Prehistoric desert snails

Prehistoric desert snails

Earlier this year, Te Papa received a small collection of precious fossils snails from Algeria. But size is not a good indicative of importance – these snails are a new find, from a fossil outcrop that had never been studied before. So we set out to study them, of course, alongside two colleagues from Algeria.

The fossil outcrop is part of a cliff facing the sea, just nearby the city of Beni Saf, in the northwestern part of the country. The rock beds are made up largely of a coarse sandstone, very red in color and visually impressive, but a little rough on the fossils.

Beni Saf snails 1
We found lots of fossils, but they are not typically well preserved. The two images on the left side are Tudorella sulcata and the two on the right are Leonia sp. (specimens MNZ M.326502 and UTl.lab25.-BS1-2, respectively).

Even though the sandstone in Beni Saf is not ideal for preserving fossils, we could still find several species there: 13 in total. One important find was Rumina atlantica, which until now was only known from a single fossil outcrop in Oran.

Beni Saf snails 2
Snails belonging to the genus Rumina lose the slender tip of the shell (leftmost images) as they grow. The shells of the adults (rightmost images) end up looking broken or truncated. The one in the far right is Rumina atlantica (specimen MNZ M.326503); immediately to its left is a Rumina decollata (MNZ M.326504); the remaining shells are all juveniles (MNZ M.326505).

We could not precisely determine how old the fossils are using chemical analyses: the sediments are not entirely suitable for that. However, we could correlate the rock beds to other outcrops in Algeria, which gave us a nice idea of the fossils’ age. They date back to the early Pleistocene epoch, which is roughly 2 million years ago.

Also, we could analyse the composition of the fauna (which species and families are present), alongside the clues found in the rocks themselves, to define how the environment looked like back then. All these snails belong to groups that can survive conditions much more arid than our typical snails ever see. Two million years ago, that place ‘near Beni Saf’ would have been dominated by dunes, with a central wadi (that is, an ephemeral river bed). We would have only found sparse vegetation growing there, mostly grasses and a few shrubs.

The research article was published on the latest issue of the French journal Annales de Paléontologie.

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