Ralloidea Finfoots and Rails

The Rallidae are most closely related to the Heliornithidae (Cracraft et al. 2004; Ericson et al. 2006; Fain et al. 2007), and an analysis by Hackett et al. (2008) even showed them to be paraphyletic with respect to the latter. Extant rails are globally distributed and include ecologically diversified taxa, such a crakes (Crex, Porzana) and coots (Fulica). As an adaptation to their habitat, mainly dense clutter of reeds, they have a mediolaterally compressed body, which is reflected osteologically by a very narrow sternum and pelvis. The three modern species of the Heliornithidae are

Eagle Umerus Anatomy

Fig. 9.3 Selected skeletal elements of Walbeckornis creber Mayr, 2007 from the late Paleocene of Walbeck in Germany. a Right coracoid (Institut für Geologische Wissenschaften of MartinLuther-Universität Halle-Wittenberg, Halle/Saale, Germany, IGWuG WAL39.2007); b right humerus (IGWuG WAL102.2007); c left carpometacarpus (IGWuG WAL221.2007); d distal left humerus (IGWuG WAL162.2007); e right femur (IGWuG WAL372.2007); f left tibiotarsus (IGWuG WAL385.2007); g distal left tibiotarsus (IGWuG WAL390.2007); h right tarsometatarsus (holotype, IGWuG WAL472.2007). Specimens coated with ammonium chloride. AH images to scale. (Photos by Sven Tränkner)

Fig. 9.3 Selected skeletal elements of Walbeckornis creber Mayr, 2007 from the late Paleocene of Walbeck in Germany. a Right coracoid (Institut für Geologische Wissenschaften of MartinLuther-Universität Halle-Wittenberg, Halle/Saale, Germany, IGWuG WAL39.2007); b right humerus (IGWuG WAL102.2007); c left carpometacarpus (IGWuG WAL221.2007); d distal left humerus (IGWuG WAL162.2007); e right femur (IGWuG WAL372.2007); f left tibiotarsus (IGWuG WAL385.2007); g distal left tibiotarsus (IGWuG WAL390.2007); h right tarsometatarsus (holotype, IGWuG WAL472.2007). Specimens coated with ammonium chloride. AH images to scale. (Photos by Sven Tränkner)

foot-propelled aquatic birds, which occur in Africa south of the Sahara and in the tropical areas of South America/Central America and Asia.

Finfoots have no Paleogene fossil record, and the earliest specimen is from the middle Miocene of North America (Olson 2003). Although many early Paleogene fossils were identified as rails, virtually all of these consist of very fragmentary or poorly preserved fossils. Without further material and before detailed comparisons with, for example, the Messelornithidae have been performed, they are of indeterminate affinities. In particular, this is true for several species of putative Rallidae from early and middle Eocene deposits of North America and England (Olson 1977b; Harrison and Walker 1979b; Harrison 1984a). The same applies to Ibidopsis hordwelliensis Lydekker, 1891 from the late Eocene (MP 17; Mlíkovsky 2002) of England, which was classified into the Rallidae by Harrison and Walker (1976a). This fairly large species is known from an incomplete coracoid and a distal tibiotarsus (Fig. 9.4). Although it seems to be a representative of the "core-Gruiformes," its assignment to the Rallidae is weakly based, and the coracoid likewise resembles the corresponding bone of the Messelornithidae (Sect. 9.1) and Parvigruidae (Sect. 9.3.1)

Quercyrallus arenarius (Milne-Edwards, 1892) and "Quercyrallus" quercy Cracraft, 1973 are represented by incomplete humeri from unknown horizons of the Quercy fissure fillings and are of uncertain affinities, just as "Rallus" adelus

Fig. 9.4 a Left coracoid of Geranopsis hastingsiae Lydekker, 1891 from the late Eocene of England (Natural History Museum, London, UK, BMNH A 30331); b left coracoid of a Psophia-like bird from an unknown locality of the Quercy fissure fillings in France (Muséum National d'Histoire Naturelle, Paris, France, MNHN QU 16929); c left coracoid of the extant Grey-winged Trumpeter, Psophia crepitans (Psophiidae); d referred right coracoid of Ibidopsis hordwelliensis Lydekker, 1891 (BMNH A 30329); e distal right tibiotarsus (holotype, BMNH A 36793) of I. hordwelliensis from the late Eocene of England. pne pneumatic opening. All images to scale. (Photos by Sven Tränkner)

