1. Name: Graffhamicrinus

    Location: Texas, USA, Graford Formation

    Age: 303-306 million years ago, Carboniferous Period

    This and other fossils of Graffhamicrinus are examples of where life, math, and seawater intersect. They are only found in particular places on ancient seafloors, and math can help predict their location.

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  2. Name: Cubitostrea lisbonensis

    Location: Texas, USA, Weches Formation

    Age: 40-48 million years ago, Paleogene Period (Eocene Epoch)

    The two halves of this shell of Cubitostrea might get mistaken for different species, but unlike other seashells with halves that are mirror images of each other, Cubitostrea and other oysters break the rules of symmetry.

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  3. Name: Batoidea

    Location: Florida, USA, Bone Valley Formation

    Age: 4.9-5.3 million years ago, Neogene Period (Pliocene Epoch)

    The fossil in the photograph was made by cells that usually construct teeth, but those cells grew on the back of a flat, wing-finned ray or skate. For millions of years rays and their relatives have repurposed tooth-forming cells to make hooks and spikes, called dermal thorns, in their skin.

    In a growing animal, only certain kinds of cells can make certain kinds of body tissue. For example, there are special cells that make bones, special cells that make teeth, and special cells that make the coloring in skin. The bodies of skates and rays repurpose some of their tooth-forming cells to form dermal thorns like these ones in the photograph.

    First, tooth-forming cells form the spiky part of the dermal thorn. Then, a subset of those cells lay down a hard, shiny material called enameloid, which is similar to the enamel on the outside of human teeth. Other cells lay down other tooth-forming minerals to make the base of the dermal thorn. Finally, bone-forming cells make attachment bone on the bottom of the structure.

    Dermal thorns help protect rays and skates. Multiple species can form identical dermal thorns. Without any other parts of the skeleton, it is impossible to identify exactly which species made the pair of dermal thorns in the photograph.

    Specimen Number: UF/TRO 17915

    Sources:

    Sire, Jean-Yves, and Ann Huysseune. “Formation of dermal skeletal and dental tissues in fish: a comparative and evolutionary approach.” Biological Reviews 78(2003):219-249.

    Reif, Wolf-Ernst. “Morphogenesis and histology of large scales of batoids (Elasmobranchii)” Paläeontologische Zeitschrift 53(1979)26-37.

    Kemp, Normal E. “Chapter 2: Integumentary System and Teeth.” In Sharks, Skates, and Rays: the Biology of Elasmobranch Fishes, edited by William C. Hamlett, 43-68. Baltimore: Johns Hopkins Press, 1999.

    Where are similar fossils found?

    Note: If you are looking for more information on dermal thorns, it might help to know that this fossilized dermal thorn and structures like it are also formally called odontodes, or dermal denticles.

    Bonus: Here is a picture of dermal thorns in a living ray.

     
  4. Name: Goniatites choctawensis

    Location: Oklahoma, USA, Caney Formation

    Age: 318-339 million years ago, Carboniferous Period

    Scientists use more than clocks to mark time. To measure time in rocks, they can use everything from certain atoms, like the kind used in carbon dating, to certain fossils like Goniatites.

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  5. Name: Ulocrinus

    Location: Texas, USA, Graford Formation

    Age:303-306 million years ago, Carboniferous Period

    When we die and our skeleton falls apart, it falls into 206 pieces. This skeleton in the photograph would end up in 600 pieces, if not hundreds more. When the skeleton is mostly intact, like this one, researchers can figure out details of the animal’s life.

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  6. Name: Hadrophyllum

    Location: Texas, USA, Smithwick Formation

    Age: 307-315 million years ago (Pennsylvanian Period)

    These individuals of Hadrophyllum have been dead for over 300 million years. A vast majority of their living coral relatives can’t move. In spite of that, researchers think that these animals could wiggle their way through the sand. Why?

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  7. 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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  8. 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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  9. 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?

     
  10. 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?