Grey-winged trumpeters Psophia crepitans, copyright A. Vinot.

Belongs within: Neognathae.
Contains: Rallidae, Sarothrura, Eogruidae, Gruidae.

The Gruiformes, cranes, rails and their relatives, are a group of generally large-footed birds commonly associated with damp habitats. A number of families previously associated with this group, such as the Otididae (bustards), Cariamidae (cariamas), and Eurypygiformes (sunbittern and kagu), are now recognised as independent lineages within the birds. The remaining monophyletic Gruiformes are difficult to define morphologically but generally possess supraorbital processes on the skull, a very narrow sternum, and a derived pelvis morphology (Mayr 2009).

The living Gruiformes are divisible into two main groups: the Ralloidea include the rails (Rallidae) and finfoots (Heliornithidae) whereas the Gruoidea include the cranes (Gruidae), limpkins (Aramus) and trumpeters (Psophia).

Cranes off the rails
Published 2 November 2009
The ‘Messel rail’ Messelornis cristata—a specimen with preserved plumage. Photo from here.

Despite its presentation in years of fieldguides and other popular books, the bird order ‘Gruiformes’ has in recent times been scattered to the four winds, with analyses both morphological and molecular proclaiming its polyphyly. Nevertheless, molecular analyses such as Hackett et al. (2008) continue to support a clade roughly corresponding to the suborder Grues as recognised by Cracraft (1973)* containing the cranes and the rails. The morphological analysis of Livezey & Zusi (2007) on the other hand, does not support this clade, but it does support monophyly for each of the two primary divisions within Grues, the ralloid and gruoid lineages.

*Just to confuse matters, the name “Grues” has been used by different authors for clades of differing inclusivity. Mayr (2009), for instance, uses “Grues” for the Aramus + Gruidae clade, and refers to the larger clade as “core Gruiformes”.

The ralloid line contains the living families Rallidae*, the rails, and Heliornithidae, the finfoots (or should that be finfeet?) Cracraft (1973) regarded the Cretaceous Laornis edvardsianus as a stem ralloid, but no-one else seems to have taken him up on this suggestion. More reliably on the ralloid stem are the Palaeocene to Oligocene Messelornithidae (Mayr 2009). Messelornithids were medium-sized birds (about the size of a small chicken) best known from Messelornis cristata for which over 500 specimens are available, some even with preserved feathering. Messelornis was highly terrestrialised with limited flight capabilities and almost ludicrously long legs (loss or reduction of flight has been a common occurrence among the Grues). Its beak was relatively short and the overall appearance of Messelornis would probably have not been dissimilar to the modern cariamas.

*Hackett et al. (2008) resolved the Rallidae as paraphyletic to Heliornithidae, with Sarothrura (the flufftails) closer to Heliornis than to the other two included rails Himantornis and Rallus. A few places, at least online, have suggested recognising Sarothrura as a separate family from the Rallidae as a result, but I’d recommend waiting for a more detailed analysis with greater coverage of the Rallidae. Increased taxonomic coverage may return the flufftails to the other Rallidae, or it may make it more appropriate to treat the finfoots as derived rallids.

The sungrebe Heliornis fulica of tropical South America (I tried to find a picture of one carrying chicks, but no luck). Photo by Jerry Oldenettel.

The finfoots of the Heliornithidae are three species (one in Asia, one in Africa, one in South America) of tropical grebe-like birds, renowned for their reclusiveness. The South American sungrebe Heliornis fulica is the most distinctive in appearance of the three species (though mitochondrial analysis indicates that it and the Asian Heliopais personata form a clade to the exclusion of the African Podica senegalensis—Fain et al. 2007) and is also very distinct in its nesting behaviour. Heliopais and Podica, like most aquatic birds, have chicks that hatch out reasonably well-developed and immediately able to swim after their parents. Heliornis, in contrast, has altricial chicks that hatch out after only ten to eleven days of incubation. The really amazing bit, though, is what happens after the chicks hatch. The male sungrebe has a shallow pouch under each wing and he is able to transport the chicks inside this pouch, even flying with them. Whether the chicks remain in the pouches permanently or whether they are only placed in them while the male is travelling remains unknown. Funnily enough, while this chick-carrying behaviour was described by Alvarez del Toro in 1971, it had originally been recorded almost 140 years earlier by Prince Maximilian of Wied. It seems that everyone else had assumed the prince was smoking something.

