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This tiny guy stumbled into our house in the suburbs of Sydney. What species is it?
It's dark and has two yellow stripes going along the length of its body. They start on its head and go right above its eyes.
This looks like a Common Garden Skink (Lampropholis guichenoti)
Further information can be found here and here
The description is a quote from the first source:
The colour of the skin of a common garden skink is mostly a brown-grey colour, and it usually has a black or dark coloured stripe down either side of its body and a copper coloured head. The diet of common garden skinks generally consists of insects and vegetation, and can include caterpillars, spiders, slugs, cockroaches, crickets, worms and ants, and fruit and vegetables. Small and enclosed spaces, such as rocks or trees, are the sought after home for common garden skinks, and they are commonly found in urban gardens, hiding in among plants or leaves. Common garden skinks generally grow to a length of 9 centimetres (3.5 inches), and they have five toes on each of their four legs, as well as a long tail. Common garden skinks can release their tails when caught by predators, such as birds, cats and larger reptiles like snakes.
Once Mistaken For a Tiny Bird With Teeth, This Fossil Is Now Officially a Lizard
Last year, a tiny fossil became big news. Trapped inside ancient amber, scientists thought they'd found the skull of a minuscule, hummingbird-like dinosaur with pointy teeth, bulging eyes, and surprisingly robust bones.
It was like no ancient bird or dinosaur ever discovered before. That's because it was actually neither.
A similar skeleton found in the same area now suggests the so-called "eye tooth bird" (Oculudentavis khaungraae) is, in reality, a lizard. Its long snout had simply been squashed over time so that it resembled more of a beak.
"Imagine taking a lizard and pinching its nose into a triangular shape," explains Edward Stanley, director of the Florida Museum of Natural History.
"It would look a lot more like a bird."
Digitally isolated bones from the skull of O. naga (left) and O. khaungraae (right). ( Edward Stanley)
Even with such a beak-like snout, some experts remained unconvinced by the discovery. In 2020, shortly after the tiniest known dinosaur was announced, scientists in the field began disputing the classification.
While some early bird fossils have been found with mouths full of teeth - a remnant of their dinosaur heritage - these gnashers are usually nestled in sockets, not directly attached to the jaw bone and no early bird has ever possessed such lizard-like eyes.
Ultimately, these arguments were enough for editors of the journal to retract the Oculudentavis paper altogether, declaring it a misclassification. While some of the original study authors continue to stick to their guns, another lizard fossil found nearby now indicates they were indeed mistaken.
This new fossil also has a puzzling appearance that doesn't seem to fit in anywhere. At first glance, it doesn't look much like the other skull reported last year. But after isolating and comparing bones found in each amber deposit, researchers have found several key comparisons between the two.
O. naga specimen with preserved bone and soft tissue. (Edward Stanley)
Both fossils are roughly the same size, have teeth attached to the jawbone, and possess lizard-like eye sockets of similar size and shape. What's more, the newly discovered fossil also has visible scales and a complete skull, with a hockey stick-shaped squamosal bone that's present in all scaled reptiles.
The two tiny fossils are not of the same species, but CT scans suggest they do belong to the same genus of lizard, which lived roughly 100 million years ago in the same region of the world. The new species has therefore been named Oculudentavis naga.
"It's a really weird animal. It's unlike any other lizard we have today," says herpetologist Juan Diego Daza from Sam Houston State University.
"We think it represents a group of squamates we were not aware of."
Artistic interpretation of O. naga. (Stephanie Abramowicz/Peretti Museum Foundation)
The unusual features in both these lizards is probably why they have proved so tricky to place in the animal kingdom. That, and the fact that the original Oculudentavis skull had a slightly squashed snout.
Reconstructing the original shape of these fossils was painstaking work, but ultimately it showed that O. khaungraae's snout had been squeezed during fossilization.
Without this compression, it would have resembled the long snout on the other lizard fossil, O. naga, rather than a beak, researchers say.
