Donald Esker
Member
I'm not sure this is the right place to post, but here goes nothing!
I'm a paleontologist studying Ice Age animals, and I want YOU(r tortoise) to help me solve an ancient mystery! Some science-y talk is coming up -- you can skip to the *** for the executive summary, if you like! ;-)
I'm hoping for your help. My name is Don Esker; I'm a doctoral candidate at Baylor University in Texas, doing my dissertation on Waco Mammoth National Monument (WMNM) http://www.nps.gov/waco/index.htm. This is an ice-age fossil site where many different creatures were found. One of the more enigmatic is an animal called Hesperotestudo crassiscutata. This was a tortoise -- perhaps related to Gopherus -- that lived on this continent during the Late Pleistocene. It's often called the North American giant tortoise. How giant? That's the problem. Most of the remains are highly fragmentary, and the handful of well-preserved specimens don't preserve soft tissue so the animal's weight can't be measured directly. Published weight estimates seem to be based largely on guesswork and rough comparisons with modern giant tortoises. For my purposes this isn't good enough. I need to have a tightly-constrained estimate of the WMNM specimen's mass so that I can model its thermal properties to find out how long it could tolerate sub-optimal temperatures. If I could manage that, it could function as a more reliable climate proxy.
Getting a good weight estimate isn't easy, however. The terms in morphometrics vs. weight curves vary between species. The differences might be small, but for an animal with a meter-long carapace these equations produce weight estimates that differ by a factor of 2 or 3. To resolve this and find the best equation for predicting H. crassiscutata's weight, I'd like to do something like this:
1. Develop morphometrics* vs. weight curves for as many testudinid species as possible.
2. Use multivariate analysis to determine whether the terms in a species' morphometrics vs. weight curve are controlled primarily by taxonomy, maximum adult size, or a mixture of the two (I'm pretty handy with PaSt).
3. Select the curve most appropriate for H. crassiscutata.
4. Reconstruct the probable morphometrics of as many museum specimens as possible to better understand the ontogeny and allometry of H. crassiscutata.
5. Reconstruct the weights of an average H. crassiscutata and the Waco specimens.
6. Model the thermal properties to determine the climate tolerance of an average specimen and the WACO specimens.
7. Compare with climate models for as much of the Pleistocene as possible to produce a range chart for each MIS.
8. Reevaluate previous papers that have used H. crassiscutata as a paleoclimate or biostratigraphic indicator in light of this new data.
* [The morphometrics would include the dimensions of the individual bones that make up the shell, the pattern of the horny scutes that cover them, and the dimension of cranial and limb elements.]
*** LONG STORY SHORT: I'm trying to find out how much an extinct Ice Age tortoise weighed when it was alive. To do this, I need to understand how a tortoise's proportions change as it gets bigger and heavier. For that, I need a LOT of tortoise measurements, of every species I can find!
And this is where you, Gentle Reader, can help! Are you willing to take a few measurements of your tortoise and send them to me? I'd need the carapace length and width, the dimensions of the scutes, etc, in addition to the weight. It'd be great if I could get every measurement from every tortoise, but you can still contribute just giving me the species, age, sex, carapace length, and weight of your shelly companions! If you're interested in participating, vote 'yes' below and email me at [email protected] -- I'll send you a list of measurements! Volunteers would get mentioned in the acknowledgements (collectively) and named specifically in the data that get's published with the study.
Cheers,
Don Esker
I'm a paleontologist studying Ice Age animals, and I want YOU(r tortoise) to help me solve an ancient mystery! Some science-y talk is coming up -- you can skip to the *** for the executive summary, if you like! ;-)
I'm hoping for your help. My name is Don Esker; I'm a doctoral candidate at Baylor University in Texas, doing my dissertation on Waco Mammoth National Monument (WMNM) http://www.nps.gov/waco/index.htm. This is an ice-age fossil site where many different creatures were found. One of the more enigmatic is an animal called Hesperotestudo crassiscutata. This was a tortoise -- perhaps related to Gopherus -- that lived on this continent during the Late Pleistocene. It's often called the North American giant tortoise. How giant? That's the problem. Most of the remains are highly fragmentary, and the handful of well-preserved specimens don't preserve soft tissue so the animal's weight can't be measured directly. Published weight estimates seem to be based largely on guesswork and rough comparisons with modern giant tortoises. For my purposes this isn't good enough. I need to have a tightly-constrained estimate of the WMNM specimen's mass so that I can model its thermal properties to find out how long it could tolerate sub-optimal temperatures. If I could manage that, it could function as a more reliable climate proxy.
Getting a good weight estimate isn't easy, however. The terms in morphometrics vs. weight curves vary between species. The differences might be small, but for an animal with a meter-long carapace these equations produce weight estimates that differ by a factor of 2 or 3. To resolve this and find the best equation for predicting H. crassiscutata's weight, I'd like to do something like this:
1. Develop morphometrics* vs. weight curves for as many testudinid species as possible.
2. Use multivariate analysis to determine whether the terms in a species' morphometrics vs. weight curve are controlled primarily by taxonomy, maximum adult size, or a mixture of the two (I'm pretty handy with PaSt).
3. Select the curve most appropriate for H. crassiscutata.
4. Reconstruct the probable morphometrics of as many museum specimens as possible to better understand the ontogeny and allometry of H. crassiscutata.
5. Reconstruct the weights of an average H. crassiscutata and the Waco specimens.
6. Model the thermal properties to determine the climate tolerance of an average specimen and the WACO specimens.
7. Compare with climate models for as much of the Pleistocene as possible to produce a range chart for each MIS.
8. Reevaluate previous papers that have used H. crassiscutata as a paleoclimate or biostratigraphic indicator in light of this new data.
* [The morphometrics would include the dimensions of the individual bones that make up the shell, the pattern of the horny scutes that cover them, and the dimension of cranial and limb elements.]
*** LONG STORY SHORT: I'm trying to find out how much an extinct Ice Age tortoise weighed when it was alive. To do this, I need to understand how a tortoise's proportions change as it gets bigger and heavier. For that, I need a LOT of tortoise measurements, of every species I can find!
And this is where you, Gentle Reader, can help! Are you willing to take a few measurements of your tortoise and send them to me? I'd need the carapace length and width, the dimensions of the scutes, etc, in addition to the weight. It'd be great if I could get every measurement from every tortoise, but you can still contribute just giving me the species, age, sex, carapace length, and weight of your shelly companions! If you're interested in participating, vote 'yes' below and email me at [email protected] -- I'll send you a list of measurements! Volunteers would get mentioned in the acknowledgements (collectively) and named specifically in the data that get's published with the study.
Cheers,
Don Esker
...I was just looking up "dino torts" myself. Then I was side tracked by tortoises wearing Dino sweaters. 
