On January 3, the Shreveport Aquarium in Louisiana welcomed a swell shark pup into the world under mysterious circumstances: It was born in a tank that housed only two sharks—and both were female. The two swell sharks have been in a female-only habitat at the Shreveport Aquarium for more than three years.

According to the aquarium, the shark egg was first spotted eight months ago. The shark hatched a few weeks ago and the team at the aquarium is working to determine how it was conceived. Once the shark is big enough for a blood draw,