The Multi-Stranded Career of Leo J. Hickey

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The Multi-Stranded Career of Leo J. Hickey
Scott L. Wing,1Kirk R. Johnson,1Daniel J. Peppe,2Walton A.Green3and David Winship Taylor4
1 National Museum of Natural History, Smithsonian Institution, Washington, DC 20013 USA
2 Department of Geology, Baylor University, One Bear Place #97354, Waco, TX 76798 USA
3 Harvard University Botanical Museum, 26 Oxford Street, Cambridge, MA 02138 USA
4 Corresponding author: Department of Biology, Indiana University Southeast,
4201 Grant Line Road, New Albany, IN 47150 USA
—email: dwtaylo2@ius.edu
Bulletin of the Peabody Museum of Natural History 55(2):69–78, October 2014.
© 2014 Peabody Museum of Natural History, Yale University. All rights reserved. • http://peabody.yale.edu
Introduction
Leo J. Hickey was born in Philadelphia on 26
April 1940. He attended a minor seminary in
Indiana for high school, then earned a B.S. from
Villanova University in 1962. Leo went to Prince-
ton University to work on his Ph.D. in geology
under the supervision of Erling Dorf, receiving
his degree in 1967. After completing his doctor-
ate, Leo was a postdoctoral fellow at the Smith-
sonian Institution’s Museum of Natural History
until 1969 when he was hired as a curator in the
Department of Paleobiology. In 1982 he left the
Smithsonian for Yale University, becoming direc-
tor of the Peabody Museum of Natural History
and professor in the Department of Geology and
Geophysics and the Department of Biology. Leo
was director of the Peabody for five years, and
then returned to research, teaching and work on
the Peabody Museum’s collections and exhibits.
He served as chair of the Department of Geology
and Geophysics from 2003 to 2006. Leo remained
active in research, teaching and exhibits until
shortly before his death on 9 February 2013.
Leo Hickey was an imaginative and iconoclas-
tic scholar whose ideas had wide influence across
many areas of biology and geology. In botany, he
made fundamental contributions to understand-
ing the morphology, systematics, phylogeny and
evolution of flowering plants. In paleontology he
carried out groundbreaking studies in paleoecol-
ogy, paleoclimate, biostratigraphy and the study
of mass extinctions. Throughout his 45-year sci-
entific career Leo’s most important insights
reflected his twin interests in geology and botany,
as well as his remarkable depth of knowledge in
both fields. Below we outline some of Leo’s major
contributions, emphasizing a few case studies of
his best-known work, including leaf architecture,
angiosperm evolution and radiation, early Paleo-
gene plant communities and the extinction and
response of plants to the Cretaceous–Paleogene
boundary mass extinction event.
Leaf Architecture and
Angiosperm Systematics
Angiosperm leaf fossils are abundant in terrestrial
rocks of Cretaceous and Cenozoic age, and as a
result they were studied early in the development
of paleobotany. From the 1820s to the 1940s,
leaves were a major basis for interpreting terres-
trial paleoenvironments and biostratigraphy.
Unfortunately, most fossil leaves were identified
by superficial matching of their general form with
living genera, which led to inconsistent recogni-
tion of morphotaxa and rampant botanical mis-
identification. As a consequence of this flawed
approach, paleoclimate had been misinterpreted,
trends in angiosperm phylogeny had been mis-
represented and biostratigraphic patterns had
been obscured. By the 1960s, the field suffered
from a nearly complete loss of credibility.
When Leo entered paleobotany in the 1960s
he saw great potential in the fossil record of
angiosperm leaves—if they could be recognized
consistently and identified successfully. He was
writing up his Ph.D. thesis on the Paleocene–
Eocene flora of the Golden Valley Formation of
North Dakota when it became clear that many of
the names that had traditionally been applied to
the fossils were botanically incorrect. He later
described the horrible sinking feeling that came
from realizing he had been building castles on a

sand foundation. Not given to despair, he devoted
himself to what he called a “herbarium crawl” at
the New York Botanical Garden, and realized that
before the potential of leaf fossils could be tapped
he would need to regularize and improve on exist-
ing terms for describing leaf morphology, as well
as store the vein features of thousands of living
angiosperm species in his remarkable visual
memory. This survey resulted in his new system
of leaf architectural terminology and in the two
papers with the largest number of citations
recorded on his Google Scholar page (Hickey
1973, 1979).
While working for the Smithsonian Leo rec-
ognized that in order to study the leaf architec-
ture of the enormous diversity of angiosperms
properly, he had to create a collection of cleared
and stained leaves representing the group as
broadly as possible, and so he began the National
Collection of Cleared Leaves at the Smithsonian
Institution. Collaborating with Jack Wolfe of the
US Geological Survey, who was amassing a simi-
lar collection of cleared leaves, Leo compiled
information on leaf architecture for all dicotyle-
dons, which then included magnoliids, water lilies
and other basal angiosperms. By mapping vein
architectural characters onto the then-current
understanding of angiosperm phylogeny, Hickey
and Wolfe were able to show that many high-level
phylogenetic relationships in angiosperms were
supported by characteristic vein patterns. Vege-
tative morphology, specifically leaf venation and
particularly characters of the leaf margin and
teeth, did contain systematically informative fea-
tures—flowers were not the only route to under-
standing the relationships among flowering
plants. The resulting paper (Hickey and Wolfe
1975) is now Leo’s third-most-cited publication.
In addition to providing new characters support-
ing some traditional systematic relationships,
Hickey and Wolfe also suggested new relation-
ships that had not been inferred from analyses of
floral characters alone. They argued for a close
relationship between Juglandaceae and rosids
because of similarities in tooth venation and leaf
organization, a then-controversial idea later con-
firmed by molecular systematic studies (e.g.,
Stevens 2001). They also recognized two major
subgroups within asterids, though the orders
assigned to these subgroups do not correspond
exactly to those currently assigned to the two
major subclades of asterids. Through much of his
career Leo and his colleagues integrated observa-
tions of the leaves of living and fossil plants, and
used cladistic methods to arrive at phylogenetic
conclusions (e.g., Li and Hickey 1988; Hickey and
Taylor 1991; Fuller and Hickey 2005; Jud and
Hickey 2014).
