Donk also noted that Bankeraceae species lacked clamp connections. When clamp connections were discovered in "Phellodon fibulatus" and tuberculate spore ornamentation (the presence of small nodules on the spores) was found in "P. niger", Kenneth Harrison thought the family Bankeraceae was superfluous, and placed "Phellodon" and "Bankera" in the family Hydnaceae. This taxonomic rearrangement was rejected by Rudolph Arnold Maas Geesteranus in 1974, who showed that the tuberculate spores of "P. niger" were the result of an immature specimen. Richard Baird and Saeed Khan investigated spore ornamentation in North American "Phellodon" species using scanning electron microscopy, and rejected the placement of "Phellodon" in the Bankeraceae, preferring to leave it and "Bankera" in the Hydnaceae. Modern molecular phylogenetic analysis places "Phellodon" in the thelephoroid clade (roughly equivalent to the order Thelephorales) along with the related genera "Bankera", "Hydnellum", and "Sarcodon". Although the status of the Bankeraceae has not been fully clarified with molecular genetic techniques, "Phellodon" is classified in this family by authorities on fungal taxonomy. The generic name is derived from "phell"-, meaning "cork", and -"don", meaning "tooth". In North America, "Phellodon" species are commonly known as "cork hydnums". The British Mycological Society, in their recommended list of common names for fungi in the United Kingdom, name "Phellodon" species in the form "descriptor word" plus "tooth": fused tooth ("P. confluens"), grey tooth ("P. melaleucus"), black tooth ("P. niger"), and woolly tooth ("P. tomentosus"). The fruit bodies of "Phellodon" species have caps and stipe, and thus fall into the general category "stipitate hydnoid fungi". The cap surfaces are initially velvety to tomentose, eventually becoming matted. The surface is rough, with pits and ridges, and sometimes with concentrical zones of color or texture. The color can vary considerably, from cream to yellowish, brownish, greenish, greyish or black. Neighboring fruitbodies can fuse together, forming intertwined caps and partially fused stipes.