Rallus carvaoensis, Alcover, Josep Antoni, Pieper, Harald, Pereira, Fernando & Rando, Juan Carlos, 2015

Alcover, Josep Antoni, Pieper, Harald, Pereira, Fernando & Rando, Juan Carlos, 2015, Five new extinct species of rails (Aves: Gruiformes: Rallidae) from the Macaronesian Islands (North Atlantic Ocean), Zootaxa 4057 (2), pp. 151-190 : 181

Rallus carvaoensis

R. carvaoensis n. sp. belongs to the group of species that combine robust leg bones (in this case, excluding the femur) with reduced wings. It is smaller than R. lowei n. sp. from Madeira and larger than R. minutus n. sp. from São Jorge.

Although no complete skulls are available, the premaxilla is longer and more curved than in R. aquaticus and R. montivagorum n. sp. (see Figure 8 B–E). The bill shape was probably similar to that of R. minutus n. sp. R. carvaoensis n. sp. has a shorter coracoid and humerus than R. montivagorum n. sp. from Pico (12% and 19% shorter, respectively; U = -2.448; p = 0.007, U = -2.714; p = 0.002) and R. aquaticus (26% and 29% shorter, respectively; U = -2.833; p <0.001, U = -2.842; p <0.001). The available forelimb bones (humerus and carpometacarpus) are around 30% smaller than in R. aquaticus , while the femur, tibiotarsus and tarsometatarsus are 12%, 17% and 26% smaller than in R. aquaticus , respectively.

The humerus is longer (9%) than in R. minutus n. sp. The carpometacarpus is smaller than in the Pico rail (21%) and in R. aquaticus (30%) (Table 1), and it is longer than in R. minutus n. sp. (35%). Despite all the known ulnae being incomplete, its extreme reduction in size is clear based on their width measurements (see Table 1).

The femur length of R. carvaoensis n. sp. is close to R. lowei n. sp. and R. adolfocaesaris n.sp (Table 1). The ANOVA of femur length (trait 17) of the Rallus from São Miguel, Pico, and R. aquaticus , reveal significant differences among them (F2,66 = 75,664; p <0.001). These differences were significant between R. carvaoensis n. sp. and R. aquaticus (p <0.001) (12%), but not between R. carvaoensis n. sp and the Rallus from Pico (p = 0.601). The tibiotarsus of R. carvaoensis n. sp. is longer than in R. minutus n. sp. (14%), slightly longer than in R. adolfocaesaris n. sp., close in length to R. lowei n. sp. and the Rallus from Pico, and smaller (17%) than in R. aquaticus .

The ANOVA of the tibiotarsus distal width (trait 25) identified morphological differences between R. carvaoensis n. sp. and R. adolfocaesaris n. sp. (p = 0.007), R. aquaticus (p <0.001), and R. minutus n. sp. (p = 0.002), but not with Rallus montivagorum n. sp. (p = 0.262).

The MANOVA of tarsometatarsus lengths (total length and distal width; traits 26 and 29) showed that R. carvaoensis n. sp. has a shorter tarsometatarsus than in R. lowei n. sp. (11%) (p = 0.003), R. montivagorum n. sp. (11%) (p <0.001), and R. aquaticus (26%) (p <0.001), but it is longer than in R. minutus n. sp. (p <0.001). The tarsometatarsus distal width of R. carvaoensis n. sp. is shorter than in R. lowei n. sp. (p <0.001) and R. aquaticus (p <0.001), but similar to R. montivagorum n. sp. (p = 0.795) and R. minutus n. sp. (p = 0.871). The length and distal width of the tarsometatarsus of R. carvaoensis n. sp. is similar to R. adolfocaesaris n. sp. (U = - 1,837; p = 0.085, U = - 1,829; p = 0.067), whereas its proximal width is narrower than in R. lowei n. sp. (U = 3.337; p <0.001), but similar to R. adolfocaesaris n. sp. (U = - 0,155; p = 0.94), R. montivagorum n. sp. (U = - 0,907; p = 0.388), R. minutus n. sp. (U = -1.533; p = 0.145) and R. aquaticus (U = - 1,911; p = 0.057).

The leg bones of R. carvaoensis n. sp. indicate that it was more stout than Rallus aquaticus . The low humerusto-femur length ratio (0.76) –the smallest among all the species here described—is clearly indicative of flightlessness. The short stout tarsometatarsus (relative to the femur) suggests that R. carvaoensis n. sp. could be a slow-pace runner

Figures

FIGURE 8. Skulls and premaxillae of Rallus spp. A, Rallus aquaticus IMEDEA 12474. B, Rallus carvaoensis n. sp. IMEDEA 104069. C, Rallus carvaoensis n. sp. MCMa 1801.013. D, Rallus carvaoensis n. sp. MCMa 1804.013. E, Rallus carvaoensis n. sp. MCMa 1812.013. F, Rallus montivagorum n. sp., DZUL 3185, (paratype). G, Rallus lowei n. sp., MMF 43421, (paratype). H, Rallus adolfocaesaris n. sp., MMF 43450, Porto (paratype). I, Rallus minutus n. sp., MCMa 1950.014. 1, dorsal view. 2, ventral view. 3, lateral view. Scale bar: 2 cm.