A continuación se presentan algunas imágenes de fósiles de helechos, con la intención de mostrarlos para estudiantes o como una información general, sólo por mencionarlos. Desafortunadamente no poseemos información sobre ellos.

Fósiles

The ferns are an ancient lineage of plants, dating back to at least the Middle Devonian. They include four living groups: Marattiales, Ophioglossales, Psilotales and leptosporangiate ferns. There are also some early groups that are now extinct, including the Stauropteridales and Zygopteridales. The chart below shows the stratigraphic ranges over which each group is known to have existed. The green taxa on the right side of the chart are groups of ferns; the blue taxa to the left are sphenophytes; and the purple Cladoxylopsida in the center are a closely related group.

Splendid 6 1/4" Brazil Petrified Wood Tietea Fern Round

6 1/4" X 5 3/4" X 1/2", 18.2 ounce, 230 plus million-year-old, expertly finished petrified Tietea fern round from Brazil with bark running the circumference. This was cut and polished by a master-craftsman in Oregon. The preparation of this piece is among the best we have ever seen. The cuts are perfectly parallel and on one side, a flawless lustrous polish representing several hours of work by a perfectionist is present.

We spent a great deal of time hand picking the best-looking examples we could find directly from the master-craftsman, himself. His work is simply outstanding and he had so many stunning pieces that this was no easy task. These are the finest we could find in this size range. The cuts are symmetrical, the polished surface is superb and the wood itself is remarkable.

This a beautiful slab from a tree fern that grew in the northern region of Brazil (Pedra de Fogo formation).
Most of the wood fossils found in this region are from the Permian Period of the Paleozoic Era (from 286M years to 245M years ago). This is probably a Dadoxylon sp..
If you know more about this specimen, please email me!
Weight
 2 lb. 6.5 oz.
Size
 9 4/8 inches X 9 inches X 3/8 inch deep.

A 1/4" thick slab with color and pattern that should cut some cabs. Pictured wet in natural light to show color and pattern. Winning bid plus $3.85 S/H will make it yours. Multible winning bids combined to save on S/H. Inquire about S/H on small single items. Outside the US please inquire about S/H cost.

This a beautiful slab from a tree fern that grew in the northern region of Brazil (Pedra de Fogo formation).
Most of the wood fossils found in this region are from the Permian Period of the Paleozoic Era (from 286M years to 245M years ago). This is probably a Dadoxylon sp..
If you know more about this specimen, please email me!
Weight
 2 lb. 11 oz.
Size
 12 3/8 inches X 9 2/8 inches X 3/8 inch.

Large slab of hard shale with fossil ferns on both sides (see pics).Alethopteris serli from the Upper Carboniferous rocks of St.Clair,Pennsylvania,U.S.A.Ferns are preserved in white on a dark background-very striking fossils.Block is 172mm long at maximum.

GOE Tietea Singularis- Petrified Tree Fern Slab CORAL

FINALLY - some new stock of this material as I just sold the last of my slabs.  Presented here is a matrix covered end slab of Tietea Singularis that is a very colorful petrified Tree Fern from Brazil and it is from the Paleozoic era and the Permian period which makes it about 245 million years old.  This fascinating slab, which features a very deep orangey  coral along with white, and, tan and  gray colors with those excellent squiggly brain-like patterns so common and desirable in petrified fern.  Measures measures 5" x 4 1/4"  x  1/4"  If you are a serious Petrified Wood or Fern collector then this should definitley be a part of your collection as a display slab.   Or - great as a special cabbing slab - wonderful for special projects.
 
 

 
 

 
White fronds on black shale excavated from Llewellyn Formation, St.Clair, PA.
This slab measures 31" x 17" at its widest points! Thickness varies from 2 3/4" to less than an inch. I left it thicker on the bottom, and this fossil can actually stand up on its
own(although a stand would be recommended for long term display). It is pictured below standing up by itself. This fossil weighs about 40 LBS! Age: Pennsylvanian (300 million years ago)

Believe it or not, the colors are natural! It is this exceptional state of preservation that gives the St. Clair, Pennsylvania fossil ferns their great exquisiteness. It's hard to comprehend 100 years, let alone 3 million times that many, but these carboniferous ferns died between 280 and 310 million years ago!

These natural wonders fell into a bog where a low temperature, low pressure, oxygen depleted environment evolved the plant tissue into Pyrite. Pyrophyllite(Aluminum Silicate) replaced the Pyrite at an ensuing stage, creating the bold, white color. Any orange-ish color was caused naturally by the presence of iron ore. We never paint or touch them up.

Nature and time are the artists.

Dozens of plant species are found in these shales, so look closely. Common species include Alethopteris, Neuropteris, Pecopteris, and Sphenophyllum. Seed ferns went completely extinct around 73 million years ago, while the dinosaurs were still around! This would be a perfect addition to anyone's fossil collection! Please wait for the pictures to load, there are
a few of them.

                      
 
 

Referencias

http://www.ucmp.berkeley.edu/plants/pterophyta/pteridomm.html
Thomas, B.A. 1991. The study of fossil ferns. British Pteridology 1891-1991: 7-16.
http://www.nccn.org/patients/patient_gls/_spanish/_breast/5_treatment.asp
http://www.nlm.nih.gov/medlineplus/spanish/breastcancer.html
Huge St.Clair PA Fern Fossil Slab
 

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