Chapter V: Introduction (4)

Mammals first appeared in the Jurassic and were probably derived from some form of mammal-like reptile. Although rare during the Mesozoic, mammals underwent rapid development and expansion during the Cenozoic, and during this era certain types of mammals became extremely large and assumed many bizarre shapes. The majority of these unusual forms lived but a short time but are well known from their fossils, and the remains of some of these animals which inhabited Texas during the Cenozoic may be seen in the Texas Memorial Museum at Austin.

Recent mammalian classification recognizes several subclasses and numerous orders and suborders, but the treatment of the mammals in a publication of this nature must of necessity be somewhat brief and no attempt at detailed classification is made.

Subclass Allotheria.—

The allotherians first appeared during the Jurassic and underwent considerable development in the late Cretaceous and early Tertiary. Included in this subclass are the _multituberculates_ which are a group of small rodent-like animals that were probably the earliest of the herbivorous mammals. These animals were probably never very numerous, and they became extinct during the early part of Eocene time.

Subclass Theria.—

Members of this subclass are first known from rocks of Jurassic age, and they constitute the largest group of mammals that are living today. Therians undergo considerable development before they are born and at birth typically resemble the fully developed animal. This subclass has been divided into several orders but only the more important ones are discussed here.

Order Edentata.—

The edentates are a rather primitive group of mammals which are represented by such living forms as the anteaters, tree sloths, and armadillos. Members of this group were common in the southern part of the United States in Pleistocene and Pliocene time, and fossil edentates have been reported from rocks of this age in Texas. One such form was _Mylodon_ (Pl. 46), one of the extinct giant ground sloths. These huge sloths were quite heavy and some of them stood as much as 15 feet tall; these great creatures were the forerunners of the modern tree sloths of South America. The mounted skeleton of one of these giant ground sloths is displayed in the Texas Memorial Museum.

ENTELODONT × ¹/₃₅
GLYPTODON × ¹/₅₀
MYLODON × ¹/₉₀

Another interesting representative of this order was the glyptodont. These peculiar mammals, which were ancestral to the present-day armadillos, developed at about the same time as the ground sloths. _Glyptodon_ (Pl. 46), a typical glyptodont that has been reported from the Pleistocene of Texas, is quite characteristic of this group. This armadillo-like beast had a solid turtle-like shell that in some forms was as much as 4 feet high. From the front of the bone capped head to the tip of its tail, a large individual might be as much as 15 feet long. The thick heavy tail was protected by a series of bony rings, and in some species the end of the tail was developed into a bony heavily spiked club. The _carapace_ (hard outer shell) of a large glyptodont is mounted at the Texas Memorial Museum.

Order Carnivora.—

Animals belonging to this order are called carnivores and are characterized by clawed feet and by teeth which are adapted for tearing and cutting flesh. The carnivores, or meat-eaters, were first represented by an ancient group of animals called _creodonts_, and this short-lived group first appeared in the Paleocene and were extinct by the end of the Eocene. They ranged from the size of a weazel to that of a large bear, and their claws were sharp and well developed. Their teeth, however, were not as specialized as those of modern carnivores, and the creodont brain was relatively small. It is assumed that these animals had a very low order of intelligence when compared to the more advanced carnivores of today.

These early meat-eaters were followed by more specialized carnivores which developed throughout Cenozoic time. Some examples of these are the saber-tooth cat _Dinobastis_ (Pl. 47) and the dire wolf _Canis diris_ (Pl. 47), both of which have been reported from the Texas Pleistocene. Some remains of these unusual forms, representing the cat and dog families, are on display at the Texas Memorial Museum.

Order Pantodonta.—

Pantodonts, known also as _amblypods_, were primitive, hoofed, herbivorous animals. They were distinguished by a heavy skeleton, short stout limbs, and blunt spreading feet. The pantodonts appeared first during Paleocene time and had become extinct by the end of the Oligocene.

Order Dinocerata.—

The members of this order are an extinct group of gigantic mammals commonly called _uintatheres_. _Uintatherium_ (Pl. 48), which is typical of the group, had three pairs of blunt horns, and the males had dagger-like upper tusks. Some of the uintatheres were as large as a small elephant and stood as much as 7 feet tall at the shoulders. The size of the brain in relation to the size of the body suggests that these animals were not as intelligent as most mammals. Uintatheres are known from rocks ranging from Paleocene to Eocene in age. Uintathere remains have been reported from Big Bend National Park in Trans-Pecos Texas.

Order Proboscidea.—

The earliest proboscideans, the elephants and their relatives, first appeared in the late Eocene of Africa and were about the size of a small modern elephant but had larger heads and shorter trunks. Proboscidean development is marked by an increase in size, change in skull and tooth structure, and elongation of the trunk. Two well-known fossil proboscideans are the _mammoth_ and the _mastodon_, both of which inhabited Texas during Pleistocene time. The mastodons resembled the elephants, but the structure of their teeth was quite different (fig. 25). Moreover, the mastodon skull was lower than that of the elephant and the tusks were exceptionally large—some reaching a length of 9 feet.

DINOBASTIS × ¹/₂₀
CANIS DIRUS × ¹/₁₅
HYRACOTHERIUM × ¹/₁₀
PLIOHIPPUS × ¹/₂₀

There were several types of mammoths, and the _woolly mammoth_ is probably the best known. This animal lived until the end of the Pleistocene and, like the woolly rhinoceros discussed below, is known from ancient cave paintings and frozen remains. Information gathered from these sources indicates that this great beast had a long coat of black hair with a woolly undercoat (Pl. 49).

During the Pleistocene, mammoths were widespread over the United States, and their remains are abundant in many stream deposits of this age. Proboscidean bones have been reported from Pleistocene rocks in many parts of Texas, where they are commonly found in sand and gravel pits.