Geology, Sedimentology
and Plant Fossils
Even as Leo was developing leaf architectural ter-
minology and investigating the systematic distri-
bution of leaf features, he was also working on
improving the interpretation of the sedimentary
environments in which fossil leaves were pre-
served. This work began in earnest during his
Ph.D. project on the Golden Valley Formation,
where he completed scores of meticulous strati-
graphic sections and a map of the formation that
is still the bible today for anyone working on these
rocks (Hickey 1977). As part of that study he doc-
umented the large variations in floral composi-
tion that can occur in different local sedimentary
environments of the same age, a point he returned
to strongly with his work on Paleocene floras of
the Clark’s Fork Basin in Wyoming (Hickey
1980). He realized that such local variation
recorded real habitat heterogeneity along an
ancient landscape, in addition to the influence of
deposition and preservation. Leo’s ability to read
sedimentary facies and reconstruct the environ-
mental mosaic of ancient landscapes was key to
understanding the habitats in which ancient
plants lived, but also to making robust biostrati-
graphic zonations that represented real change
through time rather than the vagaries of shifting
local habitats. During subsequent work in the
Paleogene of Montana (Hickey 1980) and the
Canadian Arctic (Hickey et al. 1983), Leo contin-
ued to break new ground by integrating angio-
sperm paleobotany with sedimentary facies
analysis, magnetostratigraphy and vertebrate
biostratigraphy. In so doing he provided some
of the first terrestrial climate curves that were
temporally well calibrated, and could thus be
compared with the rapidly developing marine
paleoclimate record.
The integration of paleobotany with sedimen-
tary geology had its most influential expression in
Leo’s studies with James A. Doyle on the Early
Bulletin of the Peabody Museum of Natural History 55(2) • October 2014
70

The Multi-Stranded Career of Leo J. Hickey • Wing et al. 71
Cretaceous fossil record of angiosperm diversifi-
cation in the Potomac Group (Doyle and Hickey
1976; Hickey and Doyle 1977). This work pro-
vided not only a description of early angiosperm
evolution, but also a view of its environmental
and ecological context. Collections were made in
carefully described sedimentological context,
showing that angiosperms were initially very rare
and first became abundant in environments with
clear signs of frequent disturbance—fluvial point-
bars or sites with abundant fossil charcoal or both.
Not until the late Early Cretaceous did angio-
sperms become highly abundant in most stable
Potomac Group environments. Leo also inter-
preted the morphology of early angiosperm leaves
in a functional context, showing that regardless
of their systematic affinities, they had features
similar to living early-successional plants. These
observations, integrated with Jim Doyle’s palyno-
logical work, led the two to develop the “riparian
weed” model of the early angiosperm radiation,
the idea that early angiosperms were relatively
small plants with rapid growth and reproduction
that preferentially occupied disturbed habitats
with abundant light. This idea has heavily influ-
enced all subsequent work in the field.
Hickey and Doyle’s papers on the Potomac
Group were influential among botanists from the
start, but they have become classic paleoecologi-
cal works in a broader sense because of their
masterful integration of data from so many
sources—sedimentology, stratigraphy, biostratig-
raphy, functional morphology, systematics and
evolution. The Potomac Group papers of 1976
and 1977 provided strong evidence to the scien-
tific world that the fossil record held extraordi-
nary insights about plant evolution, if it were only
studied seriously and in a modern way. Together
these papers have now been cited more than 650
times.
Case Study: Paleogene of the
Clark’s Fork Basin and the Arctic
Upon moving from Princeton to the Smithson-
ian in 1967, Leo began to work in the Clark’s Fork
Basin of northern Wyoming, using the geology
field camp in Red Lodge, Montana, as a base. Ver-
tebrate paleontologist Glenn Jepsen, a mentor of
Leo’s from Princeton, had been collecting Pale-
ocene mammals in this area since the late 1930s
and had developed a zonation of the Paleocene
strata using mammalian fossils. Phil Gingerich at
the University of Michigan had added much
greater detail and statistical rigor to the mam-
malian biostratigraphy, and Leo realized that the
maturing mammal zonation gave him the poten-
tial to subdivide the 10 million years of the Pale-
ocene into four evolutionary stages.
Interacting with geologists at the Red Lodge
camp, Leo saw that the Paleocene sedimentary
rocks in the Clark’s Fork Basin offered more than
just a refined time scale. The rocks had been
deposited as the adjacent Beartooth Mountains
were being uplifted, and Leo recognized that these
synorogenic sediments recorded a diversity of
landscapes and facies with distinct fossil floras
(Hickey 1980; Yuretich and Hickey 1984; Hickey
and Yuretich 1997). The rocks and fossil leaves
preserved much greater landscape heterogeneity
than he had encountered in the Potomac Group
or the Golden Valley Formation. The fossils of the
Clark’s Fork Basin offered the chance to study
both change through time (with age control from
the vertebrate fossils) and varied depositional set-
tings that recorded vegetation at the landscape
scale. Between 1967 and 1979, Leo discovered and
quarried more than 60 fossil plant sites and
published an overview that discussed the bios-
tratigraphic, paleoecological and paleoclimatic
implications of Paleocene floras from the Clark’s
Fork Basin (Hickey 1980).
By this time, Mary Dawson at the Carnegie
Museum had discovered the first Paleocene–
Eocene vertebrate fossils in the Canadian Arctic,
and she invited Leo to join her project to docu-
ment the plants that she had seen. Leo made his
first trip to Ellesmere Island in 1979 and quickly
caught the Arctic bug. The Eureka Sound Forma-
tion is tremendously thick and contains fossil
plants at many levels. Leo realized that work in
the Arctic would add latitudinal range to his
developing understanding of Paleocene floras and
landscapes, and also that Paleocene polar forests
were a unique and extinct biome. As the work in
the Arctic developed it began to appear that
species occurred earlier in the polar region than
they did at middle latitudes in the Rocky Moun-
tains, suggesting the possibility that the Arctic
might have been a center of origin for some line-
ages that appeared only later in middle latitudes.
Leo collaborated with magnetostratigraphers

from the University of Wisconsin–Milwaukee to
test this hypothesis, and they published their
interpretation in Science (Hickey et al. 1983). The
article caused considerable controversy, and ulti-
mately the magnetostratigraphy was revealed to
be faulty. Leo spent three more field seasons rec-
tifying the results and correcting the errors. Even
though the idea of the Arctic as a center of origin
in the Paleogene turned out to be incorrect, Leo’s
collections, stratigraphic sections and field obser-
vations are a unique resource, and modern scien-
tific interest in warm Arctic ecosystems was
spurred by his work.
