Ciao Salvatore,
in un vecchio articolo di Villarreal e Heykoop pubblicato su zeitschrift fur Mykologie (1964), gli AA. sinonimizzano le due specie dando la priorità a C. ochraceus.
Recentemente Li, Y.C.1,3, Yang, Z.L.1* and Tolgor. Fungal Diversity. (2009). Phylogenetic and biogeographic relationships of Chroogomphus species as inferred from molecular and morphological data.
Gli A.A., hanno revisionato il genere ma non nomunano assolutamente C. fulmineus se non nell'indice dove citano gli autori delll'articolo che mette in sinonimia le due specie:
Villarreal, M. and Heykoop, M. (1996). Chroogomphus ochraceus (Kauffman) O.K. Mill., the correct name for Chroogomphus fulmineus (R. Heim) Courtec. Zeitschrift für Mykologie 62: 205-212.
Non so se ci sono stati ulteriori sviluppi in merito, ma non me ne meraviglierei se ci fossero.
Ti copio-invollo la chiave parziale dei crogonfi tratta dalla monografia di Miller dove vengono espresse le differenze tra le due specie da te menzionate.
MONOGRAPH OF CHROOGOMPHUS (GOMPHIDIACEAE)
ORSON K. MILLER (1963)
CHROOGOMPHUS section CHROOGOMPHUS
Cuticle of pileus of somewhat appressed, gelatinized hyphae, but not forming a distinct gelatinous pellicle, merely viscid to the touch, no distinct gelatinous veil present.
Type: Chroogomphus rutilus ( Sch. ex Fr.) 0. K. Miller.
1. Cystidia thick-walled ...................................................... 2
2. Cuticular hyphae 6-7 11. in diam; spores up to 23 11. long; cystidia with somewhat thickened walls in their mid portion; distributed throughout North America .............................................. C. vinicolor
2. Cuticular hyphae 2-5 11. in diam ; spores not over 20 11. long; cystidia with more evenly thickened walls; southern United States and Jamaica ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. jamaicensis
1. Cystidia thin-walled ....................................................... 3
3. Spores 19-28 11. in length ...................................... C. flavipes
3. Spores 14-22 11. in length but never longer .............................. 4
4. Pileus dull colored, grayish, ochraceous, vinaceous to dingy vinaceous brown; stipe pale ochraceous, orange-huff to vinaceous red ..... . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. rutilus
4. Pileus bright colored, bright yellowish orange to bright ochraceous; stipe concolorous with pileus, becoming reddish to magenta near base ............................................... C. ochraceus