ARGENTINEAN PLANTS OF THE CRETACEOUS

Pterodofitas

This group includes the oldest plants with vascular structure that lived on the planet. The FERNS are the most important ones. They are found in Paleozoic stratums all over the world. Its resistance to the adverse climatic conditions made of them beings of extreme ecological plasticity, similar to the angiosperms. After catastrophes produced by fires or volcanic eruptions and floods, usually they are, and they were, the first settlers of devastated environments. Its great expansion capacity allowed them to be excellent fossil elements to make chronological correlations to continental scales.

During the Cretaceous, along the Patagonia territory, there were a lot of ferns that proliferated in forests, prairies, and valleys. In general they belonged to groups that are still alive, though in a lower scale, such as the OSMUNDACEAS, GLEICHEIACEAS, or DIPTERIDACEAS. But during this period, other kinds of ferns appeared such as the PTERIDACEAS, CYATHEACEAS, HYMENOPHYLLACEAS, etc. They are the ones that ornament our gardens nowadays.
They must have covered very big land extensions, occupying the ecological niches that today belong to the grasses ' family and other angiosperms that didn't have appeared by the time.

Gymnosperms

They are the plants that have bare or unprotected ovules in their flowers. (GIMNO= bare, SPERMA= seed ) Today, most of them are trees, and they have their reproductive organs in complex structures more or less compact ones, known as cones.
Their origin come from the Paleozoic Era, and they were very important along the Mesozoic Era, specially during the Jurassic and Cretaceous periods. They have been displaced nowadays from several ecological niches by the ANGIOSPERMS.
During the Cretaceous several different kinds of gymnosperms lived side by side, some of them weren't very common ones such as the PTERIDOSPERMS or ferns with seeds, the CLAMIDOSPERMAS, the BENNETTITALES, the GINKGOALES with only one surviving species, or the CYCADALES and the CONIFEROUS, with a lot of species.

Ruflorinia

This bush belonged to a community that went along the Patagonia valleys and savannas during the Cretaceous. It seemed to be a fern but it reproduced by seeds that were produced in small ovules clusters that were placed on the leaves raquis.
They were GYMNOSPERMS or plants with bare seeds, and they belonged to the group of the PTERIDOSPERMS, ferns with seeds. They are completely extinguished nowadays.
The Ruflorinias are one of the last representatives of the group, and their discovery along some Patagonia's areas has allowed to confirm that the PTERIDOSPERMS existed even though the ANGIOSPERMS had appeared. This plants lived side by side with other bushy species such as ferns, CYCADALES, BENNETTITALES and CONIFEROUS.
Its name is due to the Swedish Paleo-botanic Rudolf FlorÍn who contributed to the knowledge of the Mesozoic Gymnosperms to world level. He was also the propellent of the "cuticle analysis", a technique to study the structure of the leaves epidermis.

Bennettitales

They belonged to the GIMNOSPERMs group. They were completely Mesozoic and they extinguished by the end of the Cretaceous. They formed big communities along the Patagonia's areas, and they grew together with coniferous and ferns.
They are regarded as the ANGIOSPERMS ancestors, because they had similar reproductive structures to the present flowers.
They were like the CYCADALES, they seemed to be small palms trees from 1 to 3 meters high. Their cylindrical trunks were covered by foliated bases where the leaves inserted. They formed a kind of chaplet. Their reproductive organs were inside cones similar to flowers inserted into the foliated bases.
There were several types of BENNETTITALES that were different because of the shape of their leaves.
The most representative kind from the Patagonia were the" Zamites, Otozamites, Dictvozamites, Pterophyllum and Ptilophyllum".

Coniferous

They were and they are, generally, very high trees, that live in pure communities or associated to other groups of ANGIOSPERMS.

© Argentina On View

They were and they are, generally, very high trees, that live in pure communities or associated to other groups of ANGIOSPERMS.
It is one of the oldest groups of GYMNOSPERMS recognized in the Carbonaceous stratum, and they got great dissemination power during the Jurassic and Cretaceous Periods. There are a lot of petrified ones along the whole planet. In the Patagonia territory there is one of the most well known examples along the whole world: Santa Cruz Province's Petrified Forests, recognized as Natural Monument. Their heights are about 30 meters, and 2 meters diameter. They confirm that the araucarias were the predominant ones about 150 million years ago.
Other interesting testimonies are the pine cones' accumulations that have been found along the same province. They are constantly being plundered, avoiding like that the scientific investigations with an exceptional detail.
During the Cretaceous the araucarias went on disseminating but other CONIFEROUS occupied several ecological niches. Some of them extinguished during the Cretaceous, such as the CHEIROLEPIDIACEAS that produced a pollen called clasopoliss. Some others are still growing along the Patagonia forests, such as the PODOCARPACEAN. The Patagonia territory was a planetary region where the coniferous dominated the paleo - physical associations, as it is shown by the oldest registers of the Late Paleozoic.

Ginkgoales

They are currently represented by only one species, the Gynko Biloba. It is widely cultivated all over the world. Their leaves are fan shaped, and their veins are divided in fork. Their sexual organs are in separate individuals.
Their geological history comes from the Paleozoic and Mesozoic Eras. Along the Cretaceous there were also some species identified as KARKENIA.
Later on, some other fossils were found in other regions of the planet, such as Siberia, and allowed to set a new group the KARKENIACEAS, as a homage to the original ones from the Patagonia. These fossils show that there was another kind, which is extinguished today, they were the GYNKGOALES. It is interesting to outstand that along the Patagonia region, there were some Paleozoic kinds with fructifications that have been regarded as possible old stocks of the Mesozoic sort.