Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Paleontologists Give Madagascar’s Fiercest Dinosaur a Hand

13.01.2012
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.

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.”

ABOUT THE SOCIETY OF VERTEBRATE PALEONTOLOGY
Founded in 1940 by thirty-four paleontologists, the Society now has more than 2,300 members representing professionals, students, artists, preparators and others interested in vertebrate paleontology. It is organized exclusively for educational and scientific purposes, with the object of advancing the science of vertebrate paleontology.
The Journal of Vertebrate Paleontology
The Journal of Vertebrate Paleontology (JVP) is the leading journal of professional vertebrate paleontology and the flagship publication of the Society. It was founded in 1980 by Dr. Jiri Zidek and publishes contributions on all aspects of vertebrate paleontology.

For complimentary access to the full article beginning January 13, 2012, visit: http://www.tandfonline.com/loi/ujvp20

The article appears in the Journal of Vertebrate Paleontology 32(1) published by Taylor and Francis.

Citation: S. H. Burch and M. T. Carrano. An articulated pectoral girdle and forelimb of the abelisaurid theropod Majungasaurus crenatissimus from the Late Cretaceous of Madagascar. Journal of Vertebrate Paleontology 32(1).

Journal Web site: Society of Vertebrate Paleontology: http://www.vertpaleo.org

AUTHOR CONTACT INFORMATION

Sarah H. Burch
Department of Anatomical Sciences
Stony Brook University
Stony Brook, New York, U.S.A.
sara.burch@stonybrook.edu
Matthew T. Carrano
Department of Paleobiology
Smithsonian Institution
Washington, District of Columbia, U.S.A.
carranom@si.edu
OTHER SCIENTISTS NOT DIRECTLY INVOLVED WITH THE STUDY
Jonah Choiniere
Division of Paleontology
American Museum of Natural History
New York, NY, U.S.A.
jchoiniere@amnh.org
Kristi Curry Rogers
Biology and Geology Departments
Macalester College
rogersk@macalester.edu
Phone: +1-651-331-6815 (cell)

| Newswise Science News
Further information:
http://www.vertpaleo.org

More articles from Earth Sciences:

nachricht Impacts of mass coral die-off on Indian Ocean reefs revealed
21.02.2017 | University of Exeter

nachricht How much biomass grows in the savannah?
16.02.2017 | Friedrich-Schiller-Universität Jena

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Microhotplates for a smart gas sensor

22.02.2017 | Power and Electrical Engineering

Scientists unlock ability to generate new sensory hair cells

22.02.2017 | Life Sciences

Prediction: More gas-giants will be found orbiting Sun-like stars

22.02.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>