Postilla

Published from 1950 to 2004, Postilla short papers are based on original scientific research by

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PPEEAABBOODDYY MMUUSSEEUUMM OOFF NNAATTUURRAALL HHIISSTTOORRYY,, YYAALLEE UUNNIIVVEERRSSIITTYY 170 WHITNEY AVENUE, P.O. BOX 208118, NEW HAVEN CT 06520-8118 USA PEABODY.YALE.EDU

YAL E PEABODY MUSEUM or NATURAL HISTORY

Number 57 November 30, 1961 New Haven, Conn.

T H E PHYLETIC POSITION OF RAMAPITHECUS

ELWY N L. SIMONS

Recent discoveries of early Pleistocene hominids at Olduvai gorge, Tanganyika, by expeditions under the direction of Dr. L . S. B. Leakey have pushed back certain knowledge of fossil man almost to the beginning of this epoch. To the extent that the K-A date suggested for these early men, 1.75 million years, (Leakey et al. 1961) is accurate, the beginning of the "Villa -franchian" provincial age, and thus of the Pleistocene itself, is shown to be considerably earlier than most previous esti-mates. I t therefore seems appropriate that renewed attention be drawn to the only Pliocene fossil primate specimen known to this writer, which can be defended as being within, or near, the population ancestral to Pleistocene and subsequent hom-inids, the type maxilla of Ramapithecus brevirostris at Yale Peabody Museum.

This maxilla, Peabody Museum No. 13799, was collected August 9, 1932 by the Yale North India Paleontological Ex-pedition under Dr. G. E. Lewis (Fig. 1). The geologic occur-rence of R. brevirostris was first given by Lewis (1934) as "Either latest Middle Siwalik [Dhok Pathan Zone] or basal upper Siwalik [Tat rot Zone]." However, Lewis (1937) later determined the horizon of Y.P.M. 13799 as being within the Nagri zone, which is of Pliocene early Middle Siwalik age.

2 Postilla Yale Peabody Museum No. 57

Gregory et al. (1937) also indicate the level of this specimen as Nagri.

Consequently, Hooijer and Colbert (1951) seem to have erred in listing Ramapithecus as occurring only in the Tat rot zone fauna which they suggest as being very close to the Plio-Pleistocene boundary. Regardless of these published differences in age determination the provenance of the specimen is known, so that, at least potentially, its temporal position can be veri-fied. Faunal correlations indicate that, even in the unlikely event that Ramapithecus occurs as late as the Tatrot horizon, this primate is distinctly older than the "Villafranchian" hom-inids of Olduvai gorge.

In spite of the significance of Y.P.M. 13799, as being pos-sibly the earliest known hominid, it has been largely overlooked, or briefly dealt with in the more recent summaries of hominid evolution, a common conclusion being that the type is too fragmentary to permit taxonomic assignment. Actually, such a conclusion is incorrect and misleading. This right maxilla provides at least some information as to shape, size or posi-tioning of the entire upper dentition except for M3, in that alveolae of I1"2, C are preserved as well as the series P3 through M2. Moreover the base of the nasal aperture can be seen above the incisors, and, contra Hrdlicka (1935), the dental arcade can be determined as parabolic and not U-shaped, as was correctly stated by Lewis (1934) in the original description of this form (see Fig. 2). Some may think (as Hrdlicka did) that extrapolating from the right maxilla alone, in order to determine that the disposition of the upper cheek teeth is in an arcuate line, instead of being arranged in the parallel series seen in all pongids, is a rather uncertain procedure. However, at one point (see arrow 1, figure 2) the maxilla reaches nearly, if not entirely to the point of the palatal intermaxillary suture. Since we may safely assume that Ramapithecus, like other vertebrates, was bilaterally symmetrical, if the right maxilla and its mirror-image are pivoted around this point the amount of posterior divergence of the cheek tooth rows cannot be further decreased beyond the arrangement shown in figure 2 without assuming an impossibly long basal diameter for the

Nov. 30, 1961 Phyletic Position of Ramapithecus 3

central incisor pair (figure 2, arrow 2). In fact, the space allowed for these teeth in figure 2 (in order to be on the safe side) is intentionally made greater than it is likely to have been. Preservation of the entire length of the alveolar cavity of the right central incisor allows for comparative measure-ments as to its size. The central incisor root of Ramapithecus is only about half as long as it is in a series of chimpanzees examined in this connection and which had cheek teeth of the same absolute size as Y.P.M. 13799. In orangutans the central incisors have, comparatively, still longer roots than does Pan. As is well known, possession of large incisors relative to cheek teeth is a general feature distinguishing both fossil and liv-ing pongids from known hominids. In this feature of central incisor size, as in others, such as the highly arched palate, Ramapithecus agrees more closely with Hominidae than with Pongidae.

I t is evident that most of the misapprehensions regarding Ramapithecus now current trace back to Hrdlicka's discussion of the specimen (1935) in which he insisted that the form could not be a hominid. Even a casual examination of. this paper is sufficient to show that it bears every evidence of being a controversial and non-objective contribution. In contrast to this, all of the hominid resemblances cited for Y.P.M. 13799 by Lewis (1934) appear to this writer to have been correctly drawn, and these are reinforced by the additional hominid features called to attention here.

