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Origin Of Jawed Vertebrates: Prehistoric Fish Provides New Piece In Evolution's Jigsaw Puzzle

Date:
January 19, 2009
Source:
Uppsala University
Summary:
Scientists describe the skull and jaws of a fish that lived about 410 million years ago. Their study may give important clues to the origin of jawed vertebrates.
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The skull and jaws of a fish that lived about 410 million years ago: Ptomacanthus anglicus.
Credit: Martin Brazeau, Uppsala University

In an article in the journal Nature January 14, Uppsala researcher Martin Brazeau describes the skull and jaws of a fish that lived about 410 million years ago. The study may give important clues to the origin of jawed vertebrates, and thus ultimately our own evolution.

Ptomacanthus anglicus was a very early jawed fish that lived in the Devonian period some 410 million years ago. It represents a type of fossil fish known as an "acanthodian" which is characterized by a somewhat shark-like appearance and sharp spines along the leading edges of all fins (except for the tail fin). This group of early jawed fishes may reveal a great deal about the origin of jawed vertebrates (a story that ultimately includes our own origins). However, their relationships to modern jawed vertebrates (and thus their evolutionary significance) are poorly understood, owing partly to the fact that we know very little about their internal head skeleton.

"To date, we have detailed data from one genus Acanthodes, which occurred very late in acanthodian history," Brazeau explains.

His research presents details on the morphology of the braincase of Ptomacanthus, which is more than 100 million years older than Acanthodes. It is a radically different morphology from Acanthodes, which has several important implications for the relationships of acanthodians. The braincase of Acanthodes appears to most closely resemble that of early bony vertebrates, the lineage that ultimately includes humans and other land-living vertebrates). For this reason, the acanthodians were thought to share a closer ancestor with bony vertebrates than with sharks. However, the braincase of Ptomacanthus more closely resembles that of early shark-like fishes, and shares very few features in common with Acanthodes and the bony vertebrates.

"As a consequence, the results indicate that Ptomacanthus was either a very early relative of sharks, or close to the common ancestry of all modern jawed vertebrates," says Brazeau.


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The above post is reprinted from materials provided by Uppsala University. Note: Materials may be edited for content and length.


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Uppsala University. "Origin Of Jawed Vertebrates: Prehistoric Fish Provides New Piece In Evolution's Jigsaw Puzzle." ScienceDaily. ScienceDaily, 19 January 2009. <www.sciencedaily.com/releases/2009/01/090115103808.htm>.
Uppsala University. (2009, January 19). Origin Of Jawed Vertebrates: Prehistoric Fish Provides New Piece In Evolution's Jigsaw Puzzle. ScienceDaily. Retrieved July 31, 2015 from www.sciencedaily.com/releases/2009/01/090115103808.htm
Uppsala University. "Origin Of Jawed Vertebrates: Prehistoric Fish Provides New Piece In Evolution's Jigsaw Puzzle." ScienceDaily. www.sciencedaily.com/releases/2009/01/090115103808.htm (accessed July 31, 2015).

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