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Xanthoria aureola (Ach.) Erichsen
[invalid – ICBN art. 57.1]
 
(= Xanthoria ectaneoides (Nyl.) Zahlbr.)


Foliose, golden-yellow to orange, lacking isidia or soredia, closely resembling the common X. parietina but with narrow, elongated, strap-like lobes; apothecia sparse or more usually absent. Locally dominant on coastal rocks, also stated to occur inland on limestone rocks at higher altitudes.

Refs: Smith et al. (2009), 968; Purvis et al. (1992), 647 (as X. ectaneoides); Dobson (2005), 462 (photo, as X. ectaneoides); Dobson (2011), 471 (photo); Whelan (2011), 151 (photo).

X. parietina is also often abundant on coastal rocks and the two species are frequently confused. When they grow together, X. aureola is clearly distinct, though young thalli may be difficult to assign. Lobe tips of X. aureola are generally less than 2mm wide, but variation in X. parietina is such that measurements are often of little value in identification.

Nomenclatural note: this species is now considered to be the true Xanthoria aureola (Ach.) Erichsen and this name has been introduced in place of 'X. ectaneoides'. However, the name 'X. aureola' has a long history of widespread application to the species we now know as X. calcicola and an internet search quickly confirms continuing use of the name in that sense. Consequently, reapplication of 'X. aureola', even though presumably supported by examination of the original type, will cause considerable and long-lasting confusion and in my view is contrary to Article 57 of the International Code of Botanical Nomenclature. It would have been better for the name 'X. ectaneoides' to continue to be used for the taxon depicted here, and it is with extreme reluctance that I now follow Smith et al. (2009).

 
Xanthoria aureola (ectaneoides)
Coastal rockface, Arbroath, Angus, April 2002
 
Xanthoria aureola (ectaneoides), close-up
Xanthoria aureola (ectaneoides), with apothecia, close-up
Xanthoria aureola (ectaneoides), habitat
Coastal rocks, Kennedy's Pass, Ayrshire, May 2008 – barren and fertile thalli; habitat shot showing occurrence on supralittoral rocks with Ochrolechia parella, Tephromela atra, Anaptychia runcinata, Ramalina siliquosa, Grimma maritima, Armeria maritima, Festuca rubra subsp. pruinosa (the stiff, blue grass), etc.


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© A.J. Silverside
Uploaded August 2008, as X. ectaneoides, last updated November 2011 (first hosted at www-biol.paisley.ac.uk, January 2003, substantially extended)