Wednesday, June 26, 2013

Suizo Report -- The Third Dimension of Desert Herping

Howdy Herpers,                                                                                               24 June 2013

Typing Boy here has always thought that herping in the Sonoran Desert as being a two dimensional affair. The herps are either on the ground, or under it. But on occasion, a third additional dimension exists out there.

We'll let the pictures do the talking:

Image 1: This would make a great "Where's Waldo?" shot, but I can't handle all the replies that come with those. But before you scroll down to see the other images, give this first one you best shot. There are 2 snakes in this image, can you find them?

Image 2: Snake number 1

Image 3: Snake number 2

Snake number 1 is Tiger Rattlesnake, CT #13, a female. Snake number 2 is a Lyresnake, poised about 1 meter above CT13. I probably would not have noticed the lyresnake, but it happened to be right where I wanted to put my thermometer. Surprise!

Image 4: Our big male Black-tailed Rattlesnake, CM#12 "Jerry" going arboreal on us. We kept going back to watch his progress. Over the course of the night, he only moved about 2 meters, and seemed to be set up to nail whatever would land in the branch in front of him.Image by Marty Feldner.

Image 5 and 6: Our young male CM16, as found.

Image 7: Always a nice sight! It's about the best thing we can hope for on a June morning. C'mon Monsoons!

Best to all, roger

The decline of cantils and systematics

Agkistrodon cf bilineatus. JCM
The idea that a single species could occur in several different forms, varieties, or subspecies can be traced to Ernst Mayer's book Systematics and the Origin of Species. The idea advanced evolutionary thought but also added confusion to the concept of species and concealed the concept of cryptic species. Molecular analysis often supports polytypic species species as complexes of cryptic species suggesting squamate diversity is significantly greater than commonly assumed.

In a new paper Porras and colleagues (2013) describe the  cantil (Agkistrodon bilineatus) as a polytypic species of North American pitviper with a variably fragmented distribution extending from extreme southwestern Chihuahua and southern Sonora, Mexico, to northwestern Costa Rica, on the Pacific versant, and parts of the Yucatan Peninsula, northern Belize, Guatemala, and extreme western Honduras on the Atlantic versant; the snake also occurs in Las Islas Marías, an archipelago of four islands located about 100 km west of the state of Nayarit, Mexico .  The cantil usuall inhabits dry forest, deciduous forest, thorn scrub, and savanna, primarily areas of low relief that have been exploited heavily by agriculture and areas where this species has become a rare snake; the species elevational range extends from near sea level to about 1,500 m . Along the Pacific coast of Mesoamerica, tropical dry forests were reported as the most endangered of the major tropical ecosystems, with only 0.09% of that region afforded official conservation status . Based on multiple lines of evidence, a phylogeographic analysis of the cantils A. b. taylori was raised to the rank of full species, emphasizing that the loss of forested areas in the habitat of this species underscored the need for its conservation. More recently,  an extensive conservation assessment for the entire Mesoamerican herpetofauna, in which numerous authorities provided information on the status of cantils. Although the methodological approaches of these authors varied, it was clear from the outcome that the conservation status of A. bilineatus showed dramatic differences when analyzed on a country by country or regional basis, Porras et al. note several lines of evidence suggest that numerous populations of cantils (Agkistrodon bilineatus, A. taylori) are in rapid decline. They examined the IUCN conservation status for A. bilineatus, assessed for the entire range of the species, as well as the Environmental Vulnerability Scores (EVS) provided for certain countries along its distribution. Because of pronounced disparities in these conservation assessments and notable phenotypic differences that coincide with the geographic distribution of certain cantil populations. They conducted a taxonomic reassessment of the common cantil, Agkistrodon bilineatus (Günther 1863), to determine if the recognized subspecies of A. bilineatus merit specific status. Based on their morphological assessment, biogeographical evidence, and the results of previous DNA-based studies, we elevate the three previously recognized subspecies of A. bilineatus to full species (A. bilineatus, A. russeolus, and A. howardgloydi).

The article can be found on-line.

Porras, LW, Wilson LD, Schuett GW, Reiserer RR. 2013. A taxonomic reevaluation and conservation assessment of  the common cantil, Agkistrodon bilineatus (Squamata: Viperidae): a race against time. Amphibian & Reptile Conservation 7:48-73.

