Tyto robusta
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Tyto robusta Temporal range: Late Miocene/Early Pliocene |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Strigiformes |
| Family: | Tytonidae |
| Genus: | Tyto |
| Species: | †T. robusta |
| Binomial name | |
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Tyto robusta Ballmann, 1973 |
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| Synonyms | |
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see text |
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see text
Tyto robusta was a prehistoric barn-owl. It lived at what is now Monte Gargano in Italy, and was an island throughout much of the Neogene when sea levels were higher. The owl's remains date back to the Miocene-Pliocene boundary 5.5 to 5 million years ago. The fossil bones are about 60% as long again as a modern barn owl, giving a total length of about 50–65 cm for T. robusta. This owl provides an interesting case study of evolution and insular gigantism.
It was found sympatrically with the gigantic relative, Tyto gigantea, which at some 220% of the size of the barn owl grew to some 70–85 cm in length—larger than a Eurasian eagle-owl and maybe up to twice as heavy. Like other apex predators they can be presumed to have occurred at low population densities. Being apparently endemic to Gargano Island and perhaps some other islands in today's Apennines, where one or two huge eagles and at least at times a normal-sized barn-owl also occurred (though no large mammalian carnivores), these owls raise the question how minimum viable populations could be maintained long enough for them to live and prosper.
It is extremely commonplace for larger predatory birds such as Falconiformes and Strigiformes to evolve differently-sized sexes. Namely, the females being considerably larger with little or no overlap in size between sexes. This allows them to hunt for different-sized prey, allowing a larger, more resilient population to live off a land. But this was apparently not the case here, as there is a reasonably large sample of bones of each of the 3 owl taxa to display the natural and sexual variation within each.
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