New Records of Fossil ‘Waterbirds’ from the Miocene of Kenya

2008·2.6 MB·English

by  Gareth J. Dyke

PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY
CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024
Number 3610, 12 pp., 4 figures April 9, 2008
New Records of Fossil ‘Waterbirds’ from the Miocene
of Kenya
GARETH J. DYKE1 AND CYRIL A. WALKER2
ABSTRACT
We present a number of new fossil records of ‘‘waterbirds’’ (encompassing several of the
traditionallivingordersofbirds)fromthreeimportantMiocenedepositsinwesternKenya.These
sites surround Lake Victoria—the Ngorora Formation and sediments at Maboko and Rusinga
Islands (Kula Formation)—are well-known hominoid localities, and have yielded a diverse
assemblageofcontemporaryfossilmammals.Previouslyidentifiedaviansfromthisareaincludea
maraboustork(Leptoptilossp.),thefossilflamingoLeakeyornisaethiopicus,aswellasanumberof
additional unidentified phoenicopterid (flamingo) remains. We add records of an anhinga
(Anhingacf.pannonica),twostorks(Ciconiaminor,C.cf.ciconia/nigra),anightheron(Nycticorax
cf. nycticorax) and a threskyornithid (the group that includes the ibises and spoonbills) to the
knowndiversityofKenyanMiocenewaterbirds.Wealsoillustrate,forthefirsttime,theholotype
and paratype material of the Kenyan Miocene flamingo Leakeyornis aethiopicus. Comparisons
with other known sites of this age across northern Africa, the Mediterranean and northern
Pakistan suggest that Miocene waterbird faunas in this region were very similar in their
compositions.WhileAnhingapannonica,Ciconiaminor,andCiconiaciconiaaredocumentedfrom
other Miocene sites across the region, the osteologically distinct fossil flamingo Leakeyornis
appearstohavebeenrestrictedtoEastAfrica.AlltheaviangroupsrecordedfromtheseKenyan
Miocene sites represent extant genera, in contrast to the described fossil mammals. As has been
widelyreportedfromotherAfricansitesofthisage,fossilbirdsthusrepresentavalidmechanism
forbuilding hypotheses aboutpalaeoenvironments.
1Division of Vertebrate Zoology (Ornithology), American Museum of Natural History; School of Biology and
EnvironmentalScience,UniversityCollegeDublin,BelfieldDublin4,Ireland([email protected]).
2DepartmentofPalaeontology,theNaturalHistoryMuseumLondon,CromwellRoad,SW75BD,UnitedKingdom.
CopyrightEAmericanMuseumofNaturalHistory2008 ISSN0003-0082
2 AMERICAN MUSEUMNOVITATES NO. 3610
INTRODUCTION and Paludiavis richae. These taxa link this
faunawiththatdescribedbyRich(1972)from
The Miocene-age (ca. 24–6 mya) avifaunas Tunisia. This Upper Miocene collection also
known from Africa all comprise a consider-
included two storks (Ephippiorhynchus pakis-
able number of aquatic or semi-aquatic birds
tanicus Harrison and Walker, 1982 and
(Rich,1972;HarrisonandWalker,1982;Rich
Leptoptilus siwalikensis Harrison, 1974), as
and Walker, 1983; Olson, 1985a; Louchart et
well as a pelican (Pelecanus sivalensis Davies,
al., 2005a, 2005b). Correlated with the pres-
1880). These last two species were originally
ence of such environments in some parts of
described from the Miocene of northern
Africa at this time, many species of ‘‘water-
Pakistan (Davies, 1880; Harrison, 1974).
