Arandaspis


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Name: Arandaspis ‭(‬Aranda shield‭ ‬-‭ ‬after the Aboriginal Aranda tribe who live near where the first discoveries were made‭)‬.
Phonetic: Ah-rand-as-pis.
Named By: A.‭ ‬Ritchie‭ & ‬J.‭ ‬Gilbert-Tomlinson‭ ‬-‭ ‬1977.
Classification: Chordata,‭ ‬Pteraspida,‭ ‬Arandaspida.
Species: A.‭ ‬prionotolepis‭ (‬type‭)‬.
Diet: Uncertain.
Size: About‭ ‬15‭ ‬centimetres long.
Known locations: Australia,‭ New South Wales - Rowena Formation, Northern Territory - Stairway Sandstone Formation..
Time period: Early/Mid Ordovician.
Fossil representation: Multiple specimens.

       Arandaspis is today one of the better known Ordovician fishes,‭ ‬though its appearance is not what you might expect.‭ ‬The body of Arandaspis was long yet deep,‭ ‬with a single fin extending around the posterior half of the body.‭ ‬As such Arandaspis is not thought to have been a particularly powerful or graceful swimmer,‭ ‬possibly propelling itself through the water with just a series of rapid yet slight laterally undulating‭ (‬side to side‭) ‬body movements.‭ ‬Arandaspis also had two‭ ‘‬shields‭’ ‬made from thin bone,‭ ‬the lower being deeper than the upper.‭ ‬These would have provided support for the body as well as a degree of protection,‭ ‬but there were still gaps so that features such as eyes and gills were not obstructed.
       Arandaspis may have been a predator of other much smaller marine organisms.‭ ‬However the mouth points downwards,‭ ‬suggesting that it may have been a bottom feeder,‭ ‬either scooping up small bottom dwelling organisms or particles of organic matter that had fallen to the sea floor.‭ ‬Although Arandaspis was a jawless fish,‭ ‬it is still believed to have had plates inside the mouth that allowed the lips to have been flexible.‭ ‬To a certain extent this means that Arandaspis would have been able to manipulate things into its mouth.

Further reading
-‭ ‬First Ordovician vertebrates from the Southern Hemisphere,‭ ‬A.‭ ‬Ritchie‭ & ‬J.‭ ‬Gilbert-Tomlinson‭ ‬-‭ ‬1977.



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