The gruoid lineage includes Psophia, the trumpeters, Aramus guarauna, the limpkin, and Gruidae, the cranes, as well as the fossil taxa Parvigrus pohli, Geranoididae and Eogruidae. Most recent authors agree that Aramus and Gruidae form a clade to the exclusion of Psophia. The chicken-sized Oligocene Parvigrus was originally described by Mayr (2005a) as sister to Aramus + Gruidae, but he later (Mayr 2009) revised its position to stem gruoid. Parvigrus lacked the long beak of limpkins and cranes, as do the Recent trumpeters, three species of similarly chicken-sized birds found in northern South America.

Whether Geranoididae and Eogruidae possessed crane-like long beaks is an unknown factor as skull material for both has not been found. Cracraft (1973) placed both outside the crown gruoids, but Clarke et al. (2005) placed Eogruidae inside the gruoid crown as sister to Aramus + Gruidae. The Eocene Geranoididae have been described only from leg bones (Wetmore, 1933, assigned some wing bones to Geranoides jepseni in his original description of this species but did not describe them) so little can be said about them except that they were large and long-legged. Wetmore (1933) commented on the unusually wide spacing of the trochleae (the ‘knuckles’) at the end of the tarsometatarsus suggesting that Geranoides had very widely splayed toes, but Cracraft (1969) later attributed to wide spacing to post-mortem distortion. Cracraft (1969, 1973) included a number of Eocene birds in the Geranoididae but admitted a lack of derived characters uniting them; Geranoididae may represent a paraphyletic assemblage of basal gruoids.

Distal ends of tarsometatarsi of the eogruids Proergilornis and Ergilornis, showing reduction of the inner trochlea in Proergilornis and its loss in Ergilornis. Figure from Cracraft (1973).

The Eocene to Pliocene Eogruidae were also decent-sized long-legged birds from central Asia and (in later times) Europe. Earlier authors recognised two families, Eogruidae and Ergilornithidae, but ‘ergilornithids’ are now recognised as derived eogruids. Eogruids were highly cursorial birds and a humerus attributed to Ergilornis suggests that it was flightless, though the earlier Eogrus aeola shows no sign of being so (Clarke et al. 2005). Originally three-toed, eogruids showed a reduction in the size of the inner toe, and Ergilornis and Amphipelargus (the latest of the eogruids) lost it entirely (it is easy to present a progression from flying and three-toed to flightless and two-toed, but be warned that three-toed species survived into the Miocene, well after the appearance of the two-toed forms). The only other birds to reduce the number of toes to two are the ostriches, and a relationship between ostriches and eogruids has been suggested in the past (generally in association with the idea that the ratites do not form a monophyletic group). However, Cracraft (1973) confirmed that eogruids were more similar in their fine morphology to gruoids than ostriches, and modern phylogenetic analyses do not support a close relationship of ostriches and gruoids.

Many people carry the impression that flightlessness in birds is associated with lack of predators. However, eogruids evolved flightlessness in an environment in which predators were no rarity (amongst others, they shared their world with such horrors as hyaenodonts and entelodonts*). Similarly, while the exact circumstances in which they became flightless is unknown, modern ostriches (Africa), emus (Australia) and rheas (South America) all live alongside significant predators or at least did so until recently. Obviously, something other than lack of predators is at play here.

*I always imagine Roald Dahl’s hornswogglers to be something like an entelodont.

