These sharks just keep getting pregnant!

27 06 2007

Because of my public school education, I have been trained to immediately think of the New Mexico Whiptail lizard (Cnemidophorus neomexicanus) whenever I hear the word “parthenogenesis.” What exactly parthenogenesis was or how it occurred was never covered, but the association between reproduction without a male and these lizards was certainly hammered in to my brain. Lately, however, there have been various cases of other animals exhibiting parthenogenic reproduction, including Komodo Dragons (Varanus komodoensis) and Bonnethead Sharks (Sphyrna tiburo).

The latest news deals with a Blacktip Reef Shark (Carcharhinus melanopterus) that had died after a physical had gone awry, the shark (named “Tidbit”) biting one of the aquarium staff before dying shortly thereafter. Upon autopsy, veterinarian Bob George discovered a near-term baby shark inside Tidbit, making this perhaps the second known case of shark parthenogenesis known. Tests still need to be done to confirm this, but Tidbit was not kept with any males of her species and sharks are not known to hybridize, so it is fairly certain that this is another case of parthenogenesis (it should also be noted that both bonnetheads and blacktip reef sharks belong to Order Charcharhiniformes, or the “Ground Sharks”).

In the case of the bonnethead shark, the parthenogenic offspring was female, and the CNN article linked above makes no mention of the sex of the offspring found in Tidbit (whatever I guessed, I’d have a 50/50 chance at being right). It is possible that in times of sexual isolation some sharks can produce offspring on their own, but if no males show up (or no males are produced through parthenogenesis, as komodo dragons apparently can achieve), then the population is no better off. I would also be interested to see if this particular ability exists across all shark groups or just in this particular order; are the “warm-bodied” lamniform sharks like Makos, Porbeagles, and Great White Sharks capable of this as well? Is this ability something new that evolved in this one group, or is it an ancestral condition that more derived sharks have lost? For now we’ll have to await Tidbit’s test results, but if nothing else aquarium curators should be keeping their eyes open for more instances of parthenogenesis going on right under their noses.

More books?!

27 06 2007

As if I didn’t have enough to read already, I’ve added a few more books to my planned reading for the summer. I finished Lilian McLaughlin Brown’s Bring ’em Back Petrified last night, so I’ll hopefully be able to jump right into whatever arrives in the mail today when I get home from work. Anyway, here’s what’s been added;

The Tempo and Mode of Evolution by George Gaylord Simpson (1984 paperback)

I’ve been meaning to read this book for quite some some, but until now I had been unable to find an affordable copy. I certainly can’t wait to dig into it.

How Animals Work by Knut Schmidt-Nielsen

I know a bit about skeletal anatomy, but I have to admit that my understanding of physiology and biomechanics is pretty poor. I’m hoping Schmidt-Nielsen’s book will help to fix that.

Walker’s Mammals of the World (2 Volumes) by Ronald M. Nowak

I first happened across Walker’s Mammals of the World while petsitting for the late Dr. Ted Stiles, and I knew that my library would be pretty poor without a copy. While I plan on accumulating other books detailing mammals of the Neotropics and Africa, it will be great to have a set of books that I can use to further the number of taxa I’m familiar with.

Historical Geology: Evolution of Earth and Life Through Time by Reed Wicander and James S. Monroe

In the fall of last year I took a course called Evolution in Geologic Time, and while I’m pretty familiar with big-time evolutionary events, I could do a lot better remembering exactly when they happened. Likewise, my understanding of evolution is focused primarily around tetrapods, the majority of earth’s history prior to the Cambrian still a bit foggy upon recall, so I definitely want to help my understanding of what happened in “Deep Time” a bit more.

God’s Own Scientists: Creationists in a Secular World by Christopher P. Toumey

I haven’t yet read Ronald Numbers’ The Creationists, but I saw this book mentioned on a comment thread over at Respectful Insolence and it sounded very interesting. I’ve become relatively well-familiar with changes and shifts in creationist thought over the past few hundred years, but I definitely want to get a better idea of what goes on behind closed doors when “creation scientists” get together.

