Sparassocynus

Autor:	Abello, Mar��a Alejandra, Reyes, Mart��n De Los, Candela, Adriana Magdalena, Pujos, Francois, Voglino, Dami��n, Quispe, Bernardino Mamani
Rok vydání:	2015
Předmět:	Sparassocynus Didelphidae Mammalia Animalia Biodiversity Didelphimorphia Chordata Taxonomy
DOI:	10.5281/zenodo.5613778
Popis:	�� Sparassocynus �� heterotopicus Villarroel & Marshall, 1983 Fig. 4, Tables 1��2 Holotype. MNHN-BOL- 011896, fragment of a left maxilar with M 1��3 (Fig. 4 A), fragment of a left mandible with m 2��4 (Fig. 4 B��C), and an edentulous right mandible with roots of c��m 4. Locality and Horizon. Locality of Umala, Department of La Paz, Bolivia. Umala Formation (Montehermosan, early Pliocene sensu Marshall et al., 1979). Comparative description. The general morphology of the dentition of S. heterotopicus shows characters common to diverse carnivorous didelphoids (Goin & Pardi��as, 1996: 351; Forasiepi et al., 2009); among them are the upper molars with long metacristae and small protocones, and lower molars with small talonids and strong paracristids. Upper molars of MNHN-BOL- 011896 (Fig. 4 A) have a stylar shelf narrower than that of didelphids and as wide as in sparassocynids. The StA is absent on M 1 and M 3 and reduced on M 2. On M 1 the StB is the largest stylar cusp (in section it is half of the size of paracone), the StD is smaller than StB and subdivided into two cusps; finally StE is low and poorly developed. On M 2 the StB is proportionally larger than on M 1 and, as in the M 1, StB is larger than StD; this latest is not subdivided and StE is missing. A reduced StB is present on M 3. In contrast to the extant compared Didelphidae (Lutrolina, Didelphis, Monodelphis, Thylamys, and Caluromys) and the extinct didelphids Thylatheridium, Thylophorops, and Hyperdidelphys, stylar cusps B and D are proportionally smaller. Compared to the Sparassocynidae, particularly Sparassocynus, the StB and StD are similarly developed, but MNHN-BOL- 011896 differs by having a subdivided StD on M 1. Regarding relative sizes between StB and StD on M 1��2, MNHN-BOL- 011896 is similar to the extinct didelphid Hyperdidelphis and sparassocynids in wich StB is larger than StD and differs from the extant compared didelphids, the extinct didelphid Thylophorops and Thylatheridium, by having a StB smaller than the StD. On M 1 the preparacrista is short and points towards the parastylar corner whereas on M 3 ends labially at the anterior base of the StB; on M 2 the labial end of the preparacrista could not be evaluated because of wear. In the morphology of the preparacrista of M 1, MNHN-BOL- 0 11896 differs from all compared taxa in which this crest joins the StB, excepting Didelphis, in which the preparacrista contacts the StA. On the other hand, the arrangement of the distal end of the preparacrista in the M 3 of Umala specimen is similar to that of the M 3 of Thylophorops, Hyperdidelphis parvula (Goin & Pardi��as, 1996), and all compared extant didelphids (except Didelphis); it also differs from the M 3 of sparassocynids and Thylatheridium in which this crest joins the StB. The postmetacrista is long, sharp, and oblique as in carnivorous didelphids (e.g., Lutreolina), but is slightly shorter than in sparassocynids (a long metacrista is a diagnostic character of the sparassocynids, Reig & Simpson, 1972, Goin, 1991). The metacone is large and the paracone is reduced as in other carnivorous forms (Forasiepi et al., 2009); despite both cusps are closer to each other than in didelphids, they are not fused as in sparassocynids (Reig & Simpson, 1972; Goin, 1991). The paracone is less reduced than the metacone compared to sparassocynids and didelphids. There is no evidence of para- and metaconule on M 1��2, but on the M 3 a small paraconule is present at the base of the paracone and the end of the preprotocrista. The protocone on M 1��3 has a small occlusal surface in relation to the total molar occlusal surface; in this proportion, protocones are smaller than those of didelphids and larger than in sparassocynids. Furthermore protocones in S. heterotopicus are eccentric, similarly to those in sparassocynids and some didelphids (e.g., Thylophorops and Hyperdidelphys). The ectoflexus is poorly developed in the M 1��2 and strongest in the M 3, as occurs, for example, in the sparassocynids and most didelphids (Voss & Jansa, 2009). The mandible of MNHN-BOL- 011896 is broken in front of the m 2 and has lost most of the coronoid and angular processes, as well as a portion of the condylar process. The horizontal ramus is shallow (see Table 2) and bears a strong labial scar for the masseteric muscle on its posterolateral surface; the masseteric fossa appears to have been deep as in Lutreolina. The articular condyle is