of Placoderms are known to have lived, in both freshwater
and saltwater environments.
Placoderms however under went a rapid decline
during and after the late Devonian mass extinction (about 364 million years ago),
and were completely extinct by the end of the Devonian period (about 360 million
years ago).
The first scientific descriptions and studies of Placoderms were published by
Louis Agassiz in the first half of the 19th century. Since that time,
a variety of theories about Placoderms classification have been proposed
(in the past, they have been at times described as related to jawless fish, related to
cartilaginous fish such as sharks, and even as shelled invertebrates),
however today, they are usually classified to fall within the
Gnathostomata
(the group of animals that includes all jawed fish and other vertebrates),
but to be a sister group of all other known Gnathostomata.
Placoderms were armored fish that lived between 430 and 360 million years ago
Related Information & Resources
See Also
Placoderm Books
Here are some books from Amazon.com:
Disclosure: Products details and descriptions provided by Amazon.com. Our company may receive a payment if you purchase products from them after following a link from this website.
| Placoderms, including: Pterichthyodes, Placodermi, Dunkleosteus, Ctenurella, Arthrodira, Bothriolepis, Groenlandaspis, Coccosteus, Petalichthyida, ... Phyllolepida, Titanichthys |
By Hephaestus Books
Hephaestus Books
Paperback (172 pages)
 | List Price: $21.75*
Lowest New Price: $14.58*
Lowest Used Price: $15.26*
Usually ships in 1 to 3 weeks*
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Click Here | Product Description:
Hephaestus Books represents a new publishing paradigm, allowing disparate content sources to be curated into cohesive, relevant, and informative books. To date, this content has been curated from Wikipedia articles and images under Creative Commons licensing, although as Hephaestus Books continues to increase in scope and dimension, more licensed and public domain content is being added. We believe books such as this represent a new and exciting lexicon in the sharing of human knowledge. This particular book is a collaboration focused on Placoderms.
More info: Placodermi is a class of armoured prehistoric fish, known from fossils, which lived from the late Silurian to the end of the Devonian Period. Their head and thorax were covered by articulated armoured plates and the rest of the body was scaled or naked, depending on the species. Placoderms were among the first jawed fish; their jaws likely evolved from the first of their gill arches. A 380-million-year-old fossil of one species represents the oldest-known example of live birth. |
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By R S. Miles
Royal Soc
Paperback
| Lowest Used Price: $33.43*
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Oliver & Boyd
Paperback
| Lowest Used Price: $50.75*
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Click Here |
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Royal Society of Edinburgh
Paperback
| Lowest Used Price: $36.75*
*(As of 09:41 Pacific 3 Feb 2012 More Info)
Click Here |
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Royal Society of Edinburgh
Paperback
| Lowest Used Price: $36.75*
*(As of 09:41 Pacific 3 Feb 2012 More Info)
Click Here |
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Royal Society
Paperback
| Lowest Used Price: $45.50*
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By R. H. Denison
Cambridge Museum of Comparative Zoology
Paperback
| Lowest Used Price: $10.00*
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Royal Society of Edinburgh
Paperback
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By Roger S Miles
Library Binding
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