How are Obregonia and  Trichodiadema different from each other?
Obregonia Obregonia, the artichoke cactus, is a genus of cacti with a single species, Obregonia denegrii. The species is endemic to the state of Tamaulipas in Mexico.
Erioderma Erioderma is a genus of lichenized fungi in the family Pannariaceae. They are commonly called mouse ears or felt lichens, and are small, pale brown to olive-brown foliose cyanolichens with a fuzzy upper surface that have the cyanobacteria "Scytonema" as their photobiont. Most species are found in the tropics of Central and South America, although three species are found in coastal regions of North America where they generally grow on mossy branches in humid sites. All North American species are rare, and two of them, "Erioderma mollissimum" and "Erioderma pedicellatum", are listed as endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). "Erioderma pedicellatum" is also listed as critically endangered on the IUCN Red List of Threatened Species. Species of "Erioderma" can resemble "Pannaria", "Leioderma", or small "Peltigera", but their fuzzy upper surface and lack of veins on their lower surface distinguishes them from these lichens.