Systematics of Gruiformes

Synapomorphies (from Livezey 1998, as Grues): Body of ‘os’ entoglossum unossified; facies ventralis of extremitas omalis coracoidei with foramen pneumaticum present.

| i. s.: Aptornis Mantell 1848 [=Apterornis Owen 1848; Aptornithidae]CC10
| |--*A. otidiformis (Owen 1844) [=Dinornis otidiformis]CC10
| `--A. defossor Owen 1871CC10 [=A. otidiformis defossorGM91; incl. A. bulleri Owen in Buller 1888CC10]
| Walbeckornis Mayr 2007M09, M07
| `--*W. creber Mayr 2007M07
| Wanshuina lii Hou 1994M09
| | |--Itardiornis Mourer-Chauviré 1995M02
| | | `--*I. hessae Mourer-Chauviré 1995M02
| | `--Messelornis Hesse 1988M02
| | |--*M. cristata Hesse 1988M02
| | |--M. nearctica Hesse 1992M02
| | `--M. russelli Mourer-Chauviré 1995M02
| `--RalloideaG-RGT14
| | i. s.: Megagallinula harundinea Kurochkin 1968M09
| | Songzia [Songziidae]M09
| | `--S. heidangkouensis Hou 1990M09
| |--RallidaeG-RGT14
| `--+--Heliornithidae [Heliornithes, Podoanidae]G-RGT14
| | |--Heliopais Sharpe 1893L98
| | | `--H. personata (Gray 1849)L98
| | `--+--Podica Lesson 1831 [Podicidae]L98
| | | `--P. senegalensis (Vieillot 1817)L98
| | `--Heliornis Bonnaterre 1791L98 [incl. Podoa Illiger 1811B94]
| | `--H. fulica (Boddaert 1783)L98
| `--SarothruridaeG-RGT14
| |--SarothruraG-RGT14
| `--+--Canirallus Bonaparte 1856G-RGT14, L98 [incl. MentocrexL98]
| | |--C. beankaensisG-RGT14
| | |--C. kioloides (Pucheran 1845) [=Mentocrex kioloides]L98
| | `--C. oculeus (Hartlaub 1855)L98
| `--Nesotrochis Wetmore 1918L98
| |--N. debooyi Wetmore 1918L98
| |--N. picapicensis (Fischer & Stephan 1971)L98
| `--N. steganinos Olson 1974L98
| i. s.: GeranoididaeM09
| |--Geranoides jepseni Wetmore 1933M09
| |--Eogeranoides campivagus Cracraft 1969M09
| |--Geranodornis aenigma Cracraft 1969M09
| |--Palaeophasianus Shufeldt 1913M07
| | |--P. incompletus Cracraft 1969M09
| | `--P. meleagroides Shufeldt 1913M09
| `--ParagrusM09
| |--P. prentici (Loomis 1906)M09
| `--P. shufeldti Cracraft 1969M09
| Gypsornis Milne-Edwards 1869M09, M02 [incl. Percolinus Harrison & Walker 1977M02]
| |--*G. cuvieri Milne-Edwards 1869M02
| `--G. venablesi (Harrison & Walker 1977) [=*Percolinus venablesi]M02
| |--Parvigrus Mayr 2005M05a
| | `--*P. pohli Mayr 2005M05a
| `--Rupelrallus Fischer 1997M09, M05b
| `--R. saxoniensis Fischer 1997M09
| `--GruesM09
| |--GruidaeG-RGT14
| `--AramidaeM09
| |--Loncornis erectus Ameghino 1899M09
| |--Badistornis aramus Wetmore 1940U93
| `--Aramus Vieillot 1816L98
| |--A. guaranus (Linnaeus 1766)L98
| |--A. scolopaceusPB27
| `--A. vociferusPB27
`--Psophiidae [Psophioidea]L98
|--Anisolornis excavatus Ameghino 1891U93
`--Psophia Linnaeus 1758L98
| i. s.: P. ochroptera [=P. crepitans ochroptera, P. leucoptera ochroptera]C88
| P. undulataG97
|--*P. crepitans Linnaeus 1758L58, L98
| |--P. c. crepitansC88
| `--P. c. napensisC88
`--+--P. leucoptera Spix 1825L98
`--P. viridis Spix 1825L98
|--P. v. viridisC88
|--P. v. dextralisC88
|--P. v. interjectaC88
`--P. v. obscuraC88

*Type species of generic name indicated


[B94] Bock, W. J. 1994. History and nomenclature of avian family-group names. Bulletin of the American Museum of Natural History 222: 1–281.

