Eobranisamys sp.
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publication ID |
https://doi.org/ 10.26879/742 |
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publication LSID |
lsid:zoobank.org:pub:540D23AA-F705-4A05-8E10-FADAD3356D9C |
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persistent identifier |
https://treatment.plazi.org/id/03A587B4-E535-AC09-FBF8-D629FB9E17DF |
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treatment provided by |
Felipe |
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scientific name |
Eobranisamys sp. |
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Figure 5.15 View FIGURE 5 -16, Appendix 3
2016 Caviomorpha indet. Antoine et al., Supplementary data, p. 8.
2017 Caviomorpha indet. Antoine et al., Supplementary data, p. 9.
Referred material. MUSM 2841, fragmentary left upper molar? ( Figure 5.15 View FIGURE 5 ); MUSM 2842, fragmentary left upper molar ( Figure 5.16 View FIGURE 5 ).
Locality. Contamana CTA-66, Loreto Department, Peru.
Formation and age. Pozo Formation, lower member, late middle Eocene ( Antoine et al., 2016).
Description. MUSM 2841 ( Figure 5.15 View FIGURE 5 ) could be a fragment of an upper molar, upon which it can be recognized a part of the anteroloph, the protoloph, the mure, the third transverse crest, and a mesial part of the anterior arm of the hypocone. The crests are very thick. The lingual protoloph is reduced to a short crestule, stemming from the labial branch of the protoloph and forwardly directed, but without connection with the protocone (pseudo-taeniodont pattern). The paracone displays short anterior and posterior arms connecting to the labial end of the anteroloph and the posterior arm of the mesostyle, respectively, thereby involving the labial closure of both the paraflexus and mesoflexus. The protoloph runs from the paracone to an oblique mure. The third transverse crest, labially linked to a strong mesostyle, is thin at the level of its lingual connection with the anterior arm of the hypocone. Such a pattern suggests that the third transverse crest corresponds to a long mesoloph, and possibly to a very short mesolophule lingually. The protoloph and third transverse crest are roughly parallel and slightly oblique.
MUSM 2842 ( Figure 5.16 View FIGURE 5 ) is a labiodistal fragment of a medium-sized upper molar, upon which it can be easily recognized labially, the mesostyle and metacone, and distolingually, the hypocone. The mesostyle is particularly strong, appearing as large as the metacone and hypocone. The mesostyle is separate from the metacone by a narrow but deep notch, while the metacone is strongly connected to the posteroloph. The third transverse crest is strong, straight, and well-connected to the mesostyle, but it is distinct from the mesial end of the anterior arm of the hypocone. This pattern suggests that it is only formed by a mesoloph. The metaloph is well-defined, long, and well-curved. It runs lingually from the metacone, then turns backwardly and connects to an accessory cusp of the posteroloph mediolingually (just below the middle line of the crown). The metaloph, mesoloph, and posteroloph remain well-separated. The hypocone displays a very long and oblique anterior arm. The posteroloph is strong and gently curved. The flexi are deep. The most posterior flexus (labial part of the posteroflexus) is entirely closed and forms a deep and oval posterofossette.
Comparisons. On MUSM 2842 ( Figure 5.16 View FIGURE 5 ), the presence of a strong and non-oblique third transverse crest, as well as a well-defined, long, and curved backwardly metaloph, which is lingually connected to the posteroloph, in addition to the brachydonty, are characters found in three Paleogene genera: Cachiyacuy , Eosallamys Frailey and Campbell, 2004 , and Eobranisamys . In Cachiyacuy and Eosallamys , the development and connections of the metaloph are highly variable. The metaloph can be long, reduced, or almost absent. It is totally absent on two upper molars of Cachiyacuy : on MUSM 2744 of C. contamanensis and on MUSM 2785 of C. kummeli ( Figure 4.12 View FIGURE 4 ). When it is present in Cachiyacuy and Eosallamys , it can be connected either to the anterior arm of the hypocone, to the third transverse crest, or to the posteroloph. In Eobranisamys , the metaloph is present, well-defined, well-separated from its adjacent mesial and distal transverse crests (third transverse crest and posteroloph, respectively), and it is always connected to the posteroloph. As for MUSM 2842, the mesostyle is always labially separate from the metacone in Eosallamys and Eobranisamys , while in Cachiyacuy , these two cusps can be linked. On MUSM 2842, the development and configuration of the metaloph generate a large, deep, and rounded posterofossette (labial part of the posteroflexus), a feature characteristic of Eobranisamys . In C. contamanensis and Eosallamys , this posterofossette is smaller and shallower. This fragmentary tooth from CTA-66 is therefore likely to be the distal part of an upper molar of an Eobranisamys -like taxon. The size of the specimens is closer to the species of Eobranisamys from CTA-27 ( E. javierpradoi ) and Eobranisamys riverai than to Eobranisamys romeropittmanae . On MUSM 2842, as for E. romeropittmanae and E. riverai , the posterofossette is larger than in E. javierpradoi . As for E. javierpradoi, MUSM 2842 differs from E. romeropittmanae and E. riverai in showing sharper crests and more salient cusps.
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