If it was that of the carinate birds, how did the struthious birds and Dinosauria independently agree to differ?
Calyx 5-parted, fleshy, enclosing the fruit (utricle) and often carinate or crested.
Rostrum dilated towards its anterior end, compressed and carinate beneath the large presphenoid fossae.
All other existing birds belong to the second division, and are called (from the keel on the breast-bone) carinate birds.
carinate, keeled, furnished with a sharp ridge or projection on the lower side.
It must have been that of the struthious birds or that of the carinate birds, or something different from both.
Calyx 5- (rarely 6-) parted; its lobes long-acuminate, with carinate midrib.
The Rostro– carinate flints found at the base of the Crag are long bars with a beak–end, suited for breaking up earth.
carinate car·i·nate (kār'ə-nāt', -nĭt)
Shaped like or having a carina or keel; ridged.