Behold a baby Brontosaur bone

Object of the Month: 12/2017

What is it?:

Brontosaurus femur (juvenile)Baby bronto bone
Baby bronto boneCourtesy SMM


Age: Morrison Formation, 150 million years, late Jurassic
Where was it collected:

Poison Creek Quarry, Johnson County, WY, 1978


Dimensions:

9 inches long


Accession #: SMM P84.15.2c (cast)

The enormous Brontosaurus may have reached up to 15 feet tall, but each one started out as just a little shaver.

Hello little guy: SMM's Dick Benson stands along an artistic rendering of how small a baby Brontosaur would have been early in its life.
Hello little guy: SMM's Dick Benson stands along an artistic rendering of how small a baby Brontosaur would have been early in its life.Courtesy SMM
This nine-inch thigh bone is from a juvenile Brontosaurus that died between a few months to two years old. If it had reached full adult size, this bone could have grown to about 5.5 feet long. It was found with other juvenile bones, suggesting the young were part of a herd.

While research points to long-necked sauropod dinosaurs growing quickly through their early years, it’s very likely that Brontosaurs continually grew through their life span, just like most reptiles today.

Wait, I bet you thought brontosaurus was no longer an official dinosaur. Click here to learn about new research that has put Brontosaurus back on the dinosaur map!