What makes fossils unique

A fossil can preserve an entire organism or just part of one. Bones, shell s, feathers, and leaves can all become fossils. Fossils can be very large or very small. Microfossil s are only visible with a microscope. Bacteria and pollen are microfossils. Macrofossil s can be several meters long and weigh several tons. Macrofossils can be petrified trees or dinosaur bones. Preserved remains become fossils if they reach an age of about 10, years.

Fossils can come from the Archaeaean Eon which began almost 4 billion years ago all the way up to the Holocene Epoch which continues today. The fossilized teeth of wooly mammoth s are some of our most "recent" fossils. Some of the oldest fossils are those of ancient algae that lived in the ocean more than 3 billion years ago. The word fossil comes from the Latin word fossus , meaning "having been dug up. Fossilization is the process of remains becoming fossils.

Fossilization is rare. Most organisms decompose fairly quickly after they die. For an organism to be fossilize d, the remains usually need to be covered by sediment soon after death. Sediment can include the sandy seafloor, lava , and even sticky tar. Over time, mineral s in the sediment seep into the remains. The remains become fossilized. Fossilization usually occur in organisms with hard, bony body parts, such as skeleton s, teeth, or shells.

Soft-bodied organisms, such as worms, are rarely fossilized. Sometimes, however, the sticky resin of a tree can become fossilized. This is called fossilized resin or amber. Amber can preserve the bodies of many delicate, soft-bodied organisms, such as ants, flies, and mosquitoes.

The fossils of bones, teeth, and shells are called body fossil s. Most dinosaur fossils are collections of body fossils. Trace fossil s are rocks that have preserved evidence of biological activity. They are not fossilized remains, just the traces of organisms. The imprint of an ancient leaf or footprint is a trace fossil. Burrows can also create impressions in soft rocks or mud, leaving a trace fossil.

Paleontologist s are people who study fossils. Paleontologists find and study fossils all over the world, in almost every environment, from the hot desert to the humid jungle.

Studying fossils helps them learn about when and how different species lived millions of years ago. However, paleontologists are now looking closer at fossils and recognizing thin carbon layers in the rock around fossils as soft tissue.

Recently, a team led by Mark Norell, a paleontologist at the American Museum of Natural History in New York City, identified a layer of carbon around dinosaur embryos formed over million years ago that they think was a soft eggshell!

In addition, the hard parts exoskeleton of some insects and arthropods are made of chitin, a polysaccharide related to cellulose. If you can identify the minerals present in a fossil, you can distinguish if it is original material or altered. Alteration of hard parts is much more common in fossils and happens when original skeletal material is either permineralized, recrystallized, replaced, carbonized, or dissolved Table 6. Trace fossils, which we discussed in Chapter 4, are not really fossils but the evidence that organisms affected the sediment by burrowing, walking, or even leaving behind excrement or vomit.

One last rare type of trace fossil is gastroliths, extremely smooth polished stones that aided digestion in dinosaurs and crocodilia. These are more highly polished than stream-worn gravels. Gastroliths found in Jurassic sediments in Wyoming may have been carried by sauropods over kilometers from their source in Wisconsin.

This model shows a preserved fossil shell on the right not a cast, original and an external mold on the left of the ammonoid cephalopod Gunnarites sp. The diameter of the specimen not including surrounding rock is approximately 9 cm.

Cephalopod: Gunnarites sp. This is an example of an internal 1 and external 2 mold of the gastropod Cassidaria mirabilis from the Cretaceous of Snow Hill Island, Antarctica. It is approximately 6 cm in length not including surrounding rock. If you ever get asked by a friend to help identify a fossil, watch out for pseudofossils, which are accidents of diagenesis that look like a fossil but are just weird sedimentary formations.

Pseudofossils include septarian nodules that are mistaken for reptile skin or turtle shells, concretions are mistaken for eggs, and manganese oxide dendrites mistaken for ferns moss. Some fossils are incredibly fragile. Some delicate samples are prepared by air abrasion with talcum powder to remove the matrix. For some trilobite specimens, this takes thousands of hours to expose their delicate features.

