Romer’s Gap and the Four-Limbed Critters of Nova Scotia

The fossil record is a window into the past, but much of that window is boarded over. This situation spurs paleontologists to look in new places and new rocks, in an attempt to pry some of those boards off that window into our planet’s history. This is a great example of how paleontology is a testable science. Missing fossils from a certain time span? Look in rocks from that time span, and you should find them!

Romer’s Gap” presents a classic case of the incomplete fossil record. We know quite reliably that tetrapods–the four-limbed vertebrates including amphibians, reptiles, and us–originated around 370 million years ago. Fossils from 365 million years ago show distinct arms, legs, fingers, and toes on animals such as Acanthostega, leaving no doubt as to their tetrapod status. And we also know that tetrapods were pretty successful after that, because I’m using my tetrapod forelimbs (arms, hands, and fingers) to type out this blog post. But frustratingly, a time slice from around 360 to 345 million years ago yields precious few tetrapod fossils. This phenomenon was first noted by paleontologist Al Romer, hence its nickname of “Romer’s Gap“. The gap frustrates scientists because it is so soon after the origin of tetrapods, immediately before many important groups appear in the fossil record. That interval probably includes many events central for the transformation of tetrapods from leggy fish into truly terrestrial organisms. Tetrapods must have been around during Romer’s Gap, but where were they?

Romer's Gap is a ~15 million year interval, during which a whole bunch of tetrapod evolution presumably happened. Sites such as Blue Beach help to fill this gap. Eoherpeton at top modified from original by Nobu Tamura (CC-BY). Ichthyostega at bottom modified from public domain original by Scott Hartman.

Romer’s Gap is a ~15 million year interval, during which a whole bunch of tetrapod evolution presumably happened. Sites such as Blue Beach help to fill this gap.
Eoherpeton at top modified from original by Nobu Tamura (CC-BY). Ichthyostega at bottom modified from public domain original by Scott Hartman,

Various ideas have been proposed to explain the gap. Two front runners include:

  • Low atmospheric oxygen levels put a damper on land animals. No oxygen, no animals. But, it turns out that oxygen wasn’t that much lower than other times in history, and were actually higher than times just before the “gap”. Furthermore, marine waters should have had even lower oxygen (long story–I’ll just wave my hands and say “Chemistry!”), providing extra pressure for tetrapods to move onto land.
  • Artifact of collection and/or preservation. Is there a genuine gap in the fossil record? For any number of reasons, the fossil record is patchy. You might not have rocks from the type of environments to preserve particular organisms, or paleontologists just haven’t gotten around to studying the appropriate rocks yet.

As more paleontologists seek out more fossils, the latter hypothesis is starting to gain ground. A new study by Jason Anderson and colleagues, just published in PLOS ONE, provides additional support along these lines.

Rocks from the Horton Bluff Formation in Nova Scotia that yield fossils filling "Romer's Gap". CC-BY, modified from Anderson et al. 2015.

Rocks from the Horton Bluff Formation in Nova Scotia that yield fossils filling “Romer’s Gap”. CC-BY, modified from Anderson et al. 2015.

Blue Beach, rimming an estuary on the Bay of Fundy, has a long history of producing fossils from the time span including the base of Romer’s Gap. But, these rocks are notoriously hard to work. Wide swings in tidal levels limit working time to only a few hours a day, and most fossils are isolated bones difficult to assign to a particular kind of animal. Unless the finds are collected soon after exposure, they are lost to wave action. Thankfully, discoveries by local amateur paleontologists, in concert with fieldwork by external researchers, have slowly and steadily produced a stream of fossils.

The fossils described in the new study are nearly all isolated bones–individual limb, pelvic, and shoulder girdle pieces. But, by comparing them to more complete finds from elsewhere, it is possible to identify the specimens to varying degrees of precision.

Humerus (arm bone) of an early tetrapod from the Blue Beach locality. CC-BY, from Anderson et al. 2015.

Humerus (arm bone) of an early tetrapod from the Blue Beach locality; multiple views of the same fossil. CC-BY, from Anderson et al. 2015.

Let’s face it–the limb bones of early tetrapods are pretty clunky objects, lacking the sweeping and elegant lines of today’s salamanders, lizards, or mammals. The above image is a great example of a typical early tetrapod arm bone. But, each awkward ridge and bump points to the bone’s original owner. For instance, the bone shown here is similar to that of an animal called Pederpes, which belongs to a family of early tetrapods called Whatcheeriidae. Imagine something that looked like an ugly salamander, and you’ve got Pederpes.

All together, 37 different specimens (including isolated limb bones, skull bones, and even a handful of specimens with multiple bones from the same individual) were studied by Anderson and colleagues. The fossils could be referred to six or seven different groups of early tetrapods, showing that tetrapods were going strong even in the middle of Romer’s Gap. Some of these (closely related to Ichthyostega, shown below) are forms that are most closely associated with earlier times in earth’s history; one way or another, they made it through a big extinction just prior to Romer’s Gap. Maybe, then, the extinction didn’t hit tetrapods as hard as previously thought.

An ominous Ichthyostega. Silhouette by Scott Hartman via, public domain.

An ominous Ichthyostega. Bones from a closely related animal were found at Blue Beach. Silhouette by Scott Hartman via, public domain.

Blue Beach isn’t the only locality to plug Romer’s Gap–another recently described set of fossils from Scotland shows a similarly rich tetrapod ecosystem. Together, these localities in disparate parts of the world suggests that the purported gap in the fossil record is more a collecting artifact than the result of genuine rarity of these animals during their time. Anderson and colleagues perhaps summarize it best:

“It now seems that, whenever we discover rare windows into this time period, we find numerous fossil tetrapods reflecting a rich diversity of forms.” — Anderson et al. 2015

In other words, Romer’s Gap probably isn’t a real phenomenon! With more fossils, it’s getting shorter and shorter. This is so often the case in paleontology–and that’s a good part of what keeps us all out looking for fossils. A “gap” in the fossil record is just a challenge to overcome.

Anderson JS, Smithson T, Mansky CF, Meyer T, Clack J (2015) A diverse tetrapod fauna at the base of ‘Romer’s Gap’. PLOS ONE 10(4): e0125446. doi:10.1371/journal.pone.0125446

Category: Paleontology | Tagged , , , | 6 Comments

Brontosaurus thunders back!

Pretty much every person who ever read a dinosaur book or went to a natural history museum learned that Brontosaurus is just an outdated name for a big long-necked dinosaur that should be called Apatosaurus. Two different names were applied to the same type of animal, but Apatosaurus wins out because it was named first.

