Opisthocomiformes — Hoatzin

Gruiformes — Cranes, Rails etc.

Charadriiformes — Shorebirds

The 46 Orders










GRUAE Bonaparte, 1854

The Gruae include the Opisthocomiformes (Hoatzin) and the Gruimorphae. Bootstrap support for this clade was 91%, and it is possible that it merely appears to be a clade. Indeed, one of their alternative trees had the Hoatzin on its own branch, rather than part of Gruae. Support for Gruimorphae (Gruiformes plus Charadriiformes) was higher (96%). I have more confidence in that grouping as the Charadriiformes and Gruiformes have often been considered close on morphological grounds.


The Opisthocomiformes contain a single extant species, the Hoatzin, and are restricted to South America (mainly in the Amazon and Orinoco basins). This was not always true. There is fossil evidence of Opisthocomiformes from Namibia (Mayr, Alvarenga, and Mourer-Chauviré, 2011), Kenya (Mayr, 2014c), and France (Mayr and De Pietri, 2014), as well as from South America. There is also a fossil from the Green River Formation in Wyoming that has some similarities to Opisthocomiformes (Olson, 1992), but its true affinites are unknown and could be related to cuckoos or turacos.

A morphological analysis of modern Opisthocomus, and fossil Hoazinavis (Brazil, 22-24 mya), Protoazin (France, 34 mya), and Namibiavis (Namibia and Kenya, 15-17.5 mya), found Hoazinavis most closely related to modern Opisthocomus, followed by Protoazin, with Namibiavis the most distant relative.

A long list of bird families have been considered the closet relatives of the Hoatzin, including seriemas, cuckoos, turacos, rails, doves, and others. The lack of any close relatives justifies placing it in its own order. Fain and Houde (2004) and Ericson et al. considered it part of Metaves. The TiF list currently follows Jarvis et al. (2014), who put it as the basal taxon in Gruae. However, the bootstrap support is only 91%, so there is uncertainty about this. The Hoatzin could belong to one of the other high level groups, or even form its own high level group (Jarvis et al, 2014, Fig. 3b).

Opisthocomidae: Hoatzin Swainson, 1837

1 genus, 1 species HBW-3

GRUIMORPHAE Bonaparte, 1854

The Gruimorphae split into two groups: Gruiformes and Charadriiformes. The Gruimorphae are here, the Charadriiformes are on the next page.

GRUIFORMES Bonaparte, 1854

All sorts of taxa have been previously been included in the Gruiformes, which seemed to serve as a waste-bin taxon. The mesites, kagu, and sunbittern were once considered Gruiformes. This version of the Gruiformes is a more coherent clade. The family order is based on Fain et al. (2007). Mayr (2008a) discusses both DNA and morphological support for this clade.

Psophiidae: Trumpeters Mathews, 1913

1 genus, 6 species HBW-3

The trumpeters are an ancient lineage, probably becoming distinct from the limpkins and cranes in the Paleocene or Eocene. Nonetheless, the current crop of trumpeters are quite closely related. Indeed, Ribas et al. (2012) estimate that the common ancestor of all the extant trumpeters lived about 3 million years ago. At some point within the last few million years, only one trumpeter species left present-day descendants. Since the trumpeters have been around roughly 50 million years, it is likely that many species of trumpeters died out. This suggests that extinction plays a very important role in the biodiversity that we see, and that it hides much avian history.

Although the SACC arranges the 8 recognized subspecies of trumpeter into 3 species, I currently recognize 6 species. Oppenheimer and Silveira (2009) suggest that interjecta is indistinguishable from dextralis. Ribas et al. (2012) found 8 genetically distinct lineages, including interjecta. However, the genetic distance between interjecta and dextralis was small. The subspecies obscura was slightly more distinct, having separated roughly 500,000 years ago. The case for treating these as separate species is weak. For now I group them all as P. obscura. The other races of trumpeter are more distinct from one another, having likely separated from nearly 1 to about 2 million years ago. In the case of napensis and ochroptera, there is no sign of interbreeding in spite of a range overlap. This suggests they are separate species, and provides support for treating the remaining trumpeters as separate species.

Psophiidae tree

Ribas et al. (2012) also show how the separation of the trumpeters relates to the formation of various riverine barriers in the Amazon region. The various trumpeters inhabit several of the well-known areas of endemism in the Amazon. If other types of animal show a similar pattern and timing of separation, it will help explain the existence of these areas of endemism.

The additional English names are those used by Hellmayr and Conover (1942), sometimes for subspecies.

