Paraulacodus indicus, HINTON, 1933

Antoñanzas, Raquel López, Sen, Sevket & Mein, Pierre, 2004, Systematics and phylogeny of the cane rats (Rodentia: Thryonomyidae), Zoological Journal of the Linnean Society 142, pp. 423-444 : 433

PARAULACODUS INDICUS HINTON, 1933

Hinton (1933: 621–622) established the taxon Paraulacodus indicus ( Fig. 4K–M) on the basis of three specimens (G.S.I. D281–D283) from the Siwalik series in Pakistan (then part of northern India). Only a short diagnosis without illustrations was given, but Black (1972) provided a thorough systematic revision of this species including the first drawings of the three specimens available to Hinton (1933). The holotype (G.S.I. D283) is an incomplete right maxilla with P4-M2 ( Black, 1972: fig. 2a–c) from an unknown locality. G.S.I. D282 is a fragment of right mandible ( Black, 1972: fig. 2d–e) with m2 from near Chinji, and G.S.I. D281 is a left upper incisor ( Black, 1972: fig. 2f–h) from ‘below Kookar Dhok’ ( Black, 1972: 244).

There is definitely no reason to assume that these specimens where found associated and, furthermore, it is uncertain that they are from the same horizon. Interestingly enough, all three are believed to originate from the ‘Upper Chinji Zone’ ( Black, 1972), whereas specimens recently found in the Pakistani Siwaliks are from the Middle Chinji Formation (L. Flynn, pers. comm.). Be that as it may, G.S.I. D281– D283 are almost certainly all middle Miocene in age.

According to Jaeger et al. (1980: 369), the single lower molar G.S.I. D282 does not belong to Paraulacodus . Without justification, de Bruijn & Hussain (1985) considered G.S.I. D282 to be possibly an m1. Since the m1 are expected to be smaller than the m2, they assumed that the lower molar would be too large to fit with the type. Consequently, they evoked the possibility that Hinton’s (1933) material comprises more than one species: G.S.I. D282 would pertain to the genus Paraulacodus , but not to the species P. indicus . This option is rejected here because (1) the identification of isolated m1 and m2 is problematical (especially if the material is limited) and (2) the size variation in P. indicus is unknown.

An isolated upper molar of Paraulacodus aff. indicus from the Chinji Formation (Middle Miocene) in Pakistan was reported by Wessels et al. (1982: 358, pl. 2, fig. 14). According to these authors, the morphology of this tooth is identical to that of the holotype of P. indicus , but is much smaller. Flynn et al. (1983: 357) mentioned minor morphological differences such as the stronger hypsodonty and the stronger ectoloph of this specimen with respect to the upper molars of P. indicus . Owing to the great difference in size and slight morphological dissimilarities between this tooth and equivalent teeth of P. indicus, de Bruijn & Hussain (1985) considered that it does not belong to this species and designated it as Paraulacodus sp. , an opinion that we share.

De Bruijn & Hussain (1984, 1985) reported new specimens from the Sindi ( Pakistan) locality H-GSP. 82.14 (top of the Lower Manchar Formation, Middle Miocene) that they finally identified as Paraulacodus cf. P. indicus .

Recently, the Pakistani Siwaliks have yielded further specimens of this species ( Flynn & Winkler, 1994). This material consists of one right dentary fragment with m2-m3 and incisor (Y-GSP 31380, from locality 691), one left dentary fragment with m2-m3 (Y-GSP 31809, from locality 750), one upper incisor fragment (Y-GSP 33105, from locality 698), and six isolated teeth (Y-GSP 40066–40071, from locality 714). According to Jaeger et al. (1980), P. indicus differs from P. johanesi notably in having smaller upper incisors compared to the Ethiopian form. Yet, the size of incisors depends on the age of the individual. In addition, Flynn et al. (1983: 363) argued that, owing to the scarcity of comparative material, i.e. in the absence of a thorough knowledge of the variation, it is not possible to differentiate these species from a dimensional point of view. Finally, Jacobs et al. (1989: 167) asserted that both taxa are similar in size.

In the Asiatic species of Paraulacodus , the size discrepancy between the M2 and the M1 is greater than in P. johanesi . The anterolabial cusp on the lower molars is stronger in most specimens of P. indicus than in P. johanesi . Another difference is the tendency of the protoloph of P. indicus to bend forwards towards the labial end of the anteroloph (nearly closing the mesoflexus). Paraulacodus indicus differs from Paraphiomys pigotti , Paraphiomys hopwoodi , Paraphiomys sp. nov. from Saudi Arabia, Paraphiomys occidentalis , Epiphiomys coryndoni and Sacaresia moyaeponsi in lacking the metalophulid II on the lower molars, to cite just one among quite a few differences. Paraulacodus indicus differs from Neosciuromys africanus and Paraphiomys simonsi , for instance, in its smaller size and reduced hypsodonty. Paraulacodus indicus is much larger than Kochalia geespei , Paraphiomys shipmani , Paraphiomys orangeus and Apodecter stromeri . One of the main differences between P. indicus and Paraphiomys australis and Paraphiomys roessneri is the presence of an anterolabial cusp on the lower molars of the former.