Raphinae

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Raphines
Temporal range: Recent
Skeletons of the Dodo and the Rodrigues Solitaire compared, not to scale
Conservation status
Extinct  (c.)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Columbiformes
Family: Columbidae
Subfamily: †Raphinae
Wetmore, 1930
Genera

† Pezophaps
† Raphus

Synonyms
  • Dididae Swainson, 1835
  • Didinae
  • Raphidae Poche, 1904 (unavailable)
  • Pezophabidae Hachisaka, 1953

The Raphinae are a subfamily of extinct flightless birds formerly called didines or didine birds.[lower-alpha 1] They inhabited the Mascarene Islands of Mauritius and Rodrigues, but became extinct through hunting by humans and predation by introduced non-native mammals following human colonisation in the 17th century.

Overview

This clade is part of the order Columbiformes and contains the monotypic genera Pezophaps and Raphus. The former contains the species Pezophaps solitaria (the Rodrigues Solitaire), the latter the Dodo, Raphus cucullatus. These birds reached an impressive size as a result of isolation on predatorless islands in accordance with Foster's rule.

Comparison of mitochondrial cytochrome b and 12S rRNA sequences suggests the Nicobar Pigeon (Caloenas nicobarica) is the closest living relative of the Dodo and the Rodrigues Solitaire. This does not actually imply a very close relationship, however, and at any rate, the molecular phylogeny of the Indo-Australian pigeons has yielded wildly differing results depending on the gene sequence analyzed.[1]

The following cladogram shows the Raphinae's closest relationships within columbidae, based on Shapiro et al., 2002.[2]


Goura victoria



Caloenas nicobarica

Pezophaps solitaria

Raphus cucullatus

Didunculus strigirostris



A similar cladogram was published in 2007, only differing in the inverted placement of Goura and Dicunculus.[3]

The Nicobar Pigeon (Caloenas nicobarica) is the closest living relative of the dodo and the Réunion Solitaire.

What appears certain, regardless of the closest living relative of the didines, is that they belong to a basal Indo-Australian radiation of pigeons. Apart from the didines, this includes such animals as the Goura crowned pigeons, the Pheasant Pigeon, Ducula and Ptilinopus, and the Nicobar Pigeon. Accordingly, until better material evidence of the didines' ancestry is available, they are here considered a subfamily of the Columbidae.

No good data is available for dating the group's evolution. Based on the data analyzed by Shapiro et al., they gave an estimate of 32–56 mya for the didine-Caloenas divergence. This may or may not be roughly correct; the more precise date of c. 43 mya is probably not, since the molecular clock was calibrated with a presumed penguin—Procellariiformes divergence that has since been invalidated by Waimanu. It is far more likely than not, however, that this group's origin lay in the Paleogene than in the Neogene, as indicated by the paleogeography of the Western Indian Ocean area, notably the Mascarene Plateau. This would support the view that the Columbidae are among the older landbird lineages among the Neoaves.

The "Réunion Solitaire", long considered a third extinct didine bird, has turned out to be an ibis; it is now known as Threskiornis solitarius.

The didines are often separated as a distinct family Raphidae, and their affinities were for long uncertain; they were initially placed within the ratites due to their peculiar, flightlessness-related apomorphies, and a relationship to the Rallidae has also been suggested. Osteological and molecular data, however, agrees that placement in the Columbidae is more appropriate.[4] Many different affinities have historically been suggested for the Dodo, including that it was a small ostrich, a rail, an albatross, or a vulture.[5]

In 1842, Johannes Theodor Reinhardt proposed they were ground doves, based on studies of a Dodo skull he had rediscovered in the royal Danish collection of Copenhagen.[6] This view was met with ridicule, but later supported by Hugh Edwin Strickland and Alexander Gordon Melville, who suggested the common descent of the Solitaire and the Dodo in 1848, after dissecting the only known Dodo specimen with soft tissue, and comparing them with the few Solitaire remains then available.[7] Strickland stated that although not identical, these birds shared many distinguishing features in the leg bones, which were otherwise only known in pigeons.[8]

Description

Skulls of the Dodo and Rodrigues Solitaire, the latter having been scaled up for comparison
The Dodo shared several traits with the Rodrigues Solitaire, its closest relative, such as features in the skull, pelvis, and sternum, as well as their large size. It differed in other aspects, such as being more robust and shorter than the Solitaire, having a larger skull and beak, a rounded skull roof, and smaller orbits. The Dodo's neck and legs were proportionally shorter, and it did not possess an equivalent to the knob present on the wrists of he Solitaire. Many of the skeletal features of the Dodo and the Solitaire that are unique among pigeons have been attributed to their flightlessness. The pelvic elements were thicker than those of flighted pigeons to support the higher weight, and the pectoral region and the small wings were paedomorphic, meaning they were underdeveloped and retained juvenile features. However, the skull, trunk and pelvic limbs were peramorphic, meaning that they changed considerably with age.[9]
Pezophaps solitaria, a digital recreation based on skeleton morphology and Leguat description.

The Dodo was anatomically similar to pigeons in many features; Strickland pointed to the keratinous portion of the beak being very short, with the basal part being long, slender, and naked. Other pigeons also have naked skin around their eyes, almost reaching the beak, as in Dodos. The forehead was high in relation to the beak, and the nostril was located low on the middle of the beak and surrounded by skin, a combination of features only shared with pigeons. The legs of the Dodo were generally more similar to terrestrial pigeons than other birds, both in the scales and skeletal features. Depictions of the large crop hinted at a relation with pigeons, a group where this feature is most developed among birds. Pigeons generally have very small clutch sizes, which agrees with the single egg said to have been laid by the Dodo. Like pigeons, the Dodo also lacked the vomer and septum of the nostrils. It also shared details in the lower jaw, zygomatic bone, the palate, and the hallux. The Dodo differed from other pigeons mainly in the small size of the wings, and the large size of the beak in proportion to the rest of the cranium.[8]

Footnotes

Explanatory notes

  1. ↑ From the dodo's obsolete genus name, Didus.

Citations

  1. ↑ Johnson & Clayton 2000; Shapiro et al. 2002.
  2. ↑ Shapiro et al. 2002.
  3. ↑ Pereira et al. 2007.
  4. ↑ Shapiro et al. 2002; Janoo 2005.
  5. ↑ Hume, Cheke & McOran-Campbell 2009.
  6. ↑ Reinhardt 1842–1843.
  7. ↑ Strickland 1859.
  8. ↑ 8.0 8.1 Strickland & Melville 1848.
  9. ↑ Livezey 1993.

References

External links

Wikispecies has information related to: Raphidae

Media related to Raphidae at Wikimedia Commons

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