1. Name: Pectopteris arborescens

    Location: Texas, USA, Markley Formation

    Age: 295-303 million years ago, Carboniferous-Permian Periods

    Most plants grow from seeds today, but hundreds of millions of years ago seeds were rare or nonexistent. Without seeds, ancient fern-like and tree-like plants such as Pecopteris reproduced more like mushrooms and mold than like oak trees.

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  2. Name: Cybister

    Location: California, USA, Rancho La Brea Formation

    Age:10-55 thousand years ago, Quaternary Period (Pleistocene Epoch)

    There are too many fossils of water beetles in the tar pits of southern California. Compared to other animals in the tar pits, aquatic insects are overrepresented, and it may have to do with how those water beetles see.

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  3. Name: Archaeocidaris brownwoodensis

    Location: Texas, USA, Winchell Formation

    Age: 303-306 million years ago, Carboniferous Period

    Nine animals are crowded into this photograph. A single sea urchin, now crushed, was the home for a neighborhood of life.

    The other members of the community, besides the sea urchin, are bryozoans and brachiopods. Bryozoans are microscopic animals that live together in colonies and build lacy skeletons (marked in blue in the map on the upper right). Brachiopods are soft animals that live inside a pair of shells (marked in green).

    These fossils are the oldest evidence of community-building between sea urchins and other animals.

    When these bryozoans and brachiopods were young, they floated in the ocean. When it was time to change into an adult, they settled on the spines of a sea urchin. They stayed there for the rest of their lives, filtering food out of the water around them.

    Is there a benefit to these communities? The tiny hitchhikers probably didn’t benefit the sea urchin at all, but they didn’t hurt the sea urchin, either.

    In contrast, sea urchin spines were an ideal home for the smaller animals. The hitchhikers, unable to move on their own, could find new food sources on the back of a sea urchin. The spines provided protection that they could not provide for themselves. Finally, hard spines made a better home than the alternative - soft mud that could bury a small, immobile animal alive.

    Specimen Number:TMM 1967TX61

    Sources:

    Schneider, Chris L. “Hitchhiking on Pennsylvanian echinoids: Epibionts on Archaeocidaris.” Palaios 18(2003):435-444.

    Where are similar fossils found?

     
  4. Name: Neozanthopsis americanus

    Location: Texas, USA, Crockett Formation

    Age:37-41 million years ago, Paleogene Period (Eocene Epoch)

    This crab was right-handed. Most “handed” crabs today are also right-handed. Whether a crab is right-handed or left-handed has to do with generations of starvation.

    A crab is “right-handed” if its right claw is bigger than its left claw. Not all species of crabs are handed. Usually, the environment has to favor claw specialization to make handedness successful.

    In this case, the shape of the claws in the photograph gives a clue to the crab’s success. Not only is this crab’s right claw larger than its left, but it also has a set of bumps on the pincers. These bumps gave the crab an advantage over crabs of other species when it came to crushing snail shells to eat the animal inside.

    The snails that it ate were handed, too. In a snail’s case, handedness refers to the direction its shell coils in.

    A crab born with a left claw larger than its right claw will have a harder time cracking a snail with a right-handed shell. When there are more right-handed snails than left-handed snails, a left-handed crab is more likely to starve to death than a right-handed crab.

    When more right-handed crabs survive to produce the next generation, eventually a majority of crabs will be born from right-handed parents. Those right-handed crabs will eventually form a majority of the population.

    Specimen Number:BEG 21187

    Sources:

    Dietl, Gregory P., and Jonathan R. Hendricks. “Crab scars reveal survival advantage of left-handed snails.” Biology Letters 2(2006):439-442.

    Schweitzer, Carrie E. “Utility of proxy characters for classification of fossils: An example from the fossil Xanthoidea (Crustacea: Decapoda: Brachyura).” Journal of Paleontology 77(2003):1107-1128.

    Schweitzer, Carrie E. and Rodney M. Feldman. “The Decapoda (Crustacea) as predators on Mollusca through geologic time.” Palaios 25(2010):167-182.

    Stenzel, H. B. “Decapod crustaceans from the middle Eocene of Texas.” Journal of Paleontology 8(1934):38-56.

    Where are similar fossils found?

     
  5. Fossil Roulette will be taking a break until July while we go on expedition and collect more fossils.

    Many of the fossils we find will look like this mammal tooth in the photo. Most will be even smaller.

    See you when we return from the wilderness!

