Raphina
The Raphina are a clade of extinct flightless birds formerly called didines or didine birds. 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. Historically, many different groups have been named for both the dodo and the Rodrigues solitaire, not all grouping them together. Most recently, it is considered that the two birds can be classified in Columbidae, often under the subfamily Raphinae. The first person to suggest a close affinity to the doves was Johannes Theodor Reinhardt, whose opinions were then supported by Hugh Edwin Strickland and Alexander Gordon Melville.
Recent extractions of DNA from the dodo and Rodrigues solitaire, as well as 37 species of doves, has found where in Columbidae the raphines should be placed. Raphines are not the most primitive columbid, instead they are grouped with the Nicobar pigeon as their closest relative, with other closely related birds being the crowned pigeons and tooth-billed pigeon. A third raphine, Raphus solitarius, is now considered to be an ibis in the genus Threskiornis.
Both the Rodrigues solitaire and the dodo are now extinct. A common threshold of the extinction of the dodo is 1662, but some possible sightings had been made as late as 1688. The last sighting with a description was in 1662, but a statistical analysis by Roberts and Solow found that the extinction of the dodo was in 1693. The Rodrigues solitaire was killed off later than the dodo. The IUCN uses an extinction date of 1778 for the solitaire, although a more probable date would be in the 1750s or 1760s. Both birds became extinct as a consequence of human hunting and the introduction of mammals that ate the birds and their eggs.
Classification
This clade is part of the order Columbiformes and contains the monotypic genera Pezophaps and Raphus. The former contains the species Pezophaps solitaria, the latter the dodo, Raphus cucullatus. These birds reached an impressive size as a result of isolation on islands free of predators, in accordance with Foster's rule.History of classification
Historically, the dodo was assigned the genus Didus, now a junior synonym of Raphus. In 1848, a new species within the now defunct genus Didus, D. nazarenus, was named by Hugh Edwin Strickland and Alexander Gordon Melville. To house their new species, as well as the other species known at the time, Strickland and Melville named the subfamily Didinae. In 1893 three species were assigned to the group Pezophaps solitarius, Didus ineptus, and the possible species Didus borbonicus. Today, only two raphine species are known, with Didus ineptus becoming a junior subjective synonym of Raphus cucullatus; Didus? borbonicus now classified as the ibis Threskiornis solitarius; and Didus nazarenus being identified as synonymous with Pezophaps solitarius.A suborder named in 1893 by Sharpe, Didi was defined as a group including only the massive birds, that were sister to Columbidae, from the Mascarene Islands of Mauritius, Réunion, and Rodrigues. Features grouping Didi with Columbidae were the angle of the mandible and the hook at the end of the beak.
In 1811, Johann Karl Wilhelm Illiger created a new family for the genus Didus. He named the family Inepti, and in it included only Didus ineptus, now a synonym of Raphus cucullatus. Illiger concluded that the dodo was related to ostriches and rheas, and so placed Inepti in the order Rasores, as the sister family to Gallinacei, Epollicati, Columbini, and Crypturi.
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. This view was met with ridicule, but later supported by Strickland and Melville, who suggested the common descent of the Rodrigues solitaire and the dodo in 1848, after dissecting the only known dodo specimen with soft tissue and comparing it with the few solitaire remains then available. Strickland stated that although not identical, these birds shared many distinguishing features in the leg bones, features which were otherwise known only in pigeons.
The raphines were sometimes separated as a distinct family Raphidae, and their affinities were for long uncertain. They were initially placed in 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. Many different affinities have historically been suggested for the dodo, including that it was a small ostrich, a rail, an albatross, or a vulture.
Phylogeny
Comparison of mitochondrial cytochrome b and 12S rRNA sequences isolated from a dodo tarsal and a Rodrigues solitaire femur supported their close relationship and their placement within the family of pigeons and doves Columbidae. The genetic evidence was interpreted as suggesting the Southeast Asian Nicobar pigeon to be their closest living relative among 35 analyzed species of pigeons and doves, followed by the crowned pigeons of New Guinea and the superficially dodo-like tooth-billed pigeon from Samoa. The genus of the latter is Didunculus, and it was called "dodlet" by Richard Owen. The following cladogram, from Shapiro and colleagues, shows the position of the dodo and solitaire within the pigeon and dove family.A similar cladogram was published in 2007, inverting the placement of Goura and Didunculus and including the pheasant pigeon and the thick-billed ground pigeon at the base of the clade. Based on behavioural and morphological evidence, Jolyon C. Parish proposed that the dodo and Rodrigues solitaire should be placed in the Gourinae subfamily along with the Goura pigeons and others, in agreement with the genetic evidence. In 2014, DNA of the only known specimen of the recently extinct spotted green pigeon was analysed, and it was found to be a close relative of the Nicobar pigeon, and thus also the dodo and Rodrigues solitaire.