But…it’s just not that simple. It’s never that simple! In a move that is sure to generate considerable discussion by scientists and non-scientists alike, Brontosaurus is back. This topic is being covered in immense detail by many other writers, so I’m going to give just a quick tutorial here. In the interests of full disclosure, I should also note that I was the volunteer editor who handled this paper for the open access journal PeerJ. The opinions expressed here are solely my own.

An old school Brontosaurus, as envisioned in the late 1800s. After Marsh 1896.

An old-school Brontosaurus, as envisioned in the late 1800s. After Marsh 1896.

So, how do we resurrect Brontosaurus? It’s not just a matter of arbitrary scientific opinion–the authors of the new study, Emanuel Tschopp, Octávio Mateus, and Roger Benson–didn’t wake up one morning and say, “Hmm…let’s mess with people.” The work entailed a ridiculously awesome amount of hands-on study of specimens around the world, as well as detailed analysis of the features of the fossils to determine their evolutionary relationships.

Evolutionary relationships are the key–erecting, demolishing, or maintaining species and genera requires an understanding of how these organisms are related. Basically, if species of Brontosaurus are all mixed in with species of Apatosaurus, then the two animals should be recognized under one name (Apatosaurus). If, on the other hand, what used to be called Brontosaurus is evolutionarily well separated from species of Apatosaurus, then Brontosaurus stands up.

In order to see how the species are related, Tschopp and colleagues built a massive database documenting the anatomical features for numerous relatives of Apatosaurus–at the individual specimen level. This was the largest-scale study of its type ever done; most other studies (with few exceptions) have lumped specimens together under species, or have lumped species together into genera. A fine-scale approach, looking at individual specimens, turns out to be key. Once all of the specimens were coded, they were subjected to a phylogenetic analysis to determine which possible evolutionary trees best fit the data. In other words, a computer algorithm took the data and found which possible arrangement of evolutionary relationships made the most sense in light of the anatomical evidence. Animals that share more features changed from the ancestral condition (“derived features” in paleontological parlance) are assumed to be more closely related.

In the diagram below, which is roughly similar to a previously published analysis by Paul Upchurch and colleagues, note that the original Brontosaurus species (Brontosaurus excelsus) is in the middle of a whole bunch of Apatosaurus. Species more closely connected are more closely related–and here, the original Brontosaurus species is more closely related to the original Apatosaurus species than anything else. Unless one wanted to name each of those other species its own genus (a practice  employed for many other dinosaur groups), it made the most sense to keep Brontosaurus the same as Apatosaurus.

Tentative evolutionary tree of Brontosaurus and Apatosaurus

A hypothetical  view of the evolutionary relationships of Apatosaurus and Brontosaurus, based in part on a previously published analysis by Upchurch and colleagues. The dates at right indicate when each species was named. If this arrangement is correct, then Brontosaurus should be called Apatosaurus.

In their own analysis, Tschopp and colleagues found that Brontosaurus excelsus is well separated from the two species most traditionally considered Apatosaurus. Not only does the shape of the evolutionary tree show this, but the sheer quantity of differences also supported Brontosaurus as something different from Apatosaurus. By the paper’s standard of a “genus”, Brontosaurus fits the bill.

A new evolutionary hypothesis showing Apatosaurus and Brontosaurus as different genera.

In this arrangement, based on that found by Tschopp and colleagues, Apatosaurus and Brontosaurus are two different genera. As an interesting side-note, Brontosaurus parvus originally got its own name, Elosaurus. But, because it is “nested” within Brontosaurus, it keeps that name. As another side-note, Brontosaurus yahnaphin has also been called Eobrontosaurus. So, one could make an argument that BrontosaurusElosaurus, and Eobrontosaurus are all valid! This is where things can get a little subjective, but Tschopp et al. posit that the differences are few enough so that they should also be Brontosaurus.

So, Brontosaurus lives again! In terms of pop cultural significance, this is a pretty big deal–but in terms of scientific nomenclature, these kinds of things happen all of the time. In fact, the real treasure of the paper by Tschopp and colleagues is its in-depth approach to unraveling the evolutionary relationships of ApatosaurusBrontosaurus, and their relatives. This level of detail is becoming increasingly common for dinosaur research, and as demonstrated here can be a pretty handy tool for unraveling long-standing problems in identifying and naming species.

Brontosaurus has an unparalleled hold on the public imagination–its name aptly means “thunder lizard,” after all. As such, it’s a prime example for showing how scientists classify and reclassify organisms in light of new information.  Papers such as this, beyond taking care of naming species and genera, provide an important backbone for other analyses. If we want to understand the migrations and interchanges of dinosaurs between continents, we have to know how the various species are related. If we want to correlate the origination or extinction of species to climate changes or other global events, we have to have a solid grasp on these same relationships. Scientific progress thunders onward!

Tschopp E, Mateus O, Benson RBJ. (2015) A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda) PeerJ 3:e857

[post edited to add clarification on shared derived features, add links to other blog posts, fixed a typo or two]

Category: Dinosaurs, Paleontology | Tagged , , , , | 4 Comments

A digital head for Acanthostega

What has 16 fingers and a digital skull? Acanthostega, that’s what!

Acanthostega was one of the first limbed (rather than strictly “finned”) vertebrates, living around 365 million years ago in the shallow waters of modern day Greenland. Imagine something that looked roughly like a two foot long cross between a salmon and a salamander. As an odd evolutionary quirk, perhaps representing early experimentation in tetrapods (limbed vertebrates), Acanthostega had eight fingers on each of its hands. This critter is known from the nicely preserved fossils of several individuals, which has deservedly given it the title of “iconic” for our understanding of the transition from water onto land, for everything from feeding to locomotion.

<i>Acanthostega</i> in the flesh. "

Acanthostega in the flesh. “Acanthostega BW” by Nobu Tamura ( – Own work. Licensed under CC BY 2.5 via Wikimedia Commons.

Of course, we paleontologists are never satisfied with beautiful fossils. There always seems to be something that isn’t quite preserved, or is preserved in the wrong orientation for easy viewing, or is crushed in such a way as to render opinions on anatomy equivocal. Frustratingly, these kinds of details can be important for nailing down the finer points of evolutionary relationships as well as behavior and function. During the last two decades, non-invasive medical imaging techniques have been adapted for digital preparation and reconstruction of many fossils. Thus, it is increasingly easy to pull out previously inaccessible details of ancient anatomy.

Laura Porro and colleagues just published a paper detailing their new digital reconstruction of the skull of Acanthostega, based on CT (computed tomography) scanning of three different specimens. Each fossil had some degree of crushing or incompleteness, but together they essentially added up to a whole skull. The trick, of course, was getting them to all fit together.

The first step is to digitally remove the rock from the fossils. This process involves making a judgment in the grayscale CT scans as to where one ends and the next begins. When there is high contrast (perceived by us humans as sharp color differences in the scan), this can be done fairly automatically by the computer; in less clear cases, a human has to make this decision. Anatomical knowledge as well as a “feel” for the scan are key.