"Despite presenting a vaulted cranium and a long and tapering snout, it does not present meaningful physical characters that can be used to sustain a close relationship to birds, and all of its features indicate that it is a lizard," says Susan Evans, who studies vertebrate morphology and paleontology at University College London.
The O. naga specimen was so well preserved, scientists could even make out some soft tissue structures on the top of its snout and underneath its chin. These appear to be loose flaps of skin that the reptile may have inflated during displays, which is common for other lizards.
Researchers still aren't sure where Oculudentavis exactly sits in the lizard family, but at least now they are barking up the right tree.
Outwardly, little of the animal's body seems adapted to flying, gliding or moving through the air in any way.
But a slow-motion camera has revealed that when the lizard jumps from a height, it can slow the rate of its descent and land gently on the ground.
The lizard's surprising aerial ability might help explain how some animals became true gliders.
Details of the little lizard's talents are published in the Journal of Experimental Biology.
Active flight, powered by the flapping of wings, has evolved in three living lineages of animals: birds, bats and insects.
But at least 30 different types of animal have evolved the ability to control their aerial descent, by parachuting or gliding to ground.
For example, gliding frogs use huge webbed feet, flying squirrels use long flaps of skin between their legs, and flying fish use their fins to glide.
Other animals have less obvious morphological adaptations.
Gliding snakes flatten and undulate their bodies, which helps to slow their fall while some species of ant are so tiny they can jump out of trees and freefall gently to lower on the trunk without hurting themselves.
So Bieke Vanhooydonck of the University of Antwerp became extremely interested when she read some old scientific papers reporting anecdotal evidence that a relatively ordinary species of lizard might also be able to glide from tree to tree.
Holaspis guentheri belongs to a group of lizards known as lacertids, which live in the Old World.
Though colourful, they do not stand out in terms of their behaviour, morphology or ecology.
"Also, compared to other gliding lizard species, it does not have any conspicuous morphological adaptations to an aerial lifestyle, ie no cutaneous flaps, webbed feet etc," says Vanhooydonck.
"It made me very curious about whether these animals were really able to 'glide' and if so, how they were accomplishing it."
So Vanhooydonck and colleagues in Belgium and France filmed individual lizards leaping from a platform two metres above ground.
They compared the performance of H.guentheri with a rock-dwelling lizard (Podarcis muralis) that never takes to the air, and a highly specialised leaping gecko (Ptychozoon kuhli) that has a range of skin flaps that it uses to parachute to the ground.
For each, they examined the duration of each species' descent, the horizontal distance it covered and at what speed.
Both the rock-dwelling lizard and H.guentheri landed 50 centimetres from the base of the platform, while the gecko landed up to 1m away. But H.guentheri fell for longer, and more slowly than its rock-dwelling competitor.
"Much to our surprise, H. guentheri is able to slow down its descent and has low impact forces upon landing," says Vanhooydonck.
In fact, the lizard weighs just 1.5g, which is one third of the rock-dwelling lizard's weight and one-tenth of the gecko's.
Once weight was factored in, the researchers found that H.guentheri landed 20cm further away that it should have done had it fallen like a stone.
"Also its wing loading, the ratio of mass to surface area, is extremely low and in the same range as that of the gekko."
However, the two species achieve this aerial ability in different ways. As a result of its webbed feet and body flaps, the gecko achieves a low wing loading by having a large surface area.
H. guentheri has a low wing loading too, but by being so light.
X-ray scans of the lizard's body revealed its bones are packed full of air spaces.
Although the lizard's light weight and ability to fall gently are linked, it is still unclear whether its air-filled bones are an adaptation for parachuting, or whether they evolved for another reason.
It is also unclear whether H.guentheri glides from tree to tree to escape predators or move about more efficiently.
"Because of [the lizards'] secretive lifestyle, it is very hard to observe them in the wild, but it seems plausible they use it as an escape response," says Vanhooydonck.
And that could be just how other gliding animals took the first evolutionary steps towards an aerial lifestyle, she says.
