A new Late Cretaceous crocodyliform from the western margin of Gondwana (La Rioja Province, Argentina)

LUCAS E. FIORELLI; JUÁN M. LEARDI; MARTÍN HECHENLEITNER; DIEGO POL; GIORGIO BASILICI; GERALD GRELLET-TINNER

CRETACEOUS RESEARCH (PRINT)

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2016 vol. 60 p. 194 - 209

0195-6671

TheCretaceous witnessed the greatest diversity of Gondwanan notosuchian crocodyliforms,which displayed high levels of diversity and a notable array of specializedforms that developed in different ecological niches. Among this diversity, theadvanced notosuchians are a clade of mid body sized forms which displays aremarkable abundance but is restricted to two lithological units from the LateCretaceous of South America, the Adamantina Formation in southeastern Braziland the Bajo de la Carpa Formation in Patagonia (Argentina). The onlyexceptions known so far were the Late Cretaceous Labidiosuchus from the MariliaFormation in Brazil and Yacarerani from the Cajones Formation in Bolivia. Hereinwe report a new Cretaceous crocodyliform, Llanosuchus tamaensis gen. nov. etsp. nov., found in the Los Llanos Formation (Campanian?) in northwesternArgentina (La Rioja Province). The small specimenincludes well preserved fragments of the cranium and mandible with an estimatedskull size of about 9 cm lengths. This crocodyliform shares several derivedcharacters with Notosuchus terrestris from the Bajo de la Carpa Formation(Patagonia) and it was found in a weakly developed sandy paleosol profile formedin wet local conditions but in a region characterized by semi-arid climate andactive eolian sedimentation. The presence of a new advanced notosuchian in the Cretaceousof western Gondwana, and its intermediate geographical region between the knownSouth American species (Brazil, Argentina and Bolivia), has interestingimplications, and adds another record of an advanced notosuchian in deposits withinferred warm climates and semi-arid paleoenvironments. Finally, Llanosuchustamaensis supports a Late Cretaceous age for Los Llanos Formation withimportant geological implications for La Rioja Province.