Asaphus lepidurus trilobite 53mm from St. Petersburg, Wolchow River, Russia. dating from the Palaeozoic era, 490 to 470 million years. A fine example of a Russian Asaphus trilobite. The Asaphus lepidurus trilobite in an excellent state of preservation, the prone carapace or exoskeleton is not deformed as is often the case with the ravages of the fossil process. The carapace is fully inflated enabling a good study in a three dimension view of the attributes of the constituent body parts which make up this isopygous trilobite, the semi circular glabella with stub eye covers is a similar size to the pygidium which has faint ribbing noticeable on the axial lobe. The eight thoracic diagonally furrowed segments are crisply preserved and clearly definable.
In this genus of trilobite the three longitudinal lobes can be easily distinguished, these three lobes giving the arthropod its name from the Greek word trilobos, tri meaning three and lobos the lobes. The closest extant relative to the trilobite in the group arthropods are the horse crab or king crab, trilobites were thought to have a hard exoskeleton similar to the king crab today, composed of calcite and calcium phosphate minerals in a lattice of chitin this constituets the dorsal or upper carapace and protected the softer ventral body parts.
The bedrock or the fossil bedding plain has sustained a cleave which has run down the left side of the trilobite running through the thoracic segments, fortunately this has remained at the lower edge or margin of the trilobite. The base of the block which once formed the fossil bed has now been cut flat to aid presentation of the specimen. A good specimen Asaphus lepidurus trilobite from a classic trilobite lower Ordovician, the fossil Volhovian deposits, Asery level, Volkhov river, Baltic area, near St Petersburg, Russia.