The Theory of Island Biogeography by Robert H. MacArthur and Edward O. Wilson

After a tip from Bora that Quammen’s Song of the Dodo has a fair number of mistakes, I thought I would pick up what is considered to be the landmark work in the field of biogeography. I plan to read the two books in succession and write up a post on the subject, but that’s probably a few weeks (if not a month) away.

The way I go through books, a few more will likely be added before all is said and done, but for now I think I’ve got my work cut out for me.

Walking With Triceratops

26 06 2007

It’s funny how certain things come into style, only to be swept away by a new trend. Clothes, music, and television all are mediums in which the bang-and-bust cycle of trends is apparent, but things can come “back into style” in paleontology as well. Not very long ago I read Robert Bakker’s The Dinosaur Heresies, a wonderful book that certainly shook things up. Not everything within its pages is valid, but Bakker certainly did a lot of heavy-lifting in order to show that dinosaurs were not glorified lizards. One of the points he makes involves the posture of one of the most beloved dinosaurs, Triceratops, but as I have learned the problem of Triceratops posture is a bit more complicated than I had originally thought.

Triceratops Sprawling
From “Mounted Skeleton of Triceratops elatus” by Henry Fairfield Osborn, American Museum Novitiates, Sept. 6, 1933

On the fourth floor of the American Museum of Natural History, the mounted skeleton of Triceratops horridus (the same mount referred to as T. elatus by Osborn, above) stands today in the same posture as it was mounted in the 1930’s; back legs directly under the hips like a good dinosaur, but with the front limbs sprawled out to the sides, almost resembling a body-builder who bulked up his arms but neglected his legs. In fact, this analogy is not very far off from what Osborn himself envisioned, writing;

The pose of the fore limb, set out widely apart from the body, is also designed to withstand attack, like the widely spreading feet of the pugilist or wrestler.

This is Osborn’s idea of the adaptive value for the stance, but it does not explain why his Triceratops is sticking out its upper arms nearly horizontal to the body. The problem in determining a proper mount for the composite skeleton (fossil material coming from 4 skeletons) was that the front limbs would not articulate in the way a mammals forelimbs do. After observing various reptiles and mammals, as well as trying different poses, it became apparent that Triceratops could not carry its forelimbs directly under the body without disarticulating its own skeleton; the sprawling pose was the only one that seemed to work. I’m sure the appearance of Triceratops as being front-heavy played into the pose as well, such a massive head requiring plenty of support from the arms, although in the position chosen a huge amount of strain would be put on the front limbs. It’s arms would be spread out away from the body in a push-up position, with the legs directly under the body; if this dinosaur walked in such a position it would be a very amusing sight.

Then I read Bakker, who argued that fossil trackways (in addition to his own research and position that dinosaurs were active, dynamic animals) showed that Triceratops did, in fact, carry its front legs underneath its body and was even capable of galloping. How fast this dinosaur may have been is something for another day (I’m not even aware of any studies that have attempted to answer that question, in fact), but Bakker seemed very confident in his idea of posture, and I had my own misgivings about the super-sprawl of the AMNH mount. The trick is, however, remebering that this is not an either or question where the super-sprawl or “good dinosaur” pose must be right to the exclusion of all others. In truth, the real answer seems to lie somewhere in between.

In the 1933 paper, Osborn mentions the analysis of W.D. Matthew, tells us that other scientists were mounting their ceratopsians in different ways;

The heavy strain of supporting the great body on these widely-spread fore limbs is very apparent but there seems to be no other way to pose the skeleton. A compromise pose, such as that of the National Museum mounted skeleton (or of Marsh’s restorations so far as they can be interpreted) serves to reduce, not to banish the anatomically impossible disjointing.

