Middle-grade novel about boy who hatches triceratops egg

Middle-grade chapter book about a farm boy whose chicken lays a strange egg. When it hatches, it's a triceratops! Read this in the 80s but illustrations had a 1950s-60s feel, so book is probably from that time period.

Sounds a lot like The Enormous Egg by Oliver Butterworth.

Also think The Enormous Egg.

That's the one, thanks!

Uncle Beazley the triceratops is still living at the national zoo, too, you can go see him. :)