Nav: Home

Long-necked dinosaurs rotated their forefeet to the side

January 29, 2019

Long-necked dinosaurs (sauropods) could orient their forefeet both forward and sideways. The orientation of their feet depended on the speed and centre of mass of the animals. An international team of researchers investigated numerous dinosaur footprints in Morocco at the foot of the Atlas Mountains using state-of-the-art methods. By comparing them with other sauropods tracks, the scientists determined how the long-necked animals moved forward. The results have now been published in the Journal of Vertebrate Paleontology.

"Long-necked dinosaurs" (sauropods) were among the most successful herbivores of the Mesozoic Era - the age of the dinosaurs. Characteristic for this group were a barrel-shaped body on columnar legs as well as an extremely long neck, which ended in a relatively small head. Long-necked dinosaurs existed from about 210 to 66 million years ago - they thus had been able to assert themselves on earth for a very long period. Also their gigantism, with which they far surpassed other dinosaurs, points at their success.

Sauropods included the largest land animals in Earth history, some over 30 metres long and up to 70 tonnes in weight. "However, it is still unclear how exactly these giants moved," says Jens Lallensack, paleontologist at the Institute of Geosciences and Meteorology at the University of Bonn in Germany. The limb joints were partly cartilaginous and therefore not fossilised, allowing only limited conclusions about the range of movement.

Detective work with 3D computer analyses

The missing pieces of the puzzle, however, can be reconstructed with the help of fossil footprints of the giants. An international team of researchers from Japan, Morocco and Germany, led by the University of Bonn, has now investigated an unique track site in Morocco at the foot of the Atlas Mountains. The site consists of a surface of 54 x 6 metres which was vertically positioned during mountain formation and shows hundreds of individual footprints, some of which overlap. A part of these footprints could be assigned to a total of nine trackways (sequences of individual footprints). "Working out individual tracks from this jumbled mess of footprints was detective work and only possible through the analysis of high-resolution 3D models on the computer," says Dr. Oliver Wings of the Zentralmagazin Naturwissenschaftlicher Sammlungen der Martin-Luther-Universität Halle-Wittenberg in Germany.

The researchers were amazed by the results: the trackways are extremely narrow - the right and left footprints are almost in line. Also, the forefoot impressions are not directed forwards, as is typical for sauropod tracks, but point to the side, and sometimes even obliquely backwards. Even more: The animals were able to switch between both orientations as needed. "People are able to turn their palms downwards by crossing the ulna and radius," says Dr. Michael Buchwitz of the Museum für Naturkunde Magdeburg. However, this complicated movement is limited to mammals and chameleons in today's terrestrial vertebrates. It was not possible in other animals, including dinosaurs. Sauropods must therefore have found another way of turning the forefoot forwards.

How can the rotation of the forefoot be explained?

How can the rotation of the forefoot in the sauropod tracks be explained? The key probably lies in the mighty cartilage layers, which allowed great flexibility in the joints, especially in the shoulder. But why were the hands rotated outwards at all? "Outwardly facing hands with opposing palms were the original condition in the bipedal ancestors of the sauropods," explains Shinobu Ishigaki of the Okayama University of Science, Japan. The question should therefore be why most sauropods turned their forefeet forwards - an anatomically difficult movement to implement.

A statistical analysis of sauropod tracks from all over the world could provide important clues: Apparently the animals tended to have outwardly directed forefeet when the foreleg was not used for active locomotion but only for carrying body weight. Thus the forefeet were often rotated further outwards when the animal moved slowly and the centre of mass of the body was far back. Only if the hands were also used for the forward drive, a forefoot directed to the front was advantageous. The analysis furthermore showed that the outer rotation of the forefeet was limited to smaller individuals, whereas in larger animals they were mostly directed forward. The large animals apparently could no longer rotate their forefeet sideways. "This loss of mobility was probably a direct result of their gigantism," says Lallensack.
-end-
Publication: Jens N. Lallensack, Shinobu Ishigaki, Abdelouahed Lagnaoui, Michael Buchwitz, and Oliver Wings: Forelimb orientation and locomotion of sauropod dinosaurs: Insights from the Middle Jurassic Tafaytour tracksites (Argana Basin, Morocco), Journal of Vertebrate Paleontology, DOI: 10.1080/02724634.2018.1512501

Contact:

Jens Lallensack
Institut für Geowissenschaften und Meteorologie
Universität Bonn
Tel. 0151-19661028
E-Mail: jens.lallensack@uni-bonn.de

University of Bonn

Related Dinosaurs Articles:

Volcanic eruptions triggered dawn of the dinosaurs
Huge pulses of volcanic activity are likely to have played a key role in triggering the end Triassic mass extinction, which set the scene for the rise and age of the dinosaurs, new Oxford University research has found.
Dinosaurs: Juvenile, adult or senior?
How old were the oldest dinosaurs? This question remains largely unanswered.
How the darkness and the cold killed the dinosaurs
66 million years ago, the sudden extinction of the dinosaurs started the ascent of the mammals, ultimately resulting in humankind's reign on Earth.
These dinosaurs lost their teeth as they grew up
By comparing the fossilized remains of 13 ceratosaurian theropod dinosaurs known as Limusaurus inextricabilis collected from the Upper Jurassic Shishugou Formation of northwestern China, researchers have been able to reconstruct the dinosaur's growth and development from a young hatchling of less than a year to the age of 10.
Dinosaurs' rise was 'more gradual,' new fossil evidence suggests
Researchers have discovered two small dinosaurs together with a lagerpetid, a group of animals that are recognized as precursors of dinosaurs.
Dinosaurs of a feather flock and die together?
In the paleontology popularity contest, studying the social life of dinosaurs is on the rise.
Unique skin impressions of the last dinosaurs discovered in Barcelona
Researchers from the Universitat Autònoma de Barcelona in collaboration with the Institut Català de Paleontologia Miquel Crusafont, have discovered in Vallcebre an impression fossil with the surface of the skin of a dinosaur from the Late Cretaceous, a period right before their extinction.
What dinosaurs' color patterns say about their lives
After reconstructing the color patterns of a well-preserved dinosaur from China, researchers have found that the long-lost species called Psittacosaurus was light on its underside and darker on top.
The success of the plant-eating dinosaurs
Plant-eating dinosaurs had several bursts of evolution, and these were all kicked off by innovations in their teeth and jaws, new research has found.
Soot may have killed off the dinosaurs and ammonites
A new hypothesis on the extinction of dinosaurs and ammonites at the end of the Cretaceous Period has been proposed by a research team from Tohoku University and the Japan Meteorological Agency's Meteorological Research Institute.

Related Dinosaurs Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Anthropomorphic
Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#532 A Class Conversation
This week we take a look at the sociology of class. What factors create and impact class? How do we try and study it? How does class play out differently in different countries like the US and the UK? How does it impact the political system? We talk with Daniel Laurison, Assistant Professor of Sociology at Swarthmore College and coauthor of the book "The Class Ceiling: Why it Pays to be Privileged", about class and its impacts on people and our systems.