How To Use Heterostracan In A Sentence

• The symmetrical, diphycercal tail, not perfected by gnathostomes until the Cretaceous, was standard equipment on heterostracans in the Silurian.
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• Both the endo- and exoskeleton is made up of true bone with cell spaces (the heterostracans have acellular bone).
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• The Heterostracan head is covered with several armoured plates, the body with large scales and the tail is most often diphycercal.
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