Although we often think of a “skull” as a single unit of bone, the head is in fact made up of a number of separate but interlocking bones. Thus, each bone digitally was separated from its neighbor. The result is a bunch of colored bones floating in space, which are in their original position as preserved but not necessarily life position.

The original "squished" skull of <i>Acanthostega</i>. Modified from Porro et al. 2015, CC-BY.

The original “squished” skull of Acanthostega. Modified from original figure in Porro et al. 2015, CC-BY.

The next step is to fill in missing pieces and restore the skull to its life condition. Missing or incomplete bones could be replaced by scans from more complete fossils, scaled appropriately. Removing the post-death displacement of bones was a little more challenging. For animals with loosely-knit skull bones, individual bones tend to “sag” relative to each other after death, squishing some parts that weren’t originally squished. In the fossils, this can be evidenced through big gaps that obviously weren’t there in life, or through disturbingly overlapping bones that once again don’t look like anything in a living animal. Through digital manipulation, each bone can be scooted back to its life position relative to the other bones. Even in the best case this is a long and tedious process, and the authors clearly sank a lot of work into getting it right with Acanthostega. The result (below) is pretty dramatically different from the “as-is” fossil.

The "unsquished" skull of <i>Acanthostega</i>. Modified from Porro et al. 2015, CC-BY. I have combined two figures to better show the overall anatomy.

The “unsquished” skull of Acanthostega. Modified from Porro et al. 2015, CC-BY. I have combined two figures to better show the overall anatomy.

Although this isn’t the first attempt to “undeform” the skull of Acanthostega (previous pen-and-paper versions have been published), it is perhaps the best supported and most constrained by the fossil data. A quick glance at the original fossil as well as the digital reconstruction shows a number of difference between the two–the overall shape of the snout, position and size of the eye sockets, angulation of the back half of the skull relative to the front half, etc. The overall skull shape wasn’t the only thing that was newly revealed–the anatomy of some bones closely related to feeding (the quadrate bone, connecting the upper part of the skull to the lower jaws, for example) are also known for the first time.

There are no massive reinterpretations of the life, appearance or evolutionary history for Acanthostega in this paper, but that is okay. Nonetheless, descriptions of previously unseen bones and relationships between bones help generate refined hypotheses for future testing. For instance, Porro and colleagues further confirmed a previously suspected gap between bones on the top of the snout called the midline rostrals and nasals. This gap wasn’t immediately visible on the fossils themselves, but was unavoidably open when reassembling the skull on the computer. Some other early tetrapods also show this feature, and thus it might be handy for clarifying evolutionary relationships between these species.

Porro and colleagues also were able to describe the shape and texture of the contacts between individual bones (typically called sutures) at a new level of detail. The nature of these sutures–whether they are tightly linked from bone to bone, broad, narrow, sinuous, or whatever–can be correlated with feeding style. Something chowing down on actively wriggling prey might want to have a beefy skull with sturdy attachments between bones, for instance. If different parts of the skulls are used differently, this might also be reflected in the sutures. Some arrangements show resistance to being pushed together or pulled apart, and others show resistance to twisting. In the case of Acanthostega, it is hypothesized that the front of the skull was used for nabbing live prey (based on the teeth as well as the sturdy connections between bones on the front and roof of the skull). In contrast, the mid-section (as shown by the more loosely connected bones on the roof of the mouth and in the cheek) was more of a “stabilizer”, holding prey in place as Acanthstega swallowed. These interpretations can now be worked out in more detail using computer models.  Overall, the evidence from this and other studies points towards Acanthostega feeding underwater (perhaps as a suction feeder), rather than on land.

The field of digital paleontology is no longer as new and shiny as it once was–indeed, CT scanning is now a fairly standard technique for many scientists. But, the case of Acanthostega once again shows how digital fossils have moved from “gee whiz we scanned a specimen” into “here’s a whole bunch of new anatomy and behavior.” Although it would have been pretty cool to see this animal devour live prey, I just as much like the fact that it’s now devouring internet bandwidth as I read the open access paper and soak in the beautiful imagery!


“Explodostega”. Modified from Porro et al. 2015, CC-BY.

Soapbox Addendum
On a final note, I particularly commend the authors for including this phrase in their paper:

It should be noted that the 3D model represents our hypothesis of the reconstructed skull of Acanthostega, based on available specimens, scan resolution and personal interpretation.

When I read that sentence, I practically wept sweet tears of replicable science joy. As I have stated elsewhere, even in the best cases CT reconstructions require a certain level of finesse, practice, and personal judgment, with the strong possibility of alternative interpretations. It is wonderful to see that fact acknowledged in the literature–this is pretty rare otherwise. Additionally, although I strongly prefer that raw scans themselves be made available whenever possible, the authors have done a good thing by indicating that the scans are archived at the institution housing the original fossil specimens. I’m glad that there are more and more people thinking about reproducibility in digital reconstructions.

Porro LB, Rayfield EJ, Clack JA (2015) Descriptive anatomy and three-dimensional reconstruction of the skull of the early tetrapod Acanthostega gunnari Jarvik, 1952. PLOS ONE 10(3): e0118882. doi:10.1371/journal.pone.0118882

Category: Digitization, Paleontology, PLOS ONE | Tagged , , , , , | 4 Comments

Beefy Bones and a Big Bite for the Ancient Whale Basilosaurus

Basilosaurus life restoration by Dmitry Bogdanov, CC-BY.

Basilosaurus life restoration by Dmitry Bogdanov, CC-BY.

Although its name sounds rather dinosaurian, Basilosaurus was in fact one of the first extinct whales to make a splash in humanity’s perception of the past.

When its bones were first described back in the early 19th century, the anatomy of the backbone was thought to most closely resemble that of some Mesozoic marine reptiles. Later work, and examination of other parts of the skeleton, revealed Basilosaurus to be an early whale that lived around 34 million years ago. Of course, more recent discoveries have since produced older whales with even more “primitive” features, but Basilosaurus and its close relatives remain important for piecing together the details of whale evolution. This past week, two papers in PLOS ONE added more information on the internal anatomy of the bones of Basilosaurus as well as its strong bite.

The first paper, by Alexandra Houssaye and colleagues, used computed tomography (CT) scans to peek inside the limb bones, vertebrae, and ribs of a number of early whales. For the purposes of this post, I’ll just focus on Basilosauruscheck out the paper for the story with the other species, which is pretty interesting in its own right.

Rib of Basilosaurus--note its high density, a common feature of whale ribs. Modified from Houssaye et al., 2015. CC-BY.