Leo worked in the High Arctic for six field
seasons, documenting Paleocene–Eocene floras
and exploring more than a dozen different field
areas on Ellesmere, Axel Heiberg and Devon
Island. On Devon Island, the team discovered fos-
sil vertebrates and plants in the sediments that
filled the Miocene Haughton asteroid impact
crater and recovered a nearly complete rhinoc-
eros skeleton (Omar et al. 1987; Hickey et al.
1988). Recognizing that a large river flowing
through the crater had no name, Leo worked with
the Canadian Geographic Names board and for-
mally named Canada’s first and only Rhinoceros
River.
Case Study: Plant Extinction
at the Cretaceous–Paleogene Boundary
In 1980, Leo’s graduate school friend Walter
Alvarez led a team that proposed the revolution-
ary idea that the Cretaceous–Paleogene (K-Pg)
mass extinction was the result of a bolide impact.
Alvarez’s paleontologist colleagues at Berkeley
rejected the idea as too simple and in opposition
to the vertebrate fossil record that had been devel-
oped in eastern Montana. Both Leo and Walter
had studied geology at Princeton with paleob-
otanist Erling Dorf, who had evaluated plant
extinction at the K-Pg boundary in Wyoming in
the 1940s. Familiar with this work, Leo surveyed
the paleobotanical literature, concluding that
land plants experienced gradual rather than cat-
astrophic extinction at the end of the Creta-
ceous (Clemens et al. 1981; Hickey 1981). Leo’s
careful analysis of the floral record across the K-
Pg boundary also showed that terminal Creta-
ceous floras were poorly known and that Dorf’s
earlier work lacked the stratigraphic resolution
necessary to resolve an essentially instantaneous
event.
In 1983, Leo invited prospective student Kirk
Johnson to join him on a field trip to Jordan,
Montana, where Alvarez and his supporters had
recently discovered evidence of the K-Pg bolide
smack in the middle of the Berkeley paleontology
field area. Alvarez and his paleontologist oppo-
nents agreed to bring the debate to the outcrop.
During this trip, it became clear that it might
be possible to combine the microstratigraphy of
the K-Pg boundary pollen record with studies of
plant macrofossils to test the Alvarez hypothesis.
Leo encouraged Kirk to tackle this problem and
allowed him the use of his field equipment and
field vehicle. Over the next five years, Kirk applied
Leo’s methodology to the K-Pg boundary prob-
lem, paying strict attention to stratigraphic con-
trol, depositional setting and sample sizes.
Eventually these data showed that plants did
undergo a local extinction at the K-Pg boundary,
documenting the extinction better than any other
group of terrestrial organisms (Johnson and
Hickey 1991). When the data came in Leo changed
his initial opinion on the suddenness of the K-Pg
extinction, a move that was unusual among pale-
ontologists, and therefore highly influential.
Teaching and Exhibits
Leo’s scientific accomplishments are notable for
their breadth and for the way they are rooted in a
deep understanding of quite distinct areas of
knowledge: geology and botany. However, his joy
in thinking, analyzing and knowing was accom-
panied by a desire to share his ideas with others,
and this he did from the start to the finish of his
career. Leo found inspiration in fieldwork and in
reading the history of the earth from rocks and
landscapes. At Yale he was famed for his stratig-
raphy class, which more than one student
described as the most difficult but most interest-
ing class taken in four years of college. He also
shared his enthusiasm through longer research
trips with graduate and undergraduate students,
mostly to the northern Rocky Mountains. There
are many stories of Leo in the field, where he cut
a distinctive figure. Even during the roughest field
conditions, amid perils from rattlesnakes to polar
bears, he maintained certain formalities: a morn-
ing shave, a clean khaki shirt, a brimmed field hat,
Bulletin of the Peabody Museum of Natural History 55(2) • October 2014
72

cold chocolate cookies at lunch and a glass of
bourbon in the evening. These field excursions
were conducted with a wonderful combination of
personal warmth and scientific rigor. Field trips
were also nonstop learning opportunities in
topics far from geology and botany. Leo had com-
mand of a truly remarkable diversity of knowl-
edge ranging from early Christian history,
through Celtic culture and frontier lore, to formal
logic and classical languages. Following the Inter-
national Organization of Palaeobotany Conven-
tion in Bonn, Germany, in 2008, he took a short
side trip with two former students to the cathe-
dral in Cologne. There he gave an impromptu
tour replete with detailed information on iconog-
raphy, architecture, Roman history and Latin, to
the point where he began to attract a small follow-
ing of tourists, convinced he was an official guide.
During his career Leo contributed to science
education not only through graduate and under-
graduate teaching, but also by developing
museum exhibits that reached a younger and
broader audience. At the Smithsonian he was
chair of the Exhibits Committee from 1973 until
almost the time of his departure, and developed a
plan for renovating the paleontology halls in a
phased fashion that allowed different but inter-
locking sets of curators to apply their expertise in
separate areas of a coordinated overall exhibit. He
himself worked hardest on exhibits about the Ice
Age, the Conquest of Land, the Origin of Flower-
ing Plants, and Fossils and Industry. These
exhibits entranced and educated literally tens of
millions of visitors for more than 30 years until
they closed in the spring of 2014.
Leo’s favorite part of the Smithsonian fossil
halls was a walk-through diorama representing
the Early Cretaceous environment of the Wash-
ington, DC, area, where so many important early
angiosperm fossils had been found in the
Potomac Group, and where he and Jim Doyle had
done seminal work on early flowering plant evo-
lution, ecology and environment. The display
consisted of a bridge across a reconstruction of
the ancient landscape, with the wet, conifer-dom-
inated backswamp habitat on one side and a
scraggly, leggy thicket of Sapindopsis plants clam-
bering over the point bar on the other. On record-
ings archived at the Smithsonian one can hear Leo
instructing the artists in exhaustive (and no doubt
exhausting) detail about how things needed to
look. The “water” at the edge of the diorama’s
swamp had to be the color of strong tea to reflect
the dissolved tannins, somewhat translucent to a
depth of a few inches, but opaque where deeper.
