Fur. A pelt that was not there at dusk.

There is no time to grow a mammalian pelt. What appears is piloerection plus a LERV-activated follicle programme that forces existing hair and a burst of keratin shaft into a dense, erect, oil-slicked covering. Sebaceous output surges with it. The result reads, at distance and in poor light, as fur. It is a pseudo-coat: thermoregulatory, abrasive, and gone by the second dawn when the shafts break and the erector muscles stand down.

Dark-DNA follicle genes — archived mammalian programmes still sitting in the genome — are the plausible substrate. The shift does not invent keratin. It unshelves it.