The Paradoxididae are a
family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
of
trilobites
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 ...
, a group of
extinct marine
arthropods. They occurred during the late
Lower Cambrian
The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago ( ...
(
Toyonian) and disappeared at the end of 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 ...
. Representatives of this family have been found in the
paleocontinents of
Avalonia,
Baltica
Baltica is a paleocontinent that formed in the Paleoproterozoic and now constitutes northwestern Eurasia, or Europe north of the Trans-European Suture Zone and west of the Ural Mountains.
The thick core of Baltica, the East European Craton, ...
, and
Gondwana, now Canada (Nova-Scotia, New Brunswick, Newfoundland), USA (Massachusetts, South Carolina), England, Wales, Morocco, Spain, Czech Republic, Poland, Russia (Novaya Zemlya, Northern Siberia, North-East Yakutia), Mongolia, and Turkey. Species in this family can typically grow large to very large (over 30 cm), are relatively flat, have an inverted egg-shaped outline,
opisthoparian sutures, a glabella that in early genera has parallel sides and expands forward in later representatives, and approaches or reaches the frontal border. All species have an almost semicircular headshield (or
cephalon) with long backward-directed genal spines. The articulate middle part of the body (or
thorax
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 cre ...
) consists of 15 to 21 segments ending in sickle-shaped spines that to the back curve increasingly further backwards. The tailshield (or
pygidium
The pygidium (plural pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compo ...
) is small.
References
External links
*
*
Paradoxidoidea
Trilobite families
Cambrian trilobites
Cambrian first appearances
Cambrian extinctions
{{Redlichiida-stub