D is for……..

Dicroidium
An extinct family of seed ferns (a group of plants somewhere between a fern and a cycad) that existed during the Triassic (about 200 million years ago).
Dicroidium are also known as fork leaved seed fern due to the fern like fronds having a obvious fork. Male and female plants were believed initially to be separate species.
They inhabited what was at the time the supercontinent Gondwana.