Cachiyacuy cf. contamanensis
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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-E527-AC1F-FC7A-D1E8FEBA179F |
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treatment provided by |
Felipe |
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scientific name |
Cachiyacuy cf. contamanensis |
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Cachiyacuy cf. contamanensis , morph 2
Figure 6.7 View FIGURE 6 -12, Appendix 3
2016 Cachiyacuy cf. contamanensis Antoine et al. , p. 13 and Supplementary data, p. 9.
2017 Cachiyacuy cf. contamanensis Antoine et al. , Supplementary data, p. 9.
Referred material. MUSM 2823, fragment of a right dp4 or p4; MUSM 2825, left dp4 ( Figure 6.7 View FIGURE 6 ); MUSM 2826, fragmentary right m1; MUSM 2827, right m1 ( Figure 6.8 View FIGURE 6 ); MUSM 2828, right dP4 ( Figure 6.9 View FIGURE 6 ); MUSM 2829–2830, fragmentary right upper molars; MUSM 2831, left M1 ( Figure 6.10 View FIGURE 6 ); MUSM 2832, left M2 ( Figure 6.12 View FIGURE 6 ); MUSM 2563, right M2 ( Figure 6.11 View FIGURE 6 ).
Locality. Contamana CTA-29, Loreto Department, Peru.
Formation and age. Pozo Formation, lower member, late middle Eocene ( Antoine et al., 2016).
Description. The MUSM 2825 ( Figure 6.7 View FIGURE 6 ) is a complete but moderately worn dp4. It is pentalophodont and non-taeniodont. The curved metalophulid I and second transverse cristid are both lingually and labially linked to the metaconid and protoconid, respectively, these two cuspids being linguolabially opposed. The second transverse cristid corresponds to a long posterior arm of the protoconid, which connects to the metaconid (= metalophulid II). A well-developed and transverse mesolophid is lingually connected to a well-defined mesostylid and labially to the mesial ectolophid. The mesial ectolophid is slightly linguodistally extended, and it is not linked to the protoconid. There is a short and low distal ectolophid. The hypolophid is well-developed and slightly oblique due to the more mesial position of the entoconid with respect to the hypoconid. The lingual end of the posterolophid reaches the posterior arm of the entoconid. Only the anteroflexid and metaflexid are entirely closed, thereby forming an anterofossettid and a metafossettid, respectively.
Both specimens ( MUSM 2826 and 2827; Figure 6.8 View FIGURE 6 ) are m1s and are characterized by a trigonid slightly narrower than the talonid. They have a typical morphology of most pre-Deseadan caviomorphs, in being tetralophodont, non-taeniodont, and with a long second transverse cristid (unique or composite). On these two specimens, the second transverse cristid is complete and continuous, seemingly being only composed of a long posterior arm of the protoconid (= metalophulid II). MUSM 2826 differs from MUSM 2827 ( Figure 6.8 View FIGURE 6 ) in having a tiny cristulid extending between the metalophulid I and metalophulid II, and in lacking the connection between the metaconid and the mesostylid .
The dP4 (MUSM 2828; Figure 6.9 View FIGURE 6 ) is markedly eroded, notably in its lingual part, and its dental structure has been virtually erased. This tooth is trapezoidal with a lingual edge shorter than the labial one. The paracone is mesiolabially canted and strongly connected to the anteroloph. The protoloph is distolingually connected to the paracone, and is lingually complete, being connected distolabially to the protocone (absence of taeniodonty). Lingually, the hypocone displays a markedly oblique anterior arm that connects the protoloph mediolabially via a strong and oblique mure. Distolabially, the metacone is rather indistinct, being subsumed within the posteroloph. On the labial margin of the tooth, the mesostyle is faintly visible, but it displays a thin posterior arm, which reaches the anterior arm of the metacone. The third transverse crest and metaloph are short but well-defined, and they are lingually linked, thereby forming a V-shaped structure. The lingual base of this structure is connected to the mesial extremity of the anterior arm of the hypocone via a small crestule, which is interpreted here as a very short mesolophule. The labial branch of the third crest is in contrast interpreted as a mesoloph. Another tiny accessory crestule occurs distally, and links the lingual part of the posteroloph to the distal aspect of the anterior arm of the hypocone. All the flexi are entirely closed and they form fossettes except for the mesoflexus.
