Fossil Vertebrates from the Bahamas

SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY • NUMBER 48 Fossil Vertebrates from the Bahamas Storrs L. Olson EDITOR SMITHSONIAN INSTITUTION PRESS City of Washington 1982 ABSTRACT Olson, Storrs L., editor. Fossil Vertebrates from the Bahamas. Smithsonian Contributions to Paleobiology, number 48, 65 pages, 12 figures, 1982.•The three papers in this volume summarize the previous literature on fossil vertebrates from the Bahamas, provide revisions of the previously described fossil specimens, include identifications of newly collected material, and discuss changes in the late Pleistocene environment of the Bahaman archipelago. Olson and Pregill review the history of fossil exploration in the Bahamas, describe the known fossil localities, and briefly discuss the depauperate mammalian fauna. Pregill reviews the Pleistocene herpetofauna of New Providence Island, which is similar to that found on the island today, the only extinct taxa being a tortoise (Geochelone), a crocodile (Crocodylus), an iguana (Cjclurd), and a gecko of the genus Anstelliger (previously misidentified as Tarentola). Taphonomy of the New Providence deposits and the zoogcographical patterns of the herpetofauna are discussed in relation to arid climatic conditions of the Wisconsinan glacial period. It is suggested that the establishment of a north-south rainfall gradient within the Bahamas has caused more extinctions in the wetter northern islands, whereas a more diverse herpetofauna persists in the drier southern islands. Olson and Hilgartner review the fossil record of birds from the Bahamas and propose the following changes in nomenclature: Calohierax quadratus = Buteo sp., Burhinus nanus = Burhinus bistriatus nanus, Glaucidium dickinsom = Athene cuniculana, Otus providentiae = Athene cunicularia, Bathoceleus hyphalus = Melanerpes superciliaris, Corvus wetmorei = Corvus nasicus. About 50% of the fossil avifauna of New Providence no longer occurs there and 40% is extinct in the Bahamas. Species composition indicates that the Bahamas in the late Pleistocene were drier and had more open savanna-like and broadleaf scrub habitats. Subsequent increases in rainfall caused habitat changes that resulted in extinction. The implications of this for modern ecological theories are discussed. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institutions annual report, Smithsonian Year. SERIES COVER DESIGN: The trilobite Phacobs rana Green. '^ Library of Congress Cataloging in Publication Data Main entry under title: Fossil vertebrates from the Bahamas. (Smithsonian contributions to paleobiology ; no. 48) Bibliography: p. Includes index. Contents: Introduction to the paleontology of Bahaman vertebrates / by Storrs L Olson and Gregory K. PregiH-Fossil amphibians and reptiles from New Providence Island, Bahamas ^ '7,S.',^8"'^J^- Pí^S'"-í^°^^'' ^"d ^"bfossil birds from the Bahamas / by Storrs L, Olson and William B. Hilgartner. 1. Vertebrates, Fossil-Addresses essays, lectures. 2. Paleonlology-Bahamas-Addresses e.s- ^aysjecturcs. I. Olson. Storrs L. II. Pregill, Gregory K. III. Hilgartner, William B. IV. QE701.S56 no. 48 |QE841] 560s [566'.097296] 81-13543 AACR2 ^ Contents Page Introduction to the Paleontology of Bahaman Vertebrates, by Storrs L. Olson and Gregory K. Pregill 1 Fossil Amphibians and Reptiles from New Providence Island, Bahamas, by Gregory K. Pregill 8 Fossil and Subfossil Birds from the Bahamas, by Storrs L. Olson and William B. Hilgartner 22 Literature Cited , , ...,.; 57 Index 61 III Fossil Vertebrates from the Bahamas Introduction to the Paleontology of Bahaman Vertebrates S tons L. Olson and Gregory K. Pregill In relation to their accessibility and their bio- Still poorly known. What we hope to provide is logical interest, the Bahamas have been relatively an updated baseline, a consolidated starting poorly studied. The present collection of papers point, from which our knowledge can be ex- attempts to bring together all that is as yet knov^in panded by future exploration. We would like to of one aspect of the natural history of the archi- think that we have shown that the little details of pelago, namely, vertebrate paleontology. This is anatomy, systematics, geology, and distribution largely an outgrowth of the more extensive and that are the building blocks of studies such as detailed collection of fossils obtained by Smith- those included here, eventually lead to significant sonian personnel in 1978 from the only truly generalizations of wider application. We will have productive vertebrate fossil locality yet discovered succeeded if this volume stimulates additional in the Bahamas•a sinkhole on the island of New research of this nature. Providence. In addition to analyzing this collec- The Bahamas form an extensive archipelago of tion, we have reviewed the literature on Bahaman low (maximum elevation 67 m), limestone islands fossil vertebrates and, with the exception of mam- and cays that are spread out over a distance of mals, we have re-examined and re-evaluated all nearly 