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Phylogenetic implications of the first African Middle Miocene hominoid frontal bone from Otavi, Namibia
0 Academic des sciences / Elsevler. Paleontology / Palkontologie (Human paleontology / Palkontologie
Paw humaine)
Phylogenetic implications Middle Miocene hominoid from Otavi, Namibia
of the first African frontal bone
Implications phylog&n&iques du premier OS frontal d’un Hominoi’dea du Mioc&ne moyen d’otavi, Namibie Martin
PICKFORD’
! Salvador
MOYA
’ Chaire depal~oal?thro~ologte et depr&stoire,
SOLAR
and Meike
K~HLER’
CollGgedo France and .Vfuseumnuttonul d’histoire naturelle.
IFA
12 du C!V?S, 8. mt? Buffin,
75005 Paris, France
’ Institllt de I’uleorztologxa .M. Cr~.sujiint. E.scolaIndz~stnal23, 08201 Subau’ell, Burcelonu. Spain
ABSTRACT The discovery of a hominoid frontal at Berg Aukds, Namibia, aged 13-12 Ma, permits an analysis of the phylogenetic relations between fossil and extant great apes. The Namibian specimen is closer morphologically to African apes and humans (MH), whereas all fossil Eurasian great apes differ markedly from MH but are closer to the F’ongo clade. Keywords:
Hominoidea,
Fronfd
bone,
Middle
Miocene,
Namibia.
Phylogeny
La dkcowetie d’unfrontal d’fIominoidea d Berg Aukas. Namibie, a& de 13-12 :zla, permet I’analyse des relations phylo@nBtiques parmi les grands singes jossiles et vivants. L ‘&chantillon de Namihie s’a&re movphologiquement pro&e des singes af?icain.s et des hommes (AAH), tandis que tous les singesfossiles eurasiatiques s’t?loi’went de.sAAH et s’approchent du clade de Pongo. Mob
cl&s : Hominoidea,
OS frontal,
Miocene
moyen,
Namibie,
Phylogbnie
VERSIONABR~~G~E Introduction
et 8ge
Un frontal d’Hominoidea, Bh 52’94, a Cte decouvert dans un bloc de b&he r&zolte en 1994 5 Berg Aukas (Namibie). une localite des paleokarsts de la region des monts Otavi. La pr¶tion i l’acide a livre de tr& abondants microfossiles, dont l’association sugg?re un Ige de la fin du Miocene moyen (12-13 Ma). proche de celui des gisements de Fort Ternan et Ngorora au Kenya (Pickford, 1986).Des hr?ches identiques avaient deja livre des restes d’Hominoidea attribues 2 Otavzpi&ecus namibiensb (Conroy et al, 1992, 1993 : Senut et al., 1992). Otampithecus appartient ?I une periode int&essante. appelke I le trou noir des Homino’ides d‘Afrique j’ et qui a livrC trPs peu d’Homino’ides (Pickford, 1985). I1 est post&ieur aux xore prbxk Note remix
autres Hominoi’des de grande taille du MiocGne infkrieur d‘Afrique orientale, chez lesquels le frontal est connu, in&ant Proconwl (Walker et al., 19X3), Ajiropithews (Leakey et al.. 1988a) et Turkanapithecus (Leakey et al., 1988b). I1 prec?de les Hominoi’des eurasiatiques chez lesquels l’anatomie frontale est connue : Dvopithecus (Maya Sola et Kohler, 1993, 1995 ; Kordos, 1991), Ouranopithecus (de Bonis et Koufos. 1993 ; de Bonis et al., 1990), Ankarapithecus (Alpagut et al., 19961, SiLaapithecus (Preuss, 1982) et Lz~engpithecus (WI, 1984).
Anatomie Le fossile reprksente la plus grdnde partie dL. frontal, dont les bords sent absents. Le su1cu.s sztpraorbitalis n’est pas conserve. Lateralement, entre la crtte supercilidire et la c&e temporale,
par Yves Coppens le 26 dkembre
1996, accept&
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et des planktes
1997
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et al.
on observe une depression peu profonde, mais large. La crt?tr: supraciliaire du specimen d’Otavi est &troite : il n’y a pas de sulcus supraoral. LaGralement, on observe un sulcus peu profond entre la c&e supraciliaire et la crete tempordle. La mesure de l’image-miroir du frontal donne 24 mm environ pour la largeur interorbitaire entre les coins mksio-distaux des orbites. Les c&es temporales du frontal d’Otavi som ac@es et surplombent les fesses temporales. I1 y a deux sinus proeminents. mais inegaux. dans la region supraorbitale de BA 52’94 (figures 1 et 2). Une partie des sinus frontaux isole le plan orbitaire de la surface supkrieure du frontal, comme chez les grands singes africains et l‘homme actueki, mais i la difference de la situation obsen+e chew Dr-ypithecus, chez qui les sinus frontaux sont restreints ?i la proximite du nasion (figure 2). Che7 les grands singes africains actuels et les hominid& (AAH), le sinus frontal remplit tout l’espace sit& sous et derriere la glabelle j il atteint lateralement les parties moyennes des dew rebords supraorbitaux, s’etend posterieurement dans l’tcaille frontale et inferieurement dans la zone interorbitaire, et de 18 post&o-inferieurement, pour rencontrer le sinus ethmoi’dal. Les rkgions conservees du frontal d’Otavi s’accordent tout g fait avec cette description. Parmi les grands singes Homino’ides du Miocene infkrieur d’hfrique, de tcls sinus frontaux ont etil signal& chez l+oconszll n~wwae (crsne de Rusinga trouve en 1948) (Le Gros Clark et Leakey, 1951 ; Walker et al., 1983), Turkanupithecus (Leakey et al., 1988 b) et Afiopitk~ecus (Leakey et al., 1988 a). Un fragment non d&rit d’une orbite gauche provenant de Napak en Ouganda (Napak V, 1964) attribuable 2 un Homino’ide de grande taille (probablement Procon.%.d vrzzjoc connu sur plusieurs sites g Napak, et incluant Nap V) consiste en une portion sup&o-IatCrale de l’orbite. Shea (1988) a estime que ‘cle d&eloppement d’un vrai sinus ethmofrontal ktait un caractsre derive reliant les grands singes africains et l’homme ‘pet qu’il etait associe 2 une klinorynchic. Comme Brown et Ward (1988). nous consid&ons que la condition dilrivee est representee par les grands singes eurasiatiques; chez qui le sinus frontal est reduit ou absent, une morphologie associee 5 l’airorynchie. Begun (1985) a affirm6 que Dryopitbecus possedait de grands sinus frontaux. mais nos observations suggilrent qu’en fait, il n’en est rien : les sinus frontaux de Dvopithecus sont petits et limit& 2 la region du nasion. La presence de sinus frontaux supraorbitaires chez SizJupirbecus (Pilbeam et Smith, 1981) n’a pas kte confirmi-e par les travaux plus recents de Preuss (1982). De Bonis et al. (1990) ont postule qu’ Ouranopitheus est ancestral par rapport i Austrdopithecus. Si cela iltait le cas, il
Introduction
and age
An adult hominoid frontal bone, BA 52’94, was found in a breccia block collected in 1994 at Berg Aukas, Namibia, a palaeokarst locality in the Otavi Mountains. Acid digestion of the block released an extensive crop of microfossils and several isolated teeth of Otavipithecus. The microfauna from BA 52’94 is the same as that from the breccia, which yielded the holotype of Otavipithecus namibiensis,
460
C. R. Acad.
SCI. Paris,
devrait posseder de grands sinus frontaux du type AAH ; or. cela ne semble pas &tre le cas. Au contraire. la marphologie frontale dans la region supraorbitaire est comparable 5 celle obsen& chez D yopithecus et m@me Sivapithecus, indiquant son appartendnce au &de de Pongo. Chez Po?zgo, il n’y a pas de sinus frontaux (Winkler et al., 1988). tandis que chez Dyopithecus. le sinus est confine $ la region paranasale et ne p&Gtre pas vers le haut, dans l’ecaille du frOntal. ou lateralement, ddns les c&es supraorbitaires (Maya Sola et Kohler, 1995) (figure 2). La meme absence de sinus frontaux a et6 signal& chez Sioapithec#s (Preuss, 1982) et Lufengpithecus (Wu, 1984). La decouverte recente d’un crine d’hkarapithecus (Alpagut et al., 1996) suggererait que ce dernier possi-de un sinus frontal etendu. Pour qu’AnkavapitbeGUSsoit considkri- comme un Hominoi’de primitif, ainsi que le suggt:rent Alpagut et al. (1996), il faudrait que les sinus frontaux envahissent l‘ecaille du frontal et les &es supraorbitaires. L’anatomie du frontal afflaiblit considerablement toutes les hypotheses qui reconnaissent les grands singes du Miocene terminal d’J?urasie comme des ancetres du clade AAH (Begun, 1995). Bien qu‘il ne possPde pas toutes les apomorphies des AAH, Otaugitbecus presente des caracrPres morphologiques qui ne l’excluent pas de cette ancestralit&
Phylogbnie Dans le passe, de nombreux Hominoi’des mioc?nes ont joue tour 2 tour le r81e d’ancetres des Hominides (‘3e Bonis et al., 1990, Begun, 1995 ; Dean et Delson. 1992 ; Wu et al., 1986 ; Alpagut et al., 1996). Xous considerons ces hypotheses comme invalidees, car lous les pretendants eurasiatiques 2 l’ancestralit6 des AAH ont des sinus de petite taille ou absents dans I’&zaille du frontal. En conclusion, nous pouvons dire que Otaz,ipitbecus souligne une origine africaine du clade AAH et affaiblit considerablement 1’hypothPse d’une origine eurasiatique ; que le frontal d’Otar?zpitbecus, aux sinus tr&s d&eloppes, :#ugg&e que la r&iuction de sinus chez D yopithecus et Guranopithecus, represente une morphologie d&i&e vers les conditions trou&es dans le &de de Pofzgo; enfin, les grands singes du MiocGne terminal d’Eurasie sont phylog+netiquement plus proches des Pongidae asiatiques (Sivapitbecus, Lufengpitbecus et Po?zgoj que du clade des AAH. Ils semblent, en owe, former leur propre ckdde (contenant Dyopithecus, An,karapithecus et Ouranopithecus) au sein de la famille des Pon,qidae.
and it indicates that the sediments accumulated during the latter part of the Middle Miocene (12-13 Ma) approximately at the same time as the sites of Fort Ternan and Ngorora, Kenya (Pickford, 1986). Similar breccias from the site have previously yielded remains of hominoids classed as Otavipithecus namibiensis (Conroy et al., 1992, 1993; Senut et al., 1992). Otavipithecus occupies an interesting period of time, the so-called “hominoid black hole” of Africa, from which very few homino’id fossils have Sciences
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1997. 325,459-466
Miocene been
recovered
bodied including (Leakey 1988b) Eurasian known:
(Pickford,
1985).
