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Proceedings of the National Academy of Sciences of the United States of America logoLink to Proceedings of the National Academy of Sciences of the United States of America
. 1997 Jul 22;94(15):7993–7996. doi: 10.1073/pnas.94.15.7993

An upper dentition of Aframonius dieides (Primates) from the Fayum, Egyptian Eocene

Elwyn L Simons *,†, Ellen R Miller †
PMCID: PMC21543  PMID: 9223301

Abstract

The first known upper dentitions—an adult and subadult—of the cercamoniine adapiform Aframonius dieides are described. Comparisons show that A. dieides has an upper molar morphology resembling that of other cercamoniine adapids but the species lacks some of their typical specializations. The new dental material confirms that Aframonius stands closer to Mahgarita from west Texas and Cercamonius from Europe than it does to Schizarodon and Omanodon from Oman—all of which have been ranked as cercamoniines. Affinities of the latter two genera probably lie with the Anchomomys group. The presence of a cercamoniine adapid in the Eocene of Egypt supports the view that early African anthropoideans evolved not in isolation, but concomitantly with a contemporary Eocene prosimian radiation.

Keywords: Adapidae, Prosimii, evolution

This paper describes the first discovered upper dentitions of the cercamoniine adapiform primate Aframonius dieides from quarry L-41, Jebel Qatrani Formation, Fayum Province, Egypt. The Jebel Qatrani is a sequence of variegated sand and mudstones approximately 340 m thick. L-41 is located about 45–47 m above the base of the Jebel Qatrani and has been provisionally dated to the late Eocene by paleomagnetic studies, faunal correlation, and marine transgression analyses (refs. 1–5, but see also ref. 6). Quarry L-41 contains a rich array of Paleogene animals, including multiple species each of primates, hyraxes, creodonts, rodents, and insectivores, as well as fish, lizards, frogs, snakes, turtles, crocodiles, and birds. The morphologic and taxonomic diversity of the L-41 primates is unrivaled at other African Paleogene localities. At present this quarry has yielded nine primate genera. Four of these are prosimians [Wadilemur, Anchomomys (7), Plesiopithecus (8, 9), Aframonius (10)]. The other five, Serapia, Arsinoea (8), Catopithecus (4, 5, 11), Proteopithecus (4), and Qatrania sp. nov., are archaic anthropoideans. Serapia and Qatrania are parapithecids, and Catopithecus is an oligopithecine. Proteopithecus and Arsinoea have uncertain anthropoidean affinities, and Plesiopithecus is an unusual large nocturnal prosimian. Wadilemur and Anchomomys are small cercamoniine adapids, and Aframonius is a large one. L-41 presents an unusual primate community structure in that two of the prosimians, Plesiopithecus and Aframonius, are larger than any of the four described anthropoideans (Catopithecus, Arsinoea, Proteopithecus, and Serapia), and two other prosimians (Wadilemur and Anchomomys) are much smaller than the smallest anthropoidean.

A. dieides was first described in 1995 on the basis of three mandibular specimens (10), and its recovery was the first documentation of a large cercamoniine in Africa. Two small adapids from Oman, Omanodon and Shizarodon, have been attributed to the anchomomyiine tribe of this subfamily, but these specimens represent animals far smaller than A. dieides. In addition, Omanodon and Shizarodon, if separable from Anchomomys, are more closely related to the small anchomomyiines Wadilemur and Anchomomys from L-41 (12). A point of general significance concerning all of the L-41 primates is that, together with Omanodon and Schizarodon from Oman (12), Djebelemur from Tunesia (13), and Algeripithecus and Tabelia from Algeria (14), they show that Eocene members of Prosimii were widely distributed and morphologically diverse, and that early anthropoideans were, as stated by Rasmussen (15), “… older, smaller, structurally more primitive, and geographically more widespread” than previously suspected.

