Cachiyacuy cf. kummeli

Boivin, M, Marivaux, L, Orliac, MJ, Pujos, F, Salas-Gismondi, R, Tejada-Lara, JV & Antoine, P, 2017, Late middle Eocene caviomorph rodents from Contamana, Peruvian Amazonia, Palaeontologia Electronica 16 (7), pp. 1-50 : 29

Cachiyacuy cf. kummeli

Figure 5.11 , Appendix 3

2016 Canaanimys cf. maquiensis Antoine et al. , Supplementary data, p. 5.

2017 Canaanimys cf. maquiensis Antoine et al. , Supplementary data, p. 9.

Referred material. MUSM 2654, fragmentary left

M1 ( Figure 5.11 ).

Locality. Contamana CTA-51, Loreto Department,

Peru.

Formation and age. Pozo Formation, lower member, late middle Eocene ( Antoine et al., 2016).

Description. The MUSM 2654 M1 ( Figure 5.11 ) has an occlusal surface and a crown outline heavily worn, and lacks its posterolingual part. Although broken, the hypocone does not appear to have occupied a labial position, which indicates that this tooth is likely a M1. The posterior outgrowth of the protocone is short, which involves a very small mesiodistal constriction of the hypoflexus. The protoloph is transversely complete, its long labial part is slightly oblique (distolingually oriented), and its lingual part (posterior arm of the protocone) is short but strong (i.e., non-taeniodont pattern). The third transverse crest is strong, complete and links the mesial extremity of the oblique anterior arm of the hypocone (AAH) to a strong mesostyle labially. A strong, short, and longitudinal mure connects the third transverse crest-AAH junction to the lingual extremity of the labial protoloph, and closes the hypoflexus labially. Distolabially, there is a small metaloph, posterolabially directed, labially connected to the metacone/posteroloph and lingually to the mesolophule. The lingual connection of the metaloph with the third transverse crest is extended and includes a tiny fossette, which can be a part of the metaflexus. Its separation from the rest of the metaflexus is probably due to the strong occlusal wear. Mediodistally, there is a longitudinal accessory crestule linked to the posteroloph and almost to the metaloph. Because of the advanced state of wear, all flexi are entirely closed, except the hypoflexus which remains open lingually.

Comparisons. This specimen is comparable in size with Cachiyacuy kummeli , Canaanimys maquiensis , Eoespina woodi , and Eosachacui lavocati ( Frailey and Campbell, 2004) . The absence of taeniodont pattern of MUSM 2654 ( Figure 5.11 ) excludes affinities with Eoincamys , Eobranisamys , and Vallehermosomys mazzonii ( Frailey and Campbell, 2004; Vucetich et al., 2010). Although the M3s of C. maquiensis tend to have a lingual connection between the protocone and the protoloph (pseudo-taeniodont pattern), its M1–2s show a clear taeniodont pattern. The presence of a well-developed metaloph on MUSM 2654 is in sharp contrast with the condition found in E. woodi , E. lavocati ,? Vallehermosomys merlinae , and Draconomys verai ( Frailey and Campbell, 2004; Vucetich et al., 2010), in which this crest is absent, incipient or corresponding to a thickened posteroloph. In Cachiyacuy and Eosallamys , the metaloph tends to be more developed, like on MUSM 2654. In Cachiyacuy , the metaloph is transverse, and its lingual extremity can be connected to the third transverse crest and posteroloph via accessory crestules. In Eosallamys , the metaloph is usually only linked lingually to the posteroloph but on some upper molars (LACM 143422, 143363, 143376, 143380; in Frailey and Campbell, 2004, p. 120–122), it can be connected to the third transverse crest via an accessory crestule. Nevertheless, MUSM 2654 shows a smaller size, more slender crests with thinner enamel than upper molars of Eosallamys , and as such it appears closer in morphology and proportions to the upper molars of Cachiyacuy .

Figures

FIGURE 5. Scanning electron microscope images (in occlusal view) of fossil caviomorph teeth from CTA-47 (1-4), CTA-51 (5-12), CTA-73 (13-14) and CTA-66 (15-16).?Canaanimys sp. (1-2),?Cachiyacuy kummeli (3), Caviomorpha indet. 1 (4), Cachiyacuy cf. contamanensis 1 (5-7), Caviomorpha indet 2 (8-10), Cachiyacuy cf. kummeli (11), Eoespina sp. (12), Caviomorpha indet 3 (13), Caviomorpha indet 4 (14) and Eobranisamys sp. (15-16). 1, fragmentary right dp4 (MUSM 2645); 2, fragmentary left lower molar (MUSM 2646); 3, fragmentary left dP4 (MUSM 2648); 4, fragmentary right lower molar (MUSM 2647); 5, fragmentary right dp4 (MUSM 2651, reversed); 6, left m1 (MUSM 2652); 7, left m3 (MUSM 2653); 8, fragmentary right lower molar (MUSM 2656); 9, fragmentary left dP4 (MUSM 2657); 10, fragmentary left upper molar (MUSM 2658); 11, fragmentary left M1 (MUSM 2654); 12, right M2 (MUSM 2655); 13, fragmentary right lower molar (MUSM 2659); 14, fragmentary left upper molar (MUSM 2660); 15, fragmentary left upper molar? (MUSM 2841); 16, fragmentary left upper molar (MUSM 2842). Top scale for 1-12, bottom scale for 13-16.