However, another possible source of uncertainty regarding the genus may derive from a mandible, Peabody Museum No. 13807, assigned by Lewis (1934) to Ramapithecus, but to a different species R. hariensis. This mandible shows hetero-morphy in the lower premolars of the sort characteristic of pongids but which is not known in undoubted Hominidae. In view of this heteromorphy, not indicated in P3"4 of R. brevi-rostris and inasmuch as the mandible of R. hariensis comes from a different locality, and from a horizon that may be considerably lower in the section, I see no convincing reason for associating generically the form it represents with that of the maxilla of R. brevirostris.

4 Postilla Yale Peabody Museum No. 57

What then can be stated as fact regarding the type maxilla of Ramapithecus? As the species name implies, and as Lewis originally stated, this primate exhibits a reduction in prog-nathism, upper incisor size, and in length from the alveolar border above the incisors to the base of the nasal opening, when compared to pongids of its general size, whether living or fossil. This length from nasal aperture to I2 in Ramapithe-cus is approximately 44 per cent of the length of P3 - M2 (see arrows, figure 1) while corresponding percentages in a series of specimens of Pan range from 70 to 98. Specimens of Pongo and Gorilla examined fall within the range of Pan, in this proportion.

In addition to the foregoing differences, the upper incisors and canine, judging from their alveolae, cannot have been as large as they typically are in even the smallest Great Apes, a fact also pointed out by Lewis (1934), who remarked: "The face is very slightly prognathous, as contrasted with recent Simiidae. There are no diastemata in the dental series. The canine is small, not an antero-posteriorly elongated trenchant tusk but a hominid type with a transverse dimension exceeding the antero-posterior dimension." Lewis (1934: 163-166) fully discussed the dental characters of Y.P.M. 13799, consequently i t is unnecessary to repeat this description here. In general, crown patterns resemble both Dryopithecus and Australopi-thecus about equally.

Without further extending the polemical atmosphere sur-rounding this specimen, so unfortunately initiated by Hrdlicka, this writer will simply call attention to his final statement regarding Ramapithecus, since he appears to be the only per-son to have studied the actual specimen who has published doubts as to its hominid status. The significance of this remark, in the light of modern understanding of the australopithicines as hominids, seems to have been overlooked. Hrdlicka (1935:36) observed: "The genus [Ramapithecus], although in the upper denture, in general, nearer to man than are any of the Dryopi-theci or the Australopithecus cannot . . . be legitimately estab-lished as a hominid, that is a form within the direct human ancestry." This curious statement, indicates that Hrdlicka

Nov. 30, 1961 Phyletic Position of Ramapithecus 5

would now have to place the genus in the Hominidae since he regarded it as more man-like than Australopithecus, a genus universally accepted today by competent students as belong-ing to this family. Evidently if there are convincing reasons why Ramapithecus brevirostris should not be regarded as representing the earliest known hominid they have not been demonstrated to date.

To contend that the specimen is too inadequate for definite taxonomic assignment implies that pongids and hominids can-not be distinguished, even when reasonable information is available regarding the size, emplacement, structure and ar-rangement (whether arcuate or parabolic) of nearly all of the upper dentition, together with several characters of palate and face as well. Postcranial remains, if found, might make it easier to assign this primate taxonomically, but the six or seven distinct approximations to hominid morphology dis-cussed here for Y.P.M. 13799 provide an adequate basis for associating it with the latter family. I t seems illogical to choose the alternative of regarding this form as belonging to an otherwise unknown group of apes, parallelistic toward hominids but not closely related to them, when it occurs in the proper time and place to represent a forerunner of Pleistocene Hominidae.

REFERENCES

Gregory, W. K., M. Hellman and G. E. Lewis, 1937. Fossil anthropoids of the Yale-Cambridge India Expedition of 1935. Carnegie Inst. Wash. Publ. No. 495, pp. 1-27, 8 pi.

Hooijer, D. A. and E. H. Colbert, 1951. A note on the Plio-Pleistocene boundary in the Siwalik Series of India and in Java. Amer. Journ. Sci., v. 249, pp. 533-538.

Hrdlieka, A., 1935. The Yale fossils of anthropoid apes. Amer. Journ. Sci., v. 229, pp. 34-40.

Leakey, L. S. B., J. F. Evenden and G. H. Curtis, 1961. Age of Bed I,

Olduvai gorge, Tanganyika. Nature, v. 191, pp. 478-479. Lewis, G. E., 1934. Preliminary notice of new man-like apes from India.

Amer. Journ. Sci., v. 227, pp. 161-179, 2 pis. i Lewis, G. E., 1937. Taxonomic syllabus of Siwalik fossil anthropoids. Amer.

Journ. Sci., v. 234, pp. 139-147.

6 Postilla Yale Peahody Museum No. 57

Figure 1

Occlusal view (A) and lateral view (B) of right maxilla of type of Ramapithecus brevirostris, Y.P.M. 13799.

Nov. 30, 1961 Phyletic Position of Ramapithecus 7

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Postilla Yale Peabody Museum No. 57

Figure 2

brevirostrls, right maxilla, Y.P.M. 13799, and reverse of same, showing arcuate arrangement of teeth.

Nov. 30, 1961 Phyletic Position of Rainapithecus 9

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