For many years the dodo and the Rodrigues solitaire were placed in a family of their own, the Raphidae, because their exact relationships with other pigeons were unresolved. Each was placed in its own monotypic family, as it was thought that they had evolved their similar features independently. Osteological and molecular data has since led to the dissolution of the family Raphidae, and the dodo and solitaire are now placed in the columbid subfamily Raphinae and tribe Raphini, along with their closest relatives. In 2024, the new subtribe Raphina was created to include only the dodo and the solitaire, and the authors proposed the vernacular name 'Mascarene giant ground doves' for them.
The "Réunion solitaire", long considered a third extinct didine bird, has turned out to be an ibis; it is now known as Threskiornis solitarius.
Divergence
The 2002 study indicated that the ancestors of the Rodrigues solitaire and the dodo diverged around the Paleogene-Neogene boundary. The Mascarene Islands, are of volcanic origin and are less than 10 million years old. Therefore, the ancestors of both birds probably remained capable of flight for a considerable time after the separation of their lineage. The lack of mammalian herbivores competing for resources on these islands allowed the solitaire and the dodo to attain very large sizes. The DNA obtained from the Oxford specimen is degraded, and no usable DNA has been extracted from subfossil remains, so the age of the groups divergence from other pigeons still needs to be independently verified. The dodo lost the ability to fly owing to the lack of mammalian predators on Mauritius. Another large, flightless pigeon, the Viti Levu giant pigeon, was described in 2001 from subfossil material from Fiji. It was only slightly smaller than the dodo and the Rodrigues solitaire, and it too is thought to have been related to the crowned pigeons.It has been estimated that the group containing the dodo and the Rodrigues solitaire diverged from genera like Goura about 1.5 million years ago. However, that estimate appears highly unlikely. It was estimated that the relatives of the two species moved to the island about 35 million years ago, when a land bridge between Nazareth or St. Brandon banks and Mauritius formed.
Description
Many of the skeletal features that distinguish the dodo and the Rodrigues solitaire, its closest relative, from 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 that they were underdeveloped and retained juvenile features. The skull, trunk and pelvic limbs were peramorphic, meaning that they changed considerably with age. The dodo shared several other traits with the Rodrigues solitaire, such as features of 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 solitaire's wrists.File:Edwards' Dodo.jpg|thumb|left|Famous depiction of a dodo with a lesser Antillean macaw, Martinique macaw, and red rail
As no complete dodo specimens exist, its external appearance, such as plumage and colouration, is hard to determine. Illustrations and written accounts of encounters with the dodo between its discovery and its extinction are the primary evidence for its external appearance. According to most representations, the dodo had greyish or brownish plumage, with lighter primary feathers and a tuft of curly light feathers high on its rear end. The head was grey and naked, the beak green, black and yellow, and the legs were stout and yellowish, with black claws. Subfossil remains and remnants of the birds that were brought to Europe in the 17th century show that they were very large birds, tall, and possibly weighing up to. The higher weights have been attributed to birds in captivity; weights in the wild were estimated to have been in the range. A later estimate gives an average weight as low as. This has been questioned, and there is still some controversy. It has been suggested that the weight depended on the season, and that individuals were fat during cool seasons, but less so during hot. The bird was sexually dimorphic: males were larger and had proportionally longer beaks. The beak was up to in length and had a hooked point. A study of the few remaining feathers on the Oxford specimen head showed that they were pennaceous rather than plumaceous and most similar to those of other pigeons.
The beak of the solitaire was slightly hooked, and its neck and legs were long. One observer described it as the size of a swan. The skull was long, flattened at the top with the fore and hind parts elevated into two bony ridges structured with cancellous. A black band appeared on its head just behind the base of the beak. The plumage of the Rodrigues solitaire was described as grey and brown. Females were paler than males and had elevations on the lower neck. Sexual size dimorphism in the solitaire is perhaps the greatest in any neognath. One group, probably the males, were considerably larger than the other, measuring in length and weighing up to, whereas the smaller group, probably females, were only and weighed. This is only 60% of the weight of a larger individual. Their weight may have varied substantially due to fat cycles, meaning that individuals were fat during cool seasons, but slim during hot seasons, and may have been as low as in the larger gender and in the smaller. Though male pigeons are usually larger than females, there is no direct evidence for the largest specimens actually being the males of the species, and this has only been assumed based on early works. Though the male was probably largest, this can only be confirmed by molecular sexing techniques, and not skeletal morphology alone.