Friday, February 21, 2020

[PaleoMammalogy • 2020] Proclinodontomys dondasi • A New Echimyid Genus (Rodentia, Caviomorpha) in Central Argentina: Uncovered Diversity of A Brazilian Group of Mammals in the Pleistocene

Proclinodontomys dondasi 
Candela, Cenizo, Tassara, Rasia, Robinet, Muñoz, Valenzuela & Pardiñas, 2020

We describe a new extinct spiny ratProclinodontomys dondasi n. gen. n. sp. (Rodentia, Caviomorpha, Echimyidae), represented by a noteworthy preserved skull and mandible from the early-middle Pleistocene outcrops at the coastal cliffs of SE Buenos Aires Province (Central Argentina). Phylogenetic analyses allow us to propose that the new species described here and the already known Eurzygomatomys mordax (Winge) represent a new genus closely related to the living Euryzygomatomys spinosus and Clyomys laticeps. The new genus differs from Euryzygomatomys and Clyomys by having much more procumbent upper incisors, a more developed fossa for the M. temporalis, more flared and laterally expanded zygomatic arches, frontal less markedly expanded posteriorly, jugals much deeper anteriorly than posteriorly, with the dorsal border descending more abruptly posteriorly, smaller orbital cavity, and external auditory meatus relatively smaller and slanted upward and backward. Several features of the new species reflect a higher degree of adaptation to semifossorial habits than those of E. spinosus. The origin of the semifossorial ecomorphotype within echimyids may have been triggered by the expansion of relatively open and arid environments that arose near the Miocene-Pliocene boundary. The record of this new echimyid in Central Argentina indicates that during the early-middle Pleistocene, the southern limit of the geographic range of extinct representatives of the Brazilian lineage of semifossorial echimyids extended farther south than that of their living members.

Skulls of Echimyidae.
 (1–3) Proclinodontomys dondasi n. gen. n. sp. (MPH-P 0173, holotype) in dorsal (1), ventral (2), and lateral (3) views;
(4–6) P. mordax n. comb. (ZMUC 1/1845:13368) in dorsal (4), ventral (5), and lateral (6) views;
(7–9) E. spinosus (MACN 18103) in dorsal (7), ventral (8), and lateral (9) views.
Abbreviations: bs, basisphenoid; eam, external acoustic meatus; fm, foramen magnum; fr, frontal; I, incisive; if, incisive foramen; iof, infraorbital foramen; ipf, interpremaxillar foramen; ju, jugal; lps, lateral process of supraoccipital; M1, first molar; M2, second molar; M3, third molar; mx, maxilla; na, nasal; oc, occipital; pa, parietal; P4, fourth premolar; pl, palatine; pmx, premaxilla; sq, squamosal; tb, tympanic bulla. Scale bars = 10 mm.

Mandibles of Echimyidae. Left hemimandible of Proclinodontomys dondasi n. gen. n. sp. (MPH-P 0174) in lateral (1) and occlusal (2) views; right hemimandible (reversed) of E. spinosus (MACN 18103) in lateral (3) and occlusal (4) views.
Abbreviations: cp, coronoid process; mc, masseteric crest; m1, first molar; m2, second molar; m3, third molar; mn, masseteric notch; p4, fourth premolar. Scale bars = 10 mm.

Family Echimyidae Gray, 1825 
Subfamily Eumysopinae Rusconi, 1935 

Genus Proclinodontomys new genus 

Type species.—Proclinodontomys dondasi n. gen. n. sp. 
Other species.—Proclinodontomys mordax n. comb. (Winge, 1887).

Etymology.—From Greek pro = anterior, clino = inclination, odonto = tooth, mys = mouse; in reference to the fact that is a rodent with the front teeth inclined forward.

Proclinodontomys dondasi new species

Etymology.—The species name honors Alejandro Dondas (1948–2016), colleague and friend, tireless finder of fossils at the Atlantic cliffs of Buenos Aires Province and for many years head of the Paleontology Department of the Museo Municipal de Ciencias Naturales de Mar del Plata “Lorenzo Scaglia.” The specific epithet is formed from the surname “Dondas,” taken as a noun in the genitive case, plus the Latin suffix “i” (ICZN, 1999; Article 31.1.2).

Proclinodontomys mordax (Winge, 1887) new combination 
1887 Mesomys mordax Winge, p. 72, pl. 8, fig. 7. 
1946 Euryzygomatomys mordax (Winge); Paula-Couto, p. 5.

Adriana M. Candela, Marcos Cenizo, Daniel Tassara, Luciano L. Rasia, Céline Robinet, Nahuel A. Muñoz, Carola Cañón Valenzuela and Ulyses F. J. Pardiñas. 2020. A New Echimyid Genus (Rodentia, Caviomorpha) in Central Argentina: Uncovered Diversity of A Brazilian Group of Mammals in the Pleistocene. Journal of Paleontology. 94(1); 165–179. DOI: 10.1017/jpa.2019.73  

Hallaron una rata espinosa fósil de más de 400 mil años de antigüedad