It post-dates
other
1991) Ouranopithecus Sol& and Kbhler, 1993, al., 1996), Sivapithecus ecus (Wu, 1984).
Anatomy
(de Bonis and Koufos, 1995), Ankarapithecus (Preuss, 1982), and
1993; Moy& (Alpagut et Lufengpitb-
of BA 52’94 most and
of its tem-
crests are preserved. The endocranial surface is in a condition and is broken anteriorly to reveal an extenfrontal sinus. The outer table is in excellent condition. the Otavi frontal there is no supraorbital torus. Laterbetween the superciliary ridge and the temporal crest
there is a shallow but wide depression, which corresponds in position to the lateral part of the post-toral sulcus in Pan. In Dryopithecus ciliary ridge,
which
from the rest of the frontal, shallow superciliary groove
(Moyg SolA and K8hler, 1995) the superhas a roughened surface, is separated
which that
frontal
bone
is smooth, runs parallel
from
Namibia
by a long but to the super-
ciliary margin but some 10 mm behind it before culminating medially near the superciliary notch. This groove separates the superciliary eminence frorn the temporal crest. A similar morphology occurs in S/vapithecus and Pongo with the exception that the superc:iliary groove is narrower and deeper and the medial end of the roughened superciliary crest extends further medially and then descends inferiorly as far as nasion. The Otavi frontal, with its smooth superciliary crest and wide postorbital sulcus is close in morphology to Proconsul africanus and extant African apes and humans (AAH), despiie its lack of a bar-like
The fossil is a large part of a frontal bone lacking margins (figure 1). However, parts of the orbits poral poor sive In ally
large-
hominoids in which the frontal bone is known, Proconsul (Walker et al., 1983), Afropitbecus et al., 1988a) and Turkanapithecus (Leakey et al., from East African lower Miocene sites but predates hominoids for which the frontal anatomy is Dryopithecus (de Bonis et al., 1990; Kordos,
hominoid
supraorbital
torus.
On the right side of the fossil the supraorbital notch interrupts the superciliary ridge mesially, but it is not very marked. In Dryopithecus the superciliary notch coincides in position with the mesial end of the superciliary groove, and in this respect the frontals of Otavi and Dryopithecus are quite different. The superciliary ridge of the Otavi specimen is narrow, as in many Miocene hominoids. Its superior surface is marked on the right side by a sharply defined, but narrow, groove that enters a nutritive foramen medially. There is no supratoral sulcus in the zone distal from and between the supraorbital notches. The upper surface of the Otavi frontal is even slightly elevated in the region where a depression usually exists in extant African apes and in extinct forms such as Dryopithecus (Moyil Sola and Kiihler, 1995). In this Rusinga Proconsul low sulcus between
respect it is comparable nyanzae skull. Laterally the superciliary ridge
to the 1948 there is a shaland the tempo-
ral crest. Medially this slight depression is b’ordered by low ridge of bone, which crosses the frontal obliquely from the temporal crest towards glabella, as described Afropithecus (Leakey et al., 1988a). A similar low ridge bone occupies an analogous position in the frontal Dryopithecus. The post-glabellar frontal far back in comparison with Afropithecus, of the area delimited by the oblique
a in of of
sulcus is located the anterior part hotly temporo-
glabellar ridges having been raised upwards in responseto the development of extensive frontal sinuses. The postglabellar frontal sulcus is bordered laterally by raised flanges, which delimit the distal portion of the temporal crest. At glabella there is weakly developed but palpable mid-line depression, which appears with be homologous with the depression that occurs in the dorsal surface of the supraorbital torus in fan, Gorilla and humans as well as in some fossil forms including Dryopithecus (Maya Sola and Kbhler, 0
1
2
Figure 1. Superior (A) and anterior (B) views of the Otavi frontal temporal ridges; 2: extent of the sinuses). Note the wide interorbital pillar and the thin superciliary arches (scale in cm). : Vues supkieure (A) et antkieure (B) du frontal temporales; 2: extension des sinus). Noter le large et /es fines arches supraciliaires I&he//e en cm).
C. R. Acad. Sci Paris. Sciences 1997. 325,459-466
de la terre
d’Otavi (I: c&es pilier interorbitaire
et des planetes
(1:
1995).
It is difficult to measure the width of the interorbital region directly, because on the left side o111y a very small part of the orbital margin is preserved. However, measurement of mirror image reconstructions of the frontal yield a figure of ca. 24 mm for the interorbital the mesial-dorsal corners of the orbits. size of the frontal this measure is large, orbits were wide apart.
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breadth between Considering the meaning that the
461
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The temporal crests of the Otavi frontal are sharp ure 1) and overhang the temporal fossa, being not different in this respect from Proconsul. They overhang
(figvery the
fossa more than those of Afropithecus and Dryopithecus and are not like those found in more encephalised modern African apes where there is no overhang. The temporal crests are wide apart immediately behind the orbits and converge distally, but do not meet in the midline in the preserved parts of the specimen. from glabella, the two temporal apart.
Forty millimetres crests are still
distal 30 mm
On the right side of the frontal, parts of the superior and mesial margins of the orbit are preserved. The angle between these parts is relatively abrupt giving the impression that the orbit is of the D outline type rather than the oval
Figure 2. Extent and Otavipithecus nasion).
type. But in such a fragmentary specimen one can not go further than this. The endocranial part of the frontal is poorly preserved although part of the groove for the superior sagittal sinus can be observed in the midline. A groove for a meningeal left half of the
vessel frontal
is prominent and several
Extension Otavipithecus nasionl.
in the better preserved arachnoid granulations
Among
developed (figures
si1 and
slightly to the right of the midline of the frontal. The lateral half of the right sinus is partly filled with cancellous bone (representing a pathological condition?), so that only the
nasion (figure 2), and thereby only separate the plate from the endocranial surface of the frontal paranasal region. In this respect the Otavi frontal different from that there are no frontal
of Pongo sinuses.
and
Sivapithecus
Miocene
hominoids
men. The interlinking and there suggesting
and in of
orbital in the is very
superciliary surface vermiform grooves are three post-mortem that the specimen
In extant sinus fills
African all the
in which
sinus in hominoids Apes space
and Hominids (AAH) the below and behind glabella
462
frontal and it
Sci.
undescribed fragment of (Napak V, 1964) assign(probably Proconsul masites at Napak, including
is patterned as in extant depressions was chewed
with shallow African apes, in the ridge, by carnivores.
in the frontal condition.
squama
in our opinion, a plesiomorphic one, already present Lower Miocene hominoids. Nevertheless, the extant can apes and humans appear to be more klinorynch their Lower Miocene predecessors, and in this sense, was partly right to think of the extant AAH as derived
superior to nasion we cannot to the ethmoidal sinus, but we was indeed present in Otavipi-
C. R. Acad.
similar
rep-
Shea (1988) has argued that “the development of a true ethmofrontal sinus appears to be a derived trait linking the African apes and humans” and that it is linked to klinorynchy. We, like Brown and Ward (1988), cannot agree with him entirely; on the contrary, we consider that the derived condition is represented by the Eurasian apes in which the frontal sinus is reduced or suppressed entirely, a morphology linked to airorynchy. The AAH condition is,
reaches laterally to the middle parts of both supraorbital rims, extends posteriorly into the frontal squama and inferiorly into the interorbital area and thence posteroinferiorly to connect with the ethmoidal sinus. Where preserved the Otavi frontal accords with this topography. As a result of breakage demonstrate connection infer that this connection thecus.
Africa,
et 3:
In the posterior view, the anterior surface of a large sinus is preserved, extending laterally to the edge of the specimen near the zygomatico-frontal suture. This sinus divides the frontal squama into two portions, a superior plate and an orbital plate, very much as in Pan and Gorilla. All this suggests that extensive sinuses resent the primitive hominoid
The frontal
from
(2 gauche) 2: &belle;
site Nap V) consists of the superior-lateral portion of the orbit. Posteriorly there is a smooth post-orbi-tal sulcus, and there was evidently a gap between the superciliary ridge and the temporal line in this specimen. The relationship between this surface and the superior part of the orbit reveals that there was no supraorbital torus in this speci-
medial part is open. The left sinus is appreciably larger than the right one and it crosses over to the right side where it lies above and slightly distal to the right sinus. Part of the frontal sinus separates the orbital plate from the African apes Dryopithecus to the vicinity
Lower
ithecus(Leakey et al., 1988a). An a left orbit from Napak (Uganda) able to a large-bodied hominoid jor, which is known from several
2). These ascend into the frontal from the vicinity of nasion (which is not preserved in this specimen). The two sinuses are separated from each other by a wall of bone positioned
superior surface of the frontal as in extant humans, and unlike the situation in which the frontal sinuses are restricted
sinus dam /es frontaux de Dryopithe’cus (;1 droitel (coupes sagittalesl (7: simls;
extensive frontal sinuses have been reported to occur in Proconsul africanus (as the 1948 Rusinga skull was known at the time) (Le Gros Clark & Leakey, 1951; Walker et al., 1983), Turkanapithecus (Leakey et al., 1988b) and Afrop-
are present. There are two prominent but unequally nuses in the supraorbital region of BA 52’94
des
of the sinuses in the frontals of Dryopifbecus (left) right (sagittal sections) (1: sinus; 2: glabella; 3:
Paris,
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in Afrithan Shea with
& Planeby Sciences 1997. 325,459.466
Miocene
respect
to
their
disagree with plesiomorphic
Lower
Miocene
precursors.