Order Perissodactyla.—

The perissodactyls, or odd-toed animals, are mammals in which the central toe on each limb is greatly enlarged. Modern representatives include the horses, rhinoceroses, and tapirs. Extinct members of the Perissodactyla include the _titanotheres_, _chalicotheres_, and _baluchitheres_, all of which grew to tremendous size and took on many unusual body forms.

HORSES.—

One of the first perissodactyls was _Hyracotherium_ (also called _Eohippus_), which is the earliest known horse (Pl. 47). This small animal, whose remains have been found in Big Bend National Park, was about 1 foot high and his teeth indicate a diet of soft food. Following the first horse, there is a long series of fossil horses which provide much valuable information on the history of this important group of animals.

The record of the development of the horse is well represented in Texas, and the bones and teeth of fossil horses are common in certain parts of the State. Fossils of this type have been reported from the Tertiary of the Trans-Pecos, Gulf Coastal Plain, and High Plains regions of Texas, and the teeth of Pleistocene horses have been found in sand and gravel pits in many parts of the State. Horse teeth (fig. 26) are particularly useful fossils as they may be accurately identified and used to determine the age of the rocks in which they are found.

TITANOTHERES.—

This group of odd-toed mammals appeared first in the Eocene, at which time they were about the size of a sheep. By Middle Oligocene time they had increased to gigantic proportions but still had a small and primitive brain. _Brontotherium_ (Pl. 48) was slightly rhinoceros-like in appearance and is believed to be the largest land animal that ever inhabited the North American continent. This animal was about 8 feet tall at the shoulders; a large bony growth protruded from the skull and this was extended into a flattened horn, which was divided at the top.

UINTATHERIUM × ¹/₄₅
BRONTOTHERIUM × ¹/₃₅

Although the titanotheres underwent rapid development during the early Tertiary, these huge beasts became extinct during the middle of the Oligocene epoch. Titanothere remains have been reported from the Trans-Pecos region of Texas.

CHALICOTHERES.—

The chalicotheres were in some ways like the titanotheres, but they also exhibited many peculiarities of their own. The head and neck of _Moropus_, a typical chalicothere, were much like that of a horse, but the front legs were longer than the hind legs, and the feet resembled those of a rhinoceros except that they bore long claws instead of hoofs. The chalicotheres lived in North America from Miocene until Pleistocene time but were probably never very numerous, and their remains have not yet been discovered in Texas.

RHINOCEROSES.—

The rhinoceroses are also odd-toed animals, and there are many interesting and well-known fossils in this group. The _woolly rhinoceros_ (Pl. 49) was a Pleistocene two-horned form that ranged from southern France to northeastern Siberia. The woolly rhinoceros is well known from complete carcasses recovered from the frozen tundra of Siberia and from remains that were found preserved in an oil seep in Poland. These unusual specimens plus cave paintings made by early man have given a complete and accurate record of this creature. Although the woolly rhinoceros has not been reported from Texas, other fossil rhinoceroses have been found in the High Plains and Gulf Coastal Plain of Texas. These fossils have been found in rocks ranging from Middle Oligocene to late Pliocene in age.

_Baluchitherium_, the largest land mammal known to science, was a hornless rhinoceros that lived in late Oligocene and early Miocene time. This immense creature measured approximately 25 feet from head to tail, stood almost 18 feet high at the shoulder, and must have weighed many tons. Remains of these creatures have not been discovered in North America, and they appear to have been restricted to Central Asia.

Order Artiodactyla.—

The artiodactyls are the even-toed hoofed mammals and include such familiar forms as pigs, camels, deer, goats, sheep, and hippopotamuses. This is a large and varied group of animals, but the basic anatomical structure of the limbs and teeth show well the relationship between the different forms. Artiodactyls are abundant fossils in rocks ranging from Eocene to Pleistocene in age and are common in rocks of this age in Texas.

ENTELODONTS.—

These giant pig-like artiodactyls lived during Oligocene and early Miocene time and were distinguished by a long heavy skull that held a relatively small brain. The face was marked by large knobs which were located beneath the eyes and on the underside of the lower jaw, and although these knob-like structures were blunt they had the appearance of short horns. Certain of these giant swine attained a height of 6 feet at the shoulders and had skulls that measured 3 feet in length (Pl. 46). Entelodont remains have been found in the Miocene of the Texas Coastal Plain.

CAMELS.—

The first known camels have been reported from rocks of upper Eocene age, and these small forms underwent considerable specialization of teeth and limbs as they developed in size. Many of the camels that lived during the middle Cenozoic had long legs which were well adapted to running and long necks which would have allowed the animals to browse on the leaves of tall trees.

The earliest known Texas camels were found in rocks of Oligocene age, and camels, like horses, must have been abundant in Texas during the Pleistocene for their fossilized remains are common in many parts of the State.

WOOLLY RHINOCEROS × ¹/₂₀
WOOLLY MAMMOTH × ¹/₄₀

BOOKS ABOUT FOSSILS

The following books are recommended for the reader who wants to know more about fossils and fossil collecting. The publications listed below cover various phases of historical geology and paleontology and range from children’s books to the more technical publications of the professional paleontologist. This list, however, is by no means all-inclusive and many other interesting and useful publications are available.

GENERAL WORKS

Dunbar, C. O. (1959) Historical geology, John Wiley and Sons, New York.

College-level text, well written and well illustrated.

Moore, R. C. (1958) Introduction to historical geology, McGraw-Hill Book Co., New York.

College-level presentation of earth history. Many illustrations of
fossils.

Moore, Ruth (1953) Man, time, and fossils, Alfred Knopf, New York.

A readable account of fossils and their development throughout
geologic time.

Panghorn, M. W., Jr. (1957) Earth for the layman, American Geological Institute, Washington, D. C.

Contains many valuable references.

Raymond, P. E. (1950) Prehistoric life, Harvard University Press, Cambridge, Mass.

College-level text.

Richards, H. G. (1953) Record of the rocks, Ronald Press, New York.

College-level earth history text.