Still endangered: the Blunt-nosed Leopard Lizard
Dr. Rory Telemeco, Assistant Professor in the Department of Biology at Fresno State, seems fated for a career studying lizards … and maybe even saving them.
“I was a dinosaur nut as a kid,” he said. “Totally, I was the little boy in Jurassic Park.”
His passion for predators led him, ironically, to be involved in efforts to preserve the Blunt-nosed Leopard Lizard, which has long been on the endangered-species list.
“This species mostly eats arthropods — grasshoppers, spiders — but will also eat other lizards and small rodents if they get the chance,” he said. “They’re the biggest lizard out there. They’re one of the top predators.”
Top predators notwithstanding, they are federally listed as an endangered species — in fact, they are one of the inaugural species on the original list in the Endangered Species Act of 1973. And they are still at risk.
Dr. Telemeco is hoping that his work can change that. But then, he always did have a liking for lizards.
In college, his very first class at the undergraduate level was Zoology at 8 a.m. on Mondays, Wednesdays, and Fridays. His professor happened to work with … you guessed it, lizards.
Needless to say, the class appealed to Dr. Telemeco, despite the early hour at which he had to be on campus.
“I always liked reptiles, anyway,” he said. “So I started that year working to understand social behavior in Collared Lizards with my professor, in their habitat.”
Although Dr. Telemeco made several forays into trying other areas of study, such as working at a vertebrate paleontology lab for a few years as an intern, he eventually found that he was steering away from studying fossilized bones and more toward studying live lizards. Yes, lizards. Again.
“I also really like snakes,” he said, “but, due to my allergies to anti-venom serums, I decided there were enough people studying venomous snakes.”
It was when he received a Fulbright scholarship and did his master’s work in Australia that Dr. Telemeco began studying life history theory, which describes how evolution shapes how much energy species put into reproduction.
“The theory looks at what are the evolutionary pressures that act on animals to make reproductive decisions, what ends up being the optimal strategy,” he said. “At the same time, I became more and more aware of climate change, and how changes in the abiotic factors of the environment affect life history, especially in animals whose welfare is really linked to temperature.”
These two interests coalesced into … yes, once again, studying lizards … the Blunt-nosed Leopard Lizard, to be more precise. These lizards are endemic to the San Joaquin Valley and only live in fairly undisturbed desert habitats.
The more you learn about them, the more these little lizards seem incredible. They find ways to survive against the odds.
“As ectotherms, lizards historically have been thought of to be much under the whims of the environment,” Dr. Telemeco said. “Turns out, they have a lot of tools for modifying their body temperatures. They’re just not doing it metabolically, like the endotherms, mammals and birds, are.”
Endotherms use a lot of their energy to generate heat, but ectotherms use a lot of their energy for reproduction. Yes, that’s right. The Blunt-nosed Leopard Lizard is built to reproduce. Even so, probably due to environmental factors, the Blunt-nosed Leopard Lizard has a hard time keeping its numbers up.
Dr. Telemeco is part of a multi-agency collaboration with the U.S. Bureau of Land Management, Cal Poly San Luis Obispo, and the Fresno Chaffee Zoo performing range-wide work on northern and southern groups of the Blunt-nosed Leopard Lizard.
“We try to understand the ecology involved in preserving this species and what kind of habitat they need to have,” he said.
The Valley at one point was basically desert scrub and huge wetlands, and rapid changes in the environment appear to have negatively impacted the Blunt-nosed Leopard Lizard’s normal reproduction rate.
“It was a very different landscape a hundred years ago,” Dr. Telemeco said. “Probably because the environment is now so harsh with modern landscapes, these lizards only seem to live a couple of years in the wild, and they are not reproducing as much.”
In order to find a way to increase the lizards’ chances of survival, he and his students put temperature-sensitive radio collars on them, then use stationary antennas in the landscape to pick up the signals that allow for real-time body temperature measurements on the animals throughout the year.