Where
we
hominoid
African
Apes
frontal
Hominidae
bcne
from
Dryopitkcus
Namibia
Pongme
him is in his assertion that the Asian apes are with respect to Lower Miocene hominoids.
Begun (1995) on the basis of the Spanish and Hungarian dryopithecine fossils, has argued that Dryopithecus has large frontal sinuses, but our observations show that the frontal sinuses in this genus are small and restricted to the immediate vicinity of nasion, whereas in AAH, sinuses are extensive and invade the frontal lateral from the midline and extend deep into squama, thereby forming extensive supraorbital The
existence
of supraorbital
frontal
sinuses
the frontal bone well the frontal sinuses. in Sivapitb-
ecus (Pilbeam and Smith, 1981) has not been confirmed by a more recent study (Preuss, 1982), the supposed sinuses being due to postmortem loss of cancellous bone. De Bonis et al. (1990) have postulated that Ouranopitbecus is ancestral to australopithecines, in which case it would be expected to possess frontal sinuses of AAH type, but this appears not to be the case. Instead, the frontal morphology in the supraorbital region, where it can be observed in the fractured surface between the splanchnocranium and the neurocranium, is comparable to that of Dryopithecus and even Sivapitbecus, indicating its relationships to the fongo clade. Other features of the splanchnocranium of Ouranopithecus, such as the shape of the premaxilla, the heteromorphic upper incisors and others, accord with the frontal morphology, indicating its close
affinities
In Pongo
with there
the
Pongo
lineage.
is no frontal
sinus
(Winkler
et al., 1988),
while in Dryopithecus the sinus is confined to the paranasal region and does not penetrate upwards into the frontal squama or laterally into the supraorbital costae (Maya Sola and KGhler, 1995) (figure 2). Similar lack of frontal sinuses has been reported in Sivapithecus (Preuss, 1982) and Lufengpithecus (Wu, 1984). The recently discovered cranium of Ankarapithecus (Alpagut et al., 1996) is reported to possess an extensive frontal sinus, but the position and extent of the sinuses have not been described in detail. For Ankarapitbecus to be a stem hominoid as was postulated by Alapgut et al. (1996), the frontal sinuses would have to invade the frontal squama and the supraorbital costae. In other aspects of the splanchnocranium (premaxillary morphology, positions of infraorbital foramina, supraorbital morphology, dentition) Ankarapithecus is similar to Our;]nopithecus and Sivapithecus, longs to the Pongo clade. frontal anatomy has been
and we believe that it beAll Eurasian apes in which studied in detail, both extinct
and extant, possess reduced sinuses in the frontal squama (table) or have none at all. There can be little doubt that the reduction (1) or suppression (2) of frontal sinuses in the Eurasian lineages represent derived morphological conditions among hominoids. As such, frontal anatomy greatly weakens all hypotheses in which Eurasian Late Miocene apes have been proposed as candidates for the ancestry of the AAH clade (Begun, 1995). This is because the enlarged frontal sinus of extant AAH would have had to have evolved from ancesC. R. Acad. Sci. Parls, 1997. 325,459.466
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Figure 3. Proposed hominoids discussed morphic condition superciliary arch); glabella; C: supraorbital depressed glabellar
phylogenetic relationships of large-bodied in the text based on frontal anatomy. A: plesio(extensive sinus, no supraorbital torus, thin B: bar-like supraorbital torus with projecting costae with juxtaposed temporal crest, area and reduced or absent siinus.
Relations
phylog&@tiques chez /es Hominoib’es de grande tail/e, discutkes 2 park des caractkes de I’anatomie fron tale. A : condition pkiomorphe (sinus &endu, pas de torus supraorbitaire, arcade supracilaire fine) ; B : lows supraorbitaire en forme de barre avec glabelle projet6e ; C : &es supraorbitaires aver c&e temporale juxtapos@e, r&ion glabellaire &prim6e et sinus rkduit ou absent.
tors with reduced or absent sinuses, themselves descendents of lineages endowed with such structures. In its volume, topography and position, the frontal sinus of the late Middle Miocene Otavi spe’cimen accords closely to the condition found in older African apes such as Proconsul from Rusinga and Proconsul major from Napak. It is also similar to the morphology in extant African apes and humans, even though it has’ no sign of a supraorbital torus. Otavipithecus differs markedly from all Eurasian apes in which the frontal anatomy is inown. Even though it does not possess any of the apomorphies found in AAH, Otavipithecus possesses morphological characters that do not exclude it from a role in AAH ancestry (figure 3) and it is suitably placed in time to have been such an ancestor. We consider that the major differences in frontal sinus development in hominoids are related to the way in which the splanchnocranium Extant African apes extant Asian apes
and are
is hafted onto the neurocranium. humans are klinorynchous while airorynchous. By this criterion,
Eurasian Miocene hominoids are all airorynchous to some degree (table) (Brown and Ward, 1988), but not to the exaggerated extent observed in Pongo and Sivapithecus. Miocene African hominoids such as Proconsul and Otavipithecus are mildly klinorynchous, as is the case in many other primates and mammals, whereas extant AAH are
more
strongly
klinorynchous.
Relationships between the temporal and the superciliary eminence in hominoids
crest
The external topography of the postorbital area varies greatly in hominoids depending on the degree of klinorynchyor airorynchy expressed. In markedly #airorynchous & Planefcvy
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M. Plckford
Table.
et al
Summary
of frontal
Anatomie
frontale
Primitive
hominoid
chez
anatomy
in large-bodied
/es Hominoib’es
de grande
faaille.
condition
Pongo
A) Superciliary arch thin B) Inflated glabellar surroundings C) Sinus invades frontal squama and superciliary arch Slight
hominoids.
A)
Reduced to strong
Proconsul Afropithecus Otavipithecus
klinorynchy (2) airorynchy
crests C)
A) Bar-like supraorbital torus B) Projecting glabellar surroundings Retention of primitive hominoid condition offrontal sinuses.
(1)
Strong
1) Dryopithecus Ankarapithecus Ouranopithecus 2) Pongo Sivapithecus 1 ufengpithecus
as
Sivapithecus
the
temporal
such
portion
and
African apes (not humans)
Supraorbital costae with juxtaposed temporal B) Depressed glabellar surroundings C) Reduction (1) to suppression (2) offrontal sinus
klinorynchy
taxa
clade
of
the
supraorbital
and
crest
sulcus
Pongo
is located
the
anterolateral
close
to the
is groove-like.
Pan Gorilla
lineages morphology
orbit
In slightly
klinorynchy
airo-
of
humans. However, of its supraorbital
there region
is nothing to exclude
in the it from
including genera such as Dryopithecus, Ouranopithecus and Ankarapithecus, the temporal crest is placed slightly further back from the orbital margin but is still separated from the superciliary eminence by a groove rather than a sulcus. In klinorynchous taxa, in contrast, the
being ancestral to this clade. The lack of a supraorbital torus in Otavipithecus may resolve a long-standing debate concerning its absence in Proconsul nyanzae. Pilbeam (1969) considered that the lack of a supraorbital torus in Proconsul ah-icanus (as the 1948 Rusinga skull was known at the time) was due to the
antero-lateral portion of the temporal crest is located relatively far behind the superciliary eminence and is separated from it by a wide sulcus rather than a groove. The frontals of Proconsul and Otavipithecus accord with
small size and gracility of this species relative to extant African apes. In other words, he considered the development of a torus in Pan and Pongo to be an allometric feature, related to the larger size of the extant apes,
the
whereas Leakey considered sul to be due to its primitive
rynchous
genera,
mildly
klinorynchous
condition.
In strongly
klinoryn-
chous lineages such as Pan and Gorilla, the temporal crests are even further separated from the superciliary eminence, leaving room for the development of supraorbital tori.
Supraorbital
tori and supraorbital
There
has
some
when
applied
been
Dryopithecus which
ends
confusion
over
the
“torus”
to the supraorbital anatomy of hominoids. possesses a slightly thickened orbital rim, medially at the superciliary notch. In Pongo
and Sivapithecur the thickening of the orbital margin extends medially and even inferiorly into the interorbital area. This morphology is fundamentally different from that
torus
that
morphology
464
is so characteristic
is unlike
costae
rather
tori
is not due structure.
African
apes
trace
inflated
supraorbital
African
apes
tori
found C
and
in
its
Sci
an apomorphy
of a extant
of the group.
of supraorbital
of the
orbits,
extending
sagitally, covering the supraorbital well below the frontozygomatic some variation in the disposition
some
R. Acad
represents
development torus of
tori
KBhler (1993) noted that the s#urface of the costae and interorbital pillar in Dryopithecus laietanus was roughened in much the same way as the surface of the costae and pillar in Pongo. In Pongo the roughening consists of vermiform canals and pits in the surface of the bone oriented more or less parallel to the
in the
of the
to allometry, but to the As such, the suprorbital
Moy2 and supraorbital
margins
no
of extant
the
than
apes new
Surficial morphology and costae
observed in AAH in which a continuous bar with or without a glabellar depression traverses the supraorbital region from side to side. The use of the word “torus” in connection with these two fundamentally different structures is confusing. Clarke (1977) was of a similar opinion and proposed the words “supraorbital costae” for the morphology in Pongo. All known Eurasian apes, both fossil and extant, possess supraorbital region. The Otavi frontal shows
of a toirus in Procon(see Shea, 1988 for
details of this debate). Otavipithecus is about the size of a small chimpanzee, yet it clearly has no sign of a supraorbital torus. The new Napak orbit, which probably belongs to Proconsul major, also reveals that there was no supraorbital torus in this Lower Miocene species th’at was appreciably larger than a chimpanzee. Thus, the available evidence suggests that the presence of tori in extant African
costae term
the lack condition
Paris.