Simpson, G. G. (1953) Life of the past, Yale University Press, New Haven, Conn.

Thorough, yet readable, introduction to paleontology.

Stirton, R. A. (1959) Time, life, and man: the fossil record, John Wiley and Sons, New York.

An introductory college text, most of which is of interest to adult
level general readers.

Note: _See also_ sections on Paleontology and Fossils _in_ Encyclopedia Americana, Encyclopaedia Britannica, and others.

NONTECHNICAL AND JUVENILE

Andrews, R. C. (1953) All about dinosaurs, Random House, New York.

Interesting and readable dinosaur book for junior high and high-school
age.

Andrews, R. C. (1956) All about strange beasts of the past, Random House, New York.

Interesting and easy to read, this book deals largely with extinct and
unusual mammals (junior high and high school).

Colbert, E. H. (1945) The dinosaur book, American Museum of Natural History, New York.

A classic among “popular” dinosaur books. For all age levels.

Colbert, E. H. (1957) Dinosaurs, American Museum of Natural History, New York.

This little booklet provides a well-illustrated introduction to the
dinosaurs. For high school and adult-level readers.

Dickinson, Alice (1954) First book of prehistoric animals, Franklin Watts, Inc., New York.

Easy to read, well-illustrated book for grade-school age.

Dunkle, D. H. (1957) The world of the dinosaurs, Smithsonian Institution, Washington, D. C.

An easy to understand, amply illustrated introduction to the dinosaurs
(high school-adult level).

Fenton, C. L. (1937) Life long ago, The John Day Co., New York.

Very good for advanced grade and high-school age.

Heal, Edith (1930) How the world began, Thomas S. Rockwell Co., Chicago.

An account of the beginnings of life. For upper grade through
high-school age.

Markman, H. C. (1954) Fossils, Denver Museum of Natural History, Denver, Colo.

A well-illustrated general survey of fossils. For adult-level readers.

Matthews III, W. H. (1962) Fossils: An introduction to prehistoric life, Barnes and Noble, Inc., New York, [“In preparation” at time of first printing of Guidebook No. 2.]

This publication contains many collecting aids and much background
material for amateur collectors. Contains also a brief review of earth
history.

Matthews III, W. H. (1963) Wonders of the dinosaur world, Dodd, Mead & Co., New York.

Well illustrated, non-technical presentation of dinosaurs. For
junior-high and high-school teachers.

Parker, B. M. (1942) Stories read from the rocks, Basic Science Education Series, Row, Peterson and Co., Evanston, Ill.

Well written and colorfully illustrated. For advanced grades and
junior high.

Parker, B. M. (1948) Animals of yesterday, Basic Science Education Series, Row, Peterson, and Co., Evanston, Ill.

Well written and colorfully illustrated. For advanced grades and
junior high.

Shaver, R. H. (1959) Adventures with fossils, Geological Survey, Indiana Department of Conservation, Bloomington, Ind.

Collection hints and general information on fossils. Particularly for
the lower grades.

Shuttlesworth, D. E. (1957) Real book of prehistoric life, Garden City Books, Garden City, N. Y.

Survey of prehistoric life. For grade and junior-high levels.

COLLECTING HELPS

Brown, Vinson (1954) How to make a home nature museum, Little, Brown and Co., Boston.

Contains suggestions for collecting, mounting, and displaying fossils
and other objects of nature.

Camp, C. L., and Hanna, G. D. (1937) Methods in paleontology, University of California Press, Berkeley.

Excellent discussion of collecting and preparation techniques.

Casanova, Richard (1957) An illustrated guide to fossil collecting, Natureograph Co., San Martin, Calif.

Has collecting hints and fossil localities for most of the States.

Collinson, C. C. (1959) Guide for beginning fossil hunters, Educational Series 4, Illinois State Geological Survey, Urbana.

Clearly written, well illustrated, particularly for the lower grades.

Goldring, Winifred (1950) Handbook of paleontology for beginners and amateurs, New York State Museum, Albany, N. Y.

A complete summary of paleontology. For the advanced collector.

La Rocque, A., and Marple, M. F. (1955) Ohio fossils, Ohio Division of Geological Survey, Bulletin 54, Columbus, Ohio.

Rather comprehensive treatment of the invertebrates with several
useful keys for fossil identification.

Livingston, V. E., Jr. (1959) Fossils in Washington, Division of Mines and Geology, Department of Conservation, Olympia, Wash.

An introduction to the geology and fossils of Washington. Contains
guide to collecting localities.

Simpson, B. W. (1958) Gem trails of Texas, Bessie W. Simpson, Granbury, Texas.

Field guide to Texas mineral, rock, and fossil locations. Contains
numerous maps and well-described collecting localities.

Unklesbay, A. G. (1955) Common fossils of Missouri, University of Missouri Bulletin, Handbook 4, Columbia, Mo.

Written for the amateur; contains much general information of interest
to the beginning collector.

REFERENCE WORKS

Arnold, C. A. (1947) An introduction to paleobotany, McGraw-Hill Book Co., New York.

College-level textbook.

Beerbower, J. R. (1960) Search for the past, Prentice-Hall, Inc., Englewood Cliffs, N. J.

Good background text. Well illustrated. Has section on vertebrates.

Colbert, E. H. (1955) Evolution of the vertebrates, John Wiley and Sons, New York.

Comprehensive and technical treatment of vertebrate fossils.

Cushman, J. A. (1948) Foraminifera, their classification and economic use, Harvard University Press, Cambridge, Mass.

College-level text containing large numbers of descriptions and
illustrations of foraminifera.

Easton, W. H. (1960) Invertebrate paleontology, Harper & Bros., Inc., New York.

College-level text. Good illustrations, useful for identification.

Fenton, C. L., and Fenton, M. A. (1958) The fossil book, Doubleday and Co., New York.

Comprehensive, easy-to-read, beautifully illustrated treatment of all
types of fossils.

