Category Archives: Paleontology

Blatherings on Mammoths

On Saturday, I’ll be giving an hour-long presentation to some seniors (you know, the over 55 set) on the topic of “Woolly Mammoths in New York State.” Well, it’s a pretty nebulous topic, and I only have an hour, so that means I can direct my presentation in pretty-much any direction I want.

You know some paleobiology is going to go in there. What is the difference between a mammoth and a mastodon, for example. And why are they extinct? Someone’s going to ask why we don’t find dinosaurs in New York. Naturally, I have to talk about geochemistry, too, since I might have done a little work with that (see my other blog post).

I guess the obvious thing for me to start with is to explain what a mammoth is, ‘cause it’s not just a big fuzzy elephant!

What is a mammoth?

Mammoths, mastodons and elephants are in a larger group of mammals called proboscidians, so named in reference to their big long noses. Mammoths and elephants are actually very similar, in skeletal and in tooth structure. Mastodons have very different looking teeth, which is an important distinction between to two ice-age dwelling proboscidian groups.

Mastodon, Mammoth, and Elephant for comparison

Mammoths (and modern elephants) have teeth composed of a series of plates, that form a washboard-like grinding surface which is perfect for the foods that they eat. Both elephants and Mammoths are (or were) grazing animals (like cattle are today). Mastodon teeth are smaller and have several huge cusps, which aren’t so great for grazing but are good for eating leaves and such. Mastodons were browsers, much like giraffes, for example. Because they had different diets, they were able to coexist.

Asiatic elephant tooth
Mammoth teeth still in the jaw
Mastodon tooth (left) and Mammoth tooth (right)

The structure of the teeth is the easiest way to distinguish between mammoths and mastodons, but their skeletal structures are also distinct. Mammoths tend to be taller in the front end than in the back end, their heads held high – the top of the head being slightly higher than the shoulder. Mastodons are a little stockier, with their head often slightly lower than the shoulder.

Mastodon skeleton (left) and Mammoth skeleton (right)

Types of Mammoths

Mammoths in North America fall into two species: the Woolly Mammoth (Mammuthus primigenius) and the Columbian Mammoth (Mammuthus columbi). The woolly mammoth was smaller than the Columbian mammoth, and a lot hairier. Woolly mammoths lived further north, closer to the edges of the great glaciers that once covered much of northern North America. Columbian mammoths stayed further south. Only woolly mammoths would be expected in what is now New York State.

Distribution of Columbian Mammoths (left map) and Woolly Mammoths (right map)

What’s special and unique about mammoths (and mastodons and elephants)?

Several things stand out as interesting about proboscidians. Here are some fun facts:

  • Mammoths and elephants have only one tooth on each jaw (upper, lower; right, left) in wear at any one time. We have all of our teeth in use all the time.
  • There are only six teeth in each jaw (upper, lower; right, left) that an elephant or mastodon ever gets. They grow into the mouth one at a time from the back and fall out the front when they’re worn out. Once the sixth tooth is worn out, there’s no more teeth and the mammoth or elephant starves to death.
The pattern of tooth replacement in the jaws of elephants
  • Mastodons have the same pattern of tooth replacement, but usually have more than one tooth at a time in use. Their teeth don’t wear out as quickly though, because they eat softer food.
  • Proboscidians are in a larger group of mammals called ‘subungulates’ which are grouped together because they have hoof-like structures on their feet, but they’re not quite hooves.
  • Some of the closest relatives to elephants, mammoths, and mastodons are manatees! Manatees are also subungulates and have hoof-like structures on their front flippers. They also have the same sort of conveyor-belt tooth replacement, but they aren’t limited to only six teeth.

When and why did they go extinct?

About 10,000 years ago, mammoths and mastodons, plus a lot of other large mammals that live in North America (woolly rhinos, giant ground sloths) went extinct (Wikipedia article). Most of the animals that went extinct were huge, so we refer to them as “Megafauna.” No one is certain why this happened, but it did coincide roughly with the melting back of the continental ice sheets as well as the appearance of humans in North America. It is an interesting point of controversy. There are two main camps here and then a few extra ideas (maybe the lunatic fringe?).

Main hypotheses:

    • Human overhunting

It is possible – even likely, knowing how we as humans are – that humans might have been responsible for the loss of the mammalian megafauna. We have been known, once in a while, to over-use resources, and it is known that humans actively hunted members of the ice-age megafauna, like mammoths.

  • Climate change

We also know that climate was changing rapidly then, warming up after the end of the ice-age. The ice sheets melted back and the landscape was changed. Organisms had to adapt, and big animals like the mammoths likely had a hard time adapting.

These both seem like reasonable hypotheses. So which is it? Most scientists straddle the fence on this one: Well humans were hunting a lot, and the animals were already in trouble because of the climate change…

 Other ideas:

    • Meteor impact

Because asteroid impacts have resulted in many extinctions in earth’s history (like the extinction of dinosaurs), it seems sensible that this extinction might also have been caused by an impact. There is some evidence that there might have been an impact, but some things about the extinction event are cause for skepticism. For example, why did ONLY the large mammals go extinct?

    • Second-order predation

Here the idea is that not only did humans decimate the populations of the prey animals, they also hunted the predator animals (like saber-tooth tigers). Without the primary predators, the prey animals rapidly overpopulated the area, destroying their own resources and thus killing themselves off.

  • Hyperdisease

Humans coming from another continent would have brought a few ‘friends’ with them. Perhaps the humans brought along their own animals that carried diseases for which the native animals had no immunity. This could very quickly decimate the native population as has been seen when humans and their livestock have populated new places in modern times.

How can we find mammoths?

A common question that people ask of paleontologists like me is “How do you know where to look?” I have a standard answer for that: We look at maps, maps that geologists before us have drawn showing the various rocks exposed in an area, describing those rocks, defining their ages through various means. We look at the maps for rocks that should have the right fossils in them, and then we go out to the rocks in the real world and walk around until we find something.

At times it’s a little more sophisticated than that. We can use remote-sensing/sattelite methods and find the most probable areas using neural networks on computers.  Many times though, it’s a whole lot less sophisticated. Sometimes, you just walk across a field and kick something and when you look down, it’s a fossil bone. Mammoths are often found when people bring in backhoes to dig a hole for a new pool. Their digging and suddenly there’s a bone. They were digging a new reservoir in Snowmass, Colorado, and they found what’s now called the “Snowmastodon” Site!

What can geochemistry teach us?

My own research centers on the chemical constituents of tooth enamel in fossil animals. From that, we can learn a lot about extinct species, including what their food preferences were, what the weather was doing while they were alive, and how their teeth might have grown. One of my undertakings is described here. I presented my results at the Society of Vertebrate Paleontology annual meeting a couple of weeks ago, to find out that the project I had done has actually been done before (just never published). My results were quite different, however. Through discussion with other scientists, I think we all understand the source of the differing results. Now if I can just get them to publish their work!

