Author: Shaena Montanari

All Creatures Great and Small: Small Mammals and Conservation Paleobiology

Small mammals, at times, don’t seem very interesting or informative (like when there is a rat in your apartment and you just want it out.) A lot of paleontologists are keen on studying enormous carnivorous beasts like dinosaurs and sabre-toothed cats and are not often thinking about small, adorable (at least I think so) rodents. Fortunately for us, some people love all creatures, great and small. Ancient and modern small mammal communities are probably the best indicators of how  climate change will affect diversity, extinction, and speciation of vertebrates as a whole. They are often the base of food webs and vital to the survival of ecosystems. We were recently discussing how paleontology is relevant, and I would say these fossils are some of the most important resources we have as paleontologists interested in researching the future of global biodiversity in the face of warming temperatures.

A paper I read recently by Prost et al. 2013 in Global Change Biology serves as an excellent reminder of the dangers facing small mammal communities in a warming world. They utilized both ancient and modern data to help understand the future of both the narrow-skulled vole and collared lemmings. Polar regions are particularly interesting to study because they exceed tropical and temperate regions in warming. They used both ancient DNA and ecological niche modeling to look at changes in populations and biogeography since the Last Glacial Maximum, and then used this information to project into the future potential issue these vital species may have.

A friendly vole (Wikimedia Commons)

Interestingly, while both are small mammals that superficially occupy similar niches, they responded differently after the Last Glacial Maximum. The collared-lemming had a distinct range decrease, while the narrow-skulled voles were only minimally impacted. Also fascinating is that there is a strong correlation between extent of suitable habitat for narrow-skulled voles and their ancient genetic diversity. These animals are at the bottom of the food chain, and their survival can be integral to the entire artic and boreal forest ecosystem.

Population sizes in the two species (collared lemming in green, narrow-skulled vole in purple, oxygen isotope values  of ice core on the bottom) reacted differently after last glacial maximum. Collared lemmings clearly had a more severe population decrease than narrow-skulled voles. (Figure 2, Prost et al. 2013).

Population sizes in the two species (collared lemming in green, narrow-skulled vole in purple, oxygen isotope values of ice core on the bottom) reacted differently after last glacial maximum. Collared lemmings clearly had a more severe population decrease than narrow-skulled voles.       (Figure 2, Prost et al. 2013).

Another researcher who does stellar work on climate change and small mammal communities is Rebecca Terry. I greatly admire the importance and interdisciplinary nature of her modern and paleo-ecological work. The bulk of her work to this point has been analyzing small mammal bones in caves form the Great Basin region of the western United States. In a 2011 paper, Terry et al. analyze cave data from the last 7500 years to see how this rodent community responded to past climate change. The skeletal remains in these caves are predator-derived, meaning they are mostly owl and raptor regurgitate (pellets). These preserve the hard parts from prey and represent a solid composite signal of long term demographic trends.

Owl pellets contain bone and hair from prey (Wikimedia Commons)

The results clearly indicate a rather unexpected trend.  Rodents with diets adapted to plant fodder had a marked decline during dry periods, while rodents that primarily ate seeds dominated the faunal assemblage. Climate models show the Great Basin will warm considerably over the coming decades, so this sort of detailed information obtained from paleocommunities can help us conserve populations that are apparently vulnerable to these climate shifts.

I think these types of studies are so important to point out because they illustrate that our fossil record can be robust and useful for conservation- this has brought about the relatively new subfield ‘conservation paleobiology’ where we use paleo-information to inform modern conservation. Most of these studies are also quite interdisciplinary, using ancient DNA, niche modeling, stable isotope sampling, etc. Robust, all-inclusive sampling is needed to best understand the information locked in these fossils. Although big dinosaur fossils are cool, those finds are often sparse, and can’t tell us the useful, nitty-gritty details of community response to climate change.

Let this be a lesson to you future paleontologists, don’t ignore the little guys!

 

References:

Prost, S., Guralnick, R. P., Waltari, E., Fedorov, V. B., Kuzmina, E., Smirnov, N., van Kolfschoten, T., Hofreiter, M. and Vrieling, K. (2013), Losing ground: past history and future fate of Arctic small mammals in a changing climate. Global Change Biology. doi: 10.1111/gcb.12157

Terry, R. C., Li, C. and Hadly, E. A. (2011), Predicting small-mammal responses to climatic warming: autecology, geographic range, and the Holocene fossil record. Global Change Biology, 17: 3019–3034. doi: 10.1111/j.1365-2486.2011.02438.x

Category: Paleontology | Tagged , , | 1 Comment

Fossil Egg-cellence

I’m usually thinking about eggs. Not chocolate eggs (well, maybe this time of year), but fossil eggs. I am really interested in fossil eggs and what they tell us about behavior, but also the environments they were laid in. I have written before about stable isotopes, which can be used in egg and eggshell studies, but I will begin more generally about fossilized eggs and why so many paleontologists are keen to crack their mysteries (see what I did there?)

