E.S.C.O.N.I.

Chairman John Good called the meeting to order and everyone introduced himself or herself. Jim Fairchild reported that he had copies of "Creature Corner" available for $8 as well as copies of the Mazon Creek flora and fauna books. John Good then thanked the members who helped out with the Paleo Group exhibits for the recent March Show. John then talked about the upcoming field trips. The next one is to Braceville on March 23 and 24. Things are still not certain for Mazon Creek, but they say that the fishermen are screaming to get in and since they pay, the area may open up at least partially. The Monster Lake area should be open April 1. MAPS in Macomb will be on Tracks, Trails and Traces on April 12-14. April 7 will be to Lone Star. April 27 and 28 will be to Kentucky for fluorite if there is interest. He is also working with the Louisville Club on reciprocating field trips. The big summer trip will be the second and third weeks of June to Nebraska and South Dakota. Dave Bergmann will lead the first week to many fossil sites in Nebraska and John will lead the second week. Both Fridays there will be the opportunity to dig for dinos with Paleo Prospectors and member Rob Sula for a fee.

                                        Future Paleontology Group Meetings

April No Meeting, MAPS

May 18 Fossil Fish with Irene Broede

A touch of class was added to our meeting by member Rob Sula who graced us with some Paleo Poetry he had written called "Ode to a Blob". It will be reproduced on the web and in the Bulletin. The audience roared their appreciation! It was a hard act to follow but Karen Nordquist then took the floor for the main presentation.

Trace Fossils

We study fossil bones we find to learn more about the creatures that lived a long time ago. However, there are other clues that these critters have left behind that help us understand how they lived and what they did. These are called trace fossils, ichnofossils or lebenspurren. Some of these clues and what they can tell us include:

trackways (furrows and imprints) to help show us how they moved,

burrows to tell where they lived,

skin impressions to help us see how they looked, but never color

coprolites to tell us what they ate,

eggs to show us how they reproduced,

teeth marks on bones and bite marks on leaves to tell us how they ate

Unfortunately, a common problem with all these traces is that it can be difficult to match the trace with a specific species and genus of animal. Even when an animal is found within the burrow itself, it may not be the burrower, but may be a predator or secondary occupier of the trace. Indeed, many of the traces, especially trackways and eggshells, are given their own names. The earliest trace fossils are reported from the Vendian in Precambrian times. I will try to cover the different kinds of traces with examples from several time periods in sequence including some famous lagerstatten like Mazon Creek (300 MYA), Solnhofen (Germany, Upper Jurassic – 150 MYA), Hunsruck (Germany Devonian – 390 MYA).

TRACKWAYS

What can trackways tell us? There has been much study and in many cases now they can tell what kind of animal left the tracks, like a sauropod versus a theropod, but getting down to species is tricky. By studying the bone structure of the foot and that of living relatives and understanding the surface at the time the track was made can help narrow down the candidates. Sea bed trackways can be obliterated by the tiny microorganisms that inhabit the sand floor. They are moving constantly and disrupting the positions of the grains of sand. Studies show that this can happen over a few days. So it is a marvel that any tracks are ever found. In general the traces start out very simple in the Vendian times and become more complex in the Precambrian. After the Cambrian explosion they became even more complex with the emergence of hard bodied animals that were better preserved and that were able to build better structures. By the time of the Hunsruck slate (390 MYA) there are many trails left by the trilobite Chotecops which even show the setae fringe on its legs.

Dinosaur trackways have been studied for a long time. They study tracks to determine things like social behavior as many of the tracks seem to be of groups traveling together. Sizes of the prints are being looked at to see if there is a way to tell the sex or age of the animals. The Paluxy River Texas tracks of two different dinosaurs on the same trackway are very famous. These have been interpreted as a chase sequence involving a large sauropod trying to evade a theropod that is shadowing its steps and then lunging at its flank. Unfortunately, as usual there are no bones at the end of the trackway to tell us what animals they were and what the result of the interaction was. And there are those who do not believe that they were made by animals there at the same time. It is interesting to note the very recent discovery of theropod tracks in England 163 MYA that show a walking animal changing gait to a run in one set of tracks. There are three sets of theropods using a wider gauge toes in pace and one shows a change from this gait to a faster narrow gauge with toes out. They need to know more about the maker and its leg length etc to determine speed. Another interesting fossil from a later time in the Green River area of Wyoming (50 MYA) shows a water bird trackway that also has "dabble" marks where it was pecking into the sea bottom looking for food.