Triceratops Profile
From “Mounted Skeleton of Triceratops elatus” by Henry Fairfield Osborn, American Museum Novitiates, Sept. 6, 1933

With such problematic limbs, different mounts were bound to take different poses, and the Smithsonian dinosaur is of further interest to us because it recent has helped to answer the very questions we’re asking. In May of 2001, the Smithsonian unveiled its new mount for Triceratops (dubbed “Hatcher” after the man who discovered it), featuring limbs that were closer to being under the body than Osborn’s dinosaur, but still bend slightly outward from the body. The reanalysis that led to this new pose was undertaken by Ralph Chapman, who used computer modeling to help properly restore the dinosaur (i.e. it, too was a composite, and its back feet were actually from a hadrosaur) and figure out how it might have moved. Not everyone is behind the semi-sprawl, however, and just prior to the Smithsonian skeleton being unveiled Gregory S. Paul and Per Christiansen issued the paper “Forelimb posture in neoceratopsian dinosaurs: implications for gait and locomotion” in the journal Paleobiology, arguing that the problem with Triceratops posture often stems from problems articulating other parts of the skeleton; if you get the vertebrae and ribs wrong, you’ll probably get the arms wrong, too.

So what about trackways? If we have the ichnofossils, then we should be able to tell what the limb posture of this animal was, right? This seems to be a lot to ask; both in Bakker’s book and the Louie Psihoyos’ book Hunting Dinosaurs (the only two books with depictions of Triceratops tracks I’ve come across) the trackways are illustrated. In Bakker’s book, the tracks align just the way he says they should; the tracks suggesting the feet were under the body. Psihoyos’ book, however, depicts tracks made by the front limbs being just slightly outside those made by the rear limbs, suggesting a semi-sprawl. If that was not enough, fossil trackways are notoriously hard to match up with known fossils, tracks of the same type receiving their own name (like Grallator here in New Jersey) when we can’t figure out what dinosaur made them. This isn’t to say that we can’t identify any tracks or even any tracks made by ceratopsian dinosaurs, but given how massive the heads of ceratopsian dinosaurs could be, it’s important information to know when determining posture that trackways don’t tell us much about.

And so the arguments will likely continue; while we now know that Triceratops and its relatives like Torosaurus did not hold their front limbs out to the point where their chests would be scraping the ground while their butts were in the air, the way their skeletons are constructed seems to suggest a small amount of sprawl in the front limbs. Carrying such a massive skull would have certainly affected the front limbs, and if the Triceratops carried its limbs directly under its body it may have been a little more unstable/more likely to tip over. I don’t know if it has been done, but I for one would love to see what happens to the animal’s center of gravity when switched between the various postures, and I think that the semi-sprawl would have offered Triceratops more support without putting undue strain on its limbs.

It’s funny how old ideas come back; in such a short amount of time, Triceratops was thought to have its arms out to the side, then under its body, and now we’re at a point of compromise. While the logic of uniformitarianism may be “the present is the key to the past,” the history of the science of paleontology has taught me that the past is the key to the present, and old “fossils” can still tell us a lot about debates that continue today.

Not quite Big Bird

26 06 2007

If you can’t wait for my analysis of the PNAS article (slated for the June 29th issue) about the giant Peruvian penguins Icadyptes salasi and the smaller Perudyptes devriesi, here’s a list of articles covering the story. While the new finds certainly have implications for the evolution of penguins, everyone is acting especially surprised that these birds lived in an area much warmer than the Antarctic, but I guess they’ve never heard of the Galapagos Penguin (Spheniscus mendiculus) or even the African (“Jackass”) Penguin (Spheniscus demersus). This reminds me that I need to pick up G.G. Simpson’s book Penguins: Past and Present, Here and There, but I’ve got lots of books to get through before I start ordering anything new. Anyway, here is the abstract and the entries relevant to the big birds;

Julia A. Clarke, Daniel T. Ksepka, Marcelo Stucchi, Mario Urbina, Norberto Giannini, Sara Bertelli, Yanina Narváez, and Clint A. Boyd (2007). “Paleogene equatorial penguins challenge the proposed relationship between penguin biogeography, body size evolution, and Cenozoic climate change.” Proceedings of the National Academy of Sciences (PNAS) June 29, 2007.

