Mucronella is a genus the dates all the way back to Elias Magnus Fries (1874), the "Linnaeus of Mycology", who did some of the most influential early work on fungi from a taxonomic perspective. He shares this demi-god status with the Dutch mycologist Christiaan Hendrik Persoon who was by in far the first mycologist to publish a book specifically on Clavarioid fungi way before it was cool (Persoon 1797)! Fries circumscribed the genus for pendant, unbranched spines without any underlying subiculum. This concept has held up surprisingly consistently compare with other generic concepts from the same period in mycology with only a few species moving in and out over the last century and a half.

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Species are scattered to densely aggregated (but still typically discrete and evenly spaced), individual spines handing pendant from wood or occasionally decaying polypores. They range in size from a couple hundred microns to a centimeter long and are not often collected though perhaps just often overlooked. Most are relatively whitish but there are a few with yellow to orange tones.

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They are quite unique in the family being the only group with positively geotropic fruiting bodies. This leads to a couple interesting thoughts where one could ascribe this trait to the common ancestor of the family (this does seem to be the earliest diverging lineage) where at some point a reversal of geotropism occurred which was, by comparing species diversity, a very successful accident. This theory smells of an outdated sense of ascendant evolution however, and there is no more evidence for this than the theory the Mucronellae are just very tired or lazy small clubs that found it easier to grow with the flow, bro.

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While originally associated with hydnoid fungi as possibly a highly reduced state lacking any kind of pileus, Corner (1950, also Hennings and Lloyd) correctly surmised their close relationship with other clavarioid fungi, coming shockingly close by suggesting an affinity with Ceratellopsis, also in the Clavariaceae.  His detailed and careful study on fruiting body development helped inform this ultimately correct theory and is likely still to this day the most thorough developmental work done to date (spend some time taking in his amazingly detailed and beautiful microscopic drawings if you ever get the chance). While noting the affinity with clavarioid fungi, he placed it in his family Hericeaceae, primarily due to the amyloid spores. It is unique in the Clavariaceae in this character.

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Very recently, modern collections of a North American species of Gloeomucro have been found and sequenced. They appear to be close to Mucronella upon preliminary analysis and are included here as there is nowhere else to put it right now.

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Mucronellae are likely circumglobal in distribution with "M. calva" having been reported from all over the world in just about every continent and climate but such reports relied on gross morphology (tiny white spines) without much further investigation. Interestingly, based on ITS similarity and the caveats therein, there appears to be support for multiple trans-north-Atlantic and trans-south-Pacific species distributions

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I would venture to say nearly no species are very clearly known at present but the most recognizable (or at least commonly used names) are the Northern species M. calva, M. flava, and M. bresadolae/alba/fusiform (see below) and the beautiful Australia/New Zealand species M. pendula.