Rib of Basilosaurus–note its high density (gray is bone tissue, black is empty space), a common feature of whale ribs. Modified from Houssaye et al., 2015. Scale bar equals 10 mm. CC-BY.

Two distinct adaptations are common in the bones of aquatic amniotes (birds, reptiles, and mammals) that forage underwater. The first is Bone Mass Increase (BMI); this is achieved by making bone denser (getting rid of spongy bits) as well as by adding more bone tissue to an individual bone. The second adaptation is, by contrast, creating spongy bones with internal struts to hold up to the forces of swimming. Presumably, both of these adaptations evolved in order to maintain optimal buoyancy while enabling effective locomotion.

Basilosaurus had ribs largely made of compact bone, typical of whales (even those today). Its arm and thigh bones were also quite compact and dense, unlike the condition in some other early whales. This is actually a bit of a puzzle, because it is fairly different from close relatives of Basilosaurus that have less dense arm bones (presumably tied to swimming style), and doesn’t match with the overall picture of Basilosaurus as a predatory animal that lived in open waters. Because the hind limbs were fairly useless, it doesn’t make a lot of sense that they would have such dense bone (no need to stand up to big muscular forces). The basic conclusion: more research is needed. The study by Houssaye and colleagues provides some important data points to launch future investigations.

Blue Skull of Death. Computer reconstruction of the skull of Basilosaurus, with jaw muscles added. Modified from Snively et al. 2015. CC-BY.

Blue Skull of Death. Computer reconstruction of the skull of Basilosaurus, with jaw muscles added. Modified from Snively et al. 2015. CC-BY.

The next paper under consideration turned to the business end of Basilosaurus–its skull. Fossilized stomach contents showed that Basilosaurus chowed down on fish, wear patterns on the teeth suggested at least some shellfish in the diet, and tooth marks on the bones of other whales indicate a habit of chomping anything willing (or unwilling) to be eaten. Presumably Basilosaurus had the bite force to dent bone–could this be confirmed?

Eric Snively and colleagues constructed a computer model of the skull of Basilosaurus, complete with simulated musculature. After crunching all of the numbers, they estimated that this long-dead whale packed over 16,000 N of force in its bite (and potentially even more, depending upon the conditions invoked). This blows the bone-crushing hyena out of the water–our poor terrestrial pal weighs in at a “paltry” 3,500 N for measurements of bite force in captive animals.

The bite of Basilosaurus sounds impressive–and it certainly is–but context is everything. With a skull measuring over a meter long, Basilosaurus was far larger than hyenas. Big head, big bite. Modern crocodilians have a bite force well beyond that of Basilosaurus, and ancient marine reptiles and the “land shark” Tyrannosaurus also would have won in the cranial equivalent of an arm wrestling contest. Differences in skull size as well as muscular configuration are probably in play here. As Snively and colleagues suggest, it would also be nice to see how the bites of modern whales stack up (e.g., orcas). We’re only beginning to understand the evolution of whale bites.

So…we have a lot more information on Basilosaurus, but not much in the way of explanations or answers. Perhaps that is frustrating for some. As for me, I like these new mysteries. Science is at its best when it has questions to investigate!

Houssaye A, Tafforeau P, de Muizon C, Gingerich PD (2015) Transition of Eocene whales from land to sea: evidence from bone microstructure. PLOS ONE 10(2): e0118409. doi:10.1371/journal.pone.0118409

Snively E, Fahlke JM, Welsh RC (2015) Bone-breaking bite force of Basilosaurus isis (Mammalia, Cetacea) from the Late Eocene of Egypt estimated by finite element analysis. PLOS ONE 10(2): e0118380. doi:10.1371/journal.pone.0118380

Category: Paleontology, PLOS ONE | Tagged , , , , , , | 3 Comments

What is the scientific literature used for?

For better or for worse, we paleontologists (and many other scientists) view the use and importance of the literature in terms of citations. Citations are what drives the ever-beloved impact factor, as well as other metrics such as the h-index. Indeed, this focus on citations colors many discussions on access to the literature, such as the relative importance of rapid electronic access. You’ll hear lots of statements along these lines: “If you are in the business of writing a manuscript, but don’t have access to a particular piece of literature, you can always use interlibrary loan or a similar service. Or just got to the university library next door. Patience is a virtue. It won’t kill you (or science) to wait a few extra days.”

Oh, for everyone to have a library like this on their doorstep! Or at least the electronic equivalent. Stockholm Public Library, photo by Samantha Marx, CC-BY.

Oh, for everyone to have a library like this on their doorstep! Or at least the electronic equivalent. Stockholm Public Library, photo by Samantha Marx, CC-BY.

Although I don’t completely discount this idea (indeed, we all have seen our share of PDF requests that could have been fulfilled with a few extra seconds of Googling), I think it reflects a rather anemic view of how the scientific literature is used by scientists. Citations are certainly an easily trackable mode of literature use, but (as noted time and time again by advocates of “alternative metrics”) the literature is used for more than just writing papers. Particularly in a field like paleontology, which has a strong record of public interest and public engagement, these non-citeable uses can be myriad.

So, I decided to put together a quick list of the different ways that I use the scientific literature on a day-to-day basis. In particular, I’ve noted some areas where timely (i.e., near-immediate) access is highly desirable.

How do I use the literature?

