Spintharus

Hentz, 1850

Spintharus is a of cobweb (Theridiidae: Argyrodinae) established by Nicholas Marcellus Hentz in 1850. The genus ranges from the northeastern United States to Brazil, with the highest diversity in the Caribbean. A 2018 revision by Agnarsson and colleagues described fifteen new , many named after celebrities and public figures, making Spintharus notable for having the most species named after celebrities of any spider genus. Molecular evidence indicates that what was historically considered a single widespread species, S. flavidus, actually represents a 30 million year old radiation of at least 16 short-range species in the Caribbean region.

Spintharus flavidus by (c) Judy Gallagher, some rights reserved (CC BY). Used under a CC-BY license.

Spintharus by (c) jfox16, some rights reserved (CC BY), uploaded by jfox16. Used under a CC-BY license.

Spintharus by no rights reserved, uploaded by Lyn Roueche. Used under a CC0 license.

Pronunciation

How to pronounce Spintharus: //ˈspɪnθərəs//

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Identification

Spintharus can be distinguished from the similar Argyrodes by having two in place of a . It closely resembles Thwaitesia and Episinus in general . Specimens of S. flavidus show structural variability, with some individuals possessing an elevated region or humps on the . Females of S. gracilis measure 3.7 mm, males 2.3 mm.

Images

Habitat

Leaf litter or undersides of low-level leaves; somewhat cryptic microhabitats.

Distribution

Northeastern United States through Central America to Brazil, with exceptional diversity in the Caribbean (Cuba, Dominican Republic, Puerto Rico, Jamaica, Lesser Antilles). Caribbean are predominantly short-range or single island endemics rather than widespread.

Behavior

Ballooning (aerial on threads) has been observed but appears to be short-distance dispersal only. Limited overwater dispersal ability is inferred from phylogeographic patterns and island .

Human Relevance

Subject of notable taxonomic interest due to celebrity-named (e.g., S. barackobamai, S. berniesandersi, S. davidbowiei, S. leonardodicaprioi, S. michelleobamaae). As of 2017, Spintharus held the record for most species named after celebrities in any .

Similar Taxa

ThwaitesiaVery similar in general ; both belong to Argyrodinae and share reduced body forms typical of the .
EpisinusSimilar overall appearance; both are small theridiids with comparable body plans.
ArgyrodesDiffers in having a with two rather than the single colulus structure found in Argyrodes; this is a diagnostic character.
NeospintharusDistinguished by much higher and differences in size and position; Neospintharus has a more elevated than Spintharus.

Misconceptions

The widespread S. flavidus was historically considered a single capable of frequent overwater throughout the Caribbean. Molecular phylogenetic analysis has rejected this hypothesis, demonstrating instead that S. flavidus represents a 30 million year old radiation of at least 16 species, nearly all being short-range with limited dispersal ability.

More Details

Taxonomic History

Originally with S. flavidus (1850). Herbert Walter Levi recognized two (S. flavidus and S. gracilis) in an earlier revision. The 2018 revision by Agnarsson and colleagues added 15 new species, removed S. argenteus, and revealed extensive cryptic diversity in the Caribbean. A fossil species, †S. longisoma, is known from Dominican amber (Wunderlich, 1988).

Biogeographic Significance

The Spintharus radiation provides preliminary support for the GAARLandia landbridge hypothesis, with evidence for a single of the Caribbean approximately 30 million years ago coinciding with this contested geological event.