Eremotherium laurillardi (Lund, 1842)

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

†cf. Eremotherium laurillardi (Lund, 1842)

Fig. 5

Referred material.

Remains of Eremotherium cf. E. laurillardi have been recovered at the Cauca site in bone groupings 2-6, with only groupings 3-5 being excavated (Fig. 1B ). Fourteen cranial and postcranial remains that include a right hemi-mandible (with mf 1 to 4), skull (with right Mf 1 to 5 and left Mf 2 to 4), right clavicle, right radius, presumably left navicular, cuneiform, IV left metatarsal, a worn element that we presume corresponds to a scaphoid, fragment of pelvis with acetabulum and part of the pubic ramus and five incomplete vertebrae, from excavation Cauca “B” (Fig. 4B ) and assigned to catalogue number AMU-CURS-1268. A probable right tibia (AMU-CURS-sn) and seven rib fragments were found in Cauca “D”. The other cranial and postcranial elements identified in Cauca “C” and unexcavated groupings 2 and 6 were not collected due to their poor state of preservation, being in some cases disintegrated (Fig. 3A-C ).

Descriptions.

The 14 disarticulated cranial and postcranial elements recovered in Cauca “B” most probably belong to the same individual (AMU-CURS-1268). The cranial material is composed of only the skull (AMU-CURS-1268a) (Fig. 5A1-A4 ) and the right hemi-mandible (AMU-CURS-1268b) (Fig. 5B1, B2 ). The skull has a Tl of 580 mm and preserves only the palatal section, since part of the cranial vault, nasal bones and part of the maxilla bones were destroyed by erosive processes. The palatal section is relatively well preserved, with both the right Mf1-Mf5 and the left series Mf2-4 and the alveolus of left Mf1 and Mf5. The hemi-mandible has a Tl of 450 mm, preserving the four molariforms mf1-mf4 (Fig. 5B2 ). This hemi-mandible has a convex ventral margin and projects downwards at the level of the first molars, forming a moderate mandibular protuberance. The molariforms preserved in the skull and hemi-mandible are of quadrangular section with crowns characterised by two transverse and parallel ridges, separated by a “V” -shaped valley. Measurements of the molariforms are presented in Table 2 . Associated with these cranial remains were recovered the right clavicle with a Tl of 240 mm (AMU-CURS-1268c; Fig. 5D1, D2 ), complete right radius with a Tl of 700 mm (AMU-CURS-1268d; Fig. 5C1-C3 ), presumably left navicular (AMU-CURS-1268e), cuneiform (AMU-CURS-1268f), IV left metatarsal (AMU-CURS-1268g; Fig. 5G ), a worn element that we presume corresponds to a scaphoid (AMU-CURS-1268h), fragment of pelvis with the acetabulum and part of the pubic ramus (AMU-CURS-1268i) and five incomplete vertebrae (AMU-CURS-1268j-n; Fig. 5E1-F ). Other small, fragmented and indeterminate bone elements were observed during the excavation and presumably could be associated with the same individual.

In Cauca “C”, only a few remains of postcranial elements of an Eremotherium , were found emerging on the surface. These were identified as vertebrae, ribs, pelvis fragments and other small indeterminate fragments. However, the poor state of preservation and disintegration in some cases, did not allow their recovery. Due to the proximity of these materials to the individual collected in Cauca “B”, a possible association amongst them is not ruled out here. In Cauca “D”, an association of seven fragments of ribs and a right tibia were recovered, also in a poor state of preservation (Fig. 4E ). This bone accumulation is located about 8 m north of the Cauca “B” individual, so a possible association with the latter would not be unlikely.

Bone grouping 2 (Fig. 1B ) was not excavated due to the partial or total disintegration in very little scraps of bones of the outcropping materials. However, a skull in a state of fragmentation (Fig. 3A ) still offers evidence that allows us to identify this association as a second specimen of Eremotherium . In bone grouping 6 (not excavated) to the northwest of Cauca “D”, a humerus of Eremotherium was also identified, but its poor state of preservation prevented collection or conservation in situ.

Remarks.

The ground sloth Eremotherium laurillardi distributed from south-eastern USA to Brazil, is the only species of the genus known from the Late Pleistocene in the Americas ( Cartelle and De Iuliis 1995). The taxonomic validity of Eremotherium rusconi Schaub, 1935, another species from the Late Pleistocene of South America, is questionable ( Cartelle and De Iuliis 1995; Faure et al. 2014; Cartelle et al. 2015).

Remains referable to Eremotherium are common and widely referred to in the Pleistocene fossil record of Venezuela (e.g. Schaub (1935); Simpson (1939); Nectario Maria (1941); Aguilera (2006); Carrillo-Briceño (2015); Carrillo-Briceño et al. (2016); Chávez-Aponte (2022) and references therein); specific taxonomic assignments of many of these specimens are still uncertain and should be clarified.

Remains assigned to cf. Eremotherium laurillardi have been reported in Venezuelan territory in palaeontological and archaeological sites ranging from sea level (e.g. Muaco, Taima-Taima and Cucuruchú; see Aguilera (2006); Carrillo-Briceño (2015); J.D.C.B pers. obs. (2022)), to mountain areas above 1200 m (e.g. El Vano; Jaimes et al. (2024b)).

The cranial and postcranial materials of Eremotherium collected from Cauca likely belong to an adult individual. The assignment of these specimens to the genus Eremotherium is based on the Hypsodontic index (HI) known for ground sloths. According to Bargo et al. (2006), HI is an element that is quantified by using the depth of the mandible (DM) (below the third molariform tooth) divided by the length of the molariform tooth row (LTR). In the right hemi-mandible collected in Cauca “B” (AMU-CURS-1268b), the DM is 140 mm and the LTR is 180 mm, with a resulting IH equal to 0.77, a value that coincides with Eremotherium whose range oscillates between 0.73 and 0.83 ( De Iuliis 1996; Bargo et al. 2006). Based on the taxonomic validity of the Late Pleistocene Eremotherium species suggested by Cartelle and De Iuliis (1995) and Cartelle et al. (2015), we tentatively suggest assigning the specimens collected at the Cauca site as cf. Eremotherium laurillardi .

† Mylodontidae Gill, 1872

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 5. Megatheres (A 1 - G) and mylodontids (H 1, H 2) from the Cauca site. A 1 - A 4. Skull of cf. Eremotherium laurillardi (AMU-CURS- 1268 a) in right lateral, ventral, posterior and anteroventral view; B 1, B 2. Right hemi-mandible (AMU-CURS- 1268 b) in right lateral view; C 1 - C 3. Right radius (AMU-CURS- 1268 d) in proximal, dorsal and distal view; D 1, D 2. Right clavicle (AMU-CURS- 1268 c); E 1, E 2. Thoracic vertebra (AMU-CURS- 1268 j) in anterior and left lateral view; F. Thoracic or lumbar vertebral centrum (AMU-CURS- 1268 k) in anterior view; G. Left IV metatarsal (AMU-CURS- 1268 g); H 1, H 2. cf. Mylodontidae, proximal and dorsal right radius (AMU-CURS- 1363). Abbreviations: (alv.) alveolus, (fm) foramen magnum, (mf) lower molariform, (Mf) upper molariform, (oc) occipital condyle.