New leontiniid Notoungulata (Mammalia) from Chile and Argentina : comparative anatomy, character analysis, and phylogenetic hypotheses

Related Titles

Series: American Museum novitates, no. 3737

By

Shockey, Bruce J.
Flynn, John J. (John Joseph), 1955-
Croft, Darin A.
Gans, Phillip B., 1956-
Wyss, André R.

Type

Book

Material

Published material

Publication info

[New York], American Museum of Natural History, c2012

Notes

Caption title.

"February 29, 2012."

Herein we describe and name two new species of leontiniid notoungulates, one being the first known from Chile, the other from the Deseadan South American Land Mammal Age (SALMA) of Patagonia, Argentina. The Chilean leontiniid is from the lower horizons of the Cura-Mallin Formation (Tcm₁) at Laguna del Laja in the Andean Main Range of central Chile. This new species, Colpodon antucoensis, is distinguishable from Patagonian species of Colpodon by way of its smaller I2; larger I3 and P1; sharper, V-shaped snout; and squarer upper premolars. The holotype came from a horizon that is constrained below and above by [superscript 40]Ar/[superscript 39]Ar ages of 19.53 ± 0.60 and 19.25 ± 1.22, respectively, suggesting an age of roughly 19.5 Ma, or a little older (~19.8 Ma) when corrected for a revised age of the Fish Canyon Tuff standard. Either age is slightly younger than ages reported for the Colhuehuapian SALMA fauna at the Gran Barranca. Taxa from the locality of the holotype of C. antucoensis are few, but they (e.g., the mylodontid sloth, Nematherium, and a lagostomine chinchillid) also suggest a post-Colhuehuapian faunal age. The second leontiniid named in this paper has been known in the literature for over 75 years as Leontinia sp. Several specimens referable to this species were discovered at Pico Truncado (Deseadan SALMA) during the Field Museum's first Marshall Field Expedition, led by Elmer Riggs in 1924. This "new" taxon, Elmerriggsia fieldia, is a small-bodied leontiniid, possessing grooved premolar protocones that lack intermediate lingual cingulae, but have well-developed labial cingulids on their lower molars. This new taxon is fairly common at Pico Truncado, in Santa Cruz, Argentina, but we have not encountered it at other localities.... Other findings of this work include a northerly extension of the geographical range of Colpodon and a possible temporal extension beyond the Colhuehuapian SALMA. It appears that the fauna at Laguna del Laja is an important source of information regarding the faunal transition that occurred between Colhuehuapian and Santacrucian SALMA faunas.

Subjects

Argentina , Chile , Colpodon autocoensis , Elmerriggsia fieldia , Laja Lagoon , Leontiniidae , Miocene , Notoungulata , Oligocene , Paleontology , Phylogeny , Santa Cruz (Province)

Call Number

QL1 .A436 no.3737 2012

Language

English

Identifiers

OCLC: 778891238