birds’’ in the Miocene had a distribution that
Representative fossil ‘‘waterbirds’’ that
encompassed an area ranging from northwest
have previously been described from Kenya
Africa and southern Europe into northern
include the small flamingo Leakeyornis
PakistanandnortheasternAfrotropicalAfrica
(Phoenicopterus) aethiopicus (Harrison and
(Howard and Moore, 1984; Blondel and
Walker, 1976; Rich and Walker, 1983)
Mourer-Chauvire´, 1998). It has been suggest-
(fig. 1) and the small stork Ciconia minor
ed that suitable habitats for such species were
(Harrison, 1980), both from the Lower
more widespread across this broad geograph-
Miocene of Rusinga Island. Further material
icalregion,10–20 mya(Olson,1985a).Inspite
indistinguishable from the extant White
of such hypotheses, the literature on Miocene
Stork, Ciconia ciconia, is also known from
fossil birds from Africa has remained sparse;
the Middle Miocene of Maboko Island
this area of research has attracted relatively
(Andrews et al., 1981). New records of ‘‘birds
little attention over the last 20 years (but see
of prey’’ have also recently been described
Louchart et al., 2005a, 2005b; Walker and
from these sites (Walker and Dyke, 2006) as
Dyke,2006;Leonardetal.,2006).Asaresult,
well as a small, potentially new species of
thebackgroundtothepresentpaperjustifiesa
ostrich (Struthio sp.; Leonard et al., 2006).
brief synopsis of older literature.
In this paper we describe a number of new
Rich (1972) examined a collection of
fossil bird specimens from three Miocene
Middle–Upper Miocene fossil birds from
localities in western Kenya (Rusinga Island,
Tunisia and recognised the remains of a fossil
Maboko Island, and Ngorora) and discuss
anhinga(AnhingapannonicaLambrecht,1916),
their significance to our understanding of
originally described from Pannonian Beds
waterbird evolution in the later part of the
(these days regarded as Upper Miocene and
Paleogene. For thefirsttime we also illustrate
not Lower Pliocene) of Hungary (Lambrecht,
1916);afossilcormorant(Phalacrocoraxlittor- the paratype specimens of the Kenyan
alisMilne-Edwards,1863),firstrecordedfrom Miocene flamingo Leakeyornis aethiopicus
the Upper Oligocene of southern France; a (fig. 1).
fossil shoebill stork (subsequently named INSTITUTIONAL ABBREVIATIONS: BMNH S,
Paludiavis richae by Harrison and Walker, Bird Group Collections, Natural History
1982); and a fossil marabou stork (Leptotilos Museum, Tring; BMNH A, Department of
falconeri Milne-Edwards, 1868) that was later Palaeontology, Natural History Museum,
separated as a new species (L. richae) by London; KNM, Kenya National Museum,
Harrison (1974). Rich (1974) then recognised Nairobi; NMINH, National Museum of
ahindlimbofthissamestorkfromtheUpper Ireland (Natural History), Dublin.
MiocenelocalityofNgorora,Kenya,whichshe The fossil specimens discussed in this paper
consideredmightalsobereferabletoLeptotilos are deposited in the KNM, and were first
falconeri, distinct from L. richae. Hill and examinedinNairobibyP.Vickers-Richinthe
Walker (1979), however, considered this spec- 1970s, and then by C.A. Walker in 1980. All
imenundiagnostic. specimens were subsequently loaned to the
Harrison and Walker (1982) subsequently BMNH,wheretheyarecurrentlyhoused.Our
presented details of an Upper Miocene avi- useofanatomicalterminologyfollowsBaumel
fauna from northern Pakistan that included and Witmer (1993), with some modifications
additional fossils of both Anhinga pannonica to English after Howard (1929).
2008 DYKE AND WALKER:FOSSIL ‘WATERBIRDS’ OFKENYA 3
Fig. 1. Fossil material referred to the Lower Miocene Kenyan flamingo Leakyornis aethiopicus (see
Harrison and Walker, 1976). Not to scale. BMNH A 4382 (holotype)—portion of rostrum in dorsal view
(A); BMNH A 4383—proximal end of right tarsometatarsus in plantar view (B); BMNH A 4384—distal
portion of lower jaw in ventral view (C); BMNH A 4385—distal end of left humerus in cranial (D) and
caudal(E)views;BMNHA4386—distalendofrighthumerusincranial(F)andcaudal(G)views;BMNHA
4387—distalendoflefthumerusincranial(H)andcaudal(I)views;BMNHA4388—proximalendofleft
humerusin(J)caudalandcranial(K)views;BMNHA4389—proximalendoftarsometatarsusinplantar
(L)anddorsal(M)views;BMNHA4390—proximalendoftarsometatarsusindorsal(N)andplantar(O)
views; BMNH A4391—proximal endof tarsometatarsus inplantar (P) anddorsal(Q) views.