New penguin fossils from the Eocene of Peru force a reevaluation of previous hypotheses regarding the causal role of climate change in penguin evolution. Repeatedly, it was proposed that penguins originated in high southern latitudes and arrived at equatorial regions relatively recently (e.g., 4 to 8 million years ago), only well after the onset of latest Eocene/Oligocene global cooling and increases in polar ice volume. By contrast, new discoveries from the middle and late Eocene of Peru reveal that penguins invaded low latitudes over 30 million years earlier than prior data supported, during one of the warmest intervals of the Cenozoic. A diverse fauna includes two new species, here reported from two of the best exemplars of Paleogene penguins yet recovered. The most comprehensive phylogenetic analysis of Sphenisciformes to date, combining morphological and molecular data, places the new species outside the extant penguin radiation (crown clade: Spheniscidae) and supports two separate dispersals to equatorial (paleolatitude ~14� S) regions during greenhouse Earth conditions. One new species is among the deepest divergences within Sphenisciformes. The second is the most complete giant (>1.5m standing height) penguin yet described. Both species provide critical information on early penguin cranial osteology, trends in penguin body size, and the evolution of the penguin flipper.

LiveScience – Giant Ancient Penguins Liked it Hot – Prehistoric equatorial penguins reached 5 feet in height
BBC News – Tropical giant penguin discovered – Past global warming produced monster penguins
The Guardian – Pick up a penguin? Not this one you wouldn’t
EurekAlert! – March of the giant penguins
San Francisco Chronicle – Rethinking penguins — big, warm-weather fossil


26 06 2007

AiG just can’t stop crowing about its new creation funhouse, although bloggers who have been here recently (check out Jason Rosenhouse’s reviews here, here, and here [with more on the way!]) have made it clear that it’s long on special effects and short on substance. Although I haven’t been there myself, from what I have seen and heard so far I think Jason is 100% correct when he writes;

None of the displays and exhibits present anything that you can’t also find in any of a dozen different creationist books. With a real natural history museum you might say, “It is one thing to read about evolution in books. It is quite another to be able to see the fossils for yourself.” But with the creation museum there is really no distinction between the creationist literature and what the museum presents. You can read the propaganda in book form, or you can walk through the museum and read the same material presented on colorful placards.

This hasn’t stopped AiG from putting out positive reviews of the museum nearly every day, and in the latest review posted to their website, a curious error is made. Guest-writer David MacMillan III says;

In comparison with the Creation Museum, “world-class” museums—even museums like the Roosevelt Museum of Natural History in New York City or the Smithsonian Museum of Natural History in Washington, D.C.—seem paltry and commonplace. [emphasis mine]

Teddy has a bit of presence outside the museum and around the entrances of the AMNH (the Theodore Roosevelt Rotunda featuring quotes and depictions of the past president, as well as the famous Barosaurus vs. Allosaurus mount), so I wonder why the author of the article slipped up. Here’s a photo of myself outside the museum almost 3 years ago;


I guess it just goes to show how carefully researched and edited AiG’s articles are.

Tuesday Morning Notes

26 06 2007

My sunburn has finally started to become less painful, my shoulders still being the worst of it, but right now I look as if I should be up in a bell tower crying “Sanctuary! Sanctuary!” as my nose and cheeks continue to peel.

I blasted through the rest of The Beak of the Finch last night and it certainly was an enjoyable read. The author’s diversion in the 3rd quarter of the book to describe other observed accounts of “evolution in action” could have been integrated into the work a little better, but overall I found it to be enjoyable and enlightening. In fact, as I was reading I was reminded of some earlier ideas I had about global warming and its effect on ecology, but it seemed like at every turn the Grants or the author had beat me to the punch over a decade ago. The book did make me realize, however, how much I have some to dislike the terms “Darwinist” and “evolutionist.” I’ve discussed my dislike of the term “Darwinist” before, but even though I myself have used the term “evolutionist” it still leaves a bad taste in my mouth, smacking of the religious. We don’t go out of our way to say that someone “believes in” gravity or photosynthesis, so I don’t see why we should continue going out of our way to say “evolutionist.”

