Gruiformes
Encyclopedia
The Gruiformes are an order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

  containing a considerable number of living and extinct bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

 families
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

, with a widespread geographical diversity. Gruiform means "crane-like".

Traditionally, a number of wading and terrestrial bird families that did not seem to belong to any other order were classified together as Gruiformes. These include 14 species of large cranes
Crane (bird)
Cranes are a family, Gruidae, of large, long-legged and long-necked birds in the order Gruiformes. There are fifteen species of crane in four genera. Unlike the similar-looking but unrelated herons, cranes fly with necks outstretched, not pulled back...

, about 145 species of smaller crakes and rails
Rallidae
The rails, or Rallidae, are a large cosmopolitan family of small to medium-sized birds. The family exhibits considerable diversity and the family also includes the crakes, coots, and gallinules...

, as well as a variety of families comprising one to three species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

, such as the Heliornithidae
Heliornithidae
The Heliornithidae are a small family of tropical birds with webbed lobes on their feet like those of grebes and coots. The family overall are known as finfoots, although one species is known as a Sungrebe. The family is composed of three species in three genera.-Description:Finfoots resemble...

, the limpkin
Limpkin
The Limpkin , Aramus guarauna, is a bird that looks like a large rail but is skeletally closer to cranes. It is the only extant species in the genus Aramus and the family Aramidae. It is found mostly in wetlands in warm parts of the Americas, from Florida to northern Argentina...

, or the trumpeter
Trumpeter (bird)
The trumpeters are a family of birds restricted to the humid forests of the Amazon and Guiana Shield in South America. They are named for the trumpeting or cackling threat call of the males. The three species resemble chickens in size; they measure 45 to 52 centimetres long and weigh 1 to 1.5...

s.
Other birds have been placed in this order more out of necessity to place them somewhere; this has caused the expanded Gruiformes to lack distinctive apomorphies. Recent studies indicate that these "odd Gruiformes" are if at all only loosely related to the cranes, rails, and relatives ("core Gruiformes").

Systematics

There are only two suprafamilial clades (natural groups) among the birds traditionally classified as Gruiformes. Rails (Rallidae), finfoots and sungrebe (Heliornithidae), adzebills (Aptornithidae), trumpeters (Psophiidae), limpkin (Aramidae), and cranes (Gruidae) compose the suborder Grues and are termed "core-Gruiformes" (Fain et al. 2007). These are the only true Gruiformes. The suborder Eurypygae includes the kagu (Rhynochetidae) and sunbittern (Eurypygidae). These are not even remotely related to Grues. The families of mesites or roatelos (Mesitornithidae), button-quails (Turnicidae), Australian Plains-wanderer (Pedionomidae), seriemas (Cariamidae), and bustards (Otididae) each represent distinct and unrelated lineages. Many families known only from fossils have been assigned to the Gruiformes, e.g., Ergilornithidae, Phorusrhacidae, Messelornithidae, Eogruidae, Idiornithidae, Bathornithidae, to name just a few (see below). In spite of the fact that some of these are superficially 'crane-like' and the possibility that some may even be related to extant families traditionally included in the Gruiformes, there are no completely extinct families that can be confidently assigned to core-Gruiformes.

The traditional order Gruiformes was established by the influential German avian comparative anatomist Max Fürbringer (1888). Over the decades, many ornithologists suggested that members of the order were in fact more closely related to other groups (reviewed by Olson 1985, Sibley and Ahlquist 1990). For example, it was thought that sunbittern might be related to herons and that seriemas might be related to cuckoos. Olson and Steadman (1981) were first to correctly disband any of the traditional Gruiformes. They recognized that the Australian Plains-wanderer (family Pedionomidae) was actually a member of the shorebirds (order Charadriiformes) based on skeletal characters. This was confirmed by Sibley & Ahlquist (1990) based on DNA-DNA hybridization and subsequently by Paton et al. (2003), Paton and Baker (2006) and Fain and Houde (2004, 2006). Sibley and Ahlquist furthermore removed button-quails (Turnicidae) from the Gruifomes based on large DNA-DNA hybridization distances to other supposed Gruiformes. However, it was not until the work of Paton et al. (2004) and Fain and Houde (2004, 2006) that the correct placement of buttonquails within the shorebirds (order Charadriiformes) was documented on the basis of phylogenetic analysis of multiple genetic loci. Using 12S ribosomal DNA sequences, Houde et al. (1997) were the first to present molecular genetic evidence of gruiform polyphyly, although apparently they were not convinced by it. However on the basis of numerous additional sequence data, it has been shown decisively that the traditionally recognized Gruiformes consist of five to seven unrelated clades (Fain and Houde 2004, Ericson et al. 2006, Hackett et al. 2008).

