Cryptothallus is a genus of liverworts in the family Aneuraceae. The plants are small, and are white to pale green as a result of lacking chlorophyll. The morphology of Cryptothallus is very similar to that of Aneura. As a result, Renzaglia, has suggested it may be considered "merely as an achlorophyllous species of Aneura." Wickett and Goffinet have argued the same position on the basis of sequences of nuclear, mitochondrial, and plastid DNA.
Species of Cryptothallus are subterranean myco-heterotrophs that obtain their nutrients from the ectomycorrhizal fungi growing among their tissues rather than from photosynthesis. It is the only genus of bryophyte known with this combination of characteristics. The infecting fungus is a basidiomycete, which is also the case in fungi associated with the related genera Aneura and Riccardia. However, this is not the case for other members of the Metzgeriales that have been studied.
There are two species known for the genus. Cryptothallus mirabilis is entirely white, and grows in bogs near birch trees. It was first described as a separate genus in 1933, and has been found in locations across northern Europe, and once in Greenland. The second species, Cryptothallus hirsutus was discovered in 1977 in Costa Rica, and first published as a new species in 1996.
- Malmborg, S. von (1933). "Cryptothallus nov. gen. Ein saprophytisches Lebermoos". Annales Bryologici. 6: 122–123.
- Crum, Howard; James Bruce (1996). "A new species of Cryptothallus from Costa Rica". The Bryologist. 99 (4): 433–438. doi:10.2307/3244107. JSTOR 3244107.
- Renzaglia, Karen S. (1982). A comparative developmental investigation of the gametophyte generation in the Metzgeriales (Hepatophyta). Bryophytorum Bibliotheca. 24. Vaduz: J. Cramer.
- Wickett, N. J.; B. Goffinet (2008). "Origin and relationships of the myco-heterotrophic liverwort Cryptothallus mirabilis Malmb. (Metzgeriales, Marchantiophyta)". Botanical Journal of the Linnean Society. 156 (1): 1–12. doi:10.1111/j.1095-8339.2007.00743.x.
- Schofield, W. B. (1985). Introduction to Bryology. New York: Macmillan. pp. 184, 192. ISBN 0-02-949660-8.
- Schuster, Rudolf M. (1992). The Hepaticae and Anthocerotae of North America. V. Chicago: Field Museum of Natural History. pp. 574–579. ISBN 0-914868-20-9.
- Hill, David Jackson (1969). "The absence of chlorophyll in the spores of Cryptothallus mirabilis Malmb". Transactions of the British Bryological Society. 5 (4): 818–819. doi:10.1179/006813869804146781.
- Huldremossa Aneura mirabilis (Cryptothallus mirabilis), a short article (in Swedish) with color photographs