The “north” side of a log had to be painted darker
than the dry, sun-bleached “south” side. The
attention to detail must have been maddening to
the artists, but it delighted generations of muse-
umgoers and fanned the imaginations of more
than one future paleobotanist. Another unique
perspective was the minor and distant role for
dinosaurs in Leo’s Cretaceous landscape—the
plants were the stars of the show.
During his decades at Yale, Leo continued to
be extremely active in public education as well as
teaching, helping develop seven exhibits at the
Peabody Museum, including enhancements to
the “Age of Reptiles” mural in the Great Hall.
Leo’s love for the murals and museums was on
display when he announced the publication of the
then-oldest evidence of flowers, the Koonwarra
plant (Taylor and Hickey 1990). He took care to
make sure the correct age was represented in the
background mural of the Peabody’s Great Hall,
and his careful staging of the press conference
ensured coverage of the event by national and
international print, television and radio press. A
relatively recent addition to the museum is an
outdoor bronze statue of the ceratopsian dinosaur
Torosaurus, which looms over passersby on the
Whitney Avenue side. Anyone who pays atten-
tion to the landscaping surrounding Torosaurus
will see Leo’s hand in the choice of plants for the
Cretaceous Garden, an exhibit he delighted in
working on during his last few years, and that will
continue to represent his paleobotanical perspec-
tive on the past as it grows along the side of the
Peabody in years to come.
Closing
This volume demonstrates how Leo’s students and
postdocs have continued to push the boundaries
of areas that Leo himself pioneered. In a symme-
try he would have enjoyed, it includes contribu-
tions with coauthors from his first (Scott Wing)
and last (Dan Peppe) students, and first (Jim
Doyle) and last (David Winship Taylor) postdocs,
as well as other students, students of students and
postdocs of postdocs. Little et al. (2014) refine one
of Leo’s leaf architectural methods called leaf rank-
The Multi-Stranded Career of Leo J. Hickey • Wing et al. 73

ing. Taylor and Gee (2014) apply leaf architectural
characters to the evolution of water lilies. The con-
tribution by Doyle and Upchurch (2014) revisits
early angiosperm diversification in the Potomac
Group, while Jud (2014) applies leaf architectural
methods to a previously undescribed Potomac
Group collection that includes early angiosperms.
Hu and Taylor (2014) examine the paleoecology
of an Albian flora from Jordan. Peppe and Hickey
(2014) detail plant biostratigraphy and paleoecol-
ogy in the early Paleocene of the Great Plains, and
Green (2014) examines the functional morphol-
ogy of arborescent lycopsids.
In 2008, while working on a project with his
last student, Dan Peppe, Leo reflected on his career
and his contributions to paleobotany. Leo felt that
his research contributed in two major ways. First,
by developing and applying leaf architectural
analysis to angiosperm fossil leaves, he showed
how to identify and in many cases classify fossil
species represented by dispersed leaves alone.
These rigorous descriptive methods were a signif-
icant improvement over early paleobotanical
reliance on superficial similarities between fossils
and modern plant taxa. Second, by making large,
quantitative collections of fossil leaves in the con-
text of sedimentary environments and strati-
graphic sections, he had shown it was possible to
reconstruct ecosystems and how they changed
through time. Further, because these environmen-
tally and geochronologically well-constrained flo-
ral collections were carefully described, identified
and taxonomically classified (when possible) on
the basis of leaf architectural analyses of floras, it
has become possible to assess patterns of plant
evolution, plant phylogeny and the response of
plants to climate change and major extinction
events more rigorously. The impact of these types
of integrative studies is evident in the work being
done by many paleobotanists today, and by the
many citations to Leo’s work (documented on his
Google Scholar page [http://scholar.google.com/
citations?user=_nGJ5YQAAAAJ&hl=en, accessed
16 June 2014]).
In 2009 Leo was awarded the Moore Medal
by the Society for Sedimentary Geology for his
major insights into plant ecology and evolution,
achieved by integrating geological and biological
approaches to the plant fossil record. The award
recognized his exceptional capacity to bring
together sedimentology and stratigraphy and
couple them with his deep understanding of
angiosperm morphology and evolution. There are
few who ever master such disparate fields. Leo’s
diverse base of knowledge and his acutely logical
mind are reasons his work has been so innovative
and influential. By the end of his life Leo had
played a major role in reinvigorating paleobotany,
the discredited discipline he found as a youth, and
his insights had already been expanded and
extended by two generations of botanists and
paleobotanists, including many of his own stu-
dents and postdocs, and their students.
In his last few years Leo returned to his roots
in plant systematics and descriptive paleobotany,
working on a series of Cretaceous floras with cur-
rent and former students (e.g., Peppe et al. 2008;
Miller and Hickey 2008, 2010). He loved the
process of chasing down the oldest valid name for
the taxon he was working on. Surrounded by fos-
sils, herbarium sheets, and 19th-century taxo-
nomic monographs, he said he felt as though he
was writing a symphony. Leo’s work continued
literally until the last weeks of his life. In an e-mail
to a former student sent from his hospital room
prior to brain surgery in December 2012, Leo
wrote: “Here are the two specimens that I asked
about this morning: Sequoia longifolia Les-
quereux, 1878, Plate 61, figures 28 and 29... They
have come to take me away now so there is no
time for further comment.” A few weeks later, in
early January 2013, Leo said he was regretful that
it did not appear he would be able to complete the
project he was working on—a Late Cretaceous
flora from the Meeteetse Formation—which is
still being worked on by his coauthors. It seemed
that his inability to bring more of the former
world to human attention was almost of greater
concern to him than his own departure.
Acknowledgments
We thank Peter Wilf for setting up a Google
Scholar page for Leo Hickey, Jim Doyle for cor-
recting the faulty memory of one of us (S.L.
Wing) in a memorial printed in 2013 by the Pale-
obotanical Section of the Botanical Society of
America, Diana Marsh for searching out photo-
graphs, video and audio files at the Smithsonian
Institution Archives, and Natasha Atkins and
Derek Briggs for comments on and corrections to
the manuscript.
Bulletin of the Peabody Museum of Natural History 55(2) • October 2014
74

Received 7 July 2014; revised and accepted 7 July
2014.