“We’re looking at some of these desert landscapes they live in,” Dr. Telemeco said. “Some of them look like just bare earth, with no cover, and others have spotted shrubs on them, the most common being Ephedra californica, or the California jointfir, or cañatillo. We are testing how important the shrubs are to Blunt-nosed Leopard Lizard habitats.”
Being a lizard isn’t as easy as it sounds. Basically, the landscape is too hot during the day and too cold at night for the lizards to be active, so lizards have to resort to going into their underground rodent burrows.
“What we’ve found is all the microhabitats in landscapes without shrubs get way too hot, deadly hot, late in the day,” Dr. Telemeco said. “But the lizards are still maintaining a good temperature, by going into their burrows, probably deeper underground than we’ve measured … that’s their only option, to go underground. But if they can just climb a couple of inches above ground into a shrub, they can stay out happily longer in their habitats.”
Measurements confirm that lizards can stay above ground more often during the day if they have shrubs available.
“It looks like areas with shrubs give them an extra three hours a day in which they can be out and about, living their lives out of the underground burrows,” he said. “We’re trying to see how they can use the landscape to maintain their body temperatures, and what’s constraining them when they can be out eating and reproducing. Our study results potentially put more focus on preserving landscapes with a complex shade structure.”
Why be out and about? Well, for an endangered species, it’s critical to reproduction. Egg clutches are typically about four eggs for the Blunt-nosed Leopard Lizard. Dr. Telemeco’s efforts to monitor reproduction include using portable field ultrasound on the females to find out how the eggs are developing, how many eggs are developing, how big the eggs are, and how much energy the lizards are devoting to reproduction.
“They can produce three clutches per season, from about April through the very beginning of July,” he said. “Outside that time, they go into the non-reproductive phase of their life.”
So do lizards make good parents?
“With lizards, the diversity of things that they do is very extreme, everything from individuals that will lay eggs and leave, which is probably the most common,” he said. “Then there are species of skink that will rotate the eggs during incubation and stay with them during development. Then there are alligator lizards that will guard the nest. There are even species that give live birth, keeping their developing young in their bodies.”
What do the Blunt-nosed Leopard Lizard do? Scientists know they lay eggs, but beyond that aren't really sure because a natural nest has never been observed. The best guess is that they typically lay the eggs in an underground nest and cover them with dirt. Sounds like easy parenthood, doesn’t it? But only a small number the young seem to be surviving.
Finding optimal habitats could be the key to reversing that. Dr. Telemeco and his teams also study what the lizards’ home ranges are, figuring out exactly how they’re using the landscape.
One thing is for sure … this California native species is lucky to have someone like Dr. Telemeco looking out for its future.
This fossil isn’t a hummingbird-sized dinosaur, but an unusual lizard
A recently discovered fossil is indeed a strange lizard rather than a small dinosaur.
What was once thought to be the smallest dinosaur ever found has now been confirmed to be a lizard.
In March 2020, a Nature paper stirred some controversy when scientists identified a skull encased in 99 million year old Myanmar amber as that of a tiny, bird-like dinosaur. The authors dubbed the specimen Oculudentavis khaungraae, and acknowledged the strangeness of the fossil—most notably, they found the shape of the bones, especially around the eye region, didn’t seem to follow other bird or dinosaur evolutionary patterns.
Following publication, other paleontologists refuted the paper’s findings. Another team of scientists published a preprint in bioRxiv in June of 2020, stating that the skull more closely matched one of a lizard. The Nature paper was retracted in July of 2020. Released as a preprint in August 2020, and now as a fully peer-reviewed study in Current Biology, another study by a third team of scientists confirms that Oculudentavis is a lizard genus.
The new paper is based on another, better preserved specimen—a fossil also from Myanmar, whose skull is about a half an inch long, and also around 99 million years old. Using CT scans and 3D remodeling, the authors concluded that their fossil was a different species in the same genus as O. khaungraae—they called their specimen Oculudentavis naga—and that both species were indeed strange lizards rather than small dinosaurs.
