Dryolestoids Diversified in South America, Dominant Mammals in Late Cretaceous

FIRST DRYOLESTOID (MAMMALIA, DRYOLESTOIDEA, MERIDIOLESTIDA) FROM THE CONIACIAN OF PATAGONIA AND NEW EVIDENCE ON THEIR EARLY RADIATION IN SOUTH AMERICA

Authors:

1. ANALÍA M. FORASIEPI (a,e)
2. RODOLFO A. CORIA (b,e)
3. JØRN HURUM (c)
4. PHILIP J. CURRIE (d)

Affiliations:

a. 1CONICET, Museo de Historia Natural de San Rafael, Parque Mariano Moreno s/nº, 5600 San Rafael, Argentina

b. CONICET, Subsecretaría de Cultura de Neuquén, Universidad Nacional de Río Negro y Museo Municipal “Carmen Funes”, Av. Córdoba 55, 8318 Plaza Huincul, Argentina.

c. Natural History Museum, University of Oslo, PO Box 1172, Blindern, NO-0318 Oslo, Norway.

d. Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada.

Abstract:

We report on a new dryolestoid (Mammalia, Dryolestoidea, Meridiolestida) from the Los Bastos Formation (Coniacian), Neu quén Province, Patagonia, Argentina, consisting of an edentulous left dentary (MCF-PVPH 412). The alveoli preserved suggest the presence of three incisors, one double-rooted canine, and six double-rooted postcanines (probably three premolars and three molars). Based on comparisons with previously known dentaries and isolated teeth, MCF-PVPH 412 would have been about the same size as Reigitherium Bonaparte. Among Dryolestoidea, MCF-PVPH 412 is assigned to Meridiolestida because there were probably three molars, the roots of the posterior molars are anteroposteriorly compressed, and there is no Meckelian groove. In addition, the penultimate lower premolar would be the largest in the tooth series, which is also true in other meridiolestidans. The position of the mandibular foramen, the probable presence of three premolars, and the outline of the posteroventral part of the jaw suggest affinities with the Mesungulatoidea (e.g., Coloniatherium Rougier, Forasiepi, Hill and Novaceck; Peligrotherium Bonaparte, Van Valen and Kramarz; and Reigitherium). The Coniacian specimen represents the oldest Mesungulatoidea and fills the gap in the record between the oldest South American dryolestoid (i.e., Cenomanian) and the better known Campanian–Maastrichtian taxa. The discovery of MCF-PVPH 412 in the Coniacian of Patagonia is consistent with the dryolestoid diversification during the Late Cretaceous that makes them the most abundant mammals during that period in South America.

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