Paleobiology, the best excuse to have a broad focus

Ok, to start I would like to present something that I see as a fundamental aspect of the profession of being a paleontologist - the opportunity to delve into many aspects of science, in a word, being a polymath. I am no polymath, and I don't think that most people that would claim to be should be doing so, but it is unavoidable and irresistible to learn and practice the various disciplines of science when one is a paleontologist.

Although most of us would say that isn't so, perhaps after years of focus describing the same group(s) of fossil animals, there are many fields of science one has to be familiar with to gain any competency in that. Among the skills needed, one must be a an anatomist, geologist, evolutionary biologist, and often practice many other skills such as spelunking, camping (and its various skills of its own), illustration (long gone are the days in which most professionals have illustrators that work for them full time), microscopy, and statistics.

But paleontology isn't restrained to those disciplines either. I recall telling my father many years ago, when he asked, "Are you sure you want to be a paleontologist?", that I commented that in a way, because paleontology is simply the record of the history of life, that it is justifiable to use all means and methods at better understanding that history. If something deemed it necessary for one to understand physiology or chemistry or contact mechanics to figure out how something an ancient organism was like, one could and should. Obviously we cannot all do everything, and for efficiency's sake, we need to collaborate with other specialists when those needs arise. But if there are topics outside the mainstream of classic paleontological methods, such as finding fossils, comparative anatomy, and systematics, the opportunity to subspecialize is there.

Most museum curators do not, and probaly should not, distract themselves from the business of "normal" paleontology, but there are many, many more positions for paleontologists in other fields in academia in which this sort of uniqueness may prove an advantage.

So why would I post this on a blog about Aquatic Amniotes? Well, if there is one "group" of vertebrates that is optimal for exploring paleobiological methods and questions, it is the aquatic amniotes. They are NOT a phylogenetic grouping, but a grouping unified by common physiological, mechanical, and anatomical problems of being in an aqueous environment. Though they appear to often find solutions to these problems that appear convergent, often they are not. In these cases, they provide an excellent opportunity to explore functional morphology, adaptation, and evolutionary developmental biology.

I hope to follow this post up with some fun examples of how a variety of scientific disciplines can be utilized to understand aquatic amniote evolution. I'll try to bring in some work by others on such fields as geochemistry, modeling, materials science, and pathology to illustrate how diverse the fields being used to study aquatic amniotes are. I hope that at least some of the students that may read this will find it encourages them to broaden their horizons, explore other methods and topics, to make them better paleontologists for the future.

Hippos prancing about underwater (Hippo-Ecomorph Rant #1)

The origin of most marine mammals invokes some imaginary semiaquatic transitional form. In the last decade, many of these transitional forms have actually been found, including the semiaquatic sirenian, Pezosiren portelli, which I had the honor of collecting with my master's advisor, Daryl Domning, in Jamaica at the end of my undergraduate studies and beginning of my MS in Anatomy at Howard University. Likewise, in 2001 two papers were published in the same week that described fossil ankle bones of whales that conclusively linked the origins of the Cetacea to the Artiodactyla. I remember that day, I think it was Sept 21, 2001, a Friday, because I was interviewing at Johns Hopkins that day. Shawn Zack (now at Marshall) picked me up at the train station and asked me if I had seen the paper by Thewissen and colleagues published on Thursday, and then said that there was another paper published that Friday by Gingerich and colleagues. Since then, the molecular phylogenetic assertions that hippos are the most closely related modern mammal to the Cetacea has gained much more backing, evn though these original papers in 2001 never inform us of what fossil group they are more closely aligned to. Some recent finds in Pakistan by Thewissen and colleagues have claimed an ancestor in an unusual group of terrestrial mammals known as raoellids, though further analysis by Geisler & Theodor calls some questions to exactly which fossil groups are related to cetaceans and which are not. Yet despite this rigor of questioning what are the real sister taxa to cetaceans, the message most in the public and media have gotten is that there is some connection to hippos. Unfortunately, the connection to hippos also leads some people to examine hippos as examples of what the origins of whales were like, even though the fossil record of hippos goes only into the Miocene and the understanding of whether these earliest forms were semiaquatic or not is still very rudimentary.

Hippos, in my opinion, should be considered the poster-child for how paleontologists take their overgeneralized views of modern animal biology/ecology and infer it for fossil organisms without much, if any fustification. I wont go into this too much further, as a hippo-ecomorph rant(s) is certainly already partly written and worth spending some time on.