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Canada. Meteoritics 23:221–231.
HICKEY, L.J., R.M. WEST, M.R. DAWSON AND D.K. CHOI. 1983.
Arctic terrestrial biota: paleomagnetic evidence of age dis-
parity with mid-northern latitudes during the Late Creta-
ceous and Early Tertiary. Science 221:1153–1156.
HICKEY, L.J. AND J.A. WOLFE. 1975. The bases of angiosperm
phylogeny: vegetative morphology. Annals of the Missouri
Botanical Garden 62:538–589.
HICKEY, L.J. AND R. YURETICH. 1997. The Belfry Member of the
Fort Union Formation, an allocyclic lacustrine deposit of
late middle Paleocene Age in the Bighorn Basin, Montana
and Wyoming. In: E.B. Campen, ed. Bighorn Basin: 50
Years on the Frontier. Bighorn Basin Symposium Golden
Anniversary, Cody, Wyoming. [n.p.]: Yellowstone Bighorn
Research Association. pp. 38–42.
HOCHULI, P.A., U. HEIMHOFER AND H. WEISSERT. 2006. Tim-
ing of early angiosperm radiation: recalibrating the classi-
cal succession. Journal of the Geological Society 163:
587–594.
HU, S. AND D.W. TAYLOR. 2014. Floristics and paleoecology of
an Early Cretaceous flora from Jordan. Bulletin of the
Peabody Museum of Natural History 55(2):153–170.
JOHNSON, K.R. AND L.J. HICKEY. 1991. Megafloral change
across the Cretaceous-Tertiary boundary, northern Great
Plains, U.S.A. In: V.L. Sharpton and P.D. Ward, eds. Global
Catastrophes in Earth History: An Interdisciplinary Con-
ference on Impact, Vulcanism, and Mass Mortality.Boul-
der, CO: Geological Society of America. (Special Paper 247).
pp. 433–444.
JUD, N.A. 2014. Morphotype catalog of a Zone I (Aptian-Ear-
liest Albian) flora from Fairlington, Virginia, USA. Bulletin
of the Peabody Museum of Natural History 55(2):135–152.
JUD, N.A. AND L.J. HICKEY. 2013. Potomacapnos apeleutheron
gen. et sp. nov., a new Early Cretaceous angiosperm from
the Potomac Group and its implications for the evolution of
eudicot leaf architecture. American Journal of Botany
100:2437–2449.
LI, H., AND L.J. HICKEY. 1988. Leaf architecture and systemat-
ics of the Hamamelidaceae sensu lato. Acta Phytotaxonom-
ica Sinica 26:96–110.
LITTLE, S.A., W.A. GREEN, S.L. WING AND P. WILF. 2014. Rein-
vestigation of leaf rank, an underappreciated component of
Leo Hickey’s legacy. Bulletin of the Peabody Museum of
Natural History 55(2):79–87.
MILLER, I.M. AND L.J. HICKEY. 2008. The fossil flora of the
Winthrop Formation (Albian–Early Cretaceous) of Wash-
ington State, USA. Part I: Bryophyta and Pteridophytina.
Bulletin of the Peabody Museum of Natural History
49(2):135–180.
—2010. The fossil flora of the Winthrop Formation (Albian–
Early Cretaceous) of Washington State, USA. Part II: Pino-
phytina. Bulletin of the Peabody Museum of Natural His-
tory 51(1):3–96.
OMAR, G., K.R. JOHNSON, L.J. HICKEY, P.B. ROBERTSON, M.R.
DAWSON AND C.W. BARNOSKY. 1987. Fission-track dating
of Haughton Astrobleme and included biota, Devon Island,
Canada. Science 237:1603–1605.
PEPPE, D.J. AND L.J. HICKEY. 2014. Fort Union Formation fos-
sil leaves (Paleocene, Williston Basin, North Dakota, USA)
indicate evolutionary relationships between Paleocene and
Eocene plant species. Bulletin of the Peabody Museum of
Natural History 55(2):171–189.
PEPPE, D.J., L.J. HICKEY, I.M. MILLER AND W.A. GREEN. 2008.
A morphotype catalogue, floristic analysis and stratigraphic
description of the Aspen Shale Flora (Cretaceous–Albian) of
Southwestern Wyoming. Bulletin of the Peabody Museum
of Natural History 49(2):181–208.
STEVENS, P.F. 2001–. Angiosperm Phylogeny Website [inter-
net]. Version 12. St. Louis, MO: Missouri Botanical Garden.
[updated July 2012 and later]. Available from: http://www.
mobot.org/MOBOT/research/APweb/
TAYLOR, D.W. AND C.T. GEE. 2014. Phylogenetic analysis of
fossil water lilies based on leaf architecture and vegetative
The Multi-Stranded Career of Leo J. Hickey • Wing et al. 75

characters: testing phylogenetic hypotheses from molecu-
lar studies. Bulletin of the Peabody Museum of Natural His-
tory 55(2):89–110.
TAYLOR, D.W. AND L.J. HICKEY. 1990. An Aptian plant with
attached leaves and flowers: implications for angiosperm
origin. Science 247:702–704.
YURETICH R.F., L.J. HICKEY, B.P. GREGSON AND Y.L. HSIA.
1984. Lacustrine deposits in the Paleocene Fort Union For-
mation, northern Bighorn Basin, Montana. Journal of Sed-
imentary Petrology 54(3):836–852.
Bibliography of Leo J. Hickey
HICKEY, L.J. AND G.A. COOPER. 1971. Nomination of R. W.
Chaney for the Paleontological Society Medal. Journal of
Paleontology 45:567–569.
HICKEY, L.J. 1972. Stratigraphic summary of the Golden Val-
ley Formation (Paleocene-Eocene) of western North
Dakota. Guidebook, Coal Geology Division, Geological
Society of America (11/10–11/72). North Dakota Geologi-
cal Survey Miscellaneous Series 50:105–122.
READ, R.W. AND L.J. HICKEY. 1972. A revised classification of
fossil palm and palm-like leaves. Taxon 21:129–137.
SCOTT, R.A., P.L. WILLIAMS, L.C. CRAIG, E.S. BARGHOORN, L.J.
