Around 25 to 18.5 million years ago, cats seemed to have disappeared from North America. A period of 7 million years that scientists have called “cat gap”. To justify this absence of fossils, various theories have been put forward.
Is it the quest for a better hunting ground, the cooling caused by volcanic eruptions or even the climatic conditions of the time which were incompatible with their fossilization?
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Just because there aren’t any traces of the cats’ presence doesn’t mean “they weren’t there”
Carlo Meloro, paleontologist at Liverpool John Moores University in the United Kingdom remains cautious about the various suggestions proposed to explain the absence of felines in the territory. “These are only conjectures, he said in an interview relayed by LiveScience. If specific geological activities prevented the discovery of cats in North America in sediments during this time, that doesn’t necessarily mean they weren’t there.”
For the scientist, the “cat gap” could have been generated by “climate change, competition with other species and ecological displacement”. But how to be sure?
“The absence of cats cannot in any case be justified by the absence of fossils, abounds David Polly, paleontologist at Indiana University in Bloomington. The exclusion of cats from North America may, to some degree, simply be a coincidence involving the extinction of one cat group and the inability of another to enter North America.”
Three taxonomic families of cats present before the “cat gap”
Before this “disappearance” three taxonomic families of cats were present on the territory of North America: Nimravidae, Barbourofelidae and Felidae. These three groups, similar in appearance and genetically, did not all live in the same regions at the same time, which could explain the “cat gap”.
“In North America, the Nimravidae can be found during the Oligocene and up to 28.7 million years ago. They seem to have disappeared just before the “cat gap”. The Barbourofelidae, meanwhile , arrived in North America after the “cat gap”, with members of the genus Barbourofelis present between 11.5 and 9.8 million years ago”details Carlo Meloro at LiveScience.
It is the disappearance of the Nimravidae which makes it possible to define the beginning of the “cat gap”, explains David Polly for his part. “The extinction of the species is probably the result of a change in theecosystem American, in such a way that it has become difficult to function as a hyper-carnivore.”
A species close to the cat was therefore already extinct before the “cat gap” and a second had not yet migrated to North America.
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The immigration of felines to North America probably took place between 23.03 and 5.3 million years ago, when the sea level experienced variations. “The cats crossed through Siberia, all the way to Alaska”, suggests David Polly. But this land bridge “would have required both low sea level and suitable ecosystems in this area”.
This is the reason why very few cat fossils were discovered in North America during the “cat gap” period. Not because of a “disappearance” but perhaps simply because there was none.
David Martill, paleontologist from the University of Portsmouth in the United Kingdom, raises another point concerning the absence of felid fossils. “The fossil record is extremely patchy and how many people go looking for cat fossils?” A theory deemed plausible by David Polly.
“The fossil record does not uniformly sample all of North America, so it is possible that nimravids persisted over 23 million years ago in some corners of the continent, or that felids arrived in some areas before 17 million. years”, he explains before adding: “The fossil record of mammals, including carnivores, is very good in North America during the ‘cat gap’.”
So the mystery remains.
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