''Mesodescolea'' is a genus of fossil foliage with uncertain affinities from the

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

of Argentina and Antarctica. It includes only one species, ''Mesodescolea plicata''.

Taxonomy

The genus was first erected by

Sergio Archangelsky Sergio Archangelsky (27 March 1931 – 10 July 2022) was an Argentine paleobotanist and palynologist. He was a pioneer of modern paleobotany in Argentina, as well as of cuticular morphology and ultrastructure. He was also a corresponding member o ...

based on material from the

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...

of the

Anfiteatro de Ticó formation The Anfiteatro de Ticó Formation is a geological formation from the Deseado Massif in the province of Santa Cruz, Argentina. Paleobiology The Anfiteatro de Ticó preserves a rich and diverse flora including macrofossils, mesofossils, and micro ...

. The name of the genus is dedicated to the naturalist Horacio Descole. Although it was originally compared to cycadalean genera such as '' Ctenis'' and ''

Stangeria ''Stangeria eriopus'' is a cycad endemic to southern Africa. It is the sole species in the genus ''Stangeria'', most closely related to the Australian genus ''Bowenia'', with which it forms the family Stangeriaceae. Description ''Stangeria eriop ...

'', its affinities were originally considered uncertain. Later reinvestigations and emendations cemented the view that ''Mesodescolea'' was a member of the

Cycadales Cycads are seed plants that typically have a stout and woody (ligneous) trunk with a crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants of a species are either male or ...

family

Stangeriaceae Stangeriaceae is the smallest family of the cycads, including only two extant genera, '' Stangeria'' and ''Bowenia'', which both have an underground stem. Taxonomy Although the family was first published by Schimper and Schenk as Stangerieae, t ...

. Other authors have proposed that the genus represents a member of the angiosperms with affinities with the ANA grade or

Chloranthaceae Chloranthaceae is a family of flowering plants (angiosperms), the only family in the order Chloranthales. It is not closely related to any other family of flowering plants, and is among the early-diverging lineages in the angiosperms. They are ...

Description

The genus includes leaves with highly lobed-dissected margins. The

venation Venation may refer to: * Venation (botany), the arrangement of veins in leaves * Wing venation, the arrangement of veins in insect wings See also * * Vernation Vernation (from ''vernal'' meaning ''spring'', since that is when leaves spring forth ...

is hierarchical, with the tertiary veins forming an irregular reticulum. Chloranthoid teeth are present in the margins. The

cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

shows laterocytic

stomata In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bor ...

, and is characterized by striae and perforated

idioblast An idioblast is an isolated plant cell that differs from neighboring tissues. They have various functions such as storage of reserves, excretory materials, pigments, and minerals. They could contain oil, latex, gum, resin, tannin or pigments etc. ...

Paleoecology

Leaves of ''Mesodescolea'' are locally abundant in the deposits of the

. They are found in association with ''

Ruflorinia ''Ruflorinia'' is a genus of fossilized foliage from the Early Cretaceous of Argentina assigned to the order Caytoniales. Taxonomy The genus was first established by Sergio Archangelsky based on material from the Anfiteatro de Ticó Formation ...

''/''Ktalenia'' and the conifer ''

Brachyphyllum ''Brachyphyllum'' (meaning "short leaf") is a form genus of fossil coniferous plant foliage. Plants of the genus have been variously assigned to several different conifer groups including Araucariaceae and Cheirolepidiaceae. They are known from ...

''. The depositional environment is characterized by river deposits, and the fossils show little evidence of transport.

References

{{Taxonbar, from=Q106689299 Cretaceous Argentina Fossil record of plants Prehistoric angiosperm genera