[CC10] Checklist Committee (OSNZ). 2010. Checklist of the Birds of New Zealand, Norfolk and Macquarie Islands, and the Ross Dependency, Antarctica 4th ed. Ornithological Society of New Zealand and Te Papa Press: Wellington.

Clarke, J. A., M. Norell & D. Dashzeveg. 2005. New avian remains from the Eocene of Mongolia and the phylogenetic position of the Eogruidae (Aves, Gruoidea). American Museum Novitates 3494: 1–17.

Cracraft, J. 1969. Systematics and evolution of the Gruiformes (class, Aves). 1, The Eocene family Geranoididae and the early history of the Gruiformes. American Museum Novitates 2388: 1–41.

Cracraft, J. 1973. Systematics and evolution of the Gruiformes (class Aves). 3, Phylogeny of the suborder Grues. Bulletin of the American Museum of Natural History 151: 1–127.

[C88] Cracraft, J. 1988. Deep-history biogeography: retrieving the historical pattern of evolving continental biotas. Systematic Zoology 37 (3): 221–236.

Fain, M. G., C. Krajewski & P. Houde. 2007. Phylogeny of “core Gruiformes” (Aves: Grues) and resolution of the limpkin–sungrebe problem. Molecular Phylogenetics and Evolution 43: 515–529.

[G-RGT14] Garcia-R, J. C., G. C. Gibb & S. A. Trewick. 2014. Deep global evolutionary radiation in birds: diversification and trait evolution in the cosmopolitan bird family Rallidae. Molecular Phylogenetics and Evolution 81: 96–108.

[G97] Geoffroy, É. L. 1797. Note sur les genres Psophia et Palamedea de Linné. Bulletin des Sciences, par la Societé Philomathique de Paris 1 (7): 50–51.

[GM91] Gill, B., & P. Martinson. 1991. New Zealand’s Extinct Birds. Random Century: Auckland (New Zealand).

Hackett, S. J., R. T. Kimball, S. Reddy, R. C. K. Bowie, E. L. Braun, M. J. Braun, J. L. Chojnowski, W. A. Cox, K.-L. Han, J. Harshman, C. J. Huddleston, B. D. Marks, K. J. Miglia, W. S. Moore, F. H. Sheldon, D. W. Steadman, C. C. Witt & T. Yuri. 2008. A phylogenomic study of birds reveals their evolutionary history. Science 320: 1763–1768.

[L58] Linnaeus, C. 1758. Systema Naturae per Regna Tria Naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Laurentii Salvii: Holmiae.

[L98] Livezey, B. C. 1998. A phylogenetic analysis of the Gruiformes (Aves) based on morphological characters, with an emphasis on the rails (Rallidae). Philosophical Transactions of the Royal Society of London Series B—Biological Sciences 353: 2077–2151.

Livezey, B. C., & R. L. Zusi. 2007. Higher-order phylogeny of modern birds (Theropoda, Aves: Neornithes) based on comparative anatomy. II. Analysis and discussion. Zoological Journal of the Linnean Society 149 (1): 1–95.

[M05a] Mayr, G. 2005a. A chicken-sized crane precursor from the early Oligocene of France. Naturwissenschaften 92: 389–393.

[M05b] Mayr, G. 2005b. The Paleogene fossil record of birds in Europe. Biological Reviews 80: 515–542.

[M07] Mayr, G. 2007. The birds from the Paleocene fissure filling of Walbeck (Germany). Journal of Vertebrate Paleontology 27 (2): 394–408.

[M09] Mayr, G. 2009. Paleogene Fossil Birds. Springer.

[M02] Mlíkovský, J. 2002. Cenozoic Birds of the World. Part 1: Europe. Ninox Press: Praha.

[PB27] Pilsbry, H. A., & J. Bequaert. 1927. The aquatic mollusks of the Belgian Congo, with a geographical and ecological account of Congo malacology. Bulletin of the American Museum of Natural History 53 (2): 69–602, pls 10–77.

[U93] Unwin, D. M. 1993. Aves. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 717–737. Chapman & Hall: London.

Wetmore, A. 1933. Fossil bird remains from the Eocene of Wyoming. Condor 35: 115–118.

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