4 AMERICAN MUSEUMNOVITATES NO. 3610
Fig. 1. (Continued). BMNH A 4392—proximal end of tarsometatarsus in dorsal (R) and plantar (S)
views;BMNHA4393—distalendofrighttarsometatarsusindorsal(T)andplantar(U)views;BMNHA
4394—distalendoflefttarsometatarsusindorsal(V)andplantar(W)views;BMNHA4395—distalendof
rightfemurincaudal(X)andcranial(Y)views;BMNHA4396—distalendofrighttibiotarsusincranial(Z)
andcaudal(Aa)views;BMNHA4397—distalendoflefttibiotarsusincranial(Bb)andcaudal(Cc)views;
BMNH A4398—distal end oflefttibiotarsus in cranial (Dd) andcaudal (Ee)views.
2008 DYKE AND WALKER:FOSSIL ‘WATERBIRDS’ OFKENYA 5
Fig.2. NewrecordsofMioceneKenyanwaterbirds.Ciconiaminor,incompleteproximalrighthumerus
(KNMRU3075)incranial(A)andcaudal(B)views;Ciconiasp.,distalrighthumerus(KNHRU3914)in
cranial(C),caudal(D),andproximal(E)views;Ciconiaminor,distallefttarsometatarsus(KNMRU3898)
indorsal(F)andplantar(G)views;Anhingacf.pannonica,proximalendofrighthumerus(KNMBN1968)
incranial (H) andcaudal(I)views. Notto scale, seetextfor measurements.
SYSTEMATIC PALAEONTOLOGY variation and treat these birds within a single
species, Anhinga anhinga spp., while others
PELECANIFORMESRIDGEWAY,1887
accept two—A. anhinga in the Americas and
ANHINGIDAEBRISSON,1760 A.melanogasterintheOldWorld(seeHoward
and Moore, 1984). This latter arrangement
Anhinga cf. pannonica Lambrecht, 1916 maybemore acceptableonpurelyanatomical
MATERIAL: KNM BN 1968, proximal end grounds—Harrison (1978) noted a difference
of a right humerus (fig. 2). in the hypotarsal structure between the Old
LOCALITY AND AGE: Ngorora Formation, and New World forms that might justify their
Middle Miocene of Ngorora, western Kenya. specific separation.
The age of these deposits has been estimated The fossil record of the Anhingidae is
to be 12–10.5 mya; their sedimentology con- intermittent (Noriega and Alvarenga, 2002).
firms a semi-aquatic environment corroborat- The earliest apparent example of these birds,
ed by the presence of fish, crocodile, and Protoplotus beauforti Lambrecht (1930), was
hipporemainswithintheformation(Bishopet described from a crushed skeleton found in
al., 1971; Pickford, 1981). EocenedepositsontheIslandofSumatra,but
DISCUSSION: As many as four species of it is not until the Upper Miocene that the
anhingas(oneeachfromtheAmericas,Africa, family becomes abundant in the fossil record,
Asia, and Australia) are currently extant especially in South America (Olson, 1985a;
(depending on authors; Howard and Moore, Noriega and Alvarenga, 2002). By this time,
1984; Monroe and Sibley, 1993). However, however, anhinga osteology is largely indis-
becausethesetaxaexhibitlittlemorphological tinguishable from that of the recent genus,
variationotherthansize,therehasbeenmuch thusprovidingfewcluesastotheevolutionof
disagreement (especially in older literature) as thisgroupofbirds.OutsideofSouthAmerica,
to how many species should actually be in the Old World, three Neogene species are
considered valid. Some workers have suggest- recognised: Anhinga pannonica, from the
ed that anatomical differences represent noth- Upper Miocene of Hungary (Lambrecht,
ing more than a pattern of geographical 1916); Anhinga grandis, from the Upper
6 AMERICAN MUSEUMNOVITATES NO. 3610
Pliocene of North America (Martin and CICONIIFORMESBRISSON,1760
Mengel, 1975); and Anhinga hadarensis from
PHOENICOPTERIDAEBRISSON,1760
the Upper Pliocene of Ethiopia and early
Pleistocene of Tanzania (Brodkorb and
Leakeyornis aethiopicus (Harrison and
Mourer-Chauvire´, 1982). Of these records,
Walker, 1976) Rich and Walker, 1983
the Hungarian species may have been wide-
ranging—Rich (1972) attributed a cervical MATERIAL: Holotype, BMNH A 4382,
