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-E525-AC19-FC7A-D4A8FC4D133F |
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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 1
Figure 5.5-7 View FIGURE 5 View FIGURE 6 View FIGURE 7 , Appendix 3
2016 Cachiyacuy cf. contamanensis Antoine et al. , Supplementary data, p. 5.
2017 Cachiyacuy cf. contamanensis Antoine et al. , Supplementary data, p. 9.
Referred material. MUSM 2651, fragmentary right dp4 ( Figure 5.5 View FIGURE 5 ); MUSM 2652, left m1 ( Figure 5.6 View FIGURE 5 ); MUSM 2653, left m3 ( Figure 5.7 View FIGURE 5 ).
Locality. Contamana CTA-51, Loreto Department, Peru.
Formation and age. Pozo Formation, lower member, late middle Eocene ( Antoine et al., 2016).
Description. The dp4 (MUSM 2651; Figure 5.5 View FIGURE 5 ) is worn and broken labiomesially. Due to the fragmentary state of the tooth, only the lingual cuspids are preserved: a part of the metaconid, the mesostylid and the entoconid. The posterior arm of the metaconid is linked to a crestiform mesostylid. The second transverse cristid is divided into two independent parts: the lingual one is connected to the metaconid, and the labial one was probably linked to the protoconid (posterior arm of the protoconid). Its lingual part is oriented labiodistally. In the mesiocentral part of the tooth, the mesolophid appears discontinuous and limited to two parts: an accessory cuspid and a tiny spur of ectolophid. The accessory cuspid, situated between the second transverse cristid and the hypolophid, connects to the lingual part of the second transverse cristid. A tiny spur of the ectolophid runs labially and ends directly distolabially to the accessory cuspid. The entoconid is the highest and largest cuspid. The hypolophid is straight and transverse. The anterior arm of the hypoconid may be present. The labial part of the posterolophid is curved and does not reach the distal aspect of the entoconid, ending its course far away from this main lingual cuspid.
The m1 (MUSM 2652; Figure 5.6 View FIGURE 5 ) is nearly pristine. This tooth is subrectangular in occlusal outline, with a talonid slightly larger than the trigonid. It exhibits a tetralophodont pattern, characterized by strong and elevated cuspids and cristids. The metaconid, massive, crestiform and mesiolabially canted, is prominent over other cuspids. The protoconid, hypoconid, and entoconid are low, virtually equally sized, but the entoconid is the most cuspate cuspid, the others being more crestiform. The protoconid and hypoconid are mesiodistally opposed, but the hypoconid displays a long, narrow, and mesiolabially oriented outgrowth that widens the talonid. There is no anterocingulid. A strong and straight metalophulid I forms the mesial margin of the crown. This cristid strongly connects the metaconid to the protoconid, this latter being slightly more distal in position to the metaconid. The metaconid displays a long and strong posterior arm, which runs distally to reach a faintly visible mesostylid. This stylid is in fact entirely incorporated within the posterior arm of the metaconid. The second transverse cristid is the lowest cristid of the crown surface. It is straight and transversely continuous, and could be identified as a complete metalophulid II (but see description of the m3, hereafter). With this longitudinal cristid configuration, as well as the connection between the posterior arm of the metaconid and the mesostylid, the anteroflexid is lingually closed and forms an anterofossettid. A longitudinal and short enamel spur (accessory cristulid) occurs in the middle part of the second transverse cristid. It runs toward the metalophulid I, but does not connect to it. The ectolophid is oblique and links the distal aspect of the protoconid to the hypolophid. Distolingually, the entoconid displays short anterior and posterior arms. The anterior arm runs mesially but does not reach the mesostylid, thereby generating a well-marked and deep furrow that makes the mesoflexid open lingually. The entoconid and the hypoconid are labiolingually opposed, and linked by a strong and curved posterolophid that closes the metaflexid lingually (= metafossettid). Distolabially, the anterior arm of the hypoconid is complete but low in its middle part (grooved), and thus it appears composed of two cristulids: a mesial one stemming from the ectolophid and a distal one from the hypoconid). Within the metafossettid, there is a small accessory cuspid, located on the distal wall of the hypolophid. All flexids/fossettids are wide and deep.
