Stenhammarella

Systematics

Historical taxonomy

This species was first formally described by the Swedish lichenologist Erik Acharius in 1810. He initially classified it in the genus Biatora. In his description of Biatora turgida, Acharius provided an account of the lichen's morphological features and emphasised the care required to correctly identify it. He noted that B. turgida grows on rocks in the mountain forests of Vallis Freniere, Switzerland, a location documented by the collector Johann Christoph Schleicher. Acharius described the lichen's crust as somewhat thick, slightly raised, and either white or ash-coloured. The apothecia (fruiting bodies) he noted to be relatively large, scattered and with a circular shape and swollen appearance. These structures are embedded in the crust, surrounded by a thick, black, and entire margin that is elevated above the crust's surface. The disc of the apothecia, which is depressed within this margin, is whitish or ash-coloured with a pruinose (powdery) texture. Acharius pointed out that, at first glance, the lichen might resemble species from other genera such as Lecidea, Gyalecta, or Urceolaria, but he cautioned against this misidentification.

A few years later in 1814, Acharius considered the taxon as a variety of Lecidea albocaerulescens. In the following decades, as different authors published differing opinions about its correct classification, it was shuffled to several different genera, or considered by some as a subtaxon of an existing species. In 1967, Hannes Hertel proposed the new monospecific genus Stenhammerella to contain the species. This arrangement has largely endured in subsequent overviews of fungal classification, although an alternate placement in the genus Porpidia was suggested in 2004.

Classification

The taxonomic placement of this species has evolved over time. Initially, it was considered as incertae sedis (of uncertain placement) within the class Lecanoromycetes, lacking a definitive familial assignment. However, subsequent genetic analyses have provided clarity, demonstrating that placement in the family Lecideaceae is appropriate. Further research has led to a refined understanding of its phylogenetic relationships. In one particular analysis, the species was found to occupy a position at the basal part of a clade containing several Porpidia species, suggesting a close evolutionary relationship with this genus.