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A new Late Miocene hominoid from Kenya: Samburupithecus kiptalami gen. et sp. nov.
0 AcadEtmie des sciences / Elsevier, Palaeontology / fal6ontologie (Human palaeontology / P&ontologie
Paris humaine)
A new Late Miocene hominoid from Kenya: Samburupithecus kiptalami gen. et sp. nov. Un nouvel hominoi’de du Miocene supkieur Samburupithecus kiptalami gen. etsp. nov.
du Kenya :
Hidemi ISHIDA’ and Martin PICKFORD~ ’ Laboratory of Physical Anthropology Graduate School of Science, Kyoto lJniversi@ Sakyo, Kyoto GOG, Japan ’ Chaire depalhanthropologie et deptibistoire, Coll&e de France, 11, place M.-Berthelot, 75005 Paris, and Laboratoire 8, rue Buffon, 75005 Paris, France
depaEontolo@e,
URA 12 du CARS,
ABSTRACT A new genus and species of hominoid, Samburupithecus kiptalami, is erected on the basis of a maxillary specimen with complete post canine dentition. Its age is established as upper Miocene (9.5 Ma) on the basis of radioisotopic dating and associated mammalian fauna. The new genus is more closely related to the African ape - human clade (AAH) than is any other known extinct hominoid and it may well be on the line leading to hominids. Keywords:
Hominoidea,
Maxilla.
Cheek
dentition,
late
Miocene,
Samburu
Hills, Kenya
Un nouveaugenre d’un maxillaire
et une nouvelle espBce d’hominoiite, Samburupithecus kiptalami sont u-&s dpartir comprenant une dentition postcanine compl& Son Gge, MiocBne supbieur (9,s Ma), est estimk d partir d’une datation radio-isotopique et de la faune mammalienne associtie. Le nouveau genre est plus proche du clade grands singes afn’cains - hommes (AAH) que d’aucun autre hominoi’de kteint. Mats
cl&
: Homino’id6,
Maxillaire,
Dents
jugales,
Miocene
superieur,
Collines
de Samburu,
Kenya
VERSION AB&G~E
Introduction Dans le Miocene superieur (lo,5 P 5,5 Ma) d’Afrique, peu de sp&imens d’homino1des sont connus : une molaire inferieure de Lukeino dat&e de 6 Ma (Andrews, 1975 ; Corruccini et McHemy, 1980) et un fragment de mandibule de Lothagam (Miockne terminal ca 6,5 Ma) (Kramer, 1986). Da& le but de combler cette lacune, le premier auteur a men6 l’expkdition Nippo-Kenyanne P Samburu Hills depuis 1980. Du fait du faible nombre de fossiles homino’ides d&ouverts dans les dep6ts africains du Mio&ne,moyen et superieur, les
paleoanthropologues ont consideri: l’&hantillon fossile eurasiatique comme l’anc&tre du clade AAH (De Bonis et al.! 1990 ; Begun, 1992 ; Alpagut et al., 1996). Pickford et al (1997) montrent que tous les grands singes eurasiatiques pretendus Ctre les ancCtres des hominid& sont d&iv& en direction de Pongo. L’homindide de grande taille vieux de 9,5 Ma, dCcouvert dans le Miociine supirrieur du Kenya, est morphologiquement et chronologiquement bien plack pour representer un tel anc&tre pour le clade AAH. Le spkcimen (KNM SH 8531) est constituk du maxillaire gauche, avec la dentition postcanine d’un primate approximativement de la taille d’un gorille femelle.
Note p&em&e par YvesCoppens Iiote remisele 10 aoDt1997,accepteele lr’ septembre1997
C. R. Acad. Sci. Paris, Sciences 1997. 325,823~829
de la terre
et des planetes
/ Eorfh & Planetary
Sciences
H. lshida
and
Contexte
M Pickford
geologique
et datation
longueur de la canine par rapport 2 P3-P4, ce specimen est consid& comme appartenant ?I une femelle (Pickford, 1986). Son gge au de&s est celui d’une jeune adulte.
Le maxillaire a eti: trouve dans les affleurements de la formation Namurungule, region de Samburu, Kenya (figure 1) (Pickford et al., 1984 ; Ishida et al,, 1994 ; Sawada et al., 1997). Une datation radio-isotopique de 9,47 f 0,22 Ma fut obtenue 2 partir d’un depat qui recouvre directement le niveau d’oh provient le maxillaire. Un sge de 9,57 f 0,22 Ma fut obtenu g partir de la coulee pyroclastique qui est immkdiatement sous-jacente au niveau 2 hominoi’de. Kous dkduisons de ces correlations de datation que l’homindide de Samburu a un 9ge de 9, j Ma. Cet gge est en accord avec la biostratigraphie des grands mammiferes (Pickford et al., 1984 a, b ; ?Jakaya et al., 1984).
La partie verticale du processus zygomatique Porte un tubercule osseux bas, qui doit rep&enter le processus malaire (figure 4). La base du zygomatique est plus proche de la rangee dentaire que chez n’impone quel homme ou grand singe actuel. mais eile ressemble Z3la position observke chez Proconsul et Morotopithecus(Pilbeam, 1969). Les racines de MZ penetrent la partie la plus basse de la racine &a&e du zygomatique. Le palais n’est pas aussi profondement voi3i. que celui des gorilles et chimpan&, mais il est plus arqu& que le palais peu profond et plus plat qui caracterise Proconsul,
Description
Morotopithecuset Rangwapithecus (figure 4). Dentition. P3 est une grande dent avec une racine linguale et
systhnatique
Superfamille Hominoidea Gray, 1825 Genre Samburupithecus gen. nov. Diagnose. Homindide de taille comparable 3 celle du gorille, dont le palais est assez profondement voDt& ; bord lateral de l’ouverture nasale & bords a&r& et ayant une inclinaison subhorizontale de 30” par rapport au plan occlusal dans la region supracanine et ant&o-canine ; fossa faciale large mais peu profonde, situee bien en avant de la racine anterieure du processus zygomatique ; racine antCrieure du processus zygomadque pneumatisee ; arcade zygomatique basse ; premolaires allongees ant&o-post&ieurement, par rapport 2 celles de Proconsulet des autres hominoi’des du Miocene ; extension de l’email vers la racine anterieure de P3 ; molaires sup&ieures 2 grand cingulum du protocBne ; email relativement epais ; jonction dentine-&nail 2 fort relief; cuspides des molaires bunodontes boursoufflees avec un plissement attenue de Yemail, bassin occlusal des molaires restreint ; M3 plus grande que M2 plus grande que M’ ; en vue occlusale, le processus alvColaire est rectiligne de C P M3. Espece Samburupithecus kiptalami sp. nov. Diagnose. Identique ~3celle du genre. Hololype.KNM SH 8531, fragment de maxillaire gauche avec une partie du palatin et du premaxillaire, l’alv&ole de la canine et P3-M’ (figure 3). Localit tpe. Site SH 22, coliines de Samburu, Nord Kenya (Pickford, et al., 1984). Datation et Horizon. Formation Namurungule, au-dessus du niveau calcaire et sous le niveau de coulee argileuse : Miocene superieur, Qe radio-isotopique 9,5 Ma. Description. KNM SH 8531 est un maxillaire/premaxillaire gauche partiel avec trois molaires, deux premolaires et l’al&ale de la canine (figure 2) (Ishida et al., 1984). Le processus alvColaire du maxillaire est rectiligne de C 2 M3, mais la M3 est 1egPrement dkjetee lingualement. D’apr+s le rapport de la
Introduction The African upper Miocene (10.5-5.5 m.y.) fossil record has previously yielded few large hominoid specimens. A
