Gallinula Brisson, 1760

Boles, Walter E., 2005, A New Flightless Gallinule (Aves: Rallidae: Gallinula) from the Oligo-Miocene of Riversleigh, Northwestern Queensland, Australia, Records of the Australian Museum 57 (2), pp. 179-190 : 181-182

Genus Gallinula Brisson, 1760

Gallinula Brisson, 1760 , Ornithologia sive Synopsis Methodica vol. 1, Paris: Ad Ripam Augustinorum [50], vol. 6[2]— type species: Gallinula Brisson = Fulica chloropus Linnaeus, 1758 .

Tribonyx has been distinguished from Gallinula by the shorter, heavier toes, longer tails, absence of white on the undertail coverts ( Olson, 1973a) and short, wide bills with very short premaxilla ( Olson, 1975a), all characters that cannot be assessed from the available fossil material. Osteological comparisons of a “typical” gallinule, G. tenebrosa , and two species of native-hens Gallinula (Tribonyx) , G. ventralis and G. mortierii , found few useful characters that might permit separation of skeletal elements to subgeneric level. In the humerus of Gallinula (Gallinula) , the proximal end of the condylus dorsalis extends over the condylus ventralis. Brodkorb (1967) used this character to distinguish Gallinula (s.s.) from Fulica , in which the ventral extent of the condylus dorsalis is less, just reaching the dorsal border of the condylus ventralis. The species of Gallinula (Tribonyx) are somewhat intermediate between typical Gallinula and Fulica in this character, with a shorter, but still overlapping ventral extent of the condylus ventralis. The condylus dorsalis on the one distal humeral fossil fragment is abraded and the state of this character is equivocal. In the tarsometatarsus of Gallinula (s.s.), the lateral border of the shaft is about even with that of the trochlea metatarsi IV and they thus join smoothly with little lateral flaring. In contrast, species of Gallinula (Tribonyx) have the trochlea metatarsi IV curving outwards laterally, away from the border of the shaft. This character cannot be evaluated for the fossil material. Until skull material is recovered, it cannot be ascertained with certainty whether the Riversleigh flightless rail was indeed a native-hen.

This taxon is here diagnosed only as Gallinula . In the following discussion, however, extensive reference and comparisons are made to native-hens Gallinula (Tribonyx) because these are the only gallinules in Australia and New Zealand in which flightlessness occurs and the only ones well represented in the fossil record.

Gallinula (s.l.) can be diagnosed on the material available by the following suite of characters.

Coracoid. The processus procoracoideus extends about half way along the shaft posteriorly, joining it gradually. The impressio m. sternocoracoidei is deeply excavated mediodistally, and has a rounded border to the facies articularis sternalis.

Humerus. The crista bicipitalis extends distally only ½– 2 ⁄ 3 as far as the crista deltopectoralis. The border of the epicondylus ventralis is concave (in anterior view). The proximal end of the condylus dorsalis extends over the proximal end of the condylus ventralis.

Carpometacarpus. The processus alularis is broad (in proximal view). The os metacarpale minus is somewhat curved proximally, less so distally, but overall more than in Fulica . The distoposterior corner of the symphysis metacarpalis distalis is obliquely angular, rather than square.

Femur. The junction of the impressiones obturatoriae and trochanter femoris forms an acute angle of c. 50°. The trochanter femoris is deep, flaring from the shaft both anteriorly and posteriorly (in lateral view). There is general agreement in the size and location of the impressiones iliotrochanteria. The condylus lateralis is well produced (in lateral view). The sulcus intercondylaris is situated near the midline of the element. The condylus medialis is moderately robust (in posterior view) and well produced posteriorly (in medial view).

Tibiotarsus. The impressio lig. collateralis medialis is deep. The crista fibularis is short. There is a deep U-shaped notch on the posterolateral margin of the area interarticularis. The crista cnemialis lateralis extends to a point well proximal to the proximal end of the crista fibularis. The crista cnemialis cranialis continues as a crest along the anterior medial edge of the shaft. The fossa retropatellaris is moderately deep. The anterior surface of the proximal end is slightly convex. The condylus lateralis extends far proximally, overlapping the distal 1 ⁄ 3 –½ of the pons supratendineus.

Tarsometatarsus. The hypotarsus extends distally, rather than being truncate (in posterior and lateral views). The shaft has roughly parallel sides throughout its length. The foramen vasculare distale is situated far distally. Other useful characters, which cannot be assessed on the fossil, are that the dorsal margin of the trochlea metatarsi II is roughly even with the plantar margin of the trochlea metatarsi III; the area proximal to the trochlea metatarsi III, medial to the foramen vasculare distale and lateral to the trochlea metatarsi II, is broad with parallel sides; and the incisura intertrochlearis lateralis is wide.