Reptile and bird eggs are composed in a similar basic fashion. The egg consists of yolk, surrounded by albumen, which is contained in an organic shell membrane all held in by a crystalline shell on the outside. The shell is made of calcite crystals in differing arrangements. I will mostly talk about rigid bird and dinosaur eggs because that is what fossilizes the best, but soft, leathery reptile eggs have been known to fossilize too (Hou et al. 2010). Bird eggshells (and fossilized non-avian dinosaur eggshells) are composed of columnar calcite crystals with an organic matrix of collagen fibers. The inner surface of the calcite shell has radiating cones (called mammillae) that are anchored at their tip to a thin organic membrane that encases the yolk and albumen.

General egg and eggshell microstructure diagram. (Photo credit: Shaena Montanari)

General egg and eggshell microstructure diagram. (Photo credit: Shaena Montanari)

Eggshell pores are present along calcite crystal boundaries that provide a mechanism for gas exchange while the eggs are incubating. The sizes of these pores can help us understand paleoenvironments and behavior.  For example, a 2008 study of fossil egg porosity by Jackson et al. indicates sauropods did not fully bury their eggs, which gives us a behavioral inference we never would have known before.

Fossilized bird and non-avian dinosaur eggs come in all shapes and sizes, from big round soccer ball-like sauropod eggs, to elongated ornamented oviraptorid eggs, to tiny fossil bird eggs that are like robin’s eggs. Most of the time you will find eggshell fragments in areas where fossilized eggs can be found, but if you are lucky you can find whole eggs, or even whole clutches. Most famously a specimen of Citipati osmoslkae was found brooding atop a nest of eggs in Ukhaa Tolgod, Mongolia, which helped us learn how dinosaur parents cared for their nests (Varricchio et al. 2008).

Nest with brooding Citipati at the American Museum of Natural History

Nest with brooding Citipati at the American Museum of Natural History (Photo Credit: Wikipedia)

Since eggshells fossilize well and are made of calcite, they can be used for geochemical analyses and paleoenvironmental reconstruction in the same way fossilized tooth enamel can be. Fossil ratite bird eggshells have proved most useful for these sorts of analysis due to the fact they are robust and are present in the fossil record from at least the Neogene to present. Both δ18O and δ13C of extinct elephant bird Aepyornis indicate it ate primarily C3 vegetation in the Holocene landscape of Madagascar, and also had a δ18O less influenced by evaporation than modern ostriches (Clarke et al. 2006). This allows us to better understand potential environmental mechanisms that could have caused the extinction of this species.

Aepyornis egg, with skeleton for size comparison. Big egg! (Photo credit: Wikipedia)

Aepyornis egg, with skeleton for size comparison. Big egg for a big bird! (Photo credit: Wikipedia)

Carbon isotopic composition of Adélie penguin (Pygocelis adeliae) eggshells illustrated a recent shift to lower trophic level prey in the last 200 years when compared with the previous 38,000 years (Emslie and Patterson 2007). For a small plug of some of my own dissertation work, dinosaur eggshells from Late Cretaceous Gobi Desert localities indicate clear variation in the paleoenvironments within one region during the same time slice (Montanari et al. 2013). These are just a few examples of how geochemistry can be used to understand ancient environments in great detail using just fossilized eggshell as a proxy, and there are many more excellent studies in the literature.

This is just a small seasonal introduction on something near and dear to me, so I hope you’ve enjoyed it and decided to forgo the Cadbury mini eggs this season for a solid chocolate Citipati one (can someone make me one of those actually?)

References

Clarke, SJ, GH Miller, ML Fogel, AR Chivas, CV Murray-Wallace. 2006. The amino acid and stable isotope biogeochemistry of elephant bird (Aepyornis) eggshells from Southern Madagascar. Quaternary Science Reviews 25 (17-18): 2343-2356.

Emslie, SD, WP Patterson. 2007. Abrupt recent shift in δ13C and δ15N values in Adélie penguin eggshell in Antarctica. Proceedings of the National Academy of Sciences 104 (28): 11666.