Jones, D. J. (1956) Introduction to microfossils, Harper and Brothers, New York.

College-level textbook with considerable information on collection,
preparation, and the types of microfossils.

Moore, R. C., et al. (1953-1959) Treatise on invertebrate paleontology, Geological Society of America and University of Kansas, Lawrence, Kansas.

A technical reference for the more advanced collector. It is issued in
several parts and contains latest classification.

Moore, R. C., Lalicker, C. G., and Fisher, A. G. (1953) Invertebrate fossils, McGraw-Hill Book Co., New York.

College-level reference with fine illustrations. Of value for purposes
of identification.

Romer, A. S. (1945) Vertebrate paleontology, University of Chicago Press, Chicago.

A college-level textbook with numerous illustrations.

Shimer, H. W. (1933) Introduction to the study of fossils, The Macmillan Company, New York.

A relatively simple college-level presentation of plant and animal
fossils.

Shimer, H. W., and Shrock, R. R. (1944) Index fossils of North America, John Wiley and Sons, New York.

Comprehensive survey of the more common fossils of North America.
Useful to the advanced collector and a most useful aid for fossil
identification.

Shrock, R. R., and Twenhofel, W. H. (1953) Principles of invertebrate paleontology, McGraw-Hill Book Co., New York.

Useful college-level reference for advanced collectors.

SELECTED REFERENCES ON TEXAS FOSSILS[2]

*Adkins, W. S. (1920) The Weno and Pawpaw formations of the Texas Comanchean: Univ. Texas Bull. 1856.

Descriptions and illustrations of many common Cretaceous fossils.

*Adkins, W. S. (1928) Handbook of Texas Cretaceous fossils: Univ. Texas Bull. 2838.

Lists all fossils described from the Texas Cretaceous prior to 1928,
with many useful illustrations.

*Adkins, W. S., and Winton, W. M. (1919) Paleontological correlation of the Fredericksburg and Washita formations of north-central Texas: Univ. Texas Bull. 1945.

Contains descriptions and illustrations of many common Lower
Cretaceous fossils of north-central Texas.

Clarke, W. B., and Twitchell, M. W. (1915) The Mesozoic and Cenozoic Echinodermata of the United States: U. S. Geological Survey Monograph 54, Washington, D. C.

A valuable guide to the Mesozoic and Cenozoic echinoderms of Texas.

*Frizzell, D. L. (1954) Handbook of Cretaceous Foraminifera of Texas: Univ. Texas, Bureau Econ. Geol. Rept. Inves. No. 22.

A technical, but invaluable aid in the study of Texas Cretaceous
microfossils.

*Girard, R. M. (1959) Bibliography and index of Texas geology, 1933-1950: Univ. Texas Pub. 5910.

This valuable reference guide contains many references to Texas
fossils. Note especially entries under Paleontology in the index.

Heuer, Edward (1958) Comments on the nomenclature revision of the Strawn and Canyon megafossil plates, _in_ A guide to the Strawn and Canyon Series of the Pennsylvanian System in Palo Pinto County, Texas, An Occasional Publication of the North Texas Geological Society, Wichita Falls, Texas.

Contains illustrations and latest name changes of many of the more
common Pennsylvanian fossils of north Texas.

*King, R. E. (1930) Geology of the Glass Mountains, Part II, Faunal summary and correlation of the Permian formations with description of Brachiopoda: Univ. Texas Bull. 3042.

Contains descriptions and illustrations of numerous brachiopods from
the Glass Mountains of Trans-Pecos Texas.

*Lee, Wallace, et al. (1939) Stratigraphic and paleontologic studies of the Pennsylvanian and Permian rocks of north-central Texas: Univ. Texas Pub. 3801.

Contains an extensive faunal list and important collecting localities
for Pennsylvanian invertebrates.

*Moore, R. C., and Jeffords, R. M. (1944) Description of lower Pennsylvanian corals from Texas and adjacent states: Univ. Texas Pub. 4401, pp. 77-208.

Describes and illustrates many of the more common Pennsylvanian
corals.

*Plummer, F. B. (1943) The Carboniferous rocks of the Llano region of central Texas: Univ. Texas Pub. 4329.

Contains geologic map, locality data, and illustrations of many
Carboniferous fossils.

*Plummer, F. B., and Moore, R. C. (1921) Stratigraphy of the Pennsylvanian formations of north-central Texas: Univ. Texas Bull. 2132.

Describes and illustrates many of the more common Pennsylvanian
fossils of north-central Texas.

*Plummer, F. B., and Scott, Gayle (1937) Upper Paleozoic ammonites in Texas: Univ. Texas Bull. 3701, pt. 1.

*Renick, B. C., and Stenzel, H. B. (1931) The lower Claiborne of the
Brazos River, Texas: Univ. Texas Bull. 3101, pp. 73-108.

Contains discussion and illustrations of many common Tertiary fossils.

Sellards, E. H. (1955) Texas through 250 million years: Museum Notes
No. 4, Texas Memorial Museum, Austin.

This little booklet provides a short geologic history of Texas along with a review of oil in Texas.

*Sellards, E. H., Adkins, W. S., and Plummer, F. B. (1933) The geology
of Texas, Vol. I, Stratigraphy: Univ. Texas Bull. 3232 (August 22,
1932).

This important publication will give the advanced collector much valuable information on the distribution of the rocks of Texas. Complete with geologic map.

Stanton, T. W. (1947) Studies of some Comanche pelecypods and
gastropods: U. S. Geological Survey Prof. Paper 211, Washington, D. C.

Describes and illustrates most of the more common Lower Cretaceous pelecypods and gastropods of the State.

*Stenzel, H. B., Krause, E. K., and Twining, J. T. (1957) Pelecypoda
from the type locality of the Stone City beds (Eocene) of Texas: Univ.
Texas Pub. 5704.

Descriptions and illustrations of many of the more common Tertiary clams and oysters.

