Mammalian tracks from Upper Cretaceous Yacoraite Formation in Argentina
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Ben Creisler
Jul 6, 2026, 12:34:59 AM (11 days ago) Jul 6
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Ben Creisler
A new paper:
Highlights
Mammalian tracks were collected from mixed epicontinental facies of Yacoraite Formation.
Valle del Tonco is one of the most important Maastrichtian ichnosites in the world.
The tracks are assigned to Brasilichnium cf. saltatorium.
The tracks represent the first record of mammalian origin for the Yacoraite Formation.
This new finding enriches the ichnological record of the Yacoraite Formation.
ABSTRACT
The Yacoraite Formation in northwestern Argentina hosts an abundant and diverse body- and ichnofossil record, the latter strictly related to an associated noteworthy record of microbialites, stromatolites, and sedimentary structures induced by microbial activity (MISS). The ichnological area is included in a carbonate and siliciclastic succession sedimented within an intracontinental rift-type basin in mainly shallow marine conditions. The ichnological record from this lithostratigraphic unit mainly comprises theropod, sauropod, pterosaur, and avian tracks. Here we report small footprints related to a mammalian producer, recently discovered from mixed grainstone-packstone intervals of the Caliza Amblayo Member of the Yacoraite Formation (Quebrada Sunchales Sur, Valle del Tonco, Salta province). The formation and preservation of the tracks were evidently controlled by the activity of microbial communities and the associated mat development. The new record consists of several, circular to semicircular tetradactyl footprints, with manus-pes impression set on one side of the body almost aligned laterally with those on the other side, which are assigned to Brasilichnium cf. saltatorium. As suggested by the spatial arrangement of sets, the proposed producer is a small, fast-moving, and possibly jumping mammal to be sought among those taxa described from the southern hemisphere. This material constitutes the first documented occurrence of mammalian tracks in the Yacoraite Formation, extends the stratigraphic distribution of Brasilichnium to the Maastrichtian, and expands our knowledge of the paleobiology of mammals from this period.
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Franco E. Migliaro Petroni, Paolo Citton, Gabriel R. López-Isla, Martina Caratelli, Sebastián Pernich, Geraldine Fischer & Silvina de Valais (2026)
First mammalian tracks from the Yacoraite Formation, Valle del Tonco, Salta province, Argentina
Journal of South American Earth Sciences 106179
doi: https://doi.org/10.1016/j.jsames.2026.106179
https://www.sciencedirect.com/science/article/abs/pii/S0895981126002312
First mammalian tracks from the Yacoraite Formation, Valle del Tonco, Salta province, Argentina
Journal of South American Earth Sciences 106179
doi: https://doi.org/10.1016/j.jsames.2026.106179
https://www.sciencedirect.com/science/article/abs/pii/S0895981126002312
Highlights
Mammalian tracks were collected from mixed epicontinental facies of Yacoraite Formation.
Valle del Tonco is one of the most important Maastrichtian ichnosites in the world.
The tracks are assigned to Brasilichnium cf. saltatorium.
The tracks represent the first record of mammalian origin for the Yacoraite Formation.
This new finding enriches the ichnological record of the Yacoraite Formation.
ABSTRACT
The Yacoraite Formation in northwestern Argentina hosts an abundant and diverse body- and ichnofossil record, the latter strictly related to an associated noteworthy record of microbialites, stromatolites, and sedimentary structures induced by microbial activity (MISS). The ichnological area is included in a carbonate and siliciclastic succession sedimented within an intracontinental rift-type basin in mainly shallow marine conditions. The ichnological record from this lithostratigraphic unit mainly comprises theropod, sauropod, pterosaur, and avian tracks. Here we report small footprints related to a mammalian producer, recently discovered from mixed grainstone-packstone intervals of the Caliza Amblayo Member of the Yacoraite Formation (Quebrada Sunchales Sur, Valle del Tonco, Salta province). The formation and preservation of the tracks were evidently controlled by the activity of microbial communities and the associated mat development. The new record consists of several, circular to semicircular tetradactyl footprints, with manus-pes impression set on one side of the body almost aligned laterally with those on the other side, which are assigned to Brasilichnium cf. saltatorium. As suggested by the spatial arrangement of sets, the proposed producer is a small, fast-moving, and possibly jumping mammal to be sought among those taxa described from the southern hemisphere. This material constitutes the first documented occurrence of mammalian tracks in the Yacoraite Formation, extends the stratigraphic distribution of Brasilichnium to the Maastrichtian, and expands our knowledge of the paleobiology of mammals from this period.
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