Reprint Series ^OTTTIVr*!? ^7 Scnfpmhpr 19SA. Volume 233. DD. 1202-1204 ky\_/lILilVyrJ 12 epte be 86, , pp Paleoenvironment of the Earliest Hominoids: New Evidence from the Oligoc?ne Avifauna of Egypt STORRS L. OLSON AND D. TAB RASMUSSEN Copyright ? 1986 by the American Association for the Advancement of Science Paleoenvironment of the Earliest Hominoids: New Evidence from the OHgocene Avifauna of Egypt STORKS L, OLSON AND D. TAB RASMUSSEN Analysis of fossil birds from the Oligoc?ne Jebel Qatrani Formation in the Fayum depression of Egypt, site of the oldest known hominoid primates, allows precise paleoenvironmetltal reconstruction of the climatic and biotic conditions that influ- enced some of the earliest stages of hominoid evolution. Unlike the fossil mammals of the Fayum, which belong largely to extinct groups, most of the birds arc referable to living families, with some being close to modem genera. The avifauna consists mainly of aquatic species, with such forms as jacanas (Jacanidae) and shocbilled storks (Balaenicipitidae) indicating expanses of freshwater with dense floating vegetation. An avifauna closely analogous to that of the Fayum is found today only in a limited area of Uganda, north and west of Lake Victoria, a region of swampland bordered by forest and grasslands that presents marked faunal similarities to the environment inferred for the Egyptian Oligoc?ne. THE EARLY OLIGOCENE FOSSIL DE- posits of the Fayum depression in Eg)'pt are renowned for having pro- duced remains of the earliest known homi- noid primates (1^). The importance of these fossils to understanding evolution in the lineage thought to have given rise to Homo sapiens has focused interest on the nature of the environment in which these early primates lived, and the deposits have been subject to intensive modern paleonto- l?gica! collecting. Fossils come mainly from two intervals in the Jebel Qatrani Formation known as the upper and lower sequences that are probably early Oligocene in age (5, 6). Two of the Fayum primate genera, Ae- ?yptopithecHS and Propliopithecus, are homi- noids possibly ancestral to Homo and the modern great apes. The Fa\aim is the only place yet known where this stage in human ancestrv' is preserved, and a complete under- standing of the Fayum paleoenvironment is thus essential to interpreting the adaptations of these earliest apes. Controversy has surrounded die nature of the paleoenvironment of the Fayum depos- its and its implications for the adaptations of the primates that lived there. Kortlandt (7), in attempting to counter the belief that the area was forested and the primates arboreal- ly adapted, argued that the environment consisted of semiarid, almost treeless scrub- land, for which reason the Fayum primates must have been terrestrial. These arguments were vitiated by Bown et al. (8) based on evidence from Iitholog\', sedimentology, fossils of plants, vertebrates, and inverte- brates, and finally from the structural adap- tations of the primates themselves. They concluded that the Jebel Qatrani Formation was deposited near the coastline of the Tethyian seaway with interdigitating habi- tats of estuarinc mangroves, fresh and brack- ish fluviatile swamps, and forested flood- plains flourishing in a climate "typified by adequate, though probablv seasonal rainfall" (8). Fossil birds have hitherto played little part in the reconstruction of the paleoenviron- ment of the Fayum as only four taxa were recorded in the early collections. Among the modem collections is a greater variety' of fossil birds that have recently been smdied and identified (9). Although the total num- ber of diagnostic avian specimens is only 30, a minute fraction of the total number of vertebrate fossils obtained, some 17 to 19 species are represented, indicating great di- versity in the avifauna considering the small sample size. The significance of these speci- mens for paleoecological studies is greater than their scarcity would imply because S. L. Olson, Department of Vertebrate Zoology, Na- tional Museum of Natural Histoiv, Smithsonian Institu- tion, Washington, DC 20560. D. T. Rasmussen, Department of Anthropology, and Duke Primate Center, Duke Univcrsitv, Durham, NC 27706. SCIENCE, VOL. 233 most of t?ie fossil birds are dearly referable to living families and several may be closely related to living genera. In contrast, all of the more than 37 genera and al! but 6 of the 18 families of mammals described in the Fa\'um fauna arc extinct (4,10?12). For this reason it is difficult to make many