101 Aert Van Neslaan, Oegstgeest, the Netherlands

THE SOLUTION OF THE CRYPTOMASTODON PROBLEM

D. A. HOOIJER (101 Aert van Neslaan, Oegstgeest,The Netherlands)

SUMMARY

Cryptomastodonmartini Von Koenigswald from the Pleistocene of Java is based upon two molar fragments and a humerus portion. The molar fragments originally described as Mastodonby Martin and by Van Es are referable to Stegodontrigonocephalus Martin. The humerus portion described as Problematicum by Stehlin belongs to the giant land tortoise Geocheloneatlas (Falconer & Cautley). As the material upon which Cryptomastodon martini has been based represents two already named taxa this name must be sunk.

INTRODUCTION

Nearly one hundred years ago, a fossil tooth fragment from the Pleistocene of Patiayam in Java was described by MARTIN (1888: 90/91, pl. XI figs. 1, la) as Mastodon spec. indet. It bears a number of conical cusps, unworn, with their apices curved towards each other. The specimen so much resembled part of a mastodont molar that Mar- tin unhesitatingly put it in the genus Mastodon, but refrained from specific determination. DuBOIs (1891: 95) remarked right away that Martin's specimen closely resembled the hinder end of Stegodon molars, but his remark went unheeded for many years. A fossil distal humerus portion from Limbangan in Java described by STEHLIN (1925: 9/10, figs. 1-3) was of the size of that of an elephant but differed somewhat in the extent of the fossae and the obliquity of the medial border. Unable to find out what creature the humerus belonged to, Stehlin left it as Problematicum. In 1931, Van Es described a molar portion from the Pleistocene of Sangiran in Java as Mastodon (?) (VAN Es, 1931: 66, figs. 3-4). It resembled Martin's specimen from Patiayam but was more complete; it showed the arrangement of the cones in transverse rows but lacked the median cleft characteristic of all mastodont molar ridges.

Cryptomastodon martini Von Koenigswald

In 1933, Von Koenigswald united the molar portions described by Martin and van Es with the humerus portion described by Stehlin into a distinct and most unusual proboscidean that he named Cryptomas- 229 todon martini VON KOENIGSWALD (1933, p. 112). A whole new family of Proboscidea, the Cryptomastodontidae, with Cryptomastodon as its sole occupant, was called for. It would have square molars, vertical tooth replacement, and somewhat unusual limb bones for an elephant as evidenced by the humerus. It was unbelievable that such a kind of proboscidean would have lived then and there in the Pleistocene of Java, along with the mastodonts, stegodonts, and elephants, and no place else in the world. And nobody did believe it. DIETRICH (1934) retorted that there was no basis for erecting Cryptomastodon as the molar portions could be accommodated in Stegodon, as detached ends of long molars somehow malformed. The humerus, however, remained as much of a problem to Dietrich as it had been to Stehlin. VON KOENIGSWALD (1934: 193) immediately rejoined that he was unable to accept Dubois' and Dietrich's interpretation of Cryptomastodon, adding that a new tooth had come in, from Pitu, but this specimen has never been described or figured and I have no information on it. In 1936 OSBORN (1936: 783) wrote that Cryptomastodon was a Sire- nian, cf. Desmostylus, and by now the confusion was complete. Most authors either ignore Cryptomastodon or place it as an aberrant Stegodon or as a desmostylid. It is not in SIMPSON (1945) but figures, with a query, among the Desmostylia in Romer's latest edition of Vertebrate Paleontology (ROMER, 1974: 386).

The Solution of the Cryptomastodon Problem In my opinion Dubois and Dietrich were correct in stating that the so- called Cryptomastodon molar portions belong to Stegodon. The posterior portion of a right lower last molar of Stegodon trigonocephalus Martin from the Pleistocene of Ola Bula in Flores (fig. 1) has the last two ridges Cryptomastodon-like, with nipplelike cones, whereas the two worn ridges are stegodontine, showing a row of subequal conelets. This may be seen as an atavistic deviation for stegodonts arose from mastodonts. but what about the humerus portion from Limbangan? I have come to the conclusion that the Limbangan humerus is not mammalian. The shallow coronoid fossa and the broadened olecranon fossa, and the obliquity of the medial border distally, differences bet- ween the Limbangan humerus and that of a proboscidean noticed by STEHLIN (1925) are just the points in which the humerus of the giant land tortoise, Geochelone atlas (Falconer & Cautley), differs from that of a proboscidean (cf. HOOIJER, 1971: pl. 1 figs. 5-6). Geochelone atlas has been known from the Pleistocene of Java since 1935 (VoN KoENics- WALD, 1935: 195), and the Limbangan humerus belongs there (HooIJER, 1982: 172).