Some fossils you will use may be easy to replace and others impossible. Only handle the specimens that your instructor says you can. If you are taking this lab when teaching is face-to-face in a lab setting, you will handle both real and replica specimens of fossils.

While these may have been around for millions or billions of years and seem like they are now rocks, they need to be treated with respect. Some of the fossils that you may handle may be the only specimen of their kind in the collection. Some of the larger specimens may be heavy, especially those that are molds filled with sediment.

Never try to scratch the specimens for hardness. Also, never use acid as a mineral test. Finally, if you break or steal a specimen, you will be charged for its replacement. You are free to make sketches or photograph the specimens. If you do this, you may want to put a scale in the image, such as a coin or ruler. This will help you remember the size of the object.

Some specimens will have labels or numbers written on them, and others will not because they may be too fragile to even be written on. You must put each specimen back in its appropriate box or location in a lab tray. Also, do not move any of the paper labels from the boxes. This will prevent confusion for other lab students. The price of fossils for sale ranges from cheap to outrageously expensive. This specimen only had bones and was one of the most complete of its species.

Inspect the first set of samples and fill out the table with information about the presence of original biologic material, positive and negative relief, and mineral composition of the samples.

Identify the mode of preservation of the fossils. Use the flowchart in Figure 6. Leave these blank if necessary. Critical Thinking: Why is replacement the most common mode of preservation?

The way an organism can become fossilized depends on many things. Below are some examples to think about. Now it is called the Delaware basin, home to a major oil field Figure 6. This reef is now exposed in three mountain ranges; Apache , Guadalupe , and Glass Mountains.

Elsewhere, the reef is now buried around the entire rim of the basin. The northernmost exposure of the reef is part of the Guadalupe Mountains National Park. It is home to Carlsbad Caverns, which has the largest underground chamber in the United States. The reef was home to many fossils , including ammonoids, bryozoans, algae, sponges, brachiopods, gastropods, pelecypods, echinoids, fusulinids, trilobites, corals, and crinoids.

Unlike modern coral reefs, such as the Great Barrier reef of Australia or the reefs off the coast of Florida and Belize , it was constructed from sponge s, algae, and lacy animals called bryozoa.

The reef is subdivided into three parts: back reef, reef, and fore reef. Each had its own unique ecosystem as well as lithology and preservation. The Delaware inland sea had a narrow outlet to the Panthalassan ocean, much like the Black Sea today. These brines also dissolved the silica-rich sponges that formed the reef and affected the fossil preservation in parts of this Permian reef system.

Start at either McKittrick Canyon or the trail to Guadalupe Peak and drag the orange person icon onto one of the trails to see views of the massive limestone reef. The stratigraphy of this basin is complicated because it varies with time and position in the reef.

According to recent sequence stratigraphic analysis, there were up to six transgressive-regressive sequences in this basin Kerans and Kempter, An internal mold forms when sediments or minerals fill the internal cavity, such as a shell or skull, of an organism, and the remains dissolve.

In recent years, researchers have discovered that some fossils aren't just made of minerals. Fossil analyses have shown, for instance, that some retain organic material dated to the Cretaceous, a period that lasted from Tests suggest that these organic materials belong to dinosaurs because they match certain proteins from birds, which evolved from dinosaurs.

It's unclear how the organic material is preserved, but iron might help the proteins become cross-linked and unrecognizable, or unavailable to the bacteria that would otherwise consume them, Lacovara said. Formaldehyde works in a similar way, cross-linking the amino acids that make up proteins, making them more resistant to decay, Mary Schweitzer, a molecular paleontologist at North Carolina State University, told Live Science. Another idea is "microbial masonry," Lacovara said.

Moreover, sandstone — rock made of sand-size grains of minerals, sediments or inorganic material — seems to be the best type of environment for preserving organic material in fossils.

Maybe we need the bacteria to get through fast and to chomp through the sediment so that they can sequester some of [the surviving organic material] in the process.