Offacolidae

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. Alongside this, Offacolus may be more basal than the rest of the clade, as its seventh exopod pair is unreduced and it has a bipartite telson, among other features.^{[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]

Offacolidae Temporal range: Ordovician–Silurian PreꞒ Ꞓ O S D C P T J K Pg N
Restoration of Offacolus
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Chelicerata
Clade:	Euchelicerata
Family:	†Offacolidae Sutton et al., 2002
Type species
†Offacolus kingi Orr et al., 2000
Genera
†Offacolus †Dibasterium †Setapedites †Bunaia