Comments on: Fearsome Dinosaur Had Ridiculously Short Arms

By: Nima

Nima — Sun, 29 Jan 2012 07:27:54 +0000

I’ll have to agree with Lisa here. The arms of abelisaurs are useless as weapons but make quite effective as sexual seduction tickle tools, and perhaps also as spurs for fighting males. The flexibility of the arms joints would have prevented serious injury, and the bizarrely huge shoulder blades may have been so big to protect the chest and upper torso against heavy impacts from sideswiping rivals. During these more heavy impacts the arm could be tucked down and back.

By: Lisa

Lisa — Sat, 28 Jan 2012 14:37:14 +0000

With a wide range of movement in the arms, but little to no actual manual dexterity… I think the arms may have been used like the ‘spurs’ on male boas and pythons (actually the remains of rear limbs, with the spur itself being a claw that is visible outside the body on either side of the cloaca).

Male boas and pythons use these spurs during mating, and move them back and forth to stroke or tickle the female. While this just helps to get the female ‘in the mood’ in boids, with large theropod dinosaurs, this ‘tickling’ could literally be a way of saying ‘I’m your mate – not your dinner!’

By: Peteykins

Peteykins — Wed, 25 Jan 2012 22:08:53 +0000

Perhaps whatever evolutionary forces caused Majungasaurus arms to become so small simply reached a tipping point: once the arms became that tiny, perhaps there was no longer any advantage to them becoming any smaller, so natural selection simply ceased to have any impact on the feature. I’m not an evolutionary biologist, so I honestly don’t know if that makes sense, but many vestigial features fail to vanish altogether. I’m thinking of some whale’s “feet” and the kiwi’s wings, as well as perhaps the human appendix.

I must say, though, that the image of it waving around its comical arms in panic made me giggle for a long time.

By: Harold

Harold — Wed, 25 Jan 2012 04:21:10 +0000

I suspect that by flapping its stubby little arms wildly the Majungasaurus could use them to signal panic, just like in humans.

Or maybe they were a sort of distraction device. While prey animals were doubled over in laughter at the Majungasaurus’s pathetic little arms, the Majungasaurus would casually stroll over and eat them.

By: Annie

Annie — Wed, 25 Jan 2012 02:23:05 +0000

Is there evidence for feather attachment in the surrounding matrix? The range of motion in combination with feathers could argue for the some sort display function, be it sexual or defensive.

By: Henrique Niza

Henrique Niza — Tue, 24 Jan 2012 22:53:43 +0000

I recall reading quite a bit about how supposed weak abelisaurs’ jaws were, specially Paul Sereno thoughts about how Rugops was primarily scavenger due its supposed weak skull. It seems feasible since their jaws look less robust than even allosaurs’ jaws and these didn’t have that strong bite.

By: Pedro Andrade

Pedro Andrade — Tue, 24 Jan 2012 20:33:14 +0000

And regarding Henrique Niza’s question: we know tyrannosaurids had powerful crushing skulls, has any work been done on abelisaurid biting strength?

By: Pedro Andrade

Pedro Andrade — Tue, 24 Jan 2012 20:31:36 +0000

Great article! What could be the purpose of Majungasaurus having such disproportionate limb bone sizes? More specifically, what use could such a big shoulder blade have if the muscles don’t need to support big arms?

By: Henrique Niza

Henrique Niza — Tue, 24 Jan 2012 19:41:12 +0000

The hypothesis that tyrannosaurs’ forelimbs were reduced due the enlargement of the skull doesn’t seem to apply to abelisaurs. Their skulls aren’t particularly massive but actually the contrary and their forelimbs aren’t just ridiculous short but atrophic too.

By: steve cohen

steve cohen — Tue, 24 Jan 2012 18:45:15 +0000

“This dinosaur’s arms and hands had become so reduced that it is difficult to imagine what they could have possibly done with them other than impotently flap them around. We may never know for sure.”

Scratch its belly after dinner??