“It’s a really weird animal. It’s unlike any other lizard we have today,” Sam Houston State University herpetologist and study co-author Juan Diego Daza said in a statement. He added that the Cretaceous Period, when these fossils were formed, was when many lizard and snake groups emerged, but “they still hadn’t evolved their modern appearance,” which explains why identifying these fossils can be so challenging. “That’s why they can trick us. They may have characteristics of this group or that one, but in reality, they don’t match perfectly.”
The way the amber fossils were preserved distorted the skulls of both Oculudentavis specimens, which contributed to the original misunderstanding. O. khaungraae’s snout was distorted into a narrower cone shape, giving a birdlike impression, while O. naga’s upper skull was likely flattened during fossilization to appear more lizard-like.
The genus name Oculudentavis, established by the authors of the first Nature paper, means “eye tooth bird” in Latin. Even though that name is technically inaccurate now, Daza told CNN that taxonomic rules for naming and organizing animal species dictate that they have to continue using it. “Since Oculudentavis is the name originally used to describe this taxon, it has priority and we have to maintain it,” Daza said. “The taxonomy can be sometimes deceiving.”
Do Gila monsters climb trees?
Seeing a Gila monster climb a tree is a very rare occurrence. Click for more detail.
So, how often does this happen? (Or in other words, is this a behavior Gilas actually use regularly?) Well, there are only a handful of recorded observations of Gila monsters climbing trees. So in general, they likely don't climb trees much. Mostly, the times they've been observed climbing, they were trying to escape potential predators (like humans, as shown in the video). There is also one observation of a Gila that might have been climbing up to a low tree branch so that it could cool off a bit, as the ground was very warm.
"But wait," you might be thinking. "I've seen other pictures of big Gila monsters climbing trees." Well. not exactly. Most likely, what you saw in those pictures was one of the Gila monster's closest evolutionary cousins, a beaded lizard.
Is It a bird or a Lizard?
Study lead author and University of Bristol paleontologist Arnau Bolet said that there are several factors why scientists got confused about which species do the fossils truly belong to, Smithsonian Magazine reported.
Bolet said that the long and tapering snout and the vaulted skull roof gave an impression that it was a bird. However, a closer examination of the fossil showed the lizard-like appearance of the fossil that cannot be seen in birds.
For instance, the teeth of the Oculudentavis are fused to the jaw, which is a characteristic commonly seen in lizards and snakes. More so, the shape and connections of the skull of the fossils are from a lizard and not a bird. The analysis of the second fossil confirms this observation.
The team used CT scans of reptiles inside the second specimen and reanalyzed them from the first specimen. Bolet and his colleagues named the second species as Oculudentavis naga in honor of the Naga people.
"It's a really weird animal. It's unlike any other lizard we have today," herpetologist Juan Diego Daza from Sam Houston State University said in a statement in Florida Museum news release. "We think it represents a group of squamates we were not aware of."
On the other hand, some experts not part of the study, like Michael Caldwell of the University of Alberta, said that the Oculudentavis might not be a lizard. He suggests that it might be much more ancient and unusual.
Fiction to fact
Scientists just "appreciating" precise information may be a bit of an understatement.
He's now the dean of the College of Arts and Sciences at UC. But before his current role, his work centered on the study of invasive species.
It's extraordinary to know where, exactly, they came from, how many were introduced, where they were introduced and when that happened, Petren says. And having those factors figured out can create really rich research opportunities. You can fill in the blanks of certain equations, so to speak, with critical dates and locations.
And all of those factors were detailed in the 1989 correspondence penned by George Rau, the stepson of Fred Lazarus III.
The Lazarus lizard has hard scales on its head because it's a burrowing creature. The rest of its body is actually quite soft. (Photo: The Enquirer/Meg Vogel)
Rau had collected the creatures in Northern Italy, specifically around Lake Garda, about 80 miles east of Milan, he wrote.
Rau wrote he snagged about 10 on vacation. And released them in the backyard of the family compound on Torrence Court in East Walnut Hills, the peak of our Lizard Hill, when he returned in either 1951 or 1952.