HICKEY AND H.D. MACGINITIE. 1972. “Pre-Cretaceous”
angiosperms from Utah: evidence for Tertiary age of the
palm wood and roots. American Journal of Botany
59:886–896.
HICKEY, L.J. 1973. Classification of the architecture of
dicotyledonous leaves. American Journal of Botany
60:17–33.
—1974. Section D, foliar venation. In: A.E. Radford, W.C.
Dickison, J.R. Massey and C.R. Bell, eds. Vascular Plant Sys-
tematics.New York: Harper and Row. pp. 192–198.
—1974. Clasificación de la arquitectura de las hojas de
dicotiledóneas. Boletín de la Sociedad Argentina de
Botánica 16:1–26.
HICKEY, L.J. AND R.W. HODGES. 1975. Lepidopteran leaf mine
from the early Eocene Wind River Formation of northwest-
ern Wyoming. Science 189:718–720.
HICKEY, L.J. AND J.A. WOLFE. 1975. The bases of angiosperm
phylogeny: vegetative morphology. Annals of the Missouri
Botanical Garden 62:538–589.
DOYLE, J.A. AND L.J. HICKEY. 1976. Pollen and leaves from the
mid-Cretaceous Potomac Group and their bearing on early
angiosperm evolution. In: C.B. Beck, ed. Origin and Early
Evolution of Angiosperms. New York: Columbia Univer-
sity Press. pp. 139–206. [Excerpts reprinted in: T.N. Taylor
and E.L. Smoot, eds. 1984. Benchmark Papers in Paleob-
otany: Part II, Triassic through Pliocene. New York: Van
Nostrand, Rheinhold. pp. 207–237.]
ROMERO, E.J. AND L.J. HICKEY. 1976. A fossil leaf of Akaniaceae
from Paleocene beds in Argentina. Bulletin of the Torrey
Botanical Club 103:126–131.
HICKEY, L.J. AND J.A. DOYLE. 1977. Early Cretaceous evidence
for angiosperm evolution. Botanical Review 42:3–105.
HICKEY, L.J. 1978. Paleobotany Year 1977. Geotimes 23(1):37.
—1978. Origin of the major features of angiospermous leaf
architecture in the fossil record. CFS, Courier Forschungsin-
stitut Senckenberg 30:27–34.
HICKEY, L.J. AND R.K. PETERSON. 1978. Zingiberopsis, a fossil
genus of the ginger family from Late Cretaceous to early
Eocene sediments of Western Interior North America.
Canadian Journal of Botany 56:1136–1152.
HICKEY, L.J. 1979. Paleobotany Year 1978. Geotimes
24(1):41–42.
—1979. A revised classification of the architecture of dicotyle-
donous leaves. In: C.R. Metcalfe and L. Chalk, eds. Anatomy
of the Dicotyledons, Volume 1. 2nd ed. Oxford: Oxford
University Press. pp. 25–39.
—1980. Paleobotany Year 1979. Geotimes 25(2):39–40.
—1980. Paleocene stratigraphy and flora of the Clark’s Fork
Basin. In: P.D. Gingerich, ed. Early Cenozoic Paleontology
and Stratigraphy of the Bighorn Basin, Wyoming. Ann
Arbor, MI: University of Michigan (Papers in Paleontology
24). pp. 33–50.
—1980. Paleontologists and continental drift. Science 210:1200.
—1981. Paleobotany Year 1980. Geotimes 26(2):45–46.
—1981. Presentation of Schuchert Award of the Paleontolog-
ical Society to James A. Doyle. Journal of Paleontology
55:701–702.
—1981. Book review of Biostratigraphy of Fossil Plants, by
D.L. Dilcher and T.N. Taylor, eds. Science 212:1021–
1022.
—1981. Land plant evidence compatible with gradual, not cat-
astrophic change at the end of the Cretaceous. Nature
293:529–531.
CLEMENS, W.A., ARCHIBALD, J.D. AND HICKEY, L.J. 1981. Out
with a whimper not a bang. Paleobiology 7:293–298.
WEST, R.M., M.R. DAWSON, L.J. HICKEY AND A.D. MIALL.
1981. Upper Cretaceous and Paleogene sedimentary rocks,
Eastern Canadian Arctic and related North Atlantic area.
In: J.W. Kerr and A.J. Fergusson, eds. Geology of the North
Atlantic Borderlands. Calgary: Canadian Society of Petro-
leum Geologists. (Memoir 7). pp. 279–298.
HICKEY, L.J. 1982. Paleobotany Year 1981. Geotimes 27(2):
49–50.
HICKEY, L.J., R.M. WEST, M.R. DAWSON AND D.K. CHOI. 1983.
Arctic terrestrial biota: paleomagnetic evidence of age dis-
parity with mid-northern latitudes during the Late Creta-
ceous and Early Tertiary. Science 221:1153–1156.
TIFFNEY, B.H. AND L.J. HICKEY. 1983. Paleobotany: review of
events of 1982. Geotimes 28(2):32–33.
HICKEY, L.J. 1984. Road logs and stops, part 1. In: N.O. Fred-
eriksen and K. Krafft, eds. Cretaceous and Tertiary Stratig-
raphy, Paleontology, and Structure, Southwestern Maryland
and Northeastern Virginia: Field Trip Volume and Guide-
book. Reston, VA: American Association of Stratigraphic
Palynologists Foundation. pp. 193–209.
—1984. Summary and implications of the fossil plant record
of the Potomac Group. In: N.O. Frederiksen and K. Krafft,
eds. Cretaceous and Tertiary Stratigraphy, Paleontology,
and Structure, Southwestern Maryland and Northeastern
Virginia: Field Trip Volume and Guidebook. Reston, VA:
American Association of Stratigraphic Palynologists Foun-
dation. pp. 213–248.
—1984. Eternal summer at 80 degrees north. Discovery
17:17–23.
—1984. Changes in the angiosperm flora across the Creta-
ceous-Tertiary boundary. In: W.A. Berggren and J.A. Van-
Couvering, eds. Catastrophes and Earth History: The New
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Uniformitarianism. Princeton, NJ: Princeton University
Press. pp. 279–313.
HICKEY, L.J., R.M. WEST AND M.R. DAWSON. 1984. Arctic bios-
tratigraphic heterochroneity. Science 224:175–176.
