Gruiformes

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Gruiformes (Bonaparte, 1854), an order within class Aves.

Gruiformes is an order of birds according to traditional classifications, e.g. Wtmore 1960. That its members are one anothers' closests relatives is an idea couched on traditional morphological characters. Yet, there are no characteristics that diagnostically identify the group. Gruiformes also have long been considered by many authoritative ornithologists to be an artificial group of odd birds whose relationships are simply unresloved. The latter idea is couched as much in comparative anatomy as the former, but it is also supported by a diversity of molecular genetic data. Since the monophyly or polyphyly (realtedness or unrelatedness) of this "order" is not agreed upon by the professional community, it seems best to allow the advocates of the respective hypotheses to elaborate their own narratives to stand side by side for the consideration and comparison of the public community at large.

The traditional view:

Gruiformes is a diverse order constituting a morphologically disparate though genetically homogenous (relatively speaking) assemblage of paludicoline, aquatic and terrestrial birds, including the families Eurypgidae (subitterns), Otididae (bustards), Gruidae (cranes), the monotypic Aramidae (the limpkin), Heliornithidae (sun-grebes), Psophiidae (trumpeters), Cariamidae (seriemas), Rhynochetidae (the kagu), Rallidae (rails and allies), and the enigmatic Mesitornithidae (mesites, monias, roatelos). Defining the gruiform assemblage has historically been difficult, and classifications of these birds have altered widely. Nevertheless, there is a preponderance of morphological (Cracraft 1981) and molecular evidence (Sibley & Ahlquist 1990) to substantiate the assertion that the gruiform assemblage is holophyletic. The internal relationships of the order are contentious. Sibley & Ahlquist (1990) argued that the basal divergence amongst gruiform birds was between suborders Grui, bracketing cranes and allies, and Ralli, including the diverse Rallidae and the Mesitornithidae. The major radiation within Grui is represented by infraorder Gruides, including the Gruoidea and the famed Cariamae (Cariamida of Sibley & Ahlquist's 1990 classification). Sibley & Ahlquist (1990) argued that Aramidae are most closely related to Heliornithidae, but this stands in stark contrast to nearly two centuries of morphological analysis which indicates that the limpkin is closest to Gruidae (e.g., Cracraft 1973b, Olson 1985a, Feduccia 1996) and thus this novel relationship must be considered with a healthy dose of skepticism. Gruidae cleaves into two subfamilies, the Balearicinae, represented by the two extant species of crowned crane (Balearica spp.), the most basal cranes, and sister group to Gruinae, the gruine cranes (e.g., Grus). This topology has been recovered in multiple morphological and molecular analyses (e.g., Krajewski 1989, Sibley & Ahlquist 1990, Feduccia & Voorhies 1992, Feduccia 1996) and is robustly supported by the fossil record of cranes. The phylogenetic relationships of the vast cariamid assemblage, which includes the remarkable South American phorusrhacid birds from the Tertiary, remains highly contentious (Mayr 2002). The Psophiidae are the closest living relatives to the Cariamidae (Sibley & Ahlquist 1990, Mayr 2002), a hypothesis which has been advocated for some time (e.g., Gadow 1893) and has been corroborated by the fossil record of these birds (see A new gruiform from Messel). Olson (1973) reviewed the classification of Rallidae and this proposal was by default accepted by Sibley & Ahlquist in their 1990 work for lack of proper DNA sequences to assess Olson's phylogeny.