Recent discoveries: Mammoth mummies!

Of late, Siberia has been yielding numerous mummies of mammoths (and other mammals). The far North is a good place to look for mummies of any animal, because the cold temperatures will preserve the animals like a giant ice-box. The ice itself can encase the mummy, keeping it from becoming a meal for modern scavenging animals. Yuka  Baby mammoth

 Cloning of Mammoths

Because of the exquisite preservation of the mummified mammoths, there has been talk of attempting to clone mammoths. So long as the nuclei of cells are not totally destroyed by freezing or decay, a scientist could extract the DNA and create a clone. Will this be done? Should it be done?

SVP – Scenes written screenplay style

Because I’m weird like that, I decided to write up some bits of the 2012 annual meeting of the Society of Vertebrate Paleontology in a screenplay format.

This would never make a good movie or TV show and here’s why: NO CONFLICT! There’s over 1000 of us there, and we’re all so happy to be there that there is no conflict. Nothing happens! Everyone is happy.

So, it’s a lousy script, but it highlights some of the things that go on at these meetings, in its own special bizarre way…

Some names have been changed to protect the innocent, and things are written mostly how I remember them, which might not be reality. If you think I might be talking about you, well, I might be!

Also, please forgive the formatting errors. They’re there. I couldn’t make it work right. Poo.

By the way, these things really did happen. …mostly.

—–

#2012SVP: The movie

EXT. MAJOR HOTEL – NIGHT

PENNY HIGGINS, middle-aged paleontologist exits an airport shuttle bus. She gathers her belongings, pays the driver and enters the hotel.

INT. MAJOR HOTEL – CONTINUOUS

Penny passes through sliding glass doors and is met by the din of loud discussion. She looks toward the bar and sees a crowd within, the source of the noise. She smiles and nods. She knows the sounds of paleontologists.

PENNY
(to herself)
Paleontology. How I love thee!

INT. DARKENED CONFERENCE ROOM – DAY

Penny is checking Twitter on her phone. A tweet from the host society shows up “Beware the flatulent chairs. Sit carefully.”

Penny raises slightly from her seat and sits back down hard. The chair toots. Penny eyes the person sitting beside her. He’s looking back, eyes wide.

PENNY
Oops! Excuse me!

The man smiles and returns his attention to the speaker.

Another person enters the room and sits in front of Penny, causing his chair to emit a loud farting noise. Penny struggles to contain her laughter and quickly re-tweets the earlier tweeted warning.

INT. CONVENTION CENTER – POSTERS – DAY

The room is arranged with several rows of posters, presenting scientific results. Between the rows are packed hundreds of paleontologists, discussing the posters among themselves and with the authors. The room is a cacophony of voices. Nearly everyone has a drink.

DAN
So tell me your story here.

PENNY
(points to poster)
Well, our data seem to show that this takes about one year. But I’m told you’ve already done this.

DAN
Yes.
(grins sheepishly)
We got our data ten years ago. We just haven’t published it yet.

PENNY
Well, you need to publish it! Your data sound better than mine. And your results make better sense.

DAN
We’ll get to it.

PENNY
I’m gonna e-mail you every week until it’s published

DAN
Maybe you should.

Dan moves on. One of Penny’s friends approaches.

JUDY
How goes it?

PENNY
Yeah. This work’s been done already.

JUDY
What happened?

PENNY
This is what happens when people don’t publish.

JUDY
That stinks.

PENNY
At least it wasn’t an oral presentation – or worse: a rejection from a journal. We move on.

Judy pats Penny on the shoulder.

JUDY
It happens.

INT. DARKENED CONFERENCE ROOM – DAY

A video is playing of a Hyena eating a big chunk of meat and bone. Penny furiously tweets what she is seeing. Numerous other tweets scroll past, highlighting the same thing, each containing the phrases “bone cracking” “hyena” and “pig neck”. Penny grins, relishing the morbidity of her paleontological colleagues.

Someone sits down near Penny, causing the chair to fart. Restraining laughter, Penny heads out to find coffee.

INT. CONFERENCE ROOM – DAY

A silent auction is being set out. Items are spread out over several tables throughout the room. People are running around sorting items and arranging them in an appealing way.

Penny enters lugging a hefty wooden rocking-dinosaur.

PENNY
Yup. This is it. You’re going to a new home.

Penny looks around and finds who she’s looking for.

PENNY
Brent!
(indicates the dinosaur)
Silent or live?

BRENT
Live.

Penny hoists the dinosaur onto a table in front of the stage, where the live auction will take place later in the day.

INT. MEETING ROOM – EVENING

Six people stand around, four of whom are dressed as characters from the movie and comics “The Avengers.”

Penny walks out of a back room in a white and black pleather body suit.

PENNY
I’m gonna cook in this thing!

BECCA
Now, who are you?

PENNY
Mockingbird. From the comics.

Penny dons her long, platinum blonde wig and adjusts it on her head.

BECCA
Do you have an extra hair tie?

PENNY
(laughs)
I only have long hair when I’m wearing a wig!

BECCA
(laughs)
Oh! Oops!

There’s a knock at the door. Thor and Loki have arrived. Tony Stark leaves to set the stage for the entrance of the Avengers.

Becca’s phone bings.

BECCA
It’s time.

THOR
Let’s go.

INT. HOTEL BAR – NIGHT

The Avengers (paleontologists in costume) enter the bar to hoots and congratulations from the other paleontologists there.

Thor, Loki, and Penny approach the bar to get a drink.

THOR
Whatever you want. My treat.

A woman and her husband are seated nearby and are delighted to see the three costumed paleontologists standing there.

WOMAN
Oh, please! Let us buy! We’re so happy to meet you!

The husband nods and turns away, disinterested. The woman continues to gush.

WOMAN
I’m so glad to have met real paleontologists! Y’know, on our beach I’ve found some really interesting fossils!

Loki and Penny look knowingly at each other. Thor moves off into another conversation.

WOMAN
I’ve seen fossils of a baby bird being born.

Penny and Loki feign interest. There is little doubt in either one of their heads that what the woman has seen is not a bird being born.

LOKI
We’re glad you got to meet us. We’re pretty tired, though. We just did a big auction and we’re winding down.

WOMAN
Oh sure! Oh sure! I understand! I just think it’s great that you’re here. It’s like a sign or something!

LOKI
Well thank you for the drinks!

WOMAN
Sure! I hope we can talk more!

Loki and Penny roll their eyes at each other, then join Thor in his conversation.

INT. DARKENED CONFERENCE ROOM – DAY

Penny looks at her phone, checking the conference twitterfeed. A tweet pops up promising a blooper reel at the end of a talk. Penny is intrigued, and leaves quietly.

