Amaurornis Reichenbach, Nat. Syst. Vog., p. 21 (1852).
Type by orig. desig., Gallinula olivacea Meyer.
The genus Amaurornis differs from Porzana and Gallinula in its more rounded wing, the third quill being longest, the second equal to the fifth or sixth and the first much shorter; the bill is short, about two-thirds the length of the tarsus, which is shorter than the middle toe with claw. In shape the bill varies somewhat. In A. olivaceus and A. phaenicurus the base is rather swollen but not so in the other species; on the other hand, although A. phaenicurus differs from the other species considerably in type and colour of plumage, A. olivaceus forms in this respect a link between them. If we place A. akool and A. bicolor with A, fuscus in the genus Limnobaenus, it would seem only consistent to place A. phaenicurus in Reichenbach's genus Erythra. Under the circumstances I retain them all under the one genus Amaurornis.
Key to Species.
A. Breast grey or rufous; bill not swollen at base.
a. Breast in adults vinous-chestnut, dark olive in the young…………A. fuscus, p. 19.
b. Breast dark grey.
a1. Back rufous-brown …………A. bicolor, p. 26.
b1. Back dark olive. …………A. akool, p. 25.
B. Breast white; bill swollen at base…………A. phaenicurus, p. 23