Does the foot-long fragment come from a mammoth or a mastodon?
"I was immediately excited, it was just perfect, and I knew it was an important find that needed to be shared with people."
The findings could help to shine a light on the evolutionary history of mammals.
The extinct big cat resembled some species you might see in a zoo today, sharing some features with lithe African cheetahs and others with larger, more muscular cats like jaguars and leopards.
Scientists now believe humans stalked and then confronted a giant ground sloth thousands of years ago in New Mexico.
Early dinosaurs were at the mercy of weather patterns unfolding across the supercontinent Pangaea.
"This is a one in 100 million specimen," a University of Kansas fossil expert said.
This is the first time Candelarhynchus padillai has ever been seen in tropical South America.
This makes 11 total Archaeopteryx specimens.
The ancient marine mammal could help explain when North and South America first joined.