A 17-My-old whale constrains onset of uplift and climate change in east Africa Henry Wichuraa,1, Louis L. Jacobsb, Andrew Linb, Michael J. Polcynb, Fredrick K. Manthic, Dale A. Winklerb, Manfred R. Streckera, and Matthew Clemensb aInstitute of Earth and Environmental Sciences, University of Potsdam, 14476 Potsdam, Germany; bRoy M. Huffington Department of Earth Sciences, Southern Methodist University, Dallas, TX 75275; and cDepartment of Earth Sciences, National Museums of Kenya, 00100 Nairobi, Kenya Edited by Thure E. Cerling, University of Utah, Salt Lake City, UT, and approved February 24, 2015 (received for review November 10, 2014) Timing and magnitude of surface uplift are key to understanding with modern Indopacetus, Hyperoodon,andMesoplodon plus the impact of crustal deformation and topographic growth on four extinct genera. atmospheric circulation, environmental conditions, and surface Beaked whales are predicted by molecular clocks to have processes. Uplift of the East African Plateau is linked to mantle originated 26.52–35.82 Ma (6). The early record of fossil ziphiids processes, but paleoaltimetry data are too scarce to constrain is poor, but at 17.1 ± 1.0 Ma, the Kenyan specimen is currently plateau evolution and subsequent vertical motions associated the most precisely dated ziphiid fossil. Phylogenetic analysis nests with rifting. Here, we assess the paleotopographic implications the Turkana ziphiid with three modern genera, most notably Meso- of a beaked whale fossil (Ziphiidae) from the Turkana region of plodon, which has species that are estimated to have diverged at Kenya found 740 km inland from the present-day coastline of the 16.6 Ma (6, 7). Thus, the geochronologic constraint provided Indian Ocean at an elevation of 620 m. The specimen is ∼17 My old by the Turkana ziphiid is consistent with molecular predictions. and represents the oldest derived beaked whale known, consis- tent with molecular estimates of the emergence of modern strap- Ziphiids and Other Cetaceans in Present-Day and Paleorivers toothed whales (Mesoplodon). The whale traveled from the Indian Modern ziphiids are open-ocean, deep-diving specialized suction Ocean inland along an eastward-directed drainage system con- feeders that prey mainly on squid (8). Phylogenetic analyses in- trolled by the Cretaceous Anza Graben and was stranded slightly corporating molecular data (9) indicate that they are nested above sea level. Surface uplift from near sea level coincides with between the freshwater Ganges River dolphin (Platanista) and paleoclimatic change from a humid environment to highly variable the Yangtze (Lipotes) plus South American river dolphins (Inia and much drier conditions, which altered biotic communities and and Pontoporia). The Kenyan whale possesses derived ziphiid drove evolution in east Africa, including that of primates. characters of the beak, including hyperostosis, reduced gape, and evolutionary loss of teeth (characters not found in any clade of east Africa | Ziphiidae | uplift | drainage | paleoenvironment river dolphins). Moreover, the Turkana ziphiid’stotalbody length falls within the range of modern ziphiids (10) and is up to he Turkana ziphiid was found at Loperot in West Turkana, three times that observed in river dolphins. TKenya and described in 1975 by James G. Mead (1), who A wide variety of present-day marine whales has been ob- listed associated fauna, including mollusks, fish, crocodiles, tur- served in rivers, some of which may be associated with seasonal tles, and mammals, notably primates. Mead (1) detailed the migrations (11, 12). Modern ziphiids occasionally enter rivers, anatomy of the whale fossil, estimated its length in life at some 7 such as occurred in the 2006 stranding of Hyperoodon ampullatus m, and speculated that it was an open-ocean whale that became in the Thames River at London. Killer whales (Orcinus orca)have stranded after swimming up an eastward-flowing river and was then preserved near where it died. After the original publication Significance of this fossil find (1), the specimen went missing until late 2011, when it was rediscovered at Harvard University and returned to An enigmatic fossil representing the deep-diving, open-ocean the National Museums of Kenya (KNM), where it is curated whale family Ziphiidae found 740 km inland and at 620 m el- under the number KNM-LP 52956. evation in West Turkana, Kenya was rediscovered after it went Because the whale was found during the pre-Global Posi- missing for more than 30 years. This stranded whale fossil tioning System era, we studied the original 1964 Harvard expe- provides the first constraint on the initiation of east African dition field notes and catalog to locate the exact site of the ziphiid uplift from near sea level at 17 Ma, limiting the timing and (2°23′30″ N, 35°52′30″ Ebytriangulation)(Fig.1C)incoarse