Simplify the following text for a Grade 4 native English-speaking person.
Original: The tail , known as the telson , is spiked in most eurypterids like in modern scorpions and in some species it may have been used to inject venom , but so far there is no certain evidence any eurypterids were venomous .
Simplified: The tail , known as the telson , is spiked in most eurypterids .