The origins of the gruiform assemblage are, as in most matters concerning higher avian phylogeny, contested. Various relationships have been postulated for the gruiform assemblage, but starting with Huxley's 1867 classification, it has been noted that there are an impressive array of characters shared by Charadriiformes and Gruiformes. Huxley himself felt that Otididae represented a morphological link to the Charadriidae (plovers and lapwings), a view reiterated by Parker (1868). Garrod (1873d) argued that Burhinus was the closest living relative of the bustards and thus transferred Burhinidae to his Otididae. Furbringer (1888) in his magisterial analysis of avian relationships bolstered the gruiform/charadriiform link and argued that Eurypyga substantiated this hypothesis. Beddard (1890a) reiterated this viewpoint, drawing favorable comparisons between Burhinus and Psophia. Beddard further argued this point in his 1898 analysis of bird relationships. Lowe (1931a) argued that there was no sufficient grounds for distinguishing Gruiformes from Charadriiformes and combined the orders within "Telmatomorphae," a conclusion which though stressing the relationships between these two assemblages was generally not accepted. Ridgway & Friedmann (1941) catalogued a number of morphological traits of Gruiformes and charted their distribution amongst possible gruiform ancestors and descendants, noting similarities with Charadriiformes and Galliformes. Based on the fossil record of the gruiform assemblage, Hildegarde Howard (1950) supported a charadriiform ancestry for the gruiform birds. Olson (1985a) and Feduccia (1996) both supported the charadriiform affinity of Gruiformes. Most interestingly, is that the Pedionomidae (plains-wanderers) of Australia have been re-classified as charadriiform birds (Olson & Steadman 1981) after classically being considered gruiform birds. Sibley & Ahlquist (1990) and Feduccia (1996) both concurred with this assessment. Olson (1985a) and Feduccia (1996) have argued that Otididae may be more closely related to the Charadriiformes, a viewpoint that has surfaced from time to time in the literature, yet there is no compelling evidence to indicate a charadriiform/bustard nexus and classically the similarities between the two have been attributed to convergence. Given these data, the most convincing candidates for the ancestry of gruiforms must be considered to be the vast charadriiform assemblage.

The fossil record of Gruiformes is among the richest of all birds, and includes some of the most famous of all extinct Aves--Phorusrhacidae, the terror birds of the pampas. The cariamids have a diverse fossil record, radiating extensively in the Paleogene and represented by a number of cursorial, flightless forms convergent on some falconiform birds (e.g., Bathornis grallator). Messelornithidae, an amazing component of this gruiform radiation, represent by far the most abundant avian remains from the famed Eocene Messel oil shales of Germany. Gruiformes also underwent an extensive adaptive radiation in the steppes and plains of Mongolia and western Asia, represented by the geranoidid-eogruid-ergilornithid assemblage (Olson 1985a). These remarkable birds were once implicated in the ancestry of ostriches (e.g., Olson 1985a) but given other data (e.g., Houde 1988) this suggestion has generally been abandoned. Nonetheless the ergilornithids represent a remarkable example of convergence, mimicking the didactylous condition of Struthio, the only other bird in which this character state is known. Indeed terrestrial Gruiformes were a crucial part of the Tertiary aviary in multiple locatlies if the abundance and diversity of their remains are any indication (Cracraft 1968, 1983, Feduccia 1980, 1996). This major radiation had largely occurred by the Lower Eocene, and argues for a rapid gruiform diversification post-KT Boundary (similar to that argued for by Feduccia 1995b, 1996, 1999).

Gruiformes is today represented by scattered and relictual lineages, evidencing a former widespread distribution. For instance, numerous gruiform taxa are endemic including the New Caledonian kagu (Rhynochetus jubatus) and the trumpeters of the Amazon basin, to name but a few. They are also more prone to the secondary loss of flight than any other order of extant birds, which makes the group of extreme interest. It has been noted that gruiformes are generally altricial as chicks with an underdeveloped flight architecture (e.g., contrast with Galliformes) and thus are ideal candidates for the neotenic loss of flight (Olson 1973, Feduccia 1996).

Alternative hypotheses:

Section in progress, to be updated:

Hypothesis of Gruiform non-monophyly based on morphology: sunbittern - herons seriemas - secretarybird or hoatzin mesites - doves rails - jacanas bustards - seedsnipes plains-wanderer - seedsnipes

Hypotheses of Gruiform non-monophyly based on DNA sequence analysis: mtDNA evidence for relationship of cranes-rails to the exclusion of kagu and seriema nuclear DNA (RAG-1 and beta-fibrinogen intron 7) evidence that hemipodes are Charadriiformes nuclear DNA (beta-fibrinogen intron 7 and multilocus)evidence for the inclusion of sunbittern, kagu, and mesites in "Metaves", but other gruiforms in "Coronaves"

Hypotheses of Gruiform non-monophyly based on DNA-DNA hybridization plains-wanderer - seedsnipes rooting of "gruiform" subtree in Aves supertree by incorrectly presumed outgroup