DAWSON, M.R., R.M. WEST AND L.J. HICKEY. 1984. Paleonto-
logical evidence relating to the distribution and paleoenvi-
ronments of the Eureka Sound and Beaufort Formations,
northeastern Banks Island, Arctic Canada. Current
Research, Part B, Geological Survey of Canada Paper 84-
1B:359–361.
TIFFNEY, B.H. AND L.J. HICKEY. 1984. Paleobotany follows
interdisciplinary bent. Geotimes 29:18–20.
WING, S.L. AND L.J. HICKEY. 1984. The Platycarya perplex and
the evolution of the Juglandaceae. American Journal of
Botany 71:388–411.
YURETICH, R.F., L.J. HICKEY, B.P. GREGSON AND Y.L. HSIA.
1984. Lacustrine deposits in the Paleocene Fort Union For-
mation, northern Bighorn Basin, Montana. Journal of Sed-
imentary Petrology 54(3):836–852.
HICKEY, L.J. 1985. A once-fertile wasteland. The Sciences
25(1):42–46.
—1986. Summary and implications of the fossil plant record
of the Potomac Group. In: T.W. Broadhead, ed. Land Plants:
Notes for a Short Course.Knoxville, TN: University of Ten-
nessee, Department of Geological Sciences (Studies in Geol-
ogy 15). pp. 162–181.
HICKEY, L.J., K.R. JOHNSON AND R.F. YURETICH. 1986. Road
log—Red Lodge, Montana to Clark, Wyoming via Elk
Basin and Powell, Wyoming: field trip through the facies
of the Fort Union formation. In: P.B. Garrison, ed. Geol-
ogy of the Beartooth Uplift and Adjacent Basins.Montana
Geological Society and Yellowstone-Bighorn Research
Association Joint Field Conference and Symposium.
Billings, MT: Montana Geological Society. pp. 279–290.
DAWSON, M.R., L.J. HICKEY AND K.R. JOHNSON. 1986. Discov-
ery of a Dermopteran skull from the Paleogene of Arctic
Canada. National Geographic Research 2(1):112–115.
OMAR, G., K.R. JOHNSON, L.J. HICKEY, P.B. ROBERTSON, M.R.
DAWSON AND C.W. BARNOSKY. 1987. Fission-track dating
of Haughton Astrobleme and included biota, Devon Island,
Canada. Science 237:1603–1605.
HICKEY, L.J., K.R. JOHNSON AND M.R. DAWSON. 1988. The
stratigraphy, sedimentology and fossils of the Haughton
Formation: a post-impact crater fill, Devon Island, N.W.T.,
Canada. Meteoritics 23:221–231.
LI, H. AND L.J. HICKEY. 1988. Leaf architecture and systemat-
ics of the Hamamelidaceae sensu lato. Acta Phytotaxonom-
ica Sinica 26:96–110.
TAYLOR, D.W. AND L.J. HICKEY. 1990. An Aptian plant with
attached leaves and flowers: implications for angiosperm
origin. Science 247:702–704.
HICKEY, L.J. 1991. The physical and biotic setting of trans-
Beringian cultures. In: K.R. Johnson, L.J. Hickey and C.A.
Hoover, eds. Crossroads of Continents: The Material Cul-
ture of Siberia and Alaska.Washington, DC and New
Haven, CT: Yale-Smithsonian Seminar on Material Culture.
pp. 8–10.
HICKEY, L.J. AND D.W. TAYLOR. 1991. The leaf architecture of
Ticodendron and the application of foliar characters in dis-
cerning its relationships. Annals of the Missouri Botanical
Garden 78:105–130.
JOHNSON, K.R. AND L.J. HICKEY. 1991. Megafloral change
across the Cretaceous-Tertiary boundary, northern Great
Plains, U.S.A. In: V.L. Sharpton and P.D. Ward, eds. Global
Catastrophes in Earth History: An Interdisciplinary Con-
ference on Impact, Vulcanism, and Mass Mortality.Boul-
der, CO: Geological Society of America. (Special Paper 247).
pp. 433–444.
HICKEY, L.J. AND L.J. MCWEENEY. 1992. Plants at the K/T
boundary [Scientific Correspondence]. Nature 356:295–
296. doi:10.1038/356295b0
TAYLOR, D.W. AND L.J. HICKEY. 1992. Phylogenetic evidence
for the herbaceous origin of angiosperms. Plant Systematics
and Evolution 180:137–156.
WING, S.L., L.J. HICKEY AND C.C. SWISHER. 1993. Implications
of an exceptional fossil flora for Late Cretaceous vegetation.
Nature 363:342–344.
HICKEY, L.J. AND L. KLISE. 1994. Peabody Museum’s fossil
plants: a tale of three collections. Discovery 25(1):23–26.
MOLDOWAN, J.M., B.J. HUIZINGA, J. DAHL, F.J. FAGO, D.W.
TAYLOR AND L.J. HICKEY. 1994. The molecular fossil record
of oleanane and its relationship to angiosperms. Science
265:768–771.
WING, S.L., J. ALROY AND L.J. HICKEY. 1995. Plant and mam-
mal diversity in the Paleocene to Early Eocene of the Bighorn
Basin. Palaeogeography, Paleaoclimatology, Palaeoecology
115:117–155.
HICKEY, L.J. 1996. Paleobotany. Geotimes 41(2):29–30.
HICKEY, L.J. AND D.W. TAYLOR. 1996. Origin of the
angiosperm flower. In: D.W. Taylor and L.J. Hickey, eds.
Flowering Plant Origin, Evolution, and Phylogeny. London:
Chapman and Hall. pp. 176–231.
TAYLOR, D.W. AND L.J. HICKEY. 1996. Evidence for, and implica-
tions of an herbaceous origin for angiosperms. In: D.W. Tay-
lor and L.J. Hickey, eds. Flowering Plant Origin, Evolution,
and Phylogeny. London: Chapman and Hall. pp. 232–266.
HICKEY, L.J. 1997. Paleobotany. Geotimes 42(2):31–32.
HICKEY, L.J. AND R. YURETICH. 1997. The Belfry Member of
the Fort Union Formation, an allocyclic lacustrine
deposit of late middle Paleocene Age in the Bighorn
Basin, Montana and Wyoming. In: E.B. Campen, ed.
