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Home Dr. Hembree Research Continental Ichnology Laboratory Students Publications Courses News and Opportunities Links
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My research interests primarily lie with the interaction
of sedimentological and biological processes. I am interested in animal-substrate
interactions in ancient and modern continental (or “non-marine”)
environments. These interactions are preserved in the fossil record as trace
fossils. Trace fossils provide an in
situ record of ancient biodiversity, ecology, and environment. The study
of trace fossils, therefore, provides vital information for accurate
paleoenvironmental reconstructions. As sensitive indicators of environmental
and climatic change, ichnofossils are also useful for detailed sequence
stratigraphic analysis. In my research, I interpret the paleoenvironmental,
paleoclimatic, and paleoecological significance of paleosols and ichnofossils
preserved in the geologic record. This involves not only the study of
paleosols and continental trace fossils throughout geologic time, but also
the experimental study of burrowing behaviors of extant terrestrial annelids,
arthropods, amphibians, and reptiles. My current research projects involve
the study of the influence of climate changes on ancient soils and soil
ecosystems including those of the Pennsylvanian of southeast I am interested in recruiting motivated Master’s students
interested in these research areas.
For more information see News and Opportunities. |
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Continental Ichnology |
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My research in continental ichnology has covered a range of geologic
time and depositional settings. My research on Paleozoic vertebrates of
Kansas has involved the study of the aestivation burrows of the lysorophid amphibian, Brachydectes elongates, from pond deposits within
the Lower Permian Speiser Shale (Hembree et al.,
2004, 2005). These burrows represent the earliest evidence of aestivation
behavior by tetrapods in the fossil record.
Aestivation allows aquatic and semi-aquatic animals to survive long
periods of time without water and has become common among extant amphibians
and reptiles. Along with the detailed study of the surrounding paleosols,
associated ichnofossils and body fossils, these aestivation burrows provide
evidence for the interpretation of seasonality in the Permian of the North
American midcontinent. |
Top view of in situ
lysorophid burrow casts in an ephemeral pond
deposit of the Permian Speiser Shale, eastern |
Lysorphid burrow casts (Torridorefugium eskridgensis)
containing skeletal material excavated from the Permian Speiser
Shale, eastern Kansas. |
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My dissertation research covered a more recent period of paleoenvironmental
change, the late Eocene and early Oligocene.
I completed a detailed study of the ichnofossils associated with
paleosols in the White River Formation of northeastern Colorado (Hembree and
Hasiotis, 2007). These deposits contain the fossils of a number of burrowing
vertebrate groups, including the Amphisbaenia, an
order limbless lizard common in modern tropical to arid environments. The
paleosols of the White River Formation contain a diverse assemblage of
continental ichnofossils including those produced by dung beetles (Pallichnus and Macanopsis),
bees (Celliforma),
ants (Parowanichnus),
earthworms (Edaphichnium),
wasps, beetles, plants, and vertebrates. I used the lateral and vertical
changes in the distribution of ichnofossils to interpret paleoenvironmental
change in the sedimentary basin. Along with ichnofossils I have also applied paleopedologic and sedimentologic
principles to determine which environmental changes within the basin were due
to autogenic and allogenic processes. |
Large rhizoliths (fossil roots) preserved in an Oligocene
paleosol from northeast
Small, elliptical fecal pellets within an Oligocene
paleosol. These are interpreted as earthworm fecal pellets. |
A system of interconnected burrows and chambers
interpreted as a dung beetle nest. Preserved within an Oligocene paleosol.
Cross sectional view of a dung beetle brood burrow in an
Oligocene paleosol. |
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I am currently studying Pennsylvanian continental ichnofossils from
the paleosols of southeast Ohio (Hembree et al., 2011; Hembree and Nadon, in review).
The Pennsylvanian world contained all of the animals that comprise modern
soil ecosystems. The most abundant of
these soil organisms were the arthropods.
Pennsylvanian fossils of arthropod detritovores include millipedes, arthropleurids, mites, and insects all of which would
have engaged in feeding and dwelling behaviors in the soil based on
comparisons with modern examples. Fossils of arthropod herbivores include
flying insects. These organisms would have had temporary interaction with the
soil through the production of such reproductive structures as nests or brood
burrows. Fossils of arthropod predators include scorpions and arachnids.
