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Gerastos Trilobites


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Gerastos Trilobites may vary slightly in size and colour - All our specimens are of the same quality as seen in the photograph.

Gerastos Trilobites discovered in the fossil bed formation 393 to 388 million years ago, in the J'bel Mrakib region, near the enclave of Alnif, in the western Sahara desert of Morocco.

Genus: Gerastos ainrasifus, described Gibb, Stacey and Chatterton.
Age: Paleozoic Era, Devonian Period, Eifelian age 393 to 388 million years.
Origin: Taboumakhloüf Formation, Djebel Issoumour, Alnif, Morocco, North Africa.

Approximate average Length: 2 to 2.5 cm
Approximate average weight each: 50 to 100 g

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Enrolled Gerastos ainrasifus trilobites discovered in the fossil bed 393 to 388 million years ago, in the J'bel Mrakib region, near the enclave of Alnif, the western desert of Morocco, each specimen with attributes of the genus type, selected and cleaned. The attributes of the arthropod jump out excellently well when viewed through a lens or with the naked eye. Running a finger over the pustules, bumps and pimply surfaces of the inflated head shield and the thoracic segments brings the bugs alive in one's hand.


These specimen trilobites are too we trilobite nerds at the Fossil store, little gems, we refer to these fossilised invertebrates as 'cute little fellas!' Maybe a little strange but we can't help loving these prehistoric arthropods. When out collecting in the desert, with each discovery in the fossil bed, we are delighted to unearth them and admire their unique crisp conservation and form. An excellent starter fossil for young collectors and a superb addition to nay ongoing collection.


Gerastos trilobites 25mm the Gerastos granulosus sp. Also known as Proetus tuberculatus, this trilobite is known for its tuberculate cephalon (head), or small granulose tubercles on the cephalon, hence the trilobites specific species is also easily identified by the inflated cephalon and large holochroal eyes and short cephalon genal spines. The Gerastos trilobites are members of the Proetida, this is the family of Proetidae dating from the Paleozoic era, the Devonian period approximately four hundred to three hundred and fifty million years ago. These little trilobites were among the last of the arthropods to become extinct in the Permian era, known as the great Permian extinction, approximately two hundred and fifty-two million years ago, when up to ninety percent of life became extinct. This was a cataclysmic global event soon to be followed by other extinction level events (see our blog posts for more detailed information), since the Ordovician trilobites had been in decline as types dropped away, like the Phacopidae at the end of the Devonian period, extinguishing the Phacopida lineage.


These fabulous trilobites have been prepared on the original matrix or bedrock to expose their exoskeleton, this is the carapace of the invertebrate made of a chitin (chitin, consists of calcite and calcium phosphate mainly, in a protein lattice), in the fossil process this hard chitin carapace calcifies (absorption of minerals in the fossil bed), over time creating what we see today, the fossilised remains of the once extant marine bottom dweller. The Gerastos trilobites have a remarkable likeness to modern day woodlouse arthropod, a segmented body cover and numerous legs, which is how we view the trilobite anatomy today. Excellent imagery has been developed particularly from the Burgess shale showing soft body parts within the fossil rock. Finding soft body parts is an extremely rare occurrence.


The Fossil Store continues fossil finding trips to North Africa collecting trilobites from our colleagues in the field and in laboratory workshops. Our long-term connections afford us the luxury of knowing what preparation has been carried out or rather what repairs have not been made to our specimens, thus enabling us to guarantee every trilobite we sell and issue documentation to guarantee the authentication of each.


The process of fossil collecting in the whole region of southern Morocco in the low lying Atlas ranges, the ranges here erupt from the desert, the northern Sahara and climb toward middle Morocco, Marrakesh and further north to the Riff valley, Mediterranean North Africa, also onto the western coast again falling back into the Atlantic, the practice of the fossil diggers is to literally crack open the fossil bedding plain into smaller pieces of rock, the rock is gradually reduced into hand sized nodules or slightly larger and finally cracked open one last time, when a trilobite is found the nodule is fixed back together and off to the lab for more technical extraction using pneumatic equipment and micro sand air abrasive machinery, taking many patient hours to release the fossil arthropod of its prehistoric tomb.


The experienced and sympathetic preparator can occasionally extract from the matrix, fossil bedrock, a marvellous complete specimen, as the Gerastos and Proteus listed here. Phylum Arthropoda, Class trilobita, Order proetida, Family proetidae described by Salter 1843.