Mawsonia is an extinct relative of the modern day coelacanth that inhabited Africa and South America. It was the largest of the coelacanth group, capable of attaining lengths of up to 6 meters. It lived during the Cretaceous Period and was discovered in 1907.

In The Land Before Time

Mawsonia is seen in The Land Before Time IX: Journey to Big Water, where one is seen living in Mo's Home. This same Mawsonia is seen swimming nearby Littlefoot.