Offacolidae is a family of basal euchelicerate arthropods from the Ordovician and Silurian of Europe, Morocco and North America.

[1][2] The family is united by several features, including paddle-like sixth post-cheliceral appendages, elongated chelicerae, and reduced first tergites (although these are apparently not unique to the clade, but instead euchelicerate or wider synapomorphies, therefore making the clade paraphyletic [citation needed]).

They share with most other euchelicerates a wide carapace, which has led to them being placed in the paraphyletic “Synziphosurina” for a long time, however more detailed studies have led to them being separated.

[3] This prehistoric arthropod–related article is a stub.

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