*Stephenson, L. W. (1941) The larger invertebrate fossils of the
Navarro group of Texas: Univ. Texas Pub. 4101.

Contains descriptions of many common Upper Cretaceous invertebrates (exclusive of corals and crustaceans).

Stephenson, L. W. (1952) Larger invertebrate fossils of the Woodbine
formation (Cenomanian) of Texas: U. S. Geological Survey Prof. Paper
242, Washington, D. C.

*Winton, W. M. (1925) The geology of Denton County: Univ. Texas Bull. 2544.

Illustrates and discusses the occurrence of many Cretaceous fossils.

*Winton, W. M., and Adkins, W. S. (1920) The geology of Tarrant County: Univ. Texas Bull. 1931.

Contains many illustrations of common north Texas Cretaceous fossils.

GLOSSARY

Amber—a hard, yellowish, translucent, fossilized plant resin.

Ammonite—ammonoid cephalopod with complexly wrinkled suture pattern;
member of subclass Ammonoidea.

Anterior—front or fore.

Anus—the terminal opening of the alimentary canal, through which waste
matter is discarded from the body.

Aperture—the opening of shells, cells, etc.

Aragonite—calcium carbonate (CaCO₃) crystallizing in a different form
than calcite. In shells it is chalky and opaque; is less stable than
calcite.

Archeozoic—the oldest known geological era; early Precambrian time.

Articulated—joined by interlocking processes or by teeth and sockets.

Asymmetrical—without or lacking symmetry.

Bilateral—pertaining to the two halves of a body as symmetrical and
mirror images of each other.

Binomial nomenclature—system of scientific nomenclature requiring two
names: generic and trivial.

Blastoid—stalked echinoderm with bud-like calyx usually consisting of 13
plates; member of class Blastoidea.

Brachiopod—bivalved marine invertebrate; member of phylum Brachiopoda.

Brackish—a mixture of salt and fresh waters.

Burrow—a hole in the ground, rock, wood, etc., made by certain animals
for shelter or while gathering food.

Calcareous—composed of, or containing, calcium carbonate; limy.

Calcite—calcium carbonate (CaCO₃) crystallizing in a different form than
aragonite. In shells it is translucent and more stable than aragonite.

Cambrian—the first (oldest) period of the Paleozoic era.

Calyx—in corals the bowl-shaped depression in the upper part of the
skeleton; in stalked echinoderms that part of the body which contains
most of the soft parts.

Caprinid—a Cretaceous pelecypod that is typically coiled in the form of
a ram’s horn.

Carapace—the hard protective covering that forms the exoskeleton of many
invertebrates; in arthropods it is usually chitinous or
calcaro-chitinous.

Carbonization—the process of fossilization whereby organic remains are
reduced to carbon or coal.

Cast—the impression taken from a mold.

Cenozoic—the latest era of geologic time, following the Mesozoic era and
extending to the present.

Cephalon—the head; in trilobites the anterior body segment forming the
head.

Cephalopod—marine invertebrate with well-defined head and eyes and with
tentacles around the mouth; member of class Cephalopoda, phylum
Mollusca; includes squids, octopuses, pearly nautilus.

Ceratite—an ammonoid cephalopod with suture composed of rounded saddles
and jagged lobes; member of subclass Ammonoidea.

Chert—a cryptocrystalline variety of silica; flint is a variety of
chert.

Chitin—a horn-like substance, found in the hard parts of many animals,
such as beetles, crabs, etc.

Chitinous—composed of chitin.

Cirri—in crinoids, the jointed appendages which branch off the side of
the stem or from the base of some crinoid stems.

Coelenterate—invertebrates characterized by a hollow body cavity, radial
symmetry, and stinging cells; a member of phylum Coelenterata;
includes jellyfishes, corals, sea anemones.

Colonial—in biology refers to the way in which some invertebrates live
in close association with, and are more or less interdependent upon,
each other; colonial corals, hydroids, etc.

Columella—a small column or central axis; in corals the small rod or
axial pillar in the center of the corallite; in gastropods the solid
or perforate pillar formed by the union of the successive coils of a
conispiral shell.

Columnal—one of the disk-shaped segments of a crinoid stalk.

Concentric—having a common center, as circles; refers to shell markings
that are parallel to shell margin.

Concretion—nodular or irregular masses in sedimentary rocks and usually
formed around a central core, which is often a fossil.

Conical—cone-shaped.

Conodont—minute tooth-like fossils found in certain Paleozoic rocks;
their origin is not definitely known, but they may have been part of
some type of extinct fish.

Coral—bottom-dwelling marine invertebrate that secretes calcareous hard
parts; member of class Anthozoa, phylum Coelenterata.

Corallite—the skeleton formed by an individual coral animal; may be
solitary or form part of a colony.

Corallum—the skeleton of a coral colony.

Corona—crown; in echinoids the main part of the skeleton consisting of
symmetrically arranged calcareous plates.

Coprolite—the fossil excrement of animals.

Correlation—the process of demonstrating that certain strata are closely
related to each other or that they are stratigraphic equivalents.

Cretaceous—the third and last period of the Mesozoic era.

Cystoid—an extinct stemmed echinoderm with calyx composed of numerous
irregularly arranged plates; member of class Cystoidea.

Dendritic—resembling a tree, branching.

Dentition—the system or arrangement of teeth peculiar to any given
animal.

Devonian—the fourth oldest period of the Paleozoic era, follows the
Silurian, precedes the Mississippian.

Dip—the angle of inclination which the bedding plane of rocks makes with
a real or imaginary horizontal line.

Distillation—in fossils that process by which volatile organic matter is
removed, leaving a carbon residue.

Dolomite—a mineral composed of calcium magnesium carbonate (CaMg(CO₃)₂).

Dorsal—pertaining to the back.

Echinoderm—a marine invertebrate with calcareous exoskeleton and usually
exhibiting a five-fold radial symmetry; member of phylum
Echinodermata; includes cystoids, blastoids, crinoids, starfishes, and
sea urchins.

