Prehistoric desert snails

Prehistoric desert snails

Did you know snails can live in the desert? Natural history researcher Rodrigo Salvador tells us a little about a curious set of fossils discovered in Algeria.

Earlier this year, Te Papa received a small collection of precious fossils snails from Algeria.

The snails were found in a fossil outcrop that had never been studied before and the perspective of studying a new outcrop is always thrilling.

I was invited by a duo of Algerian researchers to study these snails because they were familiar with some of my previous work on similar fossils.

After exchanging lots of emails, the fossils finally arrive at Te Papa for study.

The fossil outcrop

The fossil outcrop is part of a cliff facing the sea, just nearby the city of Beni Saf, in the northwestern part of Algeria.

The rock beds are made up largely of a coarse sandstone, red in colour, and visually impressive.

However, this kind of sediment does not favour a perfect fossilization, so most of the fossils had just bits and pieces of their original shells preserved.

Even though the sandstone in Beni Saf is not ideal for preserving fossils, we could still find several species there: 13 in total. Twelve of those species still live in Algeria today, though not all of them still inhabit the region of Beni Saf.

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).

One important find was Rumina atlantica, which until now was only known from a single fossil outcrop in Oran.

This species is completely extinct.

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).

How old are the fossils?

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.

Snails that survive in arid environments

Fossil land snails are very good environmental indicators. Thus, they are extremely important in palaeontological studies because they allow us to reconstruct the past environments in which they lived.

We analysed the composition of the fauna (that means 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, this location near Beni Saf would have been dominated by dunes, with a central wadi (an ephemeral river bed).

There would have been only sparse vegetation growing there, mostly grasses, and a few shrubs.

What’s next?

I’m very grateful to my Algerian colleagues for inviting me to this project. As I write, they are looking for snails in other rocks around Beni Saf, so I hope that Te Papa will still receive more of these fantastic snails and that this is just the first of many works together.

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

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