<P> Arachnida (spiders, scorpions and allies) </P> <Tr> <Td> </Td> <Td> <P> Eurypterida (sea scorpions: extinct) </P> </Td> </Tr> <P> Eurypterida (sea scorpions: extinct) </P> <Tr> <Td> </Td> <Td> <P> Xiphosura (horseshoe crabs) </P> </Td> </Tr>

Which type of organism most likely evolved first apex