  • Background research for teaching. I teach a one month introduction to paleontology / evolution in the fossil record course for high school freshmen, and this is a topic for which there isn’t a good textbook for all of the content we cover (although Neil Shubin’s Your Inner Fish does an excellent job with talking about homology, development, and the fossil record). And even if there was a comprehensive textbook, I still want to sprinkle my lectures with examples from the literature, images from papers, and the like, as well as bring in relevant material from recent publications. Thus, I not infrequently turn to the primary literature.
  • Background research for a media interview. Every once in awhile, I’m contacted by a member of the news media to provide an opinion on a piece of new research. Although I do not generally accept interview requests for topics outside my area of expertise, even for topics within my area of expertise I sometimes want to brush up on a particular fact or research some of the context behind a particular story. For instance, I’m quite comfortable talking about horned dinosaurs–but if it’s a horned dinosaur from a place I don’t know much about, I might head to the literature to brush up on the overall context. This may or may not come up in the interview, but I want to be prepared to represent the science as accurately and completely as possible. Time is of the essence here!
  • Research for public talk. When developing a talk for a public audience (I give between 5 and 10 annually, for museums, community groups, and other events), I sometimes need to delve into a new topic. Maybe it’s to see what else has been found in a particular formation (it’s always nice to throw in “local color”), or just to understand a particular point on a related topic.
  • Reviewing manuscripts. Although I only accept review requests for manuscripts within my area of expertise, I frequently refer back to the literature to double-check claims made by the authors, suggest additional references, and refresh my memory on relevant details of anatomy, statistics, or geology. Review turnarounds are usually between 10 and 30 days, and it is not uncommon to be polishing a review a few days (or hours) before it is due. Waiting two weeks for an ILL isn’t a good use of time, or fair to the authors and editors who expect timely reviews. I’m certainly not going to drop $40 for a PDF in this case, either (particularly because publishers don’t reimburse for these kinds of expenses).
  • Reviewing grant applications. The same logic as for reviewing manuscripts applies to reviewing grants.
  • Writing manuscripts. I’ve buried this one in the middle of the list to emphasize that it is only one of many uses. There are few things more frustrating than being in the final push to finish a manuscript, and finding out there is a seemingly critical paper tantalizingly out of reach behind a paywall.
  • Identifying specimens in a museum collection. In the process of curating a museum collection, I am called upon to ensure that all of our cataloged specimens are identified as precisely and accurately as possible. In some cases, past experience guides me and others who work in the collections. However, parts of our collections (particularly historically collected ones) are somewhat outside my expertise (e.g., oreodonts and trilobites). Off to the literature! A well-illustrated paper can be invaluable for pinning down an identification. (how well some papers achieve this, though, is the topic of another post)
  • Providing information on a topic to a colleague or member of the public. At our museum, we’ll sometimes have folks drop by for a fossil identification, or we might get a question about a particular paleontological topic. If it’s something that’s outside the realm of popular books (and let’s face it, if it’s not a dinosaur, it’s probably not in a book), off to the literature!
  • Writing museum exhibit text. I am fortunate to have the opportunity to assemble temporary exhibits for my museum sometimes, focusing on fossils from our collection that tell a story about Earth’s history and our connection to it. But, I am not necessarily an expert on every fossil that I think is exhibit-worthy. So, off to the literature I go! Temporary exhibits here are frequently the result of reading or skimming at least a few papers on the topic.
  • Reference for artistic project. Every once in awhile, I’m lucky enough to work with an artist to illustrate a new discovery made by my museum and colleagues, or I am contacted by an artist who wants an opinion on a particular piece of work. My extensive photo library comes in handy, but I also rely extensively on the literature. If there’s a question about the plants found in a particular environment, or the scale pattern on the skin in a particular group, or the types of non-dinosaurs that lived at a relevant time in history, I’ll often turn to previously published work.

I’m sure I’ve probably missed something–how do you use the literature? Sound off in the comments section!

Category: Open Access, Publishing | Tagged , , , , | 5 Comments

The Open Access Dinosaurs of 2014

As we enter 2015, it’s a good time to reflect on the state of paleontology and the state of open access. Because I’m a dinosaur paleontologist (my apologies to the other 99% of life that ever lived), this post will of course address that clade in particular!

<i>Ziapelta</i>, one of the new open access dinosaurs named in 2014. Illustration by Sydney Mohr, from Arbour et al. 2014. CC-BY.

Ziapelta, one of the new open access dinosaurs named in 2014. Illustration by Sydney Mohr, from Arbour et al. 2014. CC-BY.

Thirty-eight new genera or species of dinosaur were announced in 2014 (according to my count based on a list at Wikipedia and the Dinosaur Genera List), spanning everything from sauropods to tyrannosaurs to horned dinosaurs. Seventeen of these were published in open access or free-to-read journals. This works out to around 45%.

PLOS ONE continues to dominate the world of open access dinosaur species–9/17 were published here. I will be very interested to see if this trend continues into future years, particularly as more open access journals enter publication. Seven other journals hosted open access or free-to-read papers on new taxa. These included publications hosted by professional societies, “big publishers,” museums, and the like.

You’ve probably noted by now that I’ve been parsing a difference between “open access” and “free to read.” The former category includes those that are fully BOIA-compliant; usually this means publication under a Creative Commons Attribution (CC-BY) license. This freely allows redistribution, repurposing, translation, and other uses, as long as the author is credited (interestingly, I note that many critics of CC-BY conveniently forget that authors must always be attributed). 11 out of 17 species were published under a CC-BY license. The remainder were under a variety of licenses (e.g., CC-BY-NC-SA). I will confess a certain amusement at the “NC” (non-commercial) clause, particularly when used by very much for-profit and very much commercial publishers (to their credit, a strict CC-BY license is now the default offering for NPG’s Scientific Reports).

Overall, 2014 (17/36 new taxa are free-to-read) doesn’t reflect a big change from 2013 (16/38 free to read). I would be interested to see what percentage of the overall paleontology literature (not just alpha taxonomy) is freely available–anyone up to collating this?

Full disclosure: I was an author on one of the papers naming a new dinosaur this year, and was handling editor for some of the other papers naming new dinosaurs. 

Appendix: The Data

Taxon Freely readable CC-BY? Journal
Adelolophus No No
Arcovenator No No
Augustynolophus No No
Changyuraptor No No
Daurosaurus No No
Eousdryosaurus No No
Gobivenator No No
Gongpoquansaurus No No
Kulindadromeus No No
Kulindapteryx No No
Laquintasaura No No
Mercuriceratops No No
Panguraptor No No
Pentaceratops aquilonius No No
Plesiohadros No No
Qianzhousaurus No No
Quetecsaurus No No
Rhinorex No No
Vahiny No No
Zaraapelta No No
Zby No No
Allosaurus lucasi Yes No Volumina Jurassica
Datanglong Yes No Acta Geological Sinica
Dreadnoughtus Yes No Scientific Reports
Fosterovenator Yes No Volumina Jurassica
Rukwatitan Yes No Journal of Vertebrate Paleontology
Huangshanlong Yes No? Vertebrate PalAsiatica
Anzu Yes Yes PLOS ONE
Aquilops Yes Yes PLOS ONE
Chuanqilong Yes Yes PLOS ONE
Leinkupal Yes Yes PLOS ONE
Nanuqsaurus Yes Yes PLOS ONE
Tachiraptor Yes Yes Royal Society Open Access
Tambatitanis Yes Yes Zootaxa
Torvosaurus gurneyi Yes Yes PLOS ONE
Yongjinglong Yes Yes PLOS ONE
Zhanghenglong Yes Yes PLOS ONE
Ziapelta Yes Yes PLOS ONE

Note: The taxa Camarillasaurus and Oohkotokia were published “officially” in 2014, but made their initial (pre-print) appearance in past years, so I don’t include these open access dinosaurs on the list.

Category: Dinosaurs, Open Access, PLOS ONE, Publishing | Tagged , , , , | 5 Comments

2014: A Great Year for Hupehsuchia

Hupehsuchus, in silhouette. Public domain image by Neil Kelley via PhyloPic.

Hupehsuchus, in silhouette. Public domain image by Neil Kelley via PhyloPic.

