Notiomastodon platensis (Ameghino, 1888)

Carrillo-Briceno, Jorge Domingo, Ruiz-Ramoni, Damian, Sanchez, Rodolfo, Jaimes, Arturo, Chavez-Aponte, Edwin, Prevosti, Francisco Juan, Segura, Valentina, Carlini, Alfredo Armando, Garbe, Lisa, Tombret, Olivier, Zazzo, Antoine & Sanchez-Villagra, Marcelo Ricardo, 2024, Cauca: megafaunal and felid fossils (Mammalia) from a Pleistocene site in northwest Venezuela, Fossil Record 27 (1), pp. 187-207 : 187

† Notiomastodon platensis (Ameghino, 1888)

Fig. 7

Referred material.

A mandible (Fig. 7A1 ), the proximal part of a humerus and the distal end of the radius with what appears to be parts of very deteriorated carpals and metacarpals, all assigned as AMU-CURS-1269 and collected from Cauca “A” (Fig. 4A ). An isolated M2 (AMU-CURS-1045) collected about 5 m northwest of Cauca “C” (Fig. 1B ) and a complete and isolated tusk (AMU-CURS-1359) (Fig. 7C ) from Cauca “E” (Fig. 4C ). Other dental and postcranial fragments (see below) in a very poor state of preservation could not be collected.

Descriptions.

The mandible AMU-CURS-1269 (Fig. 7A1 ) preserves the complete right m2 (Fig. 7A1-A3, A5 ) and erupted m3 (Fig. 7A1, A4 ) and erupted left m2 and m3 in a fragmentary state (Fig. 7A1, A5 ). Part of the mandibular ramus and condylar processes are not preserved. The right m2 is a bunodont and trilophodont molar with a well-defined heel and cingulum (Fig. 7A2, A3 ); it is 150 mm in Tl. This molar presents a wear state of “3” (following Mothé et al. (2010)), which suggests that it could correspond to a subadult/adult individual. Abundant fragments referring to upper molars M2-M3 of the same individual were recovered on the mandibular remains (Fig. 3D ). A small portion of a tusk was also found a few centimetres from the specimen, which was not collected due to the high degree of disintegration. Of the postcranial remains associated with the lower jaw, the proximal part of a right humerus is only preserved in the posterior section and what appears to be the distal end of the radius with carpal and metacarpal fragments are in a very poor state of preservation.

The isolated tusk AMU-CURS-1359 (Fig. 7C ), whose position on the skull is undetermined, measures about 1700 mm long and could belong to an adult. It is curved, although it shows no apparent natural twist and lacks an enamel band. The tusk lies about 14 m north of the Cauca “A” site and its association with the jaw and the other elements is uncertain. Near the collection site of this tusk and on the surface, some fragmented and indeterminate postcranial bones were observed.

A few metres northeast of the Cauca “D” and “E” excavations, a tusk and bone fragments were found emerging on the surface. However, these were not collected due to the poor state of preservation (grouping 7; Fig. 1B ). In addition, small fragments of gomphotherid molars were scattered on the surface of the site, possibly because of transport by runoff. A possible upper left M2 (AMU-CURS-1045) not worn and with ~ 96 mm in Tl (Fig. 7B1, B2 ), was collected a few metres northeast of excavation “C”, suggesting the probable presence of a juvenile individual at the site. On the other hand, we do not have any evidence that allows us to associate the cranial and dental remains found in Cauca “A”, with the other gomphothere elements reported herein, resulting in an uncertain number of adult individuals present at the site.

Remarks.

In recent times, consensus has emerged suggesting the validity of only two genera of gomphothere in the southern continent, Cuvieronius hyodon Fischer, 1814 and Notiomastodon platensis (= Stegomastodon platensis ) (e.g. Mothé et al. (2012, 2013, 2017a); Alberdi and Prado (2022)). The stratigraphic and geographic distribution, as well as the diagnostic features that have been used to differentiate both genera, which are based on the skull and mandibular symphysis morphology and upper tusk and molars, are discussed in detail by Mothé et al. (2016, 2017a, 2017b), Alberdi and Prado (2022) and Carrillo-Briceño et al. (2023).

Based on the taxonomic differences mentioned above and used to differentiate both genera of gomphotheres in South America, we assigned the better-preserved specimens referred to in this section to N. platensis . This assignment is supported by: 1) the double to single clover wear pattern present in the right m2 of the AMU-CURS-1269 (Fig. 7A2 ), which resembles the pattern present in molars with advanced wear state in N. platensis (e.g. Mothé et al. (2012, 2013, 2017a) and references therein); 2) the robustness, curved shape and lack of twist and enamel bands in the tusk AMU-CURS-1359 (Fig. 7C ), which contrast with the shape and morphology of the C. hyodon tusk ( Mothé et al. 2012, 2013; Mothé and Avilla 2015); and 3) a jaw with no trace of lower tusks; meanwhile, C. hyodon presents a pair of lower incisors or its corresponding vestigial alveoli ( Mothé and Avilla 2015). By analogy, we believe the other remains of gomphotheres found at the Cauca site (e.g. tooth fragments and probably postcranial elements), and with a poor state of preservation (for example these from grouping 7) could also belong to N. platensis .

Abundant specimens of gomphotheres have been reported for several locations in the Falcón State and other sites in Venezuela ( Carrillo-Briceño et al. 2008a, 2008b; Chávez-Aponte et al. 2008; Carrillo-Briceño 2012, 2015); however, their taxonomic assignment should be re-evaluated. The gomphothere remains collected from the palaeontological/archaeological sites of Muaco, Taima-Taima and Cucuruchú in Falcón State, should be assigned to N. platensis (e.g. J.D.C.B., pers. obs. (2022)).

Perissodactyla Owen, 1848

Equidae Gray, 1821

Equus Linnaeus, 1758

Figures

Figure 1. Geographic location of the Cauca site (A) and the excavation area (B). The different bone groupings are referred to as " S " and the excavations as " A-E ". The M 2 isolated from a juvenile Notiomastodon platensis (AMU-CURS- 1045) is referred to with a triangle and *. Lithic artefacts referred to here are illustrated in Fig. 9.

Figure 3. Remains of fossil vertebrates emerging on the surface at the Cauca site. Skull (A), pelvis (B) and appendicular elements (C) of megatheriid Eremotherium. A, C. correspond to unexcavated S 2 (see Fig. 1 B). Upper molars (D) of gomphoteriid Notiomastodon platensis, with the root completely eroded, associated with the mandible AMU-CURS- 1269 from Cauca " A " (Fig. 1 B).

Figure 4. Excavations at the Cauca site. Cauca " A " (A), Cauca " B " (B), and Cauca " E " (C), showing the defence of Notiomastodon platensis (AMU-CURS- 1359) in situ. Mandible of N. platensis in plaster jacket in Cauca " A " (D). Cauca " D " with remains (tibia and ribs) of cf. Eremotherium laurillardi (E).

Figure 7. Notiomastodon platensis remains from Cauca site. A 1, A 5. Dorsal and anterodorsal views of the mandible (AMU-CURS- 1269); A 2, A 3. Occlusal and labial views of preserved right m 2 and (A 4), occlusal view of m 3; B 1, B 2. Occlusal and lateral view of M 2 (AMU-CURS- 1045). C. lateral view of tusk (AMU-CURS- 1359).