824
C. R. Acad.
deux labiales. Le paracane est plus haut que le protoc8ne et a les bards anterieur et posterieur saillanrs. Les c&es divisent la vallee sagittale en fovea anti-rieure, centrale et d&tale. Le protocbne est bunodonte et il est place plus en avant que le parac6ne. La P3 est entourCe d’un sillon hypoplastique prokminent. P4 est une grande dent triradiculke. Le paracBne a des c&es qui courent de l’extremit.+ de la cuspide vers la c&e anterieure, dans la vallee sagittale, et vers la c&e distale. Le protoc6ne est plus bas et sit& plus anterieurement que le para&ne, la couronne est entouree d’un sillon hypoplastique. M’ est mod&ment u&e. Le cingulum proilminent ceint le protoc6ne. Les sillons lingual et labial sont peu profonds et etroits. Les valliles intercuspides tendent j etre etroites mais profondes. Le bassin du trigone est restreint et les cuspides sont gonfl&es et depourvues de plissements. L’email du protocane de M’ de KNM SH 8531 est deux fois plus kpais que l’email des gorilles presentant la meme usure. M* est une version plus grande de M’, mais moins u&e. Le cingulum du protocane ne rejoint pas l’hypoc?me, bien qu’un sillon hypoplastique P cet endroit en donne l’impression. M3 est similaire mais plus grande que M’, une caractkristique inhabituelle chez les Hominoidea. Le cingulum du protocBne s’arrete au niveau de l’hypoc6ne. I1 y a un paraconule proCminent fusion& avec le cingulum anterieur. &Y$o@zie. La comparaison de Samburupitbecus avec les homino’ides mioc&es et actuels (Pickford et Ishida, en preparation) indique que celui-ci est plus proche du clade Grands Singes Africains - Hommes (AAH) (figure 5). I1 est plus probablement le taxon-fr?re du clade AAH ; mais il peut egalement appartenir P ce clade comme ancCtre des hominid&. Moins probable est I’hypoWse de proche parent avec le gorille (Andrews, 1992). La combinaison des caracteres du maxillaire de Samburupithecusindique que ce dernier occupe une position anterieure 2 1’Cvolution du clade AAH, mais qu’il etait posterieur aux hominoides du Miocene moyen, tel que le
Kenyapithecus.
lower molar from Lukeino aged about 6 Ma was originally considered to be closest in general morphology to those of australopithecines (Andrews, 1975), a view which was challenged on the grounds that the tooth was phenetically
Sci. Paris, Sciences
de la terre
et des planetes
/ Earth
& Planetary Sciences 1997. 325,023~829
A new
most like that of a chimpanzee (Corruccini and McHenry, 1980). A fragmentary mandible with a heavily worn first molar from Lothagam (late Miocene age ca 6-5 Ma) is so damaged that it is virtually unidentifiable (Kramer, 1986). In order to fill in this gap in the hominoid fossil record the senior author has led Expedition to Samburu
the Hills
on-going joint since 1980.
Because African middle and have yielded so few hominoid
upper fossils
Japan-Kenya
Miocene deposits there has been
a
tendency on the part of some palaeoanthropologists to look to the Eurasian fossil record for the ancestor of the African Ape - Human (AAH) clade (De Bonis, et al., 1990; Begun, 1992; Alpagut et al., 1996). Pickford et al. (1977) show on the basis of frontal anatomy that all Eurasian apes claimed to be hominid ancestors are derived in the direction of Pongo and are thus members of the Pongid clade. It is therefore appropriate to report the discovery, in the Upper Miocene of Kenya, of a large hominoid primate aged 9.5 Ma which is morphologically and chronologically well placed to represent clade. The specimen (KNM-SH tember, canine female
such an ancestor of the AAH 8531), discovered in Sep-
1982, consistsof much of the left maxilla with post dentition of a primate approximately the size of a gorilla.
Geological
Late
context
Miocene
hominoid
from
Kenya
and age
The maxilla was found lying on the surface of an outcrop of intra-formational conglomerate which forms a prominent cliff and dipslope at site SH 22 in the southeastern outcrops of the Namurungule Formation, Samburu District Kenya (figure I) (Pickford et al., 1984a, b; lshida et al., 1994; Sawada et al., 1997). Matrix attached to the specimen is similar to that of the intra-formational conglomerate which contains a great deal of in situ bone. Above and below the conglomerate lense is a sequence of tuffaceous shales which yield fossilized fish remains as well as pumice clasts. On the basis of its attached matrix and position in the field we believe that it is likely that the hominoid specimen was originally buried and fossilized in the conglomerate. Lavas lying unconformably below the Namurungle Formation have been dated at 12-13 Ma (Matsuda et al., 1984) while lavas which unconformably overlie the ments have yielded a date of 7.08 +/-- 0.28 Ma. A radioisotopic date of 9.47 +/- 0.22 Ma (Sawada 1997) was obtained from alkali feldspars separated
sediK-Ar et al, from
pumices in a deposit which immediately overlies the bed from which the maxilla came. An age of 9.57 +/- 0.22 Ma was obtained from alkali feldspars separated from a pyroelastic flow deposit which immediately underlies the hominoid bed. We infer from this relationship that the Samburu hominoid is close to 9.5 Ma. This age determination accords with the large mammal biostratigraphy of the formation (Pickford et al., 1984a, b; Nakaya et al., 1984).
Systematic
description
Superfamily Hominoidea Gray, Genus Samburupithecus gen. Diagnosis. Large hominoid approximately
1825 nov. the
size
of
Gorilla in which the palate is relatively deeply arched; lateral margin of nasal aperture sharped-edged and sloping at a subhorizontal 30” angle to the occlusal plane in the supracanine and antero-canine area; large but shallow facial fossa situated well forward of sloping anterior root of zygomatic process; anterior root of zygomatic process pneumatized; zygomatic arch low, premolars anteroposteriorly expanded relative to those of Proconsul and other Miocene hominoids; rootward extension of enamel on anterior root of P3; upper molars with large protocone cingulum; relatively thick enamel caps on high relief
Figure 1. location of upper Miocene (AR: Athi River; BN: Ngorora; LU: Mpesida; NA: Nakali; NC: Ngeringerowa; :‘tr ‘:::i
fossiliferous sites in Kenya Lukeino; LT: Lothagam; MP: SH: Samburu Hills).
Localisation des gisements fossiliflres du Mioc+ne Kenya (AR : Athi River; BN : Ngorora ; LU : Lukeino gam ; MP : Mpesida ; NA : Nakali ; NC : Ngeringerowa buru Hills). C. R. Acad. 1997.325,823-829
Sci.
Paris,
Sciences
de
la terre
et des
sup6rieur du ; LT : Lotha; SH : Sam-
plan&es
dentine enamel junction; inflated, bunodont molar cusps with subdued wrinkling of enamel; molar occlusal basins restricted; M3 larger than M2 larger than M’; in occlusal view the alveolar process is straight from C-M3. Species
Samburupithecus
kiptalami
sp. nov.
Diagnosis. As for the genus. Holotype: KNM SH 8531, partial left maxilla with tion of palatine and premaxilla, with canine alveolus complete
/ Earth & Planetary
Sciences
P3-M3
(figure
porand
3).
825
H. lshida
and
Type (Pickford,
Locality: et al.,
Horizon
M Pickford
Site SH 22, 1984a).
and
limestone and Fauna1 Set VI:
Age:
Hills,
Namurungule
below mud radioisotopic
Etymology:‘Samburu’ which the holotype nours Mr Kiptalam
Samburu
North
Formation,
flow member: age 9.5 m.y.
Kenya
above
Upper
Miocene,
refers to thedistrict in Kenya from was collected, the species name hoCheboi, a member of the joint Japan-
Kenya Expedition, who found the specimen. Informally in the literature this hominoid has been called the Samburu Hominoid as well as Motopitbecus. At present the latter name is a nomen nudum but could be validated by us, but because the genus Morotopithecus has recently been erected possible therefore
by Gebo et al. (1997), confusion between two erect the generic name
we prefer to avoid such similar names Samburupithecus.
