Crateromys Thomas, 1895

Ochoa, Janine, Mijares, Armand S. B., Piper, Philip J., Reyes, Marian C. & Heaney, Lawrence R., 2021, Three new extinct species from the endemic Philippine cloud rat radiation (Rodentia, Muridae, Phloeomyini), Journal of Mammalogy 102 (2), pp. 1-22 : 13

Genus Crateromys Thomas, 1895

Crateromys is represented by one living species on Luzon ( Cr. schadenbergi ) and two additional species in other parts of the oceanic Philippines: Cr. heaneyi from Panay Island, and (possibly) extinct Cr. paulus from Ilin Island (near Mindoro); as noted above, molecular data indicate that Cr. australis from Dinagat Island (near Mindanao) should not be placed as a member of this genus ( Rowsey et al. 2018), and we do not include it in our treatment that follows. The cranial traits and features of external appearance of Crateromys species were described by Musser and Gordon (1981), Musser et al. (1985), Gonzales and Kennedy (1996), and Heaney et al. (2016a). Crateromys possesses high crowns, chevronate lower molar lophs, and strongly arched upper molar cusps that are separated by deep clefts and ridges ( Figs. 4 and 5 ). As detailed above, this contrasts with the medium crown height and less strongly arched cusps of Carpomys . Crateromys dentition is most similar to that of Batomys , but the members of these two genera on Luzon differ dentally in several respects. Both Crateromys and Batomys have hypsodont molars, but Crateromys has higher crowns than Batomys . Upper molars of Crateromys generally are more angular, whereas Batomys cusps are more rounded in occlusal outline. The angular shape of cusps in Crateromys in part is due to deep clefts that separate lingual and medial cusps of upper molars. In anterocone of M1, t1 and t2 are separated by a deep cleft, and this pattern is repeated for t4/t5 and t7/t 8 in all upper molars ( Fig. 2C ). These deep indentations are absent or less developed in most upper molar lophs in Batomys , with the exception of the posterior lophs (t7 and t8) in M1 and M2. In the Crateromys M1 anterocone, t1 and t3 are typically oriented anteriorly, whereas these cusps are oriented posteriorly in Batomys , producing a concave occlusal outline. Asimilar pattern is observed in the anterior loph of M2, where t4 and t6 are oriented anteriorly in Crateromys and transversely in Batomys . The anterior and posterior lophs of M3 have a more complex occlusal outline in Crateromys , whereas these lophs have a simpler laminar outline in Batomys . In Crateromys , the anterior and posterior lophs of m3 are chevronate and a posterior cingulum is occasionally observed; in Batomys , the anterior loph is not arched and the posterior loph is laminar or oblong in outline. Our assignment of the following new species to Crateromys is based on its possessing this set of characters.

Figures

Fig. 4.—Occlusal view of maxillary molars of (A) Carpomys dakal n. sp. (PNM II-1977-J11A-15997), left side; (B) Carpomys phaeurus (FMNH62291),leftside;(C) Musseromysinopinatus(FMNH193840), left side; (D) Crateromys ballik n. sp. (PNM II-1977-J3-10389), right side (mirrored); (E) Crateromys schadenbergi (FMNH 62291), right side (mirrored); (F) Crateromys heaneyi (CMC M626), left side; (G) Batomys granti (FMNH 214412), left side.

Fig. 5.—Occlusal view of mandibular molars of (A) Carpomys dakal n. sp. (PNM II-1977-J11A-16301, holotype), leftside; (B) Carpomys phaeurus (FMNH62291),leftside;(C) Musseromysinopinatus (FMNH 193840), left side; (D) Crateromys ballik n. sp. (PNM II-1977-I8-402, holotype), right side (mirrored); (E) Crateromys schadenbergi (FMNH 62291), left side; (F) Crateromys heaneyi (CMC M626), left side; (G) Batomys cagayanensis n. sp. (PNM II-1977-J3-7554, holotype), right side (mirrored); (H) Batomys granti (FMNH 214412), left side.

Fig. 2.—Maxillary and mandibular left molar toothrows of Carpomys dakal n. sp. (A and B, respectively; PNM II-1977-J11A-15997 and PNM II-1976-M-101) and Crateromys schadenbergi (C and D, respectively; FMNH 62295), showing the location of cusps and conids referred to in the text. pc = posterior cingulum.