But, in the hopes of starting the hippo discussion, how they might relate to cetacean origins and better understanding their roles as examples of the semiaquatic "transitional" mammal, and to relate to a very recent paper recently brought to my attention, it is worth discussing one key point, underwater locomotion in hippos.

A recent paper by Coughlin and Fish (2009) about underwater locomotion in the modern common hippo is an informative look at what many people often see as a "transitional state" for the terrestrial to aquatic transition. This paper is excellent, and in an elegant way really get to the heart of how hippo underwater locomotion is unique, and perhaps a good, or not so good, example of how transitional forms may have made it into the water. I am not sure the parallels they draw between hippos as raoellids, or Pezosiren portelli for that matter, are sufficiently supported, but they gently bring it up as a future avenue for research and should be commended for calling attention to the subject in a rigorous way.

The funny thing is, I have seen these sorts of results from a study of this sort many years ago in the work of a master's student from the University of Florida, Matthew Mihlbachler. In his work, notably done on a budget with a stopwatch and VHS recorder, Matt was able to come to much of the same conclusions as Coughlin and Fish (2009). Though his thesis entailed multiple aspects of the paleobiology of some fossil rhinos (which includes some interesting work about paleodemography) Mihlbachler has only published a small amount of this data in a paper about a fossil brontothere with curiously similar short limbs he named Aktautitan hippopotamopus (NOTE: hippopotamopus is not a typo, see the paper for the etymology).

The best part about these two studies is that they ultimately come to the same conclusion - when you look at hippo underwater locomotion, they are unique. Though there may be some parallels to be found in the hydrostasis controls found in either group someday (as Mihlbachler hints at with some data in his thesis), at present all we can say is that, if hippos are a good example of a transitional semiaquatic mammal (which I am not sure I would claim they are), then many of the characteristics we see in whales that lead from that negatively buoyant transitional form need to be further explored (although Sandy Madar has done some excellent work along these lines, as has Lisa Cooper).

All in all, hippos are an excellent source of information for trying to understand how large mammals might adapt to a life that involves more regular use of water, and in that way they may be good examples of the "transitional form" - BUT the notion that the ancestor of cetaceans was a hippo in the way they are today, or worse, the way we THINK they are today, is poorly conceived and unrealistic.

fake Open Access publication

What can I say? This news from The Scientist was both so shocking yet so believable, that I feel a need to report it here, even though it has nothing to do with aquatic amniotes. I won't do this frequently, as I'd rather keep this focused on ideas and research, but this cannot be ignored. As the editor of an open access journal, PalArch's Journal of Vertebrate Palaeontology, an online, open-access peer-reviewed journal based in the Netherlands (that does not charge anything), I am more than a little interested in the world of open access journals.

Recently, a couple of graduate students from Cornell tested the peer review in the journal, The Open Information Science Journal, published by Bentham Publishers. They submitted a completely fake paper to the journal and without ever hearing any reviews, got a message back that their paper had been reviewed and was accepted. Then the journal asked for the processing fee of $800, which is when these students decided to withdraw the manuscript and avoid paying the money (they are graduate students, after all). This has loads of interesting implications, though I would urge caution in equating suspicion with wrongful or unethical acts. The workings of a journal can be complex and without further comment from the journal in question, I would argue that it is best to assume an error occurred until further information comes out.

Though I think this is either an anomaly from the normal workings of this journal, or only a problem within this journal alone, it does stimulate a question that I am sure is one many people's minds when one is faced with the page charges of many journals, including open access ones. Mainly, the notion of paying to publish a paper suspiciously sounds like a business practice that would work in opposition to editorial inclinations to reject papers, or even delay publications. From a purely business standpoint, when worries of reputation are excluded, it makes more sense to do less work for each paper, which could/should result in a reduced rigor of peer review. I doubt that is occurring with many of our esteemed open access journals, primarily because of the ethics on which they were started, but as open access journals become more common and numerous, the "pay-to-play" option should cause us all to be cautious. This problem is not new, and the idea of paying to publish papers in some journals, or even simply the politics of publishing in some high-profile journals, should have always caused us to wonder about how peer review varies from journal to journal, and even editor to editor. Publishing, just like science, is a human endeavor fraught with error and often bias. But that should encourage caution and discussion and NOT cause us to stop progress in a stalemate of suspicion.

For more on this story, see the report by The Scientist.com

Aquatic Mesozoic Mammals

I have been working on a Mesozoic mammal with some colleagues in Kansas (Michael Engel) and China (Dong Ren) and cannot help but comment on the strangeness that is the world of Mesozoic mammals, in particular those that are deemed "semiaquatic".

