Facts about Spiny Sharks, an extinct prehistoric animal

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Dinosaur!

 
   
Dinosaur Jungle   >   Other Prehistoric Animals   >   Spiny Sharks

   

Spiny Sharks



Scientific Classification
  Kingdom Animalia
  Phylum Chordata
  Infraphylum Gnathostomata
  Class Acanthodii
Spiny Sharks ("Acanthodians") are a group of extinct fish, and are probably the earliest known jawed vertebrates. Their jaws are believed to have evolved from the gill arches of earlier jawless fishes, some of which used jointed cartilage as a "gill skeleton". Their fossils first appear during the early Silurian period, perhaps around 440 million years ago, and they went extinct during the late Permian period, perhaps around 250 million years ago. They evolved initially as marine species, but later during the Devonian and Carbiniferous periods colonized freshwater environments too - from the Devonian period onwards, freshwater species predominate.

Despite their name, and an outward appearance that somewhat resembled sharks, the Acanthodians were not sharks - rather had features of both bony fish (Osteichthyes) and cartilaginous fish (Chondrichthyes) - for example, they had a cartilaginous skeleton, but their fins had a bony base. Acanthodians are called "spiny", because all their fins, except the tail, were supported by bony spines.

Another interesting feature of Spiny Sharks is that their epidermis was covered with tiny rhomboid-shaped scales - although in some species particular scales are greatly enlarged, covering the top of the head, the shoulder girdle, or providing a bony flap over gill openings. Each order of Acanthodii had their own distinctive arrangement of scales, and as a result it is often possible to determine the relative age of sedimentary rocks by examining Acanthodii fossils and their scales.

Spiny Sharks Timeline:



Spiny Sharks were early jawed fish that lived between 440 and 250 million years ago

Spiny Sharks were early jawed fish that lived between 440 and 250 million years ago


   
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