Which one of the following is reptilian ancestor of birds?

Step-by-step solution

The first fossil birds found in the rocks of Jurassic period belonged to genera Archaeopteryx and Archaeornis. These are considered as reptilian ancestors of birds. It was about the size of a crow and possessed feathers and wings but had a long reptilian tail very much unlike the modern birds and a toothed beak. Fossils of Hesperornis, an aquatic diving bird, and Ichthyornis, a powerful flying bird, have been found from Cretaceous.