Atriaecarpum venablesi was an early Eocene member of the moonseed family known from the hard inner stone of its fruit. As in other Menispermaceae, the endocarp protected the seed and preserves far more reliably than the softer outer fruit tissues. The family today is dominated by climbing plants, so a climbing habit is plausible, but no attached London Clay stems or leaves demonstrate this directly.

The fruit stone is unusually straight and compressed for a menisperm, with no internal condyle or plate. Its ventral face carries a strong longitudinal ridge with a hollow on either side. The same species has also been recognised in other earliest Eocene European floras, showing that this distinctive fruit type was not confined to the London Basin.