Echinoid—bottom-dwelling, unattached marine invertebrate with
exoskeleton of calcareous plates covered by movable spines; member of
class Echinoidea; sea urchins, heart urchins, biscuit urchins.

Endoskeleton—the internal supporting structure of an animal.

Eocene—the next to earliest of the Tertiary epochs, follows the
Paleocene and precedes the Oligocene.

Equivalved—right and left valves subequal and (except for hinge
structures) comprising mirror images of each other.

Evolution—a term applied to those methods or processes and to the sum of
those processes whereby organisms change through successive
generations.

Exoskeleton—an external skeleton, or hard covering for the protection of
soft parts, particularly among invertebrates.

Fault—the displacement of rocks along a zone of fracture.

Fauna—an assemblage of animals (living or fossil) living in a given
place at a given time.

Flank—the side or lateral portion of anything.

Flora—an assemblage of plants (living or fossil) living in a given place
at a given time.

Fold—in brachiopods, a major rounded elevation of shell which affects
both inner and outer shell surfaces.

Foramen—in brachiopods, the opening in the pedicle valve near the beak
where the pedicle extends through the shell.

Foraminifer—a protozoan usually possessing a calcareous, perforated,
chambered shell, but shell may be chitinous or agglutinated; a member
of the order Foraminifera, phylum Protozoa.

Formation—a rock unit useful for mapping and distinguished primarily on
the basis of lithologic characters.

Fossil—the remains or traces of organisms buried by natural causes and
preserved in the earth’s crust.

_Guide fossil_—a fossil which, because of its limited vertical but wide
horizontal distribution, is of value as a guide or index to the age of
the rocks in which it is found.

Fossiliferous—containing fossilized organic remains.

Fusulinid—a spindle-shaped foraminifer: test shaped like a grain of
wheat.

Gastrolith—highly polished well-rounded pebbles found associated with
certain reptilian fossils; “stomach stones.”

Gastropod—a terrestrial or aquatic invertebrate, typically possessing a
single-valved, calcareous, coiled shell; member of class Gastropoda,
phylum Mollusca: snails and slugs.

Geologic age—the age of an object as stated in terms of geologic time
(e.g., a Pennsylvanian fern, Cretaceous dinosaur).

Geologic map—map showing distribution of rock outcrops, structural
features, mineral deposits, etc.

Geologic range—the known duration of an organism’s existence throughout
geologic time (e.g., Cambrian to Recent for brachiopods).

Glauconite—a greenish mineral commonly formed in marine environments and
essentially a hydrous silicate of iron and potassium.

Goniatite—an ammonoid cephalopod with suture composed of smooth saddles
and simple angular lobes; member of subclass Ammonoidea.

Graptolite—an extinct, marine, colonial organism with chitinous hard
parts; believed to belong to subphylum Hemichordata of phylum
Chordata.

Guide fossil—see Fossil.

Habitat—the physical environment in which an organism lives.

Hinge-line—in brachiopods, the edge of the shell where the two valves
articulate; in pelecypods, the dorsal margin of the valve which is in
continual contact with the opposite valve.

Igneous rock—rocks which have solidified from lava or molten rock called
magma.

Index fossil—see Fossil.

Inequivalved—opposite valves unlike in shape or size, or both.

Jurassic—second oldest period of the Mesozoic; follows the Triassic,
precedes the Cretaceous.

Keel—a strong continuous ridge along the ventral side of ammonites.

Larva—the young form of some animals before they assume the mature
shape.

Lateral—side or to the side.

Lithology—the study and description of rocks based on the megascopic
(with the naked eye) examination of samples. Used also to refer to the
texture and composition of any given rock sample.

Living chamber—in mollusks, that part of the shell which is occupied by
the living animal.

Lobe—in cephalopods, the backward flexure of the suture or septum.

Longitudinal—in a direction parallel with the length.

Lophophore—in brachiopods, a tentacle-bearing appendage attached to the
anterior surface of the mantle cavity.

Mantle—in mollusks and brachiopods, a layer of tissue containing cells
that secrete the shell.

Meso-—a prefix signifying middle.

Mesozoic—that era of geologic time that precedes the Cenozoic and
follows the Paleozoic.

Miocene—fourth oldest epoch of the Tertiary period; follows the
Oligocene, precedes the Pliocene.

Mississippian—fifth oldest period of the Paleozoic: follows the
Devonian, precedes the Pennsylvanian.

Multicellular—composed of more than one cell.

Nacreous—pearly.

Node—a knob.

-oid—a suffix meaning “in the form of.”

Oligocene—the third oldest epoch of the Tertiary period: precedes the
Miocene, follows the Eocene.

Operculum—the lid or covering of the aperture of certain shells.

Oral—referring to the mouth or aperture.

Orbitoidids—foraminifers with large typically disk-shaped tests.

Ordovician—second oldest period of the Paleozoic era; follows the
Cambrian, precedes the Silurian.

Ossicle—loosely used as a small plate.

Paleocene—oldest epoch of the Tertiary period; precedes the Eocene.

Paleozoic—that era of geologic time that follows Precambrian time and
precedes the Mesozoic era.

Pedicle opening (pedicle foramen)—see Foramen.

Pelecypod—a bivalved aquatic invertebrate; member of class Pelecypoda,
phylum Mollusca.

Pennsylvanian—the sixth oldest period of the Paleozoic era; follows the
Mississippian, precedes the Permian.

Period—a division of geologic time (Pl. 1).

Periostracum—the horny outer covering or epidermis on shells.

Permian—seventh and last period of the Paleozoic.

Permineralization—that process by which mineral matter has been added to
the original shell material by precipitation in the interstices rather
than replacing the original shell material.

Phosphatic—containing or pertaining to phosphate minerals.

Phylum—one of the primary divisions of the animal or vegetable kingdoms.

Planispiral—shell coiled in one plane.