transversely elongated and the angular processes acute and strongly inflected as is common among didelphids (Voss & Jansa, 2009). Lower dentition of MNHN-BOL- 0 11896 is partially preserved (Fig. 4 B��C). The metaconid, part of the protoconid of m 2, and the metaconid of m 4 are lost, so the morphology of the trigonid cusps (high and relative size) can be better described from those whole cusps of m 3. Similarly to some didelphids (e.g., Thylatheridium), the trigonid of the m 3 is higher than the talonid, but not as tall as it is in sparassocynids. The paraconid is a robust cusp (as in m 2 and m 4), similar to the metaconid in height, but quite larger in section. The metaconid is a small cusp located close to the protoconid resembling sparassocynids and, in less extent, Lutreolina among didelphids. A strong paracristid is developed along the protoconid and paraconid cusps; it is not straight (e.g., Monodelphis, Thylamys, and Didelphis) but forms an obtuse angle between the proximal (premetacristid) and distal (postparacristid) portions as occurs, for example, in sparassocynids, Thylatheridium and Lutreolina. The anterobasal cingulum of m 2��4 is narrow and it extends posteriorly up to the anterior wall of the protoconid. The talonids of m 2��4 are very shallow and have a smaller occlusal surface than trigonids; on m 2��3 talonids are short and narrow like in the sparassocynids (Figs. 2, 4B and 5 A; Table 2). In all molars the hypoconid projects slightly, not exceeding the labial wall of the protoconid. In the m 2 both cusps are equally projected but in the m 3 the hypoconid is placed more lingually than the protoconid, thus the talonid is narrower in the m 3 than in the m 2. In the m 4 the hypoconid is a small cusp positioned behind the posterior wall of the protoconid. The cristid obliqua is slightly oblique on m 2, and antero-posteriorly oriented on m 3��4. The entoconid is a poorly differentiated cusp on m 2��3 (better seen on m 2), and absent on m 4. The hypoconulid is smaller than the entoconid and positioned behind this cusp on m 2��3. The talonid of m 4 is relatively wider than in Sparassocynidae species and several didelphids such as Thylatheridium and Monodelphis. In contrast with these taxa, S. heterotopicus lacks a cingulum along the labial wall of the talonid bellow the hypoconid; in this regard, the talonid of m 4 of S. heterotopicus is similar to that in Lutreolina and Didelphis. Published as part of Abello, Mar��a Alejandra, Reyes, Mart��n De Los, Candela, Adriana Magdalena, Pujos, Francois, Voglino, Dami��n & Quispe, Bernardino Mamani, 2015, Description of a new species of Sparassocynus (Marsupialia: Didelphoidea: Sparassocynidae) from the late Miocene of Jujuy (Argentina) and taxonomic review of Sparassocynus heterotopicus from the Pliocene of Bolivia, pp. 147-160 in Zootaxa 3937 (1) on pages 156-157, DOI: 10.11646/zootaxa.3937.1.7, http://zenodo.org/record/241553 {"references":["Villarroel, C. & Marshall, L. G. (1983) Two new late Tertiary marsupials (Hathlyacyninae and Sparassocyninae) from the Bolivian Altiplano. Journal of Paleontology, 57 (5), 1061 - 1066.","Marshall, L. G., Butler, R. F., Drake, R. E., Curtis, G. H. & Tedford, R. H. (1979) Calibration of the Great American Interchange. Science, 204 (4390), 272 - 279. http: // dx. doi. org / 10.1126 / science. 204.4390.272","Goin, F. J. & Pardinas, U. F. J. (1996) Revision de las especies del genero Hyperdidelphys Ameghino, 1904 (Mammalia, Marsupialia, Didelphidae). Su significacion filogenetica, estratigrafica y adaptativa en el Neogeno del Cono Sur sudamericano. Estudios Geologicos, 52 (5 - 6), 327 - 359.","Forasiepi, A. M., Goin, F. J. & Martinelli, A. G. (2009) Contribution to the knowledge of the Sparassocynidae (Mammalia, Metatheria, Didelphoidea) with comments on the age of the Aisol Formation (Neogene), Mendoza Province, Argentina. Journal of Vertebrate Paleontology, 29 (4), 1252 - 1263. http: // dx. doi. org / 10.1671 / 039.029.0411","Reig, O. A. & Simpson, G. G. (1972) Sparassocynus (Marsupialia, Didelphidae), a peculiar mammal from the late Cenozoic of Argentina. Journal of Zoology, 167 (4), 511 - 539. http: // dx. doi. org / 10.1111 / j. 1469 - 7998.1972. tb 01742. x","Goin, F. J. (1991) Los Didelphoidea (Mammalia, Marsupialia) del Cenozoico Tardio de la Region Pampeana. Unpublished Ph. D dissertation, Universidad Nacional de La Plata, Facultad de Ciencias Naturales y Museo, La Plata, 327 pp.","Voss, R. S. & Jansa, S. A. (2009) Phylogenetic relationships and classification of didelphid marsupials, an extant radiation of new world metatherian mammals. Bulletin of the American Museum of Natural History, 322, 1 - 177. http: // dx. doi. org / 10.1206 / 322.1"]}
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