At the start of their research, paleobiologists Christine Janis and Borja Figueirido simply wanted to determine the hunting style of an extinct marsupial called Thylacine (also known as the "marsupial wolf" or the "Tasmanian tiger").
In the end, the Australian relic, which has a very dog-like head but with both cat- and dog-like features in the skeleton, proved to be uniquely unspecialized, but what emerged from the effort is a new classification system that can capably predict the hunting behaviors of mammals from measurements of just a few forelimb bones.
Brown University researchers have devised a dataset of forelimb bone measurements that can be used to classify the hunting style of mammalian predators. The now-extinct thylacine (front), shown juxtaposed with its still extant Australian rival the dingo, had forelimb anatomy that was curiously unspecialized for any particular hunting style.
Credit: Image courtesy of Carl Buell
"We realized what we are also doing was providing a dataset or a framework whereby people could look at extinct animals because it provides a good categorization of extant forms," said Janis, professor of ecology and evolutionary biology at Brown University, and co-author of a paper describing the framework in the Journal of Morphology.
For example, the scapulas (shoulder blades) of leopards (ambush predators who grapple with rather than chase their prey) and those of cheetahs (pursuit predators who chase their prey over a longer distance) measure very differently. So do their radius (forearm) bones. The shapes of the bones, including areas where muscles attach, place the cheetahs with other animals that evolved for chasing (mainly dogs), and the leopards with others that evolved for grappling (mostly other big cats).
"The main differences in the forelimbs really reflect adaptations for strength versus adaptations for speed," Janis said.
In plots of the data in the paper, cheetahs and African hunting dogs appear to be brethren by their scapular proportions even though one is a cat and one is a dog. But the similar scapulas don't lie: both species are acknowledged by zoologists to be pursuit predators.
In all, Janis and Figueirido of the Universidad de Malaga in Spain made 44 measurements on five forelimb bones in 62 specimens of 37 species of ranging from the Arctic fox to the thylacine. In various analyses the data proved helpful in sorting out the behaviors of their bones' owners.
Given measurements from all of the forelimb bones of an animal, for example, they could accurately separate ambush predators from pursuit predators 100 percent of the time and ambush predators from pouncing predators 95 percent of the time. Results were similar for analyses based on the humerus (upper arm bone). They were always able to make correct classifications between the three predator styles more than 70 percent of the time, even with just one kind of bone.
The elusive thylacine
The thylacine has not been known from mainland Australia in recorded human history, and by official accounts it disappeared from the Australian island of Tasmania by 1936 (although some locals still believe they may be around). In a similar vein, the beasts evaded Janis and Figueirido's attempts at a neat classification of their mode of carnivory. By some bones they were ambushers. By others they were pursuers. In the end, they weren't anything but thylacines.
Janis notes that they could do just fine as generalists, given their relative lack of competition. Historically Australia has hosted less predator diversity than the Serengeti, for example.
"If you are one the few predators in the ecosystem, there's not a lot of pressure to be specialized," she said.
In the thylacine's case the evidence from forelimb bone measurements supports their somewhat unusual status by the standards of the rest of predatory mammals as generalists. For other extinct predators, the framework will support other conclusions based on these same standards.
"One thing you tend to see is that people want to make extinct animals like living ones, so if something has a wolf-like head with a long snout as does the thylacine, although its skull is more delicate than that of a wolf, then people want to make it into a wolf-like runner," she said. "But very few extinct animals actually are as specialized as modern day pursuit predators. People reconstruct things in the image of the familiar, which may not reflect reality."
But Janis said she hopes the framework will provide fellow paleobiologists with an empirical basis for guiding those determinations.
The Bushnell Foundation supported the study with a research and teaching grant. The Museum of Comparative Zoology at Harvard University, the American Museum of Natural History in New York, and Australia's Museum Victoria and Queensland Museum provided access to specimens for measurement.
David Orenstein | Eurek Alert!
Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz
Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences