Evolution of Small Mammal Communities during the Late Quaternary in a Middle-Altitude Valley of Northwestern Argentina

We document the first occurrence of Sigmodontinae (Mammalia, Rodentia, Cricetidae) from the Pliocene of northern South America, from the San Gregorio Formation of northwestern Venezuela. The recovered isolated molars are identified as Oligoryzomys sp. and Zygodontomys sp., two currently widespread sigmodontines in South America. These records constitute the oldest representatives of these genera, potentially new species, and the first Pliocene occurrence for Oryzomyini and the whole subfamily outside Argentina. Hypotheses on the historical biogeography of sigmodontines have been constructed almost exclusively using genetic data and the fossils we report provide a new kind of evidence. The occurrence of Oligoryzomys sp. and Zygodontomys sp. in Venezuela provides novel information for the diversification models suggested for Oligoryzomys , by supporting a potential eastern corridor of open environments from northern to southern South America. The presence of sigmodontines from the locality home of the new reports, Norte Casa Chiguaje, is consistent with the palaeoenvironmental conditions originally proposed for it based on mammals and botanical records, being characterized as mixed open grassland/forest areas surrounding permanent freshwater systems. The new sigmodontine evidence is used to discuss the putative scenarios of the ancient evolution of the subfamily in South America, favouring a model in which open areas (savannahs) to the east of the Andes played crucial role aiding or obstructing Late Miocene–Pliocene sigmodontine dispersion southwards.

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“…sp. [68,69,73]), Brazil (Lagoa Santa, Gruta do Urso, Pilger, Sangão, Deobaldino Marques and Garivaldino; O . flavescens , O .…”

Section: Discussionmentioning

confidence: 99%

“…Several additional Late Pleistocene occurrences are also known from Argentina (La Angostura and La Mesada localities; O. brendae and O. cf. O. occidentalis [69]), Brazil (Gruta do Urso, Toca da Boa Vista and Lapa dos Brejões; O. cf. O. mattogrossae, O. sp.…”

Section: Oligoryzomys and Zygodontomys: Palaeoenvironmental Significancementioning

confidence: 99%

Pliocene sigmodontine rodents (Mammalia: Cricetidae) in northernmost South America: test of biogeographic hypotheses and revised evolutionary scenarios

et al. 2023

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“…At the present, there are no mentions of vicunas for Tucumán (Vilá, 2005;Arzamendia et al, 2012) (Ortiz & Pardiñas, 2001;Ortiz & Jayat, 2007;Ortiz et al, 2019b), in which vegetation belts descended to lower altitudes and contracted following the settlement of more arid and cooler conditions associated to glacial pulses (Powell & Ortiz, 2014;Ortiz et al, 2019a, b). The record of V. vicugna, whose ecological requirements are well known, fit with this scheme and reinforces the evidence yielded by small mammals.…”

Section: Northwestern Argentinamentioning

confidence: 99%

“…Tafí del Valle Formation, late Pleistocene -early Holocene (Collantes et al, 1993;Collantes & Busnelli, 2014;Ortiz et al, 2019b).…”

Section: Vicugna Vicugnamentioning

confidence: 99%

“…According to the new taxonomic framework, most records of Vicugna vicugna in lowland areas are documented for the late Pleistocene and early Holocene, a span in which environments where drier and cooler than nowadays, including more xeric vegetation (Gasparini et al, 2017;Ortiz et al, 2019b). Temperate and more humid conditions towards the early Holocene lead to vegetation shifts, thus deeply affecting the range of V. vicugna, in contrast to the case of the less-specialized Lama guanicoe, currently still widely present in vast areas of Argentina (Weinstock et al, 2009).…”

Section: Northwestern Argentinamentioning

confidence: 99%

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The Fossil Record of Camelids (Mammalia, Cetartiodactyla) in Tucumán Province, Northwestern Argentina

2021

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Actualistic taphonomy of microvertebrates ingested by the barn owl (Tyto alba) in a forested area. Implications for the fossil record

Carolina Moreano Ortiz,

Ortiz,

Pia

et al. 2024

Geobios

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Evolution of Small Mammal Communities during the Late Quaternary in a Middle-Altitude Valley of Northwestern Argentina

Cited by 6 publications

References 66 publications

Pliocene sigmodontine rodents (Mammalia: Cricetidae) in northernmost South America: test of biogeographic hypotheses and revised evolutionary scenarios

Pliocene sigmodontine rodents (Mammalia: Cricetidae) in northernmost South America: test of biogeographic hypotheses and revised evolutionary scenarios

The Fossil Record of Camelids (Mammalia, Cetartiodactyla) in Tucumán Province, Northwestern Argentina

Actualistic taphonomy of microvertebrates ingested by the barn owl (Tyto alba) in a forested area. Implications for the fossil record

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