How the 'marsupial sabertooth' thylacosmilus saw its world CommsBio
Popularly known as the"marsupial sabertooth" because its extraordinarily large upper canines recall those of the more famous placental sabertooth that evolved in North America,lived in South America until its extinction about 3 million years ago. It was a member of Sparassodonta, a group of highly carnivorous mammals related to living marsupials.
Gaillard used CT scanning and 3D virtual reconstructions to assess orbital organization in a number of fossil and modern mammals. She was able to determine how the visual system ofwould have compared to those in other carnivores or other mammals in general. Although low orbital convergence occurs in some modern carnivores,was extreme in this regard: it had an orbital convergence value as low as 35 degrees, compared to that of a typical predator, like a cat, at around 65 degrees.
However, good stereoscopic vision also relies on the degree of frontation, which is a measure of how the eyeballs are situated within the orbits."was able to compensate for having its eyes on the side of its head by sticking its orbits out somewhat and orienting them almost vertically, to increase visual field overlap as much as possible," said co-author Analia M. Forasiepi, also in INAGLIA and a researcher in CONICET, the Argentinian science and research agency.
"It might have made predation easier in some unknown way," said Gaillard,"But, if so, why didn't any other sparassodont—or for that matter, any other mammalian carnivore—develop the same adaptation convergently? The canines ofdid not wear down, like the incisors of rodents. Instead, they just seem to have continued growing at the root, eventually extending almost to the rear of the skull.
Forasiepi underlined this point, saying,"To look for clear-cut adaptive explanations in evolutionary biology is fun but largely futile. One thing is clear:was not a freak of nature, but in its time and place it managed, apparently quite admirably, to survive as an ambush predator. We may view it as an anomaly because it doesn't fit within our preconceived categories of what a proper mammalian carnivore should look like, but evolution makes its own rules.
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