{{Short description|Species of tooth fungus}} {{Use dmy dates|date=April 2025}} {{Use Oxford spelling|date=April 2025}} {{Speciesbox | image = Hydnellum auratile 34144.jpg | taxon = Hydnellum auratile | authority = (Britzelm.) Maas Geest. (1959) | synonyms_ref = <ref name="urlFungorum synonymy: Hydnellum auratile"/> | synonyms = *''Hydnum auratile'' {{au|Britzelm. (1891)}} }}

'''''Hydnellum auratile''''' is a tooth fungus in the family Bankeraceae,<ref name="CoL_3MZDK"/> first described by the German mycologist Max Britzelmayr in 1891. The fungus produces distinctive orange to orange-brown fruit bodies with caps up to 5&nbsp;cm wide that fade to brown with age. It forms ectomycorrhizal associations with both coniferous and deciduous trees, particularly Scots pine and Norway spruce on calcareous soils. Though widely distributed across Europe, parts of Asia, Australia, and North America's Pacific Northwest, ''H.&nbsp;auratile'' is considered endangered in Switzerland.

==Taxonomy==

''Hydnellum auratile'' was first described as a species of ''Hydnum'' by German mycologist Max Britzelmayr in 1891.<ref name="Britzelmayr 1892"/> Rudolf Arnold Maas Geesteranus transferred it to ''Hydnellum'' in 1959.<ref name="Maas Geesteranus"/>

==Description==

The fruit bodies of ''Hydnellum auratile'' arise on a distinct stipe and bear a cap up to 5&nbsp;cm wide, occurring either singly or in crowded groups. Young caps are vivid orange to orange-brown, with a smooth to slightly scaly surface that feels velvety to the touch. As they mature, fine radial hairs develop and the centre often sinks slightly, creating a shallow, funnel-shaped profile. Concentric wrinkles may appear toward the margin, and the cap colour fades to a muted brownish tone. The flesh (context) is thin—usually no more than 2&nbsp;mm thick—and mirrors the cap's colour transition from bright orange to pale brown.<ref name="Ryvarden 2024"/>

The stipe reaches about 4&nbsp;cm in height and 1&nbsp;cm in width, matching the cap in colour and covered in a similar velvety, felt-like layer of hairs. Under the microscope, the fungus is built of hyphae 2.5–7&nbsp;μm wide, each separated by simple cross-walls (septa). Its spores are roughly spherical (subglobose), measuring 5–6 × 3.5–4.5&nbsp;μm, and are ornamented with tiny wart-like projections (tuberculate).<ref name="Ryvarden 2024"/> In mass, the spores are brown.<ref name="Dickson 2004"/>

The widespread ''Hydnellum aurantiacum'' is a close lookalike, but can be distinguished by having a white to buff cap, dull orange to brown flesh, and white spines.<ref name="Dickson 2004"/>

==Habitat and distribution==

The fungus is widely spread in Europe,<ref name="Dickson 2004"/> and has also been reported from the Pacific Northwest region of North America.<ref name="Ammirati 2009"/> It is considered endangered in Switzerland.<ref name="Senn-Irlet 2007"/> It forms associations with both coniferous and deciduous trees.<ref name="Ryvarden 2024"/> It predominantly occurs in calcareous forests, often under Scots pine (''Pinus sylvestris'') and Norway spruce (''Picea abies'') on soils derived from limestone, chalk or shell-rich substrates, forming ectomycorrhizal associations with these trees.<ref name="Hanssen & Gulden 2002"/> The species has a broad—but patchy—distribution across the temperate zone of Europe, with confirmed records from France, Italy, Germany, Austria, Switzerland, the Czech Republic, Slovakia, Denmark, Sweden and Finland.<ref name="Hanssen & Gulden 2002"/> Other regions outside Europe where it is known to occur include India, Japan, Australia.<ref name="Hanssen & Gulden 2002"/>

==References== {{Reflist|colwidth=30em|refs=

<ref name="Ammirati 2009">{{cite book |last1=Ammirati |first1=J. |last2=Trudell |first2=S. |title=Mushrooms of the Pacific Northwest |url=https://archive.org/details/mushroomspacific00trud_400 |url-access=limited |series=Timber Press Field Guides |publisher=Timber Press |location=Portland, Oregon |year=2009 |page=[https://archive.org/details/mushroomspacific00trud_400/page/n255 231] |isbn=978-0-88192-935-5}}</ref>

<ref name="Britzelmayr 1892">{{cite book |last=Britzelmayr |first=M. |title=Hymenomyceten aus Südbayern 11 (Theil VIII): Polyporei, Hydnei, Thelephorei, Clavariei und Tremellinei |publisher=R. Friedländer & Sohn |location=Berlin |page=14 |language=de}}</ref>

<ref name="CoL_3MZDK">{{Catalogue of Life |id=3MZDK |title=''Hydnellum auratile'' (Britzelm.) Maas Geest. |access-date=23 April 2025}}</ref>

<ref name="Dickson 2004">{{cite journal |last1=Dickson |first1=G. |last2=Emmett |first2=E. |title=''Hydnellum auratile'' at last |journal=Field Mycology |year=2004 |volume=5 |issue=2 |pages=49–51 |doi=10.1016/S1468-1641(10)60249-6 |doi-access=free}}</ref>

<ref name="Hanssen & Gulden 2002">{{cite journal |last1=Hanssen |first1=Even W. |last2=Gulden |first2=Gro |year=2002 |title=''Hydnellum auratile'' (Britzelm.) Maas Geest. – en ny jordboende piggsopp i Norge |trans-title=''Hydnellum auratile'' (Britzelm.) Maas Geest. – a new terrestrial tooth fungus in Norway |journal=Blyttia |volume=60 |pages=191–194}}</ref>

<ref name="Maas Geesteranus">{{cite journal |last=Maas Geesteranus |first=R.A. |title=Sur un ''Hydnellum'' méconnu |journal=Persoonia |year=1959 |volume=1 |issue=1 |pages=111–114 |url=http://www.cybertruffle.org.uk/cyberliber/61056/0001/001/0111.htm |language=fr}}</ref>

<ref name="Ryvarden 2024">{{cite book |last=Ryvarden |first=Leif |year=2024 |title=Hydnoid Genera – A World Synopsis |series=Synopsis Fungorum |volume=50 |publisher=Fungiflora |location=Oslo |url=https://www.fungiflora.no/synopsis-50-hydnoid-genera |page=29}}{{OA}}</ref>

<ref name="Senn-Irlet 2007">{{cite report |last1=Senn-Irlet |first1=B. |last2=Bieri |first2=G. |last3=Egli |first3=S. |title=Lista Rossa Macromiceti. Lista Rossa delle specie minacciate in Svizzera. UV-0718-I |year=2007 |location=Bern |publisher=Ufficio federale dell’ambiente |language=it |url=http://www.bafu.admin.ch/publikationen/publikation/00055/index.html?lang=fr&lang=it}}</ref>

<ref name="urlFungorum synonymy: Hydnellum auratile">{{cite web |title=GSD Species Synonymy: ''Hydnellum auratile'' (Britzelm.) Maas Geest. |url=http://www.speciesfungorum.org/GSD/GSDspecies.asp?RecordID=332079 |publisher=Species Fungorum. CAB International |access-date=23 April 2025}}</ref>

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{{Taxonbar|from=Q10434764}}

auratile Category:Fungi described in 1891 Category:Fungi of Australia Category:Fungi of India Category:Fungi of Japan Category:Fungi of Europe Category:Fungi of North America Category:Inedible fungi Category:Taxa named by Max Britzelmayr Category:Fungus species