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Description
The members of the rail family (Rallidae) have frequently colonized islands across the entire world. Due to their poor flight abilities, they tend evolve flightlessness frequently and rapidly, and as a result many island rails species are flightless. In fact, out of the aprox. 150 species of extant and recently extinct rails, 31 were fightless. Sadly, this characteristic has proved to be problematic when humans arrive to these islands, and many of these flightless rails have faced extinction in the last centuries as people colonized their habitats.

At the end of 2015 a paper was published describing 5 new species of rails that inhabited the Atlantic archipelagos of Madeira and Azores. Presumably descending from the Eurasian rail (Rallus rallus), these birds showed different degrees of adaptation to their island environments, and can be classified in 2 groups: some of the rails were quite similar to their mainland counterpart, with slightly reduced sizes and shortened wings, while the others were smaller, stockier and with shorter wings. All of them went extinct in recent times, probably caused by the arrival of humans. Following the same order shown in the drawing:

a) Rallus montivagorum: with numerous remains found on the island of Pico (Azores), this is the largest species of the group (almost the same size as the Eurasian rail), and the only one that was able to fly. It would have looked very similar to the mainland counterpart, but with a slightly smaller size.

b) Rallus minutus/nanus: found in the island of São Jorge (Azores), this is the smallest species of the group, with a size close to the extant Inaccesible Island rail (found in Inaccesible Island, close to Tristan da Cunha, in the South Atlantic). Its beak was curved downwards and its legs were way stockier than those of the mainland rails. While the species was originally described as minutus, the authors later proposed the name nanus, as Rallus minutus was already planned for another rail species

c) Rallus carvaoensis: the remains of the species were found in the island of São Miguel (Azores). A bit larger than R. minutus, the beak of this species was also curved. Proportionally to its legs, its wings are the shortest among all the species shown here

d) Rallus lowei: this species found in the island of Madeira belonged to the group of small and stocky rails along with R. carvaoensis and R. minutus, being the largest and stockiest of the bunch

e) Rallus adolfocaesaris: slightly smaller than the species of Pico, this bird lived in the island of Porto Santo (Madeira). Despite being close in size to their volant relatives, this species was probably flightless

f) Rallus sp.: more rail remains have been found in many islands across both archipelagos, but they have not been assigned to any particular species, at least yet. One interesting speciment discovered in the island of Terceira (Azores) was found preserved in 3D with impressions of feathers, as a result of being silified: the bird died in an environment rich in silica, which shortly after the death of the animal encrusted the carcass and prevented decomposition

The authors of the paper describing these species also wondered why there isn't any rail species in the Canary Islands, which are closer to Africa; they suggested that, due to the presence of native rodents in the eastern and central islands of the archipelago, rails didn't get to establish there

Note: The archipelagos are not drawn to scale (neither the distance between them)

Description
The members of the rail family (Rallidae) have frequently colonized islands across the entire world. Due to their poor flight abilities, they tend evolve flightlessness frequently and rapidly, and as a result many island rails species are flightless. In fact, out of the aprox. 150 species of extant and recently extinct rails, 31 were fightless. Sadly, this characteristic has proved to be problematic when humans arrive to these islands, and many of these flightless rails have faced extinction in the last centuries as people colonized their habitats.

At the end of 2015 a paper was published describing 5 new species of rails that inhabited the Atlantic archipelagos of Madeira and Azores. Presumably descending from the Eurasian rail (Rallus rallus), these birds showed different degrees of adaptation to their island environments, and can be classified in 2 groups: some of the rails were quite similar to their mainland counterpart, with slightly reduced sizes and shortened wings, while the others were smaller, stockier and with shorter wings. All of them went extinct in recent times, probably caused by the arrival of humans. Following the same order shown in the drawing:

a) Rallus montivagorum: with numerous remains found on the island of Pico (Azores), this is the largest species of the group (almost the same size as the Eurasian rail), and the only one that was able to fly. It would have looked very similar to the mainland counterpart, but with a slightly smaller size.

b) Rallus minutus/nanus: found in the island of São Jorge (Azores), this is the smallest species of the group, with a size close to the extant Inaccesible Island rail (found in Inaccesible Island, close to Tristan da Cunha, in the South Atlantic). Its beak was curved downwards and its legs were way stockier than those of the mainland rails. While the species was originally described as minutus, the authors later proposed the name nanus, as Rallus minutus was already planned for another rail species

c) Rallus carvaoensis: the remains of the species were found in the island of São Miguel (Azores). A bit larger than R. minutus, the beak of this species was also curved. Proportionally to its legs, its wings are the shortest among all the species shown here

d) Rallus lowei: this species found in the island of Madeira belonged to the group of small and stocky rails along with R. carvaoensis and R. minutus, being the largest and stockiest of the bunch

e) Rallus adolfocaesaris: slightly smaller than the species of Pico, this bird lived in the island of Porto Santo (Madeira). Despite being close in size to their volant relatives, this species was probably flightless

f) Rallus sp.: more rail remains have been found in many islands across both archipelagos, but they have not been assigned to any particular species, at least yet. One interesting speciment discovered in the island of Terceira (Azores) was found preserved in 3D with impressions of feathers, as a result of being silified: the bird died in an environment rich in silica, which shortly after the death of the animal encrusted the carcass and prevented decomposition

The authors of the paper describing these species also wondered why there isn't any rail species in the Canary Islands, which are closer to Africa; they suggested that, due to the presence of native rodents in the eastern and central islands of the archipelago, rails didn't get to establish there

Note: The archipelagos are not drawn to scale (neither the distance between them)