Dear Teena,
The horseshoe crab could hold the distinction of being the oldest animal species still in existence.
Dating back to the Paleozoic era, the horseshoe crab existed on Earth before the dinosaurs and soldiered on through several mass extinction events.
In 2008, a horseshoe crab fossil, the oldest in existence found so far, dated back to around 445 million years ago, according to a report by Live Science.