Pleistocene—earliest epoch of Quaternary period, Cenozoic era; follows
Pliocene epoch of Tertiary period, precedes Recent epoch of
Quaternary.

Pleural—referring to the side or ribs; in trilobites, refers to lateral
portions of thorax and pygidium.

Pliocene—latest epoch of Tertiary period of Cenozoic era; follows
Miocene epoch and precedes Pleistocene epoch of Quaternary period.

Polygonal—many sided or having many-sided plates.

Polyp—a many-tentacled aquatic coelenterate animal, typically
cylindrical or cup-shaped, as in corals.

Porcelaneous—like porcelain.

Pore—a very small opening.

Posterior—situated behind; to the rear.

Precambrian—that portion of geologic time before the Cambrian; divided
into Archeozoic era (Early Precambrian) and Proterozoic era (Late
Precambrian).

Protero—combining form meaning fore, former, or anterior in time (Greek
_proteros_, fore).

Proterozoic—youngest era of the Precambrian; follows the Archeozoic era
and precedes the Cambrian period of the Paleozoic era.

Protista—the organic kingdom including the simplest of all one-celled
organisms which possess various characters of both plants and animals;
bacteria, algae, foraminifers, radiolarians.

Protoconch—in mollusks, the initial chamber of shell.

Pyrite—a hard, brass-yellow mineral composed of iron sulfide; “fool’s
gold.”

Quaternary—the youngest period of the Cenozoic era, follows the Tertiary
period.

Radial symmetry—see Symmetry.

Reef—a mound-like or ridge-like elevation of the sea bottom which almost
reaches the surface of the water, composed primarily of organic
material and commonly formed by reef-building animals, such as corals
and oysters.

Replacement—type of fossilization whereby hard parts of organisms are
removed by solution accompanied by almost simultaneous deposition of
other substances in the resulting voids; mineralization.

Respiration—the process of oxygenation.

Rock—an aggregation of one or more minerals.

Rock-unit—divisions of rocks based on definite physical and lithologic
characteristics and not defined on the basis of geologic time alone;
groups, formations, members.

Rudistid—a Cretaceous pelecypod that does not exhibit the typical clam
or oyster shape; many are cone-shaped, resembling corals.

Saddle—in cephalopods, the forward flexure (curved toward the aperture)
of the suture or septum.

Scaphopod—an exclusively marine mollusk with a single-valved tusk-shaped
shell; member of class Scaphopoda, phylum Mollusca.

Scavenger—an animal that feeds on organic refuse.

Sedentary—stationary in life, not moving from place to place.

Sediment—material that has been deposited by settling from a
transportation agent such as water or air; typically composed of
weathered rock fragments.

Sedimentary rock—rocks formed from the accumulation and lithification of
sediments.

Segment—one of the parts into which a body naturally separates or is
divided; for example, segments of arthropods or annelid worms.

Septal—pertaining to the septum.

Septum (plural, septa)—a dividing wall or partition; in fusulinids, a
partition between chambers in the fusulinid shell; in corals, one of
the radiating, longitudinal, calcareous plates located within the
corallite; in cephalopods, the transverse partitions between the
chambers.

Series—the rocks formed during an epoch; the time-stratigraphic term
next in rank below a system.

Serrate—notched like a saw.

Sessile—animal attached to the sea floor more or less permanently.

Silica—an oxide of silicon (SiO₂).

Siliceous—containing or pertaining to silica.

Silicification—the process of combining or impregnating with silica.

Silurian—the third oldest period of the Paleozoic era; follows the
Ordovician, precedes the Devonian.

Sinus—an elongate depression on brachiopod shells.

Siphuncle—in cephalopods, the segmented horny or calcareous tube which
extends from the protoconch to the living chamber.

Slickensides—polished and grooved surfaces that are the result of two
rock masses sliding past each other as in faulting.

Solitary—living alone; not part of a colony.

Species—one of the smaller natural divisions in classification.

Specific name—see Trivial name.

Spicule—a minute spike or dart, skeletal element in sponges and
holothurians.

Stratum (plural, strata)—a single bed or layer of rock.

Strike—the direction of a real or imaginary line that is formed by the
intersection of a bed or stratum with a horizontal plane; strike is
perpendicular to the dip.

Subconical—less than conical in shape; almost a cone.

Suture—the line of junction between two parts; in crinoids, the line of
junction between two plates; in gastropods, the line of junction of
the whorls as seen on the exterior of the shell; in cephalopods, the
line of junction between a septum and the shell wall.

Symmetry—orderly arrangement of parts of an object with reference to
lines, planes, or points.

_Bilateral symmetry_—the symmetrical duplication of parts on each side
of a vertical anterior-posterior plane.

_Radial symmetry_—the symmetrical repetition of parts around a common
vertical dorso-ventrally disposed axis.

_Pentamerous symmetry_—symmetry arranged in a pattern of fives.

System—the rocks formed during a period; the time-stratigraphic term
next in rank above a series.

Taxonomy—that branch of science that deals with classification,
especially in relation to plants, animals, or fossils.

Tertiary—the oldest period of the Cenozoic era; follows the Cretaceous
period of the Mesozoic and precedes the Quaternary period of the
Cenozoic.

Test—the protective covering of some invertebrate animals.

Theca—a sheath or case; in coelenterates, the bounding wall at or near
the margin of the exoskeleton; in echinoderms, the main body skeleton
(or calyx) which houses the animal’s soft parts; in graptolites, any
cup or tube of the colony.

Thorax—in trilobites, that part of the body between the cephalon and
pygidium.

Time-unit—a portion of continuous geologic time (e.g., eras, periods,
epochs, and ages).

Time-rock unit—same as time-stratigraphic unit.

Time-stratigraphic unit—term given to rock units with boundaries
established by geologic time; strata deposited during definite
portions of geologic time (e.g., systems, series, stages, etc.).

Topography—the physical features or configuration of a land surface.

