Researchers described the earliest vertebrates known to have jaws based on fossils of four extraordinary fish species discovered in China, two of which date from 436 million years ago and the other two from 439 million years ago.
This undated handout image depicts a life
reconstruction of the spiny shark-like fish Fanjingshania renovate from the
Silurian Period, whose fossils were found in Shiqian county, Guizhou province,
China. About 439 million years ago, the fish was alive. Submitted by Heming
Zhang for REUTERS.
Having jaws is essential to the existence of humans
and 99.8% of our fellow vertebrate species. Try eating a taco without them for
a moment. Jaws did, however, have to begin somewhere, just like everything else
in our bodies.
Researchers described the earliest known jawed
vertebrates on Wednesday based on fossils of four extraordinary fish species
discovered in China, two of which date from 436 million years ago and the other
two from 439 million years ago. Up until recently, the first animals with jaws
had remained a mystery because only ragged fossils of vertebrates from that
crucial point in the evolution of animals with backbones had been discovered.
"Everything changes because of the new
fossils. We now know their size, appearance, and historical evolution”,
according to vertebrate palaeontologist Min Zhu of the Chinese Academy of
Sciences in Beijing, who was the lead author of the study that was published in
the journal Nature.
The newly described species, none of which were
more than a few inches, were found in two fossil troves from the Silurian
Period that were found in southern China. Fish from 425 million years ago is the oldest jawed animals to have been discovered.
"Nearly every vertebrate you are familiar with that
has a backbone, such as those you see in zoos and aquariums and even humans,
are jawed vertebrates", according to Zhu. Shortly after creation, the basic body designs of Jawed Vertebrates were determined. For instance, practically
every organ in the human body may be linked back to the first jawed fish. That
is why it is crucial to look back and determine the roots.
Semicircular bony plates covered the majority of
its front. The back half, which had a strong tail, was much more like a regular
fish. It existed 436 million years ago together with its close relative, the
similarly sized shark Shenacanthus vermiformis, whose bones were discovered at
the same location.
Unexpectedly for a shark related, Shenacanthus'
shoulders were covered in massive bone plates. Shenacanthus, in contrast to
contemporary sharks, had a toothless mouth and may have consumed small,
soft-bodied food.
In the neighbouring province of Guizhou, two other
shark relatives, the 4-inch (10-cm) long Qianodus duplicis and the 6-inch
(15-cm) long Fanjingshania renovate, were discovered. They date back three
million years. Although their bones were less complete and well-preserved than
those of the other two species, these are the oldest members of the shark
lineage that are known.
Another evolutionary milestone is the discovery of
Qianodus, the oldest vertebrate known to have teeth. Because Qianodus carried
numerous generations of teeth that were continuously added throughout its life,
they were spiral in shape. Fanjingshania possessed numerous pairs of fin spines
as well as bony exterior armour.
About 520 million years ago, fish first started to
appear. The earliest fish, like contemporary lampreys and hagfish, lacked a
jaw. The greatest marine predators at the time the newly discovered species
lived were sea scorpions, which could grow up to 8 feet (2.5 metres) long. Jaws
contributed to the development of land vertebrates, including fish that would
soon rule the seas and subsequently give rise to amphibians, reptiles, birds,
and mammals, including humans.
One Example of an Evolutionary Invention is Jaws.
"Jaws are significant because they marked the
beginning of vertebrates' active predatory behaviour. The development of jaws,
however, represented just a minor portion of the overall alteration of the
vertebrate body plan at this stage of evolution", according to Per Ahlberg, a
palaeontologist and research co-author from the University of Uppsala in
Sweden.
The growth of the stomach, separation of the head from the shoulder girdle, pelvic fin development, forward movement of the heart away from the liver, and dramatic changes in the inner ear all happened at the same time. This was unquestionably the most dramatic change in the evolutionary history of vertebrates.
Comments
Post a Comment