This 3-foot Caiman alligator was seized by Lawrence animal control after it was listed for sale in an online ad for 00. It’s now staying at the Prairie Park Nature Center.

It was an innocent online ad.

But the offer of $300 for a 3-foot caiman — a reptile similar to a crocodile — including the tank, led to a knock on the door from police.

Marilyn Howard said her adult son Patrick was unaware that it was illegal to keep caimans as pets in the city of Lawrence.

“Animal Control and a police officer came to the house and said it was illegal to have an alligator in the city limits and so they took it,” Howard said.

The family got the reptile from a family friend eight years ago.

Their pet was taken to Prairie Park Nature Center, 2730 Harper St., where officials said it would remain for now.

According to Prairie Park officials, the animal could grow as long as 8 feet and live up to 60 years.

They said the reptile had been docile since its arrival.

As for the pet’s former owners, Howard said her son was upset to lose the caiman but thankful that he wouldn’t face any penalties.

“The officers said that because he cooperated they wouldn’t go through with an arrest or a ticket of any kind,” the mother said.

Animal Control and Lawrence police did not return calls for comment Thursday.