direct inferences about the Fayum paleoenviron- ment from the mammalian fauna. The only birds in the fauna that cannot easily be referred to living families are two very problematic supposedly ratite-Uke forms {Stromeria and Eremopezus), and a distinctive new family of heron-like birds {9}. The last was probably aquatic, whereas the "ratite" identifications are based on such fragmentary material that nothing can be said about relationships or ecology. The remaining fossil birds, by analogy with liv- ing counterparts, provide two kinds of in- formation: {i) the habitat preference of indi- vidual species and (ii) the climatic associa- tion that can be inferred from the avifauna as a whole. The probable ecological require- ments of each of the species of birds known from the Fayum deposits and the most reasonable modern counterpart for each are assessed below. The most frequently encountered birds in the Jebel Qatrani Fotmation are jacanas (Jacanidae), with three species in two gen- era. These occur both in the upper and lower sequences. Jacanas are excellent paleo- ecological indicators because of their very rcstritted habitat requirements and because they are nonmigratory, being found only in warm, tropical climates (13). They have extremely long toes and associated tarsaJ specializations for walking on lily pads (Nymphaeaceae) and other floating vegeta- tion. Two of the jacanas from the Fayum are much larger than any living species, imply- ing very large lily pads or very densely matted vegetation. Fossils of Nymphaeaceae (Ndumbo) have been reported from the Fa- yum deposits {8). Two species of jacanas, diffeting mainly in size, occur sympatrically in parts of Africa today {Actophilomis afnca- nus and A. "Microparra" capensis) and pro- vide modern analogs for the fossils. Another characteristic member of the Fa- yum fauna is a shocbilled stork (Balaenicipi- tidae). The distinctive single living species of shoebill, Balofnkeps rex, is confined to east- central Africa in a narrow belt extending from the Sudan to Zambia. These birds forage mainly on dense mats of floating plants from which they capture large fish in the massive bill by "collapsing" forcefully through the vegetation {14). At least two species of herons (Ardeidae) occur in the Fayum deposits, one of which is inseparable from the modern genus of night herons Nycticorax, represented in Africa to- Fig, 1, The ranges of 12 of the 14 modem counterpans of Oligoc?ne fossu birds from the Fayum, Egypt, overlap in the limited area of southwestern Uganda (hatched area in map of Africa on the right) bounded by Lake Victoria, the Nile River, the Kagera River, and the western Rift Valley (enlarged on the left). The fossU bird assemblage indicates that the Fayum during the Oligoc?ne resembled the swamplands bordered by forests and savannas typical of areas that have been studied near modern Kampala and Kibale. day by N. nycticorax. The other is of less certain affinity but a reasonable modern counterpart would be the purple heron, Ardea purpurea, a species that frequents weU-vcgetated areas of freshwater. Both of these species arc widely distributed, though scattered, in Africa. A fossil stork (Ciconiidae) from the Fa- yum, PalaeoephippwrhynchHs dietrichi, was originally described as being similar to the modern saddlebill stork Ephippiorhynchus sene?(derisis {15), a species that occurs in various freshwater habitats throughout much of Africa. Two species of fossil flamin- gos (Phocnicopteridae) are present in the Fayum deposits, but these may be more closely related to the extinct genus Palaeh- dus, which had different locomotor and feeding adaptations and probably diflfcrcnt habitat requirements than modern flamin- gos, which are locally abundant at large, shallow lakes in east and east-central Africa. A small fossil crane (Gruidae) from the Fayum resembles in size the anatomically primitive crowned cranes {Bale?rica), which are widely distributed in moist areas of Africa and require dense swamp or marsh vegetation for nesting. A small rail (Ralli- dae) from the Fayum is similar to modem forms diat occupy a variety of habitats. Sarothrura rufa, the most widespread species of its genus and one that preferentially in- habits thick swamp vegetation, provides a reasonable counterpart. A fossil cormorant (Phalacrocoracidae) from the Fayum is similar in size and mor- phology to Phalacrocorax ctirbo, a widely distributed extant species found thtoughout most of eastern and southern Africa. It feeds on fish and other aquatic animals that it