Orome deepi, Bauzá & Gelfo & López, 2019

Bauzá, Nicolás, Gelfo, Javier N. & López, Guillermo M., 2019, Early steps in the radiation of notoungulate mammals in southern South America: A new henricosborniid from the Eocene of Patagonia, Acta Palaeontologica Polonica 64 (3), pp. 597-607 : 600-601

Orome deepi sp. nov.

Fig. 3 .

ZooBank LSID: urn:lsid:zoobank.org:act:BCE56DA5-4984-4452-B9F2-1197BD865176

Etymology: Named after the British rock band Deep Purple, and in allusion to Las Violetas Farm, the locality in which the holotype was found (Spanish violeta, purple).

Holotype: MLP-90-II-5-1631, fragment of left maxilla with dP4–M1 Fig. 3 ).

Type locality: Las Violetas Farm locality (45°02’00.3”S 66°59’25.6”W), Chubut Province, Argentina .

Type horizon: Ypresian, early Eocene, Las Flores Formation, Río Chico Group, Itaboraian SALMA (sensu Woodburne et. al. 2014).

Material.— MLP-90-II-5-1632, fragment of left maxilla with M1–M2; MLP-90-II-5-1633, fragment of right maxilla with M1–M2; and MLP-90-II-5-1634, fragment of right maxilla with M1–M2 from type locality and horizon. MLP-79-I-5-47, isolated right M3; MLP-90-II-5-1635, isolated left M1; MLP-90-II-5-1636, isolated left M1, MLP-90-II-5-1637, fragment of left maxilla with broken P4, M1 and M2; and MLP-90-II-5-1638, fragment of left maxilla with broken M1 and M2, from Las Flores locality, Chubut Province, Argentina; Ypresian (early Eocene), Las Flores Formation Río Chico Group ), Itaboraian SALMA .

Diagnosis.—Medium-sized henricosborniid (see dimensions in Table 1) comparable to Simpsonotus praecursor in size. Molars with metacone column weaker than in Henricosbornia , but stronger than in Notostylops . The middle portion of the ectoloph is slightly convex to straight in occlusal view. M3 with metaloph longer than other henricosborniids, reaching the protocone.

Description.—The dP4 (MLP-90-II-5-1631; Fig. 3 ) presents an advanced wear and, in occlusal view, is trapezoidal in shape and molarized. The protocone and the hypocone are joined at the base and originating a central fossa open lingually. As a result of wear, the crochet reaches the protoloph and the distolabial fossette is shallow and oval in outline. In labial view the ectoloph is bulbous, curved inwards in the medial region and shows parastyle paracone and metacone columns well developed. The mesial and distal cinguli are weak.

The M1 (MLP-90-II-5-1631) shows a pattern similar to dP4, but, in contrast, the ectoloph is only slightly curved in the mesostyle region, with a strong parastyle that is projected mesially over the preceding tooth, and a weaker metastyle. Both the paracone and metacone column are identifiable in the labial side of the ectoloph, but the metacone is significantly weaker. There is a short basal shelf between these columns as remnant of a labial cingulum. The crochet is long, contacting with the medial portion of the ectoloph, and isolating a distolabial fossette. The mesial and distal cinguli are strong and well developed. Even though MLP-90-II-5-1631 is a juvenile specimen, the M1, being part of the definitive dentition, contains the same information as in adult specimens (or even more, given the great degree of conservation). The M 1 in MLP-90-II-5-1633 ( Fig. 4C ) is heavily worn, making the outline very rounded, and in the crown only the crochet is distinguishable. MLP-90-II-5-1634 ( Fig. 4A ) is less worn out than MLP-90-II-5-1633, but the M1 is only preserved from crochet to lingual end. MLP-90-II-5-1635 ( Fig. 4G ) and MLP-90-II-5-1636 ( Fig. 4E ) are well preserved, with the features of the genus easily noticeable. The crown in MLP-90-II-5-1635 presents a unified surface between protoloph, metaloph, and crochet, similar to the dP 4 in MLP-90-II-5-1631. MLP-90-II-5-1637 ( Fig. 4D ) and MLP-90-II-5-1638 ( Fig. 4F ) are as worn out as MLP-90-II-5-1633, being only recognizable by size and the morphology of the ectoloph.

The M2 (MLP-90-II-5-1632; Fig. 4B ) follows the same pattern as dP4 and M1, differing in the weaker development of the metacone column in the ectoloph. MLP-90-II-5-1634 ( Fig. 4C ) presents a M2 with a wider crochet that is confluent with the ectoloph. The distolabial fossette is also wider.

The M3 (MLP-79-I-5-47; Fig. 4H ) is a triangular shaped tooth. The distinction between the metacone and metastyle is not clear. As in the M2, the metacone column is poorly developed. The long crochet reaches the vertex where ectoloph and protoloph join together. The metaloph is also long, reaching the lingual limit of the protocone, but with a weak hypocone. The mesial and distal cinguli are strongly developed, the first being longer.

Stratigraphic and geographic range.—Ypresian (early Eocene), Las Flores Formation, Río Chico Group, Itaboraian SALMA. Patagonia outcrops in Chubut Province, Argentina.

Figures

Fig. 3. Holotype of notoungulate mammal Orome deepi gen. et sp. nov. (MLP-90-II-5-1631) from the early Eocene of Las Violetas Farm, Argentina. Left dP4 and M1 in occlusal view.

Fig. 4. Notoungulate mammal Orome deepi gen. et sp. nov. from the early Eocene of Las Violetas Farm (A–C) and Las Flores (D–H), Argentina, all tooth in occlusal view. A. MLP-90-II-5-1633, fragment of right maxilla with M1–M2. B. MLP-90-II-5-1632, fragment of left maxilla with M1–M2. C. MLP- 90-II-5-1634, fragment of right maxilla with M1–M2. D. MLP-90-II-5-1637, fragment of left maxilla with broken P4, M1, and M2. E. MLP-90-II-5-1636, isolated left M1. F. MLP-90-II-5-1638, fragment of left maxilla with broken M1 and M2. G. MLP-90-II-5-1635, isolated left M1. H. MLP-79-I-5-47, isolated right M3. A, B, C, and H were horizontaly mirrored.