Kokomopteroidea is an extinct superfamily of

eurypterid Eurypterids, often informally called sea scorpions, are a group of extinct arthropods that form the Order (biology), order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period 467.3 Myr, million yea ...

s, an extinct group of

chelicerate The subphylum Chelicerata (from New Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. It contains the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, and mite ...

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...

s commonly known as "sea scorpions". It is one of four superfamilies classified as part of the suborder

Stylonurina Stylonurina is one of two suborders of eurypterids, a group of extinct arthropods commonly known as "sea scorpions". Members of the suborder are collectively and informally known as "stylonurine eurypterids" or "stylonurines". They are known from ...

. Kokomopteroids have been recovered from deposits of Early Silurian to

Late Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wher ...

age in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

and the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...

Description

Kokomopteroids are stylonurines with a spiniferous appendage V and a posterior notch on the metastoma. The superfamily forms two distinct clades; the Kokomopteridae (including the genera '' Kokomopterus'' and '' Lamontopterus'') and the Hardieopteridae (including the genera '' Hardieopterus'', '' Tarsopterella'' and '' Hallipterus''). The Kokomopteroidea retains primitive ''

Hughmilleria ''Hughmilleria'' is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of ''Hughmilleria'' have been discovered in deposits of the Silurian age in China and the United States. Classified as part of the basal family Hughmille ...

''-type prosomal appendages for unsuitable raking through the bottom sediments of marine environments. As such, the members of the superfamily were likely

scavenger Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding b ...

s. The Hardieopteridae display some sweep-feeding characteristics similarly to members of the superfamilies Hibbertopteroidea and

Stylonuroidea Stylonuroidea is an extinct superfamily of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". It is one of four superfamilies classified as part of the suborder Stylonurina. Stylonuroidea, which lived from ...

, including a broadening of the metastoma and the spines of the anterior prosomal appendages. Hardieopterids may even have been benthic bottomdwellers partially living buried in the substrate.

Systematics and genera

The Kokomopteroids are

s classified as part of the suborder

. They are a sister group to the Hibbertopteroidea, united by a median ridge on the carapace between the lateral eyes and a distal thickening to the podomeres of the prosomal appendages. The primitive hibbertopteroid '' Drepanopterus'' is a sister taxon to all other hibbertopteroids and shares certain characteristics with the Kokomopteroidea (such as a clavate telson). Kokomopteroidea contains two families, the Kokomopteridae and Hardieopteridae. The Kokomopteridae is defined as kokomopteroids with undifferentiated opisthosoma with a marginal rim and the appendages II-V being spiniferous as in '' Lamontopterus'', with appendage VI not being spiniferous, as in '' Kokomopterus''. The Hardieopteridae is defined as kokomopteroids with lateral pleurae on the metasoma and pretelson, large lunate scales on the posterior carapace margin and a clavate telson. The opisthosoma shows both second and fourth order differentiation into a mesosoma and metasoma in the Hardieopteridae, with appendage V being spiniferous and VI being non-spiniferous as in '' Hardieopterus.'' The Kokomopteridae is only known from the

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

, the temporal range of the Hardieopteridae extends further to the

. Superfamily Kokomopteroidea Kjellesvig-Waering, 1966 * Family Kokomopteridae Kjellesvig-Waering, 1966 ** '' Kokomopterus'' Kjellesvig-Waering, 1966 ** '' Lamontopterus'' Waterston, 1979 * Family Hardieopteridae Tollerton, 1989 ** '' Hallipterus'' Kjellesvig-Waering, 1963 ** '' Hardieopterus'' Waterston, 1979 ** '' Tarsopterella'' Størmer, 1951

References

Stylonurina Silurian first appearances Devonian extinctions Arthropod superfamilies {{Eurypterid-stub