Aramidae: Limpkin Bonaparte, 1842

1 genus, 1 species HBW-3

Gruidae: Cranes Vigors, 1825

2 genera, 15 species HBW-3

The basic structure of the crane family has been known for some time. The cranes fall into two genera, Balearica and Grus, which are sometimes also considered subfamilies. Some authors have placed some of the Grus cranes in other genera, but for two decades the genetic data has shown these other genera are embedded in Grus. This was already visible in the DNA hybridization analysis of Krajewski (1989). It was even clearer in the cytochrome-b analysis of Krajewski and Fetzner (1994). Fain, Krajewski, and Houde (2007) refine this in a multi-gene analysis. The most recent analysis is that of Krajewski et al. (2010). They use the complete mitochondrial genome, and their analysis is followed here.

Heliornithidae: Finfoots G.R. Gray, 1840

3 genera, 3 species HBW-3

Sarothruridae: Flufftails

There have been suggestions that this group deserves recognition as a family since at least Sibley and Ahlquist (1985). Hackett et al. (2008) found that Sarothrura is more closely related to the finfoots than to the rails. Garcia-R. et al. (2014a) found that same is true of Canirallus, and that it is more closely related to Sarothrura than to the finfoots. Accordingly, they are placed in a separate family.

Livezey (1998) suggested that Rallicula (formerly part of Rallina) may also belong with the flufftails based on a phylogenetic analysis of osteological, myological, and integumentary characters.

The Tsingy Wood Rail, Canirallus beankaensis, has been newly discovered within the Madagascan Wood Rail complex. See Goodman et al. (2011).

3 genera, 16 species Not HBW Family

Rallidae: Rails, Gallinules, Coots Rafinesque, 1815

43 genera, 150 species HBW-3

Click for Rallidae species tree
Click for Rallidae species tree

The only comprehensive molecular review of the rails is García-R. et al. (2014). Their results are generally consistent with earlier partial studies including Trewick (1997), Slikas et al., (2002), Groenenberg et al. (2008), and Ozaki et al. (2010). The discussion in Christidis and Boles (2008) was also helpful as was the reanalysis of archived data by Raty on BirdForum. We still lack DNA for nine genera containing twelve species (five of them extinct). In some cases, the morphological studies by Olson (1973) and Livezey (1998) have allowed an educated guess concerning their affinities.

The genus Canirallus has moved to Sarothruridae (flufftails), as has Rallicula (formerly part of Rallina).

García-R. et al. (2014a, b) have attempted to put a chronology on rail diversification. I think their timescale is stretched a bit, at least on the far end (perhaps about 40%), but that it provides a reasonable guide for establishing higher taxa. I've divided the rails into three subfamiles: Rallinae, Gallinulinae, and Porphyrioninae, with Gallinulinae further divided into two tribes (Pardirallini and Gallinulini), and Porphyrioninae divided into four tribes (Porphyrionini, Himantornithini, Zapornini, and Laterallini). García-R. et al. (2014a, b) estimate that each of the subfamilies originated in the late Eocene, while the tribes originated in the early Oligocene.

Incertae Sedis: Rallidae

We don't have any solid information concerning Rougetius. I can't even be sure that it is part of Rallidae rather than Sarothruridae. Assuming it is part of Rallidae, it might belong somewhere in Rallinae. There's just not much basis for either treatment. That ambiguity causes me to put it first on the list.

Rallinae: Long-billed Rails and allies Rafinesque, 1815

We now turn to the Rallinae. The genera are ordered based on García-R. et al. (2014), except for four genera that have not be DNA-tested. Biensis is often considered part of Rallus, but Livezey (1999) found that suggested that the Madagascan Rail is not closely related to Rallus, so it is placed in its own genus, Biensis (Pucheran 1845). It's not clear whether it is closer to Rallus or to Gallirallus, so I have placed it between the two groups.

The extinct Aphanapteryx and Erythromachus are sometimes considered congeneric, and are most likely somewhere near Dryolimnas. Finally, Livezey (1998) found Gymnocrex sister to Habroptila, which has been merged into Gallirallus (see below). Accordingly, I place Gymnocrex next to Gallirallus.

Based on Maley (2012) and Maley and Brumfield (2013), King Rail, Rallus elegans, has been split into King Rail, Rallus elegans (eastern North America, Cuba) and Aztec Rail, Rallus tenuirostris (central Mexico). Further, Clapper Rail, Rallus longirostris, has been split into Clapper Rail, Rallus crepitans, (Caribbean and eastern North America), Ridgway's Rail, Rallus obsoletus, (western North America), and Mangrove Rail, Rallus longirostris, (South America).

