| Caia Temporal range: Late Silurian |
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|---|---|
| Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Plantae |
| Subkingdom: | Embryophyta |
| clade: | Polysporangiophyta |
| Class: | †Horneophytopsida |
| Genus: | †Caia Fanning et al. (1990)[1] |
| Species | |
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†C. langii Fanning et al. (1990)[1] |
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Caia is a genus of small fossil plants of Late Silurian age (around 420 million years ago). The diagnostic characters are naked parallel-sided axes branching isotomously, terminating in vertically elongate sporangia (spore-forming organs) which bear spinous emergences particularly at the distal ends. Spores are trilete and retusoid.[1] The only known species is from Hereford, England.
Cladistic analysis suggests that the genus may belong to the Horneophytopsida, a class of the polysporangiophytes, as it lacks vascular tissue and has branched stems bearing sporangia.[2] For the cladogram, see the Horneophytopsida article.