Paleontologists give Madagascar’s dinosaur a hand

New study shows that fearsome dinosaur Majungasaurus had stubby forelimb, awkward fingers, no claws.

By SOCIETY OF VERTEBRATE PALEONTOLOGY
January 14, 2012 04:09
3 minute read.
Majungasaurus crenatissimus

Majungasaurus crenatissimus 311. (photo credit: Lucille Betti-Nash)

 
X

Dear Reader,
As you can imagine, more people are reading The Jerusalem Post than ever before. Nevertheless, traditional business models are no longer sustainable and high-quality publications, like ours, are being forced to look for new ways to keep going. Unlike many other news organizations, we have not put up a paywall. We want to keep our journalism open and accessible and be able to keep providing you with news and analyses from the frontlines of Israel, the Middle East and the Jewish World.

As one of our loyal readers, we ask you to be our partner.

For $5 a month you will receive access to the following:

  • A user experience almost completely free of ads
  • Access to our Premium Section
  • Content from the award-winning Jerusalem Report and our monthly magazine to learn Hebrew - Ivrit
  • A brand new ePaper featuring the daily newspaper as it appears in print in Israel

Help us grow and continue telling Israel’s story to the world.

Thank you,

Ronit Hasin-Hochman, CEO, Jerusalem Post Group
Yaakov Katz, Editor-in-Chief

UPGRADE YOUR JPOST EXPERIENCE FOR 5$ PER MONTH Show me later Don't show it again

DEERFIELD, IL – 66 million years ago, the fearsome, meat-eating dinosaur Majungasaurus crenatissimus prowled the semi-arid lowlands of Madagascar. Its powerful jaws bristled with bladelike teeth, and its strong legs terminated in formidable claws. Not even its own kin were safe, for given the chance, Majungasaurus was known to engage in cannibalism. Now, a new study published in the Journal of Vertebrate Paleontology shows that there was one part of its dreadful form that was not to be feared: its arms.

First discovered in 1895, Majungasaurus became well known through hundreds of fossils recovered by the joint Mahajanga Basin Project of Stony Brook University and the Université d’Antananarivo between 1993 and 2007. Nearly every structure – from its cranial sinuses to an injury on its tail – has been described in great detail. But the anatomy of Majungasurus’ forelimb has remained a mystery until now.

Be the first to know - Join our Facebook page.


Lead author Sara Burch, of Stony Brook University, says the arm of Majungasaurus epitomizes the unique forelimb anatomy of abelisaurids, a group of theropod dinosaurs known almost exclusively from southern landmasses collectively known as Gondwana. “The proportions of this limb are unlike anything we see in other theropods. The forearm bones are short, only a quarter of the length of the humerus (upper arm bone), but extremely robust. The wrist bones aren’t even ossified, and the stubby fingers probably lacked claws. The proportions are so strange, it ends up looking like a hand stuck on the end of a humerus.”

Limb reduction is nothing new for theropods; it’s accentuated in the caricature of the mighty Tyrannosaurus rex. Terrifying, to be sure, but with arms too puny to scratch its own face. “Another group of theropods, the alvarezsaurs, go their own odd way with limb reduction,” says co-author Matthew Carrano of the Smithsonian Institution. “These dinosaurs also had very short hands and very short forearms.” And modern-day theropods (those feathered fellows you see flying around) have even lost some digits through evolution. Might one of these scenarios explain the anatomy of Majungasaurus? Not likely, says Burch. “While many theropods have reduced limbs, most retain their normal proportions. We don’t know of any other case where the forearm bones have become more robust in this way. Abelisaurids like Majungasaurus were clearly on a completely different trajectory from the lineage leading to birds.”

With no modern analogs, it’s difficult to speculate on how this stubby forelimb was used. But, says Burch, “grasping is out of the question – there’s no way this animal was doing much manipulation with such a reduced hand. The joint anatomy suggests great mobility at the elbow and wrist, but the individual digits probably could not have moved independently.” The limb may have been used in display, or it may represent an unknown evolutionary path that was cut short by the Cretaceous-Tertiary extinction.

Paleontologist Jonah Choiniere of the American Museum of Natural History, who was not involved with the study, says that the arm of Majungasaurus provides crucial information about theropod evolution. “Until now, most knowledge of the forelimb in abelisaurids has come from two South American species, Carnotaurus sastrei and Aucasaurus garridoi. Thanks to this study, we now know that this morphology was more widespread throughout Gondwana during the Late Cretaceous. What’s more, we now have a solid base for understanding forelimb anatomy in abelisaurids. The next steps are to relate the anatomy to other, more basal theropods and develop robust evolutionary hypotheses for how this bizarre forelimb evolved.”

This article was first published at www.newswise.com

Related Content

Holland Park’s forest, north of Eilat.
August 11, 2014
Promising trend of prosecution for environmental crimes, officials say

By SHARON UDASIN