Geochronologic evidence of a large magmatic province in northern Patagonia encompassing the Permian-Triassic boundary

Luppo, Tomás; Luchi, Mónica G. López de; Rapalini, Augusto E.; Dopico, Carmen I. Martínez; Fanning, C. Mark

doi:10.1016/j.jsames.2018.01.003

Cited by 38 publications

(39 citation statements)

References 37 publications

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“…At the same time, the recent datations provided by Luppo et al (2017) contrast with the Late Triassic age historically proposed for the whole Vera Formation and in particular for the deposits bearing the ‘ Dicroidium ’ flora and the ichnogenus Dicynodontipus . On the basis of the new isotopic ages, Luppo et al (2017) concluded that at least some of the levels bearing the ‘ Dicroidium ’-type flora (Artabe, 1985a; Artabe, 1985b) are intercalated between deposits dated 252 ± 2 Ma (Changhsingian, Late Permian) and 248 ± 2 Ma (Olenekian, Early Triassic).…”

Section: Discussionmentioning

confidence: 75%

“…These new data predate the main volcanic activity to an about a 10 Ma period between the Late Permian and the Early Triassic, making the lower part of the Los Menucos Group coeval with the La Esperanza Plutono-Volcanic Complex (González et al, 2017; Luppo et al, 2017). …”

Section: Geological Settingmentioning

confidence: 76%

“…These authors also suggested that the stratigraphic position of the deposits exposed in the Tchering quarry, west of Los Menucos town, where Dicynodontipus ( sensu Melchor & de Valais, 2006) come from, is not yet completely clear. Nevertheless, this quarry is spatially close to the outcrops where geochronological data were provided by Luppo et al (2017). On the other hand, the Yancaqueo farm from which the Pentasauropus footprints come, is located east of Los Menucos town and lacks detailed geochronological and geological studies.…”

Section: Discussionmentioning

confidence: 94%

“…On the basis of the new isotopic ages, Luppo et al (2017) concluded that at least some of the levels bearing the ‘ Dicroidium ’-type flora (Artabe, 1985a; Artabe, 1985b) are intercalated between deposits dated 252 ± 2 Ma (Changhsingian, Late Permian) and 248 ± 2 Ma (Olenekian, Early Triassic). These authors also suggested that the stratigraphic position of the deposits exposed in the Tchering quarry, west of Los Menucos town, where Dicynodontipus ( sensu Melchor & de Valais, 2006) come from, is not yet completely clear.…”

Section: Discussionmentioning

confidence: 99%

“…More recent results indicated an age of 257 ± 2 Ma (Wuchiapingian, Late Permian) for a rhyolitic ignimbrite, 252 ± 2 Ma (Changhsingian, Late Permian) for an andesite, and 248 ± 2 Ma (Olenekian, Early Triassic) for a dacitic ignimbrite (Luppo et al, 2017) of the Los Menucos Group. These new data predate the main volcanic activity to an about a 10 Ma period between the Late Permian and the Early Triassic, making the lower part of the Los Menucos Group coeval with the La Esperanza Plutono-Volcanic Complex (González et al, 2017; Luppo et al, 2017).…”

Section: Geological Settingmentioning

confidence: 98%

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Triassic pentadactyl tracks from the Los Menucos Group (Río Negro province, Patagonia Argentina): possible constraints on the autopodial posture of Gondwanan trackmakers

Citton

Díaz-Martínez

Valais

et al. 2018

PeerJ

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The Los Menucos locality in Patagonia, Argentina, bears a well-known ichnofauna mostly documented by small therapsid footprints. Within this ichnofauna, large pentadactyl footprints are also represented but to date were relatively underinvestigated. These footprints are here analyzed and discussed based on palaeobiological indications (i.e., trackmaker identification). High resolution digital photogrammetry method was performed to achieve a more objective representation of footprint three-dimensional morphologies. The footprints under study are compared with Pentasauropus from the Upper Triassic lower Elliot Formation (Stormberg Group) of the Karoo Basin (Lesotho, southern Africa). Some track features suggest a therapsid-grade synapsid as the potential trackmaker, to be sought among anomodont dicynodonts (probably Kannemeyeriiformes). While the interpretation of limb posture in the producer of Pentasauropus tracks from the Los Menucos locality agrees with those described from the dicynodont body fossil record, the autopodial posture does not completely agree. The relative distance between the impression of the digital (ungual) bases and the distal edge of the pad trace characterizing the studied tracks likely indicates a subunguligrade foot posture (i.e., standing on the last and penultimate phalanges) in static stance, but plantiportal (i.e., the whole foot skeleton and related soft tissues are weight-bearing) during the dynamics of locomotion. The reconstructed posture might have implied an arched configuration of the articulated metapodials and at least of the proximal phalanges, as well as little movement capabilities of the metapodials. Usually, a subunguligrade-plantiportal autopod has been described for gigantic animals (over six hundreds kilograms of body weight) to obtain an efficient management of body weight. Nevertheless, this kind of autopod is described here for large but not gigantic animals, as the putative trackmakers of Pentasauropus were. This attribution implies that such an autopodial structure was promoted independently from the body size in the putative trackmakers. From an evolutionary point of view, subunguligrade-plantiportal autopods not necessarily must be related with an increase in body size, but rather the increase in body size requires a subunguligrade or unguligrade, plantiportal foot. Chronostratigraphically, Pentasauropus was reported from Upper Triassic deposits of South Africa and United States, and from late Middle Triassic and Upper Triassic deposits of Argentina. Based on the stratigraphic distribution of the ichnogenus currently accepted, a Late Triassic age is here proposed for the Pentasauropus-bearing levels of the Los Menucos Group.

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Section: Discussionmentioning

confidence: 75%

Section: Geological Settingmentioning

confidence: 76%