On the surface, his claim added up. After all, it was just a slight twist on one of the well-circulated legends of the lizard.
And it sort of made sense. They could survive here given that the average temperatures and precipitation in that part of Italy are similar to those here in Cincinnati. It gets a bit colder here, but not by much, and the lizards spend the winters mostly huddled underground anyway.
But science doesn't rely upon lore or a letter. So neither did Cassandra Homan.
As a UC biology master's student, she took genetic samples from lizards in northern Italy and compared them with samples taken from those in our backyard.
As with many species, the male Lazarus lizard usually display brighter and bolder color than the females. (Photo: The Enquirer/Meg Vogel)
Simply put, they are family.
These results didn't just support Rau's story. It also revealed the lizard population experienced "a very significant bottleneck," Homan said, meaning the community here has low genetic diversity because of a small starting population.
The most genetic diversity is found in the reptiles still living around Rau's former home on Lizard Hill. And more genetic diversity indicates this is, in fact, the introduction point.
According to Homan's study, not all of the 10 lizards Rau released survived here. So an already small founding party got somehow smaller.
As far as science can determine, as few as three lived to produce the estimated millions here today.
Based on this genetic research, plus what's known about the lizard's reproduction and life expectancy, scientists can guess we've hosted 33 generations of lizards since the original trio.
Molecular analyses also revealed a new name. Since 2005, our Lazarus is officially a subspecies of its ancestral Podarcis muralis.
The Podarcis muralis maculiventris.
Or, as a young George Rau might say, pets.
Diving Anole Lizards Can Respire Underwater by Rebreathing Exhaled Air
Inspired by natural history observations in Haiti and Costa Rica, a team of biologists from the University of Toronto and elsewhere conducted experiments documenting routine air-based underwater respiration in several distantly related semi-aquatic lizard species of the genus Anolis. Their results appear in the journal Current Biology.
Semi-aquatic anoles live along Neotropical streams and frequently dive for refuge, remaining underwater for up to 16 minutes. Image credit: Lindsey Swierk.
“It’s easy to imagine the advantage that these small, slow anoles gain by hiding from their predators underwater — they’re really hard to spot,” said co-author Dr. Lindsey Swierk, a researcher in the Department of Biological Sciences at Binghamton University.
“But the real question is how they’re managing to stay underwater for so long.”
In the study, Dr. Swierk and colleagues conducted experiments documenting routine air-based underwater respiration in several anole species.
They found that these lizards can respire underwater by rebreathing exhaled air that is trapped between their skin and surrounding water.
“We found that semi-aquatic anoles exhale air into a bubble that clings to their skin,” said first author Chris Boccia, a researcher in the Department of Ecology and Evolutionary Biology at the University of Toronto.
“The lizards then re-inhale the air, a maneuver we’ve termed ‘rebreathing’ after the scuba-diving technology.”
The scientists believe that hydrophobic skin, which they observed in all sampled anoles, may have been exaptative, facilitating the repeated evolution of specialized rebreathing in species that regularly dive.
Their analyses strongly suggest that specialized rebreathing is adaptive for semi-aquatic habitat specialists.
Air-based rebreathing may enhance dive performance by incorporating dead space air from the buccal cavity or plastron into the lungs, facilitating clearance of carbon dioxide, or allowing uptake of oxygen from surrounding water.
The authors used an oxygen sensor inside the rebreathed bubbles to determine whether anoles were consuming oxygen from the bubble.
In true scuba-tank fashion, they discovered that the oxygen concentration in an anole’s air bubble decreases over the length of the dive, in support of this idea.
“The finding that different species of semi-aquatic anoles have evolutionarily converged to extract oxygen from their rebreathed air bubbles leads to other exciting questions,” Dr. Swierk said.
“For example, the rate of oxygen consumption from the bubble decreases the longer an anole dives, which could possibly be explained a reduction in an anole’s metabolic rate with increased dive time.”