vertebrae and the proximal portion of a basal portion of rostrum. Paratypes, BMNH
humerus from the Upper Miocene of Tunisia A4383,proximalendofrighttarsometatarsus;
to A. pannonica, and Harrison and Walker BMNH A 4384, distal portion of lower jaw;
(1982) added another fragmentary humerus BMNH A 4385, distal end of left humerus;
and the distal portion of a tarsometatarsus BMNH A 4386, distal end of right humerus;
from the Upper Miocene of Pakistan to BMNH A 4387, distal end of left humerus;
thisfossil taxon. Asanaside, andtocomplete BMNH A 4388, proximal end of humerus;
our discussion of the African fossil record of BMNH A 4389-4392 proximal ends of tarso-
these birds, it should be noted that the Qua- metatarsi; BMNH A 4393-4394, distal ends of
ternary species Anhinga nana Newton and tarsometatarsi; BMNH A 4395, distal end of
Gadow (1893) described first from Mau- right femur; BMNH A 4396-4398, distal ends
ritius and later from Madagascar (Andrews, oftibiotarsi(fig. 1).Allcollectedandpresented
1897) was re-identified by Olson (1975) as a totheBMNHbyL.S.B.Leakey.
cormorant. LOCALITY AND AGE: Lower Miocene,
Although it is incomplete, KNM BN 1968 Rusinga Island (locality RS12), Lake Victoria,
closely resembles the known anatomy of both Kenya (for locality map and detailed informa-
the late Paleogene Anhinga pannonica and the tion,seevanCouveringandMiller,1969).This
extant A. melanogaster (which survives in is the oldest of the three sites yielding bird
Kenya today; Monroe and Sibley, 1993) materialtobedescribedinthispaper;sediments
(fig. 2). Referral to the former species, how- at this locality have been dated to 18–16 mya
ever, is supported on the basis of the size and (van Couvering and Miller, 1969) and again
age of this element—its placement within the havebeeninterpretedasindicativeoffloodplain
other African fossil taxon, A. haddarensis, is conditions with extensive bodies of standing
excluded because this species is much stouter water(Andrewsetal.,1981).
and stockier in its limb proportions than any DISCUSSION: Measurements and interpre-
of its kin (Brodkorb and Mourer-Chauvire´, tation of these specimens were presented by
1982). Even though KNM BN 1968 very Harrison and Walker (1976) and Rich and
closely resembles A. pannonica in details of Walker (1983).
its preserved morphology (fig. 2), we make
this referral tentatively because of a small CICONIIFORMESGARROD,1874
comparative sample size of A. melanogaster
ARDEIDAEVIGORS,1825
and because of the incompleteness of this
fossil. Nonetheless, the new specimen is
Nycticorax cf. nycticorax Linnaeus, 1758
somewhat larger than all available extant
examples of this genus (1.5–3 mm in most MATERIAL: KNM MB 562, right coracoid
dimensions); in this respect KNM BN 1968 lacking ventral portion of sternal end (fig. 3).
maycorroboratetheargumentsofRich(1972) LOCALITYANDAGE: Maboko Island, Lake
and Harrison and Walker (1982) regarding Victoria, western Kenya. The age of these
material already assigned to A. pannonica. deposits has been estimated to be 16.5–
MEASUREMENTS: KNM BN 1968, length 14.5 mya;sedimentsatMabokoaresomewhat
across tuberculum dorsale to tuberculum olderthanthoseexposedatNgororaandhave
ventrale—20 mm; maximum width of ca- been inferred to represent a floodplain envi-
put—23 mm; cranial extent of crista bicipita- ronment (Andrews et al., 1981).
lis—22 mm; shaft width and distal termina- DISCUSSION: Although the Night Heron
tion of crista bicipitalis—13 mm. (Nycticorax) appears to represent a distinct
2008 DYKE AND WALKER:FOSSIL ‘WATERBIRDS’ OFKENYA 7
Fig.3. NewrecordsofMioceneKenyanwaterbirds.Indeterminatecranialendofrightcoracoidreferred
to Threskiornithidae (KNM MB 563) in ventral (A), dorsal (B), and medial (C) views; Nycticorax cf.
