18 février 2017

Saccorhytus: ancêtre des vertébrés

Quelle fascinante découverte:

Researchers (...) say that fossilised traces of the 540-million-year-old creature are "exquisitely well preserved".

The microscopic sea animal is (...) the most primitive example of a category of animals called "deuterostomes" which are common ancestors of a broad range of species, including vertebrates (backboned animals).

Saccorhytus was about a millimetre in size, and is thought to have lived between grains of sand on the sea bed.

The researchers were unable to find any evidence that the animal had an anus, which suggests that it consumed food and excreted from the same orifice.

(...) "To the naked eye, the fossils we studied look like tiny black grains, but under the microscope the level of detail was jaw-dropping.

(...) Saccorhytus was also covered with a thin, relatively flexible skin and muscles, leading the researchers to conclude that it moved by contracting its muscles and got around by wriggling.

The researchers say that its most striking feature is its large mouth, relative to the rest of its body. They say that it probably ate by engulfing food particles, or even other creatures.

Also interesting are the conical structures on its body. These, the scientists suggest, might have allowed the water that it swallowed to escape and so might have been a very early version of gills.

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