Fossil Friday 4/17/15: Fossil Plants preservation and Identification

We all must have had in a point of our life heard about how extinct organisms remains become fossilized, either by books, movies or even in the Discovery or History channel. TheropodsizeThere are many different types of fossilization processes including Permineralization, Cast and Molds, Replacements and Crystalization,  and Carbonization, We often encounter these in the context of animal shells or bones, but what we hardly ever hear about is the preservation plant fossils. Plants, just as the megafauna, can be preserved in the rocks. Typical plant fossils are wood, seeds, roots, flowers, pollen, and leaves which are by far the most commonly preserved macroscopic plant part.

Plant fossils are commonly preserved in fluvial or deltaic systems where rivers deposit sediment. Many of the best leaves are preserved in abandoned river channels that form oxbow lakes. The fossilized leaves from Tennessee that I am studying were collected from oxbow lake deposits. In these oxbow lakes the plant parts are deposited gently in fine-grained sediment and can be preserved with excellent detail. As the sediment is buried by further flooding events water is squeezed out of the sediment and the internal structure of the leaf is squashed. Eventually, only a thin carbonaceous film that will outline the original plant structure.This fossilization process is known as compression. If the grains of sediment are large and angular the fossilized leaf will have poor detail, but the grains are smooth and fine, as is typical in oxbow lake deposits, the fossil will be full of detail that will help in identification.

The ability to identify fossils is controlled largely by the quality of preservation.In the case of leaves, the best way to identify the species is to describe the leaf characters such as shape, size, leaf attachment, lobation, the type of margin, and the venation pattern. Leaves come in many shapes which is the measurement of the leaf length  from the base to the apex. These can be divided into four main shape: Elliptic, the widest part of the leaf is at the middle of the leaf; Ovate, the widest part of the leaf is near the base; Oblong, the opposite margins near the19326-055659 middle of the leaf run parallel having the same width; Obovate, the widest part of the leaf is near the apex. Also the lobation of a leaf is a great way for  identification. A lobe is a marginal projection of the leaf where the sinus is increase into the leaf, these can be identified as Palmately Lobe, Pinnately Lobed or unlobed. Leaf margins can vary from toothed margin that have projections, known as teeth along the margin, or smooth margin which don’t have any kind of projections. Describing the vein architecture is another important way to distinguish and identifying species. Each species of leaf has its own vein architecture, almost like our fingerprints. The primary veins of leaves may be pinnate or palmate. The secondary veins may be Craspedodromous (secondary veins terminate at margin);  Semicraspedodromous, (secondary veins branch near the margin); Eucamptodromous, (secondary veins do not branch or reach the margin); and Brochidodromous, (secondaries reach the margin forming loops and arches). Almost every species has a unique combination of these and other leaf architectural features.

One of the reasons we study fossil plants is to learn about the history of earth’s climate. Leaves in particular can be used to estimate climate variables like mean annual temperature and rainfall. Once we know all this we can compare the plant fossils with the megafauna fossils from a same location and learn about the interactions between the two of them. Such as understanding the megafauna’s migration cycles cause by the seasons that can be recorded in the plant fossils. We can understand very little of the planets past by only studying the megafauna, but by studying the fossil plant we begin to see the bigger picture, and if we connect the clues we can construct and fully understand the paleo-ecology of our ancient planet.

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(Permineralization, is the replacement of tissues or cells by minerals; Cast and Molds, is when the organisms remains is destroyed and only the external mold and internal mold are preserved; Replacements and Crystalization, occurs when the shell or bone tissue is replace by another mineral; Carbonization, are the remains preserved in a thin layer of the chemical element of carbon.)

Update on BioMuseo Adventures

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The fruits of Jorge Moreno Bernal‘s labor at Lake Alajuela. Two crocodile teeth, a ray tooth (both bottom-right), and a possible mammalian pelvis or shoulder plate.

In a previous post, Jeremy told us of some of the many exciting things that have been happening in the field as of late.  Lake Alajuela is proven to be not only a very beautiful field site, but fruitful as well; we hope to continue prospecting and discovering there!  In this post, however, I want to talk a little bit more about our work outside the field.