Sciences
de
la terre
et des
plan&es
from
the
interorbital
pillar
costae and extending suture laterally. There is and strength of this / Earth
& Planetary Sciences 19’37. 325.459-466
Miocene rugose
surface,
its development
probably
being
related
to
the size and development of the facial mask. In African apes in contrast, the roughened bone of the supraorbital tori, when present, does not extend downwards the interorbital pillar, nor does it descend below tozygomatic suture.
ecus is taken Pongo clade.
to
be a derived
Temporo-glabellar The the
character
linking
to of of
it to the
temporo-glabellar These bony
ridges in ridges are
unusual in primates and were taken to be an autapomorphy of Afropithecus by Leakey et al. (1988a). Their presence in the Otavi specimen suggests a possible phylogenetic relationship between the two genera. Such a relationship has already been proposed by Andrews (1992) on the basis of mandibular and dental evidence, but Pickford et al. (1994) argued that this was unlikely. The interesting point is that in the Otavi frontal these ridges have been reduced in relief partly because of inflation of the superior surface of the frontal above the enlarged sinuses. Further inflation of this region could well lead to reduction in relief of these ridges or to their disappearance and to suppression of the post-glabellar frontal sulcus that lies between them, in which case the frontal would more closely resemble that of other hominoids in which these ridges
do
Systematics arises as to whether Otavipithecus should be a synonym of Afropithecus, but the frontal and
the holotype mandible of Otavipithecus are morphologically markedly different in several important respects from their counterparts in Afropithecus. Pickford et al. (1994) enumerated the differences between the mandibles and dentition of Otavipithecus and Afropithecus, and the Otavi frontal serves to amplify the distinctiveness of these two genera and indicates that synonymy would be inappropriate. The postorbital while it is much
constriction in Afropithecus less so in the Otavi specimen.
is marked, In the Otavi
frontal the sinuses have been greatly enlarged in comparison with those of Afropithecus and the temporal crests have not only shifted distally with respect to the superciliary crests but they have also moved considerably further apart. Thus, the frontal trigon in Afropithecus is considerably
smaller
C. R. Acad 1997
in
area
than
Sci. Paris, Sciences
325.459-466
is a smaller
species.
from
Thus,
Namibia
whereas
in
temporal crests far apart even at their most distal preserved extremity. In the Otavi specimen, the postglabellar frontal sulcus is positioned appreciably further distally than it is in Afropithecus. It is doubtful that the differences observed relate to sexual dimorphism. Finally, the angle between the frontal squama and the interorbital pillar in Afropithecus is very open, as in Aegyptopithecus, whereas in Otavipithecus this angle is more closed, being similar to those of vertically
pongids oriented
and African face.
apes,
suggesting
a more
Otavipithecus is plesiomorphic in its known cranial parts, being not greatly different from other Lower and Middle Miocene African hominoids. Compared with Proconsul, in some of its dental features it is derived towards the African Ape/Human clade, which is why Conroy et al. (1992) placed it close to the genus Kenyapithecus, but its frontal shows none of the derived features of extant African apes such as the development of a bar-like supraorbital torus (figure 3; table). In the past, various Eurasian Miocene hominoids have been proposed as hominid ancestors (i.e. #ancestral either to African apes and humans, or ancestral exclusively to Australopithecus) (Wu et al., 1986; de Bonis et al., 1990; Dean and Delson, 1992; Begun, 1995), or that they may be the stem members of the great apes and human clade (Alpagut et al., 1996) rather than having exclusive relationships with either the African apes or the pongines. We consider that these hypotheses are unlikely because all of the Eurasian pretenders to AAH ancestry have small or absent sinuses in the frontal squama ancl possess other characters of the splanchnocranium and dentition that ally
not occur.
The question considered
latter
boqe
Phylogeny
ridges
presence of oblique bony Otavi frontal is interesting.
the
frontal
Afropithecus the temporal crests meet relatively close behind glabella to form a frontal trigon behind which is a prominent sag&al crest, the Otavi specimen shows the
towards the fron-
Examination of fossil hominoids from Africa, including Proconsul and Otavipithecus, reveals that the roughened bone surfaces in the supraorbital region are confined the superciliary region, and are not as extensive as those Pongo. Thus, the extent of this vermiform morphology the bone surface in the supraorbital region in Dryopith-
though
hominoid
it is in
de la terre
Otavipithecus,
et des plan&es
even
them to the Pongo clade. Australopithec-ines Homo, in contrast, possess enlarged frontal invade the frontal squama and the supraorbital and are thus primitive in this set of features. The above can be summarised as follows 1) Otavipithecus clade and greatly Miocene hominoids
and early sinuses that eminence (figure
3):
points to an African origin of the AAH weakens hypotheses in WI- ich Eurasian are viewed as ancestral to the AAH
clade; 2) the Otavipithecus frontal with its extensive sinuses suggests that the reduced sinuses of Dr:vopithecus and Ouranopithecus represent a morphology derived towards the condition found in the Pongo clade in which frontal sinuses are reduced or even absent; 3) european Late Miocene apes are phylogenetically closer to the Asian Pongidae (Sivapithecus, Lufengpithecus, Pongo) than to the AAH clade, but appear to form a clade of their own (containing Dryopithecus,, Ankarapithecus and Ouranopithecus) within the family Pongidae.
/ Earfh & Planetary
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et al.
Acknowledgements: The authors would like to thank the Geological Survey of Namibia (Dr B. Hoal, Dr G. Schneider) for logistic and administrative support that led to the recovery of the Otavi frontal. Research permission was accorded by the National Monuments Council of Namibia (Mr G. Hoveka. Mr A. Vogt). Thanks are also due to the College de France (Prof. Y Coppens), the Museum National d’Histoire Naturelle (Prof. Ph. Taquet) and the Mission of Co-operation and Cultural Affairs, Windhoek (M. Yves Make. Mme N, Weir). Goldfields Namibia and the Development Brigade Corporation of Namibia provided access to Berg Aukas Mine, Namibia. Thanks are ulso extended to the National Museum of Uganda (Mr E. Kamuhangire. Mr E. Musiime) for access to the Napak hominoid samples, Angel lsobel kindly made casts of the Otovi specimen. Last, but by no means least, we thank Dr B. Senut, co-leader of the Namibia Palaeontology Expedition for her continued involvement in this project.
REFERENCES
Aiello L. and Dean C. 1990. An introduction to Human Evolutionary Anatomy, Academic, London, 596 p. Alpagut B., Andrews P., Fortelius M.. Kappelman J., Temizsoy IL, Celebi H., and Lindsay W. 1996. A new specimen of Ankurapithecus meteai from the Sinap formation of Central Anatolia, Nature, 382,349.351 Andrews P. 1992. Evolution and environment in the Homtnoideo, Nature. 360,641.646 Begun D 1995. Miocene fossil hominids and the chimp-human clade. Science, 257. 1929-1932 Begun D. 1995. Late Miocene European orong-utans, gorillas, humans, or none of the above? J. Hum. Evoi, 29,169- 180 Brown B. and Ward S 1988. Basicranial and facial topography in Pongo and Sivapifnecus, In: Schwartz J.H. (ed). Orang-ufun Eiology, Oxford University Press, New York & Oxford, 247-260 Cave A.J.E. and Haines. R W. 1940. The poranasal sinuses of the anthropoid apes, J. Anot., 72,493-523 Clarke R.J. 1977 The cranium of the Swarfkrans hominid SK 847 ond its relevance to human origins, PhD Thesis, University of the Wrtwatersrand, Johannesburg, South Africa Conroy G., Pickford M., Senut B.. Van Couvering J.A. and Mein P. 1992. Otavipithecus namibiensis. first Miocene hominoid from southern Africa, Nature, 356, 144-148 Conroy G., Pickford M., Senut B. and Mein P. 1993. Additional Miocene primates from the Otavi Mountains, Namibia. C. R. Acad. Sci. Paris, 317. s&e II, 987-990 Dean D. and Delson E. 1992 Second gorilla or third chimp? Nature, 359‘676.677 De Bonis L., Bouvroin G., Geraads D. and Koufos G. 1990. New hominid skull material from the late Miocene of Macedonia in northern Greece, Nuture. 345,712.714 De Bonis L. and Koufos G. 1993. The face and mandible of Ouronopifhecus macedoniensis: description of new specimens and comparisons, J. Hum. Evol., 24,469-491 Kordos L 1991. Le Rudapithecus hungaricus de Rudabbnya (Hongrie), L’Anthropo/ogie, 95,343.362 Le Gros Clark W.E. and Leakey L.S.B. 1951 The Miocene Hominoidea of East Africa, Fossil Mamma/s of Africa, 1, l-1 17 Leakey R., Leokey M G. and Walker A.C 19880. Morphology of Afropifhecus turkanensis from Kenya, Am. J. Phys. Anthropoi.. 76, 289-307 Leakey R., Leakey M.G. and Walker A.C 1988b. Morphology of Turkonapithecus kolokolensis from Kenya, Am. J. Phys. Anfhropal., 76,277.288