0 L
and
M3
are
little
4 I cm
Figure 3. Profiles of the maxilla of Samburupithecus taken at P“ and MZ to show facial fossa (F) and low position notch of the zygomatic root (M). ,r,,& /!a
length of C relative to P3-P4 this specimen is considered to represent a female, given that the ratio C/P3-P4 was dimorphic to the same degree as it is in gorillas (Pickford, 1986). It was a young adult when it died: its M’ is in medium wear M2
M2
any and
Description: KNM SH 8531 is a partial left maxilla/ premaxilla with three molars, two premolars, and the canine alveolus (figure 2) (Ishida et al., 1984). The alveolar process of the maxilla is straight from C-M3, but the M3 is slightly offset lingually. By inference from the ratio of the
while
SH 8531
worn.
Profils du maxillaire de Samburupithecus kiptalami p? et MZ montrant /a fosse faciale (F/ et /a position malaire du zygomatique (MI.
The region
maxilla is slightly crushed, principally and much of its surface is weathered.
pris basse
kiptalami of malar
au niveau de du tubercule
in the palatal It was found
in four pieces which have been accurately reconstructed since the edges of the pieces fit well against each other. The general proportions of the maxilla can be estimated within reasonable limits. The zygomatic process of the maxilla has a long forward-sloping anterior root which merges anteriorly into a large but shallow facial fossa. The vertical portion of the zygomatic process carries a tubercle of bone low down which may represent the malar process (figure 4). The base of the zygomatic is closer to the tooth row than it is in any living great apes or man, but resembles the position observed in Proconsul and Morotopithecus (Pilbeam, 1969). The upper part of the zygomatic root is missing, and a large maxillary sinus, now partly filled with matrix, can be discerned. The sinus extends forwards into the anterior root of the zygomatic process as it does in Gorilla and Pan. The roots of M2 penetrate the lower part of the flaring zygomatic root, which suggests that the zygoma are low in Samburupithecus. In all specimens of fan, Gorilla, fongo and Homo available for comparison in the Kenya National Museum, the molar roots do not reach upwards as far as the flaring root zygomatic process. In this respect Samburupithecus calls Proconsul and Morotopithecus.
Figure 2. Occlusal Samburupithecus ,: “- : Vues occlusale Samburupithecus
a26
and lateral view of KNM SH 8531, kiptalami nov. gen., nov. sp. et /at&a/e kiptalami
de KNM SH 8531, nov. gen., nav. sp.
left
A small portion of the margin of the nasal aperture is preserved in SH 8531 from a point above the canine root for a distance of about 20 mm. It slopes at a subhorizontal angle of 30” relative to the occlusal plane, quite unlike the steeply oriented nasal margin in man and Rangwapi-
maxilla,
thecus.
maxi/lake
anterior
gauche,
C. R. Acad.
of the re-
slopes Sci. Paris,
Sciences
The lateral and medial downwards de
la terre
part of the floor of the nasal aperture to the canine root is sharp-edged and and forwards, unlike the rounded and et des
plan&es
/ Eari%
& Planetary Sciences 1997. 325,823-829
A new
Late Miocene
hominoid
from
Kenya
In lateral view the alveolar margin of SH 8531 curves upwards anteriorly much less than it does in Pongo, and in this respect it is similar to Pan and Gorilla. In occlusal view the alveolar process is straight from C-M3, as in most non-human hominoids. The alveolar process is preserved from the anterior part of the canine alveolus to the rear of M3. The absence of an incisor alveolus in the small portion of premaxilla preserved in front of the canine, suggests that there was probably a diastema in SH 8531. The canine alveolus is abraded laterally, so it is not possible to obtain the complete cross-sectional shape of the canine root. However, in its preserved parts, the alveolus resembles those of female gorillas, especially in the rounded shape of the postero-lingual corner and by its size relative to the premolars. Itdiffers in shape and orientation from the more uniformly
oval
alveolus
of Pongo
and
Homo.
Dentition. P3 is a large tooth with one lingual and two labial roots. The anterior edge of the paracone projects forwards and would have slightly overlapped the canine in labial view. A small contact facet for the upper canine is preserved on P3 near the labial margin of the anterior surface of the tooth. The position of this facet is similar to that seen in female gorilla specimen number OM 3544 in the Kenya National Museum. Enamel extends onto the anterior labial roots, much as in Gorilla and Pongo. This feature in hominoid P3s is correlated with the possession of a honing function in P, and it seems likely that Samburupithecus would have possessed such a feature in its lower P,. The paracone is higher than the protocone and
OM 3264 GOrilla
0 I
has sharp anterior and posterior edges. Ridges which are almost obliterated by wear and erosion lead into the sagittal valley. These ridges divide the sagittal valley into anterior, central and distal foveae. The protocone is bunodont and is placed further forwards than the paracone. It
5 4
I cm
Figure 4. Sections of palates (at M’) of fossil and apes to show palatal depth (arrow shows position holotype of Samburupifbecus kipfalami). k*t$mm:
extant African of break in the
Coupes des palais (prises au niveau de M’) des grands singes fossiles et vivants montrant /a profondeur du palais (la f/&he une cassure dans I’holotype de Samburupithecus kiptalami).
raised
floor
of the
nasal
aperture
in Pan
but
africains indique
resembling
some specimens of Gorilla (e.g. OM 3543 in the National Museum of Kenya). The palate is not as deeply arched as those of gorillas and chimpanzees, but it is much more deeply arched than the shallow and flatter palate that typifies Proconsul, Morotopithecus, and Rangwapithecus (figure 4). In SH 8531 a short portion of the inter-palatine suture is preserved opposite M ’ - 2 , but since the palate is slightly crushed, reconstructions of palatal breadth will need to take into account the displacements of bone involved in the crushing. Because the damage is due to minor faulting accompanied by rotation of slivers of palate, reconstruction may be possible. However, suture preserved is short, we cannot arcade shape with confidence. C. R. Acad. Sci. Paris, Sciences 1997. 325,823~829
because the length of reconstruct the dental
de la terre
et des plan&es
/ Earth
has two ridges which rior ridges respectively. hypoplastic groove.
lead towards the anterior and posteThe P3 is encircled by a prominent
P4 is a large oval three-rooted tooth. On the anterior labial margin of the paracone is a low crest. Otherwise, the labial surface of the paracone is smoothly curved. The paracone has worn and eroded occlusal ridges which lead from the area of the cusp tip towards the anterior ridge, into the sagittal valley and towards the distal ridge. As with the P3, these ridges define the edges of the anterior, central and distal foveae. The protocone is lower and more anteriorly situated than the paracone. Perikymata are clearly visible on the worn surface of the paracone, and the crown is encircled by a hypoplastic groove. M’
is a moderately
worn
tooth
with
on the protocone, paracone, metacone small chip of enamel is missing from
dentine
exposures
and hypocone. A the tip of the para-
cone. A prominent cingulum borders the protocone, but it does not lead onto the hypocone. The anterior cingulum is inflated and the anterior fovea is consequently filled in and rather small. The distal fovea is open and moderately deep. The lingual and labial notches are shallow and narrow. The intercusp valleys tend to be narrow but deep, so that cusps are still separated even after moderate wear. & Planetary
Sciences
H. lshido
and
The trigon remarkably
M Pickford
basin free
is restricted of wrinkles.