We only have about three weeks left in Panama, and there are many things that we still want to get done.  Creating a narrative for the BioMuseo is one of our main priorities, and there is still much to do.  As promised, today I will give an update on how things are going with our work with the BioMuseo. Continue reading

Smithsonian’s Panama Debate Fueled by Zircon Dating | Newsdesk

Ocean currents before the formation of the Isthmus of Panama. Photo Smithsonian Tropical Research Institute

Ocean currents before the formation of the Isthmus of Panama. (Photo © Smithsonian Tropical Research Institute)

Camilo Montes and colleagues have made exciting discoveries about the dating of the rise of the Isthmus of Panama using detrital zircons! Visit the following link to the Smithsonian’s website to read the press release! Smithsonian’s Panama Debate Fueled by Zircon Dating | Newsdesk.

Duke Trip

Last week Justy, Nathan and myself headed to Duke to microCT scan fossils from the Panama Canal. Our main goal was to scan 71 fossil teeth belonging to various rodents, but we brought various other fossils along as well in case we had extra time. Overall we ended up scanning all 71 rodent teeth, 6 crab fossils, and various plants all from the canal sites. We even scanned some fossils for our personal research projects including a turtle skull and some sciurid postcrania.

When we arrived at Duke we met with Jimmy Thostenson, the engineer/technician in charge of running the scanner. Jimmy taught us how to position our fossils in the scanner, and then he set up the scanner and explained to us how it worked along the way. We queued up our specimens that would be scanned that day, and then left to explore campus. We returned later when they were finished scanning and checked the images to make sure they were looking good. At one point the axis of rotation of our scans were off, so Jimmy taught us how to fix that. We then opened up each scan in Avizo and made a rough 3D image to make sure all was well. All of our scans ended up great!

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Jimmy teaching us how to set up the scanner as Nathan and Justy look on.

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The inside of the microCT scanner.

A Sciurid humerus from the Thomas Farm site in Florida, as it was being scanned.

A Sciurid humerus from the Thomas Farm site in Florida, as it was being scanned.

While our specimens were scanning, we were able to explore Durham. Continue reading

Full Plaster Jacket

Today was yet another beautiful day at Lago Alajuela, where we have spent the last two days searching for fossils from the relatively unexplored Alajuela Formation. This site hosts an amazing array of marine fossils ranging from mollusks and sharks to turtles and crocodiles, as well as the occasional terrestrial vertebrate. We were fortunate to have this opportunity, as water levels are usually too high to expose a decent amount of the outcrops due to either excessive rainfall or water not being released from the dam which is used to fill the canal. The hunt was on!

An amazing find. The large bone plate was found relatively compete in situ. This specimen was collected from the relatively weathered sandstone horizon on the southern shore of the lake.

An amazing find. The large bone plate was found relatively compete in situ. This specimen was collected from the relatively weathered sandstone horizon on the southern shore of the lake.

From the beginning the findings were good. Continue reading

Panama, Millipedes, and Research…Oh My!

I ended last month doing a lot of fossil preparations and started the month of March in Panama. Having spent a rainy February in doors it was great to get out into the field and looking for fossils. They were early mornings and long days filled with lots of sun. Spending days out by the canal was a great experience. Having collected at other sites that had abundant specimens it was great to experience other sites with fewer and harder to find specimens. One site, newly opened, on the east side of the canal produced hundreds or new specimens of both shrimp claws and crab carapaces.

Me looking for Millipedes, and plant fossils

Me looking for Millipedes, and plant fossils

On the first day we went to several of the sites we could later spend more time at. The second site we went to is known as Las Cascadas. It was at this site on a previous trip that Dr. Aaron Wood found a rare fossil millipede. We spent about half of a day looking for any more but had no success in finding another. The rest of the week was spend at several other sites on both sides of the canal looking for crabs and other invertebrate fossils. While several of us spent time at other sites the vertebrate contingent made several great finds at the Las Cascadas site. Continue reading

Sweet Home Alabama!

For the past few day I have been in Alabama with Prof Steven Manchester and his class IMG_20150328_083224885_HDRsearching for fossilized leaves. We departed from the Museum at 1 pm on Friday and arrived in Birmingham, Alabama  at 9 pm. We rested for the night at a hotel and early in the morning headed to Cahaba Environment Center at Living River. At the site we meet up with other professor from the area whom would be our guides. Continue reading