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Moyc?~ S. and Kohler M. 1993. Dryopithecus y el origen de 10s grandes monos actuales, lnvestigocion y Ciencbo, 207. 30-31 MO@ Sold S. and Kbhler M. 1993. Recent discoveries of Dryopithecus shed new light on evolution of great apes, Nature, 365, 543-545 Mayo Sola S. and Kohler M 1995. New pariiol crs3nium of Dryopitbecus Lartet. 1863 (Hominoideo. Primates) frorn the upper Miocene of Can Lloboteres, Barcelona, SpaIn, J. Human Evoi.. 29. 101-139 Pickford M. 1985. L’ecologie des premiers grands singes, La Recherche, 16. 188-198 Pickford M 1986. The geochronoiogy of Miocene higher primate faunas of East Africa, In: Else J. and Lee P. (eds:‘, Primate fvolufion, Cambridge University Press, 19-34 Pickford M.. Senut B , Conroy G. and Mein P. 1986. Phylogenetic position of Ofavipifhecus: Questions of methodology and approach, In Thierry B.. Anderson J R.. Roeder J.J. and HerrenSchmidt N., (eds), Currenf Primatology, 1, Ecology and Evolution. Universite Louis Pasteur, Strosbourg, 265272 Pilbeam D and Smith R. 1981. New skull remains of Sivopifhecus from Pakistan, Mem. Geol. Surv. Pakistan, 2. 1-13 Pilbeam D. 1969. Teliiary Pongidae of East Africa Evolutionary relationships and Taxonomy, Peabody Museum of Natural History, Buiiefin, 3 1, 1~ 185 Preuss TM. 1982. The face of Sivopithecus indicus, Description of a new, relatively complete specimen from the Siwaliks of Pakistan, folio Primatologico, 38. 141-l 57 Senut 8.. Pickford M , Mein P.. Conroy G. and Van Couvering J.A. 1992. Discovery of 12 new Neogene fossiliferous sites in palaeokarsts of the Otavi Mountains, Namibra, C. R. Acad. Sci. Paris, serie II, 3 14, 727-733 Shea B. 1988 Phylogeny and skull form in the holninoid primates In, Schwartz J.H. (ed), Orang-ufan Biology. Oxford University Press, New York & Oxford. 233-245 Walker AC, Falk D.. Smith R. and Pickford. M. 1983. The skull of Proconsul africanus: Reconstruction and cranlal capacity, Nature, 305,525.527 Winkler L , Conroy G. and Vannier M. 1988. Sexual dimorphism in exocranial and endocranral dimensions, In: Schlwartz J.H. (ed). Orang-utan Biology, Oxford University Press, New York & Oxford. 225-232 Wu Rukang, 1984 The cranium of Romapithecus and Sivapithecus from Lufeng. China, Cour. Forsch. Inst. Senckenberg, 69. 41-48 Wu Rukang, Xu Qinghuo and LL. Qingwu. 19136. Relationship between Lufeng Sivapithecus and Ramapithecus and their phylogenetic position, Acta Anfhropol. Sin/co, 5, l-3:;
Sci. Paris, Sciences
de ICI terre
et des planetes
J Earth
& Planetary Sciences 1997. 325,459.466
Paw humaine)
Phylogenetic implications Middle Miocene hominoid from Otavi, Namibia
of the first African frontal bone
Implications phylog&n&iques du premier OS frontal d’un Hominoi’dea du Mioc&ne moyen d’otavi, Namibie Martin
PICKFORD’
! Salvador
MOYA
’ Chaire depal~oal?thro~ologte et depr&stoire,
SOLAR
and Meike
K~HLER’
CollGgedo France and .Vfuseumnuttonul d’histoire naturelle.
IFA
12 du C!V?S, 8. mt? Buffin,
75005 Paris, France
’ Institllt de I’uleorztologxa .M. Cr~.sujiint. E.scolaIndz~stnal23, 08201 Subau’ell, Burcelonu. Spain
ABSTRACT The discovery of a hominoid frontal at Berg Aukds, Namibia, aged 13-12 Ma, permits an analysis of the phylogenetic relations between fossil and extant great apes. The Namibian specimen is closer morphologically to African apes and humans (MH), whereas all fossil Eurasian great apes differ markedly from MH but are closer to the F’ongo clade. Keywords:
Hominoidea,
Fronfd
bone,
Middle
Miocene,
Namibia.
Phylogeny
La dkcowetie d’unfrontal d’fIominoidea d Berg Aukas. Namibie, a& de 13-12 :zla, permet I’analyse des relations phylo@nBtiques parmi les grands singes jossiles et vivants. L ‘&chantillon de Namihie s’a&re movphologiquement pro&e des singes af?icain.s et des hommes (AAH), tandis que tous les singesfossiles eurasiatiques s’t?loi’went de.sAAH et s’approchent du clade de Pongo. Mob
cl&s : Hominoidea,
OS frontal,
Miocene
moyen,
Namibie,
Phylogbnie
VERSIONABR~~G~E Introduction
et 8ge
Un frontal d’Hominoidea, Bh 52’94, a Cte decouvert dans un bloc de b&he r&zolte en 1994 5 Berg Aukas (Namibie). une localite des paleokarsts de la region des monts Otavi. La pr¶tion i l’acide a livre de tr& abondants microfossiles, dont l’association sugg?re un Ige de la fin du Miocene moyen (12-13 Ma). proche de celui des gisements de Fort Ternan et Ngorora au Kenya (Pickford, 1986).Des hr?ches identiques avaient deja livre des restes d’Hominoidea attribues 2 Otavzpi&ecus namibiensb (Conroy et al, 1992, 1993 : Senut et al., 1992). Otampithecus appartient ?I une periode int&essante. appelke I le trou noir des Homino’ides d‘Afrique j’ et qui a livrC trPs peu d’Homino’ides (Pickford, 1985). I1 est post&ieur aux xore prbxk Note remix
autres Hominoi’des de grande taille du MiocGne infkrieur d‘Afrique orientale, chez lesquels le frontal est connu, in&ant Proconwl (Walker et al., 19X3), Ajiropithews (Leakey et al.. 1988a) et Turkanapithecus (Leakey et al., 1988b). I1 prec?de les Hominoi’des eurasiatiques chez lesquels l’anatomie frontale est connue : Dvopithecus (Maya Sola et Kohler, 1993, 1995 ; Kordos, 1991), Ouranopithecus (de Bonis et Koufos. 1993 ; de Bonis et al., 1990), Ankarapithecus (Alpagut et al., 19961, SiLaapithecus (Preuss, 1982) et Lz~engpithecus (WI, 1984).
Anatomie Le fossile reprksente la plus grdnde partie dL. frontal, dont les bords sent absents. Le su1cu.s sztpraorbitalis n’est pas conserve. Lateralement, entre la crtte supercilidire et la c&e temporale,
par Yves Coppens le 26 dkembre
1996, accept&
C. R. Acad. Sci. Paris, Sciences 1997, 325,459.466
aprPs r&ns~on
de la terre
le 5 filvrier
et des planktes
1997
/ ECU% & Planefury
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M. Pickford
et al.
on observe une depression peu profonde, mais large. La crt?tr: supraciliaire du specimen d’Otavi est &troite : il n’y a pas de sulcus supraoral. LaGralement, on observe un sulcus peu profond entre la c&e supraciliaire et la crete tempordle. La mesure de l’image-miroir du frontal donne 24 mm environ pour la largeur interorbitaire entre les coins mksio-distaux des orbites. Les c&es temporales du frontal d’Otavi som ac@es et surplombent les fesses temporales. I1 y a deux sinus proeminents. mais inegaux. dans la region supraorbitale de BA 52’94 (figures 1 et 2). Une partie des sinus frontaux isole le plan orbitaire de la surface supkrieure du frontal, comme chez les grands singes africains et l‘homme actueki, mais i la difference de la situation obsen+e chew Dr-ypithecus, chez qui les sinus frontaux sont restreints ?i la proximite du nasion (figure 2). Che7 les grands singes africains actuels et les hominid& (AAH), le sinus frontal remplit tout l’espace sit& sous et derriere la glabelle j il atteint lateralement les parties moyennes des dew rebords supraorbitaux, s’etend posterieurement dans l’tcaille frontale et inferieurement dans la zone interorbitaire, et de 18 post&o-inferieurement, pour rencontrer le sinus ethmoi’dal. Les rkgions conservees du frontal d’Otavi s’accordent tout g fait avec cette description. Parmi les grands singes Homino’ides du Miocene infkrieur d’hfrique, de tcls sinus frontaux ont etil signal& chez l+oconszll n~wwae (crsne de Rusinga trouve en 1948) (Le Gros Clark et Leakey, 1951 ; Walker et al., 1983), Turkanupithecus (Leakey et al., 1988 b) et Afiopitk~ecus (Leakey et al., 1988 a). Un fragment non d&rit d’une orbite gauche provenant de Napak en Ouganda (Napak V, 1964) attribuable 2 un Homino’ide de grande taille (probablement Procon.%.d vrzzjoc connu sur plusieurs sites g Napak, et incluant Nap V) consiste en une portion sup&o-IatCrale de l’orbite. Shea (1988) a estime que ‘cle d&eloppement d’un vrai sinus ethmofrontal ktait un caractsre derive reliant les grands singes africains et l’homme ‘pet qu’il etait associe 2 une klinorynchic. Comme Brown et Ward (1988). nous consid&ons que la condition dilrivee est representee par les grands singes eurasiatiques; chez qui le sinus frontal est reduit ou absent, une morphologie associee 5 l’airorynchie. Begun (1985) a affirm6 que Dryopitbecus possedait de grands sinus frontaux. mais nos observations suggilrent qu’en fait, il n’en est rien : les sinus frontaux de Dvopithecus sont petits et limit& 2 la region du nasion. La presence de sinus frontaux supraorbitaires chez SizJupirbecus (Pilbeam et Smith, 1981) n’a pas kte confirmi-e par les travaux plus recents de Preuss (1982). De Bonis et al. (1990) ont postule qu’ Ouranopitheus est ancestral par rapport i Austrdopithecus. Si cela iltait le cas, il
Introduction
and age
An adult hominoid frontal bone, BA 52’94, was found in a breccia block collected in 1994 at Berg Aukas, Namibia, a palaeokarst locality in the Otavi Mountains. Acid digestion of the block released an extensive crop of microfossils and several isolated teeth of Otavipithecus. The microfauna from BA 52’94 is the same as that from the breccia, which yielded the holotype of Otavipithecus namibiensis,