I just can’t get enough of those bizarre hupehsuchians! These ancient marine reptiles–known exclusively from ~248 million year old rocks in China–had a tubular, bone-encased torso, toothless jaws, and flippers often sprouting an extra finger and toe or two. In a previous blog post, I noted that they’re probably best described as a “swimming sausage topped with armored mustard”.

Formerly a poorly-known group (both in the literature as well as in general paleontological awareness), Hupehsuchia underwent a scientific transformation in 2014. A wave of newly described specimens has washed through the literature, highlighting the diversity of species and body plans in this group. Additionally, recent studies and new discoveries have clarified their relationships–these animals were probably most closely related to the famous icthyosaurs, or fish lizards. Just in time for the holidays, yet another hupehsuchian has been announced.

Skeleton of Eohupehsuchus; the head is at the left of the image. Modified from Chen et al. 2014. CC-BY.

Skeleton of Eohupehsuchus; the head is at the left of the image. Modified from Chen et al. 2014. CC-BY.

Our newest character is called Eohupehsuchus brevicollis, and it’s a tiny thing (full disclosure: I was the handling editor for this paper). The whole body, when complete, might have been less than 30 cm (~1 foot) long, and the head is a little shorter than a typical human thumb. The animal had a relatively shorter neck than many of its close cousins (hence the species name “brevicollis“, which means “short neck”), and its limb bones also happen to be much more ossified than is typical for a hupehsuchian. This feature, among others, suggests that Eohupehsuchus probably isn’t just a tiny juvenile of some larger, better known species; juveniles of most animals tend to have less densely ossified bones than do adults.

There are now a total of four named species of Hupehsuchia, and at least one more is on the way. Remarkably, all of them lived within a fairly small geographic area (<80 km separation between all known fossils) and within a limited time interval (2 or 3 million years, max). Chen and colleagues, the authors on the study naming Eohupehsuchus, speculate that all of these species were able to coexist so happily due to differences in body size and shape–thus indicating different lifestyles that ensured ecological separation.

So…in the year 2014, Hupehsuchia doubled the number of named species. Long-hazy details of anatomy were resolved, and as a result, the evolutionary relationships of hupehsuchians to other marine reptiles are now more certainly known than ever before. Not bad for an armored swimming sausage!

Still craving some hupehsuchian action? Check out my previous posts on other discoveries from 2014!

Skull (photograph and interpretive drawing) of Eohupehsuchus. The tip of the snout is to the left of the image. From Chen et al. 2014. CC-BY.

Skull (photograph and interpretive drawing) of Eohupehsuchus. The tip of the snout is to the left of the image. From Chen et al. 2014. CC-BY.

Chen X-H, Motani R, Cheng L, Jiang D-Y, Rieppel O (2014) A carapace-like bony ‘body tube’ in an Early Triassic marine reptile and the onset of marine tetrapod predation. PLoS ONE 9(4): e94396. doi:10.1371/journal.pone.0094396

Chen X-H, Motani R, Cheng L, Jiang D-Y, Rieppel O (2014) The enigmatic marine reptile Nanchangosaurus from the Lower Triassic of Hubei, China and the phylogenetic affinities of Hupehsuchia. PLoS ONE 9(7): e102361.doi:10.1371/journal.pone.0102361

Chen X-H, Motani R, Cheng L, Jiang D-Y, Rieppel O (2014) A small short-necked hupehsuchian from the Lower Triassic of Hubei Province, China. PLOS ONE 9(12): e115244. doi:10.1371/journal.pone.0115244

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Assembling the Aquilops Paper

In my previous post, I introduced Aquilops, a new little dinosaur from ancient Montana, and talked about some of the science behind establishing its identity. Here, I want to step back (or is that look down?) for a little navel-gazing about the process behind the paper (and you can read the paper here).

Reconstruction of Aquilops, by Brian Engh. CC-BY.

Reconstruction of Aquilops, by Brian Engh. CC-BY.

I was a real latecomer to the project. Scott Madsen, a wonderfully skilled paleontologist and fossil preparator, found the fossil back in the late 1990s. This was on a National Geographic Society-funded expedition headed up by Rich Cifelli (Sam Noble Oklahoma Museum of Natural History) and Des Maxwell (University of the Pacific). After Scott found the skull, he did the preparation on it, and passed it on to Des and Rich. They, in turn, set to work on the research and formal description. Life and work caught up with everyone, so the manuscript aestivated for a time. Matt Wedel (who was Rich’s graduate student) ended up moving to the same town as me, we became good friends (and babysitters of each other’s kids–thanks, Matt, for helping out last night!), and Matt thought he’d suggest bringing me on board for the project [read more of Matt’s side of the story here]. By that point, I had personally seen many of the Chinese ceratopsians that weren’t described at the time of the discovery of Aquilops, so I could genuinely contribute to the research and provide broader context. Des and Rich agreed to bring me on, so in the fall of 2010, Matt and I drove up to Des’s town to pick up the specimen, and we all got to work.

Thankfully, Des and Rich had done a bang-up job with the original manuscript–in fact, their diagnosis of Aquilops is largely unchanged from the original manuscript to the published paper, as are the basics of the description. Because the manuscript was originally formatted for a short-paper journal, we made the decision to expand it into a monograph-type treatment of the fossil. This would allow us to really do justice to an amazing fossil. Thus, we had to take the basics of the first manuscript and plunk in additional comparisons and figures, as well as add some detailed biogeographic analyses.

For me, this project was fun for several reasons. First, I got the opportunity to work on a cool fossil. There had been rumors and rumors of rumors of an Early Cretaceous ceratopsian skull from Montana, so it was rather awesome to hold the thing in my hands and be involved with the scientific research. Second, this paper stretched my writing abilities. I learned much from my co-authors, particularly Rich, about tightening prose and presenting a scientific story for a broad audience. Because Rich’s expertise is mainly in fossil mammals, he was constantly pushing me to make the tale of Aquilops and its biogeography accessible to non-dinosaur workers. Des Maxwell and Matt Wedel in turn added their own text and polish to my text. I also greatly enjoyed getting to see Scott Madsen’s handiwork up close. As a paleontologist usually removed from the prep lab, it is easy to forget how much we really owe to preparators. Without Scott, Aquilops would still just be some teeth sticking out of a lump of rock.

Another thing I greatly enjoyed was delving into the realm of biogeographic analysis. Although some of my previous papers have had a biogeographic slant, I’ve never really had cause to use some of the more advanced analytical techniques that are becoming the standard for paleontology. Thus, the Aquilops project pushed me into a new scientific realm. Along the same lines, I also did a lot of hard thinking about paleogeographic reconstructions–those pretty maps showing past connections between continents. As I delved into that literature, particularly for the Lower Cretaceous, I learned more and more just how much uncertainty there was. I had always had a rough feeling for this, but the Aquilops project really drove the point home.

