Texas Fossils: An Amateur Collector's Handbook

by William Henry Matthews

I. Fossils displaying radial [symmetry]—symmetrical repetition of parts around a central axis A. [Fossil] tapering, cylindrical, cone-shaped: 1. Fossil with [longitudinal] radial partitions or septa; cone-shaped[Coral] 2. Shell with [transverse] septa or sutures; tapering at one end[Cephalopod] 3. Shell without internal septa or partitions: a. Shell large, heavy; usually with external longitudinal ribs. Occur only in [Cretaceous] rocks[Rudistid] b. Shell small (usually less than 2 inches long), tusk-shaped, open at both ends. Rare in [Paleozoic] and [Mesozoic] rocks[Scaphopod] B. Fossil disk-shaped or flattened dome-shaped: 1. Fossil with radiating star pattern on top[Echinoid] 2. Fossil [subconical] to hemispherical, dome-shaped; base concave or flat; minute pits or pores covering surface; typically small (less than 3 inches across)Bryozoa 3. Fossil small (less than ½ inch); generally disk-shapedForaminifera (orbitoidid) 4. Fossil disk-shaped or button-like; with longitudinal, radial partitions or septaCoral C. Fossil composed of segments or plates: 1. Fossil composed of circular segments, disks, or chambers; when united form cylinder: a. Tapered shellCephalopod b. Non-tapered, segments small and of relatively uniform thickness with hole in center; individual columnals disk-shapedCrinoid stem 2. Fossil composed of many-sided plates: a. Bud-shaped fossil of 13 wedge-shaped plates[Blastoid] b. Cup-shaped fossil of many curved plates surrounded by branching armsCrinoid II. Fossils displaying [bilateral] symmetry—symmetrical duplication of parts on each side of a plane A. Fossil coiled in a single plane: 1. Shell divided by internal transverse partitions or suturesCephalopod 2. Shell without internal partitions or sutures[Gastropod] 3. Shell small; spindle-shaped; resembles wheat grain. Common in [Pennsylvanian] and [Permian] rocksForaminifera (fusulinids) B. Fossil not coiled: 1. Shells or valves similar to clams: a. Plane of symmetry parallel to hinge; [equivalved][Pelecypod] b. Plane of symmetry (almost bilaterally symmetrical) at right angles to hinge line; mostly [inequivalved]; strongly ribbed. “Scallop-like” with “ears.” Rare in Paleozoic rocksPelecypod c. Plane of symmetry at right angles to hinge line; inequivalved; not “scallop-like” and without “ears.” Larger [valve] commonly has an opening in beak. Common in Paleozoic rocks[Brachiopod] 2. Fossil tapering, cylindrical, cone-shaped: a. Fossil with internal longitudinal, radial septa or partitions; cone-shapedCoral b. Shell with internal transverse partitions or sutures; tapering at one endCephalopod c. Shell without internal septa or partitions. (1) Shell large, heavy; usually with external longitudinal ribs. Occur only in Cretaceous rocksRudistid (2) Shell small (usually less than 2 inches), tusk-shaped, open at both ends. Rare in Paleozoic and Mesozoic rocksScaphopod 3. Fossil heart-shaped, domed or flattened; radial star pattern on topEchinoid 4. Fossil segmented: a. Fossil divided into 3 lobes; may be curled up. Not found in Mesozoic or [Cenozoic] rocks[Trilobite] b. Fossil flattened or elongate; resembles shrimp, crab, or crayfishCrustacean III. Fossils displaying no apparent symmetry A. Shell without transverse internal partitions or sutures: 1. Shell coiled like ram’s horn, low spired, opening of shell very large; surface has [concentric] ridges. Shell has two valves; smaller, flattened valve not often found. In Texas found only in Cretaceous rocksPelecypod (Note: Some Paleozoic gastropods, “2,” closely resemble larger valve of these pelecypods) 2. Shell tightly coiled; most have higher spire than “1.” Opening of shell smaller than “1”; shell not as rough as “1” and has only one valveGastropod B. Coiled fossils; coiling not in one plane: 1. Shell with transverse internal partitions or sutures: a. Partitions always smooth; thick shelled; loosely and irregularly coiled, usually in large compact masses of many individual shells. Occur only in Cretaceous rocks[Caprinid] b. Partitions (sutures) usually wrinkled; relatively thin shelled; mostly regularly and tightly coiled; occur as separate individual specimensCephalopod 2. Shell without transverse internal partitions or suturesGastropod 3. Solid spiral ridge around central axis; resembles a corkscrewBryozoa C. Uncoiled fossils: 1. Fossil resembles a narrow saw blade; typically found as thin film of carbon. Not found in Mesozoic or Cenozoic rocks[Graptolite] 2. Fossil irregularly cone-shaped; longitudinal radial partitions or septaCoral 3. Shell resembles a clam or oyster shell but valve or shell not symmetricalPelecypod (mostly oysters) 4. Branching twig-like fossils: a. Fossils covered with minute pores or openingsBryozoa b. Fossils with evenly distributed, relatively large openings with longitudinal radial partitions or septa[Colonial] coral 5. Lace-like fossils; occur as thin sheets or filmsBryozoa 6. Fossils composed of radiating masses of [polygonal] or circular tubes containing radial septaColonial coral 7. Irregular fossils; typically cylindrical with rough surface: a. Fossil has large axial opening and thick wall; usually has external longitudinal ribs. Occurs only in Cretaceous rocksRudistid b. Fossil solid with no large axial opening; surface with small pits or pores (fewer than in Bryozoa). In Texas, occurs most commonly in Pennsylvanian and Permian rocksSponge