INT. DARKENED CONFERENCE ROOM – MOMENTS LATER

Penny takes a seat in another conference room (though it looks identical to the one she just left). She settles in, phone in hand, ready to be wowed.

The presentation begins.

SPEAKER
It’s hard to motivate an alligator to run.

The audience laughs. Soon videos are being shown of alligators and crocodiles running in a Plexiglas chute.

Penny looks at the twitterfeed. Multiple people are tweeting about this presentation. Penny smiles.

SPEAKER
And, as promised, the blooper reel.

On the screen are shown video clips of the alligators and crocodiles escaping from the chute and lunging at the camera. The audience laughs. Tweets fly.

INT. BANQUET ROOM – EVENING

Several hundred paleontolgists are gathered for a catered meal and a short awards ceremony. The meal has been eaten and the few remaining plates have been removed. Attention turns to the President of the Society of Vertebrate Paleontology. She announces several award winners. As the evening continues, the awards become more significant.

PRESIDENT
The Colbert Student poster prize goes to Stephanie Crofts.

People rise to give a standing ovation. As all sit down, a series of toots and tweets are heard.

PRESIDENT
And the Romer Prize for student research goes to Jack Tseng!

The crowd rises again, clapping and shouting. With sitting, the chorus of toots and farting noises is louder. There is audible chuckling. Penny looks at her twitterfeed. A new hashtag has arisen: #squeakyseat

PRESIDENT
And the Romer-Simpson Medal goes to Philip Gingerich!

The crowd rises once more, delighted for their long-time colleague. The tooting and farting sounds as people sit are very loud this time. Clearly people are intentionally sitting hard to make the noise louder. Penny is laughing so hard, tears are coming from her eyes.

INT. HOTEL LOBBY – MORNING

Penny walks away from the front desk. She pauses, looking back.

PENNY
(to no one)
Next year. L.A. See you soon.

Society of Vertebrate Paleontology annual meeting wrap-up

Ah! The annual meeting of the Society of Vertebrate Paleontology (SVP)! My favorite thing in the world! Four days of paleontological bliss, where I don’t have to define terms or defend your chosen profession. Where you can escape from the forced isolation of being the only paleontologist in your department, or worse, in your city. Where evolution is accepted and assumed rather than danced about using clever euphemisms. And where you can trot out your *really* bad science puns and everyone laughs.

Overall, this year seemed no different than other years, but some things really stood out to me. Because I chose to live-tweet sessions, I felt more connected to the happenings at the meeting than I ever have before (and got to make some new friends, to boot!) And, incredibly, there was not a single talk that I went to that I felt was poorly executed. Usually, there’s one or two a day that are agony to sit through, for whatever reason, but this year it didn’t happen. Every talk was not only enjoyable, but offered something worth tweeting about. A good chunk of the meeting was Storify-ed by Jon Tennant (@protohedgehog on Twitter), so you can see what we were doing.

The venue was splendid. I enjoyed the convenience of all the sessions being side-by-side, and the posters were less than 3 minutes walk from the oral session. Even better, the hotel (if one chose to stay there) was less than 5 minutes from any of the sessions. And (after a little nudging), there was even free wi-fi! Perhaps the best (or worst) part of the venue was the seats that apparently had whoopie-cushions built in. There was a lot of accidental tooting, which was finally recorded here.

Highlights of presentations included video of a hyena eating a pig neck in about 30 seconds (noting the bone breaking capabilities of hyenas) and several videos of crocodiles and alligators running (including a blooper reel!).

For me, one of the biggest parts of SVP is the annual auction. I’ve helped with the auction ever since I started graduate school and finally became a member of the auction committee sometime soon after getting my Ph.D. At first, it was always just a matter of helping with the set-up, but over the last 10 years, we’ve started dressing in costume with a theme for the live auction each year. Those of us on the committee put a great deal of time and effort (and sometimes money) into constructing our costumes. The theme is usually established sometime during the summer prior to the meeting, and we rush to create our costumes while simultaneously preparing our professional presentations for the meeting as well. This year, the theme was the Avengers. I chose to dress as Mockingbird, who did not appear in the movie, but has been in a few of the comics. I liked the look of her costume, which is why I chose her. She also has a Ph.D., so how can I go wrong?

Auction, Avengers-style.

This year, I brought back an item I bought back in 2004: a big wooden rocking dinosaur. My son was an infant then. Now, at eight, he’s not so into the dinosaur. Hopefully, it’s off to make some other kid really happy and the auction winner will bring it back when his child has out-grown it.

The ol’ dino-rocker is off to a new home!

The auction raises money for various programs at SVP that support students. I’m glad to be able to help the society in this way. This year the auction made $22,700!

Dino-Thor?

As usual, I was able to drum up some new work for the lab while I was there, and perhaps start some new collaborations. I’m suddenly thinking an awful lot about microwear on teeth. I found out that what I presented was actually old news — only that the folks who had already done the same project kinda hadn’t bothered to publish it yet. (grumble) All told, this was one of the most productive meetings I have ever had. And somehow, I didn’t get sick during the whole event. I’m still healthy, two days after getting home. How’d that happen?

Well, while the iron’s hot, it’s time for me to attack some old research projects. There’s a short paper burning in me about the problems with the taxa Phenacodus and Tetraclaenodon. Then there’s that huge dataset that I tabulated as a postdoc that still hasn’t seen the light of publication. Yeah, I should get on that. I love this feeling of frantic motivation. I hope it lasts!

If you’re not satisfied with what I have to say about the meeting, then check out what others have said, (below). I’ll be updating this as I hear about other people’s posts.

What do Vertebrate Paleontologists Talk About, by Bora Zivkovic (@BoraZ on Twitter; Scientific American Blogs)

SVP, you’re so silly, Tarchia (Pseudoplocephalus Blog)

 

Society of Vertebrate Paleontology invades Raleigh!

This post was written a while ago, but my blog (for whatever reason) was down. It’s fixed now, so I’m publishing it – after the fact. My musings on the meeting will come later..

—–

I’m currently in Raleigh, North Carolina, sitting in my hotel room, winding down after a crazy-awesome day-and-a-half. I’m here for the annual meeting of the Society of Vertebrate Paleontology, which is, hands down, my favorite meeting. Every year I go to this meeting no matter what the cost. (I’ve been going to this meeting since 1994, and only skipped a few when I was a poor, starving graduate student.) The Society of Vertebrate Paleontology is the one professional organization that I likely will never allow myself to not be a member of.

This year, the meeting is proceeding as it always does for me: Interacting with colleagues; learning about new methods; developing collaborations; making new friends. I brought some research (as I always do) and will be presenting it this afternoon in a poster session. Tomorrow will be busy as the Friday of the meeting always is, because of the annual auction and that I’m an auction committee member.