nycticorax,incompleterightcoracoid(KNHMB562)inmedial(D),dorsal(E),andventral(F)views.Notto
scale,seetext formeasurements.
taxon that may have separated early from the MEASUREMENTS: KNMMB562,preserved
otherherons(Ardeidae),thereispresentlylittle length to dorsal lip of facies articularis sterna-
fossilevidenceforthis.Rasmussenetal.(1987) lis—41 mm;maximummedialwidthofhead—
described a tarsometatarsus from the Jabal 9 mm;dorsalthicknessofhead—4 mm;lateral
Qatrani Formation (Oligocene) in Fayum width to processus procoracoideus—7 mm;
Province, Egypt, which they considered virtu- dorsalthicknessatmidshaft—4 mm.
ally indistinguishable from the recent Black-
crownedNightHeron(Nycticoraxnycticorax),
CICONIIDAEGRAY,1840
currently present throughout Africa, southern
Europe, and Asia (Monroe and Sibley, 1993). Ciconia minor (Harrison, 1980)
ThisappearstobetheearliestPaleogenerecord
of the genus known to date (Olson, 1985a; MATERIAL: KNM RU 3075, incomplete
Rasmussenetal.,1987). proximal end of right humerus; KNM RU
The coracoid from Maboko Island (KNM 3898,distalendoflefttarsometatarsuslacking
MB562)istypicalofNycticoraxinthatithas the trochlea for metatarsal II (fig. 2).
a projecting processus acrocoracoideus and a LOCALITYANDAGE: Rusinga Island (Kula
ventrally developed facies articularis clavicu- Beds), Lake Victoria, western Kenya.
laris(fig. 3).Theshapeoftheconcavityofthe DISCUSSION: The first of the two fossil
surface between the processus acrocoracoi- specimens that we refer here to Ciconia minor
deusandthefaciesarticularishumeralisinthis consists of the articulating head of a right
specimen distinguishes it from the neotropical humerusbrokendistaltothesulcusligamentosus
Yellow-crowned Night Heron (Nyctinyassa transversus (fig. 2). The caput humeri and
violacea); this concave area also resembles tuberculum dorsale of KNM RU 3075 are
extant specimens of Nycticorax nycticorax preserved, however, and present characters that
(fig. 3). Although the dimensions of KNM canbeusedforreferral.Thecaputhumeriofthis
MB562aresmallerthancomparativematerial specimen is evenly domed and bears a distinct
of both these two extant genera (perhaps muscle attachment scar that slants over the
suggesting specific status for this specimen), cranial side of the tuberculum dorsale as seen
we follow Rasmussen et al. (1987) in tenta- typically in extant Ciconia (fig. 2). In caudal
tively referring this fossil to the extant N. view,thecaputhumeriismarkedlyprojectedas
nycticorax. inC.minor(Harrison,1980)moresothaninthe
8 AMERICAN MUSEUMNOVITATES NO. 3610
other extant species of this genus. This feature, THRESKIORNITHIDAERICHMOND,1917
combinedwiththepresenceofnumerousforam-
inadistaltothecaputhumeri,isconsistentwith Genus and species indeterminate
speciesthesamesizeorlargerthanC.minor.
The second specimen referred here (KNM MATERIAL: KNM MB 563, cranial end of
RU3898)consistsofjustthedistalextremityof right coracoid (fig. 3).
alefttarsometatarsusincludingasmallportion LOCALITYANDAGE: Maboko Island, Lake
ofshaft(fig. 2).Thisspecimenisverysimilarto Victoria, western Kenya.
extantciconiidswehaveexamined—thedorsal DISCUSSION: Rich(inAndrews,1981)tenta-
margin of trochlea metatarsal II is prominent tively referred this incomplete and damaged
andprojectsdistallybelowtheleveloftrochlea coracoidtothecharadriiformfamilyBurhinidae
metatarsalIII,asinCiconia(fig. 2).KNMRU (stone-curlews). However, if this element were
3898 corresponds with extant specimens of C. fromaburhinidthenitwouldpertaintoalarge
minorinitspreservedsize. bird—approaching the dimensions of Esacus,
MEASUREMENTS: KNM RU 3075, maxi- the Great Stone-curlew (Howard and Moore,
1984). However, KNM MB 563 lacks a well-
mum width across caput to tuberculum
developedprocessusacrocoracoideusalongwith
dorsale—23 mm; depth of caput humeri—
thedistinctprojectionontheventralfaceofthe
10 mm. KNM RU 3898: total length to
facies articularis clavicularis that characterises
trochlea metatarsal III—36 mm; total length
these birds (fig. 3). Our comparisons of this
to trochlea metatarsal IV—34 mm; width of
specimen suggest instead that it should be
shaft—30 mm; maximum width of trochlea
referredtoThreskiornithidae(ibisesandspoon-
metatarsal III—4 mm.
bills),andmorespecificallytotheibises.