Sunday, June 23, 2013

Molecular phylogeny of a possibly extinct snake

Coluber cursor Lacépède, 1789, was described from Martinique and has been placed in the genera Herpetodryas, Dromicus, and Liophis  at various points in time. But molecular work suggests the snake is one of 41 species in the now greatly expanded genus Erythrolamprus. Erythrolamprus cursor.  Jowers and colleagues (2013) failed to find the snake in a search of its last known islet, Dianond Rock, literally a large rock about 5.8 hectares, 2 km off the coast of Martinique. Diamond Rock was the source of the last two specimens collected in 1964. Left with no alternative to sort out the snake's phylogenetic relationships, the authors extracted DNA from old museum specimens. They found  a sister relationship between E. cursor and E. juliae (another Antillean species known from Dominica, Guadeloupe, and Mairie-Galante). All sequences recovered had the same haplotype and the level of divergence between E. cursor and E. juliae, from the nearby island of Dominica, was lower than between other intraspecific distances within other Erythrolamprus. Furthermore, phylogenetic analyses confirm that these two species are sister taxa and share most recent common ancestry an estimated 2 million years ago. Diamond Rock lacks a frog population, and while E. cursor's close relatives seem to feed mostly on anurans, the Black Rock population must have been feeding on something else. There are four species of lizards living on the islet, and they seem to be likely prey, given that related species occasionally take lizards as well as frogs. The authors emphasize the urgent need to conduct an exhaustive survey on the supposed last population of E. cursor at Diamond Rock to establish the survival of this species there, and to understand how it may have adapted to such an ecosystem, especially in the sympatry of several introduced rodent species.

Jowers MJ, Caut S, Garcia-Mudarra JL, Alasaad S, Ineich I. 2013. Molecular Phylogenetics of the Possibly Extinct Martinique Ground Snake. Herpetologica 69: 227-236.

Tuesday, June 18, 2013

Psuedoboini diet & microhabitat

A Psuedoboa neuwiedii that contained the remains of an Ameiva atrigularis. JCM
Recently, I found a large Pseudoboa neuwiedii lying in vegetation about 50 cm above the ground with its head down. It was most certainly waiting for prey to pass by. We collected the snake, and when removed from the bag the snake regurgitated a partially digested Ameiva atrigularis.

Diet and microhabitat variation within a clade of snakes may provide insight into how the group evolved. Alencar and colleagues (2013) look at the Neotropical Pseudoboini, a clade distributed from Mexico to Argentina and thought to be monophyletic. Psuedoboini consists of  about 47 species in the genera Boiruna, Clelia, Drepanoides, Mussurana, Oxyrhopus, Paraphimophis, Phimophis, Pseudoboa, Rhachidelus, Rodriguesophis and Siphlophis. 

The authors found the diet of pseudoboine snakes consists mainly of lizards and small mammals, as previously reported in the literature. They found Oxyrhopus may show a shift in diet from ectotherm prey as juvenilies to endothermic prey as adults. Ophiophagy was found to be more important than previously thought. The four species of Siphlophis were found to specialize in lizards. Drepanoides anomalus specializes in lizard eggs. Pseudoboines have diverse feeding habits with most of the diversification occurring in terminal taxa. And, they suggest in the evolutionary history of diet it seems that the ancestors of the diet specialists were either specialists in the same type of prey or generalists.

Among pseudoboines, Drepanoides anomalus and the four species of Siphlophis are semi-arboreal. The authors suggest that S. longicaudatus may also use the vegetation based on its slender body and long tail data is lacking. Surprisingly, Clelia clelia, Pseudoboa neuwiedii, P. nigra, and Oxyrhopus vanidicus also use the vegetation although to a lesser degree. The evolution of arboreality in Siphlophis and in Drepanoides anomalus, species known to inhabit primarily forested habitats, supports the hypothesis that more arboreal snakes tend to evolve more frequently in forests.

Alencar LRV, Gaiarsa MP, Martins M. 2013. The Evolution of Diet and Microhabitat use in Pseudoboine Snakes. South American Journal of Herpetology 8:60-66.