What’s different about this year over the others is that I’ve decided to join the ranks of those who use social media to disperse what is being discussed in sessions to the wide world. I’ve been ‘live-tweeting’ sessions: commenting on speakers using the hash tag #2012SVP so that other interested parties can know what’s happening if they couldn’t come to the meeting or if they’re just in the room next door listening to someone else. I don’t say much, only commenting on things that really grab my attention and I think others out there would be interested to know.

This experience has been great so far. Over the past year I’ve begun to think that social media and science outreach was a better fit for my interests and passions than hard-core research (even though I do plenty of research and have new results to present every year). The interactions (face-to-face and electronic) I’ve had during this meeting have been amazing and now, more than ever, I’m realizing that my suspicions are true. Research is great. Sharing it with others is even better.

There are two and a half more days to the meeting. I expect my feelings will grow stronger as this time goes on. I like where I am right now. I like where things are going. Stay tuned!

Rodents of Unusual Size

As I was driving home from work yesterday, I was pondering what the next great bit of science would be that I should publish. I started thinking about this project that has been back-burnered for a while.

Projects in the sciences get back-burnered for many reasons. This particular one has been set aside as I wait for results from other colleagues from other institutions. This happens, and is a common occurrence in the sciences. But as I was driving, I realized that part of the project is complete and can be its own paper in the absence of the contributions from the others for the greater project.

Co-authors, get ready. There’s a manuscript coming together by ME!

So, what’s it about? And why is the title of this post “Rodents of Unusual Size”? ROUSes don’t exist anyway, so what am I worried about?

Well, there are some big rodents out there. The largest modern rodent is the Capypara (or Carpincho), which roam around in South America. These rodents average about 50 kg (110 pounds), so they are fairly large. But in the ancient past, South America hosted even larger species of rodents, including Arazamys, Isostylomys, and Josephoartigasia. The latter, is thought to have potentially weighed 1000kg (2200 pounds)! Now that’s a rodent of unusual size!!

Capybara Grazing (by FinlayCox143)

A common research question that I answer with my type of research is “what did the animal eat?” I can get at this using geochemical analysis of tooth enamel. The larger project that my colleagues and I are working on seeks to answer the question, “What did these giant fossil rodents eat?”

The obvious answer, of course is, “Anything it wants!” But we want to be a bit more specific. So how do we do this? By studying the isotope geochemistry of tooth enamel.

Diet recorded in tooth enamel

We joke in isotope geochemistry that “You are what you eat, plus a few permil.” When I’m analyzing samples, I’m comparing the amount of Carbon-13 (’heavy’ carbon, but not the radioactive stuff, Carbon-14) relative to the amount of Carbon-12 (the common carbon in the world). Slightly less than 99% of all carbon atoms in the universe are Carbon-12. Around 1% of all carbon atoms are Carbon-13. (And whatever is left is the radioactive Carbon-14). A mass spectrometer can measure the relative amounts of Carbon-12 to Carbon-13 and gives us a number, called a ‘delta value’ in units of ‘permil’ (‰).

We write this like: δ13C = -14‰ (said “delta 13-C equals minus fourteen permil”)

Depending upon what you’ve just measured the isotopes from, this delta value can be interpreted in a number of ways. For diet and tooth enamel, it goes like this:

Plants, in general, use one of two types of photosynthesis. These two types are called C3 and C4. C3 plants are typically trees and bushes (or occasionally grasses) that live in cooler moist environments. C4 plants are typically plants especially grasses that live in arid environments. (This is an over-generalization, of course, but is usually our first assumption.)

Luckily for us, C3 and C4 plants have different δ13C values. C3 plants are usually about -27‰; C4 plants usually around -13‰.

Now, let’s say an animal comes along and eats these plants. You are what you eat, they say. Plus a few permil… In the case of mammal tooth enamel and plants, it’s plus 14‰. So a bison grazing on C4 grasses has a tooth enamel  δ13C of about 1‰. A horse that prefers to eat the bushes with have a tooth enamel  δ13C of about -13‰.

The difference in  δ13C in tooth enamel reflects a difference in diet. In general, we assume that animals that show a C4 diet (tooth enamel  δ13C around 1‰) probably were grazing (grass-eaters) and those that show a C3 diet (tooth enamel  δ13C around -13‰) were probably browsing (leaf-eaters). Of course, there are animals that do some browsing and some grazing (horses in particular). We can tease out the relative amounts of grazing and browsing in a single animal too.

So the plan is to look at the tooth enamel of the giant rodents Arazamys, Isostylomys, and Josephoartigasia and figure out if they were browsing or grazing. We might assume that they were grazing, since some of the largest land mammals are also grazers (like elephants), but they might also be browsing, just to eat enough food to fuel such a giant body!

Capybara diets

It’s always a good idea to ground-truth your assumptions whenever you have the opportunity. There are lots of assumptions that go into inferring that an animal is either a browser or a grazer when there is only isotopic data to look at. We decided it would be worthwhile to examine the isotopes in modern giant rodents to see if our predictions and assumptions are borne out. Since capybaras are the largest modern rodents, we decided to study them.

Capybaras are known to be grazers. We can sit and watch them graze on grass in an environment where there is lots of C4 grass to be eaten. We also know that there are some C3 grasses in the places where capybaras live, but we might assume that since the majority of grasses are C4, then the majority of the capybara’s diet is C4 as well. Thus we predict that the tooth enamel  δ13C from a capybara would be around 1‰.

Well, guess what?

Capybaras selectively eat the C3 grasses. Their tooth enamel only reflects a C3 diet! But we didn’t know this until we ran the isotopes! We ran a couple hundred samples, so we know it’s not an error. This was completely unexpected. Seems like we have a problem, right?

Well, really, it’s not the end of the world. It is what it is. This is how science works. We know that capybaras are grazers, but if all we had to go on was tooth enamel, we’d get it wrong.

But we have other things. We have the shape of the teeth themselves. Long and rootless teeth are common in animals that eat an abrasive diet – and is a common characteristic among grazing animals. Have you ever looked at a horse tooth? Most rodents, including the capybara, have these long and rootless teeth.

We can also look at microwear on the surface of the tooth. An abrasive diet (actually, any diet) will scratch and wear the tooth surface, leaving tell-tale marks that we can observe using microscopes. Specific types of marks are associated with different diets: grazing, browsing, fruit-eating, etc. This is the realm of my colleagues. They are looking at the microwear on the teeth of the giant fossil rodents. Hopefully, they’ll get on that soon. I ought to start bugging them.

What does an ROUS eat?

The isotopic analyses from the fossil giant rodents are done. But in the light of what we learned from the capybaras, the interpretation is sketchy. I can’t say more than that right now. Until we have the microwear data, all we can say is “Huh.”