BURROWS and HOLES

Why do animals burrow? Marine organisms burrow for respiration, predation, gardening, feeding, reproduction and protection. Continental burrowers have more extreme fluctuations in water table level, and weather conditions with which to deal. The burrows of insects and crustaceans have been used to learn about the climate and conditions of their times, like dampness, water table levels and seasonality. Some of the organisms make similar burrows on sea or on land. The interior layers of soil are less disrupted than the actual surface. Burrows provide protection from the disruptive events at the surface as well as protection from predators that hunt by sight. However this can backfire when predators hide in burrows and wait for other burrowers to come along. They can also aid in respiration by providing a slow flow of water past the animal in the burrow to bring it oxygen. By using tentacles, hairs or slime, they can collect food particles in this flow. Most of them actually derive nourishment from the particles in the sediment itself for they are covered with algae and bacteria that are decomposing it. One usually thinks of the food as settling on the top of the sea bottom (detritus, which is still the richest food source), but these layers get buried as time goes by and that means that they are available in the lower layers also. Many of the tunnel burrowers continue to feed off the top level while their bodies remain within the burrow as food tends to come to the bottom regularly. Some shrimp actually cultivate certain bacteria within the walls of their burrows for their food supply. There are four general burrowing techniques used: intrusion, compression, excavation and backfilling. In some cases the maker can be identified by the shape and construction of the burrow. Anemones build burrows a little longer than their bodies and feed from the top. If threatened they pull the body into the tube. Some detritus feeding shrimp feed at one end of a U shaped tube and put their fecal pellets outside the other end.

Eggs and Nests

Eggs tell us about the reproductive strategies of the animals that produced them. One of the earliest is Palaeoxyris from Mazon Creek that was not identified as a shark egg case until the 1970s. There are famous dinosaur egg sites now in Montana and in Argentina that provide prolific information and theories about dinosaurs and how they reproduced. The Maiasaur nests of Egg Mountain Montana show that the babies were helpless and this led to the good mother theory for the animal. However, the nesting sites in Patagonia indicate that the nests were abandoned and the babies were on their own.

Skin Impressions

We often see paintings of prehistoric animals and we wonder how the artists know the proper way to show them. Fortunately there are some sites where preservation is so good that features like skin and feathers are found. In rare instances, mummified animals are also found and they tell us even more about what these animals looked like. And there are quite a few skin impressions of dinosaurs, mostly sauropods that have been found and studied. There is also an impression from the theropod Carnotaurus from Argentina (which is why I think Disney chose it for its movie "Dinosaur" since it had interesting scutes on it). Otherwise there is not much known for the theropods. The Patagonian titanosaur nest also revealed the first embryonic dinosaur skin that shows a range of beads set in several patterns. The skin is beaded and is not scaly with interlocking scales like snakes or lizards. Some fascinating fossils of lizards from the Green River show extensive skin impressions with individual scales visible.