Hou, LH, PP Li, DT Ksepka, KQ Gao, MA Norell. 2010. Implications of flexible-shelled eggs in a cretaceous choristoderan reptile. Proceedings of the Royal Society B: Biological Sciences 277 (1685): 1235-1239.

Jackson, FD, DJ Varricchio, RA Jackson, B Vila, LM Chiappe 2008. Comparison of water vapor conductance in a titanosaur egg from the Upper Cretaceous of Argentina and a Megaloolithus siruguei egg from Spain. Paleobiology, 34(2), 229-246.

Montanari, S, P Higgins, MA Norell 2013. Dinosaur eggshell and tooth enamel geochemistry as an indicator of Mongolian Late Cretaceous paleoenvironments. Palaeogeography, Palaeoclimatology, Palaeoecology. 370, 158-166.

Varricchio, DJ, Moore, JR, Erickson, GM, Norell, MA, Jackson, FD,  Borkowski, JJ 2008. Avian paternal care had dinosaur origin. Science 322(5909), 1826-1828.

 

 

 

 

Category: Paleontology, Review | 6 Comments

Paleoecology and Poop, a Perfect Pair

It’s time to stop feeling sheepish and discuss poop. That’s right. You may not know this, but both modern and fossil poop can tell us so much information about biology, ecology, and environments that I think we need to talk about it. Instead of saying poop one million times in this entry, I will use the more official terms us scientists use: fossil poop is called a coprolite, while modern (fresh) samples are typically called scats. Feel a little less embarrassed now?

You may be wondering how interesting a coprolite can be. After all, fossilized excrement may look funny but it surely cannot be useful, right? Well just two weeks ago in PLOS ONE we saw that a 270 million year old shark coprolite contains remains of tapeworm egg casings, which is the earliest example of vertebrate intestinal parasites (Dentzien-Dias et al. 2013). Also, fossil freshwater bivalve shells were discovered in vertebrate coprolites from the Karoo Basin in South Africa, making them the first record of any freshwater bivalve in the Early Triassic (Yates et al. 2012).

Tapeworm eggs in a shark coprolite. From Dentzien-Dias et al. 2013

More traditionally though, coprolites are used to glean ecological information relating to the animal it came from and the environment it lived in. Knowledge about the diets of extinct animals can give us an indication of past vegetation structures and help us understand how climate change can alter landscapes and food webs. Researchers out of New Zealand were able to use extinct moa coprolites for radiocarbon dating and ancient DNA analysis (Wood et al. 2012). Moa were giant herbivorous birds (up to 250 kg) that went extinct shortly after the arrival of humans on the island. Moa coprolites can give us direct evidence of moa diet, and therefore the vegetation structure of their habitat, before the arrival of humans.

Moa coprolites sampled from Wood et al. 2012

Pollen, along with DNA of both the moa and the plant remains in the coprolites were examined. 67 species of plants were identified in the coprolites, indicating the moa was a generalist browser ~6,500 BP.

In addition to diets, coprolites can also be used to obtain ancient genomes from extinct species, such as cave hyenas (Bon et al. 2012) and the first Americans (Jenkins et al. 2012). Under the right conditions, DNA will be preserved in coprolites and provide previously unknown information about genetic diversity of extinct populations and species.

Perhaps most importantly, coprolites can have a very important place in conservation paleobiology. Animal-plant (or any prey) interactions are often not preserved in the fossil record, and things like coprolites are the only record of these interactions. Conservation scientists want to know what these relationships were like before human colonization in many areas, and this is a useful proxy to determine the “natural state” of animal-environment interactions. Wood et al. 2012 describes a pollen analysis of a coprolite from a kakapo- a rare flightless parrot endemic to New Zealand. Evidence from the coprolite shows they used to feed on a cryptic root parasite, but now the ranges of these two species do not overlap, which can indicate a shifting position of the kakapo in the larger food web. Evidence from coprolites will not only help us understand biology of animals that was previously unknown, but also will allow us to see a snapshot in time of ancient environments, and this helps us learn more about what we should try and conserve. Looks like poop science might be more useful than you thought!

 

References:

Bon C, Berthonaud V, Maksud F, Labadie K, Poulain J, Artiguenave F, Wincker P, Aury JM, Elalouf JM. (2012) Coprolites as a source of information on the genome and diet of the cave hyena. Proceedings of the Royal Society B: Biological Sciences 279, (1739) 2825-2830.

