''Ellipsocephalus'' Zenker, 1833, is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of blind Cambrian

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 ...

, comprising benthic species inhabiting deep, poorly lit or

aphotic The aphotic zone (aphotic from Greek prefix + "without light") is the portion of a lake or ocean where there is little or no sunlight. It is formally defined as the depths beyond which less than 1 percent of sunlight penetrates. Above the aphot ...

habitats. ''E. hoffi'' is a common trilobite mainly from central Europe (Czech Republic). Ellipsocephalus sanctacrucensis

Distribution

* ''E. hoffi'' (Schlotheim, 1823) occurs in the

Middle Cambrian Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (disambiguation) * Middle Brook (disambiguation) * Middle Creek ...

of the Czech Republic, Jince Formation, ''Ellipsocephalus hoffi''–''Paradoxides'' (''Rejkocephalus'')–''Lingulella'' Biozone of Fatka & Szabad (2014). * ''E. polytomus'' Linnarsson, 1877, is widely distributed in the ‘Oelandicus Beds’ (''Baltoparadoxides oelandicus'' Biosuperzone) of Sweden and found near Viken, Näkten lake, Närke and Jämtland. The species is also known from drill cores retrieved from the island of Gotland, Sweden (e.g., Ahlberg 1989). * ''E. sanctacrucensis'' (Samsonowicz, 1959) is known from the

of Poland (Słowiec Sandstone Formation, ''Paradoxides insularis'' and ''P. pinus''-zones, near Brzechów, Holy Cross Mountains).

Description

''Ellipsocephalus'' is approximately oval in shape and markedly convex. It has opistoparian facial sutures that are directed slightly outward from both front and back of the eyes. The glabella has approximately parallel, slightly concave sides and is rounded frontally. Lateral furrows are indiscernible, as is the occipital ring. The palpebral lobes are not distinctly separated from the narrow occular ridges. The preglabellar field is somewhat inflated and librigenae are half as wide as the fixigenae. Some species have genal spines (as in ''E. sanctacrucensis''), whereas in the most common species (''E. hoffi'') the genae lack spines and are only slightly angular posterolaterally. ''Ellipsocephalus'' has 12

thoracic The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the crea ...

segments and the pygidium is 4× wider than long.

Behaviour

''Ellipsocephalus'' and some other primitive micropygous Cambrian genera, such as '' Bailiella'', enroll differently from other trilobites so that the posterior thorax segments and pygidium bend under the thorax. This is called "double enrollment".

References

Sources

'' Trilobite info (Sam Gon III)''

External links

'' Trilobite info (Sam Gon III)''
{{Taxonbar, from=Q3723539 Ellipsocephalidae Ptychopariida genera Cambrian trilobites Fossils of the Czech Republic Paleozoic life of New Brunswick Cambrian genus extinctions