Summary:
Atropellis piniphila is most easily differentiated from Atropellis pinicola by its spores. Features include growth on cankers of Ponderosa and lodgepole pine, the fruitbody first closed and rounded to ellipsoid, then expanding, 0.2-0.3cm across, brown to black, with leathery-membranaceous texture and a stem-like base, and microscopic characters, (Weir 1921). It attacks Pinus ponderosa and Pinus contorta between the ages of 5 and 25 years, the infection occurring usually at the nodes, less frequently on the internodes (but may spread throughout the length of the stem), and causes cankers on the surface. After further examination of Atropellis piniphila (Weir) M.L. Lohman & E.K. Cash and the type of Atropellis arizonica M.L. Lohman & E.K. Cash, the only feature that appeared to differ was the septation of the spores (0-1-septate for the former and 0-3-septate for the latter, not considered enough to define a new species in view of the small number of 3-septate spores examined), (Reid, J.).

Microscopic:
spores (14)16-28(32) x 4-7(8) microns, "elliptic-fusoid, with acute ends, straight or sigmoid, (0) to 1-septate (rarely becoming 3-septate)"; asci (85)90-160 microns, (Reid, J.), spores averaging 18.9 x 6.4 microns, oblong to elliptic or fusiform, ends acute, colorless, continuous, usually with a single central oil droplet (occasionally with two oil droplets), irregularly biseriate, sometimes uniseriate; asci 8-spored, averaging 135.8 x 14.1 microns, clavate, rounded at top, long-stemmed; paraphyses filamentous, branched, longer than the asci, colorless, (Weir)

Notes:
Collections of A. piniphila were examined from WA, ID, AB, MT, NM, and (the only collection corresponding to A. arizonica) AZ, (Reid, J.(2)). It causes considerable damage to Pinus contorta (lodgepole pine) in several areas of AB, BC, and the western United States (Hopkins(1)).

Synonyms and Alternate Names:
Atropellis arizonica M.L. Lohman & E.K. Cash
Cenangium piniphilum Weir
Clavaria bresadolae Quel.
Hericium bresadolae (Quel.) Malencon