In the meantime, though, the conclusions of the capybara study are important and need to be published, since they kind of shake up some of our basic assumptions for interpreting diets from carbon in tooth enamel. Now all I gotta do is decide which journal. Hmm.

Why I do what I do: Education, one victory at a time.

I had a great experience the other day – the kind of experience that all educators want. I converted someone.

I didn’t know if they needed or wanted conversion, but they were skeptical of what I was presenting. And I – entirely unwittingly – provided that bit of information that converted them from ‘skeptic’ to ‘believer.’

A fair question to ask at this point is, “What didn’t they believe in?” We’ll get there.

I had been invited to give a talk/presentation on the nebulous topic of ‘dinosaurs.’ The group that invited me had recently had a lively discussion about dinosaurs, but found that they still had questions for which no Google search provided adequate answers. So there I was.

I was a little trepidatious, because, despite the fact that I am a ‘vertebrate paleontologist,’ I really don’t know a whole lot about dinosaurs. There are thousands of 9-year-olds who know more about dinosaurs than I do. Mammals are my thing. But they sent me a list of questions, and I realized that I could address most of them easily. Most had less to do with dinosaurs than they did about the science of paleontology.

As it happened, the group was a delight. We had a fabulous time talking about how the turkey you eat at Thanksgiving really is a dinosaur. We talked about how bones and teeth were made of minerals (essentially rocks) and that’s why they don’t rot (and why they’re preserved as fossils). We talked about what was wrong with Jurassic Park. We talked a bit on how we name, and how we recognize, new species, and about some of the ‘mistakes’ paleontologists have made along the way. We talked about tracks and pseudofossils. Really, there were few topics in paleontology that we didn’t cover, and it was only an hour-and-a-half presentation.

With about 15 minutes to go, the skeptic was revealed (paraphrased):

‘If humans and dinosaurs never co-existed – so humans never saw dinosaurs – how do we know that dinosaurs are real? How do we know that they ever really existed?’

From how the question was asked, I could tell that our skeptic was genuinely curious – not intent on discrediting me or the science, but honestly confused. And as I listened, I was frankly boggled by where the confusion was.

You see, I’ve been at this so long that the reasons why we know that dinosaurs existed seem so self-evident, I don’t understand how people don’t see them. However, one thing I have learned in recent years while teaching introductory geology courses: It is impossible to remember what you didn’t know before you started your studies. That is to say, I don’t remember not knowing how we determine relative ages of rocks. I don’t remember not knowing that rocks exposed on the surface are of all different ages. I finally realized that our skeptic didn’t know these things any more than I did 20+ years ago. I also realized that the answer our skeptic wanted didn’t come from paleontology, but from geology. No wonder Google wasn’t being helpful.

So I stepped back and described Hutton’s original observation of the unconformities in Scotland and how this helps us understand of the depth of geological time. Then I explained how some basic principles (original horizontality, superposition, cross-cutting relationships) can help us put rocks in the correct chronological order. Then I drew a stack of rocks and showed that humans were at the top of the stack and dinosaurs were at the bottom.

And the skeptic’s eyes opened wide. ‘I get it! There were dinosaurs!’

Others in the room were delighted. They’d been trying to ‘prove’ the existence of dinosaurs to the skeptic for a while, and here I had done it with two drawings in five minutes.

I was never my intention to go in there and ‘convert’ anyone. (In fact, I hesitate to use the term ‘convert,’ only that the term was being tossed around by everyone in the room when the presentation was done, including by the skeptic.) I was simply there to answer people’s questions about dinosaurs. I don’t care what they believe about evolution or the age of the earth or anything. I was there to be a better database than the world wide web. I think they got the answers that they wanted, and then some.

And I got that fantastic satisfaction that we all yearn for as educators: Somebody learned something – something that may well alter their world view – and thanked me for it.

Oh, yeaaaaah!

How do you measure body temperature of an extinct giant sloth?

Modern sloths are curious beasts. Generally fairly small, tree-dwelling critters, they’re notorious for their slowness. But they come from a grand tradition of great size. Until the big extinction of large mammals that occurred about 10,000 years ago, there roamed across the land giant ground sloths that would have made most people run in terror.

Megatherium americanum

These giant sloths coexisted with great beasts like mammoths and woolly rhinos and saber-toothed tigers. They didn’t live in the trees; they were far too big. Instead, they moved about on the ground, using their huge claws to rake leaves from trees to eat.

All this is romantic, but seriously, if giant sloths were as slow as their modern cohorts, wouldn’t they have just been gobbled up by the saber-tooth tigers and the dire wolves?

Well, that’s a good question. How can it be answered?

Modern sloths are slow because they have low metabolic rates. Their diets consist of foods of poor nutritive value, so they balance this by sticking high in the trees and taking their time to get around. The low metabolic rate is reflected by having a low body temperature. Most mammals (like us, or horses and cattle) keep their bodies at 37-39°C. Modern sloths (and other low-metabolic-rate mammals) keep theirs at around 32°C.

So all we need to do is measure the body temperature of a giant sloth! Oh, wait. They’re extinct. Dang.

Geochemistry to the rescue!

Almost all of my research revolves around the geochemical analysis of fossilized teeth in mammals, to make inferences about their biology, and the environments in which they lived. To do this, I measure the relative amounts of stable isotopes (not the radioactive ones!) of carbon and oxygen from tooth enamel. The methods I use are (relatively) straightforward, and have been used actively for decades. The relative amounts of the different isotopes of oxygen and carbon can be related to temperature – and here’s our foot in the door to get at body temperature.

It can be complicated though, especially for oxygen, and until recently we couldn’t easily distinguish temperature changes from things like changes in the amount of precipitation. We also could only look at changes in environmental temperature, rather than body temperature.  (Sigh.)

That changed a few years back with the development of a new method of temperature determination called “clumped isotope” paleothermometry or just delta-47 (Δ47). As it happens, the heavy isotopes of carbon and oxygen can exist together (clump) in a single molecule of carbon dioxide, CO2 (which is what we measure with the mass spectrometer). This carbon dioxide comes from carbonate (CO3) which comes from the tooth enamel. How often the heavy carbon and heavy oxygen clump in a molecule is directly related to the temperature at which the molecule formed. In the case of mammals, this is the temperature of the mammal’s body.

So all we have to do is count how many carbon dioxide molecules have both the heavy carbon and the heavy oxygen (= clumped isotopes) and we can measure body temperature!

It sounds simple, it’s really not, but only because there aren’t that many molecules with the clumps, so we need a lot of material and tons of analytical time to get it done. This makes it expensive and it’s hard to get materials because you basically have to destroy most of a tooth. Museums don’t like to lend you specimens that you’re going to destroy. I don’t blame them, really.

We’ve been fortunate, however. One museum has recognized the importance of this study: We really do need to know the metabolic rates of giant sloths if we want to understand their biology and behavior. We were lent teeth from two species of giant sloth, as well as teeth from a horse and a bison from the same cave locality that the sloths came from. We know body temperature in horses and bison, so we can use those results for comparison.