1000 km. The larger islands are almost all of the previously reported fossil specimens. Par- in the northern part of the archipelago, where the ticularly in the case of birds, this has resulted in predominant vegetation type is pine forest (Pinus a number of taxonomic and nomenclatural caribaea). Rainfall (data from Buden, 1979; Young changes. Furthermore, we have attempted to in- and Cant, 1977) is greatest at the northern end of terpret our findings in the context of the more the archipelago, averaging 1300 to 1550 mm per general picture of Pleistocene biogeography and annum on Grand Bahama and Great Abaco, paleoecology that has emerged from our recent respectively. On the islands of the Great Bahama studies in the Antilles. Yet this does not alter the Bank, rainfall ranges from 1295 mm per annum fact that the fossil vertebrates of the Bahamas are on New Providence, in the north, to 920 mm per annum on Long Island, in the south. The south- Stons L. Olson, Department of Vertebrate Zoology, National Museum ern islands are quite dry (860 mm per annum on of Natural History, Smithsonian Institution, Washington, D. C. Mayaguana; 738 per annum on Great Inagua) 20560. Gregory K. Pregill, Natural History Museum, P.O. Box 1390, San Diego, California 92112. and vegetation here consists mainly of xeric 2 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY broadlcaf scrub. This rainfall gradient has impor- by more than an order of magnitude, from 11,406 tant zoogeographical ramifications (see other pa- km^ at present, to about 124,716 km^ in the pers in this volume). Wisconsinan (Buden, 1979). What is now the The most important factor in any consideration Great Bahama Bank constituted the bulk of the of the faunal history of the Bahamas is the effect land area and was separated from the Cuban that eustatic fluctuations in sea level in the Pleis- mainland by the 15-km-wide Old Bahama Chan- tocene would have had on the archipelago. Al- nel (Buden, 1979), thus presumably greatly facil- though there is not full agreement on the extent itating the dispersal of organisms from Cuba. At of Pleistocene changes in sea levels, a maximum the close of the Wisconsinan glaciation, 12,000 to lowering of 120 m during the height of the Wis- 13,000 years ago, sea levels began rising and consinan glaciation, 17,000 years ago, is a reason- much land was submerged, fragmenting the for- able estimate (Gascoyne et al., 1979). This would merly continuous large islands into many smaller have consolidated the 29 islands and 661 cays of ones. Today, most of the Great Bahama Bank is the present-day Bahamas into five major islands under 3 to 30 m of water. and several smaller ones (Figure 1). In addition, During the Wisconsinan glaciation, average a large island would have been created from the temperatures in the Bahamas would have been Cay Sal Bank, where there is now almost no dry cooler than at present by about 4° C (Lynts and land, and several islands would have formed from Judd, 1971), and the fossil record provides evi- the Mouchoir, Silver, and Navidad banks south- dence that climate and vegetation in general were east of Turks and Caicos, where there is no land altered as well (see discussions on pp. 18, 52). at all. Land area in the Bahamas was increased This evidence corroborates that from other is- 100 =1 FIGURE 1.•Map of ihe Bahama.s showing ihe extent of the present banks and thus the approximate configuration of the islands during the last glaciation. NUMBER 48 lands, showing that in Wisconsinan times, the frogs" were also included in this sample (G. M. West Indies as a whole were more arid, and open Allen, 1937:370), but these were never studied savanna and scrubland habitats were much more and they cannot now be located in the MCZ prevalent than today (Pregill and Olson, 1981). collections (Ernest Williams, pers. comm.). This Although the Bahamas are riddled with sink- may have been the "mass of small miscellaneous holes and caves, such as usually provide ideal sites bones" from which Williams forwarded speci- for the accumulation of fossil vertebrates, the mens to Koopman (1951), who identified two islands have been relatively little explored paleon- mandibles of bats, one of which belonged to a tologically. Barbour (in Lawrence, 1934) and species [Mormoops blainvillii) that no longer occurs Hecht (1955) lamented that many deposits of in the Bahamas. cave earth have been obliterated for use as fertil- Very little was originally recorded about the izer, but there must still be many unexploited Exuma site other than that fossils "were sorted sources of fossils awaiting discovery on the various out by Mrs. Vivienne Knowles from cave earth islands of the Bahamas. excavated for use as fertilizer . during the early Among the first fossil or subfossil vertebrates part of 1937" (Wetmore, 1937b;427). Although collected in the Bahamas were those obtained by Wetmore referred to the fossils as having come Froelich Rainey in 1933-34 for Yale University. from Great Exuma, G.

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