     
  6. Name: Cedaria minor 

    Location: Utah, USA, Weeks Formation

    Age: 444-461 million years ago, Cambrian Period


    No one has ever seen a living Cedaria, or any other trilobite. Even though they were one of the most diverse groups of animals ever known, the last living trilobite died 250 million years before any human walked on Earth. 

    Trilobites were ocean-dwelling animals with many legs and hard, outer plates. So far, researchers have recognized and named over 20,000 species of trilobite. That’s an amazing diversity. In comparison, all of the different kinds of birds alive today, from ostriches to sparrows to penguins, add up to only half as many species. There are more than three times as many species of trilobites as there are species of mammals. 

    Trilobites had more than large numbers. They also came in a diversity of forms and sizes. 

    Cedaria was small, and would fit on a dime. In contrast, some of the other trilobite species grew forty times larger, and reached 72 centimeters, about the size of a freight-truck tire. Others grew to be only a tenth of a centimeter, about the width of a grain of rice. 

    The abundance and diversity of trilobites helped them make it through two mass extinctions, times when many other groups went extinct. 

    However, by the time a third mass extinction hit 250 million years ago, trilobites had lost the diversity and abundance that had helped them thrive. At the end, only a handful of trilobite species were left to go extinct.

    Specimen Number: NPL 15006

    Sources:

    Gon, Sam III. “A Guide to the Orders of Trilobites,” accessed 9 October 2012. http://www.trilobites.info. 

    Hughes, Nigel C. “The evolution of trilobite body patterning.” Annual Review of Earth and Planetary Sciences 35(2007):401-434.

    IUCN. “Summary of number of animal species in each Red List Category in each taxonomic class.” In: IUCN  Red List of Threatened Species. Version 2012.1. Accessed 9 October 2012. http://www.iucnredlist.org/documents/summarystatistics/2012_1_RL_Stats_Table_3a.pdf

    Where are similar fossils found?

     
  7. Name: Dracontomelon macdonaldii

    Location: Los Santos State, Panama, Búcaro Formation

    Age:34-41 million years ago, Paleogene Period (Eocene Epoch)

    This fossil of Dracontomelon macdonaldii comes from Panama, from a time when Central America was an island. It is eleven thousand miles from where you would expect to find it, across the Pacific Ocean from the home of its living relatives.

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  8. Name: Gonioloboceras welleri

    Location: Texas, USA, Graham Formation

    Age:299-303 million years ago, Carboniferous Period

    Each red lightning bolt in the photograph started off as part of a home. The animal that made the home flooded, then walled off, then drained each of those lightning bolt sections, one by one. For an ammonoid like Gonioloboceras, filling its own shell with water was just a part of growing up and moving around.

    All ammonoid animals, like Gonioloboceras, had a soft body that rested in the outermost, open end of a hard shell.

    The rest of the shell of each animal had many inner walls that divided the structure into chambers. The borders between each lightning bolt in the photo are the remains of those inner walls.

    As the ammonoid animal grew larger, it made more shell to accommodate its body. It also made more chambers that it could fill or empty in order to offset its increasing body weight.

    When those chambers were full of water, the animal sank deeper into the ocean. When the animal replaced the water with air through a tube running along the outer border of the shell, the animal floated higher.

    In that way, an ammonoid could swim around the ocean without flippers or fins, like its closest living relative, the nautilus, does today.

    Specimen Number: BEG 5886

    Sources:

    Hewitt, R. A., A. Checa, G. E. G. Westermann, and P. M. Zaborski. “Chamber growth in ammonites inferred from color markings and naturally etched surfaces of Cretaceous vascoceratids from Nigeria.” Lethaia 24(1991):271-287.

    Mutvei, H., and R. A. Reyment. “Buoyancy control and siphuncle function in ammonoids.” Palaeontology 16(1973):623-636.

    Where are similar fossils found?

     
  9. Name: Coenholectypus planatus

    Location: Texas, USA, Comanche Peak Formation

    Age:99-113 million years ago, Cretaceous Period

    “Left” and “right” are meaningless concepts for a sea urchin like Coenholectypus. Those ideas work well with animals like us, who only have one line of symmetry. However, a sea urchin has five lines of symmetry. “Pentaradial” describes animals with that feature.

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  10. Name: Belosaepia ungula

    Location: Texas, USA, Crockett Formation

    Age:37-41 million years ago, Paleogene Period (Eocene Epoch)

    Fossils of Belosaepia (see photograph) have been identified as everything from teeth to tail spikes. What are they, really?

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