We’re also lucky that the clumped isotope method is so new, that the few labs that are capable of running these analyses are eager to try different things. Right now, we’re not having to pay for the analyses, though we do plan to see if we can get funding to pay for more analyses later.

Cool! Let’s do it!

But wait. There’s another problem. You see, sloths don’t have tooth enamel.

We use enamel from fossil teeth because it’s really hard and resistant to alteration during the process of fossilization. If the material we want to measure the isotopes from has been altered, we may be measuring something besides the body temperature signal – and that could be anything!

Sloth teeth are made entirely of dentine (which we have in our teeth, too, underneath the enamel). Sloths have two layers of dentine, a harder outer layer equivalent to enamel and a softer inner layer like our dentine. We’ve decided to measure the clumped isotopes from both the inner and outer dentine layers (assuming that the outer one is less likely to be altered, because it is much harder). We’re also measuring the clumped isotopes from the enamel and dentine of the horse and bison. This is how we’re going to determine if there is any alteration of the dentine in the sloth. If the sloth outer dentine gives the same temperature as the dentine in horse and bison, we have to be suspicious that it represents some alteration value and not really body temperature (and then all this work is for naught!).

Where we are.

Well, the preliminary data are in. They weren’t what I expected, but I’m not a sloth expert, so I’ll wait for my colleagues to chime in.

In the meantime, it’s time to start writing an abstract on the subject for the Society of Vertebrate Paleontology Annual Meeting, which this year will be in Raleigh, North Carolina. I think it’s gonna be pretty exciting!!!

Published: Global Warming 55 Million Years Ago

This is the first installment of my attempt to convert a scientific paper (my own) into plain language that is accessible to everyone. Feel free to ask questions in the comments. I’ll respond there, or with additional blog posts.

Climate change at the Paleocene-Eocene boundary: New insights from mollusks and organic carbon in the Hanna Basin of Wyoming.

By Penny Higgins

Published in PalArch’s Journal of Vertebrate Palaeontology

v.9 n. 4, p. 1-20

Link to the complete technical version: PDF

INTRODUCTION

There is a lot of interest in climate change these days, especially global warming. Especially if that global warming can be blamed on increasing amounts of carbon dioxide in the atmosphere. The problem is that it’s hard to know if the trend toward warmer temperatures (at least the global average) is due to natural cycles of the Earth or due to increases in atmospheric carbon dioxide because of the burning of fossil fuels by us, or if there is even a relationship between increasing carbon dioxide and warming (maybe increases in both are coincidence, but not not due to some causal relationship).

This paper doesn’t make any arguments to support or refute any ideas about modern global warming. However, it is relevant because it explores a past episode of rapid global warming. This ancient event took place about 55 million years ago. Global average temperatures might have increased by as much as 10 degrees, and did so relatively rapidly (over about 10,000 years). It is suspected that this rapid warming was due to the release of massive amounts of carbon dioxide into the atmosphere.

So the warming of 55 million years ago seems similar to modern warming in being rapid (though not as rapid as in the modern scenario) and being potentially blamed on increased carbon dioxide in the atmosphere. In this paper, we assume that the warming at 55 million years ago did happen, lasted about 150 thousand years, then things cooled back down to more-or-less where they had been before. For the sake of this paper, it doesn’t matter what caused the warming, only that it was.

This warming event began at the boundary between two epochs on the geologic time scale: the Paleocene and the Eocene. We call this event the Paleocene-Eocene Thermal Maximum, or the PETM.

The Paleocene-Eocene boundary is actually defined based upon the onset of warming, as identified by a big change in the relative amounts of two isotopes of carbon (13-C and 12-C) in the atmosphere, and consequently in all organic material that was deposited at that time. How we measure these amounts and what the actual numbers mean are the topic of another paper or blog post. What’s important is that these relative amounts, or isotopic ratios, are presented in what we call the ‘delta notation’ (like δ13C, δ15N, and δ18O) in units of permil (‰). When delta values are more negative, there’s relatively more 12-C in a sample; when delta values are more positive; there’s more 13-C in a sample. The PETM, then, is recognized by a negative carbon isotope excursion (CIE), where the delta values suddenly drop by three to five permil. The PETM ends when carbon delta values go back to what they had been before the CIE started.

Much of what’s known about the climate change at the PETM, and the Earth’s subsequent recovery, is known from cores of rock and sediment collected from the ocean floors. Naturally, we’re interested in what would happen to us – those of us stuck on land. In the Hanna Basin, in south-central Wyoming, there is a sequence of rocks that began to be deposited before the PETM started, and continued to be deposited during the PETM and after the PETM. These rocks were deposited on land and are sediments from lakes and floodplains. In these lakes and small rivers were living lots of organisms, in particular, mussels. There was also a lot of organic material being deposited – so much so that now it is represented by many thick coal seams that are actively mined.

Location Map showing where the Hanna Formation lies

This sets up a scenario where we can use the organic carbon (from the coals) to identify the CIE, and therefore the Paleocene-Eocene boundary and the PETM in a terrestrial rock sequence. Then, we can look at the fossil mussels, and other things, to examine the environmental changes that happened during and after the PETM. The main questions, and ones that are relevant to modern concerns about climate change, are:

1) after the warming ended, did the environment go back to its original state or was it forever changed?

2) what effect did climate change have on the organisms that lived through it?

FINDING THE PETM

First, let’s look at the rocks. The Hanna Formation, the rock unit I’m studying, is about three kilometers thick (or about two miles). The part we care about is in the top half. The bulk of the Hanna Formation is composed of sediments deposited on floodplains, with little shallow streams that wound around (called fluvial). There are two parts of the Hanna Formation that have lake beds in them (called lacustrine), cleverly called the upper and lower lacustrine units (ULU and LLU). The focus of this study is on the upper and lower lacustrine units and some fluvial rocks in between them. I had reason to suspect, when I started this study that the Paleocene-Eocene boundary lies between the lacustrine units. This is borne out in this paper.

The Hanna Formation – its total thickness and where the study section is

It turns out that is wasn’t very easy to identify the CIE (and therefore the Paleocene-Eocene boundary) in the Hanna Formation. The delta values from the coals and other organic materials jump around a lot, probably because the organic carbon I was looking at comes from lots of different types of plants, all of which are slightly different isotopically. One conclusion of this study is that we need to do more ‘compound-specific’ work. That is to say, if we can isolate specific organic molecules and analyze them separately from everything else, that should make the carbon isotope values less variable. Unfortunately, the type of instrument and laboratory that’s needed to do that isn’t present here at the University of Rochester. I’m working on it.