460
C. R. Acad.
SCI. Paris,
devrait posseder de grands sinus frontaux du type AAH ; or. cela ne semble pas &tre le cas. Au contraire. la marphologie frontale dans la region supraorbitaire est comparable 5 celle obsen& chez D yopithecus et m@me Sivapithecus, indiquant son appartendnce au &de de Pongo. Chez Po?zgo, il n’y a pas de sinus frontaux (Winkler et al., 1988). tandis que chez Dyopithecus. le sinus est confine $ la region paranasale et ne p&Gtre pas vers le haut, dans l’ecaille du frOntal. ou lateralement, ddns les c&es supraorbitaires (Maya Sola et Kohler, 1995) (figure 2). La meme absence de sinus frontaux a et6 signal& chez Sioapithec#s (Preuss, 1982) et Lufengpithecus (Wu, 1984). La decouverte recente d’un crine d’hkarapithecus (Alpagut et al., 1996) suggererait que ce dernier possi-de un sinus frontal etendu. Pour qu’AnkavapitbeGUSsoit considkri- comme un Hominoi’de primitif, ainsi que le suggt:rent Alpagut et al. (1996), il faudrait que les sinus frontaux envahissent l‘ecaille du frontal et les &es supraorbitaires. L’anatomie du frontal afflaiblit considerablement toutes les hypotheses qui reconnaissent les grands singes du Miocene terminal d’J?urasie comme des ancetres du clade AAH (Begun, 1995). Bien qu‘il ne possPde pas toutes les apomorphies des AAH, Otaugitbecus presente des caracrPres morphologiques qui ne l’excluent pas de cette ancestralit&
Phylogbnie Dans le passe, de nombreux Hominoi’des mioc?nes ont joue tour 2 tour le r81e d’ancetres des Hominides (‘3e Bonis et al., 1990, Begun, 1995 ; Dean et Delson. 1992 ; Wu et al., 1986 ; Alpagut et al., 1996). Xous considerons ces hypotheses comme invalidees, car lous les pretendants eurasiatiques 2 l’ancestralit6 des AAH ont des sinus de petite taille ou absents dans I’&zaille du frontal. En conclusion, nous pouvons dire que Otaz,ipitbecus souligne une origine africaine du clade AAH et affaiblit considerablement 1’hypothPse d’une origine eurasiatique ; que le frontal d’Otar?zpitbecus, aux sinus tr&s d&eloppes, :#ugg&e que la r&iuction de sinus chez D yopithecus et Guranopithecus, represente une morphologie d&i&e vers les conditions trou&es dans le &de de Pofzgo; enfin, les grands singes du MiocGne terminal d’Eurasie sont phylog+netiquement plus proches des Pongidae asiatiques (Sivapitbecus, Lufengpitbecus et Po?zgoj que du clade des AAH. Ils semblent, en owe, former leur propre ckdde (contenant Dyopithecus, An,karapithecus et Ouranopithecus) au sein de la famille des Pon,qidae.
and it indicates that the sediments accumulated during the latter part of the Middle Miocene (12-13 Ma) approximately at the same time as the sites of Fort Ternan and Ngorora, Kenya (Pickford, 1986). Similar breccias from the site have previously yielded remains of hominoids classed as Otavipithecus namibiensis (Conroy et al., 1992, 1993; Senut et al., 1992). Otavipithecus occupies an interesting period of time, the so-called “hominoid black hole” of Africa, from which very few homino’id fossils have Sciences
de
la terre
et des
plan&es
/ Earth
& Planefory
Sciences
1997. 325,459-466
Miocene been
recovered
bodied including (Leakey 1988b) Eurasian known:
(Pickford,
1985).
It post-dates
other
1991) Ouranopithecus Sol& and Kbhler, 1993, al., 1996), Sivapithecus ecus (Wu, 1984).
Anatomy
(de Bonis and Koufos, 1995), Ankarapithecus (Preuss, 1982), and
1993; Moy& (Alpagut et Lufengpitb-
of BA 52’94 most and
of its tem-
crests are preserved. The endocranial surface is in a condition and is broken anteriorly to reveal an extenfrontal sinus. The outer table is in excellent condition. the Otavi frontal there is no supraorbital torus. Laterbetween the superciliary ridge and the temporal crest
there is a shallow but wide depression, which corresponds in position to the lateral part of the post-toral sulcus in Pan. In Dryopithecus ciliary ridge,
which
from the rest of the frontal, shallow superciliary groove
(Moyg SolA and K8hler, 1995) the superhas a roughened surface, is separated
which that
frontal
bone
is smooth, runs parallel
from
Namibia
by a long but to the super-
ciliary margin but some 10 mm behind it before culminating medially near the superciliary notch. This groove separates the superciliary eminence frorn the temporal crest. A similar morphology occurs in S/vapithecus and Pongo with the exception that the superc:iliary groove is narrower and deeper and the medial end of the roughened superciliary crest extends further medially and then descends inferiorly as far as nasion. The Otavi frontal, with its smooth superciliary crest and wide postorbital sulcus is close in morphology to Proconsul africanus and extant African apes and humans (AAH), despiie its lack of a bar-like
The fossil is a large part of a frontal bone lacking margins (figure 1). However, parts of the orbits poral poor sive In ally
large-
hominoids in which the frontal bone is known, Proconsul (Walker et al., 1983), Afropitbecus et al., 1988a) and Turkanapithecus (Leakey et al., from East African lower Miocene sites but predates hominoids for which the frontal anatomy is Dryopithecus (de Bonis et al., 1990; Kordos,
hominoid
supraorbital
torus.
On the right side of the fossil the supraorbital notch interrupts the superciliary ridge mesially, but it is not very marked. In Dryopithecus the superciliary notch coincides in position with the mesial end of the superciliary groove, and in this respect the frontals of Otavi and Dryopithecus are quite different. The superciliary ridge of the Otavi specimen is narrow, as in many Miocene hominoids. Its superior surface is marked on the right side by a sharply defined, but narrow, groove that enters a nutritive foramen medially. There is no supratoral sulcus in the zone distal from and between the supraorbital notches. The upper surface of the Otavi frontal is even slightly elevated in the region where a depression usually exists in extant African apes and in extinct forms such as Dryopithecus (Moyil Sola and Kiihler, 1995). In this Rusinga Proconsul low sulcus between
respect it is comparable nyanzae skull. Laterally the superciliary ridge
to the 1948 there is a shaland the tempo-
ral crest. Medially this slight depression is b’ordered by low ridge of bone, which crosses the frontal obliquely from the temporal crest towards glabella, as described Afropithecus (Leakey et al., 1988a). A similar low ridge bone occupies an analogous position in the frontal Dryopithecus. The post-glabellar frontal far back in comparison with Afropithecus, of the area delimited by the oblique
a in of of
sulcus is located the anterior part hotly temporo-
glabellar ridges having been raised upwards in responseto the development of extensive frontal sinuses. The postglabellar frontal sulcus is bordered laterally by raised flanges, which delimit the distal portion of the temporal crest. At glabella there is weakly developed but palpable mid-line depression, which appears with be homologous with the depression that occurs in the dorsal surface of the supraorbital torus in fan, Gorilla and humans as well as in some fossil forms including Dryopithecus (Maya Sola and Kbhler, 0
1
2
Figure 1. Superior (A) and anterior (B) views of the Otavi frontal temporal ridges; 2: extent of the sinuses). Note the wide interorbital pillar and the thin superciliary arches (scale in cm). : Vues supkieure (A) et antkieure (B) du frontal temporales; 2: extension des sinus). Noter le large et /es fines arches supraciliaires I&he//e en cm).
C. R. Acad. Sci Paris. Sciences 1997. 325,459-466
de la terre
d’Otavi (I: c&es pilier interorbitaire
et des planetes
(1:
1995).
It is difficult to measure the width of the interorbital region directly, because on the left side o111y a very small part of the orbital margin is preserved. However, measurement of mirror image reconstructions of the frontal yield a figure of ca. 24 mm for the interorbital the mesial-dorsal corners of the orbits. size of the frontal this measure is large, orbits were wide apart.
/ Earth & Plunetary
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breadth between Considering the meaning that the
461
M. Pickford
et al.
The temporal crests of the Otavi frontal are sharp ure 1) and overhang the temporal fossa, being not different in this respect from Proconsul. They overhang
(figvery the
fossa more than those of Afropithecus and Dryopithecus and are not like those found in more encephalised modern African apes where there is no overhang. The temporal crests are wide apart immediately behind the orbits and converge distally, but do not meet in the midline in the preserved parts of the specimen. from glabella, the two temporal apart.