Coprolites and Regurgitates

Coprolites are clues to the producer’s last meal and since they would normally decompose rapidly, they were probably preserved close to where the producer lived. Coprolites are numerous in our own Mazon Creek fossils and contain a range of matter including bone, scales, ostrocodes, and parts of bivalves and crustaceans. Most are not able to be matched with its maker although the spiral ones found are believed to be from lungfish, sharks or rays because of their spiral intestinal valves. Some Permian amphibians’ coprolites tell us that they had a diet that included fish, small amphibians and small reptiles. There have even been some feathers found in coprolites of crocs and fish. The Jurassic Solnhofen site has several examples of coprolites. One of the most common is named Lumbricaria intestinum and is often long (up to 6 feet) and worm-like and made up of calcite. Since it is so common it is believed to be from the more common animals like fish, crustaceans or cephalopods. Another interesting type of trace fossil is the cough ball made up of ejecta from the mouth. The one pictured is of an undigested fish about 20 inches long that was probably ejected by a larger fish or reptile. An early Cretaceous find of a mass of fossil bones in Spain is the first indication that birds were prey animals. There are at least three different species of birds present in the pellet. There is a Daspletosaurus sp. that was found in the Late Cretaceous rocks of Montana in the Two Medicine Formation. This would be the first report of gut contents for a tyrannosaurid. The remains consist of acid-etched vertebrae and part of a dentary from juvenile hadrosaur dinosaurs. This is in agreement with a large Canadian coprolite reported with young hadrosaur bones in it. There are also many reports of dinosaur bones found with teeth marks from tyrannosaurids, although they are usually on the limb bones not the vertebrae. There have also been reports of some gut contents of other dinosaurs, including lizards inside Compsognathus and Sinosauropteryx, a cannibalistic Coelophysis (controversial), and acid-etched bones found with a Baryonyx.

Gastroliths

Gastroliths are stones that were swallowed by the animal to help process food. There are some swimming vertebrates that swallow stones to change their weight and center of gravity. They were only known in sauropods, prosauropods and psittacosauruids. Sauropods held them in a musculature gizzard. Some of them had only pencil-thin teeth and could not process plants in their mouths. The Seismosaur ‘Sam’ fossil had two pockets of stones, one in front of the chest and one in the pelvis. There were 240 stones up to a size of 10 cm across with a high polish from the digestive acids.

Teeth Marks

Plant arthropod interactions have played an important role in evolution. For example, the evolution of angiosperms and insects are thought to be closely related. Interactions range from feeding to shelter, transport, reproduction and disease transmission and many of them leave traces. There are many examples of leaf feeding traces (surface or intervein), leaf mining (between the two cuticle layers of the leaf), and leaf galls (invading parasites). In addition the stems can show signs of wounding and boring and traces of damage can be found on spores and seeds. There are many Paleozoic shark teeth marks on cephalopods. Bite and gnaw marks on bones of mammals and plant eating dinosaurs are not uncommon. There have been reports of teeth marks from Allosaurus on the vertebrae of sauropods. There is also a ceratopsian pelvis bone with marks from a T rex on it. There was even a study done to determine the bite force of animals based on tooth marked bones. They found that the bite force of the T rex was from 6,410 to 13,400 N (newtons) which indicates a very strong bite that could withstand struggling prey. Some other bite force calculations to compare are 550 N for a dog, 749 N for humans, 1,446 N for dusky sharks, 4,168 N for lions and 13,300 N for alligators. (N = force to give acceleration of 1 meter/second to a mass of 1 KG. Equal to 100,000 dynes).

In summary, we can learn a lot from the traces that fossil animals leave behind. Usually it does not tell the whole story but instead gives us important clues as to how these animals may have lived a long time ago. I have just touched the surface in each of these areas and left only a few traces myself. This is just the beginning. Perhaps it will help when you visit MAPS this year and see some of the fossils with these traces upon them.

Many members described the trace fossils that they brought to the meeting. Irene Broede had several including worm burrows, a dinosaur track cast, and a coprolite. John Catalani had some with delicate trilobite trackways. Paul Guerino had a large slab with worm burrows. Rob Sula also had an interesting trackway. Dorothy Lamb had a coprolite slice and a Jurassic trackway. Andrew Hay had a beautiful Mazon Creek Neuropteris leaf with a chunk bitten away. Jim Schmidt and Jeanine Mielecki also described fossil traces they had. The meeting was adjourned for refreshments and more conversation.

Respectfully submitted Karen Nordquist, Secretary

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Last Updated 6/4/2002