initial elevation of environmental change indicated by geo- fluvial sandstones and conglomerates of the Lower to Middle dynamic and climatic modeling, paleosols, isotopes, paleobot- Miocene Auwerwer Formation (2–4) ∼7 m below a basalt dated any, and the mammalian fossil record. At 17 Ma, elevation was at 17.1 ± 1.0 Ma (4). Although located in an area repeatedly low, rainfall was high, vegetation was forested, and mammalian affected by extensional processes since the Cretaceous, the fossil communities contained immigrants and native African species, location corresponds to the northern periphery of the Late Ce- including diverse primates. Uplift resulted in increasing aridity nozoic East African Plateau (EAP) (Fig. 1B). The specimen and open habitats that drove human evolution. consists of the rostrum and the ascending processes of the maxillae and premaxillae (length of 82 cm and width of 55 cm) Author contributions: H.W. and L.L.J. designed research; H.W., L.L.J., A.L., M.J.P., F.K.M., D.A.W., M.R.S., and M.C. performed research; H.W., L.L.J., A.L., M.J.P., F.K.M., D.A.W., broken from the rest of the skull (1). Five phylogenetically in- M.R.S., and M.C. analyzed data; and H.W., L.L.J., and M.R.S. wrote the paper. formative characters of KNM-LP 52956 (Fig. 2A and SI Ap- The authors declare no conflict of interest. pendix) were scored and entered into a data matrix of 46 This article is a PNAS Direct Submission. characters and 29 fossil and recent taxa (5). A traditional Wagner Data deposition: The 3D digital model of KNM-LP 52956 reported in this paper has been tree search (one random seed and 10 replications) applied to archived at www.digimorph.org/specimens/Turkana_ziphiid. unweighted and unordered characters yielded 17 most parsimo- 1To whom correspondence should be addressed. Email: [email protected]. nious trees of 124 steps (Fig. 2B). In all most parsimonious trees, This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. the Turkana ziphiid falls in a derived but unresolved clade 1073/pnas.1421502112/-/DCSupplemental. 3910–3915 | PNAS | March 31, 2015 | vol. 112 | no. 13 www.pnas.org/cgi/doi/10.1073/pnas.1421502112 Downloaded by guest on September 23, 2021 A B Ethiopian N 150 km zz zzzzzzz zzzz Plateau zzzzzz 4° Kenya whale 17.1 Ma (K/Ar) ANZA GRABEN C rst KENYA 0° Kenya whale Lokichar Fault RIFT Lokone HoHorst Lake Victoria LAMU Loperot Yatta lava flow EMBAYMENT 13.51 Ma (K/Ar) Auwerwer Hills N Elevation (m) East African 4° 5 km 3000 Plateau Auwerwer Basalts - Middle Miocene 2000 Indian Ocean Auwerwer Formation - Early to Middle Miocene 1000 33° 40° Lokone Formation - Oligocene to 500 Early Miocene Miocene – Recent rifting Normal faults Paleoaltimetric data Basement - Precambrian 0 Jurassic – Cretaceous rifting zzzz Shear zone Fig. 1. (A) Topography of Africa and bathymetry of the Atlantic and Indian Oceans. The white box indicates the location of the principal map shown in B. (B) Geological setting of the Cenozoic East African Rift System and topography of the present EAP based on a digital elevation model derived from Satellite Radar Topography Mission data. Elevations >1,000 m are enclosed by a white line. Rock ages for the basalt overlaying the beaked whale fossil and the Yatta lava flow phonolites are based on the radioactive decay of potassium (40K) into argon (40Ar). The white box indicates the location of the geological map in C. (C) Geological map of the Oligo-Miocene Lokichar Basin. The red diamond indicates the beaked whale fossil locality (Williams’ Flat) within the Lower to Middle Miocene Auwerwer Formation. been reported 161 km up the Columbia River at an elevation of fluviolacustrine strata that transition upward into marine units 6 m and river depth >10 m (Table 1) (13). In 2007, mother and toward the Kenya–Somalia coast in the Lamu Embayment (Fig. calf humpback whales (Megaptera novaeangliae) swam 133 km 1B) (19, 20). The Anza Graben constitutes a failed rift arm, upstream to Sacramento, CA (elevation of 4 m and river depth of which once linked rifting in the Central African Shear Zone with ∼10 m) (Table 1) (13). An Antarctic minke whale (Balaenoptera extensional processes in eastern Kenya that led to the separation bonaerensis) swam 1,000 km up the Amazon and its tributary the of Madagascar from Africa (19). Tapajós, traveling as much as 83 km in 1 day (Table 1) (14). In The size of the ziphiid, the regional context of the fluvial sedi- comparison, South American Sotalia fluvatilis, a river dolphin, has ments in which it was found, and the fauna associated with it in- a normal range that reaches an elevation of ∼100 m, where river dicate that the path to its stranding site was a sizable low-gradient depths are 10–30 m, 3,600 km up the Amazon drainage from the river. The ziphiid may have mistakenly entered the river while Atlantic Ocean (Table 1) (15).