Fain & Houde (2004) proposed that Neoaves are divisible into two clades, Metaves and Coronaves, although it has been suggested from the start that Metaves maybe paraphyletic (Fain and Houde 2004, Ericson et al. 2006, Hackett et al. 2008). Sunbittern, kagu, and mesites all group within Metaves but all the other lineages of "Gruiformes" group either with a collection of waterbirds or landbirds within Coronaves. This division has been upheld by the combined analysis of as many as 30 independent loci (Ericson et al. 2006, Hackett et al. 2008), but is dependent on the inclusion of one or two specific loci in the analyses. One locus, i.e., mitochondrial DNA, contradicts the strict monophyly of Coronaves (Morgan-Richards et al. 2008), but phylogeny reconstruction based on mitochondrial DNA is complicated by the fact that few families have been studied, the sequences are heavily saturated (with back mutations) at deep levels of divergence, and they are plagued by strong base composition bias.

The kagu
Kagu
The Kagu or Cagou is a crested, long-legged, and bluish-grey bird endemic to the dense mountain forests of New Caledonia. It is the only surviving member of the genus Rhynochetos and the family Rhynochetidae, although a second species has been described from the fossil record...

 and sunbittern
Sunbittern
The Sunbittern, Eurypyga helias is a bittern-like bird of tropical regions of the Americas, and the sole member of the family Eurypygidae and genus Eurypyga.-Description and reproduction:...

 are one another's closest relatives. It had been proposed (Cracraft 2001) that they and the recently extinct adzebills (family Aptornithidae) from New Zealand constitute a distinct Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...

n lineage. However, sunbittern and kagu are believed to have diverged from one another long after the break-up of Gondwanaland and the adzebills are in fact members of the Grues (Houde et al. 1997, Houde 2009). The seriema
Seriema
The seriemas are the sole extant members of the small and ancient family Cariamidae, which is also the sole surviving family of the Cariamae. Once believed to be related to cranes, they have been placed by one recent study near the falcons, parrots and passerines, as well as the extinct terror birds...

s and bustard
Bustard
Bustards, including floricans and korhaans, are large terrestrial birds mainly associated with dry open country and steppes in the Old World...

s represent distinct lineages within neoavian waterbirds.

ORDER GRUIFORMES
  • Suborder Ralli
    • Family Rallidae
      Rallidae
      The rails, or Rallidae, are a large cosmopolitan family of small to medium-sized birds. The family exhibits considerable diversity and the family also includes the crakes, coots, and gallinules...

       (flufftails, crakes, moorhens, gallinules, and rails) paraphyletic to Heliornithidae and Aptornithidae
    • Family Heliornithidae
      Heliornithidae
      The Heliornithidae are a small family of tropical birds with webbed lobes on their feet like those of grebes and coots. The family overall are known as finfoots, although one species is known as a Sungrebe. The family is composed of three species in three genera.-Description:Finfoots resemble...

       (finfoots and Sungrebe) nested within Rallidae
    • Family †Aptornithidae
      Adzebill
      The adzebills, genus Aptornis, were two closely related bird species, the North Island Adzebill, Aptornis otidiformis, and the South Island Adzebill, Aptornis defossor, of the extinct family Aptornithidae. The family was endemic to New Zealand.They have been placed in the Gruiformes but this is not...

       (adzebills) (prehistoric
      Late Quaternary prehistoric birds
      Prehistoric birds are various taxa of birds that became extinct before recorded history, or more precisely, before they could be studied alive by bird scientists...

      ) - nested within Rallidae
  • Suborder Grui
    • Family †Eogruidae (fossil
      Fossil
      Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

      )
    • Family †Ergilornithidae (fossil
      Fossil
      Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

      ) - may belong in Eogruidae
    • Family Gruidae (cranes)
    • Family Aramidae
      Limpkin
      The Limpkin , Aramus guarauna, is a bird that looks like a large rail but is skeletally closer to cranes. It is the only extant species in the genus Aramus and the family Aramidae. It is found mostly in wetlands in warm parts of the Americas, from Florida to northern Argentina...

       (Limpkin)
    • Family Psophiidae (trumpeters)
  • Families incertae sedis and doubtful Gruiformes
    • Family †Parvigruidae (fossil
      Fossil
      Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

      )
    • Family †Songziidae (fossil
      Fossil
      Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

      )
    • Family †Gastornithidae (diatrymas) (fossil
      Fossil
      Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

      )
    • Family †Messelornithidae (Messel
      Messel pit
      The Messel Pit is a disused quarry near the village of Messel, about southeast of Frankfurt am Main, Germany. Bituminous shale was mined there. Because of its abundance of fossils, it has significant geological and scientific importance...

      -birds)
    • Family †Salmilidae (fossil
      Fossil
      Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

      )
    • Family †Geranoididae (fossil
      Fossil
      Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

      )
    • Family †Bathornithidae (fossil
      Fossil
      Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

      ) - distinct order (Cariamae
      Cariamae
      Cariamae is a suggested name for a group of primarily flightless birds that have been around for 63 million years. The group includes the families Cariamidae, Phorusrhacidae, Bathornithidae, Idiornithidae and Ameghinornithidae...

      )
    • Family †Idiornithidae (fossil
      Fossil
      Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

      ) - distinct order (Cariamae
      Cariamae
      Cariamae is a suggested name for a group of primarily flightless birds that have been around for 63 million years. The group includes the families Cariamidae, Phorusrhacidae, Bathornithidae, Idiornithidae and Ameghinornithidae...

