Boletín del Instituto de Fisiografía y Geología

ISSN 1666-115X

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Año 2026 - Volumen 94

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The lower Valanginian ammonite fauna of Puerta Quintuco, Argentina – with description of the new genus Quintucoceras
urn:lsid:zoobank.org:pub:7BC45593-2BB7-4DEC-885E-7CB68E722D64
 

Horacio Parent [parent@fceia.unr.edu.ar]: Laboratorio de Paleontología, IFG, Facultad de Ingeniería, Universidad Nacional de Rosario, Pellegrini 250, 2000 Rosario, Argentina.

Alberto C. Garrido [albertocarlosgarrido@gmail.com]: Museo Provincial de Ciencias Naturales “Prof. Dr. Juan A. Olsacher”, Dirección Provincial de Minería, Etcheluz y Ejército Argentino, Q8340AUB Zapala, Neuquén, Argentina. Centro de Investigación en Geociencias de la Patagonia – CIGPat, Departamento Geología y Petróleo, Facultad de Ingeniería, Universidad Nacional del Comahue, Buenos Aires 1400, Q8300IBX Neuquén, Argentina

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Abstract. In the Neuquén Basin (Argentina) occur several early Valanginian neocomitid ammonites that have been long assigned, provisionally to Thurmanniceras Cossmann, Neocomites Uhlig, or Pseudoblanfordia Spath. A new collection including adult and well-preserved ammonites from the uppermost Vaca Muerta and Quintuco formations in the type locality of this latter, Puerta Quintuco, is described in this paper. This new fauna, Wichmanni to Riveroi zones in age, shows that a large part of the mentioned neocomitids belong to a single evolving lineage here described as the new genus Quintucoceras [urn:lsid:zoobank.org:act:3B1A4573-81DF-4A7E-8E6A-1EC14F163968]. It is proposed that Lissonia branched from the new genus in the uppermost Wichmanni Zone. The new fauna also includes species of Lissonia, Subthurmannia Spath, Sarasinella Uhlig, and possibly Kilianella Uhlig, and Karakaschiceras Thieuloy.

  According to our lithostratigraphic interpretation, in the studied section the base of the Quintuco Fm in its type  locality is marked by the first appearance of a sandy level with tractive structures and intraclasts, strongly contrasting with the lutitic (black shale) domain succession that defines the underlying Vaca Muerta Fm. It is important to note that the lower levels of the Quintuco Fm as defined here are laterally correlated with the Huncal Member, included in the Vaca Muerta Fm by previous authors.

Key words. Neocomitidae, Quintucoceras n. gen., mosaic morphology, Lissonia, early Valanginian, Vaca Muerta
Formation, Quintuco Formation, Argentina.
 

Recibido 04/01/2026, Aceptado 14/03/2026, Disponible vía Internet 18/03/2026
 

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