Article

Deletion of the flightless ibis Xenicibis from the fossil record of Cuba

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Abstract

Shortly after the discovery of the first known flight-less ibis Apteribis glenos (Olson and Wetmore, 1976) in the Hawaiian islands (augmented later by a second species A. brevis Olson and James, 1991), the equally remarkable flightless ibis Xenicibis xympithecus (Olson and Steadman, 1977) was described from Jamaica. The description was based on some postcranial elements collected by H. E. Anthony during 1919-1920 in a cave deposit at Long Mile Cave, Trelawny Parish, Jamaica, and was followed by the description of a complete and well preserved humerus from Swansea Cave, St. Catherine Parish, Jamaica (Olson and Steadman, 1979). That Xenicibis might have been more widely distrib-uted was suggested by Acevedo-Gonzáles and Ar-redondo (1982), who recorded the genus from Cuba without mentioning localities or specimens. Ar-redondo (1984:6-7) then referred to "Xenicibis sp." a complete left humerus that he collected in Cueva de Pío Domingo, Sumidero, Pinar del Río, and kept in his private collection (OA 2969). He also noted some other appendicular elements of "Xenicibis sp.", including the distal end of a left tibiotarsus, a left tarsometatarsus, and one phalanx, all uncataloged at the time but now numbered OA 2970a, OA 2971, and OA 2972, respec-tively. These bones were found in association with the humerus, and the tarsometatarsus was described briefly. As part of my revisionary work on Arredondo's pa-leontological collection, I examined all of the above material and found that it does not represent the ge-nus Xenicibis, nor any other ibis (Threskiornithidae). Instead, these specimens agree in all their osteological characters with Aramus guarauna, the Limpkin (Arami-dae), a gruiform structurally similar to primitive cranes (see Olson 1985). Arredondo did not compare his material with Aramus, and his identification of the fossil specimens was based on comparisons with illus-trations of Xenicibis xympithecus (see Arredondo 1984). The Limpkin is widely distributed in the Neotropics and is fairly common in Cuba (Garrido and García Montañ a, 1975). It occurs in other Greater Antillean islands near bodies of water, rice fields, wooded flood-plains of rivers, and upland wet forest (Raffaele et al., 1998:265). The left humerus reported by Arredondo is inside the range variation of a small series of skeletons of Aramus guarauna from Cuba. It is partially covered by travertine, showing wear on the pectoral crest, inter-nal tuberosity, and bicipital crest. The other referred specimens show some differences in color and degree of mineralization in comparison with this last speci-men. The humerus of Xenicibis is characterized by a slender twisted shaft, bicipital crest reduced, pectoral crest reduced in area, thickened, and twisted; external tuberosity reduced and displaced distally, with a very deep and wide brachial depression (Olson and Stead-man, 1979). None of these flightless characters occurs in the Cuban humerus, which has a much shorter shaft that is less curved latero-medially and not twisted and flattened up to the mid point; the bicipital crest is well developed and not reduced, and placed proximally; the external tuberosity is more proximal and well de-fined, not distal and reduced; the pectoral crest is large and wide instead of short and thin. None of the other bones show diagnostic characters of the genus Xenicibis, such as very wide anterior in-tercondylar fossa and reduced supratendinal bridge in the tibiotarsus, or tarsometatarsus with two simple calcaneal ridges well separated by a deep groove (Ol-son and Steadman, 1977). In all respects these bones agree with Aramus guarauna, particularly in having a wide supratendinal bridge, a thin intercondylar sulcus of the tibiotarsus, and a tarsometatarsus with closed calcaneal ridges that form canals, among other char-acters. However, these specimens represent the first record of Aramus guarauna in Cuban Quaternary de-posits. The genus Xenicibis is known only in Jamaica, where its flightlessness evolved. Water barriers that con-stantly separated that island from Cuba throughout geological history (see Iturralde-Vinent and MacPhee, 1999) prevented the dispersal of this genus to Cuba. Acknowledgements.—I thank Prof. Oscar Arredondo for his assistance during the revision of his paleonto-logical collection. Gilberto Silva Taboada (Museo Na-cional de Historia Natural de Cuba) and Storrs L. Ol-son (Smithsonian Institution) made valuable comments on the first drafts of this manuscript.

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Preliminary diagnoses of two extraordinary new genera of birds from Pleistocene deposits in Hawaiian Islands
  • S L Olson
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Olson, S.L., and A. Wetmore. 1976. Preliminary diagnoses of two extraordinary new genera of birds from Pleistocene deposits in Hawaiian Islands. Proc. Biol. Soc. Wash. 89(18): 247-258.
The humerus of Xenicibis, the extinct flightless ibis of Jamaica
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A new genus of flightless ibis (Threskiornithidae) and other fossil birds from cave deposits in Jamaica
  • S L Olson
  • D W Steadman
Olson, S.L., and D. W. Steadman. 1977. A new genus of flightless ibis (Threskiornithidae) and other fossil birds from cave deposits in Jamaica. Proc. Biol. Soc. Wash. 90(2): 447-457.