EARLY AND MODERN MAMMALIAN MASTICATION
What it is
For my PhD I am studying Didelphis virginiana's (the opossum's) tooth function, structure, and innervation. Teeth are the hardest bone in the body and are often preserved even when all other bones have been broken or worn away by time. They are also an often overlooked sensory system that encodes tooth "feel", temperature, and (read more about this below). How did this sensory system evolve?
The opossum is the lone metatherian (marsupial) of North America and the ideal comparison for eutherian (placental) tooth studies. Omnivory and a lower-than-average body temperature (for a mammal) have allowed opossum to survive and spread with humans.
Why it matters
Modern opossums are often used as a proxy for early mammals, as their teeth are morphologically similar to their Triassic counterparts. Early mammalian and pre-mammalian fossils display a number of novel morphologies. This includes complex tooth occlusion, a single set of replacement teeth, an ossified secondary palate, and an expanding cortex. These characters suggest a more complex mastication (chewing) behavior in these Triassic animals that may have allowed for more efficient breakdown of food. Thus, more calories could support endothermy and an expanding brain. Studying opossum chewing function and morphology allows us to test these hypothesis of early mammalian evolution.
Read All About it
Learn more about teeth in my guest post on the Anatomy To You Blog.
What it is
For my PhD I am studying Didelphis virginiana's (the opossum's) tooth function, structure, and innervation. Teeth are the hardest bone in the body and are often preserved even when all other bones have been broken or worn away by time. They are also an often overlooked sensory system that encodes tooth "feel", temperature, and (read more about this below). How did this sensory system evolve?
The opossum is the lone metatherian (marsupial) of North America and the ideal comparison for eutherian (placental) tooth studies. Omnivory and a lower-than-average body temperature (for a mammal) have allowed opossum to survive and spread with humans.
Why it matters
Modern opossums are often used as a proxy for early mammals, as their teeth are morphologically similar to their Triassic counterparts. Early mammalian and pre-mammalian fossils display a number of novel morphologies. This includes complex tooth occlusion, a single set of replacement teeth, an ossified secondary palate, and an expanding cortex. These characters suggest a more complex mastication (chewing) behavior in these Triassic animals that may have allowed for more efficient breakdown of food. Thus, more calories could support endothermy and an expanding brain. Studying opossum chewing function and morphology allows us to test these hypothesis of early mammalian evolution.
Read All About it
Learn more about teeth in my guest post on the Anatomy To You Blog.
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Tooth Histology
What it is Histology is the art of slicing preserved tissue into thin pieces, like salami. We mount this tissue on glass slides and apply different dyes and antibodies to mark different tissue structures, like proteins, blood cells, nuclei in cells, and much more. The tissue is then imaged (like the photo on the right). Why it matters Mapping out the tissues in and around the teeth is key for understand how this sensory system is structured. Interpreting histology slides is also a key skill in the medical fields. |
Opossum tissue stained with Picrosirius red , which stains collagen I and III. On your left you see a muscular artery (and one lone red blood cell in yellow), on the right is a nerve bundle. You can see that collagen is everywhere in the mammalian body. Picture taken by me.
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AUSTRALIAN AGAMID SKULL ONTOGENY AND MORPHOLOGY
What it is
Lizards are notoriously hard to identify in the fossil record. Now take five modern Agamid "dragons", all closely related (i.e. different species of the same family), and deflesh them. What do you have? That's what I am going to find out! I am currently studying an entire series of agamids, all in different stages of life.
Why it matters
We know comparatively little about the life-histories of these lizards, how they grow and develop, and if they all look "the same" inside the skull or completely different! Agamids are a great study system for phenotypic plasticity and selection pressure.
Read all about it
This research was recently published in the Journal of Herpetology, Volume 31, Number 3, September 2017.
What it is
Lizards are notoriously hard to identify in the fossil record. Now take five modern Agamid "dragons", all closely related (i.e. different species of the same family), and deflesh them. What do you have? That's what I am going to find out! I am currently studying an entire series of agamids, all in different stages of life.
Why it matters
We know comparatively little about the life-histories of these lizards, how they grow and develop, and if they all look "the same" inside the skull or completely different! Agamids are a great study system for phenotypic plasticity and selection pressure.
Read all about it
This research was recently published in the Journal of Herpetology, Volume 31, Number 3, September 2017.
OSTEOPATHOLOGY IN RHINOCEROTIDAE FROM 50 MYA TO THE PRESENT
What It Is
An osteopathology is the result of a trauma or a disease that happens to a bone. This could be anything from a break in the bone to infectious cysting. I am looking at a number of pathologies in the North American rhino lineage (about 50 to about five million years ago or so). Rhinos also increase in size from about the size of a large dog to a multi-ton animal over this same time span and I want to know how this exponential increase in mass affects osteopathological expression (such as arthritis).
Why it Matters
There have been very few projects that attempt to look at pathology in non-human animals on the population-level, and even fewer that consider the fossil record. Do these pathologies become so severe as to be an evolutionary constraint or is pathology independent of phylogeny? And what does this imply for the future of wild and captive animals?
Read all about it
This research was published in PlosONE, an open-access journal. Click here to read.
You can also check out this article in The Economist about this project!
What It Is
An osteopathology is the result of a trauma or a disease that happens to a bone. This could be anything from a break in the bone to infectious cysting. I am looking at a number of pathologies in the North American rhino lineage (about 50 to about five million years ago or so). Rhinos also increase in size from about the size of a large dog to a multi-ton animal over this same time span and I want to know how this exponential increase in mass affects osteopathological expression (such as arthritis).
Why it Matters
There have been very few projects that attempt to look at pathology in non-human animals on the population-level, and even fewer that consider the fossil record. Do these pathologies become so severe as to be an evolutionary constraint or is pathology independent of phylogeny? And what does this imply for the future of wild and captive animals?
Read all about it
This research was published in PlosONE, an open-access journal. Click here to read.
You can also check out this article in The Economist about this project!
FLUVIAL TAPHONOMIC BIAS
What it is
Taphonomy is what happens to a bone between death and final burial. This could be dispersal of bones by a predator, decomposition, or even the weather. Physical scattering processes, like dispersal through a steam or river, can be systematic, and thus measurable. We measured the greatest length, width, and height of over 5,000 fossils that were deposited in three ancient stream beds from Oregon to see if we could mathematically eliminate the systematic sorting effect of the stream (i.e. bias).
Why it matters
In order to understand ancient ecosystems, we first have to have an accurate count of the flora and fauna. Working backwards like this isn't as simple as directly comparing to modern ecosystems, because we don't know if the balances were the same back then (and they probable were not). We are much more likely to glimpse the future of climate change if we first understand the past.
What it is
Taphonomy is what happens to a bone between death and final burial. This could be dispersal of bones by a predator, decomposition, or even the weather. Physical scattering processes, like dispersal through a steam or river, can be systematic, and thus measurable. We measured the greatest length, width, and height of over 5,000 fossils that were deposited in three ancient stream beds from Oregon to see if we could mathematically eliminate the systematic sorting effect of the stream (i.e. bias).
Why it matters
In order to understand ancient ecosystems, we first have to have an accurate count of the flora and fauna. Working backwards like this isn't as simple as directly comparing to modern ecosystems, because we don't know if the balances were the same back then (and they probable were not). We are much more likely to glimpse the future of climate change if we first understand the past.
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