Clapper/King Rail complex

Species Subspecies Range
Ridgway's Rail
R. obsoletus
obsoletus, levipes, yumanensis,
rhizophorae, beldingi
western US,
western Mexico
Aztec Rail
R. tenuirostris
tenuirostris central Mexico
Mangrove Rail
R. longirostris
phelpsi, margaritae*, pelodramus*,
longirostris*, crassirostris*, cypereti
South America
King Rail
R. elegans
elegans, ramsdeni eastern US and Mexico,
Clapper Rail
R. crepitans
crepitans, saturatus, waynei,
scottii, insularum, pallidus*,
grossi*, belizensis*, coryi,
leucophaeus, caribaeus
eastern US and Mexico,
Belize, Caribbean

* = subspecies not sampled by Maley and Brumfield (2013).

Clapper (or possibly Mangrove) Rails have very recently been discovered along the Pacific Coast of southern Central America (esp. the Gulfs of Fonseca and Nicoya). There is also a report from the Atlantic coast (Panama: Bocos del Toro). So far as I know, none of these have been definitely identified as to subspecies, but Van Dort (2013) suggests the Pacific coast rails are Mangrove Rails.

The genus Gallirallus itself has been recently studied by Kirchman (2012). As a result, the genera Eulabeornis and Habroptila, which had previously not been considered that close to Gallirallus, end up submerged inside it, as is Nesoclopeus. The genus Aramidopsis is merged into Lewinia, which gains two species from Gallirallus. Kirchman argued that the genetic distances between all the Gallirallus species is fairly small, and indicates a common ancestry as recently as a million or so years ago. This is amazingly recent!

I don't believe his calibration, which was based on the fact that rails cannot have been on Wake Island for more than about 125,000 years. The idea is that Wake Island was completely submerged at that time. More conventional molecular dating gives a much older date, about 7.8 million years ago, suggesting that the Wake Island Rail recently arrived from another island. This suggests a very rapid loss of the ability to fly. Kirchman (2012) found that the extinct Wake Island Rail's closest relative was the extinct Mangaia Rail, Gallirallus ripleyi from the Cook Islands. The Mangiaia Rail is known only from subfossil remains that appear to be 700-1000 years old, and its date of extinction is uncertain. It is not included on the main list, but is included in the Rallidae tree.

The extinct Sharpe's Rail, Gallirallus sharpei, is known from one specimen from an unknown location. According to Bird Life International, it is now thought to have been a color morph of Buff-banded Rail, Gallirallus philippensis. The information they cite remains to be published.

Gallinulinae G.R. Gray, 1840

The next group is the Gallinulinae. It contains two tribes, Pardirallini and Gallinulini. Interestingly, neither the swamphens nor the American Purple Gallinule are part of the Gallinulinae.

Pardirallini is a clade of Neotropical rails. There are two clades in Pardirallini. The first consists of the the former Cyanolimnas and Neocrex rails and the Ash-throated Crake. The latter is the type of Mustelirallus (Bonaparte 1856), and I've put merged Cyanolimnas and Neocrex into Mustelirallus. These are sister to Pardirallus, completing the first clade. The second contains the Aramides wood-rails and the Uniform Crake (Amaurolimnas).

Gallinulini mainly contains the gallinules and coots, together with the woodhens and native-hens. It also contains the remaining portion of Porzana, after many species have been transferred to Zapornia. I follow Christidis and Boles (2008) and separate Pareudiastes (Hartlaub and Finsch 1871, type pacificus) and Tribonyx (DuBus 1840, type mortierii) from Gallinula.

Note that the Spot-flanked Gallinule, formerly in Gallinula, is now in the monotypic genus Porphyriops (Pucheran 1845). Raty's reanalysis found that the Spot-flanked Gallinule, Porphyriops melanops, belongs near Porzana. This makes sense as the Spot-flanked Gallinule looks much like a Sora, Porzana carolina. García-R. et al. (2014), using more data, placed it as shown on the diagram and estimated that the common ancestor of Porzana and Porphyriops lived perhaps 20 million years ago. Even if this is 40% exaggerated, it is more than enough to support using a different genus for the gallinule.

The Lesser Moorhen is now "Gallinula" angulata instead of Gallinula (there doesn't seem to be an available name). This change was needed because "Gallinula" is basal to both Gallinula (true gallinules and moorhena) and Fulica (coots).