      )
    • Family †Phorusrhacidae (terror birds) (fossil
      Fossil
      Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

      ) - distinct order (Cariamae
      Cariamae
      Cariamae is a suggested name for a group of primarily flightless birds that have been around for 63 million years. The group includes the families Cariamidae, Phorusrhacidae, Bathornithidae, Idiornithidae and Ameghinornithidae...

      )
    • Family Cariamidae (seriemas) - Neoavian landbirds - distinct order (Cariamae
      Cariamae
      Cariamae is a suggested name for a group of primarily flightless birds that have been around for 63 million years. The group includes the families Cariamidae, Phorusrhacidae, Bathornithidae, Idiornithidae and Ameghinornithidae...

      )
    • Family Otididae
      Bustard
      Bustards, including floricans and korhaans, are large terrestrial birds mainly associated with dry open country and steppes in the Old World...

       (bustards) - Neoavian waterbirds - distinct order
    • Family Eurypygidae (Sunbittern) - prospective "Metaves" - new order Eurypygiformes
      Eurypygiformes
      Eurypygiformes is a clade formed by the Kagu , a bird endemic to New Caledonia, and the Sunbittern from the tropical regions of the Americas....

       together with kagu
    • Family Rhynochetidae
      Kagu
      The Kagu or Cagou is a crested, long-legged, and bluish-grey bird endemic to the dense mountain forests of New Caledonia. It is the only surviving member of the genus Rhynochetos and the family Rhynochetidae, although a second species has been described from the fossil record...

       (Kagu) - prospective "Metaves" - new order Eurypygiformes together with sunbittern
    • Family Mesitornithidae
      Mesite
      The mesites are a family of birds of uncertain affinities. They are smallish, near flightless birds endemic to Madagascar. Generally brownish with paler undersides, they are of somewhat pheasant-like appearance and were initially placed with the Galliformes...

       (mesites, roatelos, monias) prospective "Metaves" - distinct order


When considered to be monophyletic, it was assumed that Gruiformes was among the more ancient of avian lineages. The divergence of "gruiforms" among "Metaves" and "Coronaves" is proposed to be the first divergence among Neoaves, far predating the Cretaceous–Tertiary extinction event c. 65 mya(Houde 2009). No unequivocal basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...

 gruiforms are known from the fossil record. However, there are several genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 which are not unequivocally assignable to the known families and which may occupy a more basal position:
  • Propelargus (Late Eocene/Early Oligocene of Quercy, France) - cariamid or idornithid
  • Rupelrallus (Early Oligocene of Germany) - rallid? parvigruid?
  • Badistornis (Brule Middle Oligocene of Shannon County, USA) - aramid?
  • Probalearica (Late Oligocene? - Middle Pliocene of Florida, USA, France?, Moldavia and Mongolia) - gruid? A nomen dubium
    Nomen dubium
    In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...

    ?
  • "Gruiformes" gen. et sp. indet. MNZ S42623 (Bathans Early/Middle Miocene of Otago, New Zealand) - Aptornithidae?
  • Aramornis (Sheep Creek Middle Miocene of Snake Creek Quarries, USA) - gruid? aramid?
  • Euryonotus (Pleistocene of Argentina) - rallid?
  • Occitaniavis - cariamid or idiornithid, includes Geranopsis elatus


Other even more enigmatic fossil birds are occasionally suggested to belong into this order, such as the proposed Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...

 family Laornithidae and the following taxa:
  • Horezmavis (Bissekty Late Cretaceous of Kyzyl Kum, Uzbekistan)
  • Telmatornis
    Telmatornis
    Telmatornis is a prehistoric bird genus of unclear affiliations. It apparently lived in the Late Cretaceous; its remains were found in the early Maastrichtian Navesink Formation of New Jersey. A single species is included today, Telmatornis priscus...

    (Navesink Late Cretaceous?)
  • Amitabha (Bridger middle Eocene of Forbidden City, USA) - rallid?
  • Eobalearica (Ferghana Late? Eocene of Ferghana, Uzbekistan) - gruid?
  • "Phasianus" alfhildae (Washakie B Late Eocene of Haystack Butte, USA)
  • Talantatos (Late Eocene of Paris Bain, France)
  • Telecrex (Irdin Manha Late Eocene of Chimney Butte, China) - rallid?
  • Neornithes incerta sedis (Late Paleocene/Early Eocene of Ouled Abdoun Basin, Morocco)
  • Aminornis (Deseado Early Oligocene of Rio Deseado, Argentina) - aramid?
  • Loncornis (Deseado Early Oligocene of Rio Deseado, Argentina) - aramid?
  • Riacama (Deseado Early Oligocene of Argentina)
  • Smiliornis (Deseado Early Oligocene of Argentina)
  • Pseudolarus (Deseado Early Oligocene - Miocene of Argentina) - gruiform?
  • Gnotornis (Brule Late Oligocene of Shannon County, USA) - aramid?
  • Anisolornis (Santa Cruz Middle Miocene of Karaihen, Argentina) - aramid?

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