Not all dinosaurs were big or strange. Some were remarkably
similar to modern animals – for example, the ornithomimids that lived in
Maryland 115 million years ago looked for all the world like ostriches
with long tails. Standing six or seven feet tall, ornithomimids were
about the same size as ostriches, and like ostriches they had long
necks, small heads, and toothless beaks. Ornithomimid fossils from
Alberta, Canada show that these dinosaurs were covered in feathers,
including big plumes on their arms (the bald ornithomimid in the image
above was painted before this discovery, and is now considered out of
Why are ornithomimids so much like modern ostriches? For
one thing, these two animals are distant cousins – birds are a
specialized type of dinosaur that has survived to the present day.
However, ornithomimids are not true birds, nor are they especially close
to birds on the dinosaur family tree (the toothy dromaeosaurs, or “raptors”, are much closer).
The similarity between ornithomimids and ostriches is in fact a classic
example of convergent evolution. Sometimes distantly related animals
that live in similar ways and encounter similar problems evolve
remarkably similar anatomical solutions. For instance, sharks, dolphins,
and extinct marine reptiles called ichthyosaurs all evolved the same
fishy shape because they all specialize in hunting fish in the open
ocean. In the same way, ornithomimids and ostriches converged on the
same set of adaptations to survive in their respective habitats. Long
legs and compact feet help them run fast to escape from predators. Big
eyes help them see long distances, even at night. And a beak is useful
for plucking fruits, leaves, and seeds off of bushes and trees.
scientist Charles Gilmore first identified ornithomimid fossils from
Maryland in 1921. We're still finding the remains of these animals today
- especially the bones of their legs and feet.
Illustration by Mary Parrish, National Museum of Natural History.