Forty millimetres crests are still
distal 30 mm
On the right side of the frontal, parts of the superior and mesial margins of the orbit are preserved. The angle between these parts is relatively abrupt giving the impression that the orbit is of the D outline type rather than the oval
Figure 2. Extent and Otavipithecus nasion).
type. But in such a fragmentary specimen one can not go further than this. The endocranial part of the frontal is poorly preserved although part of the groove for the superior sagittal sinus can be observed in the midline. A groove for a meningeal left half of the
vessel frontal
is prominent and several
Extension Otavipithecus nasionl.
in the better preserved arachnoid granulations
Among
developed (figures
si1 and
slightly to the right of the midline of the frontal. The lateral half of the right sinus is partly filled with cancellous bone (representing a pathological condition?), so that only the
nasion (figure 2), and thereby only separate the plate from the endocranial surface of the frontal paranasal region. In this respect the Otavi frontal different from that there are no frontal
of Pongo sinuses.
and
Sivapithecus
Miocene
hominoids
men. The interlinking and there suggesting
and in of
orbital in the is very
superciliary surface vermiform grooves are three post-mortem that the specimen
In extant sinus fills
African all the
in which
sinus in hominoids Apes space
and Hominids (AAH) the below and behind glabella
462
frontal and it
Sci.
undescribed fragment of (Napak V, 1964) assign(probably Proconsul masites at Napak, including
is patterned as in extant depressions was chewed
with shallow African apes, in the ridge, by carnivores.
in the frontal condition.
squama
in our opinion, a plesiomorphic one, already present Lower Miocene hominoids. Nevertheless, the extant can apes and humans appear to be more klinorynch their Lower Miocene predecessors, and in this sense, was partly right to think of the extant AAH as derived
superior to nasion we cannot to the ethmoidal sinus, but we was indeed present in Otavipi-
C. R. Acad.
similar
rep-
Shea (1988) has argued that “the development of a true ethmofrontal sinus appears to be a derived trait linking the African apes and humans” and that it is linked to klinorynchy. We, like Brown and Ward (1988), cannot agree with him entirely; on the contrary, we consider that the derived condition is represented by the Eurasian apes in which the frontal sinus is reduced or suppressed entirely, a morphology linked to airorynchy. The AAH condition is,
reaches laterally to the middle parts of both supraorbital rims, extends posteriorly into the frontal squama and inferiorly into the interorbital area and thence posteroinferiorly to connect with the ethmoidal sinus. Where preserved the Otavi frontal accords with this topography. As a result of breakage demonstrate connection infer that this connection thecus.
Africa,
et 3:
In the posterior view, the anterior surface of a large sinus is preserved, extending laterally to the edge of the specimen near the zygomatico-frontal suture. This sinus divides the frontal squama into two portions, a superior plate and an orbital plate, very much as in Pan and Gorilla. All this suggests that extensive sinuses resent the primitive hominoid
The frontal
from
(2 gauche) 2: &belle;
site Nap V) consists of the superior-lateral portion of the orbit. Posteriorly there is a smooth post-orbi-tal sulcus, and there was evidently a gap between the superciliary ridge and the temporal line in this specimen. The relationship between this surface and the superior part of the orbit reveals that there was no supraorbital torus in this speci-
medial part is open. The left sinus is appreciably larger than the right one and it crosses over to the right side where it lies above and slightly distal to the right sinus. Part of the frontal sinus separates the orbital plate from the African apes Dryopithecus to the vicinity
Lower
ithecus(Leakey et al., 1988a). An a left orbit from Napak (Uganda) able to a large-bodied hominoid jor, which is known from several
2). These ascend into the frontal from the vicinity of nasion (which is not preserved in this specimen). The two sinuses are separated from each other by a wall of bone positioned
superior surface of the frontal as in extant humans, and unlike the situation in which the frontal sinuses are restricted
sinus dam /es frontaux de Dryopithe’cus (;1 droitel (coupes sagittalesl (7: simls;
extensive frontal sinuses have been reported to occur in Proconsul africanus (as the 1948 Rusinga skull was known at the time) (Le Gros Clark & Leakey, 1951; Walker et al., 1983), Turkanapithecus (Leakey et al., 1988b) and Afrop-
are present. There are two prominent but unequally nuses in the supraorbital region of BA 52’94
des
of the sinuses in the frontals of Dryopifbecus (left) right (sagittal sections) (1: sinus; 2: glabella; 3:
Paris,
Sciences
de
la terre
et des
plan@tes
/ Earth
in Afrithan Shea with
& Planeby Sciences 1997. 325,459.466
Miocene
respect
to
their
disagree with plesiomorphic
Lower
Miocene
precursors.
Where
we
hominoid
African
Apes
frontal
Hominidae
bcne
from
Dryopitkcus
Namibia
Pongme
him is in his assertion that the Asian apes are with respect to Lower Miocene hominoids.
Begun (1995) on the basis of the Spanish and Hungarian dryopithecine fossils, has argued that Dryopithecus has large frontal sinuses, but our observations show that the frontal sinuses in this genus are small and restricted to the immediate vicinity of nasion, whereas in AAH, sinuses are extensive and invade the frontal lateral from the midline and extend deep into squama, thereby forming extensive supraorbital The
existence
of supraorbital
frontal
sinuses
the frontal bone well the frontal sinuses. in Sivapitb-
ecus (Pilbeam and Smith, 1981) has not been confirmed by a more recent study (Preuss, 1982), the supposed sinuses being due to postmortem loss of cancellous bone. De Bonis et al. (1990) have postulated that Ouranopitbecus is ancestral to australopithecines, in which case it would be expected to possess frontal sinuses of AAH type, but this appears not to be the case. Instead, the frontal morphology in the supraorbital region, where it can be observed in the fractured surface between the splanchnocranium and the neurocranium, is comparable to that of Dryopithecus and even Sivapitbecus, indicating its relationships to the fongo clade. Other features of the splanchnocranium of Ouranopithecus, such as the shape of the premaxilla, the heteromorphic upper incisors and others, accord with the frontal morphology, indicating its close
affinities
In Pongo
with there
the
Pongo
lineage.
is no frontal
sinus
(Winkler
et al., 1988),
while in Dryopithecus the sinus is confined to the paranasal region and does not penetrate upwards into the frontal squama or laterally into the supraorbital costae (Maya Sola and KGhler, 1995) (figure 2). Similar lack of frontal sinuses has been reported in Sivapithecus (Preuss, 1982) and Lufengpithecus (Wu, 1984). The recently discovered cranium of Ankarapithecus (Alpagut et al., 1996) is reported to possess an extensive frontal sinus, but the position and extent of the sinuses have not been described in detail. For Ankarapitbecus to be a stem hominoid as was postulated by Alapgut et al. (1996), the frontal sinuses would have to invade the frontal squama and the supraorbital costae. In other aspects of the splanchnocranium (premaxillary morphology, positions of infraorbital foramina, supraorbital morphology, dentition) Ankarapithecus is similar to Our;]nopithecus and Sivapithecus, longs to the Pongo clade. frontal anatomy has been
and we believe that it beAll Eurasian apes in which studied in detail, both extinct
and extant, possess reduced sinuses in the frontal squama (table) or have none at all. There can be little doubt that the reduction (1) or suppression (2) of frontal sinuses in the Eurasian lineages represent derived morphological conditions among hominoids. As such, frontal anatomy greatly weakens all hypotheses in which Eurasian Late Miocene apes have been proposed as candidates for the ancestry of the AAH clade (Begun, 1995). This is because the enlarged frontal sinus of extant AAH would have had to have evolved from ancesC. R. Acad. Sci. Parls, 1997. 325,459.466
Sciences
de
la terre
et des
plan&es
/ Earfh
Figure 3. Proposed hominoids discussed morphic condition superciliary arch); glabella; C: supraorbital depressed glabellar
phylogenetic relationships of large-bodied in the text based on frontal anatomy. A: plesio(extensive sinus, no supraorbital torus, thin B: bar-like supraorbital torus with projecting costae with juxtaposed temporal crest, area and reduced or absent siinus.
Relations
phylog&@tiques chez /es Hominoib’es de grande tail/e, discutkes 2 park des caractkes de I’anatomie fron tale. A : condition pkiomorphe (sinus &endu, pas de torus supraorbitaire, arcade supracilaire fine) ; B : lows supraorbitaire en forme de barre avec glabelle projet6e ; C : &es supraorbitaires aver c&e temporale juxtapos@e, r&ion glabellaire &prim6e et sinus rkduit ou absent.
tors with reduced or absent sinuses, themselves descendents of lineages endowed with such structures. In its volume, topography and position, the frontal sinus of the late Middle Miocene Otavi spe’cimen accords closely to the condition found in older African apes such as Proconsul from Rusinga and Proconsul major from Napak. It is also similar to the morphology in extant African apes and humans, even though it has’ no sign of a supraorbital torus. Otavipithecus differs markedly from all Eurasian apes in which the frontal anatomy is inown. Even though it does not possess any of the apomorphies found in AAH, Otavipithecus possesses morphological characters that do not exclude it from a role in AAH ancestry (figure 3) and it is suitably placed in time to have been such an ancestor. We consider that the major differences in frontal sinus development in hominoids are related to the way in which the splanchnocranium Extant African apes extant Asian apes
and are
is hafted onto the neurocranium. humans are klinorynchous while airorynchous. By this criterion,
Eurasian Miocene hominoids are all airorynchous to some degree (table) (Brown and Ward, 1988), but not to the exaggerated extent observed in Pongo and Sivapithecus. Miocene African hominoids such as Proconsul and Otavipithecus are mildly klinorynchous, as is the case in many other primates and mammals, whereas extant AAH are
more
strongly
klinorynchous.
Relationships between the temporal and the superciliary eminence in hominoids
crest
The external topography of the postorbital area varies greatly in hominoids depending on the degree of klinorynchyor airorynchy expressed. In markedly #airorynchous & Planefcvy
Sciences
463
M. Plckford
Table.
et al
Summary
of frontal
Anatomie
frontale
Primitive
hominoid
chez
anatomy
in large-bodied
/es Hominoib’es
de grande
faaille.
condition
Pongo
A) Superciliary arch thin B) Inflated glabellar surroundings C) Sinus invades frontal squama and superciliary arch Slight
hominoids.
A)
Reduced to strong
Proconsul Afropithecus Otavipithecus
klinorynchy (2) airorynchy
crests C)
A) Bar-like supraorbital torus B) Projecting glabellar surroundings Retention of primitive hominoid condition offrontal sinuses.