The upper molars ( Figure 6.10 View FIGURE 6 -12) are brachydont, primarily tetralophodont in appearance (anteroloph, protoloph, third transverse crest, and posteroloph; but see below concerning the presence of a metaloph), non-taeniodont, and somewhat transverse in occlusal outline (i.e., wider than long). The paracone is the highest and largest cusp of the crowns. The metacone is slightly more lingual in position and rather indistinct, being entirely subsumed within the posteroloph. In contrast, there is a strong and well-defined mesostyle between the paracone and the metacone. While a deep furrow separates the paracone from the mesostyle (mesoflexus open labially), the metacone is connected to the mesostyle via a well-marked anterior arm. However, tiny and shallow labial notches, absent on MUSM 2563 ( Figure 6.11 View FIGURE 6 ), tend to separate the metacone from both the mesostyle and posteroloph on MUSM 2831 ( Figure 6.10 View FIGURE 6 ). Lingually, the protocone is massive. It develops a strong and long posterior outgrowth, which runs distally and nearly closes the hypoflexus lingually (mesiodistal constriction of the hypoflexus). Contrary to MUSM 2832 ( Figure 6.12 View FIGURE 6 ), the lingual protoloph is composed of two crestules on MUSM 2831 ( Figure 6.10 View FIGURE 6 ): one stemming from the protocone and the other from the protoloph. The hypocone is smaller and slightly more labial in position. It displays a strong and oblique anterior arm, which continues its course mesially via a well-defined longitudinal or slightly oblique mure that links the protoloph in its lingual part. A trenchant third transverse crest extends linguolabially between the mesial extremity of the anterior arm of the hypocone and the mesostyle. It is parallel and close to the protoloph. On MUSM 2832 ( Figure 6.12 View FIGURE 6 ), the third transverse crest is slightly curved. It is strongly linked to the mesostyle. In contrast, it shows a lingual thinning on MUSM 2831, and is almost disconnected to the anterior arm of the hypocone on MUSM 2563 and 2832 (i.e., = mesoloph). On MUSM 2832, a secondary minute crestule, backwardly directed, is present on the distolingual wall of the mesoloph. The two least worn upper molars (MUSM 2831 and 2832) are tetra to pentalophodont because of a variable development of the metaloph-like crest, whereas on the more worn upper molar (MUSM 2563; Figure 6.11 View FIGURE 6 ), there is no metaloph but a tiny spur on the posteroloph, which is probably a relic of that loph. When present, the metaloph is lingually free. On all teeth, the labial end of the anteroloph reaches the base of the paracone and generates, with the protoloph, an oval-shaped, narrow and labiolingually developed anterofossette. On MUSM 2831 ( Figure 6.10 View FIGURE 6 ), there are two secondary longitudinal crestules within the anterofossette: one situated on the distal wall of the anteroloph and one situated on the mesial one of the protoloph.
Comparisons. The size and morphology of these teeth correspond to those of Cachiyacuy contamanensis . The dP4 is morphologically similar with the dP4s referred to C. contamanensis , notably in having the metaloph that reaches the third transverse crest lingually. Moreover, as for MUSM 2828 ( Figure 6.9 View FIGURE 6 ), many dP4s of C. contamanensis have a secondary longitudinal crestule stemming from the posteroloph. Like in Cachiyacuy , Canaanimys , and Eosallamys , the upper molars described here are subrectangular rather than subquadrate as in Eoespina / Eosachacui and? Vallehermosomys merlinae . On these CTA- 29 specimens, the development of the metaloph is highly variable (long, small, or almost absent), a variation which is found on the M1–2s of Cachiyacuy and Eosallamys . Like in Cachiyacuy , these upper molars from CTA-29 differ from those of Eosallamys in having more slender crests with a thinner enamel thickness. They also display a long posterior outgrowth of the protocone, which remains shorter than that observed in Canaanimys . The non-taeniodont pattern of these upper molars excludes affinities with Vallehermosomys mazzoni , Canaanimys , Eobranisamys , Branisamys , Eoincamys and Incamys ( Hoffstetter and Lavocat, 1970; Lavocat, 1976; Frailey and Campbell, 2004; Vucetich et al., 2010). Their brachydonty also contrasts with the higher crowned teeth characterizing Branisamys and Incamys . The pentalophodonty of the MUSM 2825 dp4 ( Figure 6.7 View FIGURE 6 ) excludes Eobranisamys and Branisamys . Compared with the dp4 of Canaanimys maquiensis (MUSM 1895; in Antoine et al., 2012, figure 2z), MUSM 2825 from CTA-29 does not have a lingual connection between the metaconid and mesostylid. This character is variable in dp4s of Cachiyacuy (i.e., presence or absence of that connection). In addition, on MUSM 2825, the protoconid is clearly separate from the mesial ectolophid like in Eosallamys simpsoni (as well as in Eobranisamys and Branisamys ). However, this character is not found in Cachiyacuy and Eosallamys paulacoutoi , while it is variable in Eoespina / Eosachacui . Given the very similar dimensions and morphological features of this dental material from CTA-29 with C. contamanensis , we provisionally assigned the latter to Cachiyacuy cf. contamanensis , morph 2. Because of the apparent larger size of this dental material form CTA-29 with respect to MUSM 2651–2653 from CTA-51 (attributed to Cachiyacuy cf. contamanensis , morph 1, see above) we refer these isolated teeth to as two different taxa.
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