TERMS

The common noun “anthropoids” is used by many to refer to early, middle, and late Cenozoic members of suborder Anthropoidea. However, especially in Europe, this term refers informally to the anthropoid apes. Other scientists, particularly in France, call members of this suborder simians. For more precise reference here, and in continuance of usage by one of us (E.L.S.), these animals are here called anthropoideans.

SYSTEMATICS

Order Primates Linnaeus, 1758; Suborder Prosimii, Illiger, 1811; Family Adapidae, Trouessart, 1879 (s.l.); Subfamily Cercamoniinae, Gingerich, 1975.

Aframonius dieides

Holotype.

Cairo Geological Museum 42202, left dentary with well preserved P3–M3 (see figure 1 of ref. 10).

Hypodigm.

Duke University Primate Center (DPC) 15190 right maxillary fragment with alveolus of C1 and P2–M3; DPC 9859 subadult left maxillary fragment with dP4, M1–2.; DPC 11595, left dentary with alveoli for I1–P2 and crowns of P3–M3 (M1 and M3 broken); DPC 12437, left dentary with C1–M3 and right dentary with a broken root of I2, base of C1 crown, and P2–M3 (see fig. 3 in ref. 10).

Distribution.

Known only from the type locality: L-41, Fayum Province, Egypt.

Diagnosis.

This is repeated in part from ref. 10. A. dieides is a cercamoniine with a relatively shallow dentary and symphyseal fusion in older individuals. The incisor roots are small and implanted vertically and the central incisor alveolus is smaller than that for the lateral one. The canines are dimorphic in size. There are three premolars; P2/2 is very reduced in size although it shows a honing facet for the upper canine. P3–4 are both wedge-shaped and have a broad, complex talonid shelf. The lower molars are crested and have relatively long and narrow crowns. There is no paraconid, and the entoconid is positioned at the posterolingual corner of the talonid. The lower third molar has a narrow, but well developed, hypoconulid lobe on the talonid. Aframonius is most similar to Protoadapis and Europolemur in size and molar form but differs in having more complex premolars and more dimorphic canines, and in exhibiting fusion of the mandibular symphysis. The upper premolar size sequence is P2 < P3 < P4 with the crown of P2 less than 1/5th the size of P3. P2 has no lingual cusp, P3 has no distinct lingual cusp but has a strong, sharp lingual cingulum, and P4 has a distinct inner cusp and strong surrounding basal cingula, as well as distinct stylar flexures on each side of the buccal cusp. Upper molars are subequal with well developed basal cingula except on the buccal side of the hypocone, and slight parastylar flexures as well as pronounced, buccally flexed metastyles are present on all three upper molars. A hypocone, paraconule, and metaconule are present on M1–3 with the hypocone smallest on M3. A. dieides differs from other cercamoniines in showing a pattern of fine wrinkling, somewhat as in Aegyptopithecus, on the lingual slopes of the protocone and posterior slope of the paraconule, as well as throughout the trigon basin, particularly on M2–3. This wrinkling can be detected on unworn lower teeth as well.

DESCRIPTION OF NEW MATERIAL

The upper right dentition of DPC 15190 (Fig. 1) is a comparatively unworn series so that tooth crown morphology can be readily studied. Both P4 and M1 are slightly damaged. The canine alveolus of DPC 15190 is incomplete as its outer edge is broken off, but judging from what can be seen the canine would have been relatively large. There are three upper premolars. The anterior premolar, P2, is a small conical tooth with sharp mesial and distal crests. The middle premolar, P3, is larger than P2 and triangular in occlusal outline. P3 has a single buccal cusp and a nearly complete basal cingulum. P4 is trapezoidal in occlusal outline, with the mesial portion being slightly longer than the distal. The buccal cusp is high and sharp, and the lingual cusp is about one-third the height of the buccal cusp and rises out of the mesiolingual cingulum.

Figure 1.