Bighorn Basin: 50 Years on the Frontier. Bighorn Basin
Symposium Golden Anniversary, Cody, Wyoming.
[n.p.]: Yellowstone Bighorn Research Association. pp.
38–42.
HICKEY, L.J. 1999. Common Fossil Plants of Western North
America by William D. Tidwell [book review]. The Quar-
terly Review of Biology 74(2):215.
ROYER, D.L, S.L. WING, D.J. BEERLING, D.W. JOLLEY, P.L.
KOCH, L.J. HICKEY AND R.A. BERNER. 2001. Paleobotanical
evidence for near present-day levels of atmospheric CO dur-
ing part of the Tertiary. Science 292:2310–2313.
WAAGE, K.M., C. MACCLINTOCK AND L.J. HICKEY. 2001. Post-
glacial fossils from Long Island Sound off West Haven, Con-
necticut. Postilla 225:1–26.
HICKEY, L.J. 2001. On the nomenclatural status of the morpho-
genera, Quereuxia and Trapago. Taxon 50:1119–1124.
BEERLING, D.J., J.A. LAKE, R.A. BERNER, L.J. HICKEY, D.W.
TAYLOR AND D.L. ROYER. 2002. Carbon isotope evidence
implying high O2/CO2ratios in the Permo-Carboniferous
atmosphere. Geochimica et Cosmochimica Acta 66:
3757–3767.
The Multi-Stranded Career of Leo J. Hickey • Wing et al. 77

ROYER, D., L.J. HICKEY AND S.L. WING. 2003. Ecological con-
servatism in the “living fossil” Ginkgo. Paleobiology 29(1):
84–104.
WILDMAN, R.A. JR., L.J. HICKEY, M.B. DICKINSON, R.A. BERNER,
J.M. ROBINSON, M. DIETRICH, R.H. ESSENHIGH AND C.B.
WILDMAN. 2004. Burning of forest materials under late Pale-
ozoic high atmospheric oxygen levels. Geology 32(5):457–460.
HICKEY, L.J. AND C. MACCLINTOCK. 2005. Reading the rock
and landscape records of the New Haven region. In:
N.W. McHone and M.J. Peterson, eds. Guidebook for
Field Trips in Connecticut. New England Intercollegiate
Geological Conference, 97th Annual Meeting; 2005 Sep
30–Oct 1–2. Hartford, CT: State Geological and Natural
History Survey of Connecticut, Department of Environ-
mental Protection (Guidebook 8). pp. 161–175.
FULLER, D.Q. AND L.J. HICKEY. 2005. Systematics and leaf archi-
tecture of the Gunneraceae. Botanical Review 71(3):
295–353.
GREEN, W.A. AND L.J. HICKEY. 2005. Leaf architectural pro-
files of angiosperm floras across the Cretaceous/Tertiary
Boundary. American Journal of Science 305:983–
1013.
MILLER, I.M., M.T. BRANDON AND L.J. HICKEY. 2006. Using leaf
margin analysis to estimate the mid-Cretaceous (Albian)
paleolatitude of the Baja BC block. Earth and Planetary Sci-
ence Letters 245:95–114.
MANCHESTER, S.R. AND L.J. HICKEY. 2007. Reproductive and
vegetative organs of Browniea Gen. N. (Nyssaceae) from the
Paleocene of North America. International Journal of Plant
Sciences 168(2):229–249.
PEPPE, D.J., J.M. ERICKSON AND L.J. HICKEY. 2007. Fossil leaf
species from the Fox Hills Formation (Upper Cretaceous:
North Dakota, USA) and their paleogeographic signifi-
cance. Journal of Paleontology 81:550–567.
KLISE, L.S. AND L.J. HICKEY. 2007. Preserving extant Metase-
quoia shoots for herbaria. Bulletin of the Peabody Museum
of Natural History 48(2):255–259.
YANG, H. AND L.J. HICKEY, EDS. 2007. Metasequoia: back from
the brink: an update. Proceedings of the Second Interna-
tional Symposium on Metasequoia and Associated Plants.
Bulletin of the Peabody Museum of Natural History
48(2):183–246.
MILLER, I.M. AND L.J. HICKEY. 2008. The fossil flora of the
Winthrop Formation (Albian–Early Cretaceous) of Wash-
ington State, USA. Part I: Bryophyta and Pteridophytina.
Bulletin of the Peabody Museum of Natural History
49(2):135–180.
PEPPE, D.J., L.J. HICKEY, I.M. MILLER AND W.A. GREEN. 2008.
A morphotype catalogue, floristic analysis and stratigraphic
description of the Aspen Shale flora (Cretaceous–Albian)
of southwestern Wyoming. Bulletin of the Peabody
Museum of Natural History 49(2):181–208.
ELLIS, B., D.C. DALY, L.J. HICKEY, K.R. JOHNSON, J.D.
MITCHELL, P. WILF AND S.L. WING. 2009. Manual of Leaf
Architecture. Ithaca, NY: Cornell University Press.
MILLER, I.M. AND L.J. HICKEY. 2010. The fossil flora of the
Winthrop Formation (Albian–Early Cretaceous) of Wash-
ington State, USA. Part II: Pinophytina. Bulletin of the
Peabody Museum of Natural History 51(1):3–96.
ROYER, D.L., I.M. MILLER, D.J. PEPPE AND L.J. HICKEY. 2010.
Leaf economic traits support a weedy habitat for early
angiosperms. American Journal of Botany 97(3):438–445.
HICKEY, L.J., S. HU AND B.J. SKINNER. 2011. A new genus of
silicified conifer wood from the Late Triassic of Connecticut.
American Journal of Science 311(7):608–631.
WING, S.L., C.A.E. STRÖMBERG, L.J. HICKEY, F. TIVER, B.
WILLIS, R.J. BURNHAM AND A.K. BEHRENSMEYER. 2012. Flo-
ral and environmental gradients on a Late Cretaceous land-
scape. Ecological Monographs 82(1):23–47.
JUD, N.A. AND L.J. HICKEY. 2013. Potomacapnos apeleutheron
gen. et sp. nov., a new Early Cretaceous angiosperm from
the Potomac Group and its implications for the evolution of
eudicot leaf architecture. American Journal of Botany
100:2437–2449.
Bulletin of the Peabody Museum of Natural History 55(2) • October 2014
78