Rodrigues rail
The Rodrigues rail, also known as Leguat's gelinote or Leguat's rail, is an extinct species of the rail family that was endemic to the Mascarene island of Rodrigues. The bird was first documented from life by two accounts from 1691–93 and 1725–26. Subfossil remains were later discovered and correlated with the old accounts in 1874, and the species was named E. leguati in Leguat's honour. It is generally kept in its own genus, Erythromachus, but has sometimes been assigned to the genus Aphanapteryx along with its close relative the red rail of Mauritius; their relationship with other rails is unclear.
The Rodrigues rail was about long and weighed at least. It was described as having grey plumage, a red beak, red legs, and a naked red patch around the eye. The beak was long and curved downwards. It was flightless and fed on tortoise eggs. It was described as being attracted to red objects, which humans exploited while hunting it. The Rodrigues rail is believed to have become extinct in the mid-18th century mainly because of predation by introduced cats and hunting.
Taxonomy
In 1848, the English zoologist Hugh Edwin Strickland called attention to a bird mentioned in the French traveller François Leguat's 1708 memoir A New Voyage to the East Indies about his stay on the Mascarene island of Rodrigues from 1691–93. Leguat was the leader of a group of nine French Huguenot refugees who settled on Rodrigues after they were marooned there. Leguat referred to the birds as "gelinottes", a name Strickland thought implied the grouse of Europe, though this was not consistent with the form of the beak described by Leguat. Strickland was unable to classify the bird further, but noted similarities with the dodo and kiwi, based on unidentified birds from Mauritius illustrated by the travellers Pieter van den Broecke and Sir Thomas Herbert, which he thought related. Strickland also noted similarities with a bird from Mauritius, which would later be identified as the red rail.File:First Erythromachus bones.jpg|thumb|left|First bones described in 1874; a tarsometatarsus, a fragmentary skull |alt=An illustration of bird bones laid out in rows
In 1874, the French zoologist Alphonse Milne-Edwards described subfossil bird bones from Rodrigues he had received via the British ornithologist Alfred Newton, which had been excavated under the supervision of his brother, Colonial Secretary Edward Newton. Milne-Edwards connected Leguat's account with three bones found in caves of the Plaine Corail region, Rodrigues. He recognised their similarity to those of the red rail, while noting it supposedly had a straighter beak. Milne-Edwards coined the generic name Erythromachus from the Greek words, "red", and, "battle", in reference to its attraction to red objects, and the specific name is in honour of Leguat.
The name Erythromachus was incorrectly explained as referring to the Erythraean sea by the American ornithologist Charles Wallace Richmond in 1908. The name Miserythrus, from "red" and "hatred", was used by A. Newton in 1874, and also refers to the rail's behaviour towards red, but as a newer name, it is a junior synonym. Milne-Edwards did not select a holotype specimen for the species from the bones he had loaned from Cambridge University Museum of Zoology for his study, but a syntype series was later listed from specimens there, presumably by A. Newton.
In 1875, A. Newton also identified a reference to the bird in the 1725–26 account of the French traveller Julien Tafforet, Relation de l'Ile Rodrigue, which had recently been rediscovered. In 1879, more fossils, including skulls, were described by the zoologists Albert Günther and E. Newton, who confirmed that the bird was a rail, and also noted that some specimens had beaks as curved as that of the red rail. In 1921, the American linguist Geoffroy Atkinson questioned the bird's existence, in an article that doubted the veracity of Leguat's memoir. The American ornithologist James Greenway suggested in 1967 that Leguat's description referred to wind-blown purple swamphens, since the word grey is sometimes used synonymously with blue in old descriptions. This idea has not been accepted by other commentators. Today, it is widely accepted that Leguat's memoirs represent credible observations of local birds in life. His observations on the local fauna are considered some of the first cohesive accounts of animal behaviour in the wild.
In 1999, the French palaeontologist Cécile Mourer-Chauviré and colleagues pointed out that a carpometacarpus bone assigned to the Rodrigues rail and illustrated by Günther and E. Newton in 1879 does not belong to a rail, and therefore not this bird. More subfossils have since been discovered, including an associated but incomplete skeleton with a complete skull and jaws found in Caverne Poule Rouge in 2005.
