WHERE TO LOOK

Plate 5FOSSILCOLLECTING EQUIPMENT

The items described above are those that are most needed and constitute the basic equipment of thefossilhunter. The serious amateur may wish to include certain additional items which will place his collecting on a more professional basis. Some of these accessory items are:

1. Atopographic mapof the collecting area. These are available for many parts of the State and are published and distributed at nominal cost by the United States Geological Survey, Washington, D. C., and/or Denver, Colorado. The Survey can supply an index sheet showing all such maps available for Texas.

2. Ageologic mapof the collecting area if one is available. The list of publications of the Bureau of Economic Geology should be consulted to see if a geologic report or map of the area has been published. This list may be obtained without charge from the Bureau of Economic Geology, The University of Texas, Austin 12, Texas.

3. Thegeologic mapof Texas. Although a geologic map of Texas is included in this publication (Pl. 10), the scale is so small that its use is somewhat limited. For more detailed work a larger geologic map in color (scale: 1 inch = 31.56 miles) may be ordered from the Bureau. The sale price is 25 cents.

4. Acompassfor more accurate location of collecting localities.

5.Adhesiveormasking tape. The locality information can be written on the tape and applied directly to the specimen.

6.Paper labels(about 3×5 inches). A properly completed label should be placed inside each bag of material.

Knowing where to look for fossils is a very important part offossilcollecting. It has already been pointed out that igneous and metamorphic rocks are not likely to befossiliferous, but that most fossils are found in marine sedimentary rocks. These sediments were deposited under conditions that were favorable for organisms during life and which facilitated preservation after death. Limestones, limy shales, and certain types of sandstones are typically deposited under such conditions.

One should look particularly for areas where rocks formed from marine sediments lie relatively flat and have not been greatly disturbed by heat, pressure, and other physical or chemical changes. If the rocks appear to have undergone considerable folding and fracturing, there is great likelihood that any fossils that were present have been destroyed or damaged by this action.

Quarries are good places to look but one should be sure to obtain permission before entering.Rockexposures in quarries are rather fresh but have undergone some weathering. Quarries have been opened in many of the limestone formations of Texas, and large numbers of fine specimens have been collected in some of these excavations. Certain LowerCretaceouslimestones are useful for road metal, building stone, or in the manufacture of portland cement, and extensive quarrying has been undertaken in the Edwards Plateau region of Texas (Pl. 9). Bones and petrified wood are frequently found in sand and gravel quarries in many parts of the State.

Particular attention should be given to all railroad and highway cuts as rocks exposed in this way are usually still in their original position and are fairly well weathered. Cuts made by recent construction are usually more productive after they have undergone aperiodof weathering as this helps to separate the fossils from their enclosing rocks.

Gullies, canyons, and stream beds are also good places to examine. These areas are continually subjected to the processesof erosion or stream action, and new material is uncovered year after year.

If there are abandoned coal mines nearby, the dumps of wasterockaround the mine shafts could be checked. A careful examination of such waste may reveal fine specimens of well-preserved plant fossils.

Coal has been mined in several parts of Texas, and abandoned shafts or dumps are still present in some counties. The bituminous coals of Texas are predominantlyPennsylvanianin age, and mining has been carried on in the following counties: Eastland, Erath, Jack, Palo Pinto, Parker, Wise, Young.

When a likely collecting spot has been located, the ground should be examined very carefully to see if there are anyrockfragments which contain pieces of shell or the imprints of leaves or other organisms.

If the fossils have been freed by weathering, they can be easily picked up and placed in the bag. Many times, however, it will be necessary to take the hammer and very carefully remove the surroundingrock. Smaller specimens may be more safely freed with the careful use of the proper size chisel by gently tapping the chisel and gradually chipping away thematrix—the rock that is holding the specimen. After most of the matrix has been removed, thefossilshould be carefully wrapped and placed in the collecting bag.

Before leaving a collecting locality, one should be sure to record its geographic location and thegeologic ageof therockin which the fossils were found. The place should be located on the map and the locality entered in the notebook in such a manner that it could easily be located again for additional collecting. If a county ortopographic mapis available, it is wise to mark the locality on the map. The geographic and geologic data should be written on a label placed in the bag of fossils collected at that particular locality. In addition, many collectors find it helpful to write the locality on the outside of each bag of fossils.

Material from separate localities should be kept in individual cloth or paper bags, and the collector should take every precaution to keep the labels with their respective fossils. Remember thatafossilwithout a locality is hardly worth the paper it is wrapped in.

The collector shouldalwaysask the land owner’s permission before entering or collecting on private property. One should respect all property, especially livestock and fences, and leave the area cleaner than when entered. If these precautions are observed, future collectors will probably be welcome to return for additional collecting.

