Borhyaena Ameghino, 1887

Gaillard, Charlène, Forasiepi, Analía M., Tarquini, Sergio D., MacPhee, Ross D. E. & Ladevèze, Sandrine, 2024, Cranium of SipaloCYon externUS (Metatheria, Sparassodonta) with remarks on the paleoneurology of hathliacynids and insights into the Early Miocene sparassodonts of Patagonia, Argentina, Swiss Journal of Palaeontology (20) 143 (1), pp. 1-34 : 23

Borhyaena Ameghino, 1887

Type species. Borhyaena tuberata Ameghino, 1887

Borhyaena macrodonta Ameghino, 1887

( Fig. 10B–D )

Holotype. MACN 52-390 , incomplete cranium with associated right dentary and dentition (Additional file 1: Figure S 16), from Gran Barranca, Chubut Province, Patagonia, Argentina; Colhue Huapi Member, Sarmiento Formation, Early Miocene, Aquitanian, Colhuehuapian Age.

Referred specimen. MACN-Pv CH 40, fragmentary rostral portion of face, as well as associated symphyseal region of jaw, fragmentary canines, and associated m3–m4.

Occurrence. Sacanana, Chubut Province, Patagonia, Argentina; Sarmiento Formation, Early Miocene, Aquitanian, Colhuehuapian Age.

Description. Te specimen MACN-Pv CH 40 is not well preserved. Te fragmentary face consists of a symphyseal fragment of the lower jaw with partial left lower canine, fragment of right facial part of maxilla, and incomplete left upper canine. Te same concretion also contained two adjacent right lower molars (m3–m4) from the same individual.

Te dentaries are unfused at symphysis. In lateral view, the anterior border of dentaries is gently curved, differing from the straighter border of other Colhuehuapian borhyaenids such as Ar. sinclairi ( Forasiepi, 2009; Marshall, 1978) and other species (e.g., Australohyaena antiquua (Ameghino, 1894) ; Forasiepi et al., 2015). Tere is one mental foramen, preserved at the level of premolars, smaller than the rostralmost mental foramen of Ar. sinclairi MLP 85-VII-3-1.

Te upper and lower canines are large but not as robust as those of Ar. sinclairi ( Forasiepi, 2009; Marshall, 1978). Tere are shallow grooves at least on the accessible labial surface of the teeth, as seen in other borhyaenoids. Te left lower canine preserves its apical portion, which in addition to the reduced extralveolar exposure of the root, suggests that the specimen was a young adult (see discussion in Babot et al., 2022). Te m3–m4 are partially broken; minimum measurements (as the teeth are incomplete): length of m3, 13.5 mm; length of m4, 16.5 mm; and width of m4, 8.5 mm. Both molars have the protoconid as the dominant cusp followed by the paraconid. Te metaconid is a very small cusp in m3 and vestigial in m4 ( Fig. 10C–D ). Te m3 preserves some features of the talonid. Te hypoconulid is caudal to the metaconid. Te talonid extends as a cingular border on the medial side of the crown. On the labial side there is a postcingulid descending from the hypoconulid. Te postcingulid is incomplete in m3 and highly reduced in m4. In the latter, other structure of the talonid are absent.

Figures

Fig. 10 Dentition of A S.externus MACN-Pv CH1911, right upper postcanine dentition in occlusal view accompanied by line drawing,and B–D specimen MACN-Pv CH40 referred to B.macrodonta, corresponding to a fragmentary rostral portion of the face in lateral left view with upper canine and the tip of the lower canine (B), and a fragmentary right m3–m4 in lingual view (C) and occlusal view accompanied by line drawing (D). Scale bars represent 5 mm. ac anterior cingulum, ecg ectocingulum, efx ectoflexus, hyld hypoconulid, mc metacone, mcc postmetacrista, mcd metaconid, pac paracone,pacc preparacrista, pacd paraconid, past parastyle, pr protocone, prd protoconid