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A.&M. College of Texas, College Station Amarillo College, Amarillo Arlington State College, Arlington Austin College, Sherman Baylor University, Waco Blinn College, Brenham Corpus Christi, University of, Corpus Christi Del Mar College, Corpus Christi East Texas State College, Commerce Hardin-Simmons University, Abilene Henderson County Junior College, Athens Houston, University of, Houston Howard County Junior College, Big Spring Kilgore College, Kilgore Lamar State College of Technology, Beaumont Lee College, Baytown McMurry College, Abilene Midwestern University, Wichita Falls North Texas State College, Denton Odessa College, Odessa Pan American College, Edinburg Rice University, Houston St. Mary’s University, San Antonio San Angelo College, San Angelo San Antonio College, San Antonio Southern Methodist University, Dallas South Texas College, Houston Southwestern University, Georgetown Stephen F. Austin State College, Nacogdoches Sul Ross State College, Alpine Tarleton State College, Stephenville Texarkana College, Texarkana Texas Christian University, Fort Worth Texas College, Tyler Texas College of Arts and Industries, Kingsville Texas Technological College, Lubbock Texas Western College, El Paso The University of Texas, Austin Trinity University, San Antonio Tyler Junior College, Tyler West Texas State College, Canyon

Plate 6
[Fossil] Identification Chart
I [RADIAL SYMMETRY]

A. Tapering, cylindrical cone-shaped fossils 1. Cone-shaped with [longitudinal] partitions or septa[Coral] 2. Fossils with septa or sutures; tapering at one end[Cephalopod] 3. Shell without internal partitions or sutures a. Shell large heavy, external longitudinal ribs. [Cretaceous] only[Rudistid] b. Shell small, tusk-shaped open at both ends. Rare in [Paleozoic] and [Mesozoic][Scaphopod] B. Disc or dome-shaped fossils 1. Star pattern on top[Echinoid] 2. [Subconical] small pits or pores on topBryozoan 3. Small disc-shaped (less than ½ inch)Orbitoid Foraminifera 4. Disc-shaped or button-like, with longitudinal partitions or septaCoral C. Fossils composed of segments or plates 1. Circular discs or chambers; when united form cylinder a. Tapered shellCephalopod b. Not tapered, segments small of uniform thickness, hole in centerCrinoid Stem 2. [Fossil] composed of many-sided plates a. Bud-shaped, 13 wedge-shaped plates[Blastoid] b. Cup-shaped, many curved plates branching armsCrinoid

Plate 7
[Fossil] Identification Chart
II [BILATERAL] [SYMMETRY]

A. [Fossil] coiled in a single plane 1. Shell divided by internal [transverse] partitions or sutures[Cephalopod] 2. Shell without internal partitions or sutures[Gastropod] 3. Shell small, spindle-shaped; resembles wheat grain. [Pennsylvanian] and [Permian]Foraminifera [fusulinid] B. Fossil not coiled 1. Shells or valves similar to clams a. Plane of [symmetry] parallel to hinge; [equivalved][Pelecypod] b. Plane of symmetry almost at right angles to hinge; strongly ribbed; “Scallop-like” with “ears”, [inequivalved]Pelecypod c. Plane of symmetry at right angles to [hinge-line]; without “ears”, not “Scallop-like”; commonly with opening in beak, inequivalved[Brachiopod] 2. Fossil tapering, cylindrical or cone-shaped a. Cone-shaped, internal [longitudinal] partitions or septa[Coral] b. Tapered, internal transverse partitionsCephalopod c. Shell without internal septa or partitions (1.) Shell large heavy, longitudinal ribs. [Cretaceous] only[Rudistid] (2.) Shell small, tusk-shaped, open at both ends, rare in [Paleozoic] and [Mesozoic] rocks[Scaphopod] 3. Fossil heart-shaped, domed or flattened; star pattern on top[Echinoid] 4. Fossil segmented a. Divided into 3 lobes, may be curled up. Paleozoic only[Trilobite] b. Flattened or elongate, resembles shrimpCrustacean

Plate 8
[Fossil] Identification Chart
III NO APPARENT [SYMMETRY]