It is usually necessary to do the final cleaning and preparation of fossils at home or in the laboratory, for most fossils brought in from the field require considerable preparation before they are ready for display.

Excess matrix should be carefully removed with hammer and chisel; blows should always be directed away from thefossil. Smaller tools (needles, tweezers, and awls) should be used in the final preparation stage, and one should work carefully to avoid damaging the specimen. Before starting the final cleaning, it will be helpful to place the fossils in water and let them soak overnight. This will loosen much of the excessrock, and most of the softer material can then be removed with a small scrub brush or tooth brush. Mounted needles can be used to clean more delicate specimens or around the smaller structures of larger fossils. It may be advisable to use the magnifying glass when working with small fossils or with delicate surface structures of larger specimens.

Broken fossils can be repaired with clear plastic household cement, and specimens that are crumbling may be coated with pure white shellac, thinned collodion, or clear nail polish. The latter is preferred as it is not as likely to crack. Fragments of bone are particularly apt to crumble upon exposure to the air. This type offossilis normally quite fragile and should be excavated with great care and shellaced as soon as dry.

Dilute hydrochloric acid may be used in removing silicified fossils from acalcareousmatrix. The material to be etched should be placed in a pottery or glass container and covered with water. Acid should then be added to the water very slowly and until large numbers of bubbles are given off. Each time the bubbling ceases, more acid should be added and this process should be repeated until thefossilis free of matrix. This procedure should be carried on in a well-ventilated place, and the acid should be handled with extreme caution. Hydrochloric acid can cause damage or serious injury and the fumes are extremely corrosive.

In order to get the maximum pleasure out offossilcollecting, most amateur paleontologists want to identify and classify the fossils that they have collected. This requires some knowledge of how fossils are classified and how they receive their scientific names.

The number of organisms, both living and extinct, is so great that somesystemof classification is needed to link them all together. Many fossils bear distinct similarities to plants and animals that are living today, and for this reason paleontological classification is similar to that used to classify modern organisms. This system, known as the system ofbinomial nomenclature, was first used consistently in 1758 by Linné (or Linnaeus), an early Swedish naturalist.

Scientific names established in accordance with the principles ofbinomial nomenclatureconsist of two parts: thegeneric(orgenus) name and thetrivialname. These names are commonly derived from Greek or Latin words which are usually descriptive of the organism orfossilbeing named. They may, however, be derived from the names of people or places, and in such instances the names are always Latinized. Greek or Latin is used because they are “dead” languages and not subject to change. They are also “international” languages in that scientists all over the world can use the same names regardlessof what language they write in. Thesystemof binomial nomenclature has led to the development of the science oftaxonomy, the systematic classification and naming of plants and animals according to their relationships.

The world of organic life has been divided into the plant and animal kingdoms. These kingdoms have been further divided into larger divisions calledphyla(from the Greek wordphylon, a race). Eachphylumis composed of organisms with certain characteristics in common. For example, all animals with a spinal cord (or notochord) are assigned to the phylum Chordata.

Thephylumis reduced to smaller divisions calledclasses, classes are divided intoorders, orders intofamilies, families intogenera, and each genus is divided into still smaller units calledspecies. A species may be further reduced to subspecies, varieties, or other subspecific categories, but these need not concern us in a publication of this nature.

The following table illustrates the use ofbinomial nomenclaturein the classification of man, a clam, and a dog.

The generic name and thetrivial nameconstitute thescientific nameof aspeciesand according to thissystemof classification the scientific name of all living men isHomo sapiens. It is obvious that there are many variations among individual men, but all men have certain general characteristics in common and are therefore placed in the same species.

In a scientific name, the generic name is always started with a capital letter and thetrivial namewith a small letter. Both names must be italicized or underlined.

The name of the author (the person who first described thefossil) usually appears following the scientific name. The date of the scientific publication containing the original description of the fossil is often placed after the author. For example:

Turrilites worthensisAdkins and Winton 1920

With the large numbers of plants and animals that are living today, plus those of the past, random naming would result in much confusion. For this reason scientists have established strict rules that must be followed when a specimen is named. The strict application of these rules enables scientists in all parts of the world to assign scientific names without fear of duplication.

The beginning collector is usually content to know if his specimen is a clam or a snail or a fern or a palm leaf. But as the collection grows, it becomes increasingly desirable to know the scientific name of eachfossil.

