description Onnia Overview
Onnia is a genus of trinucleid trilobites from the Ordovician Period. It is known from parts of Europe and North Africa and belongs to a group characterized by a broad cephalic fringe. The fringe contains numerous regularly arranged perforations, giving the cephalon a distinctive sieve-like appearance. Onnia is relevant to studies of Ordovician trilobite diversity, cephalic construction, and the evolution of trinucleid feeding or sensory structures.
help Onnia FAQ
What period did the trilobite Onnia live in?
Onnia lived during the Ordovician Period and belongs to the trinucleid trilobites. The group is recognized for unusual cephalic structures rather than the smooth, simple head shapes seen in some other trilobites.
What is the perforated fringe on an Onnia fossil?
Onnia has a broad cephalic fringe containing many regularly arranged perforations. This sieve-like fringe is a defining feature of trinucleid trilobites and is often the first part examined during identification.
Where have Onnia fossils been found?
Onnia is known from parts of Europe and North Africa in Ordovician marine rocks. The broad geographic range shows that the genus was not limited to a single modern country or fossil basin.
How can I distinguish Onnia from a more ordinary trilobite?
Start with the head, or cephalon, because Onnia has a wide fringe with regularly spaced holes. That perforated structure, together with its Ordovician age, is more useful for identification than the overall body outline alone.
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