Enamel thickness. Although the style of wear in Samburupithecus molars suggests that they are thin enamelled,
and the cusps are inflated and This suite of features is prob-
ably related to the possession of relatively thick enamel caps in the molars. The enamel on the protocone of M’ of KNM SH 8531 is more than twice as thick as enamel in similarly worn gorilla molars measured at homologous
such is an illusion caused by a high relief dentine enamel junction. The enamel on the protocone of M’ in SH 8531 is 2.2 mm thick. In a gorilla specimen (OM 3264) at a comparable wear stage, the enamel is 1 mm thick. The
points. M* is basically a larger version of M’, but is less worn. The protocone cingulum does not lead onto the hypocone although a hypoplastic groove at this level gives the impression that it does. There is a small ridge which
relief of the dentine enamel junction in Samburupithecus molars is high. It compares well with most lower Miocene hominoids as well as living African apes and man. It differs markedly from Kenyapithecus, Heliopithecus, Afropithecus, Sivapithecus, Ouranopithecus and Pongo which
runs from the protocone M3 is morphologically an unusual feature in
tip onto the lingual cingulum. similar to but is larger than M’, Hominoidea. The distal ridge is
inflated and lightly beaded. The protocone cingulum stops at the hypocone as in M’ and M2, but is joined by a crest to the tip of the hypocone. The wear in this tooth is greater on the labial cusps than on lingual cusps which are virtually unworn. The tip of the protocone is marked by a scattering of hypoplastic pits. There is a prominent paraconule fused to the anterior cingulum. An unusual feature of the molars is that M3 is larger than M2 and M’. Such inter-molar proportions are found in Rangwapithecus, although
but do not occur
Australopithecus
in other
afarensis
hominoid sometimes
taxa ap-
proaches this condition. The enamel surface possesses remarkably subdued wrinkling and other surface ornamentation, and Samburupithecus therefore differs from most hominoids, in particular Rangwapithecus and Pongo, in which secondary wrinkling is well developed.
have considerably enamel junction.
more
subdued
relief
of
the
dentine
The wear gradient in the cheek teeth of SH 8531 is comparable to that seen in gorillas and chimpanzees, but is not as marked as it is in Sivapithecus. The main wear facets on P3, p and M’ are oriented much as in Gorilla and other African hominoids.
Phylogeny. ocene
and
Comparison extant hominoids
of
Samburupithecus (Pickford
and
lshida
with Miin prep.)
indicates that it is most closely related to the African Ape Human clade (AAH) (figure 5). It is most likely to be the sister group of the AAH clade. Andrews (1992) has proposed that it should be positioned within this clade as the ancestor of the gorilla but we consider that the dentition of
Samburupithecus as Praeanthropus
is closer
africanus
to that of early hominids from Laetoli and Kanapoi
such and
upper premolars of Samburupithecus are mesioenlarged in comparison with the premolars of Miocene apes, with the exception of Rangwapithecus. In their general proportions the P3 and P4 of SH 8531 are similar to those of living apes and man. Dental
The distally lower
dimensions
are
listed
in Table.
Samburipithecus
Eurasian Apes Table. ::9::Y
Dimensions
Mensurations
of the des dents
cheek
jugales
teeth de KNM
KNM
SH 8531.
SH 853
1.
Middle Miocene African Apes C*
ap tr root
lle 9e 23e
length
Early Miocene African Apes
P3
ap labial ap sagittal tr
10.5 8.6 11.7
P
w tr
9.8 12.7
M’
w tr
13.9 13.3
MZ
w tr
15.7 15.8
M3
w tr
16.6 16.8
P3-M3 Ml-M3 P3-p4
ap: antero-posterior;
828
Position syst@matique simp/ifEe de Samburupithecus. (AAH inch Praeanthropus, Australopithecus, Paranthropus, Homo, Pan, Gorilla et Ardipithecus ; Eurasian Apes inclue Griphopithecus, Dryopithecus, Oreopithecus, Ouranopithecus, Ankarapithecus, Platodontopithecus, Sivapithecus, Lufengpithecus, Gigantopithecus et Pongo Middle Miocene African Apes inclut Kenyapithecus et Otavipithecus ; far/y Miocene African Apes inch Proconsul, Afropithecus, Heliopithecus et Morotopithecus).
64.5 46.4 18.5
sagittal sagittal sagittal tr: transverse;
e: estimate. C. R. Acad.
Figure 5. Simplified phylogenetic position of Samburupithecus. (AAH include Praeanfhropus, Australopithecus, Paranthropus, Homo, Pan, Gorilla and Ardipithecus; Eurasian Apes include Griphopithecus, Dryopithecus, Oreopithecus, Ouranopithecus, Ankarapifhecus, Platodontopifhecus, Sivapithecus, Lufengpithecus, Cigantopithecus and Pongo; Middle Miocene African Apes include Kenyapithecus and Otavipifhecus; Early Miocene African Apes include Proconsul, Afropithecus, Heliopithecus, and Morotopithecus). W&Ww)
Sci. Paris,
Sciences
de
la terre
et des
plan&es
/ Earth
&
Plonetafy Sciences 1997.
325,823-829
;
A new
to be in the direct ancestry of an exclusive ancestor of the gorilla. Among characters supporting this view are several unusual features including M3 larger than M2 (occurs in some specimens assigned to Australopithecus afarensis and Paranthropus boiser), the molar cusps relatively free of wrinkling, restricted molar occlusal basins, the large and inflated protocone cingulum and the antero-posteriorly elongated premolars. The deeply arched palate, the antero-posteriorly elongated premolars, the position and extent of the facial fossa and the sharp-edged anterior nasal margin are plesiomorphic for the AAH clade. Samburupifhecus lacks the derived characters that unite the Eurasian Apes into a single (Pongo} clade whereas it retains several plesiomorphic features such as low position of the zygomatic arch that occur in Early and Middle Miocene African Apes. it is thus hominids
more
rather
likely
than
Late Miocene
hominoid
from
Kenya
Summary. The salient morphological features of the Samburupithecus kipfalami maxilla include its large size; palate arched more deeply than in Proconsul, Morotopithecus and Afropithecus, but not as deeply as in fan, Gorilla and hominids; sharp-edged nasal margin; low, retired zygomatic root; and straight cheek tooth row. The sharp-edged nasal margin is similar to some gorilla specimens but this character is variable and its value for systematics is uncertain. The combination of dental and maxillary features of Samburupithecus indicates that it occupies a position close to the African Ape - Human (AAH) clade, but was posterior to middle Miocene hominoids such as Kenyapithecus (figure 5). Within the AAH clade, Samburupithecus is closest in dental morphology to primitive hominids such as Praeanthropus. As such it throws a great deal of light on the late Miocene ancestry of humankind.
Acknowledgements: of Education, P. Taquet and
We thank the Government of Kenya and Director of the National Museum of Kenya, the Japanese Ministry Science and Culture and Prof. S. Ishida, H. Mitsushio. J. Itani, J. Ikeda. K. Hanihara. S. Matano, Y. Coppens and Drs T. Makinouchi, T. Koyaguchi. H. Nakaya. T. Matsuda and Y. Nakano. In particular we thank Mr Kiptalam Chepboi.
REFERENCES Alpagut B.. Andrews P., Fortelius M.. Kappelman J., Temizsoy I., Celebi H. and Lindsay W. 1996. A new specimen of Ankarupithecus mefeoj from the Sinap Formation of Central Anatolia, Nature, 382,349-35 1 Andrews P.J., in: Pickford M. 1975. Late Miocene sediments and fossils from the Northern Kenya Rift Valley, Nature, 256.279-284 Andrews P. 1992. Evolution and environment in the Hominoidea. Nature, 360,641~646 Begun D. 1992. Miocene fossil hominids and the chimp-human clade, Science. 257. 1929-1932 Corruccini R.S. and McHenry H.M. 1980. Cladometric analysis of Pliocene hominid% J. Human Evoi., 9.209221 De Bonis L., Bouvrain G.. Geraads D. and Koufos G. 1990. New hominid skull material from the late Miocene of Macedonia in Northern Greece, Nature, 345,7 12-7 14 Gebo D.L., MacLatchy L., Kityo R.. Deino A.. Kingston J. and Pilbeam D. 1997. A hominoid genus from the Early Miocene of Uganda, Science. 276.401-404 lshida H.. Pickford M.. Nakoya H. and Nakono Y. 1984 Fossil anthropoids from Nochola and Samburu Hills, Samburu District. Kenya, AfK Study Monogr. Suppl. Issue. 2.73-85 lshida S., Makinouchi T,, Sawada Y.. Tafeishi M, and Uemara. Y. 1994. Geologic Map of the Sombufu Hills. Kenya Kyoto University-National Museums of Kenya Samburu Hills Expedition, Fat. Sci. Kyoto University Kramer A. 1986. Hominid-Pongid distinctiveness in the Miocene-Pliocene fossil record: the Lothagam mandible. Am. J. Phys. Anthrop.. 70.457-473
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Matsuda T.. Torii M.. Koyaguchi T., Makinouchi T., Mitsushio H., lshido H. and lshida S. 1984. Fission-track, K-Ar age determinations and palaeomagnetic measurements of Miocene volcanic rocks in the western orea of Baragoi. Northern Kenya: age of hominoids. Afr. Study Monogr: Suppl. Issue, 2.57-66 Nakaya H.. Pickford M.. Nakano Y. and lshida H. 1984. The late Miocene large mammal fauna from the Namurungule Forma tion. Samburu Hills, Northern Kenya, Afr. Study Monogr. Suppl. Issue, 2,87-131 Pickford M., lshida H.. Nakano Y. and Nakaya H. 1984a. Fossiliferous localities of the Nachola-Samburu Hills area, Northern Kenya, Afr. Study Monog~ Suppl. Issue, 2,45-56 Pickford M.. Nakaya H.. lshida H. and Nakan0.Y. 1984b. The biostratigraphic analyses of the faunas of the Nachola area and Samburu Hills. Northern Kenya, Afr Study Monogr: Suppf. Issue. 2, 67-72 Pickford M. 1986. Sexual dimorphism in Proconsuf, in: Pickford M., and Chiarelli A.B., (eds). Sexuol dimorphism in living and fossil Primates, II Sedicesimo. Florence, 133-170 Pickford M.. Moya Sola S. and Kohler M. (1997). Phylogenetic implications of the first African Middle Miocene hominoid frontal bone from Otavi, Namibia, C. R Acad. Sci. Paris, 325, Series Iia. 459-466 Pilbeam D.R. 1969. Tertiary relationshrps and taxonomy, l-185
Pongidae of East Africa: Evolutionary Bull. Peabody Mus. Nat. Hist., 31.
