Hermit crab on physical characteristics, genetic information, and combined data, support the longstanding hypothesis that the king crabs in the family Lithodidae are derived hermit crabs and should be classified as a family within Paguroidea. Other researchers have challenged this, asserting that the Lithodidae (king crabs) should be placed with the Hapalogastridae in a separate superfamily Lithodoidea. Six families are formally recognized in the superfamily Paguroidea, containing around 1100 species in total in 120 genera. The fossil record of "in situ" hermit crabs using gastropod shells stretches back to the Late Cretaceous. Before that time, at least some hermit crabs used ammonites'
Hermit (hummingbird) very decurved bills. Many species, including the rufous-breasted hermit, also use the heliconias for nesting, attaching their conical nest to the underside of one of the plant's broad leaves. The taxonomy of some groups has changed significantly in recent years. Apart from those issues discussed at "Phaethornis", a taxonomic problem occurs with the "Threnetes leucurus"/"T. niger" complex. Schuchmann & Hinkelmann (1999) considered the sooty barbthroat a melanistic variant of the "T. leucurus", but as it was described first, its scientific name was adopted for the entire species; pale-tailed barbthroat ("T. niger"). This, however, has not been accepted by all authorities,