AN ECOMORPHOLOGICAL REVIEW OF THE DODO (RAPHUS-CUCULLATUS) AND SOLITAIRE (PEZOPHAPS-SOLITARIA), FLIGHTLESS COLUMBIFORMES OF THE MASCARENE ISLANDS

This paper describes a morphological study of the dodo Raphus cucullat us and solitaire Pezophaps solitaria-extinct, flightless Columbiformes of the Mascarene Islands, Indian Ocean--based on mensural data from 3 87 skeletal elements, comparative data from four flighted species of C olumbidae, ancillary mensural data from other Columbiformes, and the l iterature. Raphus cucullatus and P. solitaria are characterized by gre at body size and substantially reduced pectoral limbs. Sexual size dim orphism is unusually great in both R. cucullatus and P. solitaria, and sexual dimorphism of P. solitaria may be the greatest of any carinate bird. Estimates of body mass (kg), based on femur lengths of flighted columbids and adjusted for flightlessness and seasonal deposition of fat, were: 21 and 17 for male and female R. cucullatus. and 28 and 17 for male and female P. solitaria, respectively. Pectoral reduction is greater in R. cucullatus than in P. solitaria, but both species are ch aracterized by differential shortening of wing elements, changes in th e sternum and scapulocoracoidal angle. R. cucullatus has disproportion ately long femora, short tarsometatarsi and long digits, whereas P. so litaria has disproportionately long tibiotarsi, short tarsometatarsi a nd short digits; relative shaft widths of leg elements are substantial ly greater in both R. cucullatus and P. solitaria than in flighted col umbids. As is typical of other birds, giantism of R. cucullatus and P. solitaria probably was associated with physiological changes, increas ed longevity, enhanced thermodynamic efficiency and improved capacity for fasting. Evidently both R. cucullatus and P. solitaria were primar ily frugivorous, and foraging-related morphological peculiarities incl ude an enlarged crop and the retention of 'gizzard stones'. Both speci es had clutch sizes of one, and egg masses of the flightless species a pproximated that predicted for a flighted columbid of equal size. Extr eme sexual dimorphism and territoriality of P. solitaria suggest that the species may have been polygynous and perhaps lek-breeding. The des cription of 'gigantic immaturity' in R. cucullatus by Strickland & Mel ville (1848) probably represents the first recognition of paedomorphos is in any species of bird. Pectoral underdevelopment and (in at least R. Cucullatus) comparatively 'juvenile' plumage in adults substantiate the role of paedomorphosis in the ontogeny of flightlessness in R. cu cullatus and P. solitaria; both species also were characterized by per amorphic skulls, trunks and pelvic appendages. The common assumption o f monophyly of the flightless species (i.e. Raphidae) lacks rigorous a nalytical support. In spite of the anthropogenous extinction of both s pecies, both R. cucullatus and P. solitaria were evolutionarily innova tive in ontogeny, morphological characters and life-history strategies .