Paleoenvironmental and paleoecological information from fossils and sediment

 

This display appeared in the University of Michigan Museum of Natural History in 2020 and highlights the recent work of members of the Badgley Lab using fossil specimens and sediment samples to learn about ancient animals, plants, and their environments. Display photo courtesy of the University of Michigan Museum of Natural History.

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Many plants deposit silica into their cells as they grow, and these silica bodies, known as phytoliths, are preserved in sediment after the plant dies. Fossilized phytoliths, like the one shown at right, can be identified by taxon or functional type (i.e., grass, woody dicot, etc.). By studying phytolith assemblages preserved in sediment and ancient soils, researchers can determine their vegetation composition and habitat structure (open or closed canopy).

The isotopic composition of plants is also recorded--not only in their tissues as with animals--but also in the soil in which they grow. This means that the isotopic composition of ancient sediment and soils, when analyzed, can show what the vegetation was or the environmental conditions under which it grew. Sometimes, small carbonate nodules (concentrations of the mineral calcite) form in soils and around plant roots, especially in arid regions. These nodules preserve the chemical composition of the vegetation and can be analyzed isotopically.

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Using 2D and 3D images of fossil teeth, points called landmarks (the red dots) are identified and marked on the image. Comparing differences and similarities among landmarks from multiple specimens can show how shape varies among individuals, species, or families. The genus or species of an extinct animal can be identified by finding similarities with modern specimens, and its diet can be inferred based on tooth shape and wear patterns on the tooth surface.

Photo by Molly Moroz

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The chemical signatures, or isotopes, of food and water sources are incorporated into body tissues during animals' and plants' lives. Studying carbon isotopes in fossilized mouse teeth can tell us what type of plants the animal ate; oxygen isotopes point to specific water sources.

 

At left, mice teeth are shown ready for sampling, attached to a surface with putty. The graphed results of the sampling (right) show that the diets of five families of rodents from southern California changed between 17 and 13 million years ago, through an episode of climatic warming. The isotopes from teeth of these animals became less negative over time, indicating that their food sources changed, or that growing conditions of plants became drier.

Photos and data courtesy of Tara Smiley

Lots of information can come from very small things like this fossilized mouse jaw, from the extinct genus Copemys. This 3D print of the jaw is enlarged 50 times the original size!

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*the jaw

Finding answers in the sand

It turns out that even tiny things can tell huge stories about the past. This fragment of a fossilized mouse jaw contains information about the animal it belonged to, its diet, and its environment. It can even help us better understand animals and environments today. This mouse lived roughly 14 million years ago in southern California. Studying the tooth shape and isotopic composition of specimens like this can help us understand what these animals ate and the environments they lived in millions of years ago.