The m3 (MUSM 2653; Figure 5.7 View FIGURE 5 ), despite having the distal part of its talonid labiolingually pinched, basically exhibits a similar dental pattern to that of m1. The mesostylid is better defined and separate from the posterior arm of the metaconid by a thin and shallow notch. On this tooth, the second transverse cristid appears continuous, but there is a disruption on its middle, which indicates that this transverse cristid is a combination of two cristids. Its lingual part seems to be a neomesolophid that runs labially from the mesostylid. The labial part of the second transverse cristid corresponds to the posterior arm of the protoconid. As on m1, there is an accessory longitudinal enamel cristulid, which is situated at the labial extremity of the short neomesolophid that runs toward the metalophulid I without connecting it. The labial part of the posterior arm of the protoconid also bears a short accessory cristulid, forwardly directed. Lingually, an accessory cuspid is also present on the mesoflexid, close to the mesostylid. However, there is no secondary cuspid on the metafossettid as it does on m1. Otherwise, this tooth also differs from m 1 in showing a weaker development of the anterior arm of the hypoconid, which appears composed of two cristulids, as on m1, but the latters are disconnected, thereby involving an incipient taeniodonty.
Comparisons. The three teeth have trenchant cristids but the latter are clearly thinner compared with Deseadan or Miocene caviomorph species. Basically, the occlusal pattern of the lower molars from CTA-51 is simply constructed and similar to that found in most of pre-Deseadan caviomorphs (i.e., brachydonty, tetralophodonty, and non-taeniodonty without oblique cristids). The specimens recall Cachiyacuy contamanensis by their size, although they are slightly smaller, and by some morphological characters. On the MUSM 2651 dp4 ( Figure 5.5 View FIGURE 5 ), the second transverse cristid is discontinuous with its lingual part distally directed, and the mesolophid is limited to a very short cuspid-like cristid. On the dp4 of Cachiyacuy kummeli , Eobranisamys , Eoespina , Eosachacui , Eosallamys simpsoni , Sallamys pascuali , Sallamys cf. pascuali , and Branisamys ( Hoffstetter and Lavocat, 1970; Lavocat, 1976; Frailey and Campbell, 2004; Shockey et al., 2009), the mesolophid is well-developed and labiolingually complete. On LACM 143451 ( Eosallamys paulacoutoi ; in Frailey and Campbell, 2004, p. 122), the mesolophid is reduced but appears as a well-defined cristulid still connected to the mesostylid. In Sallamys quispea Shockey et al., 2009 , the mesolophid is reduced and includes two cristulids: one stemming from the mesostylid (neomesolophid) and the other from the ectolophid (true mesolophid). In Canaanimys maquiensis , the mesolophid on dp4 is reduced to a short cuspid-like cristid, like in MUSM 2651. However, on MUSM 2651, there is a lingual part of the second transverse cristid, while this structure is absent on the dp4 of Canaanimys maquiensis (MUSM 1888; in Antoine et al., 2012, figure 2k). On the dp4 of C. contamanensis , the cristid arrangement in the trigonid is highly variable. In this species, the second transverse cristid and mesolophid of dp4s can be transversely complete but with a tendency to be divided and reduced (MUSM 2665, 2670, 2671, 2672, and 2673). One dp4 of C. contamanensis (MUSM 2670; Figure 4.5 View FIGURE 4 ) has a similar configuration to that found in MUSM 2651 (i.e., discontinuous second transverse cristid with its lingual part distally directed, and a mesolophid reduced to a cuspid-like cristid). In addition, in having a posterior arm of the metaconid high and strongly connected to the mesostylid, the MUSM 2651 dp4 is somewhat peculiar among the Paleogene taxa known, since this character is otherwise found only in C achiyacuy, Sallamys quispea and Sallamys cf. pascuali ( Shockey et al., 2009) . In C achiyacuy, this character is rather variable and only found on some dp4s (MUSM 2663, 2670 [ Figure 4.5 View FIGURE 4 ], 2669, and 2763–2765). Finally, on MUSM 2652 and 2653, the addition of accessory cristulids connected to the second transverse cristid can also be observed in some lower molars of C. contamanensis , Eobranisamys and Eosachacui . Contrary to the MUSM 2652 and 2653 molars ( Figure 5.6-7 View FIGURE 5 View FIGURE 6 View FIGURE 7 ), or the molars of C. contamanensis , in Eobranisamys and Eosachacui , these cristulids are shorter and absent on m3s. Lower molars from CTA-51 differ from those attributed to C. maquiensis (CTA-27) in having a high posterior arm of the metaconid and a continuous metalophulid I. In sum, due to the strong dental affinities, an attribution of these lower teeth from CTA-51 to Cachiyacuy contamanensis could by reasonable. However, given the small difference of size noticed, we attribute MUSM 2651, 2652, and 2653 to Cachiyacuy cf. contamanensis , morph 1.
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