''Ellipsocephalus'' Zenker, 1833, is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of blind

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

trilobite Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...

, comprising

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...

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 (di ...

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 (: thoraces or thoraxes) or chest is a part of the anatomy of 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 ...

segments and the pygidium is four times 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