Topographic map—a map showing the physical features of an area,
especially the relief and contour of the land.

Transverse—at right angles to length.

Triassic—the youngest period of the Mesozoic era; follows the Permian
period of the Paleozoic and precedes the Jurassic period of the
Mesozoic.

Trilobite—an extinct marine arthropod having a flattened segmented body
covered by a hardened dorsal exoskeleton divided into three lobes.

Trivial name—the Latinized name added to a generic name to distinguish
the species; same as specific name.

Type locality—the geographic location at which a formation was first
described and from which it was named; or from which the type specimen
of a fossil species comes.

Type specimen—the individual or specimen on which the original
designation of a species was established.

Umbilicus—an external depression or opening at the center of many
loosely coiled shells; in gastropods it is usually located at the base
of the shell; in cephalopods it is usually located laterally.

Umbo—the arched part of the valve near the beak in bivalve shells.

Unicellular—composed of one cell.

Valve—the one or more pieces comprising the shell of animals.

Variety—a subdivision of a species, designated by a third name when a
variety is designated.

Ventral—pertaining to the abdomen; as opposed to dorsal, pertaining to
the back.

Vertebrate—an animal having a backbone or spinal column.

Whorl—a single turn or volution of a coiled shell.

-zoic—combining form meaning “life” (Greek _zoikos_, life).

Zooecium (plural, zooecia)—tube or chamber occupied by an individual of
the bryozoan colony; also called an autopore.

Footnotes

[1]Associate Professor of Geology, Lamar State College of Technology,
Beaumont, Texas.

[2]Entries marked with asterisk are published by the Bureau of Economic
Geology, The University of Texas, Austin. Those not out of print are
distributed at nominal sale price; list sent on request. These
publications may be consulted at many public libraries and/or
Chamber of Commerce offices.

Index

Page numbers in italics indicate illustrations.

A
_Acanthoceras_: 77
_Actinomma_: 49
Africa: 87
Agnatha: 87
Alaska: 7
_Alectryonia lugubris_: 68
algae: 44, 46, 47
“algal biscuits”: 44
alligators: 95
_Allorisma_: 67
_Allosaurus_: 90, 97, 98
Allotheria: 100
allotherians: 100
Amarillo College: 27
amber: 7
amblypods: 102
_Ambocoelia_: 57
_Amelanchier_: 48
American Museum of Natural History: 2, 15, 96
ammonites: 11, 75, 76, 77, 78
Ammonoidea: 66
ammonoids: 75, 76, 77, 78
Amphibia: 89
amphibians: 87, 92
Amphineura: 56
_Amphiscapha_: 61
_Ancilla_: 64
_Angulotreta_: 55, 56
ankylosaurs: 90, 97, 99
Annelida: 78
annelids: 78
_Anomia_: 74
anteaters: 100
Anthozoa: 49, 51
_Apsotreta_: 55, 56
aragonite: 11
_Archelon_: 91
_Archetectonica_: 64
_Archaeopteryx_: 100
Archeozoic, derivation and pronunciation: 33
Archer County: 89
_Archimedes_: 54
_arietina, Exogyra_: 70
Aristotle: 3
Arizona: 7
Arkansas: 37
Arlington State College: 1, 27
armadillos: 100, 102
Aronow, Saul: 1
Arthropoda: 78, 79, 80
arthropods: 10, 78, 79, 80
crustaceans: 79, 80
insects: 7, 79
ostracodes: 79, 80
trilobites: 78, 80
Articulata: 56
Artiodactyla: 106
artiodactyls: 106
camels: 106
entelodonts: 101, 106
ash, volcanic: 5
_Astacodes_: 79
_Astartella_: 67
Asteroidea: 82
asteroids: 82, 83
Asterozoa: 82
_Astraeospongium_: 50
_Astrhelia_: 53
_Astylospongia_: 50
_Aulosteges tuberculatus_: 12, 13
Austin: 14, 17, 19, 87
Austin College: 27
Australia: 87
author, of a fossil: 22
autopores: 51
Aves: 89, 100
_Avonia_: 12, 13
_signata_: 12, 13
_subhorrida_: 12, 13

B
bacteria: 47
_Baculites_: 77
bags, collecting: 17, 18
Balcones fault zone: 36, 37
baluchitheres: 104, 106
_Baluchitherium_: 106
_Barbatia_: 74
Baylor County: 89
Baylor University: 1, 2, 27, 90, 91, 95
Beaumont: 1, 34
clay: 34
Beaver, Harold: 1
_Belemnites_: 77, 78
Belemnoidea: 78
belemnoids: 77, 78
_Bellerophon_: 61
Big Bend area: 35, 36
National Park: 35, 97, 102
Big Spring: 89
binomial nomenclature: 21-22
Bird, R. T.: 2, 15, 96
birds, fossil: 5, 100
Blastoidea: 81
blastoids: 26, 28, 81
Blinn College: 27
bone, permineralized: 9
Books About Fossils: 108-110
Boon, Jack: 1
Brachiopoda: 54, 55, 56
brachiopods: 26, 29, 54, 55, 56
articulate: 54, 55, 56, 57, 58
Cambrian: 55
Cretaceous: 56
inarticulate: 55, 56
Mississippian: 55
Pennsylvanian: 57, 58
Permian: 12, 13
Recent: 56
silicified: 12, 13
symmetry: 24, 26, 29
_Brachiosaurus_: 90
Brewster County: 11, 12, 35, 41
brittle stars: 82
Bronaugh, Richmond L.: 1
Brontosaurus: 90, 97, 98
_Brontotherium_: 104, 105, 106
Brown, L. F., Jr.: 1
Bryophyta: 44
Bryozoa: 51, 54, 55
bryozoans: 26, 27, 28, 30, 51, 54, 55, 84
Mississippian: 54
Pennsylvanian: 55
_bulla, Venericardia_: 72
Bureau of Economic Geology: 2, 19
burrows: 14
“button corals”: 49, 53