The poster-child for aquatic Mesozoic mammal is Castorocauda, the beaver-like docodontan from the Middle Jurassic Daohugou Beds of Liaoning Province in northern China. This is the same locality that has had the earliest gliding mammal, Volaticotherium, as well as some weird feathered dinosaurs like Epidendripteryx, and the mammal I am studying with Engel and Ren (I promise to share more about this critter when the paper is published). Castorocauda is an interesting animal, if anything because it shows few specializations for an aquatic life other than a beaver-like tail, unusual limb proportions, and larger than normal body size for a Jurassic mammal.

Back in 1994, Fred Szalay proposed that stagodontid marsupials, found in the Cretaceous of North America, were aquatic, based on the morphology of the bones in the ankle. In 2005 Nick Longrich presented an abstract at the meeting, Evolution of Aquatic Tetrapods in Akron, OH (hosted by Hans Thewissen at NEOUCOM), detailing how stagodontids might have been durophagous and semiaquatic, based on aspects of their dentition and postcrania, especially a caudal vertebra that resembled those dirsoventrally compressed caudal vertebrae of beavers which are also found in Castorocauda. Recent studies of stagodontids (Fox & Naylor 2006), however, have discredited these claims of being stagodontids as aquatic, although it would be interesting to see if some of Longrich's ideas can be further explored.

So, if semiaquatic mammals are rare in the Mesozoic, why? It has been fairly well documented that being semiaquatic (whatever that means - I'll rant on this some more in the future to be sure) is energetically more costly than being either fully terrestrial or fully aquatic (Williams 1999), so that may have been a hurdle impassible for them, but then why would so many other mammal groups manage it in the Cenozoic even strictly in freshwater, from a variety of body sizes such as desmans to beavers? Mesozoic mammals had been pegged as limited to smaller body sizes in the past, but it is increasingly evident that this was not the case.

I would suspect it is something altogether much less exciting, and much more mundane, expected, and depressing - the fossil record. The "pull of the recent" strikes again, and this time I wouldn't be surprised that because the fossil record of Mesozoic mammals is limited by exposures and the longer periods of time in which fossils may have been destroyed, we simply have fewer of them.

Plus, it is really hard to recognize some of the subtler aspects of adaptations for being semiaquatic in gorups which are still fairly rarely known from anything more than fragmentary teeth and jaws. Hell, if you had a river otter jaw in your hand, would you know it was semiaquatic? No, at least not until we start getting to understand the finer relationships of the skeletal and dental adaptations of aquatic and semiaquatic mammal mammals in a broader context.

Hmmm.... that is a tempting distraction from Mesozoic mammals, isn't it?

update on Cetacean response to climate change

I was just reading over another recent paper that may also prove relevant to this post as well as the previous one, so I thought I would post an update.
Site fidelity in cetaceans is not new, but a recent paper by Valenzuela et al (2009) does an excellent job showing that for at least some large mysticetes, site fidelity is a matter of cultural inheritance, and can cause a lack of flexibility (at least in the geologically speaking 'short term') of feeding grounds for some taxa even in bad years.
Obviously, this report does not bode well for balaenids in the oncoming global warming situation, though it may be another facet worth exploring when considering prehistoric cetacean distributions. It may ultimately be outside the realm of possibility to answer such questions, particularly when we still don't have good estimates of simple things like body size of fossil groups (though I know one person is working on that) or how far different taxa may have regularly migrated (which may or may not be consistently related to body size).

Cetacean response to climate change

A very recent review paper by Colin McLeod (see here for Univ Aberdeen press release) in Endangered Species Research, titled, "Global climate change, range changes and potential implications for the conservation of marine cetaceans: a review and synthesis", raises some critically important points about the distribution of whales and how that is likely to be affected by expected changes in global climate. Obviously, this is very, very important for all of us that care about modern Cetacea as well as the health of the world's oceans in general.

But I would also urge marine mammal paleontologists to consider something else about this paper. Note that McLeod goes through and meticulously reviews the preferred habitats of most modern cetaceans. One should not be surprised to find that very few of these have a fossil record that goes back to the middle Miocene, when the world was much warmer, and the typical polarized distribution of modern cetaceans is, in reality, an effect of the repeated expansions and contractions of many cetaceans that have evolved in favor of colder waters (and its associated productivity) several times within the last 2-3 million years. This antitropical distribution splits sister species from each other by a warm patch of water in tropcical (and sometimes even subtropical) zones.

