''Illaenus crassicauda'' is a species of
trilobite
Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the At ...
s belonging to the family
Illaenidae
The Illaenidae are a family of trilobites in the order Corynexochida. 223 currently accepted species in 24 genera are known from the Ordovician. Some scholars include the Panderiidae in the Illaenidae, but this is not generally supported.
Distr ...
. These trilobites lived in the middle
Ordovician and in the Silurian age (443 - 418 million years ago). Fossils of this species have been found in the sediments of Sweden and Russia.
Etymology
The Latin species name ''crassicauda'' means "fat-tailed", with reference to the shape of the
pygidium.
Description
''Illaenus crassicauda'' can reach a length of about . These trilobites are without glabella and without articulation of the tail. The
cephalon
Cephalon, Inc. was an American biopharmaceutical company co-founded in 1987 by pharmacologist Frank Baldino, Jr., neuroscientist Michael Lewis, and organic chemist James C. Kauer—all three former scientists with the DuPont Company. Baldino s ...
has a high profile. The large bulbous head are distant from the axis of the head, close to the margin.
Archive.org
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References
* V. Jaanusson
Zur Fauna und zur Korrelation der Kalksteine mit Illaenus crassicauda (sog. Flagkalk) im Siljan-Gebiet Dalarnas
Geologiska Föreningen i Stockholm Förhandlingar - Volume 69, Issue 1, 1947
External links
Fossil ID
Illaenina
Ordovician trilobites
Ordovician trilobites of Europe
Ordovician trilobites of Asia
{{Corynexochida-stub