When American ornithologist Alexander Wetmore described this species from subfossil remains which were found at Prosperous Bay, Saint Helena, he classified it into the new genus Aphanocrex.

While Olson had considered it as congener of the Inaccessible Island rail, other scientists regarded it not even as a close relative and so it is retained in Aphanocrex.

The Saint Helena rail was relatively large and reached almost the size of the New Zealand weka (Gallirallus australis).

Furthermore, it had strong toes with long claws, which gave that species a good ability to climb and flutter up the steep valley walls.

It fed probably on the eggs and the juveniles of several Saint Helena terrestrial and pelagic bird species and on snails.