I also received Lilian MacLaughlin Brown’s Bring ’em Back Petrified yesterday, wrapped up like a Christmas present and with a $2 bill inside (the book was not in as good condition as advertised). You don’t get that kind of service from your local chain book-store. Anyway, the book seems to chronicle the time Barnum Brown and his wife visited Guatemala, looking for Cenozoic fossils. It is interesting to read the book from the perspective of Brown’s wife, Brown seemingly driven to get out and find fossils as soon as possible, his wife preferring to be a housewife, even in the middle of the jungle. What is also curious is that the book contains a number of drawings, some seemingly drawn from photographs, but the faces of the couple are always blacked out (a photo of Barnum Brown is under “Currently Reading” on the right since there seems to be no image of the book’s cover anywhere). I managed to get 50 pages into it last night, and I’ll likely finish it this afternoon before devouring whatever comes in the mail today.

I also would love to write something up about the giant, extinct Peruvian penguins announced yesterday, but the PNAS website does not seem to have any paper about the giant birds. I could write up the story quite quickly like a number of other blogs and news outlets already have, but I would prefer to read the actual paper first, so I guess I’ll have to wait. I still have plenty of posts to work on, though, and perhaps I’ll write something up about a paper focusing on extinction and geographical distribution I came across yesterday in the meantime…

Not worth the paper it’s printed on…

25 06 2007

If you’re a teacher/educator and will be attending the upcoming National Education Association conference (I assume it’s the summer one in Philadelphia), you might want to keep an eye out for an AiG-sposored booth handing out tracts and copies of the error-laden book Evolution Exposed. While AiG swears up and down that they don’t want creationism taught in public schools (it’s all about “individual enlightenment,” or so Ken Ham and others would have us believe), they seem to be trying awfully hard to get teachers and school administrators to realize how terrible evolution is. They don’t want to get creationism into public schools, no sir; they just want to convert educators, parents, and school boards so that they can, well, get creationism into public schools…

Update the 1st; PZ has caught on to this as well, providing a link to the creationists trying to evangelize to the attendees of the convention. Funny, the blogger I contacted said that AiG had next-to-nothing to do with the booth, and yet the booth has it’s own AiG-run blog, propaganda, etc.

Envelope please…

25 06 2007

I am exceedingly pleased to announce that Darren of Tetrapod Zoology has seen it fit to bestow the “Thinking Blogger Award” upon me (look in the right sidebar). I’m certainly glad to have been tagged by a blogger of superior knowledge/skill, and in-keeping with tradition I must now tag 5 other bloggers. This is a task in and of itself, however, as 1) So many other blogs get the ol’ gears turning in my noggin’, and 2) everyone and their mother seems to have one already. If I link to you and you’ve already been awarded, just let me know and I’ll pick someone else. Here are my picks for the award;

1) Jeremy Bruno – The Voltage Gate

Jeremy always has something interesting up on his blog, be it great quotes, new studies, or just-plain-cool videos. The Voltage Gate is certainly a must-read blog, and I am also duly indebted to Jeremy since he’s half the team that got the blog carnival Oekologie started.

2) Various – Shifting Baselines

Before I got serious about ecology, evolution, and paleontology, I was a shark nut and loved absolutely everything about the ocean. In fact, I still do despite my new interests eclipsing the old, and the crew at Shifting Baselines has definitely made me think about what we’re taking out of and putting into the oceans. Regardless of whether you’re interested in fish on your plate or in the ocean, Shifting Baselines is certainly thought-provoking.