(1)
Strong
1) Dryopithecus Ankarapithecus Ouranopithecus 2) Pongo Sivapithecus 1 ufengpithecus
as
Sivapithecus
the
temporal
such
portion
and
African apes (not humans)
Supraorbital costae with juxtaposed temporal B) Depressed glabellar surroundings C) Reduction (1) to suppression (2) offrontal sinus
klinorynchy
taxa
clade
of
the
supraorbital
and
crest
sulcus
Pongo
is located
the
anterolateral
close
to the
is groove-like.
Pan Gorilla
lineages morphology
orbit
In slightly
klinorynchy
airo-
of
humans. However, of its supraorbital
there region
is nothing to exclude
in the it from
including genera such as Dryopithecus, Ouranopithecus and Ankarapithecus, the temporal crest is placed slightly further back from the orbital margin but is still separated from the superciliary eminence by a groove rather than a sulcus. In klinorynchous taxa, in contrast, the
being ancestral to this clade. The lack of a supraorbital torus in Otavipithecus may resolve a long-standing debate concerning its absence in Proconsul nyanzae. Pilbeam (1969) considered that the lack of a supraorbital torus in Proconsul ah-icanus (as the 1948 Rusinga skull was known at the time) was due to the
antero-lateral portion of the temporal crest is located relatively far behind the superciliary eminence and is separated from it by a wide sulcus rather than a groove. The frontals of Proconsul and Otavipithecus accord with
small size and gracility of this species relative to extant African apes. In other words, he considered the development of a torus in Pan and Pongo to be an allometric feature, related to the larger size of the extant apes,
the
whereas Leakey considered sul to be due to its primitive
rynchous
genera,
mildly
klinorynchous
condition.
In strongly
klinoryn-
chous lineages such as Pan and Gorilla, the temporal crests are even further separated from the superciliary eminence, leaving room for the development of supraorbital tori.
Supraorbital
tori and supraorbital
There
has
some
when
applied
been
Dryopithecus which
ends
confusion
over
the
“torus”
to the supraorbital anatomy of hominoids. possesses a slightly thickened orbital rim, medially at the superciliary notch. In Pongo
and Sivapithecur the thickening of the orbital margin extends medially and even inferiorly into the interorbital area. This morphology is fundamentally different from that
torus
that
morphology
464
is so characteristic
is unlike
costae
rather
tori
is not due structure.
African
apes
trace
inflated
supraorbital
African
apes
tori
found C
and
in
its
Sci
an apomorphy
of a extant
of the group.
of supraorbital
of the
orbits,
extending
sagitally, covering the supraorbital well below the frontozygomatic some variation in the disposition
some
R. Acad
represents
development torus of
tori
KBhler (1993) noted that the s#urface of the costae and interorbital pillar in Dryopithecus laietanus was roughened in much the same way as the surface of the costae and pillar in Pongo. In Pongo the roughening consists of vermiform canals and pits in the surface of the bone oriented more or less parallel to the
in the
of the
to allometry, but to the As such, the suprorbital
Moy2 and supraorbital
margins
no
of extant
the
than
apes new
Surficial morphology and costae
observed in AAH in which a continuous bar with or without a glabellar depression traverses the supraorbital region from side to side. The use of the word “torus” in connection with these two fundamentally different structures is confusing. Clarke (1977) was of a similar opinion and proposed the words “supraorbital costae” for the morphology in Pongo. All known Eurasian apes, both fossil and extant, possess supraorbital region. The Otavi frontal shows
of a toirus in Procon(see Shea, 1988 for
details of this debate). Otavipithecus is about the size of a small chimpanzee, yet it clearly has no sign of a supraorbital torus. The new Napak orbit, which probably belongs to Proconsul major, also reveals that there was no supraorbital torus in this Lower Miocene species th’at was appreciably larger than a chimpanzee. Thus, the available evidence suggests that the presence of tori in extant African
costae term
the lack condition
Paris.
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la terre
et des
plan&es
from
the
interorbital
pillar
costae and extending suture laterally. There is and strength of this / Earth
& Planetary Sciences 19’37. 325.459-466
Miocene rugose
surface,
its development
probably
being
related
to
the size and development of the facial mask. In African apes in contrast, the roughened bone of the supraorbital tori, when present, does not extend downwards the interorbital pillar, nor does it descend below tozygomatic suture.
ecus is taken Pongo clade.
to
be a derived
Temporo-glabellar The the
character
linking
to of of
it to the
temporo-glabellar These bony
ridges in ridges are
unusual in primates and were taken to be an autapomorphy of Afropithecus by Leakey et al. (1988a). Their presence in the Otavi specimen suggests a possible phylogenetic relationship between the two genera. Such a relationship has already been proposed by Andrews (1992) on the basis of mandibular and dental evidence, but Pickford et al. (1994) argued that this was unlikely. The interesting point is that in the Otavi frontal these ridges have been reduced in relief partly because of inflation of the superior surface of the frontal above the enlarged sinuses. Further inflation of this region could well lead to reduction in relief of these ridges or to their disappearance and to suppression of the post-glabellar frontal sulcus that lies between them, in which case the frontal would more closely resemble that of other hominoids in which these ridges
do
Systematics arises as to whether Otavipithecus should be a synonym of Afropithecus, but the frontal and
the holotype mandible of Otavipithecus are morphologically markedly different in several important respects from their counterparts in Afropithecus. Pickford et al. (1994) enumerated the differences between the mandibles and dentition of Otavipithecus and Afropithecus, and the Otavi frontal serves to amplify the distinctiveness of these two genera and indicates that synonymy would be inappropriate. The postorbital while it is much
constriction in Afropithecus less so in the Otavi specimen.
is marked, In the Otavi
frontal the sinuses have been greatly enlarged in comparison with those of Afropithecus and the temporal crests have not only shifted distally with respect to the superciliary crests but they have also moved considerably further apart. Thus, the frontal trigon in Afropithecus is considerably
smaller
C. R. Acad 1997
in
area
than
Sci. Paris, Sciences
325.459-466
is a smaller
species.
from
Thus,
Namibia
whereas
in
temporal crests far apart even at their most distal preserved extremity. In the Otavi specimen, the postglabellar frontal sulcus is positioned appreciably further distally than it is in Afropithecus. It is doubtful that the differences observed relate to sexual dimorphism. Finally, the angle between the frontal squama and the interorbital pillar in Afropithecus is very open, as in Aegyptopithecus, whereas in Otavipithecus this angle is more closed, being similar to those of vertically
pongids oriented
and African face.
apes,
suggesting
a more
Otavipithecus is plesiomorphic in its known cranial parts, being not greatly different from other Lower and Middle Miocene African hominoids. Compared with Proconsul, in some of its dental features it is derived towards the African Ape/Human clade, which is why Conroy et al. (1992) placed it close to the genus Kenyapithecus, but its frontal shows none of the derived features of extant African apes such as the development of a bar-like supraorbital torus (figure 3; table). In the past, various Eurasian Miocene hominoids have been proposed as hominid ancestors (i.e. #ancestral either to African apes and humans, or ancestral exclusively to Australopithecus) (Wu et al., 1986; de Bonis et al., 1990; Dean and Delson, 1992; Begun, 1995), or that they may be the stem members of the great apes and human clade (Alpagut et al., 1996) rather than having exclusive relationships with either the African apes or the pongines. We consider that these hypotheses are unlikely because all of the Eurasian pretenders to AAH ancestry have small or absent sinuses in the frontal squama ancl possess other characters of the splanchnocranium and dentition that ally
not occur.
The question considered
latter
boqe
Phylogeny
ridges
presence of oblique bony Otavi frontal is interesting.
the
frontal
Afropithecus the temporal crests meet relatively close behind glabella to form a frontal trigon behind which is a prominent sag&al crest, the Otavi specimen shows the
towards the fron-
Examination of fossil hominoids from Africa, including Proconsul and Otavipithecus, reveals that the roughened bone surfaces in the supraorbital region are confined the superciliary region, and are not as extensive as those Pongo. Thus, the extent of this vermiform morphology the bone surface in the supraorbital region in Dryopith-
though
hominoid
it is in
de la terre
Otavipithecus,
et des plan&es
even
them to the Pongo clade. Australopithec-ines Homo, in contrast, possess enlarged frontal invade the frontal squama and the supraorbital and are thus primitive in this set of features. The above can be summarised as follows 1) Otavipithecus clade and greatly Miocene hominoids
and early sinuses that eminence (figure
3):
points to an African origin of the AAH weakens hypotheses in WI- ich Eurasian are viewed as ancestral to the AAH
clade; 2) the Otavipithecus frontal with its extensive sinuses suggests that the reduced sinuses of Dr:vopithecus and Ouranopithecus represent a morphology derived towards the condition found in the Pongo clade in which frontal sinuses are reduced or even absent; 3) european Late Miocene apes are phylogenetically closer to the Asian Pongidae (Sivapithecus, Lufengpithecus, Pongo) than to the AAH clade, but appear to form a clade of their own (containing Dryopithecus,, Ankarapithecus and Ouranopithecus) within the family Pongidae.
/ Earfh & Planetary
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M. Pickford
et al.
Acknowledgements: The authors would like to thank the Geological Survey of Namibia (Dr B. Hoal, Dr G. Schneider) for logistic and administrative support that led to the recovery of the Otavi frontal. Research permission was accorded by the National Monuments Council of Namibia (Mr G. Hoveka. Mr A. Vogt). Thanks are also due to the College de France (Prof. Y Coppens), the Museum National d’Histoire Naturelle (Prof. Ph. Taquet) and the Mission of Co-operation and Cultural Affairs, Windhoek (M. Yves Make. Mme N, Weir). Goldfields Namibia and the Development Brigade Corporation of Namibia provided access to Berg Aukas Mine, Namibia. Thanks are ulso extended to the National Museum of Uganda (Mr E. Kamuhangire. Mr E. Musiime) for access to the Napak hominoid samples, Angel lsobel kindly made casts of the Otovi specimen. Last, but by no means least, we thank Dr B. Senut, co-leader of the Namibia Palaeontology Expedition for her continued involvement in this project.
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