Simplify the following text for a Grade 7 native English-speaking person.
Original: Believed to be present at the time of the arrival of the first Portuguese ships during the 16th century , these creatures are claimed to have existed as recently as the late 19th century .
Simplified: It is said that they were there at the time of the arrival of the first Portuguese ships during the 16th century . These creatures are claimed to have existed as recently as the late 19th century .