The conundrum in making the fossil record of whales informative of the problems we are facing today is that the fossil record of cetaceans is best for the Miocene, from a time when they were experiencing a cooling trend, not a warming. The fossil record of cetaceans during the Pliocene and Pleistocene may be better suited for such a comparison to the modern situation, but it is simply not as well studied (or perhaps as abundant) as the Miocene fossil record is. In that way, if one were to try to predict how marine mammals would respond to a warming trend, it would probably be ideal to very carefully explore how they handled this during glacial-interglacial cycles.

BUT, one edge that the Miocene (and likewise late Eocene) has over these glacial times is some insight in the way that cetaceans interact in marine ecosystems that are warm, like those that will eventually come with the changes being wrought on our world. If one wants to best understand how cetaceans may interact when warmer waters dominate the ocean landscape, the Miocene is perhaps a better model system than even the present day. Granted, modern animals are still FAR more important to understanding their future than any fossil taxon (with its own phylogenetic baggage to deal with that could influence the data), the total community structure, distribution patters, and even physical interactions may be in part better understood when looking at an almost worldwide warm world full of cetaceans in the Miocene. For instance, there are clear differences in the distributions of platanistids and eurhinodelphids in the West Atlantic during the Miocene, and better understanding why such similar animals would have latitudinally partitioned a very warm coast is almost impossible to understand from today's taxa, even though it may happen to many of today's species in the not too distant future.

If there are any graduate students looking for projects out there, one I can easily see would be ones utilizing some of Colin McLeod's other work on correlations of prey size and osteological correlates to answering these sorts of questions. Likewise, other groups that have a different response to climate change, seacows, may be a worthwhile avenue to explore some of these questions as well. I wish I could do it all, and though I am trying to get a start with the Sirenia part of the equation, in the end there are too many questions for one person to ask in a lifetime, and I hope someone out there will give some of these studies with cetaceans a try.

Preservation biases of fossil cetaceans

I have been quietly writing a series of posts for this blog, lengthy and full of figures, and now that I am close to posting some of them, I came across something short and sweet that I cannot resist posting about. So, I guess the longer posts will have to wait.

This morning, when I read the newest MarMamm listserv posts, I came across a new paper on minke whale habitat preferences off the coast of Scotland. Several years ago I would never have read that paper, mainly out of a lack of interest in focusing on baleen whales. Since then I have had the pleasure of working more closely with Alton "Butch" Dooley of the VMNH (see his blog). Butch has been finding numerous, well-preserved, mysticete skulls and skeletons in the Miocene age rocks of Carmel Church Quarry in Virginia. These animals are quite a puzzle at times, mainly because of their size they are rarely so well preserved, and the logistics of collecting them has deterred many in the past and resulted in specimens that a few and far between. Anyone working on dinosaurs may know how it feels, but suffice it to say that if you are interested in really understanding fossil species, preservation and sample sizes matter. As a paleobiologist, what Butch is collecting in VA is an ideal and rare opportunity.

Ok, back to the paper of the morning. Kevin Robinson and colleagues in Scotland and Wales very recently published a paper on the habitat preferences of modern minke whales in the journal, Journal of Coastal Conservation. In it, they present a consistent link between the distribution of minke whales (Balaenoptera acutorostrata) and habitat details, such as seafloor physiography and sediment type.

I know this is a stretch, but I cannot help but think that this close connection of some, but perhaps not all, mysticetes to a habitat type might be useful in explaining the distribution and preservation of large fossil cetaceans. I don't mean to push it too far, but this could serve a role similar to the way terrestrial paleo folks regard the lack of montane taxa preserved (or at least, they all should). I know it is logical, but it is nice to find modern support for the idea that the record of fossil mysticetes may be biased to those that prefer habitats that preserve well.

This may also be a point of curiosity regarding how/why we get physeterid fossils, even though physeterids are supposedly more pelagic. I don't mean that fossil physeterids were not pelagic, but it is worth considering all the possible influences on distribution of fossil cetaceans, and maybe use taphonomy to better understand what animals are part of a local fauna, and which are bodies washing into it from afar.

These are all things to think about, although perhaps nearly impossible to approach as a study due to the complications involved in confirming this sort of data widely for modern mysticetes, and even more difficult for attempting to link studies of physiography and sediment types with meticulously collected fossil mysticetes. But, I hope it is an entertaining thought for the day and look forward to any comments you all might have.
Cheers,
Brian