^ s CM LI B RARY OF THL U N IVER.SITY or ILLINOIS 550.5 FI v.7-9 UROLOGY UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN GEaOGY . I ® stamped below GEOLOGY LIBRARY L161— H41 k^r- Vw. a03 ^ go ' THE UWWrr OF THE JAN 2 2 1941 OHIVERSnY OF ILUNOIS GEOLOGICAL SERIES OF FIELD MUSEUM OF NATURAL HISTORY Volume 8 Chicago, December 31, 1940 No, 3 THE STATUS OF PROGALEOPITHECUS AMEGHINO By Bryan Patterson Assistant Curator of Paleontology Despite its arresting name, the genus Progaleopithecus (Ameghino, 1904, pp. 171-175; 1906, pp. 348-349, figs. 181, 182) has received scant attention in the Hterature of paleontology and zoogeography. Apart from the work of the original describer, I have encountered no reference to it, even in the voluminous compilations of such authors as Arldt and Scharff . This is a little surprising, for it is obvious that if the conception of relationships implied in the name were to be substantiated, the genus would be of great paleontologic and zoo- geographic interest. Ameghino described two species from the Deseado formation of Patagonia, P. fissurellatus and P. tournoueri. The latter was based on two specimens, one of which is a mandibular fragment with part of the dentition. This specimen is now in the Collection Tournouer of the Laboratoire de Pal^ontologie, Museum National d'Histoire Naturelle, in Paris, where I was able to study it during the summer of 1938. The specimen consists of the symphysis and a portion of the left ramus bearing the incisors, canine and first two premolars, all very little worn. For reasons that will be presented below, it is believed that these teeth are of the deciduous, rather than of the permanent dentition as Ameghino thought. In addition, there is an associated right canine and dp^. Ameghino's figure was almost certainly drawn from this individual. The first two incisors are similar in structure and both are approxi- mately as long as wide at the base of the crown ; the second is some- what larger than the first and has a slightly wider root. The crowns are high and divided into two cylindrical columns for almost their entire lengths. The external (posterior) column of each is rather longer than the internal, and its base is a little inclined forward from the vertical axis of the tooth. Di^ is strikingly dissimilar to its predecessors and closer, structurally, to the canine. It is convex No. 487 21 22 Field Museum of Natural History — Geology, Vol. 8 externally and concave — almost shovel-shaped — internally. The upper portion of the internal surface bears two grooves, the anterior one somewhat larger than the posterior, which isolate a cusp-like element. Two indentations, of which the anterior is much the deeper, occur on the cutting edge and continue downward into the grooves in the internal side. The canine differs from di^ in that it is larger and relatively longer; a low posterior heel is present, the portion of the crown in front of the anterior groove is larger, and the posterior groove Fig. 8. Progaleopithecics tournou'eri Ameghino. Dorsal view of the right dps and portion of mandible with left dix-dp^. Approximately 3/1. and indentation are notably smaller. The protoconid is clearly adumbrated. Dpx is in general similar to the canine. The heel is larger and set off anteriorly by a ridge — the metaconid ridge — behind which is a well-defined groove. A very slight depression is present externally behind the protoconid. The cutting edge indentations, internal grooves and isolated cusp are precisely as on the canine. The an- terior portion of the crown is longer, however, and the tooth as a whole more convex externally and more concave internally. Di^, canine and dpy are imbricating, the posterior extremity of each tooth overlapping the anterior extremity of its successor. The crowns of all three taper very rapidly toward their bases; the roots are stout, single and also rapidly tapering. Dp^ is double-rooted, each root also having the characteristic cone-like shape. Several advances over dpx may be seen. The proto-metaconid is much stouter. 0^5 I The Status of Progaleopithecus 23 expanded antero-externally-postero-internally and demarcated pos- teriorly by well-defined external and internal grooves. The anterior wing of the trigonid is as long as the proto-metaconid and the talonid combined, and is decidedly curved antero-internally. The heel is considerably larger and bears an incipient entoconid ridge. On the Fig. 9. Progaleopithecus tournoueri Ameghino. External and internal views of portion of left mandible with diy-dp^. Approximately 3/1. internal surface the isolated cusp is large, the anterior groove small, and the posterior groove well developed. The symphysis is fairly deep, moderately sloping upward anteri- orly and, as Ameghino noted, completely fused. MEASUREMENTS Dii Dij Dig Dc Dpx Dp^ A.