Evolution
Apart from being a close relative to the red rail, the relationships of the Rodrigues rail are uncertain and the two are commonly listed as separate genera, Aphanapteryx and Erythromachus, but have sometimes been united as species of Aphanapteryx. Günther and E. Newton first generically synonymised the two in 1879 because of their skeletal similarities. In 1945, the French palaeontologist Jean Piveteau found skull features of the two species different enough for generic separation, and in 1977, the American ornithologist Storrs L. Olson stated that though the two species were similar and derived from the same stock, they had also diverged considerably, and should possibly be kept separate. Based on geographic location and the morphology of the nasal bones, Olson suggested that they were related to the genera Gallirallus, Dryolimnas, Atlantisia, and Rallus. The American ornithologist Bradley C. Livezey was unable to determine the affinities of the Rodrigues and red rail in 1998, stating that some of the features uniting them and some other rails were associated with the loss of flight rather than common descent. He also suggested that the grouping of the Rodrigues and red rail into the same genus may have been influenced by their geographical distribution. Mourer-Chauviré and colleagues also considered the two as belonging to separate genera.Rails have reached many oceanic archipelagos, which has frequently led to speciation and evolution of flightlessness. According to the British researchers Anthony S. Cheke and Julian P. Hume in 2008, the fact that the red rail lost much of its feather structure indicates it was isolated for a long time. These rails may be of Asian origin, like many other Mascarene birds. In 2019, Hume supported the distinction of the two genera, and cited the relation between the extinct Mauritius scops owl and the Rodrigues scops owl as another example of the diverging evolutionary paths on these islands. He stated that the relationships of the Rodrigues and red rails was more unclear than that of other extinct Mascarene rails, with many of their distinct features being related to flightlessness and modifications to their jaws due to their diet, suggesting a long period of isolation. He suggested their ancestors could have arrived on the Mascarenes during the middle Miocene at the earliest, but it may have happened more recently. The speed with which these features evolved may also have been affected by gene flow, resource availability, and climate events. Flightlessness can evolve rapidly in rails, sometimes repeatedly within the same groups, as in Dryolimnas, so the distinctness of the Rodrigues and red rails may not have taken long to evolve; some other specialised rails evolved in less than 1–3 million years. Hume suggested that the two rails were probably related to Dryolimnas, but their considerably different morphology made it difficult to establish how. In general, rails are adept at colonising islands, and can become flightless within a few generations in environments without predators, yet this also makes them vulnerable to human activities.
Description
The Rodrigues rail was about long, smaller than the red rail, but with proportionally longer wings. It may have weighed at least. Subfossil remains exhibit a large variation in size, which may reflect sexual dimorphism. It had bright grey plumage, perhaps flecked with white. Its beak and legs were red, and it had a red, naked area around its eyes. The cranium of the Rodrigues rail was slightly elongated, convex in every direction, and compressed from top to bottom in side-view. The cranium was medium-sized among Mascarene rails, long and wide. It had a narrow, long frontal region, at its least width.The beak was long and curved downwards as in the red rail, but the narial openings were longer. The premaxilla that comprised most of the upper bill was long, shallow in side-view, with a narrow nasal bone, and its total length was almost 60% longer than the cranium. The culmen of the beak was almost straight above the nostril, and the nasal bone was slightly longer than the cranium. The beak was up to long, the lower jaw up to long, and at its greatest depth. The narial opening was very long, 66% of the rostrum's length. There were foramina on the upper bill, which did not extend to the front edge of the narial opening. The mandible was long and narrow, ending in a sharp point, with the length of the mandibular symphysis being about 65% of the cranium's length. The mandible had large, deep set foramina, which ran almost up to a deep sulcus at the centre of the mandible. Günther and Newton stated that the examined beaks varied greatly in size and shape; some specimens had short and almost straight beaks, while others had much longer beaks that were prominently curved. These writers were unsure whether this was related to the overall size of an individual bird or to sexual dimorphism. Livezy was unable to confirm the idea that the differences in the beaks reflected dimorphism in 2003, but thought it probable. Hume examined all available upper beaks in 2019, but found no differences in curvature.
The bones associated with the forelimbs were generally small in proportion to the bird. The scapula was small and narrow, and long. The coracoid was short but wide, and the sternum was also small. The humerus was very small, its shaft was curved from top to bottom, and it ranged from. The radius and ulna were short, and the latter was and strongly arched from top to bottom, ranging from. The pelvis was large and strongly built in proportion to the size of the bird, was long, wide at the front, and wide at the back. The hindlimb elements were generally very robust. The femur was very robust, with a curved shaft, and ranged from in length. The tibiotarsus was short but robust, and ranged from. The fibula was also short and robust. The tarsometatarsus was short but very robust, ranging from long. The proportions of the legs, pelvis and sacrum of the Rodrigues and red rail were generally similar. The Rodrigues rail differed from the red rail by having a broader and shorter skull, longer and lower nostrils, a proportionately longer humerus, a shorter, stouter femur, as well as a considerably different plumage, based on early descriptions. The Dutch ornithologist Marc Herremans suggested in 1989 that the Rodrigues and red rails were neotenic, with juvenile features such as weak pectoral apparatuses and downy plumage.