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The Early Eocene Climatic Optimum at the Lower Section of the Lumbrera Formation (Ypresian, Salta Province, Northwestern Argentina): Origin and Early Diversification of the Cingulata
Journal of Mammalian Evolution ( IF 1.9 ) Pub Date : 2021-05-10 , DOI: 10.1007/s10914-021-09545-w
Juan Carlos Fernicola , Ana N. Zimicz , Laura Chornogubsky , Mihai Ducea , Laura E. Cruz , Mariano Bond , Michelle Arnal , Magalí Cárdenas , Mercedes Fernández

Recently, the basal beds of the lower section of the Lumbrera Formation have been referred to the early Eocene (Ypresian) based on the identification of a succession of hyperthermal events globally dated between 52 and 55 Ma. Nevertheless, this section have also been referred to the middle Eocene (Lutetian) based on the ‘evolutionary stage’ of its fossil mammals. In this contribution, we present a new 238U-206Pb isochron age (46.2 Ma) obtained from samples taken on various independent points across paleosol and matrix positioned at the top of the lower section of the Lumbrera Formation. The new age is consistent with the hyperthermal scheme and constrains the deposition of the lower section of the Lumbrera Fm. between 55–46.2 Ma. In this new geochronological framework, we present one of the most ancient cingulate assemblages from America, recorded during the early Eocene hyperthermal. The specimens involved were recovered from the lowest levels of the lower section of the Lumbrera Formation at Los Cardones National Park, Calchaquí Valleys, Salta Province, Argentina. This cingulate assemblage is formed by the armadillos Pucatherium parvum, a species widely distributed in the Eocene of northwestern Argentina and a new taxon, Noatherium emilioi, gen. et sp. nov. In this new geochronological framework, the taxonomic composition and morphological variations observed in the two species described here and their probably contemporaneous Riostegotherium yanei from the Itaboraí basin (Brazil) support an early diversification of the Cingulata during the Paleocene, and reinforce an intertropical origin for the group.



中文翻译:

Lumbrera组下部(Ypresian,Salta省,阿根廷西北部)的始新世早期气候最佳:Cingulata的起源和早期多样性

最近,基于对全球52至55 Ma之间一系列高温事件的识别,将Lumbrera层下部的基床称为早期始新世(伊普尔人)。尽管如此,根据其化石哺乳动物的“演化阶段”,本节也被称为中始新世(鲁特田)。在这项贡献中,我们提出了一个新的238 U- 206铅等时年龄(46.2 Ma),取自在古土壤和位于Lumbrera组下部下部顶部的基质的各个独立点上采集的样品。新时代与高温方案相一致,并限制了Lumbrera Fm下部的沉积。55-46.2 Ma之间。在这个新的年代学框架中,我们提出了始于始新世高温的美国最古老的扣带状组合之一。所涉及的标本是从阿根廷萨尔塔省卡尔查奎谷地洛斯卡德内斯国家公园Lumbrera组下部最低层中回收的。这种有扣带的组合是由犰狳Pucatherium parvum形成的。是一种广泛分布在阿根廷西北部始新世的物种,也是一个新的分类群Noatherium emilioi gen。等 十一月 在这个新的年代学框架中,在这里描述的两个物种及其在伊塔博拉伊盆地(巴西)可能同时出现的亚里奥热亚种(Riostegotherium yanei)的分类学组成和形态变化,支持了古新世期间Cingulata的早期多样化,并加强了该热带的热带起源。团体。

更新日期:2021-05-10
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