Dryptosaurus aquilungis, Cope, 1866

Paul, G. S., 1988, Predatory Dinosaurs of the World, Predatory Dinosaurs of the World, New York: Touchstone Books, pp. 323-349 : 346-349

DRYPTOSAURUS AQUILUNGIS (Cope, 1866)

synonym— Laelaps aquilungis

type— ANSP 9995

time ----- Late Maastrichtian of the late Late Cretaceous

horizon and distribution—New Egypt Formation of New Jersey

MAIN ANATOMICAL STUDY—Cope, 1870

	Type
FEMUR LENGTH— —	890 890 mm mm
TONNAGE— —	~ ~1.5 1.5??

I discuss this species here for a lack of anywhere better to do it; it is being reexamined by Kenneth Carpenter and Dale Russell. This large, gracile, aberrant, and poorly known theropod has been considered everything from a megalosaur to a tyrannosaur, to even a dromaeosaur protobird. It is none of these. The ankle is advanced and looks avetheropodian, but it is also different from other theropods, so this taxa is a unique form. A number of other theropod remains in the United States have been placed in this genus; all are dubious at best. It seems that the forelimbs are large and have very big claws, and the teeth are fairly normal blades. Duckbills were among this big animal’s prey.

Many features link protobirds and birds. For one example, in birds the snout is reduced. The maxilla, preorbital openings, jaw-closing muscles, and smell organs the snout contains are all reduced or lost. These things can be seen developing in protobirds; even the preorbital opening of Velociraptor is small compared to nonprotobird theropods. A common, but not strict, protobird trait is to have well-developed binocular vision. The way in which protobird eyes faced forward usually differed from that of tyrannosaurs (for an exception, see comments on Dromaeosaurus, pages 349-51). In protobirds the frontals that make up the skull roof above the eye sockets are triangular and broader over the back of the eye socket; this is the bird way of binocular vision. But the purpose of stereo vision was the same in tyrannosaurs, protobirds, and birds: to improve the precision of head strikes.

Notice that unlike the hips of other theropods, here the long rod is missing from the end of the ischium bone. This means that the ischial-based limb muscles again anchored along most of the bones’ length, as they had in the earliest dinosaurs. This is also an avian feature, and it probably had to do with the equally birdlike initial backward-swinging of the pubis. In 1969, Dale Russell suggested that the slender, bowed outermost digit of the hand of Troodon could rotate backward on the wrist bones and oppose the other fingers, somewhat the way our thumb does. If correct, then this would apply to Archaeopteryx, dromaeosaurs, and perhaps oviraptors too, because they have similar hands.

It is remarkable how ready for avian-style flight the Jurassic avetheropods were. All they had to do was elongate their forelimbs, modify them a little, and increase their power, and they could have flown.