captures by diving. Two fossils from the Fayum are referred to the Pandionidae. The single modem spe- cies of this family, the osprey, Pandion ha- Uaetus, occurs in Africa almost entirely as a wintering bird from the north, but is wide- spread. Ospreys are almost entirely piscivo- rous and feed in both freshwater and marine situations by plunging on their prey from a height. If the habits of the fossil forms were similar, it would imply the presence of some areas of open water. An eagle from the Fayum is most similar to the genus Haliaee- tus, whose members are also largely piscivo- rous and occur mainly in the vicinity of aquatic environments. The modem African fishing eagle H. vocifer is the only member of the genus in continental Africa and is wide- spread. The only true land bird among the Fayum fossils, apart from the supposed rarites, is a turaco or plantain-eater. (Musophagidae) closely resembling species of the modem genus Crinifer {sensu stricto), of which the eastern species, C. zonurus, may be taken to represent the fossil form. The modern mu- sophagids are strictiy arboreal and are con- fined to Africa, where most of the species occur in heavily forested areas. Exceptions, however, are the species of Crinifer and Corythaixoides, which inhabit more arid sa- vanna, woodland or acacia bush. To find an area today where an avian assemblage most similar to that of the Fa- yum occurs, we used the maps compiled by Snow (J?), from which the distributions of aU the modern counterparts to the Fayum birds were superimposed. Overlap between the ranges of 12 of the 14 species occurs only in a very restricted area of Uganda, north and west of Lake Victoria, including the north shore of that lake (Fig. 1). It should be noted that among the modern analogs, the taxa of more limited distribu- tion that are the principal cause of the area of overlap being so restricted {Baiaeniceps, Crinifer, and Actophilomis) are among those whose fossil counterparts are the most confi- denriy identified. Snow does not report any osprey specimens from this area, but there are sight and breeding records for ospreys from the Ugandan shore of Lake Victoria {17, 18). The only species absent from this area are the flamingos, which require shal- low bodies of saline or brackish water, al- though flamingos do occur in the rift sys- tems that flank Lake Victoria on the east and west, and esmarine environments probably suitable for modern-type flamingos oc- curred near the site of deposition of the Fayum fossils {6, 8). The area of Uganda indicated above is recognized as forming a distinctive faunal 12 SEPTEMBER I986 REPORTS 1203 zone (19) bounded by Lake Victoria on the east, the Victoria Nile on the north, the Kagera River on the south, and the western rift system on the west (Fig. 1). The region differs from areas to the south and east of Lake Viaoria in having a wetter climate and, until recently, in supporting a belt of continuous forest. The vegetation today in- cludes a variety of moist savanna types, wooded grasslands, patches of forest, swamp, and swamp forest. Despite decades of intensive draining, swamps are abundant and widespread in Uganda, in some regions making up more than 20% of the surface area (20). Forest still covers 8% of the country, mostly in the southwest, although much has been cleared for human habita- tion, cattle grazing, and agriculture. Eggeling {21, 22) conduaed floral and faunal surveys of a virgin swamp bordered by forest near Kampala, Uganda, and identi- fied within the swamp seven successive com- munities that he named, on the basis of the dominant species, the lily, fringing papyrus, fern and sedge, Limnophyton, papyrus. Mis- canthidium, and palm zones. The ferns and sedges grow on immense floating mats of vegetation. The following birds, among oth- ers, were found in this swamp (21): muso- phagids {"Schizorhis" = Crinifer in part, spe- cies not identified). Bale?rica, Aaophilomis, Phidacrocorax, Ephippiorhynchus, at least three genera of rails, eight species of herons, including A. putpurea, and a variety of diur- nal raptors. Thus, the only major groups of Fayum birds not reported in the Ugandan swamp during Eggeling's survey were fla- mingos and Balaenkeps, the last possibly having been locally extirpated. In addition, Eggeling noted three species of primates in the swamp forest. An aerial photograph of such a swamp near Kampala shows areas of floating vegetation, open channels, and pa- pyrus fringes, bordered by extensive forest and patches of grassland (23). The forests near