Which of the following a synapomorphy linking dinosaurs and birds?

a. endothermy

b. small size

c. loss of teeth

d. furcula

d. furcula

Explanation:

Furcula

Furcula is a synapomorphy linking dinosaurs and birds.

The furcula is the structure formed by midline fusion of clavicles and this very element is unique in the theropods as well. And is the most crucial for understanding the link between birds and the theropods.

The first suggestion was by Huxley in 1868, and in 1870, the key component of the debate is the presence of Frucula.