Fig. 9.4 a Left coracoid of Geranopsis hastingsiae Lydekker, 1891 from the late Eocene of England (Natural History Museum, London, UK, BMNH A 30331); b left coracoid of a Psophia-like bird from an unknown locality of the Quercy fissure fillings in France (Muséum National d'Histoire Naturelle, Paris, France, MNHN QU 16929); c left coracoid of the extant Grey-winged Trumpeter, Psophia crepitans (Psophiidae); d referred right coracoid of Ibidopsis hordwelliensis Lydekker, 1891 (BMNH A 30329); e distal right tibiotarsus (holotype, BMNH A 36793) of I. hordwelliensis from the late Eocene of England. pne pneumatic opening. All images to scale. (Photos by Sven Tränkner)

Oberholser, 1917 (="Quercyrallus ludianus" Brodkorb, 1963) from the late Eocene of the Paris Gypsum, a long-beaked species which is based on an incomplete and poorly preserved skeleton (Cracraft 1973a; Olson 1977b). "Quercyrallus dasypus" (Milne-Edwards, 1892) was synonymized with the galliform Palaeortyx gallica by Mourer-Chauvire (1992a). Megagallinula harundinea Kurochkin, 1968 (proximal ulna) from the late Oligocene (Indricotherium Beds) of Kazakhstan (Kurochkin 1968a) and Palaeorallus alienus Kurochkin, 1968 (distal tibiotarsus) from the "middle" Oligocene of Mongolia (Kurochkin 1968b) were excluded from the Rallidae by Cracraft (1973a).

Songzia heidangkouensis Hou, 1990 from the early Eocene of Songzi County (Hubei Province) of China is known from a partial skeleton, consisting of the skull, both hindlimbs, and an incomplete wing, and was classified in the mono-typic taxon Songziidae (Hou 1990). Although the specimen is rather poorly preserved, its proportions are rail-like, and a close relationship to the Rallidae was also assumed by Hou (1990). In particular, the tarsometatarsus of this small species is long and slender, the ulna is short, and the hallux and other toes are very long (Hou 2003). Nevertheless, proportions are a weak indicator of relationships of an Eocene bird, and the holotype specimen would certainly benefit from further preparation.

Accordingly, the earliest well-represented Rallidae are two species of Belgirallus, B. oligocaenus Mayr and Smith, 2001 and B. minutus Mayr and Smith, 2001, which are based on diagnostic postcranial bones from the earliest Oligocene of Belgium (MP 21). A partial skeleton of a rail from the early Oligocene of Germany corresponds well with B. oligocaenus in size and morphology (Mayr 2006c). This specimen is from a medium-sized species, about the size of the extant Water Rail, Rallus aquaticus, and closely resembles extant rails in its osteological features. The elongated toes allow an assignment to the Rallinae (all Rallidae except the African Nkulengu Rail, Himantornis haematopus), but a further classification within that taxon is not possible.

Most other Oligocene Rallidae are known from a few bones only and tell us little apart from the presence of rails in European and African deposits of that geological period. This applies to a distal tarsometatarsus of an unnamed rail from the early Oligocene of the Jebel Qatrani Formation (Fayum) in Egypt (Rasmussen et al. 1987) and Rallicrex kolozsvarensis Lambrecht, 1933 from the "middle" Oligocene of Romania (distal tarsometatarsus). Remains of Paraortygometra porzanoides (Milne-Edwards, 1869) were reported from the late Oligocene of France by Mourer-Chauvire et al. (2004).

Boles (2001b) indicated that rails were also found in the late Oligocene Etadunna Formation, and Boles (2005a) described a flightless rail in the extant taxon Gallinula, Gallinula disneyi, from late Oligocene to early Miocene deposits of the Riversleigh Formation in Australia. This species apparently existed over a time span of about 15 million years, and the fossil material consists of remains of most major wing and leg bones. Its flightlessness was inferred from the proportions of the limb elements. Whereas extant rails include several flightless insular species, flightlessness in the continental G. disneyi is more unusual, as the species coexisted with marsupial carnivores. If correctly assigned to Gallinula, this species would be the earliest known crown group representative of the Rallidae. Boles (2005a) even assumed that it may be on the stem lineage of the extant flightless Tasmanian Native-hen (G. mortierii).

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