The fossil record of Old World ibises from
Ciconia sp. Brisson, 1760 similarlyageddepositsis,however,poor.Milne-
Edwards (1863) described a Plegadis-sized ibis,
MATERIAL: KNMRU3914,distalendofa Actiornis pagana (see Harrison, 1986 for com-
right humerus (fig. 2).
mentsonthisgenus),fromtheUpperOligocene–
LOCALITYANDAGE: Rusinga Island (Kula Lower Miocene of France, and Olson (1985b)
Beds), Lake Victoria, western Kenya (see describedaspecies,Geronticusapelex,andreferred
above). anadditionalspecimentotheextantThreskiornis
DICUSSION: Although the two living species aethiopicus (Sacred Ibis). Both these latter taxa
of Ciconia that fall within the size range of our have been identified from Early Pliocene sedi-
material, the White Stork (Ciconia ciconia) and mentsinSouthAfrica(Olson,1985b).KNMMB
the Black Stork (C. nigra), are strikingly 563,however,isveryfragmentaryandwerefrain
different in their external appearance they are from referring it to a particular genus. In
very similar osteologically. Hence, with the comparison with extant species, this element is
exception of some characteristic elements (see largerthancorrespondingbonesfromtheGlossy
above),separationofthetwoonmorphological Ibis (Plegadis falcinellus) and smaller than those
groundsisoftenimpossible.Harrison(1980),for of the Sacred Ibis (Threskiornis aethiopicus) and
example,wasunabletodifferentiateaproximal theBaldIbis(Geronticuscalvus).KNMMB563
portionofacarpometacarpusfromtheMiocene suggestsathreskiornithidofsimilarsizetoeither
of Maboko Island among these two species of the Hadada (Bostrychia hagedash) or the
Ciconia.BecauseinitssizeandstructureKNM MadagascanIbis(Lophotibiscristata).
RU 3914 closelyresembles the distal humeri of MEASUREMENTS: KNM MB 563, greatest
therecentspeciesandeventhoughitsepicondy- width of sulcus muscularis supracoracoi-
lusdorsalisissomewhatmoreprojected(fig. 2), deus—9 mm; width of facies articularis clavi-
we refrain from more specific assignment here cularis—8 mm.
basedonsuchlimitedfossilmaterial.
MEASUREMENTS: KNM RU 3914, maxi- DISCUSSION
mum distal width—30 mm; width of shaft
proximal to processus supracondylaris dorsa- Descriptions of new records of fossil water-
lis—24 mm. birds from Miocene sites surrounding Lake
2008 DYKE AND WALKER:FOSSIL ‘WATERBIRDS’ OFKENYA 9
Victoria allow us to confirm the presence of ting CAW to study specimens in their care
five families of these birds in the assemblage. during a visit to Kenya in 1980. CAW also
Our re-examination of field collections made thanksMartinPickfordforhisencouragement
in the 1980s further augments the list of and considerable help during his stay and for
known taxa, in addition to previous descrip- later discussions concerning Kenyan Miocene
tions restricted to specific genera (a stork of fossil localities and comments on this paper.
the genus Leptoptilos and the flamingo CAW’s work was partly funded by the Boise
Leakeyornis)—we have added new records of Fund, Oxford. We thank Sandra Chapman
an anhinga (Anhingidae: Anhinga cf. pannoni- and Phil Crab (NHM, London) for their
ca), two distinct size-classes of storks assistance with this project, and Zlatozar
(Ciconiidae: Ciconia minor, C. cf. ciconia/ Boev and Timothy Crowe for providing
nigra), a night heron (Ardeidae: Nycticorax helpful reviews.
cf. nycticorax) and an indeterminate thres-
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