World's Smallest Lizard Discovered In Caribbean
The world's smallest lizard has been discovered on a tiny Caribbean island off the coast of the Dominican Republic. The newly discovered species not only ranks as the smallest lizard, but it also is the smallest of all 23,000 species of reptiles, birds, and mammals, according to a paper to be published in the December issue of the Caribbean Journal of Science by Blair Hedges, an evolutionary biologist at Penn State, and Richard Thomas, a biologist at the University of Puerto Rico.
So small it can curl up on a dime or stretch out on a quarter, a typical adult of the species, whose scientific name is "Sphaerodactylus ariasae," is only about 16 millimeters long, or about three quarters of an inch, from the tip of the snout to the base of the tail. It shares the title of "smallest" with another lizard species named Sphaerodactylus parthenopion, discovered in 1965 in the British Virgin Islands. Hedges and Thomas discovered small groups of the new species living in a sink hole and a cave in a partially destroyed forest on the remote island of Beata, which is part of the Jaragua National Park in the Dominican Republic.
"Our discovery illustrates that we still don't know everything about the Earth's species, even in areas that are very close to the United States," Hedges says. "The island home of this tiny lizard is closer to Miami than Miami is to Puerto Rico, and we did not even know the species existed, although the area has been studied by biologists for several hundred years." Hedges says the habitat that this species needs to survive is disappearing rapidly. "People are cutting down trees even within the national parks and, if they take the forest away, these lizards and other species will disappear."
Economic and law-enforcement difficulties are contributing to deforestation of the Caribbean forests, which are even more fragile and more threatened than those in the Amazon of South America because they are so small. "In the Caribbean, forests that used to cover all of the land now typically cover less than 5 percent--and they are being cut down at an increasing rate, mainly for subsistence farming and fuel," Hedges says. "Although there are laws against cutting down trees in the national parks, the enforcement of the laws is not enough to protect the forests, for a variety of reasons."
Hedges and Thomas went to the remote Isla Beata specifically with the goal of discovering previously unknown species that might be living there. "We tend to explore more rugged and hard-to-reach areas than other scientists," Hedges says.
The "smallest" and "largest" species of animals tend to be found on islands, the researchers say, because species can evolve there over time to fill ecological niches in the habitat left vacant by other organisms that never reached the remote locations. If a species of spider is missing from an island, for example, the lizards there might evolve into a very small species to "fill" the missing spider's ecological niche.
"Habitat destruction is the major threat to biodiversity throughout the world," says Hedges, who has studied Caribbean species for many years, and has long recognized it as a "hot spot" of threats to biodiversity. "The Caribbean is now widely recognized by conservationists and biologists as an ecological hot spot because it clearly is an area that has an unusually high percentage of endangered species that occur nowhere else in the world," Hedges says. "Most land species on Earth have evolved to live in forested regions, and now humans are destroying the forests--which is a big problem, especially on islands, where species have restricted ranges."
"It is hard to say whether this lizard is as small as a lizard can get, but you would think it probably is approaching that limit because it is the smallest of all 23,000 known species of reptiles, birds, and mammals," Hedges says. "The smaller an animal gets, the larger its surface area gets as a percentage of the volume or mass of its body. At some point, it gets to be physiologically impossible to get any smaller." For the lizard, which lives in a dry environment surrounded by comparatively moist leaf litter, the limiting factor is the danger of desiccation. "If we don't provide a moist environment when we collect them, they rapidly shrivel right up and die by evaporation from the proportionally large area of their surface," Hedges explains.
Hedges and Thomas named the new lizard in honor of Yvonne Arias, a champion of conservation efforts in the Dominican Republic. Arias is president of the organization known as Groupa Jaragua, a non-governmental organization set up specifically for preserving the biodiversity of the Jaragua National Park.
Hedges and Thomas have discovered and described more than 50 new species of amphibians and reptiles throughout the Caribbean, mostly for genetic and evolutionary studies. Finding them, collecting them, and naming them is a necessary first step for other types of research. Hedges says this exploration and discovery of new species also is critical for protecting biodiversity. "It is difficult to protect a species when you don't know it exists," he says.