Lake Victoria have now been largely removed, but well-studied forested tracts such as Kibale Forest still exist to the west of the lake {19,20). Kibale supports an anthro- poid primate community consisting of two families, five genera, and eight species (24), which compares very closely with the two families, four genera, and eight species known from the upper sequence of the Jebel Qatrani Formation. By analogy with Uganda, the climate of the Fayum region of Egypt during the early Oligoc?ne may be assumed to have been warm, annually stable, and tropical. Near Kampala, the mean monthly low tempera- tures are about IS^'C, and the mean monthly highs are about IS^C, with little variation among months. Rainfall on the Ugandan shores of Lake Victoria averages 1520 to 2030 mm per year, and falls 160 to 170 days per year {19, 22,25). At Kibale Forest, 100 km west of the lake, the mean annual rainfall is 1475 mm, and it falls on the average 166 days per year. The daily mean minimum and maximum temperatures at Kibale are 12.7? and 25.5?C (24). At both 'Kampala and Bubale there is only mild seasonality of rainfall, with no severe dry season. The fossil avifaima provides strong evi- dence that the paleoenvironment of the Fa- yum during the Oligoc?ne closely resembled modern Ugandan swamps bordered by for- est and open woodland or grassland. This area of Uganda presents other striking paral- lels with the fauna, flora, and environment known or inferred for the Fayum. Thus, the climate and habitat of the earliest known hominoids may be projected with consider- able precision and confidence. The next African hominoids to appear in the fossil record after the Fayum forms are the various species of early Miocene dryopithecines, which are known mainly from the islands and shores of modern Lake Victoria (i), suggesting that such environments contin- ued to be important in hominoid evolution. The Fa^tim avifaima shows that fossil birds may be an important tool for paleoen- vironmental reconstruction providing a rela- tively direct means of interpretation compa- rable only to plant megafossils, for which birds provide an independent check. The persistence of Paleogene avian taxa into modern times may permit inferences to be drawn from a few dozen bird fossils that cannot be obtained from examination of thousands of mammalian teeth belonging to extinct families and genera. Paleontologists should be made increasingly aware of this underestimated resource so that avian fossils are no longer consigned to trays of scrap as so often in the past. REFERENCES AND NOTES 1. E. L. Simons, P. Andrews, D. R, Pilbcam, in Evolution of African Mammals, V. J. Magtio and H. B. S. Cooke, Eds. (Harvaid Univ, Press, Cam- bridge, MA, 1978), p. 120. 2. E. L. Simons and E. Delson, in Evolution of African Mammals, V. J. Maglio and H. B. S. Cookc, Eds. (Harvard Univ. Press, Cambridge, MA, 1978), p. 100. 3. K. F. Kav, J, G, Fleagle, E. L. Simons, Am. J. Phys. Anthropol. 55, 293 (1981). 4. E. L. Simons and T. M. Bown, Nature (London) 313,475(1985). 5. J. G. Fleagle et ai., Proc. Xth Congr. Int. Primawt. Soc, in press. 6. T. M, Bown and M, J. Kraus, U,S. Gtol. Surv. Prof. Pap., in press. 7. A. Kortiandt,/. Hum. Evol. 9, 277 (1980). 8. T. M. Bown et al., ibid. 11, 603 ( 1982). 9. D. T. Rasmussen, S. L. Oison, E. L. Simons, Smithson. Contrib. Paleobiol., in press. 10. E. L. Simons, Peabo?y Mus. Nat. Hist. Yale Unit. Bu?. 28, 1 (1968). 11. T. M. Bown and E. L. Simons,/. Afammai. 65, 539 (1984). 12. D. L, Gebo and D. T. Rasmussen, ibid. 66, 538 (1985). 13. S. L, Oison, Proc. Biol. Soc. Wash. 89, 259 (1976). 14. A. Guillet, Ostrich SO, 252 (1979). 15. K. Lajnbrecht, Geol. Hun?. Ser. Paiaeontol. 7, 1 (1930). 16. D. W. Snow, Ed., An Atlas ofSpeciatUm in African Non-Passerine Birds [British Museum (Namral His- lorv), London, 1978]. 17. C. W. Chorlev, UganiaJ. 7, 123 (1940). 18. A. W. WiUiarns, ibid. 8, 39 (1940). 19. J. Kingdon, East African Mammals: An Atlas of Evolution in Africa (Univ, of Chicago Press, Chica- r, 1974), vol. 1. W. Langlands, Occas. Pap. Dept. Ca^r. Makerere Univ. Kampala 43 (1973). 21. W. I. Eggeling, Uganda]. 1, 51 (1934). 22. ,/. Eco?. 23, 422 (1935). 23. L. C. Beadle and E. M. Lind, Uganda/. 24, 84 (1960). 24. T. T. Struhsaker, The Red Cotobus Monkty (Univ. of Chicago Press, Chicago, 1975), 25. J. P. Henderson, Uganda}. 13, 154 (1949). 26. We thank S. L. Wmg for comments on an carhcr draft of this manuscript and E. L. Simons for access to fossil collections. 5 May 1986; accepted 17 July 1986 I204 SCIENCE, VOL. 233