Cyclomylus lohensis, Matthew and Granger, 1923

WANG, BANYUE, 2001, On Tsaganomyidae (Rodentia, Mammalia) of Asia, American Museum Novitates 3317, pp. 1-52 : 15-18

mylus lohensis . However, they misidenti­

fied the other specimens. The paratypes

designated by them include, in fact, two

different genera: Tsaganomys and a new

genus, Coelodontomys (see below). Their

line drawings illustrating the reconstructed

skull of T. altaicus were based on speci­

mens belonging to different genera (Mat­

thew and Granger, 1923: figs. 1–3). This

may be one of the factors that led to great

confusion in the later classification of the

Tsaganomyidae . Fig. 10. Cheek teeth of Tsaganomys altaicus One of the main problems confounding A. Cheek tooth of IVPP V 11389.3. A1. Occlusal view. A2. Anterobuccal view. A3. Posterolingual classification is cheek tooth morphology. Beview. B. Longitudinal section of cheek tooth cause the enamel is very thin on the occlusal ( IVPP V 11409.1) showing dentine part (d) and surface of the cheek teeth and the cusps and pulp cavity (p). lophs are very weakly expressed, the occlu­

sal pattern is easily worn away. When worn

the cheek teeth become cylindrical and uniprisms of the PE are almost vertical to the laterally hypsodont, and have smooth, consurface of the enamel. The HSB of the PI is cave occlusal surfaces. Superficially there composed of 5–7 prisms and has about 20– seems to be no difference among the teeth. 30° inclination. Careful observation reveals that among the DIMENSIONS: See table 1. paratypes listed by Matthew and Granger DISCUSSION: Based on holotypes, Mat­ (1923) there are two different kinds of hypthew and Granger (1923) rightly distin­ sodont teeth: one has a well­developed den­

tine part composed of primary dentine, a short conical pulp cavity with pointed apex, and a high ratio of dentine part to pulp cavity; the other one shows opposite trends. In addition, the skulls that bear these two kinds of teeth differ in morphology (see table 6). The former is typical of Tsaganomys , but the latter represents a new taxon ( Coelodontomys ). Shevyreva (1972) rightly distinguished two kinds of teeth among the strongly hypsodont cheek teeth. Unfortunately, however, she referred them incorrectly and named a new genus and species, Beatomus bisus , without figuring the holotype. According to her description and figures of the other specimens (Shevyreva, 1972: fig. 6; 1974a: figs. 1d, e, 2, 3). Beatomus bisus shows typical Tsaganomys tooth morphology. On the other hand, her Tsaganomys is quite different from the holotype of Tsaganomys altaicus but similar to Coelodontomys . It seems that Beatomus bisus is a junior synonym of Tsaganomys altaicus .

Kowalski (1974) described Cyclomylus minutus from Khatan Khayrkhan, Mongolia. Huang (1993) relocated this species into Tsaganomys. Bryant and McKenna (1995) considered T. minutus as a synonym of T. altaicus. I have not seen Kowalski’s holotype, and I am not certain whether it is a Tsaganomys. However, I observed Huang’s specimens from Ulantatal area, Nei Mongol, China. They are typical of Tsaganomys. The measurements of the Ulantatal specimens indicate that they are within the range of Tsaganomys altaicus. The measurements of the cheek teeth of Tsaganomys show no obvious size groupings among the specimens (fig. 14). The available material indicated that young individuals are small and some cheek teeth show a size increase from top to base. I agree with Bryant and McKenna (1995) that T. minutus of Hung (1993) is a junior synonym of T. altaicus. The cheek teeth of T. altaicus all have open roots at all stages of wear.

Tsaganomys sp. of Teilhard de Chardin (1926) from Saint Jacques, Nei Mongol, China, referred to Cyclomylus lohensis by Kowalski (1974: 158) is T. altaicus, as well.

Among the specimens of ‘‘ Tsaganomys and/or Cyclomylus ’’ from the Buran Formation in Zaysan Basin, Kazakhstan, listed by Emry et al. (1998), only K35(15)/424 belongs to T. altaicus (Emry et al., 1998: fig. 8 A).

Emry and Korth (1996) considered Morosomys Shevyreva (1972) a synonym of specimen, IVPP V 11405. Checking the orig­ Tsaganomys. It seems that Morosomys rep­ inal label I found that V 11405 was collected resents a taxon distinct from Tsaganomys in from the upper member of the Wulanbulage having brachydont cheek teeth and other fea­ Formation near IVPP Loc. 78016 rather than tures. in Loc. 78016 of the Yikebulage Formation.

Wang et al. (1981) listed Tsaganomys sp. Thus, Tsaganomys does not occur in the Yikfrom the Yikebulage Formation based on one ebulage Formation.

TABLE 1 Measurements (mm) of Cheek Teeth of Tsaganomys altaicus