Sawada Y., ltaya T,, lshida H.. Kobeto K.. Makinouchi S. 1997. The age of Somburu Hominoid. Preprint Japan. Sot. Africanists. 45
& PJctnetav
Sciences
T and lshida Ann. Meeting
Paris humaine)
A new Late Miocene hominoid from Kenya: Samburupithecus kiptalami gen. et sp. nov. Un nouvel hominoi’de du Miocene supkieur Samburupithecus kiptalami gen. etsp. nov.
du Kenya :
Hidemi ISHIDA’ and Martin PICKFORD~ ’ Laboratory of Physical Anthropology Graduate School of Science, Kyoto lJniversi@ Sakyo, Kyoto GOG, Japan ’ Chaire depalhanthropologie et deptibistoire, Coll&e de France, 11, place M.-Berthelot, 75005 Paris, and Laboratoire 8, rue Buffon, 75005 Paris, France
depaEontolo@e,
URA 12 du CARS,
ABSTRACT A new genus and species of hominoid, Samburupithecus kiptalami, is erected on the basis of a maxillary specimen with complete post canine dentition. Its age is established as upper Miocene (9.5 Ma) on the basis of radioisotopic dating and associated mammalian fauna. The new genus is more closely related to the African ape - human clade (AAH) than is any other known extinct hominoid and it may well be on the line leading to hominids. Keywords:
Hominoidea,
Maxilla.
Cheek
dentition,
late
Miocene,
Samburu
Hills, Kenya
Un nouveaugenre d’un maxillaire
et une nouvelle espBce d’hominoiite, Samburupithecus kiptalami sont u-&s dpartir comprenant une dentition postcanine compl& Son Gge, MiocBne supbieur (9,s Ma), est estimk d partir d’une datation radio-isotopique et de la faune mammalienne associtie. Le nouveau genre est plus proche du clade grands singes afn’cains - hommes (AAH) que d’aucun autre hominoi’de kteint. Mats
cl&
: Homino’id6,
Maxillaire,
Dents
jugales,
Miocene
superieur,
Collines
de Samburu,
Kenya
VERSION AB&G~E
Introduction Dans le Miocene superieur (lo,5 P 5,5 Ma) d’Afrique, peu de sp&imens d’homino1des sont connus : une molaire inferieure de Lukeino dat&e de 6 Ma (Andrews, 1975 ; Corruccini et McHemy, 1980) et un fragment de mandibule de Lothagam (Miockne terminal ca 6,5 Ma) (Kramer, 1986). Da& le but de combler cette lacune, le premier auteur a men6 l’expkdition Nippo-Kenyanne P Samburu Hills depuis 1980. Du fait du faible nombre de fossiles homino’ides d&ouverts dans les dep6ts africains du Mio&ne,moyen et superieur, les
paleoanthropologues ont consideri: l’&hantillon fossile eurasiatique comme l’anc&tre du clade AAH (De Bonis et al.! 1990 ; Begun, 1992 ; Alpagut et al., 1996). Pickford et al (1997) montrent que tous les grands singes eurasiatiques pretendus Ctre les ancCtres des hominid& sont d&iv& en direction de Pongo. L’homindide de grande taille vieux de 9,5 Ma, dCcouvert dans le Miociine supirrieur du Kenya, est morphologiquement et chronologiquement bien plack pour representer un tel anc&tre pour le clade AAH. Le spkcimen (KNM SH 8531) est constituk du maxillaire gauche, avec la dentition postcanine d’un primate approximativement de la taille d’un gorille femelle.
Note p&em&e par YvesCoppens Iiote remisele 10 aoDt1997,accepteele lr’ septembre1997
C. R. Acad. Sci. Paris, Sciences 1997. 325,823~829
de la terre
et des planetes
/ Eorfh & Planetary
Sciences
H. lshida
and
Contexte
M Pickford
geologique
et datation
longueur de la canine par rapport 2 P3-P4, ce specimen est consid& comme appartenant ?I une femelle (Pickford, 1986). Son gge au de&s est celui d’une jeune adulte.
Le maxillaire a eti: trouve dans les affleurements de la formation Namurungule, region de Samburu, Kenya (figure 1) (Pickford et al., 1984 ; Ishida et al,, 1994 ; Sawada et al., 1997). Une datation radio-isotopique de 9,47 f 0,22 Ma fut obtenue 2 partir d’un depat qui recouvre directement le niveau d’oh provient le maxillaire. Un sge de 9,57 f 0,22 Ma fut obtenu g partir de la coulee pyroclastique qui est immkdiatement sous-jacente au niveau 2 hominoi’de. Kous dkduisons de ces correlations de datation que l’homindide de Samburu a un 9ge de 9, j Ma. Cet gge est en accord avec la biostratigraphie des grands mammiferes (Pickford et al., 1984 a, b ; ?Jakaya et al., 1984).
La partie verticale du processus zygomatique Porte un tubercule osseux bas, qui doit rep&enter le processus malaire (figure 4). La base du zygomatique est plus proche de la rangee dentaire que chez n’impone quel homme ou grand singe actuel. mais eile ressemble Z3la position observke chez Proconsul et Morotopithecus(Pilbeam, 1969). Les racines de MZ penetrent la partie la plus basse de la racine &a&e du zygomatique. Le palais n’est pas aussi profondement voi3i. que celui des gorilles et chimpan&, mais il est plus arqu& que le palais peu profond et plus plat qui caracterise Proconsul,
Description
Morotopithecuset Rangwapithecus (figure 4). Dentition. P3 est une grande dent avec une racine linguale et
systhnatique
Superfamille Hominoidea Gray, 1825 Genre Samburupithecus gen. nov. Diagnose. Homindide de taille comparable 3 celle du gorille, dont le palais est assez profondement voDt& ; bord lateral de l’ouverture nasale & bords a&r& et ayant une inclinaison subhorizontale de 30” par rapport au plan occlusal dans la region supracanine et ant&o-canine ; fossa faciale large mais peu profonde, situee bien en avant de la racine anterieure du processus zygomatique ; racine antCrieure du processus zygomadque pneumatisee ; arcade zygomatique basse ; premolaires allongees ant&o-post&ieurement, par rapport 2 celles de Proconsulet des autres hominoi’des du Miocene ; extension de l’email vers la racine anterieure de P3 ; molaires sup&ieures 2 grand cingulum du protocBne ; email relativement epais ; jonction dentine-&nail 2 fort relief; cuspides des molaires bunodontes boursoufflees avec un plissement attenue de Yemail, bassin occlusal des molaires restreint ; M3 plus grande que M2 plus grande que M’ ; en vue occlusale, le processus alvColaire est rectiligne de C P M3. Espece Samburupithecus kiptalami sp. nov. Diagnose. Identique ~3celle du genre. Hololype.KNM SH 8531, fragment de maxillaire gauche avec une partie du palatin et du premaxillaire, l’alv&ole de la canine et P3-M’ (figure 3). Localit tpe. Site SH 22, coliines de Samburu, Nord Kenya (Pickford, et al., 1984). Datation et Horizon. Formation Namurungule, au-dessus du niveau calcaire et sous le niveau de coulee argileuse : Miocene superieur, Qe radio-isotopique 9,5 Ma. Description. KNM SH 8531 est un maxillaire/premaxillaire gauche partiel avec trois molaires, deux premolaires et l’al&ale de la canine (figure 2) (Ishida et al., 1984). Le processus alvColaire du maxillaire est rectiligne de C 2 M3, mais la M3 est 1egPrement dkjetee lingualement. D’apr+s le rapport de la
Introduction The African upper Miocene (10.5-5.5 m.y.) fossil record has previously yielded few large hominoid specimens. A