Modern arthropod predators construct burrows for use as dwellings, temporary
resting places, and reproduction. Pennsylvanian amphibians and early
reptiles, such as microsaurs, temnospondyls,
and cotylosaurs, likely constructed burrows for use
as dwellings, temporary nests, and possibly aestivation. |
Ichnofossils interpreted as millipede burrows from the
Pennsylvanian Casselman Formation, southeast |
Rhizoliths from paleosols of the Pennsylvanian Casselman
Formation. |
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My research in continental ichnology also involves experimental work with modern organisms (Hembree and Hasiotis, 2006, 2007; Hembree 2009). Through detailed field observation and laboratory experiments with modern burrowing animals, continental tracemakers and their trace morphologies may be correlated to: 1) such substrate conditions as soil texture, moisture, and organic content; 2) depositional environments; and 3) such climatic factors as temperature and precipitation. I have established an animal burrowing laboratory that includes such burrowing animals as scorpions, whip scorpions, trapdoor spiders, centipedes, and millipedes. The goal of this research is to develop a database that provides qualitative and quantitative paleoenvironmental data for variations in continental trace fossil type and morphology. For more information on this research click here. |
Giant African millipedes (Lophostreptus rutilans)
used in burrowing experiments. |
Casts of spiral burrows produced by African millipedes
burrowing in loose, organic-rich sediment. |
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Paleopedology |
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The study of paleosols is important to geologists and biologists
alike. Paleosols provide unique evidence for interpreting ancient terrestrial
ecosystems, environment, and climate. They also provide some of the best
evidence of the evolution of terrestrial ecosystems as well as the
interaction of terrestrial organisms and the substrate. I have used paleopedology extensively along
with my studies of continental ichnology. My research has included the study
of paleosols from the Pennsylvanian and Permian of Kansas, Oklahoma, and
Ohio, the Triassic of Colorado, the Eocene of Wyoming, the Oligocene of
Colorado, South Dakota, Nebraska, and Wyoming, and the Miocene of Colorado.
In addition, by studying the characteristics of modern soils in Kansas
through field work and laboratory analysis, the pedogenic features preserved
in these paleosols have been used to interpret specific paleoenvironmental
and paleoclimatic conditions. My current research on Pennsylvanian paleosols of Ohio incorporates a
heavy field component in addition to laboratory analyses, including the
determination of bulk geochemistry, clay mineralogy, and stable isotope ratios.
There is an extensive record of Pennsylvanian paleosols in southeastern Ohio.
Exposures of the Allegheny and Conemaugh groups in particular allow for both
lateral and vertical analyses of the strata. One 30 m section, for example,
contains 10 different paleosols interpreted as four different types based on
parent material, pedogenic modification, and ichnofossils. |
Miocene paleosols in northeast |
Pennsylvanian paleosols in southeast |
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Reptile Paleobiology |
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The members of the Reptilia possess many
significant evolutionary adaptations for life in a variety of continental
environments. These adaptations are extremely useful in paleoenvironmental
and paleoclimatic studies. Such adaptations include extensive morphological
modification, from body elongation to complete loss of limbs, for fossorial
lifestyles. Many of my current projects involve the fossil record, ichnology,
phylogeny, paleoecology, and biogeography of amphisbaenians.
North American fossil amphisbaenians are present in
Paleocene to Miocene deposits of Colorado, Nebraska, South Dakota, and
Wyoming. I have completed a paleobiogeographic
study of the Amphisbaenia using worldwide
occurrences of both fossil and modern taxa (Hembree, 2006). This study has
indicated that the origin of this group, whose fossils appear only in the
Paleocene, may extend as far back as the Triassic. I have also completed a phylogenetic study and reclassification of the North
American family of amphisbaenians, the Rhineuridae (Hembree, 2007). This study has involved the
reexamination of fossils collected since the end of the nineteenth century
and resulted in the clarification of many taxonomic irregularities. Finally,
my study of the Amphisbaenia has involved the study
of living amphisbaenians including variations in
their burrowing behavior to changes in temperature, moisture, and substrate
conditions (Hembree and Hasiotis, 2006). The ecology of the modern amphisbaenians, therefore, provides an excellent analog
for interpreting the paleoecology of the fossil forms. The study of these
living animals, then, can help in interpreting changes in the
paleoenvironments and paleoclimate of |
Amphisbaena camura, a living amphisbaenian.
Skull of Rhineura floridana, a North American amphisbaenian.
Revised phylogeny of North American amphisbaenians. |
Cast of an amphisbaenians
burrow system excavated in a 10 gallon aquarium.
Branching tunnels in an amphisbaenians
burrow complex produced in the lab.
Push marks preserved on the surface of the tunnels in the
amphisbaenians burrow complex. These surficial structures provide clues to
determine both the excavation method and tracemaker. |
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Paleozoic Tetrapod Evolution and Paleoecology |
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The early evolution of tetrapods has been another major area of
interest in my research. Fossils generally classified as amphibians, or non-amniote tetrapods, continue to comprise a diverse, paraphyletic assemblage of lineages that seem to resist
further resolution. Recent phylogenetic work,
however, has begun to clarify some of these relationships. The fossils of
these organisms preserve the initial modifications necessary for life on
land. Their evolution can be used to interpret paleoenvironmental change in
their habitats. In light of the modern biodiversity crisis, studying such
reactions would help biologists and paleontologists understand how current
life may be affected my modern environmental change. Eastern Kansas provides
extensive outcrops to study, all containing abundant fossils of Pennsylvanian
and Permian tetrapods. My research to date has involved Early Permian
ephemeral pond communities and their responses to environmental changes
through both brief time periods (10s to 100s of years) and geologic time
(Hembree et al., 2004). These deposits preserve complete, articulated fossil
specimens of early tetrapods which are also ideal for use in phylogenetic studies. |
Articulated lysorophid
skeletons from the Permian Speiser Shale, eastern |
SEM photos of fossils collected from a Permian
ephemeral pond including lungfish teeth, unidentified tetrapod
teeth, ostracodes, and charophytes. |
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Copyright © 2007 Daniel Hembree Last revised: 5/2011 |
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