New piece in the jigsaw puzzle of human origins

In an article in today's Nature, 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", Martin Brazeau says.

"I present 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."

Source: Uppsala University

   

• mabarker - Jul 14, 2009
  • Rank: 1 / 5 (1)
  This article says in classic evolutionary style, *The study may give important clues to the origin of jawed vertebrates, and thus ultimately our own evolution.*
  
  Give me a break.
  
  Herewith are the facts: the Agnatha (jawless fish) such as the lamprey (Petromyzontida) are quite complex in their design (e.g. well-formed eyes, filter feeding ability) and are genuine fish. Looking to the fossil record for their evolutionary ancestors has revealed nothing. M. Benton (2005) is cautious, saying, *Lampreys and hagfishes are very different from many of the extinct jawless fishes, but they are unique in perhaps showing us something of the Early Paleozoic world, before jaws existed* [emphasis mabarker] p. 44
  
  Three darwinists stated, . . . no forms intermediate between agnathans [vertebrates containing the earliest and most primitive vertebrates] and gnathostomes [jawed vertebrates including the fishes] are known. Hickman, et al. 1997, p. 501
  
  *The evolutionary relationships of gnathostomes [jawed vertebrates] have been the subject of study for almost a century. Fossils, morphological characters, and molecular sequences have been used to infer their phylogenetic relationships. However, these studies have proposed different models of relationships that have not been resolved with confidence. Phylogenetic analysis of mitochondrial and some nuclear gene sequences have generated conflicting models, indicating that molecular sequences may not be adequate for resolving the deep branches of gnathostomes* Venkatesh, Erdmann and Brenner, PNAS 2001.
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• Ethelred - Jul 15, 2009
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  Herewith are the facts: the Agnatha (jawless fish) such as the lamprey (Petromyzontida) are quite complex in their design (e.g. well-formed eyes, filter feeding ability) and are genuine fish.

  
  
  And have undergone another 410 million years of evolution.
  
  

  Looking to the fossil record for their evolutionary ancestors has revealed nothing

  
  
  Sure it has. If it hadn't you wouldn't be mining for quotes to try to make reality go away.
  
  

  Three darwinists stated, . . . no forms intermediate between agnathans [vertebrates containing the earliest and most primitive vertebrates] and gnathostomes [jawed vertebrates including the fishes] are known. Hickman, et al. 1997, p. 501

  
  
  Well that has now changed. So much for searching and quoting but not reading.
  
  You really should the sources of your out of context quotes.
  
  Ethelred
  
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