This list treats the Common Gallinule, Gallinula galeata and Common Moorhen, Gallinula chloropus, as separate species, as does the AOU (both NACC and SACC). Groenenberg et al. (2008) found that the Common Moorhen is more closely related to the Gough Moorhen, Gallinula comeri, and the extinct Tristan Moorhen, Gallinula nesiotis, than to the Common Gallinule. The relationships of the rest of the former Gallinula have not been subject to genetic testing.

Pardirallini: Wood-Rails and allies Livezey, 1998

Gallinulini: Coots, True Gallinules and Moorhens G.R. Gray, 1840

Porphyrioninae Reichenbach, 1849

Although the swamphens are placed next to the gallinules and coots, the genetic distance between them is quite large. Garci-R. et al. (2014a, b) estimate that their most recent common ancestor lived some 40 million years ago. This should not now be surprising. Earlier geneitic evidence has separated them with Ozaki et al. (2010) and Raty placing the swamphens sister to Laterallini and Trewick (1997) grouping them with Zapornini. The morphological evidence has also cast doubt on the position of the swamphens, with Livezey (1998) putting them in a relatively basal position.

The swamphens are in the final subfamily, Porphyrioninae. It contains four tribes: Porphyrionini, Himantornithini, Zapornini, and Laterallini.

The first tribe, Porphyrionini is mainly composed of purple gallinules and swamphens (Porphyrio). I'm speculating that Aphanocrex goes here too. Indeed, Livezey's (1998) analysis suggested that Aphanocrex might even be embedded in Porphyrula,. As for Porphyrula itself, Olson (1973) had recommended that it be merged into Porphyrio. Trewick (1997) made a genetic case for this merger, which was adopted by AOU in 2002.

Based on the genetic analysis of García-R. and Trewick (2015) and the earlier papers by Sangster, 1998) and Sangster et al. (1999, the Purple Swamphen, Porphyrio porphyrio has been split into 5 species:

The second tribe is Himantornithini, so called because it contains the Nkulengu Rail, Himantornis haematopus, which was previously thought to be a very basal member of Rallidae. Surprisingly, it is not only not basal, but seems to be sister to the New Guinea Flightless Rail, Megacrex inepta. These group with the Striped Crake, Aenigmatolimnas marginalis, White-browed Crake, Poliolimnas cinereus, Watercock, Gallicrex cinerea, and the Amaurornis bush-hens and waterhen.

Note that sample used by Trewick (1997) that is supposedly from Megacrex inepta appears to be wrong. Raty, in s BirdForum post, found that the DNA of Trewick's bird is almost identical to other DNA of Gallirallus lafresnayanus.

The third tribe in Porphyrioninae is Zapornini. It contains a number of Old World crakes. The basal genus is what remains of Rallina. Many of the other species were previously classified as genus Porzana, but have been moved to Zapornia (Leach 1816, type Gallinula minuta Montagu 1813 = parva). Given the genetic distances involved, I've separated the Black Crake as Limnocorax flavirostra (W. Peters, 1854), and the Ruddy-breasted Crake and Band-bellied Crake in genus Limnobaenus (Sundevall 1873, type fuscus).

That brings us to the last tribe, the tribe of New World crakes, Laterallini. I have resurrected Rufirallus (Bonaparte 1854, type viridis) for the Russet-crowned Crake, Rufirallus viridis. It may be sister to the Ocellated Crake, Micropygia schomburgkii (see Raty's reanalysis). They seem to form a basal group in Laterallini. Most of the rest of the species are in Laterallus or Creciscus. This includes the Black-banded Crake, Laterallus fasciatus, which has been moved from Rufirallus (or Porzana or Anurolimnas, depending on the taxonomy used). Two Laterallus (albigularis and exilis) are closer to Creciscus than Laterallus, and have been placed in Limnocrex. Limnocrex is close to Hapalocrex (Yellow-breasted Crake), and both are sister to Coturnicops (Swinhoe's and Yellow Rails). Swinhoe's Rail is the only Old World representative in Laterallini.

Raty's reanalysis grouped together a few species that look like Black Rail (jamaicensis). The Galapagos Rail belongs here too. The old name Creciscus (Cabanis 1857, type jamaicensis) applies to the group. Presumably the Inaccessible Island Rail, Atlantisia rogersi, and Ascension Rail, Mundia elpenor are close relatives.

Porphyrionini: Purple Gallinules and Swamphens Reichenbach, 1849

Himantornithini: Bush-hens and Waterhens Bonaparte, 1856

Zapornini: Old World Crakes Des Murs, 1860

Laterallini:New World Crakes Informal (TiF, 2014)

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