Heavy is a hippopotamus

Miriam Schlein (June 6, 1926 – November 23, 2004) was an American author who wrote nearly 100 books (in 5 decades) that helped teach children about animals and more obscure ideas such as space and time. Her books include Discovering Dinosaur Babies (1991), The Dino Quiz Book (1995), and Before the Dinosaurs (1996). [source](