Thursday, June 6, 2013

Evidence for reptiles filling mammalian roles in the Paleogene greenhouse

Artist's rendition of Barbaturex morrisoni. Credit Angie Fox, Nebraska
State Museum of Natural History, University of Nebraska-Lincoln.
Some 40 million years before rock singer Jim Morrison's lyrics earned him the moniker "the Lizard King," an actual king lizard roamed the hot tropical forests of Southeast Asia, competing with mammals for food and other resources.
            A team of U.S. paleontologists, led by Jason Head of the University of Nebraska-Lincoln, describes fossils of the giant lizard from Myanmar this week in the scientific journal Proceedings of the Royal Society B. Their analysis shows that it is one of the biggest known lizards ever to have lived on land.
            The creature's scientific name is Barbaturex morrisoni -- which means "Lizard King," in honor of the aforementioned Doors singer.
            At almost six feet long and weighing upwards of 60 pounds, the lizard provides new and important clues on the evolution of plant-eating reptiles and their relationship to global climate and competition with mammals.
            In today's world, plant-eating lizards like iguanas and agamids are much smaller than large mammal herbivores. The largest lizards, like the giant, carnivorous Komodo dragon, are limited to islands that are light on mammal predators. It is not known, however, if lizards are limited in size by competition with mammals, or by temperatures of modern climates, Head said.
            But B. morrisoni lived in an ecosystem with a diversity of both herbivorous and carnivorous mammals during a warm age in Earth's history -- 36 to 40 million years ago -- when there was no ice at the poles and atmospheric carbon dioxide levels were very high. The creature was larger than most of the mammals with which it lived, suggesting that competition or predation by mammals did not restrict its evolution into a giant.
            "We think the warm climate during that period of time allowed the evolution of a large body size and the ability of plant-eating lizards to successfully compete in mammal faunas," Head said.
            "You can't fully understand the evolution of ecosystems in the modern world without looking at the ones that preceded them. We would've never known this by looking at lizards today. By going back in time using the fossil record, we can find unique information on the origin of modern ecosystems."
            Head worked with Patricia Holroyd of University of California, Berkeley, Gregg Gunnell of Duke University, and Russell Ciochon of the University of Iowa on identifying and analyzing B. morrisoni.
            It was a discovery millions of years and then a few extra decades in the making. Fossils of the giant lizard were discovered by Ciochon and colleagues in the 1970s in Myanmar, but were unstudied in the University of California Museum of Paleontology until a few years ago, when Head and Holroyd began looking into them.
            When Head first examined the fossils, he noticed the creature's bones were characteristic of a group of modern lizards that includes bearded dragons, chameleons and plant eaters like spiny-tailed lizards.
            "I thought, 'That's neat. Based on its teeth, it's a plant-eating lizard from a time period and a place from which we don't have a lot of information.' But when I started studying its modern relatives, I realized just how big this lizard was. It struck me that we had something here that was quite large -- and unique," said Head, an assistant professor of earth and atmospheric sciences at UNL and a curator in the University of Nebraska State Museum of Natural History's Division of Vertebrate Paleontology.
            He noticed another telltale sign -- ridges on the underside of the jaw that strongly suggested it supported soft tissues, much like the multicolored chin flaps and dewlaps that give some modern lizards a bearded appearance. The giant lizard's genus name, Barbaturex, means "bearded king."
            "I was listening to The Doors quite a bit during the research," Head said. "Some of their musical imagery includes reptiles and ancient places, and Jim Morrison was of course 'The Lizard King,' so it all kind of came together."
            Head said the discovery of B. morrisoni now leads to other big questions: For how long do these giant lizards persist in the fossil record? How far and wide did they disperse across the planet? What are the relationships of the evolution of reptile body sizes to changes in global temperature throughout history? And the obvious question -- does a warming climate mean giant reptiles will someday return?
            He said if we were to raise global temperatures at a natural pace and preserve natural, healthy habitats, we could end up with the evolution of giant lizards, turtles, snakes and crocodiles.
            "But we're changing the atmosphere so fast that the rate of climate change is probably faster than most biological systems can adapt to. So instead of seeing the growth and spread of giant reptiles, what you might see is extinction," he said.
            Meanwhile, the researchers will consider how the clues provided by B. morrisoni can be used to reconstruct global temperature over geologic time periods.
            "That becomes very important in modeling what temperature change will be like across the surface of the planet in the future," Head said. "And that, obviously, bears directly on our own health."

