Pachyascaceae
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''Pachyascus'' is the sole
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
in the family Pachyascaceae. It contains a single species, the
lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...
''Pachyascus lapponicus''. Both the genus and species were described as new to science in 1968 by lichenologists
Josef Poelt Josef Poelt was a botanist, bryologist and lichenologist. He held the chair in Systematic Botany and Plant Geography at the Free University of Berlin (1965 - 1972) and then was head of the Botanical Institute and Botanical Garden of Graz Universi ...
and
Hannes Hertel Hannes Hertel is a German lichenologist and taxonomist and was Director of the State Herbarium in Munich, Germany 1992–2004. His specialist areas are the fungi and lichens. Early life and education Hannes Hertel was born in 1939. His doctorat ...
. ''P. lapponicus'' was originally collected from Lapland, a province in northern Sweden. The lichen has several unusual characteristics: it grows exclusively along with the rock moss ''
Andreaea ''Andreaea'' is a genus of rock mosses described by Johann Hedwig in 1801. They are small, delicate acrocarpous mosses (meaning that the capsules are formed at the tips of vertical branches) that form dark brown or reddish cushions on wet silic ...
'', it bears goniocyst-like parts (goniocysts are small aggregations of
photobiont A lichen ( , ) is a hybrid colony of algae or cyanobacteria living symbiotically among filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualistic relationship.
cells surrounded by fungal
hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...
e) and produces tiny
apothecia An ascocarp, or ascoma (: ascomata), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. As ...
that stand in the leaf axils of the moss, and it has thick asci. Poelt and Hertel thought the species occupied a basal position in the order
Lecanorales The Lecanorales are an order of mostly lichen-forming fungi belonging to the class Lecanoromycetes in the division Ascomycota. The order contains 26 families, 269 genera, and 5695 species. Families Suborder Lecanorineae * Biatorellacea ...
, and Poelt tentatively placed it in its own family, Pachyascaceae in a 1974 publication. This family was formally published in 2001. In 2020, it was classed within the Lecanoromycetidae but within uncertain order placement. Another lichen, which bears a superficial resemblance in the ascomata, was once placed in ''Pachyascus'' as ''P. byssaceus'' ; it is now known as '' Vezdaea aestivalis''.


References

Lecanorales Lichen genera Monotypic Lecanorales genera Taxa described in 1968 Taxa named by Hannes Hertel Taxa named by Josef Poelt {{Lecanorales-stub