Dentzien-Dias PC, Poinar G Jr, de Figueiredo AEQ, Pacheco ACL, Horn BLD, et al. (2013) Tapeworm Eggs in a 270 Million-Year-Old Shark Coprolite. PLoS ONE 8(1): e55007. doi:10.1371/journal.pone.0055007

Jenkins JL, et al. (2012) Clovis Age Western Stemmed Projectile Points and Human Coprolites at the Paisley Caves. Science 337 (6091), 223-228.

Wood, J. R., Wilmshurst, J. M., Worthy, T. H., Holzapfel, A. S. and Cooper, A. (2012), A Lost Link between a Flightless Parrot and a Parasitic Plant and the Potential Role of Coprolites in Conservation Paleobiology. Conservation Biology, 26: 1091–1099. doi: 10.1111/j.1523-1739.2012.01931.x

Wood JR, Wilmshurst JM, Wagstaff SJ, Worthy TH, Rawlence NJ, et al. (2012) High-Resolution Coproecology: Using Coprolites to Reconstruct the Habits and Habitats of New Zealand’s Extinct Upland Moa (Megalapteryx didinus). PLoS ONE 7(6): e40025. doi:10.1371/journal.pone.0040025

Yates AM, Neumann FH, Hancox PJ (2012) The Earliest Post-Paleozoic Freshwater Bivalves Preserved in Coprolites from the Karoo Basin, South Africa. PLoS ONE 7(2): e30228. doi:10.1371/journal.pone.0030228

 

Category: Paleontology | Tagged | 1 Comment

So You Wanna Be a Paleoecologist? Part II

Paleoecology, Paleodiets, and Paleobiology

In my last entry, I explained the basics of stable isotope geochemistry for paleoecology. Now that we have covered what isotopes are and how they work, you may be wondering: what can we use them for in vertebrate paleontology? Luckily, there are loads of interesting questions that can and have been answered using stable isotope geochemistry and vertebrate fossils. I’m going to talk about a few recent papers that exemplify how great stable isotopes are for paleoecologists who are interested in vertebrates, but remember there is an enormous body of work out there for you to check out!

Ancient Food Webs

In modern ecosystems, we frequently examine food webs and dietary habits of apex predators to learn more about how animal communities interact. We also need to know this information for conservation purposes. But how have food webs and dietary niches changed over millions of years? Stable isotopes help us tease apart this complex question. In Domingo et al. (2013), an abundant fossil mammal assemblage from the Late Miocene of Spain was examined to better understand the resource partioning and habitat of extinct carnivorous mammals.

The carbon isotope values from the enamel of all taxa sampled. Carbon isotope values below -10 per mil generally reflect C3 dominated ecosystem. (Click for larger image) From Domingo et al. 2013

The δ13C values of the herbivores indicated this environment was mostly a pure C3 environment, dominated by wooded areas. There were statistically significant dietary differences between two of the sabre-toothed cats when compared with the amphicyonid, indicating dietary niche partioning between top predators. Examining a rich diversity of fossils in one ecosystem has allowed for a food web to be established in this region for the Late Miocene, which would not be possible without stable isotope geochemistry.

Paleodiets and Paleobiology

Stable isotopes are useful when we have enigmatic fossil taxa that have ambiguous morphologies. We often want to know: what did these animals eat? Sometimes, dental morphology cannot tell us everything we want to know about the paleodiets of a mysterious fossil taxon.

Paranthropus boisei is an ancient hominin that lived around 2 million years ago in East Africa. It possessed dental characteristics, such as low-cusped molars, which lead to the popular opinion that P. boisei ate mostly hard nuts and seeds. But, as Cerling et al. (2011) showed, carbon isotopes illustrated P. boisei actually ate mostly C4 grasses and shrubs, more than any other hominin ever studied using this method.

Carbon and oxygen isotope values for P. boisei and other vertebrates in East Africa. P. boisei has a similar to diet to hippos and equids in the area. (Click for larger image) From Cerling et al. 2011.

Stables isotopes can also elucidate the paleodiets of dinosaurs. Spinosaurs were a type of theropod dinosaur with very odd dentition that was quite crocodilian. Their conical teeth have often been thought to be a specialization for piscivory, but this is difficult to prove. By utilizing oxygen isotopes, Amiot et al. (2010) used specimens of spinosaurs from all around the world and showed their oxygen isotope composition is closer to co-occuring crocodiles and turtles than terrestrial theropods. This leads them to conclude spinosaurs may indeed have spent a large portion of their life foraging for food in aquatic environments.

