Offacolidae

Offacolidae Temporal range: Ordovician–Silurian PreꞒ Ꞓ O S D C P T J K Pg N
Restoration of Offacolus
Scientific classification
Domain:	Eukaryota
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

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]

References

1. Lustri, Lorenzo; Antcliffe, Jonathan B.; Gueriau, Pierre; Daley, Allison C. (October 2024). "New specimens of Bunaia woodwardi Clarke, 1919 (Euchelicerata): a new member of Offacolidae providing insight supporting the Arachnomorpha". Royal Society Open Science. 11 (10). doi:10.1098/rsos.240499. PMC 11524597. PMID 39479250.
2. Lustri, Lorenzo; Gueriau, Pierre; Daley, Allison C. (7 May 2024). "Lower Ordovician synziphosurine reveals early euchelicerate diversity and evolution". Nature Communications. 15 (1). doi:10.1038/s41467-024-48013-w. PMC 11076625.
3. Lamsdell, James C. (January 2013). "Revised systematics of Palaeozoic 'horseshoe crabs' and the myth of monophyletic Xiphosura: Re-evaluating the Monophyly of Xiphosura". Zoological Journal of the Linnean Society. 167 (1): 1–27. doi:10.1111/j.1096-3642.2012.00874.x.