<Table> <Tr> <Th_colspan="2"> Rattlesnakes </Th> </Tr> <Tr> <Td_colspan="2"> </Td> </Tr> <Tr> <Td_colspan="2"> Eastern diamondback rattlesnake, Crotalus adamanteus </Td> </Tr> <Tr> <Th_colspan="2"> Scientific classification </Th> </Tr> <Tr> <Td> Kingdom: </Td> <Td> Animalia </Td> </Tr> <Tr> <Td> Phylum: </Td> <Td> Chordata </Td> </Tr> <Tr> <Td> Subphylum: </Td> <Td> Vertebrata </Td> </Tr> <Tr> <Td> Class: </Td> <Td> Reptilia </Td> </Tr> <Tr> <Td> Order: </Td> <Td> Squamata </Td> </Tr> <Tr> <Td> Suborder: </Td> <Td> Serpentes </Td> </Tr> <Tr> <Td> Family: </Td> <Td> Viperidae </Td> </Tr> <Tr> <Td> Subfamily: </Td> <Td> Crotalinae </Td> </Tr> <Tr> <Td> Genus: </Td> <Td> Crotalus / Sistrurus </Td> </Tr> </Table> <Tr> <Th_colspan="2"> Rattlesnakes </Th> </Tr> <Tr> <Td_colspan="2"> Eastern diamondback rattlesnake, Crotalus adamanteus </Td> </Tr> <Tr> <Th_colspan="2"> Scientific classification </Th> </Tr>

How many types of rattlesnakes are there in the world