References:

  1. Beddard, F. E. 1890. On the structure of Psophia and on its relations to other birds. Proceedings of the Zoological Society of London 1890: 329-341.
  2. Beddard, F. E. 1898a. The structure and classification of birds. Longmans, Green and Co., London.
  3. Cracraft, J. 1968. Systematics and evolution of the Bathornithidae (Aves, Gruiformes), with remarks on the relationships of the suborder Cariamae. American Museum Novitates 2326: 1-46.
  4. Cracraft, J. 1973b. 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.
  5. Cracraft, J. 1981. Towards a phylogenetic classification of the recent birds of the world (class Aves). Auk 98: 681-714.
  6. Cracraft, J. 1983. Cladistic analysis and vicariance biogeography. American Scientist 71: 273-281.
  7. Feduccia, A. 1980. The Age of Birds. Harvard University Press, Cambridge.
  8. Feduccia, A. 1995b. Explosive evolution in Tertiary birds and mammals. Science 267: 637-638.
  9. Feduccia, A. 1996. The Origin and Evolution of Birds, First Edition. Yale University Press, New Haven.
  10. Feduccia, A. 1999. The Origin and Evolution of Birds, Second Edition. Yale University Press, New Haven.
  11. Feduccia, A. & Voorhies, M. R. Crowned cranes (Gruidae: Balearica) in the Miocene of Nebraska. Los Angeles County Museum of Natural History, Science Series 36: 239-248.
  12. Furbringer, M. 1888. Untersuchungen zur Morphologie und Systematik der Vogel. Vols. 1, 2. 1751 pp. Von Holkema, Amsterdam.
  13. Gadow, M. 1893. Vogel. II. Systematischer Theil. In: Bronn's Klassen und Ordnungen des Thier-Reichs, vol. 6(4). C. F. Winter, Leipzig.
  14. Garrod, A. H. 1873d. On certain muscles of the thigh of birds and on their value in classification. Part I. Proceedings of the Zoological Society of London 1873: 626-644.
  15. Houde, P. 1988. Paleognathous birds from the early Tertiary of the Northern Hemisphere. Nuttal Ornithological Club, Cambridge.
  16. Howard, H. 1950. Fossil evidence of avian evolution. Ibis 92: 1-21.
  17. Huxley, T. H. 1867. On the classification of birds; and on the taxonomic value of the modifications of certain of the cranial bones observable in that class. Proceedings of the Zoological Society of London 1867: 415-472.
  18. Krajewski, C. 1989. Phylogenetic relationships of the cranes (Gruiformes: Gruida) based on DNA hybridization. Auk 106: 603-618.
  19. Lowe, P. R. 1931a. On the relations of the Gruimorphae to the Charadriimorphae and Rallimorphae, with special reference to the taxonomic position of Rostratulidae, Jacanidae, and Burhinidae (Oedicenmidae olim); with a suggested new order (Telmatomorphae). Ibis 73: 491-534.
  20. Mayr, G. 2002. A new specimen of Salmila robusta (Aves: Gruiformes: Salmilidae n. fam.) from the Middle Eocene of Messel. Palaontologische Zeitschrift 76(2): 305-316.
  21. Olson, S. L. 1973. Evolution of the rails of the South Atlantic islands (Aves: Rallidae). Smithsonian Contributions to Zoology 152: 1-53.
  22. Olson, S. L. 1985a. The fossil record of birds. In: Farner, D. S., King, J. R., & Parkes, K. C., Avian Biology, vol. 8, 79-252.
  23. Olson, S. L. & Steadman, D. 1981. The relationships of the Pedionomidae (Aves: Charadriiformes). Smithsonian Contributions to Zoology 337: 1-25.
  24. Parker, W. K. 1868. A monograph on the structure and development of the shoulder-girdle and sterum in the vertebrata. R. Hardwicke for the Ray Soc., London.
  25. Ridgway, R. & Friedmann, H. 1941. The birds of North and Middle America. Bulletins of the United States National Museum 50, pt. 6, 882 pp.
  26. Sibley, C. G. & Ahlquist, J. E. 1990. Phylogeny and Classification of Birds: A Study in Molecular Evolution. Yale University Press, New Haven.

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