Smilodon populator Lund, 1842

Manzuetti, Aldo, Perea, Daniel, Jones, Washington, Ubilla, Martın & Rinderknecht, Andres, 2020, An extremely large saber-tooth cat skull from Uruguay (late Pleistocene - early Holocene, Dolores Formation): body size and paleobiological implications, Alcheringa: an Australian Journal of Paleontology 44, pp. 1-8 : 3-4

Smilodon populator Lund, 1842

Referred material. MNHN-P 957 , almost complete skull ( Fig. 2).

Geographic and stratigraphic location. Limetas Creek (Department of Colonia, Uruguay), Dolores Formation, late Pleistocene–early Holocene .

Comparative description. Dorsal view: elongated and rather narrow skull, according to the disposition of the zygomatic arches. There is an opening in the frontonasal region of the skull. Lateral view: the nasals are high and the large lambdoid crest forms a marked angle where it meets the mastoid process as evidenced in Smilodon populator and differing from S. fatalis ( Kurten & Werdelin 1990) . Ventral view: enlarged mastoid process; anteroposteriorly elongated and transversely compressed auditory bullae.

The tooth rows are very well preserved but lacking M1; canines are cracked and broken. The incisors are slightly recurved posteriorly, the PM3 is tricuspidate and slightly oblique with respect to the corresponding PM4. The PM4 is secodont and has the typical configuration of the genus ( Berta 1987), the secondary ectoparastyle is anterior to the parastyle, and the protocone is reduced. Judging from the degree of wear of the teeth, specially PM4, and the level of fusion of the cranial sutures, the specimen MNHN-P 957 is from an adult individual.

Remarks. The body mass estimations, using equations for extant felids based on measurements of the skull, provide an average value above 400 kg ( Table 1). Based on that average body mass, the typical prey size must have greatly exceeded 1 t, and the maximum prey size was around 3 t ( Table 2). Bivariate analysis based on measurements of the skull and dentition ( Figs 3 and 4) shows significant differences between Smilodon gracilis and S. fatalis , and in some ways with S. populator too. In terms of absolute size, the specimen MNHN-P 957 is larger than S. gracilis ( Berta 1987, 1995), S. fatalis ( Merriam & Stock 1932, Kurten & Werdelin 1990) and even the sample of specimens of S. populator used here ( Figs 3 and 4A) (Mendez-Alzola 1941, Churcher 1967, Kurten & Werdelin 1990). The only exception is the biplot of the PM4, which falls within the size variability of the largest S. fatalis and S. populator ( Fig. 4B ).

Measurements (in mm). Skull measurements: TL, 392; CBL, 379; OOL, 242; ZW, 240; RW, 119; IOW, 112; PCW, 100; GBM, 152; GBC, 83; FMB, 35; FMH, 32. Dental measurements (right side): TRL I-PM4, 168; Diast, 22; CAP, 52; CML, 24; PM3AP, 19; PM3ML, 12; PM4AP, 44; PM4ML, 18.

Figures

Figure 3. Bivariate graphs for the Smilodon populator specimen MNHN-P 957. A, zygomatic width (ZW) versus condylobasal length (CBL); B, canine transverse diam- eter (CML) versus canine anteroposterior diameter (CAP). Data from different sources (see Material and methods).

Fig. 4. Bivariate graphs for the Smilodon populator specimen MNHN-P 957. A, PM3 transverse diameter (PM3ML) versus PM3 anteroposterior diameter (PM3AP); B, PM4 transverse diameter (PM4ML) versus PM4 anteroposterior diameter (PM4AP). Data from different sources (see Material and methods).