Hea JJ,  Gunnell GF,  Holroyd PA, Hutchison JH, Ciochon RL. 2013. Giant lizards occupied herbivorous mammalian ecospace during the Paleogene greenhouse in Southeast Asia. Proceedings of the Royal Society B: Biological Sciences, 280 (1763): 20130665 DOI: 10.1098/rspb.2013.0665

Tuesday, June 4, 2013

Oil palm plantations favor frog species of least concern

Species like Hylarana erythrea thrive in oil plam plantations while other species disappear.

Oil palm plantations in Malaysia are causing threatened forest frogs to disappear, paving the way for common species to move in on their turf, scientists have revealed.

The study, carried out by the Zoological Society of London (ZSL) describes how forests converted to palm oil plantations are causing threatened forest dwelling frogs to vanish, resulting in an overall loss of habitat that is important for the conservation of threatened frog species in the region.

Scientists travelled to Peninsular Malaysia where they spent two years studying communities of frog species in four oil palm plantations and two areas of adjacent forest. The paper is published in the journal Conservation Biology.

Aisyah Faruk, PhD student at ZSL's Institute of Zoology says: "The impact we observed is different from that observed previously for mammals and birds. Instead of reducing the number of species, oil palm affects amphibian communities by replacing habitat suitable for threatened species with habitat used by amphibian species that are not important for conservation. This more subtle effect is still equally devastating for the conservation of biodiversity in Malaysia."

Amphibians are the most threatened vertebrates in the world, with over 40% at risk of extinction. The peat swamp frog (Limnonectes malesianus) is just one of the declining species threatened due to deforestation. It inhabits shallow, gentle streams, swampy areas, and very flat forests, laying eggs in sandy streambeds. Scientists only found this species in forest areas, and if palm oil plantations continue to take over, the peat swamp frog, along with its forest home, could be a thing of the past.

ZSL's Dr. Trent Garner, a co-author on the paper, says: "Existing practices in managing oil palm are not accommodating the highly threatened forest frog species in Malaysia which urgently need saving."

The planting of oil palm plantations leads to the loss of natural forests and peat lands and plays havoc with ecosystems and biodiversity. ZSL, together with collaborators from Queen Mary University of London, Universiti Kebangsaan Malaysia and University of Malaya, continues to work closely with Malaysian palm oil producers in determining if simple modifications to agricultural practices may bring some of the forest species back into areas planted with oil palm and allow them to survive and reproduce in plantations.

Aisyah Faruk, Daicus Belabut, Norhayati Ahmad, Robert J. Knell, Trenton W. J. Garner.2013. Effects of Oil-Palm Plantations on Diversity of Tropical Anurans. Conservation Biology, 27 (3): 615 DOI: 10.1111/cobi.12062

Sunday, June 2, 2013

Why female loggerhead sea turtles always return to their natal beach

A Loggerhead Sea Turtle. Photo: V. Stiebens, GEOMAR
Marine turtles are among the most endangered species of the world ocean. For a better protection of these fascinating animals, scientists try to understand why turtles return to their birthplace in order to reproduce after rather long distance migrations. Using molecular tools applied to turtles from the Cape Verde islands, scientists from GEOMAR Helmholtz Centre for Ocean Research Kiel (Germany) found that males and females adopt different strategies: while females are very faithful to their island of birth, males appear less selective and mate at multiple locations. Furthermore, the study published now in the Proceedings of the Royal Society B: Biological Sciences demonstrates that females from different islands have different immune genes, suggesting that returning home to reproduce is linked to advantages in parasite resistance. This is the first evidence ever to explain why many migratory animals show this type of behavior.

Worldwide, over 15,000 species are threatened by extinction, and the loggerhead sea turtle is no exception. Once the mysteries surrounding some of the species behavior are resolved, more effective conservation programs can be developed to facilitate their protection. The case of the loggerhead sea turtle is particularly interesting: Why do they migrate for several thousands of kilometers to eventually come back to their place of birth for reproduction after roughly 25 years?

To address this question, a group of evolutionary biologists from GEOMAR Helmholtz Centre for Ocean Research Kiel focused on the world’s third largest nesting population of the loggerhead sea turtle which is found in the archipelago of Cape Verde. Despite the fact that the species is protected, the number of nesting turtles has been decreasing rapidly due to the slaughter of turtles for their meat, marine pollution, coastal development in nesting areas and fisheries by-catch. Hence, the loggerhead turtle has the “endangered” status on the Red List of Threatened Species (IUCN 2012).

