The Paradoxididae are a
family
Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
of
trilobites, a group of
extinct
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
marine
arthropods
Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...
. They occurred during the late
Lower Cambrian (
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 (di ...
. Representatives of this family have been found in the
paleocontinents of
Avalonia,
Baltica, 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) consists of 15 to 21 segments ending in sickle-shaped spines that to the back curve increasingly further backwards. The tailshield (or
pygidium) is small.
References
External links
*
*
Paradoxidoidea
Trilobite families
Cambrian trilobites
Cambrian first appearances
Cambrian extinctions
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