Russian trilobites - 3D pictures



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	O ther trilobites

Trilobite

The trilobites of Russia, and specifically those coming from the Region near St.-Petersburg, near
the great Wolchov (Volhov) river, from the lower Ordovician, kunda level, Putilovo quarry, are
among those most cherished by collectors. There are a few reasons for it - their exotic forms,
superb preservation, high professional preparation, and availability. At the bottm there are a few
pictures of a place in Putilovo quarry where they were excavated out.

en.wikipedia.org
Trilobites are extinct arthropods in the class Trilobita. They appeared in the Cambrian period and flourished throughout the
lower Paleozoic era before slowly declining to extinction. The last of the trilobites disappeared in the mass extinction at the
end of the Permian 250 million years ago (m.y.a.).

Trilobites are very well-known, and possibly the second-most famous fossil group after the dinosaurs. They are the most
diverse group of animal species preserved in the fossil record, consisting of nine (or possibly ten) orders and over 15,000
species. The trilobites are currently included along with the Chelicerata in the group Arachnomorpha.

Most were simple, small marine creatures that walked along the seafloor and filtered mud to obtain food.

http://www.trilobite.com/
.The name Trilobite--meaning three lobed one-is in reference to the three longitudinal lobes across their heads (cephalon),
consisting of a slightly raised central lobe (the axis) and two flatter pleural lobes on either side. The entire bodies were also
divided into three: the head (cephalon), thorax (chest) made up to a group of up to 30 segments and the tail (pygidium).
Underneath and rarely preserved are three pairs of legs for the head and paired legs for each pleural groove. Trilobites are
the earliest known animal to possess vision. Some possessed eyes and some seem to have no eyes at all, while others
possessed beautiful compound eyes capable of 360 degree vision.

http://www.amonline.net.au
Trilobita is the most species-rich entirely extinct arthropod group. In trilobites, the hard exoskeleton covering the dorsal body
surface and its well marked segmentation (for example, the jointed segments of the thorax) are classic arthropod features.
The trilobite exoskeleton was mineralised, constructed of calcite. The trilobite hypostome, a plate attached to the lower side
of the head just in front of the mouth opening, corresponds to a similar structure (the labrum) in other arthropods. A pair of
compound eyes is developed in most trilobites, with the arrangement of their units (ommatidia) being typical of Arthropoda
(e.g., compound eyes in horseshoe crabs, crustaceans and insects). Trilobites periodically shed their exoskeleton to
accommodate growth; trilobite fossils sometimes preserve so-called moult configurations that show various stages in the
release of the old exoskeleton and escape of the then soft-bodied animal....

http://www.fossilmuseum.net
The Baltic limestone deposits that bear these trilobites was formed in seas of about 70 - 330 feet in depth in what was
probably a large shallow basin. Scientists believe that this basin was repeatedly blocked from contact with the sea to the
west,resulting in changes in both turbidity and salinity. Toward the end of the early Ordovician the connection was
re-established, with substantial deterioration in visibility in the seas due to the influx of more turbid water. At this time some
trilobites developed raised eyes perhaps to improve their vision both of potential prey as well as predators. The "periscope
eyes" of Asaphus Kowalewski were not yet evident as this species evolved somewhat later. While many trilobites were
detritivores feeding on animal and plant debris in the bottom muck, Asaphids are presumed to have been necrophagous,
meaning that they fed on dead carcasses, due to the shape of the hypostoma (platform for mouthparts).....