824
C. R. Acad.
deux labiales. Le paracane est plus haut que le protoc8ne et a les bards anterieur et posterieur saillanrs. Les c&es divisent la vallee sagittale en fovea anti-rieure, centrale et d&tale. Le protocbne est bunodonte et il est place plus en avant que le parac6ne. La P3 est entourCe d’un sillon hypoplastique prokminent. P4 est une grande dent triradiculke. Le paracBne a des c&es qui courent de l’extremit.+ de la cuspide vers la c&e anterieure, dans la vallee sagittale, et vers la c&e distale. Le protoc6ne est plus bas et sit& plus anterieurement que le para&ne, la couronne est entouree d’un sillon hypoplastique. M’ est mod&ment u&e. Le cingulum proilminent ceint le protoc6ne. Les sillons lingual et labial sont peu profonds et etroits. Les valliles intercuspides tendent j etre etroites mais profondes. Le bassin du trigone est restreint et les cuspides sont gonfl&es et depourvues de plissements. L’email du protocane de M’ de KNM SH 8531 est deux fois plus kpais que l’email des gorilles presentant la meme usure. M* est une version plus grande de M’, mais moins u&e. Le cingulum du protocane ne rejoint pas l’hypoc?me, bien qu’un sillon hypoplastique P cet endroit en donne l’impression. M3 est similaire mais plus grande que M’, une caractkristique inhabituelle chez les Hominoidea. Le cingulum du protocBne s’arrete au niveau de l’hypoc6ne. I1 y a un paraconule proCminent fusion& avec le cingulum anterieur. &Y$o@zie. La comparaison de Samburupitbecus avec les homino’ides mioc&es et actuels (Pickford et Ishida, en preparation) indique que celui-ci est plus proche du clade Grands Singes Africains - Hommes (AAH) (figure 5). I1 est plus probablement le taxon-fr?re du clade AAH ; mais il peut egalement appartenir P ce clade comme ancCtre des hominid&. Moins probable est I’hypoWse de proche parent avec le gorille (Andrews, 1992). La combinaison des caracteres du maxillaire de Samburupithecusindique que ce dernier occupe une position anterieure 2 1’Cvolution du clade AAH, mais qu’il etait posterieur aux hominoides du Miocene moyen, tel que le
Kenyapithecus.
lower molar from Lukeino aged about 6 Ma was originally considered to be closest in general morphology to those of australopithecines (Andrews, 1975), a view which was challenged on the grounds that the tooth was phenetically
Sci. Paris, Sciences
de la terre
et des planetes
/ Earth
& Planetary Sciences 1997. 325,023~829
A new
most like that of a chimpanzee (Corruccini and McHenry, 1980). A fragmentary mandible with a heavily worn first molar from Lothagam (late Miocene age ca 6-5 Ma) is so damaged that it is virtually unidentifiable (Kramer, 1986). In order to fill in this gap in the hominoid fossil record the senior author has led Expedition to Samburu
the Hills
on-going joint since 1980.
Because African middle and have yielded so few hominoid
upper fossils
Japan-Kenya
Miocene deposits there has been
a
tendency on the part of some palaeoanthropologists to look to the Eurasian fossil record for the ancestor of the African Ape - Human (AAH) clade (De Bonis, et al., 1990; Begun, 1992; Alpagut et al., 1996). Pickford et al. (1977) show on the basis of frontal anatomy that all Eurasian apes claimed to be hominid ancestors are derived in the direction of Pongo and are thus members of the Pongid clade. It is therefore appropriate to report the discovery, in the Upper Miocene of Kenya, of a large hominoid primate aged 9.5 Ma which is morphologically and chronologically well placed to represent clade. The specimen (KNM-SH tember, canine female
such an ancestor of the AAH 8531), discovered in Sep-
1982, consistsof much of the left maxilla with post dentition of a primate approximately the size of a gorilla.
Geological
Late
context
Miocene
hominoid
from
Kenya
and age
The maxilla was found lying on the surface of an outcrop of intra-formational conglomerate which forms a prominent cliff and dipslope at site SH 22 in the southeastern outcrops of the Namurungule Formation, Samburu District Kenya (figure I) (Pickford et al., 1984a, b; lshida et al., 1994; Sawada et al., 1997). Matrix attached to the specimen is similar to that of the intra-formational conglomerate which contains a great deal of in situ bone. Above and below the conglomerate lense is a sequence of tuffaceous shales which yield fossilized fish remains as well as pumice clasts. On the basis of its attached matrix and position in the field we believe that it is likely that the hominoid specimen was originally buried and fossilized in the conglomerate. Lavas lying unconformably below the Namurungle Formation have been dated at 12-13 Ma (Matsuda et al., 1984) while lavas which unconformably overlie the ments have yielded a date of 7.08 +/-- 0.28 Ma. A radioisotopic date of 9.47 +/- 0.22 Ma (Sawada 1997) was obtained from alkali feldspars separated
sediK-Ar et al, from
pumices in a deposit which immediately overlies the bed from which the maxilla came. An age of 9.57 +/- 0.22 Ma was obtained from alkali feldspars separated from a pyroelastic flow deposit which immediately underlies the hominoid bed. We infer from this relationship that the Samburu hominoid is close to 9.5 Ma. This age determination accords with the large mammal biostratigraphy of the formation (Pickford et al., 1984a, b; Nakaya et al., 1984).
Systematic
description
Superfamily Hominoidea Gray, Genus Samburupithecus gen. Diagnosis. Large hominoid approximately
1825 nov. the
size
of
Gorilla in which the palate is relatively deeply arched; lateral margin of nasal aperture sharped-edged and sloping at a subhorizontal 30” angle to the occlusal plane in the supracanine and antero-canine area; large but shallow facial fossa situated well forward of sloping anterior root of zygomatic process; anterior root of zygomatic process pneumatized; zygomatic arch low, premolars anteroposteriorly expanded relative to those of Proconsul and other Miocene hominoids; rootward extension of enamel on anterior root of P3; upper molars with large protocone cingulum; relatively thick enamel caps on high relief
Figure 1. location of upper Miocene (AR: Athi River; BN: Ngorora; LU: Mpesida; NA: Nakali; NC: Ngeringerowa; :‘tr ‘:::i
fossiliferous sites in Kenya Lukeino; LT: Lothagam; MP: SH: Samburu Hills).
Localisation des gisements fossiliflres du Mioc+ne Kenya (AR : Athi River; BN : Ngorora ; LU : Lukeino gam ; MP : Mpesida ; NA : Nakali ; NC : Ngeringerowa buru Hills). C. R. Acad. 1997.325,823-829
Sci.