These are just a few examples of how stable isotopes can be used in vertebrate paleontology to tell us more about ecology, biology, and diets of long extinct animals. Although there is a large body of work on this subject, there are still many regions of the world that remain relatively unsampled in this manner. If you want to use stable isotopes at your own field site or on a specimen you have, contact a stable isotope geochemist near you, they are always willing to help!

References 

Amiot R., et al. 2010. Oxygen isotope evidence for semi-aquatic habits among spinosaurid theropods. Geology 38, 139–142.

Cerling,T., et al. 2011. Diet of Paranthropus boisei in the early Pleistocene of East Africa. PNAS 108, (23) 9337-9341.

Domingo, M.S. 2013. Resource partioning among top predators in a Miocene food web. Proc. R. Soc. B. 280, (1750).

 

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So You Wanna Be a Paleoecologist? Part 1

For the better part of the past three decades, stable isotope geochemistry has become an increasingly common tool vertebrate paleontologists use to find out more about the biology and ecology of extinct organisms. The diet and ecology of an animal can often remain elusive when fossils are merely examined morphologically. Luckily, stable isotopes can tell us specific characteristics about what an animal is eating and the environments it lives in during its lifetime. Despite the fact this method is commonly used these days, there is a lot of background and jargon associated with it that many paleontologists have not been exposed to. In my two part series I am going to describe the foundations of these methods as they apply to paleontology, and then in part two I will highlight some recent work that illustrates how geochemical methods should be seen as an indispensible tool for paleontologists. Hopefully this brief description will help the method of stable isotope ecology become more accessible to all types of paleontologists!

What is an isotope?

Some elements have multiple stable forms with a different number of neutrons in the nucleus, known as isotopes. For example, a normal carbon atom has 6 protons and 6 neutrons in its nucleus, for an atomic weight of 12, but there is also a less abundant form of carbon that exists with an atomic weight of 13, meaning there are 6 protons and 7 neutrons in its nucleus. Heavier stable isotopes tend to be more rare on earth. The differing physical properties of isotopes of the same element lead to a predictable and often times systematic variation in the ratio of heavy to light isotopes in organic materials.

The two stable isotopes of carbon. Credit: S. Montanari (2012).

 

How are they measured?

Stable isotope ratios are measured using a isotope ratio mass spectrometer (IRMS). The basic mass spectrometer design has not been greatly modified since its invention by Alfred Nier in the 1940s while working on the Manhattan Project, hence the design is still called “Nier-type” today. A Nier-type IRMS is constructed of a source, flight tube, magnet, and collector cups. At the source, the sample gas is ionized and then accelerated into the flight tube. A giant magnet deflects the sample based on mass into collection cups, known as Faraday collectors. This collection creates an electrical current that is measured by a connected computer and converted into an isotope ratio. Samples are measured relative to a standard in “per mil” notation. Unknown samples are measured against known standards, which in the case of carbonates is Vienna Pee Dee Belemnite or V-PBD.

A simple schematic of an isotope ratio mass spectrometer. From Wikimedia Commons/USGS

Isotopes in the environment

As bones, teeth, and eggshells mineralize, stable isotopic signatures from the water and food an organism is consuming will be locked in and recorded. Once mineralized, this signature will not change over the life of an animal. When we find a fossil, it is possible to measure these ratios using an IRMS, as previously mentioned, but what do they tell us about the environment specifically?

Perhaps on of the most useful stable isotope systems to understand for paleoecologists is the pattern of carbon isotopic fractionation in plants.  Due to a physical isotope fractionation, C3 type plants preferentially fix 12C bearing Co2 during photosynthesis, resulting in δ13C values that are strongly discriminated from the δ13C of the atmosphere (currently ~-7‰), ranging between -35 and -25‰ depending on climate and ecology. In contrast, C4 plants have δ13C values worldwide between -15 and -11‰. C3 and C4 plants tend to grow under different climate regimes, and this clear delineation in δ13C values of these plants provides a way to track changes in ecosystems and understand dynamics of environments in deep time.

Similar predictable fractionations occur with water in the environment and water in the body of an organism, which allows oxygen isotope ratios, δ18O, to be useful for reconstructing the type of water the organism was drinking in their environment, for example, if it was highly evaporated or not. Oxygen isotope ratios recorded in tooth enamel are related to the drinking water of the organism, which is obtained from the environment. The δ18O of environmental water is determined by the δ18O of precipitation, which in turn is determined by temperature, evaporation, and the source of the precipitation air mass (Dansgaard 1964). Lighter isotopes of oxygen evaporate while heavier ones condense, meaning the greater the distance between the ocean and the air mass, rain will be lighter because heavy isotopes rainout preferentially earlier in travel of the air mass. Enrichment of δ18O is greatest under arid, hot conditions. These systematic variations in the enrichment and fractionation of oxygen isotopes allows us to glean environmental information from the δ18O contained in fossil tooth enamel.

