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Llanosuchus, new notosuchian from Late Cretaceous of Argentina



Ben Creisler
bcreisler@gmail.com

A new paper:



Lucas E. Fiorelli, Juan M. Leardi, E. Martín Hechenleitner, Diego Pol,
Giorgio Basilici & Gerald Grellet-Tinner (2016)
A new Late Cretaceous crocodyliform from the western margin of
Gondwana (La Rioja Province, Argentina).
Cretaceous Research 60: 194–209
doi:10.1016/j.cretres.2015.12.003
http://www.sciencedirect.com/science/article/pii/S0195667115301270


Highlights

We describe the first crocodyliform from the Late Cretaceous of La
Rioja province, NW Argentina.
Based on a phylogenetic analysis the new taxon represents an advanced
notosuchian and the first from Northern Argentina.
This new notosuchian has interesting paleobiogeographic and geological
implications for La Rioja and South America.

Abstract

The Cretaceous witnessed the greatest diversity of Gondwanan
notosuchian crocodyliforms, which displayed high levels of diversity
and a notable array of specialized forms that developed in different
ecological niches. Among this diversity, the advanced notosuchians are
a clade of mid body sized forms which displays a remarkable abundance
but is restricted to two lithological units from the Late Cretaceous
of South America, the Adamantina Formation in southeastern Brazil and
the Bajo de la Carpa Formation in Patagonia (Argentina). The only
exceptions known so far were the Late Cretaceous Labidiosuchus from
the Marilia Formation in Brazil and Yacarerani from the Cajones
Formation in Bolivia. Herein we report a new Cretaceous crocodyliform,
Llanosuchus tamaensis gen. nov. et sp. nov., found in the Los Llanos
Formation (Campanian?) in northwestern Argentina (La Rioja Province).
The small specimen includes well preserved fragments of the cranium
and mandible with an estimated skull size of about 9 cm lengths. This
crocodyliform shares several derived characters with Notosuchus
terrestris from the Bajo de la Carpa Formation (Patagonia) and it was
found in a weakly developed sandy paleosol profile formed in wet local
conditions but in a region characterized by semi-arid climate and
active eolian sedimentation. The presence of a new advanced
notosuchian in the Cretaceous of western Gondwana, and its
intermediate geographical region between the known South American
species (Brazil, Argentina and Bolivia), has interesting implications,
and adds another record of an advanced notosuchian in deposits with
inferred warm climates and semi-arid paleoenvironments. Finally,
Llanosuchus tamaensis supports a Late Cretaceous age for Los Llanos
Formation with important geological implications for La Rioja
Province.