Nevertheless, in general where the values are more negative than -26‰, you’re in the CIE. To help make it more clear, I used a three-point running average of the raw carbon isotope data. This tends to smooth out the line, while keeping the big jumps visible. The first major jump into more negative values occurs at about 2500 meters, which coincides with estimations made using mammal fossils and fossil mollusks by others who have worked in the Hanna Formation before.

When I compared this overall pattern with other published patterns of carbon isotope variability (some from ocean cores and some from terrestrial sections), things matched up pretty nicely. Using pattern matching, I placed the top of the CIE (and the end of the PETM) at about 2650 meters, which is in the lower part of the upper lacustrine unit. This means that the 150 thousand years of the PETM are represented by about 150 meters of rock in the Hanna Formation, or that a meter of rock was laid down every 100 thousand years. This is actually reasonable – no one in the geological sciences is bothered by this rate of deposition.

Carbon Isotopes from the Hanna Formation, showing the CIE and the location of the LLU and ULU

ENVIRONMENTAL CHANGE

Now that the CIE is identified, I could begin to address the environmental changes that might have occured during that period of warming. I approach this in two ways:

1) Looking at isotopes of nitrogen – which gives us information about the organisms from which the organic matter is coming (e.g. we can distinguish between a stagnant pond or a lively lake).

2) Looking at isotopes of carbon and oxygen in the mussels that have been collected – which can give us information about annual changes in the environment that the mussels lived in.

NITROGEN

Most of the organic molecules that go into coal also have nitrogen in them, though not as much nitrogen as carbon. Usually, when looking at fossil organic carbon, the amount of carbon is so low that there essentially is no measurable nitrogen in the samples. In the case of the Hanna Formation, though, we have coal, which is basically ALL organic carbon-bearing molecules. That means that there’s some hope of finding measurable nitrogen, and that’s what I did.

So really, this part of the study was basically done for giggles – just to see if I could do it. And once I had data, well, I had to interpret it.

There are two ways to think about nitrogen. One is to simply compare how much nitrogen there is relative to carbon (C/N ratios). A second is to look at the ratios of two isotopes of nitrogen, 14-N and 15-N. C/N ratios give us information about the origin of the organic molecules (from algae or land plants, for example) and the isotopic ratios tell us about status of lake, whether it be full of actively photosynthesizing plants or if it is stagnant.

Using the combination of C/N ratios and nitrogen isotopes, it seems that for the most part the organic carbon in the lakes of the Hanna Formation is dominated by land plants. So these are leaves and litter that were washed into the lakes. One interesting isotopic data point sits at the bottom of the CIE. From this point, it seems that there was might have been drying of the lake at the beginning of the PETM. That would make sense, assuming that warming could cause greater evaporation.

MUSSELS

The work with the mussels is actually been the topic of two undergraduate senior theses that I’ve advised. They’ve been doing some great work to look at the annual changes in isotopes by collecting multiple samples from single shells, following growth lines, to put together a picture of environmental changes that happened during the individual animals’ lives. I don’t say much about that work in this paper. That’ll be published later. What I do talk about is trends. I’ve taken the averages from individual shells and used those to look at how the isotopes of carbon and oxygen from the shells change over time. I also talk about how carbon and oxygen isotopes change relative to each other within a single shell.

Mussel Shell – dashed lines show where isotopic samples were collected

So, how are carbon and oxygen in the shells of mussels, you ask? Mollusk shells are made of calcium carbonate (CaCO3) which contains one carbon and three oxygen atoms. We collect powdered bits of the shells by using a dental drill and take this powder and put it into the mass spectrometer. The calcium carbonate is converted to carbon dioxide (which is easily measured by the mass spectrometer) by reacting the powders with acid. You put acid on the calcium carbonate, it fizzes, making carbon dioxide, which is drawn into the mass spectrometer and – wango! – we have carbon and oxygen data.

Carbon in mussel shells is thought to be derived mostly from carbon dioxide that has been dissolved in the water, and so should track the isotopic value of atmospheric carbon dioxide. Atmospheric carbon dioxide, as mentioned earlier, gets more negative during the CIE then returns to the pre-CIE values. The average values from the shells seem to follow this trend, so there’s no surprises.

But now we’re talking about yet another isotope: Oxygen. The isotopes that we measure are 16-O and 18-O. Isotopes of oxygen are a big topic of discussion when dealing with climate change. That’s because oxygen is an important component of water, and water is an important component of climates. For example, climates can be described as arid or humid. There can be rainy seasons or monsoons. Precipitation can take the form of rain or snow. All of these processes affect the isotopes of oxygen in water. Temperature also affect oxygen isotopes. Unfortunately, isotopes of oxygen in water are a very complex system, and would best be discussed in a separate blog post. What is important is that there isn’t any obvious trend in the average values of oxygen from the shells over time, either.

Since oxygen is affected by climate, one would expect that there should be some change if there’s been a significant climate change. However, because oxygen is so complicated, the changes in oxygen isotopes by changing one part of climate (the time of year when it rains, for example), might be offset by other changes (like a change in average temperature). The fact that there isn’t any obvious trend or change in oxygen isotopes over time doesn’t mean that there wasn’t any change in climate.

And we do see a difference when we compare the variations in carbon and oxygen within a single shell. Carbon and oxygen in shells from the lower lacustrine unit (before the PETM) tend to change in opposite directions (or are negatively correlated). When oxygen isotopic values get more positive, carbon isotopic values get more negative. Shells in the upper lacustrine unit show the opposite pattern. Carbon and oxygen values change in the same direction (are positively correlated), so when oxygen gets more positive, so does carbon. From this, it’s possible to infer that before the PETM there was a lot of vegetation and photosynthesis going on around the lakes, whereas during the PETM, photosynthesis might have slowed down during the warmer months and bacteria might have dominated life in the water. This seems reasonable since in the upper lacustrine unit there are also huge fossilized bacterial mats called stromatolites.

CONCLUSION

So that’s what this paper is about. We see some evidence of environmental change due to warming at the Paleocene-Eocene boundary. Particularly, we have the one really positive nitrogen isotopic value near the base of the CIE and we see a change in the relationships between carbon and oxygen isotopes in individual mussel shells during the PETM as compared to pre-PETM.

One thing that hopefully is obvious however: there is more work to be done.

The work with nitrogen isotopes started with a shot in the dark. More samples should be analyzed. There’s definitely more work to be done there.

My students’ work on the mussel shells will greatly contribute to this as well. Since I wrote this paper, there have been more shells collected and more samples analyzed. That work needs to be wrapped up and published soon.

We really need to do that ‘compound-specific’ work I mentioned earlier to help clarify the CIE. It’ll also help clear up what sorts of plants were around at that time, so we can better interpret the nitrogen data.

Also, though not discussed at all in the paper, is the fact that there are paleobotanists out there looking at fossil leaves and pollen. There’s a story to be told there, and someone’s getting a Ph.D. For their efforts. I can’t wait until that work is done!

