Hibbertopteroidea
| Hibbertopteroidea Temporal range: Early Silurian - Late Permian, 442–252 Ma |
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| Reconstruction of Hibbertopterus, a hibbertopterid. | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Chelicerata |
| Class: | Merostomata |
| Order: | †Eurypterida |
| Suborder: | †Stylonurina |
| Superfamily: |
†Hibbertopteroidea Kjellesvig-Waering, 1959 |
| Families | |
Hibbertopteroidea is an extinct superfamily of eurypterids, an extinct group of merostomatan arthropods commonly known as "sea scorpions". It is one of four superfamilies classified as part of the suborder Stylonurina.
Hibbetopteroids were large bizarre Eurypterids found from the Early Silurian to the end of the Permian period. They were sweep feeders, inhabiting freshwater swamps and rivers, feeding by raking through the soft sediment with blades on their anterior appendages to capture small invertebrates. Their morphology was so unusual that they have been thought to be an order separate to Eurypterida. Recent work however confirms them to be derived members of the suborder Stylonurina, with the genus Drepanopterus being a basal member of their superfamily.
The Hibbertopteroids are important within eurypterid evolutionary history as the last group of eurypterids to experience a significant radiation in diversity at the genus level (during the Late Devonian and Carboniferous) as well as being the latest known surviving members of the group, going extinct during the Permian-Triassic extinction event.
Hibbertopteroids are diagnosed as stylonurines with a posterior cleft on the metastoma and rounded lenses overlaying the lateral eyes as well as having anterior prosomal appendages modified for sweep-feeding.
Sweep-feeding strategies evolved independently in two of the four stylonurine superfamilies, the Stylonuroidea and the Hibbertopteroidea. In both superfamilies, the adaptations to this lifestyle involves modifications to the spines on their anterior prosomal appendages for raking through the substrate of their habitats. Stylonuroids have fixed spines on appendages II-IV which could have been used as dragnets to rake through the sediments and thus entangling anything in their way. Hibbertopteroids show even more extreme adaptations towards a sweep-feeding lifestyle.
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