Figure 1

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Scanning electron micrograph of DPC 15190. Upper right P2 to M3 of A. dieides. Note the large canine socket, the greatly reduced P2 as well as the similar-sized and highly crenulate molars. Scale ×9.

Upper molars of DPC 15190 are transversely broad with buccal and lingual portions about equally developed. The trigon is clearly defined, and all three cusps are high and sharp. A paraconule is present and positioned far mesially. The preparacrista first descends mesially and then curves lingually to the paraconule. The preprotocrista descends directly mesially from the apex of the protocone to the paraconule. The enamel is wrinkled and particularly striated on the lingual aspect of the protocone and hypocone. No pericone is present. Mesial, buccal, and distal cingula are strong, and the hypocone is developed out of the lingual cingulum. A metaconule is either absent or weakly developed. There is no mesostyle, but there is slight buccal flexure of the ectoloph.

The upper first molar is broad with strong mesial, buccal, and distal cingula. The tips of the metacone and hypocone are broken in this specimen. The hypocone is a small distinct cusp formed out of the distolingual cingulum. A small paraconule is present. There is no metaconule, instead the postmetacrista and postprotocrista form a low continuous crest.

The second upper molar differs from M1 in having a larger and more distinct hypocone, and in having a metaconule that is present, although weak. The paraconule is small and inconspicuous. The postparacrista and and premetacrista descend slightly buccally from the apices of the paracone and metacone, respectively, to form an ectoloph that is asymmetrically flexed with the distal portion (premetacrista) being longer and better defined than the mesial (postparacrista).

The third upper molar is almost as large as M2. M3 has a large well developed protocone, and a hypocone is present as a small cusp arising from the lingual cingulum. The M3 hypocone is much reduced relative to the size of the M2 hypocone and is even smaller than the M1 hypocone. A small paraconule is present. There is no distinct metaconule, but a low crest connects the bases of the metacone and protocone. Unlike M2, the postparacrista and premetacrista are of approximately equal length. Unlike the lower molar series the upper molars do not increase in size from front to back.

The second maxillary fragment, DPC 9859, is a left subadult specimen with dP4 and M1–2 (Fig. 2). The dP4 is molariform and distinctly smaller and lighter colored than M1–2, which are subequal in size and both a little smaller than in DPC 15190. DPC 9859 has a DP4 that lacks a hypocone and hence looks like a molar trigon; however, there is a flexure in the basal cingulum where the hypocone would be. Both paraconule and metaconule are present on the dP4. A parastyle and metastyle are present, but as in the molars there is no mesostyle. The molar crown morphology of DPC 9859 confirms that seen in M1–2 of DPC 15190, including the presence of wrinkled enamel.

Figure 2.

Figure 2

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Scanning electron micrograph of DPC 9859. Upper left subadult dP4, M1–2 of A. dieides. Note the triangular, but molariform, dP4 and crenulated molar enamel. Scale ×11.

COMPARISONS

The presence of broad molars with wide central basins, reduced P2/2, continuous or nearly continuous cingula, well developed hypocones isolated from the trigon, buccal flexure of the ectoloph, and occurrence of a paraconule along with weak or absent metaconules give A. dieides an upper molar morphology resembling that of other cercamoniine adapids such as Periconodon (16) and Mahgarita (17). At the same time, A. dieides is distinct in the simplicity of its upper molar structure as it lacks many specific features characteristic of its closest relatives. For example, while the P2 of A. dieides is small, as in other cercamoniines, it is not peg-like as in Mahgarita. Also the M3 of A. dieides is a large tooth and not reduced as in Mahgarita. In addition, A. dieides lacks: (i) a pericone present in Periconodon, Hoanghonius (18), Rencunius (19), and Djebelemur (14); (ii) a mesostyle clearly developed in Caenopithecus (16, 20); (iii) the crescentic protoconule characteristic of Hoanghonius, and (iv) the expression of prominent metaconules and centrocrista seen in Hoanghonius and Rencunius.