The archipelago of Cape Verde is composed of numerous islands where turtles can be observed. In this study, GEOMAR scientists collected tiny skin samples from turtles on four different islands of the archipelago for analysis. Using multiple genetic tools, the scientists found that Cape Verdean female loggerheads not only return to Cape Verde to breed but also that they show a remarkably accurate philopatric (returning to reproduce at the place of birth) behavior of a couple tens of kilometers: “It was fascinating to demonstrate that most female turtles actually return to the exact island where they were born”, said lead author Victor Stiebens.

This outstanding behavior has some advantages for the turtles. The study found that a certain region in the turtle’s genome is responsible for fighting parasites and diseases, the so-called major histocompatibility complex. “Indeed, the study shows that turtles nesting at the most distant islands of the archipelago have different sets of these genes, providing the right genetic make-up to pass to the offspring to fight off the local parasite fauna present in that specific place”, explains senior author Dr. Christophe Eizaguirre.

At the same time, always returning to the same island may have detrimental effects for species with small population sizes since it may lead to mating with relatives, i.e. inbreeding. However, it was rather interesting that in this study, the scientists were able to show that males counteract this inbreeding risk by being less selective in choosing their mating places. “Males seem to look for females over large regions of the archipelago, whereas females are more faithful to their place of birth to mate” reports Victor Stiebens. “These gender-specific behaviors assure genetic transfer between the nesting islands but also the existence of genes needed in these local environments” says Dr. Eizaguirre.

The conclusions of the study show that returning home to reproduce gives individuals an additional advantage to fight off parasites and diseases, and may thus add a piece to the puzzle of the intriguing journey of marine turtles. “From a conservation perspective, the results suggest that it is very important to not lose any of the nesting colonies as each singular location provides important genetic adaptation for the survival of the entire population in the case of major biotic/abiotic changes in a globally changing environment”, says Dr. Eizaguirre.

V. A. Stiebens, S. E. Merino, C. Roder, F. J. J. Chain, P. L. M. Lee, C. Eizaguirre. 2013. Living on the edge: how philopatry maintains adaptive potential. Proceedings of the Royal Society B: Biological Sciences, 2013; 280 (1763): 20130305 DOI: 10.1098/rspb.2013.0305

Invasive treefrog changes calls of native frog

Cuban Treegrog, USGS
May 30, 2013 — Human-produced noises from sources such as traffic and trains can substantially impact animals, affecting their ability to communicate, hunt, or even survive. But can the noise made by another animal have the same detrimental effects? A new study presented at the 21st International Congress on Acoustics (ICA 2013) examines the calls made by an invasive species of tree frog and suggests the answer is yes

Ecologist Jennifer Tennessen, a graduate student at The Pennsylvania State University, and her colleagues recorded the calls of the Cuban tree frog (Osteopilus septentrionalis) -- an invasive species that had arrived in southern Florida by the 1930s and spread rapidly, eventually establishing populations throughout the southeastern United States. Tennessen and colleagues measured the effect of those calls on the acoustic behavior of two native species of tree frogs in southern Florida: green tree frogs, which have an acoustic signature that is similar to that of the Cubans, and pine woods tree frogs, whose song is different.

"We predicted that Cuban tree frog chorusing would interfere most with native tree frogs whose acoustic behaviors were similar," she said, "and that these would be the most likely candidates to modify their acoustic behavior to avoid interference."

During controlled playbacks of the chorus of the Cuban tree frogs, the researchers found, green tree frogs doubled their call rate -- the number of calls per minute. The call rate of pine woods tree frogs, in contrast, did not notably change. "By increasing their call rate, green tree frogs may be able to increase the likelihood that potential mates can detect them a midst the noise," Tennessen said. "This response, however, likely comes at the cost of requiring additional energy, which could be detrimental as it may divert energy away from other important functions like digestion and immune function."

Because they're essentially making more sound -- which makes them easier to spot -- green tree frogs may also be more vulnerable to predation, Tennessen said.

And the effects aren't just limited to the tree frogs. Adding the Cuban tree frog chorus to the "soundscape" of the ecosystem might use up valuable acoustic space, Tennessen said, "impairing the communication of a variety of different species -- from frogs and toads to birds and insects -- that rely on sound for survival and reproduction.

Saturday, June 1, 2013

Suzio Report: Some animals from the famous hill

Howdy Herpers,
We got our good photographers, and we got our bad photographers. When I say "bad photographers," there are 2 meanings. These are those who, like me, dumbly point the camera, squeeze the trigger, and pray that something good will somehow miraculously happen. (Most times, it doesn't.)

