Miocene Macroflora Research Articles

The first fossil record of a giant horsetail (Equisetum, Equisetaceae) is from the Miocene of Patagonia, Argentina

A Miocene macroflora recovered from Ñirihuau Formation sediments exposed at Quebrada Vera site in northwesterern Patagonia, Argentina, is recorded and described for the first time. The assemblage is composed exclusively of free-sporing plants, mainly by Equisetum remains with subordinate occurrences of four fern morphotypes (represented by bi-, tri- and pinnate fronds). Equisetum imprints and molds include distinctive jointed stems with whorls of linear and basally fused leaves, numerous scars of lateral branches arranged in a radially symmetrical pattern situated at the nodes, and nodal diaphragms of up to 4 cm in diameter. The large size and regular branching of the stems link the fossils to the South American giant members of the genus and they probably represent a new fossil species. This is the first conclusive fossil record of a giant Equisetum worldwide, and consequently, it is biogeographically and evolutionarily relevant. The new findings attest that members of the giant horsetail clade were components of the Patagonian vegetation in the Miocene, implying that the age of the clade must predate that estimated from morphological and/or molecular data. The plant fossil assemblage represents part of a wetland community probably growing close to a riverside or lakeshore in coincidence with previous sedimentological estimates.

Deuxième complément à l'inventaire de la macroflore du Miocène Supérieur de la diatomite de Murat (Cantal, Massif Central, France)

Le gisement de diatomite de Murat (Cantal), daté à la limite Mio-Pliocène (Messinien), est particulièrement riche en végétaux fossiles. De nouvelles prospections effectuées de 2010 à 2019 ont permis de compléter les inventaires précédents. Seules cinq nouvelles formes fossiles ont été découvertes et sont décrites : trois nouvelles espèces (1 Filicophyte et 2 Magnoliophytes) et deux formes fossiles d'aiguilles de pin (Pinus sp., Coniferophytes). Deux autres espèces précédemment citées sont détaillées et figurées. Le nombre total d'espèces décrites dans la diatomite de Murat est maintenant de 86 : 4 Filicophytes, 11 Coniferophytes et 71 Magnoliophytes. La diatomite de Murat reste donc l'un des plus riches gisements de végétaux fossiles miocènes du Massif central. La flore est dominée par des espèces tempérées, mais des espèces plus froides et des espèces thermophiles sont aussi présentes.

The Miocene macroflora of the northern Ogallala Group, northern Nebraska and southern South Dakota

The results of the first comprehensive paleobotanical survey of the northern portion of the late Miocene Ogallala Group are discussed. Several species of fossilized fruiting structures from vascular plants (Berriochloa, Celtis, Cryptantha, Biorbia, Lithospermum, Eleofimbris, Carex,andCyperocarpus) in the mid- to late-Miocene are reported. Fewer taxa (12 genera) were found in the South Dakota-northern Nebraska area than have been reported previously (20 genera) from southern Nebraska-Kansas strata in the same formations and approximately the same area of exposures. Sites of Barstovian age near the Kilgore Flora site indicate that grasses were commonly found in the region. The results presented here support the hypothesis that grassland savanna vegetation was widely distributed in the northern Great Plains by the Clarendonian age.

The late Miocene macroflora of the La Cerdanya Basin (Eastern Pyrenees, Spain): towards a synthesis

The late Miocene macroflora of the La Cerdanya Basin (Eastern Pyrenees, Spain): towards a synthesis