interested in the evolution of skull morphology and how
phylogenetic patterns, and developmental and functional
constraints underlie the origin of morphological diversity.
I take a broadly comparative approach and apply integrative
techniques by combining the fields of comparative anatomy,
developmental biology, experimental genetics, functional
morphology, systematics and paleontology to characterize
instances of morphological diversification in major
lineages of tetrapods. Currently I employ extinct and
extant amphibians to work towards these goals.
evolutionary developmental morphology
evolutionary morphology of the skull is shaped, in part, by
heritable genetic and developmental factors. I am
interested in the role of developmental evolution as a
source of morphological diversity.
My goals in this
area involve characterizing skull morphogenesis, and to use
a phylogenetic context to understand how changes produce
variation in adult morphology. I am currently investigating
the evolutionary development of the skull in amphibians. I
utilize GFP-mutant strains and injection methods to trace
developing cell lineages and observe structural
morphogenesis. This is followed by examining the expression
of patterning genes (e.g., Hox,
by, finally, taking an experimental approach to determining
the function of genes, through controlled perturbation.
This work identifies pathways that may be more or less
labile/plastic, as well as instances of the evolution of
novel morphogenetic pathways.
Morphological evolution in deep time
utilize the fossil record to document the consequences of
large-scale morphological evolutionary events, such as
those produced by heterochrony. It has been hypothesized
that modern amphibians diverged from Paleozoic amphibians
via heterochronic events producing a paedomorphic
morphology. However, the details of this process remain
My goal in this
area of research is to document (qualitatively and
quantitatively) the patterns of morphological change that
characterize transitions in the stem of modern amphibians.
My research works towards synthesizing previous work with
new data from other regions, such as the braincase,
treating the skull as an integrated whole. These data can
be used to generate hypotheses of the types of heterochrony
operating, thereby refining morphological models associated
with specific types of developmental perturbations. These
refined models provide a means for making comparisons with
transitions in other lineages to test competing
hypotheses that certain processes are expressed as
universal patterns in the evolution of morphological
diversity, or not.
and functional influences on morphology
addition to molecular and development constraints,
functional factors have a strong influence on morphology,
and can be powerful sources of morphological diversity.
Fossoriality (burrow excavation) is an example of a
behaviour that has strongly influenced morphology in
vertebrates. In fact, it is a rare example of a behaviour
that has evolved convergently in every major tetrapod
lineage, making it a unique system for exploring functional
influence on morphological evolution in a broad
goal in this
area includes documenting instances of convergent as well
as novel strategies for coping with functional constraints.
Recent work employing Finite Element Analysis (FEA) has
revealed how stress and strain are distributed throughout
the skull in caecilians, which will be used as a point of
comparison to test whether tetrapod skulls respond in
morphologically similar ways to similar functional
pressures. This research sheds light on the ability of the
skull to adapt to complex behaviours and to diversify to
fill specialist niches in ecosystems.
of the morphology and development of the braincase of
caecilian amphibians (Gymnophiona)
Cranial Anatomy of Ennatosaurus
Casiedae) from the Permian of Russia and the evolutionary
relationships of Caseidae
1) The evolution of the
process of keratinization: comparative histology of
amphibian and reptile claws
2) The evolution of
morphology in the terminal phalanges of non-therapsid