3) Molly – RedMolly Picayune Democrat

While the vast majority of blogs I read are almost exclusively about science, there are plenty of excellent and thought-provoking writers out there covering different subject, and Molly’s blog is one of the best. Whether it’s about home schooling, the difference between local/organic food and the stuff at Shop Rite, or writing in general, Molly certainly has plenty of great insights.

4) Anne-Marie – Pondering Pikaia

Anne-Marie covers many of the same topics as I do on her relatively-new blog, but she has some wonderful insights and perspectives that I don’t always pick up on. Indeed, whenever I come across a widely-discussed story, I often say “I wonder what Anne-Marie thinks of this” and head on over to her blog. Hers is definitely a blog to watch.

5) Kate – Secret Sex Lives of Animals

We all know that if you don’t reproduce, you’re pretty much a dead-end (at least in evolutionary terms), but the importance of sex to behavior and evolution is often overlooked. Kate’s blog focuses on the mating habits of animals, and believe me, it’s not all “When a boy bear and a girl bear feel a certain way about each other…”

And there you have it. I would love to have tagged plenty of others, and there are plenty of other blogs that are worth a look, but alas, 5 is the number of the awards, and the number of awards shall be 5. If you want to go back to the post that started it all, you can track the history of the meme here.

Blog Against Theocracy, Part Deux

25 06 2007

Blue Gal has announced that the Blog Against Theocracy blogswarm will be back from July 1-4 with the theme “Separation of church and state is patriotic.” You can get all the details at the main page here.

I feel like the “Incredible Melting Man”…

25 06 2007

Sometimes I do stupid things despite the fact that I know better, and my stubbornness has been manifested in the form of a extremely painful sunburn all over my torso. Up until the year before last, I don’t remember ever experiencing sun burn at all, spending all day at the beach with only (at most) a little redness that never led to pain or peeling later on. This weekend was a different story, however, and after about 3 hours at the beach (1/2 of that time spent in the water) I have a burn that keeps me up a night and makes it painful to sit down or put on a shirt. I had a similar experience at Inversand a few weeks ago, and even though most of my body was covered up and therefore unaffected, I got a bad burn on the back of my ears from looking down at the marl all day.

While I was certainly stupid not to wear sun-screen (my wife and I forgot to bring some and didn’t feel like running out to buy some overpriced stuff from a shop in Spring Lake), I almost have to wonder if my more recent bad experiences with sun burns and the large number of skin cancer cases every year has something to do with the atmosphere. I know CFC’s were phased out during the 90’s, but that doesn’t mean that their effects stopped or even that the ones already released would not continue to deplete ozone in the atmosphere. In any case, I’m already starting to peel, giving me the appearance of so many of the anoles I kept in terrariums as a child, and hopefully things will only get better from here. Still, I should learn my lesson and go out of my way to wear protection from the sun, especially because last year my wife (then my fiancee) noticed a weird mole on my back that had never been there before. I cut it off myself and have not had any problems since, but I would be a fool if I invited skin cancer because I was too lazy to do anything about it.

This reminds me of a comment someone made to me this past weekend, too; they claimed that I was “speaking out both sides of my mouth” when it came to ecological preservation because I said man is feeble also but wields great destructive power. To this person it was an either-or question, but even a little thought decimates this logic. The most feeble person capable of pushing a button to launch a rocket or pull the trigger of a gun can unleash great destructive power, even though they may be fragile themselves. I am still amazed that humans exist at all, given that (as some like cartoonist Gary Larson have suggested) Homo sapiens is the walking equivalent of spam, as well as the fact that without technology we would be limited in our range of habitation and probably live short, brutal lives. We can decode the genome, level mountains, and create great works of art, but we can easily succumb from a fall down a few stairs, a spider bite, or allergy to peanut butter, and I do not see individuals of our species as any more durable or resilient than any other. There are always threats and dangers to life; we’re just better at getting around them or avoiding them than most other animals (although we have certainly created plenty of new dangers, and we continue to do so at our own peril).