A. dieides can be compared in absolute size to various cercamoniines, contemporary prosimians, and early anthropoideans. Size comparisons for those species that have upper premolars and molars intact are as follows:

A. dieides, length of P2–M3 is 19.7 mm.

Mahgarita stevensi, length of P2–M3 is 15.9 mm.

Pronycticebus gaudryi, length of P2–M3 is 15.5 mm.

Caenopithecus lemuroides, length of P2–M3 is 23.6 mm.

Plesiopithecus teras, length of P2–M3 is 14.0 mm.

Catopithecus browni, length of P2–M3 is 13.4 mm.

Proteopithecus cocaenus, length of P2–M3 is 11.5 mm.

DISCUSSION

Simons et al. (10) discussed a number of mandibular features shared by cercamoniine adapids, including A. dieides, that possibly linked cercamoniines with early anthropoids. Among these were mandibular fusion, possession of canine dimorphism, and incipient development of a canine/premolar honing complex. Evidence of canine, and thus presumably sexual size dimorphism, was documented for most Fayum Oligocene anthropoideans many years ago by Fleagle et al. (21), and the same canine dimorphism has been recently reported for Catopithecus (22) and the mandibles of Aframonius (10). However, DPC 15190 is currently the only known adult maxilla of A. dieides, and recovery of a number of maxillae with the canine preserved will be necessary to document fully the degree of canine/sexual dimorphism and canine premolar honing function in this species. The large canine socket partially preserved in DPC 15190 may indicate that this individual is a male, and if so, the presence of a large upper canine would be in agreement with evidence from the lower dentition for their being considerable canine dimorphism in Aframonius (10).

In true catarrhines, as in the early anthropoideans Oligopithecus and Catopithecus, P2/2 has been lost, and the upper canine hones against P3. In DPC 12437, a lower jaw of A. dieides, the small size of P2, and wear facets on P2 and P3 indicate that honing was in the process of being transferred distally. A similar transfer of honing function is also evident in Caenopithecus and perhaps also in Djebelemur and Mahgarita, although it cannot be confirmed in the later two genera. In the upper dentition of A. dieides, DPC 15190, the canine is not preserved but P2 is very small as would be expected if the second premolar was in the process of being lost and the canine premolar honing function shifted distally.

Information about the morphology and geographic distribution of cercamoniine adapids is important for interpreting the origin of anthropoid primates, as some researchers have argued for a close relationship between cercamoniines and early anthropoideans from Africa (15, 19, 23–25). For example, Rasmussen and Simons (26) discussed morphological similarities of the upper dentition shared between the cercamoniine Protoadapis (27), its allies (Europolemur, Mahgarita, Periconodon, and Hoanghonius), and the early anthropoidean Oligopithecus. Rasmussen (25) also noted affinities in molar structure between the cercamoniine Mahgarita and the early anthropoideans Catopithecus, Oligopithecus, and Dolichocebus. In terms of geographic distribution, the recovery of a cercamoniine adapid from North Africa, together with recent discoveries of Paleogene primates from Oman, Tunesia, and Algeria supports the position that early African anthropoideans did not evolve in isolation but as part of a larger African Eocene primate radiation.

Acknowledgments

We thank F. A. Ankel-Simons, G. F. Gunnell, and D. T. Rasmussen for comments on the manuscript. We also acknowledge the assistance in Egypt of the staff and colleagues of the Egyptian Geological Survey and Mining Authority and the Cairo Geological Museum. We thank Prithijit S. Chatrath for assistance in Egypt. The specimens described here were prepared by F. A. Ankel-Simons and P. S. Chatrath. Scanning electron micrographs were taken at Duke University by L. M. Eivest. Support for the research reported here came from National Science Foundation Grants BNS-91–08445 and SBR-95–07770 and from Verna Cuddeback Simons and Gordon and Ann Getty. This is Duke Primate Center publication no. 646.

ABBREVIATION

DPC

Duke University Primate Center

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