Then there are those "bad photographers" who are artists at their craft, but think that by getting a good image of something, they have just created the next Mona Lisa. In their minds, their work is priceless, and not meant to be shared. At least, not on a gratis basis.

I don't 100% blame these people. They have invested big bucks in their equipment, and countless hours developing their skills. But like them, we have invested big bucks at OUR craft as well. We sink 5 grand a year just in equipment alone, never mind gas money, or salary, or most importantly, beer.

So now, we lead good horses to water, they get their images, and we get nothing?  We step back so you can get your picture? Then, we get nothing? THAT'S WRONG!

And sometimes, these bad photographers even drink our beer in the process. That's heartless!
 From now on, camera dudes and dudesses, you take pictures, we want copies. Don't make us ask--ok? Just bring 'em on!

I'm pleased to report that on Saturday, 11 May, we were with "good photographers."  We speak of two visiting guests from Holland, Wouter Kok and Ferry van Stralen. With us this day was our stalwart field hand Marty Feldner, and the somewhat erstwhile Gordon Schuett and Ryan Sawby. We had our A game going for sure this day.

Other than the fact that we had good photographers with us, it was an ordinary day in paradise. Ryan did manage to find us a new Gila Monster. (Which proves that even a blind squirrel can find an acorn). To this herper, a new monster is always a day maker in its own right. But calling any day in the Suizos an "ordinary day" is a good thing. There is always a shot at seeing 14 different rattlesnakes in situ. Where will you do better than that on a regular basis?

It's time to just go with the images. All except the last 2 were taken by Ferry van Stralen. It's a thrill to see what a good photographer can do on an ordinary day. We'll skip the long stories, and let the images do the talking.

Best to all, roger

Lung ventilation & the evolution of the turtle shell

The skeleton of the South African reptile Eunotosaurus 
africanus fills a gap in the early evolution of turtles
 and their enigmatic shell. Photo Credit: Tyler Lyson.

Through careful study of an ancient ancestor of modern turtles, researchers now have a clearer picture of how the turtles' most unusual shell came to be. The findings, reported on May 30 in Current Biology, a Cell Press publication, help to fill a 30- to 55-million-year gap in the turtle fossil record through study of an extinct South African reptile known as Eunotosaurus.

"The turtle shell is a complex structure whose initial transformations started over 260 million years ago in the Permian period," says Tyler Lyson of Yale University and the Smithsonian. "Like other complex structures, the shell evolved over millions of years and was gradually modified into its present-day shape."

The turtle shell isn't really just one thing -- it is made up of approximately 50 bones. Turtles are the only animals that form a shell through the fusion of ribs and vertebrae. In all other animals, shells are formed from bony scales on the surface; they don't stick their bones on the outsides of their bodies.

"The reason, I think, that more animals don't form a shell." The reason, I think, that more animals don't form a shell via the broadening and eventually suturing together of the ribs is that the ribs of mammals and lizards are used to help ventilate the lungs," Lyson says. "If you incorporate your ribs into a protective shell, then you have to find a new way to breathe!" Turtles have done just that, with the help of a muscular sling.

Until recently, the oldest known fossil turtles, dating back about 215 million years, had fully developed shells, making it hard to see the sequence of evolutionary events that produced them. That changed in 2008 with the discovery of Chinese Odontochelys semitestacea, a reptile about 220 million years old, which had a fully developed plastron -- the belly side of the shell -- but only a partial carapace on its back.

Eunotosaurus takes the turtle and its shell back another 40 million years or so. It had nine broadened ribs found only in turtles. And like turtles, it lacked the intercostal muscles running between its ribs. But Eunotosaurus didn't have other features common to Odontochelys and turtles, including broad spines on their vertebrae.

Lyson says he and his colleagues now plan to investigate various other aspects of turtles' respiratory systems, which allow them to manage with their ribs locked up into a protective outer shell. "It is clear that this novel lung ventilation mechanism evolved in tandem with the origin of the turtle shell," he says.


Tyler R. Lyson, Gabe S. Bever, Torsten M. Scheyer, Allison Y. Hsiang, Jacques A. Gauthier. Evolutionary Origin of the Turtle Shell. Current Biology, 2013; DOI: 10.1016/j.cub.2013.05.003