Paris,
Sciences
de
la terre
et des
sup6rieur du ; LT : Lotha; SH : Sam-
plan&es
dentine enamel junction; inflated, bunodont molar cusps with subdued wrinkling of enamel; molar occlusal basins restricted; M3 larger than M2 larger than M’; in occlusal view the alveolar process is straight from C-M3. Species
Samburupithecus
kiptalami
sp. nov.
Diagnosis. As for the genus. Holotype: KNM SH 8531, partial left maxilla with tion of palatine and premaxilla, with canine alveolus complete
/ Earth & Planetary
Sciences
P3-M3
(figure
porand
3).
825
H. lshida
and
Type (Pickford,
Locality: et al.,
Horizon
M Pickford
Site SH 22, 1984a).
and
limestone and Fauna1 Set VI:
Age:
Hills,
Namurungule
below mud radioisotopic
Etymology:‘Samburu’ which the holotype nours Mr Kiptalam
Samburu
North
Formation,
flow member: age 9.5 m.y.
Kenya
above
Upper
Miocene,
refers to thedistrict in Kenya from was collected, the species name hoCheboi, a member of the joint Japan-
Kenya Expedition, who found the specimen. Informally in the literature this hominoid has been called the Samburu Hominoid as well as Motopitbecus. At present the latter name is a nomen nudum but could be validated by us, but because the genus Morotopithecus has recently been erected possible therefore
by Gebo et al. (1997), confusion between two erect the generic name
we prefer to avoid such similar names Samburupithecus.
0 L
and
M3
are
little
4 I cm
Figure 3. Profiles of the maxilla of Samburupithecus taken at P“ and MZ to show facial fossa (F) and low position notch of the zygomatic root (M). ,r,,& /!a
length of C relative to P3-P4 this specimen is considered to represent a female, given that the ratio C/P3-P4 was dimorphic to the same degree as it is in gorillas (Pickford, 1986). It was a young adult when it died: its M’ is in medium wear M2
M2
any and
Description: KNM SH 8531 is a partial left maxilla/ premaxilla with three molars, two premolars, and the canine alveolus (figure 2) (Ishida et al., 1984). The alveolar process of the maxilla is straight from C-M3, but the M3 is slightly offset lingually. By inference from the ratio of the
while
SH 8531
worn.
Profils du maxillaire de Samburupithecus kiptalami p? et MZ montrant /a fosse faciale (F/ et /a position malaire du zygomatique (MI.
The region
maxilla is slightly crushed, principally and much of its surface is weathered.
pris basse
kiptalami of malar
au niveau de du tubercule
in the palatal It was found
in four pieces which have been accurately reconstructed since the edges of the pieces fit well against each other. The general proportions of the maxilla can be estimated within reasonable limits. The zygomatic process of the maxilla has a long forward-sloping anterior root which merges anteriorly into a large but shallow facial fossa. The vertical portion of the zygomatic process carries a tubercle of bone low down which may represent the malar process (figure 4). The base of the zygomatic is closer to the tooth row than it is in any living great apes or man, but resembles the position observed in Proconsul and Morotopithecus (Pilbeam, 1969). The upper part of the zygomatic root is missing, and a large maxillary sinus, now partly filled with matrix, can be discerned. The sinus extends forwards into the anterior root of the zygomatic process as it does in Gorilla and Pan. The roots of M2 penetrate the lower part of the flaring zygomatic root, which suggests that the zygoma are low in Samburupithecus. In all specimens of fan, Gorilla, fongo and Homo available for comparison in the Kenya National Museum, the molar roots do not reach upwards as far as the flaring root zygomatic process. In this respect Samburupithecus calls Proconsul and Morotopithecus.
Figure 2. Occlusal Samburupithecus ,: “- : Vues occlusale Samburupithecus
a26
and lateral view of KNM SH 8531, kiptalami nov. gen., nov. sp. et /at&a/e kiptalami
de KNM SH 8531, nov. gen., nav. sp.
left
A small portion of the margin of the nasal aperture is preserved in SH 8531 from a point above the canine root for a distance of about 20 mm. It slopes at a subhorizontal angle of 30” relative to the occlusal plane, quite unlike the steeply oriented nasal margin in man and Rangwapi-
maxilla,
thecus.
maxi/lake
anterior
gauche,
C. R. Acad.
of the re-
slopes Sci. Paris,
Sciences
The lateral and medial downwards de
la terre
part of the floor of the nasal aperture to the canine root is sharp-edged and and forwards, unlike the rounded and et des
plan&es
/ Eari%
& Planetary Sciences 1997. 325,823-829
A new
Late Miocene
hominoid
from
Kenya
In lateral view the alveolar margin of SH 8531 curves upwards anteriorly much less than it does in Pongo, and in this respect it is similar to Pan and Gorilla. In occlusal view the alveolar process is straight from C-M3, as in most non-human hominoids. The alveolar process is preserved from the anterior part of the canine alveolus to the rear of M3. The absence of an incisor alveolus in the small portion of premaxilla preserved in front of the canine, suggests that there was probably a diastema in SH 8531. The canine alveolus is abraded laterally, so it is not possible to obtain the complete cross-sectional shape of the canine root. However, in its preserved parts, the alveolus resembles those of female gorillas, especially in the rounded shape of the postero-lingual corner and by its size relative to the premolars. Itdiffers in shape and orientation from the more uniformly
oval
alveolus
of Pongo
and
Homo.
Dentition. P3 is a large tooth with one lingual and two labial roots. The anterior edge of the paracone projects forwards and would have slightly overlapped the canine in labial view. A small contact facet for the upper canine is preserved on P3 near the labial margin of the anterior surface of the tooth. The position of this facet is similar to that seen in female gorilla specimen number OM 3544 in the Kenya National Museum. Enamel extends onto the anterior labial roots, much as in Gorilla and Pongo. This feature in hominoid P3s is correlated with the possession of a honing function in P, and it seems likely that Samburupithecus would have possessed such a feature in its lower P,. The paracone is higher than the protocone and
OM 3264 GOrilla
0 I
has sharp anterior and posterior edges. Ridges which are almost obliterated by wear and erosion lead into the sagittal valley. These ridges divide the sagittal valley into anterior, central and distal foveae. The protocone is bunodont and is placed further forwards than the paracone. It
5 4
I cm
Figure 4. Sections of palates (at M’) of fossil and apes to show palatal depth (arrow shows position holotype of Samburupifbecus kipfalami). k*t$mm:
extant African of break in the
Coupes des palais (prises au niveau de M’) des grands singes fossiles et vivants montrant /a profondeur du palais (la f/&he une cassure dans I’holotype de Samburupithecus kiptalami).
raised
floor
of the
nasal
aperture
in Pan
but
africains indique
resembling
some specimens of Gorilla (e.g. OM 3543 in the National Museum of Kenya). The palate is not as deeply arched as those of gorillas and chimpanzees, but it is much more deeply arched than the shallow and flatter palate that typifies Proconsul, Morotopithecus, and Rangwapithecus (figure 4). In SH 8531 a short portion of the inter-palatine suture is preserved opposite M ’ - 2 , but since the palate is slightly crushed, reconstructions of palatal breadth will need to take into account the displacements of bone involved in the crushing. Because the damage is due to minor faulting accompanied by rotation of slivers of palate, reconstruction may be possible. However, suture preserved is short, we cannot arcade shape with confidence. C. R. Acad. Sci. Paris, Sciences 1997. 325,823~829
because the length of reconstruct the dental
de la terre
et des plan&es
/ Earth
has two ridges which rior ridges respectively. hypoplastic groove.
lead towards the anterior and posteThe P3 is encircled by a prominent
P4 is a large oval three-rooted tooth. On the anterior labial margin of the paracone is a low crest. Otherwise, the labial surface of the paracone is smoothly curved. The paracone has worn and eroded occlusal ridges which lead from the area of the cusp tip towards the anterior ridge, into the sagittal valley and towards the distal ridge. As with the P3, these ridges define the edges of the anterior, central and distal foveae. The protocone is lower and more anteriorly situated than the paracone. Perikymata are clearly visible on the worn surface of the paracone, and the crown is encircled by a hypoplastic groove. M’
is a moderately
worn
tooth
with
on the protocone, paracone, metacone small chip of enamel is missing from
dentine
exposures
and hypocone. A the tip of the para-
cone. A prominent cingulum borders the protocone, but it does not lead onto the hypocone. The anterior cingulum is inflated and the anterior fovea is consequently filled in and rather small. The distal fovea is open and moderately deep. The lingual and labial notches are shallow and narrow. The intercusp valleys tend to be narrow but deep, so that cusps are still separated even after moderate wear. & Planetary
Sciences
H. lshido
and
The trigon remarkably
M Pickford
basin free
is restricted of wrinkles.
