This mushroom substrate is called flat mushroom, scientific name sidearm.

Some places are called north wind mushroom, frozen mushroom, fungus, trumpet mushroom and so on. The acacia tree belongs to the broad-leaved species, and is able to be parasitized by most of the wood-rotting fungi, and is able to differentiate the fruiting body normally. However, if you are not able to determine the species of the substrate, it is recommended that you do not consume it, so as not to accidentally eat poisonous mushrooms poisoning.