Associated Smithsonian Expert: Kathy Hollis, M.S.

Kathy Hollis with Triceratops obtusus, collected in 1890 by John Bell Hatcher

Courtesy of Adrienne Block

Kathy Hollis is the collections manager in the Smithsonian National Museum of Natural History Department of Paleobiology. As a kid she would give rocks as gifts, assuming everyone thought rocks were as cool as she did. She majored in geology at the College of Wooster in Ohio and went on to finish a master’s in geology at the Ohio State University in 2005. It was at Ohio State that Kathy realized her love for museum collections. She finished a master’s in Museum Studies at the University of Colorado at Boulder in 2008 specializing in collections care and museum-based research. Kathy has been at the Smithsonian since 2010 and helps to care for one of the largest fossil collections in the world. Her work involves getting the information about what organisms lived when and where out of the collection drawers and making it digital, accessible, and searchable online. Kathy brakes for fossil echinoderms.

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This image was obtained from the Smithsonian Institution. The image or its contents may be protected by international copyright laws.

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Fossil crinoid (Graphiocrinus simplex) from the Mississipian period
Photo by Smithsonian Institution, Department of Paleobiology

About Crinoids (Class Crinoidea): Paleobiology

Like other echinoderms, crinoids have internal skeletons made of hard “ossicles.” The stalk that anchors a crinoid to a reef or other hard surface is strengthened by stacked, disk-shaped ossicles. The delicate rays of a crinoid are supported by smaller, linked ossicles that provide sites of attachment for the muscles that move them. What remains in the fossil record are these calcified, skeletal parts. Large berms of fossilized skeletons of crinoids are testimony to their abundance during the Paleozoic and Mesozoic eras. Scientists believe that the huge volume of calcified skeletal material left behind by crinoids shaped the environment for other species. Which crinoid fossils are present indicates the age of a fossil bed, since many species lived on Earth for short periods (in geologic time). Despite their prehistoric abundance, only one subclass of crinoids is still living today.

Fossil echinoderm (Geocome sp) from the Jurassic period
Photo by Smithsonian Institution, Department of Paleobiology

About Echinoderms (Phylum Echinodermata): Paleobiology

Echinoderms appear in the fossil record more than 500 million years ago, during the early Cambrian. What are usually left behind are hard mouthparts or parts of their skeletons, made of calcite plates. Rarely, an entire skeleton fossilizes, for example in a situation where it was quickly buried in sand. Even a piece of skeleton can provide information, because echinoderms have specific patterns in their skeletons. The echinoderms you see today have five-point (pentaradial) symmetry, often noticeable in five arms. While some of the earliest echinoderms were pentaradial, others had unusual body shapes. The “helioplacoids” had long, oval-shaped bodies with no arms, and a spiral pattern on the surface from tube feet wrapped around a central core. Helioplacoids went extinct even before the end of the Cambrian, as did a variety of other echinoderms, including the star-shaped Somasteroidea. Some echinoderms survived and diversified, becoming dominant in the oceans of the Paleozoic era.