Phylogeny of horned dinosaurs, from Farke et al. 2014. CC-BY.

Phylogeny of horned dinosaurs, from Farke et al. 2014. I am really quite proud of this figure, which summarizes a great deal of information in a compact space. That includes everything from what the dinosaurs looked like, to when they lived, to how they were related to each other, to their biogeography. This final product was produced only after many consultations between the various authors. CC-BY.

Random Thoughts
To finish out this post, I thought I’d throw out a few random thoughts that are useful to share, but don’t really warrant their own post. Here goes!

  • PhyloPic is awesome. This website hosts silhouettes of various organisms, all of which are explicitly licensed for reuse by other workers. A variety of CC-BY ceratopsians were already available, and I generated a few other images where necessary.
  • Open source software was invaluable for this paper. All of the figures I produced were generated within GIMP or Inkscape, and then exported as TIF files. For the figure of the digital surface scans, the initial images were captured in Meshlab. All bibliographic work, except for the final polish, was completed in Zotero.
  • It was nice to put multiple 3D formats of surface scans in as supplemental information with the paper. Although 3D PDFs are handy on some levels, they can be…quirky…within various browsers and operating systems, so OBJ and STL files are a little more universally guaranteed to work. Plus, if we were going to all the work of scanning the specimen, we might as well make it so people can easily find and use the darned scans.
  • One nice use of the 3D scans was that we could produce color-free surface models that could then be annotated to produce a figure of the specimen. This removes discolorations in the specimen that obscure details, and is a trick I first learned from Joe Sertich on our Dahalokely paper. This was also done the “old fashioned way” for the teeth, by Rich and the folks at the OMNH. In that case, an ammonium chloride-coated cast showed the detail much better than the digital scan could (due to limits in scan resolution). See also this post on figuring fossils for more on why removing color is a good thing sometimes.
  • I am really pleased that we had the space to document the specimen so completely, including multiple photographic views, interpretive drawings, and measurements. On the latter point, it all traces back to Matt Wedel’s classic post, “Measure Your Damned Dinosaur.” Although aspects of our interpretations and analyses will inevitably be superseded by future discoveries, the data will always stand.
  • The folks in Oklahoma are working on a really, really nifty museum exhibit to highlight the fossil of Aquilops, which permanently resides in their collections. Digital artist and exhibit technician Garrett Stowe, in collaboration with preparator Kyle Davies, has been doing some amazing stuff to reconstruct the skull of Aquilops as well as the entire animal. Get a sneak peek at the Sam Noble Oklahoma Museum of Natural History website!

That’s all for now! I highly recommend checking out any number of other posts related to this article, including Matt Wedel on the history of the project, Brian Engh on the artwork, and a nice web page from the folks in Oklahoma on their fossil specimen. You can also read the original paper at PLOS ONE.

Category: Dinosaurs, Navel Gazing, Open Access, Paleontology, PLOS ONE, Publishing | Tagged , , , , , , | 1 Comment

Aquilops, the little dinosaur that could

Today, several colleagues and I named a really cute little dinosaurAquilops americanus. At around 106 million years old, Aquilops turns out to be the oldest “horned” dinosaur (the lineage including Triceratops) named from North America, besting the previous record by nearly 20 million years. Even more interesting is the fact that Aquilops is not at all closely related to later horned dinosaurs from North America, but is mostly closely related to forms that lived in Asia around the same time. This is in line with a growing body of evidence showing an exchange of animals between the two continents at that time.

Aquilops in life, by Brian Engh. CC-BY.

Aquilops in life, by Brian Engh. CC-BY.

To learn the major details, you can of course check out the paper in PLOS ONE or read any number of news articles and blog posts on the find. For the rest of this post (and probably one or two other posts), I instead want to talk about some things that weren’t necessarily discussed in the paper or the press. [note: I should definitely add that the fossil is housed at the Sam Noble Oklahoma Museum of Natural History; Matt Wedel has more over at his blog, and I’ll add some on the history of the project in an upcoming post]

What’s with that bump on the front of the beak?
The rostral bone, which forms the upper beak and is a feature that unambiguously identifies Aquilops as a horned dinosaur, has a funky bump on the front of it. I spent a lot of time up-close with the specimen in hand and under a microscope, trying to convince myself that it wasn’t just some piece of bone displaced by crushing. In the end, I’m pretty certain that it’s a “real” feature; i.e., something the animal had while it was alive. Perhaps it’s pathological (abnormal) bone, but once again the texture doesn’t look ugly enough for that to be my preferred explanation.

At any rate, this animal had a funky bump on the front of its face. No idea what it was for (fighting? digging? something else?), but it sure was cool.

Skull and lower jaw of Aquilops, in my hand for scale. CC-BY.

Skull and lower jaw of Aquilops, in my hand for scale. CC-BY.

That animal is pretty small! How do you know it’s not just a baby?
It is indeed small! Based on Matt Wedel’s estimates, it was probably about the size of a large raven and body mass of a bunny rabbit (we only have a skull, so this was based off scaling from more complete skeletons of closely related species, such as Archaeoceratops [body mass statement corrected after initial post]).

As you can see from the picture, the skull could fit pretty neatly into your hand. The overall head is a little less than two-thirds the size of the largest published skulls of its closest relatives (Liaoceratops and Archaeoceratops), so based on size alone I suspect it’s not fully grown. The bone texture is also consistent with a young-ish animal.

But…other features (such as the development of the teeth and the comparatively close fusion between some bones) suggest that although the animal was young, it probably wasn’t a baby (or even a kid). I imagine it something like the Aquilops equivalent of an adolescent or maybe a teenager.

Can’t you just slice up the bone to determine the age?
Unfortunately, we don’t have any limb bones, which are the gold standard for determining dinosaur age. Skull bones are a possibility (and have been used for some dinosaurs, at least to determine relative age), but…the growth and changes in skull bone are very poorly characterized (especially relative to calendar age), and virtually nothing is known about skull bone growth in early ceratopsians. Thus, microanatomy of skull bones probably wouldn’t be that informative.

Why name a new species if it the animal is not fully grown?
It is no secret that dinosaurs change–sometimes radically–as they grow up. So, this can raise some concerns about whether or not species should be established based on young specimens. However, I am pretty comfortable naming Aquilops as a new species, even if the skull is from a young individual. Several features of the skull–including the unique shape of the beak as well as some combinations of features in the skull–distinguish Aquilops from other animals. Many of these features seem to be fairly stable through the life of an animal in species where we have large samples (e.g., beak shape). Thus, there is little to suggest that we wouldn’t recognize a larger and older Aquilops when and if we find one.

