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NUMBER 89 23
FIGURE 9.—Fossils of the Reunion Rail, Dryolimnas augusti, new species, from Caverne de la Tortue: a, right
tarsometatarsus, holotype, CT 13, anterior view; b, left tarsometatarsus, holotype, CT 14, posterior view; c, right
humerus, proximal part, paratype, CT 4, anconal view; d, right ulna, paratype, CT 6, palmar view; e, same, internal
view;/ proximal part and shaft of left femur, paratype, CT 7, posterior view; g, distal part and shaft of right
femur, paratype, CT 9, posterior view; h, same, anterior view; i, right tibiotarsus, paratype, CT 11, proximal
view;/ left coracoid, shaft, paratype, CT 3, posterior view. All figures x 1.5.
tarsi, but it was present, as in D. cuvieri. It also is present in
Gallirallus australis (Sparrman), whereas it is absent in Aphanapteryx
and Erythromachus. On the internal side of the hypotarsus
there are three ridges and two open grooves, as in Dryolimnas,
Aphanapteryx, and Erythromachus, whereas in
Gallinula and Fulica, for example, the most internal groove is
closed.
The accurate lengths of the pectoral and wing bones are unknown,
but the proportions of the wing bones compared to
those of the leg bones are similar to those of the subspecies D.
cuvieri aldabranus, so it is likely that the Reunion Rail also
was flightless. This hypothesis is corroborated by the robustness
of the tarsometatarsus.
The modem species Lewinia pectoralis (Temminck) is considered
by Olson (1973) to belong to the genus Dryolimnas.
The Reunion form differs from it by its much larger size.
COMPARISON WITH FOSSIL FORMS.—For the extinct rail of
Rodrigues, Milne-Edwards (1874) created the genus Erythromachus
as distinct from the extinct genus Aphanapteryx of
Mauritius. Gunther and Newton (1879) transferred the Rodrigues
species to Aphanapteryx and were followed by Olson
(1977), who, however, indicated that these two species have
numerous differences in their osteology as well as in their
plumage, which is known from historical accounts. Piveteau
(1945) had already mentioned strong differences in the cranial
morphology.
The main osteological differences between Aphanapteryx
bonasia (Selys-Longchamps), from Mauritius, and Erythromachus
leguati Milne-Edwards, from Rodrigues, are as follows.
In Aphanapteryx the skull is narrower and longer, the temporal
fossae are deeper, and the nostrils are shorter and higher (Olson,
1977). On the sternum, the sternal carina is much lower,
and the gap between the coracoidal facets is much wider. The
humems is longer, its shaft is more incurved, and its bicipital
surface is proportionally shorter, whereas in Erythromachus
the humeral shaft is straighten The carpometacarpus is unknown
because the bone illustrated by Gunther and Newton
(1879, pl. 43: fig. G), and referred to E. leguati, does not belong
to the Rallidae. The femur is elongated and anteroposteriorly
incurved in Aphanapteryx but is shorter and stouter in
Erythromachus. The tarsometatarsus is proportionally more robust,
and its trochleae are less splayed in Erythromachus,
whereas in Aphanapteryx the shaft of the tarsometatarsus is
proportionally narrower, and the trochleae are more splayed,
particularly the internal trochlea. For these reasons we consider
the rails of Mauritius and Rodrigues to be two different genera.
The Reunion Rail differs from Aphanapteryx by the shape of
the tarsometatarsus, which is stouter, with proportionally nar-