When the almighty paeleontologist Jack Horner aroused interest in his thesis that Tyrannosaurus was a scavenger, like a vulture, there was one bearded man who stood up and said:

“Fuck that”

(He didn’t actually, but you get the idea).

That man was Robert T. Bakker, who became Horner’s biggest rival in the field of paeleontology. In fact, their rivalry was so fierce that when Horner was working as a scientific adviser for the Jurassic Park trilogy, he featured a scene in The Lost World depicting the brutal death of a Bakker lookalike. In the film, this fictional Paeleontologist is displayed as overly enthusiastic and unintelligent, sporting Bakker’s trademark beard and only thinly disguised with the name “Burke”.

In the scene, Burke is hiding from a Tyrannosaur behind a waterfall, when he is startled by a coral snake. Fleeing the snake, he runs out of the safety of the cave, to be swiftly devoured.

Jack Horner clearly fucked up though, as Bakker picked up on this and mailed Horner the message:

“I told you Rex was a predator!”

Anyway, back to the paper I read.

It uses the Kowalevskian idea of evolution (that animals evolve towards adaptive needs because of a shift in environmental resources) to explain how Allosaurus opens its jaws to angles of well over 90 degrees.

It uses the example of how Sabre-Tooth cats were much smaller than their prey, and had to evolve to still stand a chance of survival. To continue hunting bulky proboscideans (aka shit with trunks) the STCs needed to change the shape of their skull. The lower jaw had to be able to move out of the way of the Sabres, meaning there needed to be a massive open jaw angle. They also had to attack larger prey with their head pointing up, using muscles behind the head to drive down on a bigger area with the teeth.

The adapted skulls allowed the jaw to be pulled more down and backwards than others, and the muscles and shallow glenoid (curve in the bottom of the skull that the lower jaw touches) stops the jaw from dislocating when opening >90 degrees.

What Bakker is saying is that in the Late Jurassic, the common prey fauna was massive. With an average femur (thigh) length of over 80cm among sauropods (aka things with long-ass necks), the predators had to adapt. Unlike other Jurassic predators like Ceratosaurs and Megalosaurs, Allosaur teeth are often found broken off near sauropod kills. This is irrefutable proof that Allosaurus hunted massive sauropods as regular prey. Megalosaur and Ceratosaur attacks on sauropods have been confirmed, but the circumstances have always been “rare and concentrated in unusual environments”.

From this evidence, Bakker made the link between the fine-tuning of the Allosaurus skull to kill big shit and the Kowalevskian evolution of the Sabre-Tooth cats. Allosaurus could pull its jaws open really wide, but it had small teeth.

Although this sounds like a problem, Bakker hypothesizes that the teeth act as a serrated blade to cause massive trauma, driven by a highly specialised neck musculature formation known as a rib-shaft-bundle. This allows slashing bites over a big bit of sauropod flesh, sawing off meat and allowing an easier kill. Bakker likens the upper Allosaur jaw to a “Samoan war-club”.

The rib-shaft-bundle is a feature lost from modern birds, but was present in large therapods (T.Rexes and shit, for all you commoners).

This type of physical attack would not kill big game like a sauropod, but it would definitely weaken it. Several of these bites would down a large dinosaur, and, if more recent studies are correct, Allosaurus hunted (if only occasionally) in small groups.

So basically, Allosaurids could open their jaws to 120° and kill Apatosaurs and they were pretty cool.

That is all.