Enamel thickness. Although the style of wear in Samburupithecus molars suggests that they are thin enamelled,
and the cusps are inflated and This suite of features is prob-
ably related to the possession of relatively thick enamel caps in the molars. The enamel on the protocone of M’ of KNM SH 8531 is more than twice as thick as enamel in similarly worn gorilla molars measured at homologous
such is an illusion caused by a high relief dentine enamel junction. The enamel on the protocone of M’ in SH 8531 is 2.2 mm thick. In a gorilla specimen (OM 3264) at a comparable wear stage, the enamel is 1 mm thick. The
points. M* is basically a larger version of M’, but is less worn. The protocone cingulum does not lead onto the hypocone although a hypoplastic groove at this level gives the impression that it does. There is a small ridge which
relief of the dentine enamel junction in Samburupithecus molars is high. It compares well with most lower Miocene hominoids as well as living African apes and man. It differs markedly from Kenyapithecus, Heliopithecus, Afropithecus, Sivapithecus, Ouranopithecus and Pongo which
runs from the protocone M3 is morphologically an unusual feature in
tip onto the lingual cingulum. similar to but is larger than M’, Hominoidea. The distal ridge is
inflated and lightly beaded. The protocone cingulum stops at the hypocone as in M’ and M2, but is joined by a crest to the tip of the hypocone. The wear in this tooth is greater on the labial cusps than on lingual cusps which are virtually unworn. The tip of the protocone is marked by a scattering of hypoplastic pits. There is a prominent paraconule fused to the anterior cingulum. An unusual feature of the molars is that M3 is larger than M2 and M’. Such inter-molar proportions are found in Rangwapithecus, although
but do not occur
Australopithecus
in other
afarensis
hominoid sometimes
taxa ap-
proaches this condition. The enamel surface possesses remarkably subdued wrinkling and other surface ornamentation, and Samburupithecus therefore differs from most hominoids, in particular Rangwapithecus and Pongo, in which secondary wrinkling is well developed.
have considerably enamel junction.
more
subdued
relief
of
the
dentine
The wear gradient in the cheek teeth of SH 8531 is comparable to that seen in gorillas and chimpanzees, but is not as marked as it is in Sivapithecus. The main wear facets on P3, p and M’ are oriented much as in Gorilla and other African hominoids.
Phylogeny. ocene
and
Comparison extant hominoids
of
Samburupithecus (Pickford
and
lshida
with Miin prep.)
indicates that it is most closely related to the African Ape Human clade (AAH) (figure 5). It is most likely to be the sister group of the AAH clade. Andrews (1992) has proposed that it should be positioned within this clade as the ancestor of the gorilla but we consider that the dentition of
Samburupithecus as Praeanthropus
is closer
africanus
to that of early hominids from Laetoli and Kanapoi
such and
upper premolars of Samburupithecus are mesioenlarged in comparison with the premolars of Miocene apes, with the exception of Rangwapithecus. In their general proportions the P3 and P4 of SH 8531 are similar to those of living apes and man. Dental
The distally lower
dimensions
are
listed
in Table.
Samburipithecus
Eurasian Apes Table. ::9::Y
Dimensions
Mensurations
of the des dents
cheek
jugales
teeth de KNM
KNM
SH 8531.
SH 853
1.
Middle Miocene African Apes C*
ap tr root
lle 9e 23e
length
Early Miocene African Apes
P3
ap labial ap sagittal tr
10.5 8.6 11.7
P
w tr
9.8 12.7
M’
w tr
13.9 13.3
MZ
w tr
15.7 15.8
M3
w tr
16.6 16.8
P3-M3 Ml-M3 P3-p4
ap: antero-posterior;
828
Position syst@matique simp/ifEe de Samburupithecus. (AAH inch Praeanthropus, Australopithecus, Paranthropus, Homo, Pan, Gorilla et Ardipithecus ; Eurasian Apes inclue Griphopithecus, Dryopithecus, Oreopithecus, Ouranopithecus, Ankarapithecus, Platodontopithecus, Sivapithecus, Lufengpithecus, Gigantopithecus et Pongo Middle Miocene African Apes inclut Kenyapithecus et Otavipithecus ; far/y Miocene African Apes inch Proconsul, Afropithecus, Heliopithecus et Morotopithecus).
64.5 46.4 18.5
sagittal sagittal sagittal tr: transverse;
e: estimate. C. R. Acad.
Figure 5. Simplified phylogenetic position of Samburupithecus. (AAH include Praeanfhropus, Australopithecus, Paranthropus, Homo, Pan, Gorilla and Ardipithecus; Eurasian Apes include Griphopithecus, Dryopithecus, Oreopithecus, Ouranopithecus, Ankarapifhecus, Platodontopifhecus, Sivapithecus, Lufengpithecus, Cigantopithecus and Pongo; Middle Miocene African Apes include Kenyapithecus and Otavipifhecus; Early Miocene African Apes include Proconsul, Afropithecus, Heliopithecus, and Morotopithecus). W&Ww)
Sci. Paris,
Sciences
de
la terre
et des
plan&es
/ Earth
&
Plonetafy Sciences 1997.
325,823-829
;
A new
to be in the direct ancestry of an exclusive ancestor of the gorilla. Among characters supporting this view are several unusual features including M3 larger than M2 (occurs in some specimens assigned to Australopithecus afarensis and Paranthropus boiser), the molar cusps relatively free of wrinkling, restricted molar occlusal basins, the large and inflated protocone cingulum and the antero-posteriorly elongated premolars. The deeply arched palate, the antero-posteriorly elongated premolars, the position and extent of the facial fossa and the sharp-edged anterior nasal margin are plesiomorphic for the AAH clade. Samburupifhecus lacks the derived characters that unite the Eurasian Apes into a single (Pongo} clade whereas it retains several plesiomorphic features such as low position of the zygomatic arch that occur in Early and Middle Miocene African Apes. it is thus hominids
more
rather
likely
than
Late Miocene
hominoid
from
Kenya
Summary. The salient morphological features of the Samburupithecus kipfalami maxilla include its large size; palate arched more deeply than in Proconsul, Morotopithecus and Afropithecus, but not as deeply as in fan, Gorilla and hominids; sharp-edged nasal margin; low, retired zygomatic root; and straight cheek tooth row. The sharp-edged nasal margin is similar to some gorilla specimens but this character is variable and its value for systematics is uncertain. The combination of dental and maxillary features of Samburupithecus indicates that it occupies a position close to the African Ape - Human (AAH) clade, but was posterior to middle Miocene hominoids such as Kenyapithecus (figure 5). Within the AAH clade, Samburupithecus is closest in dental morphology to primitive hominids such as Praeanthropus. As such it throws a great deal of light on the late Miocene ancestry of humankind.
Acknowledgements: of Education, P. Taquet and
We thank the Government of Kenya and Director of the National Museum of Kenya, the Japanese Ministry Science and Culture and Prof. S. Ishida, H. Mitsushio. J. Itani, J. Ikeda. K. Hanihara. S. Matano, Y. Coppens and Drs T. Makinouchi, T. Koyaguchi. H. Nakaya. T. Matsuda and Y. Nakano. In particular we thank Mr Kiptalam Chepboi.
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& PJctnetav
Sciences
T and lshida Ann. Meeting