Facts About Trace Fossils That Help Unlock the Mystery of Evolution

Facts About Trace Fossils
Fossils are a source of evidence of some past happening. There are different types of fossils, trace fossils being one of them. ScienceStruck traces down the trace fossil facts.
ScienceStruck Staff
Last Updated: Dec 9, 2017
Did You Know?
It is always easy to find a trace fossil than a body fossil. An animal will die once, but before that, it will leave several marks behind which can form trace fossils.
Trace fossils give a lot of information and indirect evidence about an entity. It is not like a body fossil that shows a part of the animal. This kind of fossil just shows some markings, which may be in the form of footprints, hand prints, burrows, and bite marks. It may also include droppings that became fossils, skin impressions, or any other markings. These fossils can be found commonly because an animal will leave several imprints in its whole lifetime. Another advantage of this type is that it gives information about the behavior and living conditions of that particular animal. But the disadvantage to this is that, it becomes difficult to know which exact animal it is and its definite origin. These fossils have been of great help to paleontologists and archaeologists to find some real activities and incidents that happened in the past. This fossil particularly has contributed to know about dinosaurs.

Trace fossils are also known as ichnofossils, and the study of such fossils is called ichnology. It includes the further division into sub types. Read on to know more about them.
Formation of Trace Fossils
▶ According to the Ottawa-Carleton Geoscience Centre, trace fossils generally get formed on soft things. Just like we get our footprints on sand, dinosaur's footprints left a mark on the sand that they walked on. Some of this sand dried and got covered by sedimentary rocks, which was later left isolated for many years.
▶ The trace fossils in the form of burrows stayed the same for millions of years because of rock formations on it.
▶ The fossil with a skin impression may happen when the animal might have sat down or laid down on sand or mud. The mud gets buried and then it turns into rocks.
▶ The droppings that turned into fossils are also formed in the same way. These give evident information about the diet of a particular animal.
Types of Trace Fossils
☆Repichnia
It involves all the fossil forms that come under the locomotion category. This category involves footprints or certain tracks. The fossils may show slithering and crawling movements. The footprints give away information about the living conditions; say if it lived alone or in a group, or if it had a tail. If it had a tail, it is important to know whether the tail touched the ground while walking. All these questions are answered by this type. It also tells about the length of stride and the speed in some cases.
☆Pascichnia
This type includes fossils of animals that dig while finding food. This type is identified by different patterns that are formed when the animal is digging. The best examples have been seen where the water surfaces meet the sediment rocks.
☆Domichnia
This type includes fossils that are related to dwelling. It includes remains of burrows or borings. The fossil can be that of a permanent habitat or something built for temporary safety or shelter. The examples found are seen in different shapes and sizes like U-shaped, vertical, or cylindrical.
☆Cubichnia
This type of fossil has been formed by animals while they were resting or hiding. It shows that an animal was sitting at that place for a while. This type indicates how big the animal must be to have left behind such an imprint.
☆Fodinichnia
This type focuses on the feeding tracks of an animal. It includes burrows, which show that the animal has excavated for feeding. It comes in various sizes such as U-shaped or tubular.
Other Subtypes
The Accepted Classes
✦Aedificichnia
It was covered by Brown & Ratcliffe in 1988. It is something that has been made by creatures by building on a substrate and attaching itself to the substrate. The best example can be that of a wasp nest.
✦Agrichnia
It was proposed by Ekdale et al. in 1984. In other words, it can be also called "gardening traces". This includes the remains of burrow networks of animals that prey on smaller organisms ,which moved freely near that area.
✦Calichnia
This was covered by Genesee & Bown in 1994. This includes an activity that's specifically about breeding. Bee cells or nests are examples.
✦Equilibrichnia
It was put forth by Bromley in 1990. It mentioned organisms that buried themselves as a response to sedimentation rates. These fossils come in the form of burrows, which show the action of the organism. It might go up to avoid getting buried or the opposite, by getting buried to avoid exposure.
✦Fugichnia
It was proposed by Simpson in 1975 and is also known as "escape traces". It involves the marks of an organism trying to escape from getting buried during high-sedimentation times like turbidity/density current. It is commonly seen in a chevron pattern, and the desperate movements of the animal can also be noticed.
✦Praedichnia
This was put forth by Ekdale in 1985. This type gives a lot of information about the behavior of the animal. It may be in the form of borings, shells, and teeth marks on bones. This type is particularly seen on hard objects.
The Non-accepted Classes
✦Chemichnia
It is nothing but agrichnia (appears somewhat like a gardening network) that is formulated for the purpose of harvesting bacterial cultures.
✦Cecidoichnia
It is an irregular outgrowth that looks like a gall, and is present on the plant tissues. The outgrowth occurs as a result of animal, plant, or bacterial interaction.
✦Corrosichnia
As a part of the name suggests, these are traces or a form of corrosion that is left behind by the roots of plants. This corrosive action occurs on sediments.
✦Cursichnia
This trace occurs as a result of the locomotory tracks left behind by organisms, and usually occurs due to their walking/crawling habit.
✦Fixichnia
This trace is an outcome of the support that sessile organisms make use of while holding on to a hard substrate.
✦Mordichnia
This trace is indicative of the death of a prey after it was assaulted.
✦Natichnia
This is a kind of locomotory trace left behind by a swimming organism (such as benthic fish) after shaking up a soft sediment.
✦Polychresichnia
The word 'poly' in the name gives us a clue. This trace fossil is a result of multiple behaviors. For instance, domichnia served as a life position for organisms.
✦Sphenoichnia
This trace is an outcome of the retreading action of soils and sediments done by plants and animals.
✦Taphichnia
This is a trace fossil that is indicative of an animal that tried to get away but was buried, and is often found along with its body fossil.
✦Volichnia
It includes the impressions of an organism that has been left, after landing from a flight. This type mainly focuses on the imprints of a flying insect.
These types of fossils has been very useful in finding information about dinosaurs. This is the reason we enjoyed the Jurassic Park movie series so much! Or else, who would have ever known about those big extinct creatures? All this is so interesting, which makes us realize that we have so much to learn about archaeology!