When he starts to identify fossils it may be helpful to show them to a geology teacher if a college or university is nearby. Most teachers are glad to be of help and will probably have similar specimens in their own collections. As all colleges do not have geology departments, a list of institutions with geologists on their faculties is included at the end of this section of the handbook (p. 27). In addition, many of the science teachers in the public schools are familiar with fossils and can give helpful suggestions as to how to classify material.

Museums are also good places from which to get help. If the museum has a geological collection, it will be most helpful to compare specimens with the fossils in their collections and to ask the museum personnel for advice. In addition to the above sources of information, local professional geologists are usually familiar with the geology of the local area and the paleontological literature of the region.

Possibly local librarians can recommend books, encyclopedias, or other publications that will be of help. Members of a localrockand mineral club, if one is available, are another source of information. Many times these collectors can pass along good ideas and tell exactly which books to consult.

After books or journals describing the fossils of the area have been located, the collected specimens should be closely compared with any illustrations that are shown. Eachfossilshould be examined carefully, its more characteristic features noted, and it should again be compared with the illustrations and descriptions in the book. Thephylumor class to which the specimen belongs should be determined first. For example, the genus andspeciesof a certain fossil may not be known, but it looks like a snail and accordingly it is named agastropod(for class Gastropoda, the snail class), and this is, at least, a start in determining the scientific name of that particular fossil. The descriptive material in the text of each reference will usually point out the more detailed features which will be diagnostic of the genus or species.

The illustrations and descriptive material in this publication will also be of considerable help in identification. Many illustrations of the more common invertebrate fossils have been included, but the publication was not designed primarily for use infossilidentification. Rather, it is intended to guide the amateur or student who is interested in fossil collecting, and to furnish suggestions as to how collecting may be more effectively pursued.

Fossilidentification keys may be useful in helping the beginning collector identify specimens. The collector compares a fossil with the key description and eliminates those characters that do not fit the specimen.

The key used in this handbook is based primarily onsymmetry—the orderly arrangement of the parts of an object with reference to lines, planes, or points. The shape of the shell or body, presence or absence of coiling, and presence or absence of body partitions are also useful criteria in identifying fossils. To use thekey the beginner should know something about symmetry. Two major types of symmetry are used in this key.

1.Radial symmetry—the symmetrical repetition of parts around an axis. This is thesymmetryof a wheel, and any vertical section through the center of the object divides it into symmetrical halves (fig. 4a).2.Bilateralsymmetry—the symmetrical duplication of parts on each side of a plane (fig. 5). The plane divides the object into two halves that are mirror images of each other. This is the symmetry of a plank.

2.Bilateralsymmetry—the symmetrical duplication of parts on each side of a plane (fig. 5). The plane divides the object into two halves that are mirror images of each other. This is the symmetry of a plank.

It should be noted that many objects may have both kinds ofsymmetry. For example: A cone when viewed from the top hasradial symmetryand when viewed from the side showsbilateralsymmetry (fig. 4a, b).

Fig. 4.Types ofsymmetryin afossilcoral. (a) Radial symmetry. (b)Bilateralsymmetry.

Fig. 5.Bilateralsymmetryas displayed by a typicalfossilbrachiopod.

An illustration of the use of the key on pages26-27 follows. Assuming that a specimen displaysradial symmetry, this means that it belongs under Part I on the key. If thefossilhas a tapering, cylindrical, cone-shaped shell (“A” on the key), the subheadings under the “A” part of the key are examined. Should the specimen have a shell which is round, tapering at one end, withtransversesepta or sutures (number 2 under “A”), it is probably acephalopod. This is indicated on the right hand side of the page. Number 1 under “A” is eliminated because the fossil did not havelongitudinalradial partitions within the shell.

Some fossils display no apparentsymmetryand such afossilwould be referred to Part III of the key. If this fossil had internaltransversepartitions “A” would be eliminated. If the fossil was not a coiled fossil “B” would also be eliminated and we would proceed directly to “C”—uncoiled fossils. If the specimen is a branching twig-like fossil, numbers 1, 2, and 3 would be eliminated and the specimen referred to number 4 (Branching twig-like fossils). Should the specimen have evenly distributed relatively large openings with radiallongitudinalpartitions or septa, the specimen is probably acolonialcoral(“b” under number 4 on the key). The “a” part of number 4 would be eliminated because the coral had large openings and radial longitudinal septa.

Once a tentative identification has been made from the key, pictures and descriptions of thisfossilgroup are examined to establish a more precise identification. It should be remembered that keys are not perfect, and the collector should not expect to be able to identify every specimen with this key.

(Instructions on pages23-25 for use of key)

Plate 6FossilIdentification ChartIRADIAL SYMMETRY

Plate 7FossilIdentification ChartIIBILATERALSYMMETRY

Back to Index Next