This research was sponsored by the Biotic Surveys and Inventories program of the U. S. National Science Foundation.
PHOTOS:High-resolution images of the lizard plus other images and information are available from a link on the web at http://www.science.psu.edu/alert/Hedges11-2001.htm.
Materials provided by Penn State. Note: Content may be edited for style and length.
Looking under the skin
Though Chédotal was not involved in the current research, data from his lab fueled the investigation into fetal muscle development. In 2017, Chédotal and his colleagues published a collection of detailed 3D snapshots of human embryos and fetuses the likes of which had not been seen before. The team used a technique called "whole-mount immunostaining" to render the skin of their samples transparent and highlight specific kinds of cells within the tissue. Using antibodies that latch onto myosin, a protein found only in muscles, the researchers captured various stages of human muscle development in high-resolution.
As an anatomist, Diogo had the skill to spot unusual muscles lurking in the images of fetal hands and feet, Chédotal said. Diogo pulled 13 3D images from the embryonic image database, representing embryos and fetuses between roughly 7 and 13 gestational weeks old. His team found that, at about week 7 of gestation, human fetuses have hands and feet that contain about 30 muscles each, but the number dwindles to just 20 about six weeks later.
For example, a muscle in the hand known as "contrahens 5" connects to the pinky finger and pulls the digit down and toward the midline of the hand. The muscle appears in adult monkeys and developing human embryos, but the researchers observed that around gestational week 10, the tissue begins to degrade and completely disintegrates before week 11. In the feet, muscles that lie between the metatarsal bones in the feet and pull the toes together fully form and then break down by week 9.
Though some muscles appeared to degrade or fuse into other muscles as early as week 7, some persisted well into week 11, "which is strikingly late for developmental atavisms," Diogo said in a statement.
"These are muscles that we know were present in our ancestors . and they are still there," Diogo said of the transient structures. The muscular remnants are known as atavisms &mdash anatomical structures that have been lost in certain organisms but might appear during embryonic development or in adults as variations or anomalies.
Although humans normally lose one-third of their atavistic limb muscles before birth, according to the study, on rare occasions, a muscle or two persists through the pruning and hangs around into adulthood, Diogo said. The lingering muscles often go unnoticed, neither causing problems nor granting their owner super-nimble digits, but appear to be significantly more common in individuals with developmental delays, such as those with Down syndrome or Edwards syndrome. It may be that people are more likely to retain atavistic muscles when they experience arrested or delayed development in the womb, the authors suggest.
The study provides the "first precise atlas" of embryonic limb development in humans, Delphine Duprez, a developmental biologist at the Institute of Biology Paris-Seine, told Live Science in an email. However, she added that the results have yet to be verified and may prove difficult to confirm, given that it remains "difficult to study muscle development in human embryos as compared to animal models."
In hopes of easing embryonic research, Chédotal and his lab members are continuing to build up their database of images. Now, they can tag up to eight tissue types with different antibodies at one time, meaning they can show how arteries, nerves and muscles interact in early human development. Muscles need to be hooked up to nerves and well supplied with blood to survive, so the detailed data may allow scientists like Diogo to piece together exactly when, why and how muscles disappear in the womb, he said.
The growing database, which is already available for public use, will eventually be adapted so that it is compatible with virtual reality and other platforms that enable users to interact with 3D images, Chédotal added. He hopes that the database will prove useful to everyone from acclaimed researchers to medical students, who up until now have studied fetal development from decades-old illustrations in textbooks, he said.
Diogo plans to use images from the database to study how the human head, arteries and nerves develop in utero. Beyond unearthing new details of human evolutionary history, Diogo said he aims to help medical professionals predict exactly what lies beneath their patients' skin. If researchers could predict which anatomical variations might be present in a particular patient, he suggested, doctors could be better prepared for surgery and generally deliver superior care.