Aquilops to scale next to a human. They look like they would make cute pets, but don't let that fool you--those beaks would have been sharp! Illustration by Brian Engh, CC-BY.

Aquilops to scale next to a human. A dinosaur at this size looks like it would make a cute pet, but don’t let that fool you–those beaks would have been sharp! Illustration by Brian Engh, CC-BY.

If you only have a skull, how do you know what the rest of the dinosaur looked like?
Even though we only had the skull, we did want to attach that head to the rest of the body for the artwork that is being used to publicize this find. The body plan of early horned dinosaurs such as Aquilops was fairly conservative–large head, long hindlimbs, shorter forelimbs, mostly bipedal, long tail. Decent skeletons are known for close relatives of Aquilops (such as Archaeoceratops) and quite fine skeletons are known for slightly more distant relatives (such as Psittacosaurus. Thus, although some details may be shown to be slightly off if a complete skeleton of Aquilops is found, we are pretty confident in the overall reconstruction.

Coming up…more behind the scenes tidbits
Update: Want to learn more? Check out this blog post from co-author Matt Wedel and a behind-the-scenes look at the artwork from Brian Engh.

Farke, A. A., W. D. Maxwell, R. L. Cifelli, and M. J. Wedel. 2014. A ceratopsian dinosaur from the Lower Cretaceous of western North America, and the biogeography of Neoceratopsia. PLOS ONE 9(12):e112055. [read the paper – open access!]

Category: Dinosaurs, Paleontology, PLOS ONE | Tagged , , , , | 14 Comments

Lungfish brains ain’t boring

I tend to think of fish brains as fairly unremarkable. Too simple relative to mammal brains, too un-dinosaur-y relative to dinosaur brains. Shark and perch brains get a brief nod in many comparative anatomy classes, but mostly to lament how “primitive” they are. Check ’em off the list, make a sketch, pass the quiz, and let’s see how fish brains evolved into something more interesting.

But, I only just learned that my callousness is more than a bit unwarranted. Researchers Alice Clement and Per Ahlberg, both from Uppsala University, Sweden, last week published a fascinating look at the reconstructed brain of a 380 million year old lungfish from Australia, Rhinodipterus. In conjunction with previously published work, a fascinatingly complex picture of lungfish brain evolution emerges.

Lungfish are particularly interesting to study due to their long fossil record–over 400 million years–as well as their key position within vertebrate evolution. Today, there are three main lungfish genera–Neoceratodus (the Australian lungfish), Lepidosiren (South American lungfish), and Protopterus (African lungfish). Only Protopterus has more than one species. Lungfish as a group are probably the fish most closely related to limbed vertebrates (tetrapods, including salamanders, turkeys, and humans, to name a few), and thus are an important reference point for understanding tetrapod evolution. 

The modern African lungfish Protopterus, probably even less tasty than it sounds. Image in the public domain, modified from Ray 1908.

The modern African lungfish Protopterus, cursed with a mostly cartilaginous cranium. Image in the public domain, modified from Ray 1908.

The problems with studying lungfish brains, though, really occupy two levels. The first is that brains don’t generally fossilize well–so, paleontologists have to rely on a “cheat code” to view the brains in extinct animals. Brains are encased in brain cases, a skull structure that often preserves at least the basic contours of the brain. Use a CT scanner to look inside the braincase, make a spinning digital model of the brain. But…the braincase is mostly cartilaginous in modern lungfish as well as many fossil species. Thus, even the basics of brain anatomy are essentially unknowable for much of lungfish evolution.

Thankfully, many early lungfish did have bony skulls. Nonetheless, many of the known fossils were crushed, incomplete, or incompletely studied. We are fortunate to have the fossil resources of the Gogo Formation, a 380 million year old set of rocks that preserves the remains of a marine reef. The specimens from here are spectacular (including an embryonic fish still connected to its umbilical cord), uncrushed, and beautifully freed from their rocky cradles using advanced preparation techniques. One of these fossils included a partial skeleton of the lungfish Rhinodipterus kimberleyensis. The braincase was CT scanned, and then a digital model of the inside contours was created to approximate the brain. This digital model, in turn, was then compared with published data from a few living and a fossil lungfish.

The ancient lungfish Dipterus, a close relative of the Rhinodipterus studied by Clement & Ahlberg (2014). Image from Ray 1907, in public domain.

The ancient lungfish Dipterus, a close relative of the Rhinodipterus studied by Clement & Ahlberg (2014). Image from Ray 1907, in public domain.

One of the most striking findings is that the reconstructed brain of Rhinodipterus is more similar to that of Neoceratodus, the modern Australian lungfish (picture at end of post), rather than that of the other modern lungfish (i.e., those from Africa and South America, Protopterus and Lepidosiren). Because Neoceratodus and the ancient lungfish Rhinodipterus share this “primitive” shape, Clement and Ahlberg hypothesized that the brain shape of other modern lungfish probably evolved as a unique evolutionary innovation. Other researchers have noted that the brains of today’s amphibians share some similarities with those of Protopterus and Lepidosiren. Looking at the entire evolutionary tree, it is now apparent that this was simply convergent evolution.

Clement and Ahlberg also looked into what brain says about function and behavior. They note that lungfish probably developed an enhanced sense of smell through their evolution, based on changes in the size and shape of the part of the brain associated with olfaction. Some differences in the inner ear–which is related to sensing changes in body position, movement, as well as sound–are also apparent across species, but the specific implications of these differences are a little hazier.

Digital endocast and interpretive drawing of the endocast from Rhinodipterus. The front of the brain is on the right, and the back (spinal cord) is at the left. Modified from Clement & Ahlberg 2014, CC-BY.

Digital endocast and interpretive drawing of the endocast from Rhinodipterus. The front of the brain is on the right, and the back (spinal cord) is at the left. The inner ear region is shown in orange, the hindbrain (including base of the spinal cord) in yellow, the midbrain in blue, and the forebrain in green and red. Modified from Clement & Ahlberg 2014, CC-BY.

Lungfish brains are surprisingly interesting! My congratulations to the authors on producing a very accessible piece of work. If a dinosaur paleontologist can understand it, that’s an achievement! Yet, even with this new study, there is so much more to learn. Hopefully studies of other well-preserved specimens will provide additional information on the noggins of these fascinating animals.

The modern Australian lungfish Neoceratodus. Public domain, modified from Flower 1898.

The modern Australian lungfish Neoceratodus. Public domain, modified from Flower 1898.

Clement AM, Ahlberg PE (2014) The first virtual cranial endocast of a lungfish (Sarcopterygii: Dipnoi). PLOS ONE 9(11): e113898. doi:10.1371/journal.pone.0113898

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Category: Fish, Open Access, Paleontology, PLOS ONE, Zoology | Tagged , , , , | 2 Comments