Caddoidea
Banks, 1893
Caddoidea is a small superfamily of () within the suborder Eupnoi, established by Nathan Banks in 1893. It contains two : Caddidae and Acropsopilionidae. Members are characterized by distinctive morphological features including relatively long legs and compact bodies. The group has a disjunct distribution with representatives in North America, eastern Asia, and Australia. Caddoidea represents one of the more specialized lineages within the Dyspnoi-Eupnoi clade of long-legged harvestmen.
Pronunciation
How to pronounce Caddoidea: //kæˈdɔɪdiə//
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Identification
Distinguished from other Eupnoi superfamilies by the combination of: tarsal formula and structure; presence of specific glandular openings on the body; and detailed of the penis, particularly the arrangement of . Acropsopilionidae (Australian) and Caddidae (Holarctic) differ in structure and leg proportions. The superfamily is most readily identified by examining male under microscopy.
Images
Habitat
Moist forest environments, particularly in leaf litter, under bark, and in rocky crevices. Some associated with caves or deep soil . Strong preference for stable, humid microhabitats with abundant decaying matter.
Distribution
Disjunct distribution: Caddidae occurs in eastern North America and eastern Asia (Japan, Korea, China); Acropsopilionidae is restricted to Australia (Queensland, New South Wales).
Ecological Role
Presumed and scavengers in forest floor and subterranean ; specific ecological functions poorly documented due to rarity and cryptic habits.
Human Relevance
No direct economic or medical significance; of interest to arachnologists studying and due to the group's disjunct distribution pattern.
Similar Taxa
- PhalangioideaAlso within Eupnoi but distinguished by different tarsal structure, penis , and generally more uniform global distribution; Phalangioidea contains the vast majority of familiar long-legged .
- IschyropsalidoideaAnother Eupnoi superfamily with enlarged , but differs in body proportions, tarsal formula, and lacks the specialized penis arrangement of Caddoidea.
More Details
Phylogenetic significance
Caddoidea is considered a relictual group whose disjunct distribution (eastern North America + eastern Asia + Australia) reflects ancient vicariance patterns, possibly dating to the Mesozoic breakup of Laurasia and Gondwana. The Australian Acropsopilionidae was historically placed in its own superfamily but molecular and morphological evidence supports its placement within Caddoidea.
Taxonomic history
The superfamily has remained stable since Banks' 1893 establishment, though -level composition has changed with the inclusion of Acropsopilionidae. The group was long considered closely related to Ischyropsalidoidea, but recent phylogenomic studies suggest a more position within Eupnoi.