The Snouters and Teaching Cladistics

A new species of Rhinograde mammal, Nasoperforator bouffoni, was described last week by a group of researchers at the Muséum d’histoire naturelle, in Paris. This is really exiting news in science, as we often (falsely) think that we’ve found and named all the living mammals that there are.

Drawing of the head of Nasoperforator bouffoni

The Rhinogrades (or more affectionately, the Snouters) were originally described in the book, The Snouters: Form and Life of the Rhinogrades, by Harald Stümpke. The Rhinogrades are a new order of mammals known only from the island Hy-dud-dye-fee in the South Sea archipelago of Hi-yi-yi. They are noted for the incredible adaptations of their noses for locomotion and feeding.

Illustration of Otopteryx volitans

Stümpke proposes a family tree of the Order Rhinogradentia based upon 26 genera of Snouters described in the book. This sort of family tree, more properly called a ‘phylogram,’ is typically based upon a person’s gut feeling about the similarities among different species. It can be based upon a researcher’s experience and can be biased by a scientist’s pre-conceived notions about how things ought to be related. A better, more objective, way to approach relationships among different species is to use cladistic analysis (or cladistics).

Stümpke's phylogram of the Snouters

If you’re remotely interested in paleontology, then you’ve probably heard of cladistics (or cladograms, or clades). Cladistics is one of those things in the science of paleontology that you have to know about. Some folks spend their entire careers focused on cladistic analysis. Others avoid cladistics vehemently. Nevertheless, there’s no escaping cladistics. If you want to know paleontology, you gotta know cladistics.

So then, what is cladistics if it’s so important? For me, it’s a topic that I took a full semester course on as a graduate student. My notes are in a binder labeled ‘sadistics,’ which goes a long way to describe just how I feel about cladistics. (I actually have two binders labeled ‘sadistics.’ The other one is for a class in which I learned about t-tests, f-tests, means, and standard deviations.)

But seriously, cladistics is a tool by which paleontologists (and biologists and botanists and geneticists) can mathematically determine the ‘relatedness’ of organisms. More generally, cladistics is used to determine evolutionary relationships, so we can determine who evolved from whom. It’s mathematical, and thus reproducible and computerizable, and comes replete with all sorts of statistics (the other sadistics) that can be used to support or refute proposed evolutionary pathways.

Fine.

But it’s also a bit of a nightmare.

The analysis starts by breaking a species down into a bunch of ‘characters’ for which there are, in the purest cladistics, only two states. The states for each character are entered as 0’s and 1’s in a matrix. Examples of well-behaved characters are:

Character Character state ‘0’ Character state ‘1’
Antorbital Fenestra (a skull opening seen in some dinosaurs) Absent Present
Palatine teeth (having teeth on the roof of the mouth) Present Absent

Presence and absence characters are great. Unfortunately, not all characters can be broken easily into 0’s and 1’s.

Character Character state ‘0’ Character state ‘1’ Character state ‘2’
Eye color Blue Brown Hazel
Femur length (the thigh bone) 0-10 inches 12-18 inches 20-19 inches

And sometimes, characters obvious in several species are not known from others. For example, eye color is meaningless when considering eye-less animals, but if only one species in your analysis lacks eyes, then you need that character information for the other species. Another problem occurs when (especially in paleontology) an organism is only incompletely known. For example, toe characteristics aren’t helpful when one of the animals in your study is known only from its skull.

In principle, however, one needs only determine all the character states for a suite of characters for each organism in an analysis.

Organism Character 1 (hooves) Character 2 (hair) Character 3 (warm-blooded) Character 4 (bones) Character 5 (scales) Character 6 (4-chambered heart)
Horse 1 (has) 1 (has) 1 (has) 1 (has) 0 (doesn’t have) 1 (has)
Cow 1 (has) 1 (has) 1 (has) 1 (has) 0 (doesn’t have) 1 (has)
Trout 0 (doesn’t have) 0 (doesn’t have) 0 (doesn’t have) 1 (has) 1 (has) 0 (doesn’t have)
Croco-stimpy 0 (doesn’t have) 0 (doesn’t have) 0 (doesn’t have) 1 (has) 1 (has) 1 (has)

And then you use all the 1’s and 0’s to determine who’s most similar to (and thus more related to) whom. In the above case, if we look only at characters 1-5, one can see that horses and cows are very similar and related to each other, as are trout and croco-stimpies. But add character 6, and you can see that croco-stimpies are more similar to horses and cows than to trout, thus, one could infer that trout evolved into croco-stimpies which then evolved into horses and cows.

You’ve already got a headache, and it hasn’t even gotten complicated yet.

Enter the Rhinogrades.

For years, I’ve been handing my students copies of Stümpke’s book, and asking them to do a cladistic analysis of nine species (of their choice) of Snouters. Next time I’ll have them include the new species. The problem is that the students have to come up with their own characters and character states. Students quickly realize how important it is to choose good characters (and character states), and how difficult it can be to determine character states when all they have is an incomplete description of an organism. So, it’s actually a really great exercise (even if the students claim to hate it). The students turn in a cladogram and a list of characters and character states, and I compare their cladogram with the one I’ve devised based off of Stümpke’s family tree.

My Snouter cladogram - based only on Stümpke's phylogram

And when they’re all done, then I tell them.

It’s a hoax. There’s no Hi-Yi-Yi. No Nasoperforator. But it was fun, wasn’t it?

And now for something completely different…

This recent post reminds me that I ought to be using this blog for good, not just for shameless self-promotion (although self-promotion can be fun). I need to promote science, its importance and utility. And, of course, how fun it is!

So I think I’ll start adding blog entries about my current research, what it is, and why it matters. Anyone interested?

Current projects include:

  • Body temperature in giant ground sloths. (You can do that?)
  • Paleobiology and dietary preferences of giant (1000 kg) rodents in South America. (Yes, Rodents of Unusual Size do exist!)
  • Tooth mineralization patterns and their relationship to diet in notoungulates (extinct endemic mammals from South America).
  • Continental environmental change associated with rapid global warming at the Paleocene-Eocene boundary (55 million years ago).
  • Late Cretaceous vertebrates from Axel Heiberg Island. (yeah, in the Arctic)
  • Less-is-more: Using bulk isotopic analysis from tooth enamel of fossil mammals to predict yearly patterns of temperature and precipitation.
  • Mid-Paleocene mammals and reptiles, and species turnover due to climate change 60-ish million years ago
  • Cheek tooth (molar) mineralization patterns in mammoths. (Everyone uses tusks! <eyes rolling>)

If you’re interested in any of these things, let me know, and I’ll write about them. I can also write about day-to-day life as an non-tenure-track isotope geochemist, in a rigorous research-heavy earth-sciences department.

Let me know!