Historical taxonomy The family Pyrenulaceae was introduced by the German lichenologist
Gottlob Ludwig Rabenhorst in 1870 in his treatment of the , which he defined by their wart-like
fruiting bodies opening through a pore at the summit. His concept of the family was based on lichens with mostly immersed to emergent, usually hemispherical fruiting bodies enclosed by a dark wall, and he included the genera
Microthelia,
Acrocordia,
Arthopyrenia,
Leptorhaphis, and
Pyrenula. 's
Coloured Figures of English Fungi or Mushrooms (1800), illustrating the
basionym of
Pyrenula nitida, the
type species of the
type genus of Pyrenulaceae At the
ordinal level, Pyrenulaceae is placed in
Pyrenulales, a name first used by
Bruce Fink in 1915 and later validated by
Hawksworth and Eriksson in 1986. The ordinal placement of the family was debated through the 1980s and 1990s:
Richard Harris argued in 1989 that Pyrenulaceae belonged with non-lichenized families in Melanommatales rather than in a separate Pyrenulales, which he saw as preserving an artificial divide between lichenized and non-lichenized fungi, while Eriksson and Winka in 1997 kept the order provisionally separate from a broadly defined Dothideales pending better molecular sampling. Subsequent multigene phylogenetic studies resolved the question by placing Pyrenulales in the subclass Chaetothyriomycetidae within Eurotiomycetes, a position retained in current classifications. Harris's 1989 treatment showed that generic boundaries in Pyrenulaceae were already being reconsidered before
molecular data became available. In his account of the eastern North American flora, he accepted a narrower
Anthracothecium and reduced several previously recognized genera, including
Melanotheca,
Mycopyrenula,
Parmentaria,
Pleurotheliopsis, and
Pyrenastrum, to
synonymy under
Pyrenula. He argued that characters such as
ostiole orientation, ostiole fusion, and broad ascospore types had been overemphasized in older classifications and often produced artificial groupings. A major pre-molecular treatment of the family was
André Aptroot's 1991
monograph, which revised Pyrenulaceae largely through
cladistic analysis of
morphological characters. Reviewing the work in 1993, Ove Eriksson noted that Aptroot accepted eight genera in the family, including the newly proposed
Clypeopyrenis,
Distopyrenis,
Mazaediothecium, and
Pyrenowilmsia, but also emphasized that the group remained incompletely known and that molecular data would be needed to test and refine this classification. By the late 1990s, attempts to integrate lichenized and non-lichenized pyrenocarpous fungi were already reshaping ideas about Pyrenulaceae. In a 1998 review, André Aptroot argued that the traditional Pyrenulales, taken in a broad sense, probably formed a natural group and distinguished them from the Pleosporales by their heavily ascoma wall, which is typically composed of interwoven
hyphae (), rather than angular, jigsaw-like cells (). He also treated Pyrenulaceae as including both lichenized and secondarily non-lichenized elements, citing
Distopyrenis and the non-lichenized
Pyrenula coryli as examples of lineages that complicated older, more rigid distinctions between lichen and fungus classification.
Molecular phylogenetics of
North Carolina, showing its distinctive red, pseudostromatic ascomata Even before broad molecular sampling was available, limited phylogenetic evidence already suggested that
Anthracothecium,
Granulopyrenis, and
Pyrgillus might be nested within
Pyrenula as traditionally circumscribed, and that wider species sampling would be needed before the generic classification could be revised with confidence. The first molecular study focused specifically on the family, published in 2012, used three
molecular markers (
nrLSU,
mtSSU, and
ITS) and sequence data from 21 taxa. It recovered two strongly supported
lineages within the family and confirmed that
Pyrenula in its broad sense was not
monophyletic. Many characters traditionally used in generic classification—including ascospore colour and septation, structure, secondary chemistry, features, and
ostiole position—did not correspond well to these two groups, although
pseudocyphellae were confined to one of them. A 2013 species-level study illustrated this mismatch further: despite its bright red, , trypethelioid ascomata and unusual pigment chemistry,
Pyrenula sanguinea was placed within
Pyrenula as the
sister species of
P. cruenta. A more comprehensive three-gene phylogeny sampling 100 taxa, published in 2016, confirmed these results. Pyrenulaceae was strongly supported as
monophyletic, but
Pyrenula in its traditional sense was not:
Anthracothecium,
Lithothelium (itself non-monophyletic), and
Pyrgillus all proved to be nested within it. The analysis resolved two well-supported
clades—Group 1, characterized by the usual presence of thalline pseudocyphellae (with the notable exception of
Anthracothecium), and Group 2, which lacks them—with
Granulopyrenis seawardii tentatively placed as the earliest-diverging lineage. Because broad taxon and gene sampling remained incomplete, the authors stopped short of formal taxonomic changes but concluded that generic delimitation within the family will need substantial revision. ==Description==