T.L. 'Tommy' Phillips
Emeritus Professor of Plant Biology
Affiliate, Department of Geology
Member, National Academy of Sciences
65 Morrill Hall MC-116
Paleobotanical Research - Building 337
(reprinted from "Slices of Time - Prehistoric Past is Recorded in Coal" by Holly Korab, in LAS News, 2000, on the occasion of Dr. Phillips’ election to the National Academy of Sciences.)
“Coal is versatile. You can burn it or tuck it in the Christmas stockings of mischievous children. If you luck upon a petrified chunk called a coal ball, you can even reconstruct prehistoric life on Earth.
‘Inside these coal balls are beautifully anatomically-preserved plants,’ says Tom Phillips, a paleobotanist in LAS. ‘This is not what used to be the plant—it is the plant—which gives us a huge window into our geologic past.’
For the past 39 years, Phillips has been opening this window into the past. Recently he was elected into the National Academy of Sciences in recognition for his extraordinary work in documenting Pennsylvanian Age plant life to the extent that scientists are now reconstructing environments that existed 300 million years ago. His extensive botanical record and database provide clues as to the origins of commercially valuable coals and offer scientific insights such as how plants evolved. Scientists today are also interested in the signposts the data may yield for global change. Phillips discovered that many plants disappeared abruptly in the middle to late Pennsylvanian for reasons thought to be tied to a change in the paleoclimate.
‘Nature has performed multi-million-year experiments many times in the past,’ says Phillips. ‘These fossils tell the results of those experiments.’
Coals balls are petrified plants that formed 320 and 300 million years ago in a period also called the Great Coal Age. This was before dinosaurs and flowering plants.
The plants coal balls immortalize were tropical flora that extended 9,000 miles from North America to China, back when North America, Europe, and Asia were still joined as a single continent called Laurasia. The portion that now constitutes the coal belt was farther south than that region is today, with large portions straddling the equator. Low spots, such as Illinois, were covered by muddy deltas that gave way to vast tropical swamps. Organic matter from the swampy forests accumulated as peat and, eventually, became coal.
Occasionally a trickle of water laden with the mineral calcium carbonate seeped into the debris and crystallized within the plants, cell by cell, before the plants were squashed by subsequent debris. These mineral-hardened plants were effectively frozen in time. Phillips says that many are so lifelike ‘that you'd think that if you water them they'd grow.’ It's possible, for instance, to reconstruct entire plants and their root systems because the plants are preserved essentially where they grew. They preserve details not available from other kinds of fossils.
When the trickle of mineral water was more like a flood, it fossilized the plants entombed in an entire seam of coal—top to bottom. These massive coal balls are particularly prized because they record the gradual changes in the number and distribution of plants in the swamp over thousands of years. They are, in effect, slices of ecological time.
In the early 1970s, while other paleobotanists were reconstructing individual plants, Phillips was thinking bigger. He proposed the then-radical idea of reconstructing entire paleoenvironments. ‘I didn't want to know just that these plants existed,’ says Phillips. ‘I wanted to know what grew where and why.’
Phillips began amassing what is now the largest collection of coal balls in the world—some 40,000 specimens. The collection represents 80 different coal seams that together document plant life spanning some 12 million years. Phillips and his graduate students sometimes chased halfway around the world after coal balls from coal seams that filled missing time slots—chiseling them from a mine or outcrop with sledge hammers and crowbars.
He systematically catalogued and quantified each coal ball by cutting them into slices and peeling off layers of plant material less than a cell thick. The plant tissue found in each square centimeter of the peel was then entered into a database, which was combined with data from the Illinois State Geological Survey on the abundance and location of ancient pollen and spores. (Scientists use data on pollen and spores, which were plentiful and resistant to deterioration, to project plant distribution in coals in which coal balls didn't form.)
These added steps of quantifying the biological constituents of the plants and their distribution are what set Phillips' work apart. For instance, that's how he learned that the lycopod tree, once the most abundant plant in the coal swamps, disappeared almost overnight—a climate-related shift missed by other studies.
If it is possible to love a chunk of coal, Phillips does. He examines each as a jeweler might an uncut diamond. Still, enough is enough. Phillips recently stopped collecting coal balls after concluding even he has plenty. But that doesn't mean his scientific exploration is over. ‘It's been a grand chase,’ says Phillips. ‘Now it's time to discover what else these fossils have to tell us.’ “
Willard, D.A., T. L. Phillips, A. D. Lesnikowska & W.A. DiMichele (2007) Paleoecology of the Late Pennsylvanian-age Calhoun coal bed and implications for long-term dynamics of wetland ecosystems. International J. Coal Geol. 69:21-54
Phillips, T.L. (2006) Biography of Aureal T. Cross: World class coal geologist, palynologist, paleobotanist and educator.. 69:1-20.
Phillips, T.L. & J. Galtier (2005) Evolutionary and ecological perspectives of Late Paleozoic ferns Part I. Zygopteridale. Review of Palaeobotany and Palynology 135:165-203
DiMichele, W.A., T. L. Phillips & W.J. Nelson (2002) Place vs. time and vegetational persistence: a comparison of four tropical mires from the Illinois Basin during the height of the Pennsylvanian Ice Age. International J. Coal Geol. 50:43-72
DiMichele, W.A. & T.L. Phillips (2002) The ecology of Paleozoic ferns. Rev. Palaeobot. Palynol. 119:143–159.
Labandeira, C.C. & T.L. Phillips (2002) Stem borings and petiole galls from Pennsylvanian tree ferns of Illinois, USA: Implications for the origin of the borer and galling functional-feeding-groups and holometabolous insects. Palaeontographica 264:1-84