Source: http://www.mycoguide.com/guide/fungi/basi/agar/poly/phan/hapa/rutilans
Timestamp: 2019-04-22 11:29:08+00:00

Document:
Poisonous. Contains polyporic acid. Causes abdominal pain, nausea, vomiting, and other symptoms, as well as purple discoloration of urine. Recovery may take a week.
tender nesting polypore, cinnamon bracket, purple dye polypore.
Epithet = getting ruddy color (warm red). Genus = tender pileus.
Annual, bracket sessile to effused reflexed. Cap surface and pores dull orange to cinnamon brown. KOH turns all parts violet. Flesh soft and fibrous, becoming light and somewhat brittle when dry. Pores angular, 2–4 per mm. Microscopic characters: monomitic, generative hyphae with clamps, branched and thick-walled in the context; cystidioles same size as basidia; spores elliptical, hyaline, thin-walled, 3.5–5 × 5–6.5 µm (Gilbertson and Ryvarden 1986).
Aurantiporus croceus is orange and larger, KOH turns reddish (not yet recorded here). Trametes cinnabarina (Pycnoporus) is bright red; Kuo reports: Cap surface purplish to reddish, then gray to black with KOH; pore surface olive green with KOH. Phellinus gilvus is darker brown, firm, with golden context, KOH turns black. Phaeolus schweinitzii is larger, forms rosettes, KOH turns black. Pycnoporellus alboluteus is orange, pores larger, on conifers; Kuo reports: All parts bright red with KOH [not recorded for Chicago area]. Fistulina hepatica has a meaty and mottled flesh and separate tubes.
Saprobe causing a white rot. Found on dead hardwood logs and branches. In Chicago Region found in oak woodland and hardwood forest but nearly absent from oak savanna. Found on conifers in Arizona.
Late June to early October. One record in April.
Circumglobal in temperate zone. Common in north-eastern North America and in Arizona. Less common in Gulf Coast states and rare in west.
Fairly common; widespread. Only one or a few found at a time. Three historic collections by W. S. Moffatt, as P. nidulans: 1902 Wheaton, 1903 Glen Ellyn, 1904 Winfield; one collection by E. T. Harper, as P. rutilans: 1902 Riverside. Listed in Moffatt (1909) for Elmhurst.
We have over 100 collections plus 50 observations since 1994.
Miettinen et al. (2016): FRANCE. Rhône: Rontalon, Bois des rivoires, N45.64575:E4.61808, alt. 622 m, Quercus petraea, 15 Aug 2008, Rivoire 3429 (LY*, neotype of Boletus rutilans designated here).
Boletus rutilans (1798) was transferred to Polyporus (1818), Inonotus (1882), Leptoporus (1886), Inodermus (1888), Polystictus (1913), Hemidiscia (1916), and Phaeolus (1925).
Polyporus nidulans (1821) was transferred to Boletus (1827), Inonotus (1881), Polystictus (1890), and Phaeolus (1900). There was also the illegitimate homonym Agaricus nidulans (Fr.) E.H.L. Krause (1933); non Agaricus nidulans Pers. 1798 (Phyllotopsis nidulans).
There is contention between two names and whether they are synonyms. Some authors, particularly in America, use the name Hapalopilus nidulans. Others use Hapalopilus rutilans. Index Fungorum did not consider them synonyms (Aug 2014) but now has them as synonyms with H. rutilans as current (Apr 2017). Contrary to this, MycoBank treated them as synonyms with H. rutilans as the current name (Oct 2015), but now (April 2017) does not have them as synonyms (why?). Mycobank and Index Fungorum do not agree on heterotypic synonyms. Regarding H. nidulans, Mycobank gives Remarks : Fries (1821) referred to Boletus versicolor Schaeffer, pl. 136, which may be Boletus pinicola Swartz, but in 1838 (: 455) to Bulliard, pl. 482, which is Polyporus nidulans Fries as now understood.
Here are my thoughts on using H. rutilans. The basionym Boletus rutilans (1798) is earlier than Polyporus nidulans (1821). That is the fact in support of the epithet rutilans having priority. I think Mycobank is in error by listing the Fries 1818 Observationes mycologicae work as sanctioning the name. That is not listed as a sanctioning work by the International Code of Nomenclature, see 13.1(d). Later both names were sanctioned by Fries in 1821. A possible argument for using P. nidulans is that Fries listed that name on the page prior to P. rutilans and indicated that P. rutilans might be a variety of P. nidulans; Mycobank states that this means P. rutilans is not sanctioned against P. nidulans. But see Example 5 below that negates this idea. Also, the fact that P. nidulans was combined into Hapalopilus earlier has no bearing on priority.
Both names are sanctioned. Neither has been conserved or rejected (that I can find). So we apply the applicable rules in the code: 15.4; 11.4.
15.4. When, for a taxon in a rank lower than genus, two or more sanctioned names and/or two or more names with the same final epithet and type as a sanctioned name compete, Art. 11.4 governs the choice of the correct name.
Note 1. The date of sanctioning does not affect the date of valid publication, and thus priority (Art. 11), of a sanctioned name. In particular, when two or more homonyms are sanctioned only the earliest of them may be used, the later being illegitimate under Art. 53.2.
Ex.5. Fries (Syst. Mycol. 1: 41. 1821) accepted Agaricus flavovirens Pers. (1793), treating A. equestris L. (1753) as a synonym. Later (Elench. Fung. 1: 6. 1828) he stated “Nomen prius et aptius arte restituendum” and accepted A. equestris. Both names are sanctioned, but when they are considered synonyms A. equestris, having priority, is to be used.
11.4. For any taxon below the rank of genus, the correct name is the combination of the final epithet of the earliest legitimate name of the taxon in the same rank, with the correct name of the genus or species to which it is assigned, except (a) in cases of limitation of priority under Art. 14, 15, 56, or 57, or (b) if the resulting combination could not be validly published under Art. 32.1(c) or would be illegitimate under Art. 53, or (c) if Art. 11.7, 22.1 or 26.1 rules that a different combination be used.
So if we consider these two names to be synonymous and we apply the rules then the winner is Hapalopilus rutilans. The species epithet rutilans is the final epithet of the earliest legitimate name of the taxon in the same rank and Hapalopilus is the correct name of the genus ... to which it is assigned .
I updated this web page on 2017 April 22, adding article 15.4 and changes on Index Fungorum and Mycobank (previous version was 2015 October 01), after finding that the Wikipedia page for Hapalopilus nidulans cited my web page and discussion of competing names. The Wikipedia page said: As of November 2015, both MycoBank and Species Fungorum give H. rutilans and H. nidulans as synonymous, with the latter being the preferred name. That is no longer the case (Apr 2017).

References: Art. 11
 Art. 53
 Art. 14
 Art. 32
 Art. 53
 Art. 11