Is this like one of those kook theories that the Holocaust didn't
happen and Hitler never killed Jews and others? The question is
actually what would be required for anything to constitute evidence
that fish evolved from invertabrates? The conclusions in the article
are so weak that even if the theory is wrong all the author is trying
to do is weaken the best theories we have so far, to make room for
some dogma or some other apish/religious sin of the flesh. The human
zoo.
The first fish to evolve were the Agnathans (Class agnatha) (7). These
jawless fishes are the first vertebrates. These fish have round mouth
parts that could be used for sucking or filter feeding (10). These
rasping, sucking mouths are currently found on modern lampreys and
hagfishes. These fish were often extremely armored in order to help
them protect themselves. One group that evolved before the Silurian
were the Ostracoderms which have been described as "small, blunt-
headed forms...they fed on debris in the mud, bullet shaped swimmers,
and some...with an astonishing array of spines and crests on their
heads." (1). Most of these types of fish are currently extinct with
the exceptions of the lampreys and the hagfish.
From these bottom feeding, jawless fish came the evolution of jawed
fish. Jaws evolved only once (rather than evolving multiple times in
different species through parallel evolution). Jaws evolved from gill
arches which are the bony parts between gill slits. It is thought that
a gill arch in an agnathan became fused to its skull (11). The upper
part of the gill support became the top jaw and the bottom part of the
gill support became the bottom jaw. Embryology points to this and the
arrangement of nerves in shark heads and most simple fishes shows that
jaws are in line with gill arches. While fish had the first bony jaws,
they also have some of the most complicated. While the human head has
only one moving part (the jaw), the head of a fish may have more than
twenty-four bones that may move together in feeding (8). The evolution
of the jaw is incredibly important because it led to fish to be able
to ingest a much wider variety of foods and allowed them to be active
hunters as opposed to passive filter feeder (1). This led to a wide
variety of adaptations in morphology. Fish became more agile to be
better predators, they were able to reduce their armor because they
were less vulnerable, and their muscle density was able to decrease
becuase they no longer led such a sluggish lifestyle (10).
The first jawless fishes include the acnathodians and placoderms. Even
early in their development the jawless fishes showed great diversity.
The acnathodians appeared around four and half million years ago. They
were the first jawed fishes to evolve and they tended to be small,
streamlined, and had huge eyes. Placoderms on the other hand appeared
in the early Silurian and dominated the Devonian. These were some
strange looking fish! As described by Peter Gore, "the Placoderms had
bony armor that covered the head and forepart of the body. In many, a
movable joint between the head and body armor let the head rock back
to open the mouth wide. The primitive jaws had jagged bony edges that
served as teeth. The tail end usually lacked protection"(11). At the
beginning of the Devonian, Placoderms were small, but they soon
increased in size. The Dunkleosteus, a placoderm, grew to be as large
as 35 feet, had well developed jaws, with fang like teeth. The front
of the trunk was heavily armored and the hind part was either bare or
covered with small scales (11). The Dunkleosteus and all the other
large placoderms are extinct, but in the Devonian they dominated both
salt and freshwater.
http://serendip.brynmawr.edu/exchange/node/1904
http://skywalker.cochise.edu/wellerr/students/armored-fish/armored-fish.htm
21.http://www.evolutiondeceit.com/chapter6.php