-p. diam 1.4 1.6 3.0 4.0 4.9 5,3 Tr.diam 1.4 1.9 1.4 1.7 1.9 2.0 24 Field Museum of Natural History— Geology, Vol. 8 It is quite clear that Progaleopithecus is not referable to the Galeopithecidae. The comb-like first and second incisors, the elongate, multi-cusped third incisor^ and the shallow symphysis of Galeopithecus and of Galeopterus distinguish these forms so sharply from the Deseado genus that close relationship is out of the question. Progaleopithecus is in all its characters a typical member of the notoungulate suborder Typotheria and is certainly referable to the Interatheriidae,2 with which Ameghino's Progaleopithecidae (listed but not defined in 1906, p. 471) accordingly becomes synony- mous. With but little change the description given above would be applicable to the milk dentition of Protypotherium sp. figured by Sinclair (1909, pi. 5, figs. 13, 14). Resemblance between the two specimens is so close as to leave no doubt that the dentition under discussion is of the deciduous series; the rapidly tapering crowns and roots of di^-dpTj^ are particularly characteristic. Also, behind and beneath dp^^ in the Paris specimen there is a cavity, sectioned by the breakage of the ramus, which contains tooth fragments at its base. Recognition of the interatherid affinities of Progaleopithecus suggests the possibility that the genus may be based on the milk dentition of one of the four Deseado members of the family, Plagi- arthrus (= Argyrohyrax) , Archaeophylus, Cochilius and Phanophilus, all described prior to 1904.^ At present, however, it is not possible to identify it with any one of them. The only known species of Pla- giarthrus, P. clivus, is much too large. Cochilius includes species of appropriate size, but it is primarily a Colhu^-Huapi genus with but one species described as coming from the Deseado, and this with some reserve (Simpson, 1932, p. 5). Phanophilus is so inadequately 1 The dental formula of the Galeopithecidae is variously interpreted; the arrangement followed here is Cabrera's. 2 Ameghino (1904, p. 172) recognized the resemblances, as he almost invari- ably did in such cases, but regarded them as evidence that Galeopithecus was an exceedingly specialized descendant of the Typotheria. ^ Simpson (1932, pp. 5-8) was in some doubt as to whether the first three of these were all valid. A skull of Plagiarthrns in the Field Museum collection (P13415) appears to me to demonstrate that this genus and Cochilius are distinct from each other. An incomplete mandible (P14687) tentatively referred to Archaeophylus differs considerably from either of these two forms in the structure of P3. The distinction is sufficiently great, considering the rather unvarying nature of the interatherid lower premolar-molar series, to justify belief that the animal represented by this specimen is also generically distinct. Unfortunately, however, the tentative reference is somewhat uncertain, for Ameghino (1897, p. 423) gave rooted premolars as a diagnostic character of Archaeophylus, whereas Pg-? are rootless in P14687. It is possible that Ameghino may have been mistaken in this (Simpson, op. cit., p. 7), but the possibility can not be explored at present. The most that can be said now is that the mandible in question indicates either that Archaeophylus is valid or that there is an additional interatherid in the Deseado fauna. The Status of Progaleopithecus 25 known that, although its validity is unquestionable, its relationships are somewhat doubtful. Identity with Archaeophylus, if the genus be valid, is possible, but more material of this form is necessary before an opinion can be reached. In conclusion, I wish to express my sincere thanks to the American Association of Museums for the award of the Carnegie Grant that made the examination of the Tournouer collection possible, and to Professeur Camille Arambourg and Miles. Raymonde Cintract and J. Signeux of the Laboratoire de Pal^ontologie for their unfailing courtesy and kindness during my stay at the Museum National. The drawings have been made by Mr. John J. Janecek from stereo- scopic photomicrographs taken by me. REFERENCES Ameghino, F. 1897. Mammiferes cretac^s de I'Argentine (Deuxifeme contribution a la con- naissance de la faune mammalogique des couches a Pyrotherium). Bol. Inst. Geog. Arg., 18, pp. 406-521, figs. 1-86. 1904. Nuevas esi>ecies de mamiferos, cretdceos y terciarios de la Rep6blica Argentina. An. Soc. Cient. Arg., 57, pp. 162-175, 327-341; 58, pp. 35-41, 56-71, 182-192, 225-290 [continued from 56, pp. 193-208, 1903]. 1906. Les formations sedimentaires du Cretace sup6rieur et du Tertiaire de Patagonie avec un parallele entre leurs faunes mammalogiques et celles de I'ancien continent. An. Mus. Nac. Buenos Aires, 15, [(3), 8], pp. 1-568, figs. 1-358, pis. 1-3. Simpson, G. G. 1932. New or Little Known Ungulates from the Pyrotherium and Colpodon Beds of Patagonia. Amer. Mus. Nov., No. 576, pp. 1-13, figs. 1-9. Sinclair, W. J. 1909. Typotheria of the Santa Cruz beds. Rept. Princeton Univ. Exped. Patagonia, 6, pp. 1-110, figs. 1-16, pis. 1-11. THE UBflAKY OF THE JAN 2 2 1941 ONIV€RSlTY OF ILLINOIS