As you can see, there is a lot that can be described surrounding stable isotope ratios in fossils. I have only touched on carbon and oxygen, which are the two most commonly used in vertebrate paleontology isotopic studies, but I will be sure to highlight others in part two of this series where I will dive more into the applications of this method in recent case studies.

Additional reading:

Dansgaard, Willi. 1964. Stable isotopes in precipitation. Tellus 16 (4): 436-468.

Koch, Paul. 2007. Isotopic study of the biology of modern and fossil vertebrates. In Stable Isotopes in Ecology and Environmental Science. 2nd ed. Boston: Blackwell Publishing.

Sulzman, E W. 2007. Stable isotope chemistry and measurement: A primer. Stable Isotopes in Ecology and Environmental Science 1-21.

Category: Background, Paleontology | Tagged , , , , | 2 Comments

Bird brains: what they can tell us about ecology and evolution

For my inaugural post here at The Integrative Paleontologists, I am going to discuss a recent paper in PLOS ONE that highlights some of the aspects I love most about being a comparative biologist.

Paleoecology is the area of paleontology I am most interested in–and now, many paleontologists are spending a significant portion of their time examining extant species in order to understand more about the features and signals found in the fossil record.  Fossils are often fascinating morphologically but information such as behavior and ecology can be difficult to access in long-dead specimens with no soft tissue preservation and of course, no live observations. We as paleontologists need to think of creative comparative methods that can breathe some life back into old bones.

In their recent paper, Adam Smith and Julia Clarke use high resolution CT scanning to look at a variety of structures in the endocranial region of a group of birds called Charadriiformes (plovers, sandpipers, gulls, terns, and their allies). Within charadriiforms, a wide variety of locomotor and feeding ecologies are represented­–ranging from auks, which are wing-propelled divers, to marsh sandpipers, which are terrestrial ground-foragers.

Razorbill, a type of auk. CC-BY.

Morphology preserved in the brain case of vertebrates can correspond to certain unique ecologies and life histories. Charadriiformes are a good group to test this on because of their diverse ecologies and well-known evolutionary relationships. I will highlight a few of their findings here:

  •  The “wulst”, also known as the sagittal eminence, is a structure in the brain of birds linked to sensory and visual perception. This structure can be reconstructed using a digital endocast. Interestingly, the only two terrestrially foraging species sampled possess a uniquely positioned wulst when compared to the other charadriiforms. On the other hand, both flightless and volant species possess similarly shaped wulsts so it may not be useful in predicting flight styles of birds.
  • The inner ear is comprised of a bony tube, known as a labyrinth. The characteristics of this labyrinth have been known to accurately predict how acrobatically an animal can move.  Although in this group of birds, it appears that labyrinth shape and structure is conserved, even between divers and non-divers.

    Cranial endocasts of four species in this study illustrating differences in endocranial morphology. Smith and Clarke 2012 (CC-BY)

  • Overall, it was shown that flightless wing-propelled divers have relatively smaller brains for their body masses and also smaller optic lobes than volant members of the same group. There was one species, the Black Skimmer (Rynchops niger) that was strikingly different from all of the others that were sampled. The Black Skimmer has, among other unique endocranial characteristics, an unusually large wulst. This seems to be related to the Black Skimmer’s unique tactile feeding ecology– it feeds at the surface of the water by skimming the surface with its lower jaw (video from YouTube here).

Learning the details of these endocranial morphological correlates to behavior and ecology is invaluable to understanding the endocranial characters we see in fossils. Charadriiforms have a robust fossil record; so fossil specimens from this group can be CT scanned in order to enlighten us as to potential feeding and behavioral traits now that the significance of these morphological features are known. I think increasingly paleontologists will turn to studying extant species with new advanced technologies that we can also apply to our fossil specimens, allowing us to better grasp ecology in deep time. Expect to hear more on this topic from me in the future!

Citation:

Smith NA, Clarke JA (2012). Endocranial Anatomy of the Charadriiformes: Sensory System Variation and the Evolution of Wing-Propelled Diving. PLoS ONE 7(11): e49584. doi:10.1371/journal.pone.0049584

Category: Paleontology, PLOS ONE | Tagged , , , , | 1 Comment