When plucking a snail from the beach you’d be lucky to snag a left-coiling shell.That’s because only 5% of all snails are “lefties,” new research shows. Shell enthusiasts have long marveled at the lack of sinistral (left-coiling) snails among their collections, especially when other shelled mollusks, such as clams and the now-extinct ammonites—nautiluslike creatures that sported dozens of tentacles inside spiraled shells—are just as likely to be left- as right-coiling.
Now, in the largest survey of its kind, researchers inspected more than 55,000 snail species—representing two-thirds of all gastropods—to reveal that left-coiling has arisen more than 100 times, and yet few of the species that have made the switch have been particularly successful. In the rare cases where left-coiling took off, it was almost always on land, the team reported here in a presentation last week at the annual meeting of the Canadian Society of Zoologists.
The researchers don’t know why sinistrality is so rare underwater, but the most likely explanation, they say, is that unlike land snails that tend to hang around where they hatch out, the microscopic young of sea snails are carried on ocean currents that make the chance of meeting and reproducing with another left-coiling nest-mate slim. Without such a meeting, the left-coiling lineage goes extinct.
Long, long ago, O Best Beloved, the ancestor of the penguins could soar through the air. So why did the penguin give up flight? Rudyard Kipling never wrote a Just So story with an answer, but now scientists have one: The penguin doesn’t fly because it would rather swim.
A new study of murres, penguinlike seabirds that retain the ability to take wing, shows just how costly and inefficient it is to be both a diver and a flyer. The new findings back the long-held hypothesis that penguins gave up the heavens more than 70 million years ago to become kings of the waves.
“This study contributes a lot by putting hard numbers on the energy costs of moving through both the aerial and aquatic realms,” writes Daniel Ksepka of North Carolina State University in Raleigh, who studies penguin evolution and was not involved with the research, in an e-mail…
Stanford Biologist Deborah M. Gordon’s decades-long study of the collective behavior of harvester ant colonies has provided a rare real-time look at natural selection at work.
by Bjorn Carey
In ancient Greece, the city-states that waited until their own harvest was in before attacking and destroying a rival community’s crops often experienced better long-term success.
It turns out that ant colonies that show similar selectivity when gathering food yield a similar result. The latest findings from Stanford biology Professor Deborah M. Gordon’s long-term study of harvester ants reveal that the colonies that restrain their foraging except in prime conditions also experience improved rates of reproductive success.
Importantly, the study provides the first evidence of natural selection shaping collective behavior, said Gordon, who is also a senior fellow at the Stanford Woods Institute for the Environment…
… is an extinct genus of Reptiliomorpha (reptile like amphibians), which lived about 320-305 million years ago. Classification is uncertain, but it was possibly an early reptile or an amphibian close to the diadectomorphs. Its remains were found in the Czech Republic. Its name means “single-tooth lizard”. Solenondosaurus measured about 45 cm.
The Solenodonsaurus show a curious mix of characters making it difficult to place phyllogentically. The teeth lack labyrinthodont folding of the enamel, and it skull is without the otic notch seen in other reptiliomorph amphibians…
(read more: Wikipedia) (illustration by Dmitry Bogdanov)
Oldest evidence of split between Old World monkeys and apes discovered
Two fossil discoveries from the East African Rift reveal new information about the evolution of primates, according to a study published online in Nature this week led by Ohio University scientists.
The team’s findings document the oldest fossils of two major groups of primates: the group that today includes apes and humans (hominoids), and the group that includes Old World monkeys such as baboons and macaques (cercopithecoids).
Geological analyses of the study site indicate that the finds are 25 million years old, significantly older than fossils previously documented for either of the two groups.Both primates are new to science, and were collected from a single fossil site in the Rukwa Rift Basin of Tanzania.
Rukwapithecus fleaglei is an early hominoid represented by a mandible preserving several teeth. Nsungwepithecus gunnelli is an early cercopithecoid represented by a tooth and jaw fragment..
(read more: PhysOrg) (illustration by Mauricio Anton)
The threespine stickleback,Gasterosteus aculeatus, is native to northern Europe, northern Asia, and North America. Most populations are anadromous (they live in seawater but breed in freshwater or brackish water), but there are also freshwater populations confined to landlocked lakes
This species has contributed much to the study of species formation and it is a research organism for evolutionary biologists and geneticists studying adaptation to new environments.
Fruit bats and bat fruits: the evolution of fruit scent in relation to the foraging behaviour of bats in the New and Old World tropics
by Hodgkison et al.
Frugivory among bats (Chiroptera) has evolved independently in the New and Old World tropics: within the families Phyllostomidae and Pteropodidae, respectively. Bats from both families rely primarily on olfaction for the location of fruits. However, the influence of bats on the evolution of fruit scent is almost completely unknown.
Using the genus Ficus as a model, the aims of this study were to explore the chemical composition of fruit scent in relation to two contrasting seed dispersal syndromes in Panama and Malaysia and to assess the influence of fruit scent on the foraging behaviour of neo- and palaeotropical fruit-eating bats…
Amphibians Living Close to Farm Fields Are More Resistant to Common Insecticides
May 1, 2013 — Amphibian populations living close to agricultural fields have become more resistant to a common insecticide and are actually resistant to multiple common insecticides, according to two recent studies conducted at the University of Pittsburgh.
In a study published today in Evolutionary Applications, the Pitt researchers demonstrate, for the first time, that tadpoles from populations close to farm fields are more resistant to chlorpyrifos — one of the most commonly applied insecticides in the world, often sold as “Dursban” or “Lorsban.” In addition, a related study published in February shows that tadpoles resistant to chlorpyrifos are also resistant to other insecticides.
“While we’ve made a lot of progress in understanding the ecological consequences to animals that are unintentionally exposed to insecticides, the evolutionary consequences are poorly understood,” said study principal investigator Rick Relyea, Pitt professor of biological sciences and director of the University’s Pymatuning Laboratory of Ecology. “Our study is the first to explore how amphibian populations might evolve to be resistant to insecticides when they live in places that have been sprayed for many years.”…
The origins of winged flight is a hotly debated topic in paleontology. A study published last year in Science suggests that wings and feathers may have evolved in dinosaurs earlier than previously thought. When researchers took a closer look at several fossil specimens of Ornithomimus edmontonicus, they found winglike forelimbs and hundreds of traces of filaments suggestive of feathers. Ornithomimus belongs to a group of dinosaurs that appears in the fossil record millions of years before maniraptorans, the group of feathered dinosaurs that survives today as birds, the findings hint at even earlier evolutionary origins of wings and feathers.
O. edmontonicuswas no flier, however. The researchers estimate it weighed 150 kilograms (330 pounds), so it’s wings more likely served some other function, perhaps in courtship or brooding.
Image: Julius Csotonyi (above)/Royal Tyrrell Museum (below)
If Nyasasaurus parringtoni isn’t the earliest dinosaur, it’s the closest thing to it that scientists have found so far. Working from an upper arm bone and six vertebrae found in Tanzania in the 1930s, researchers surmise that Nyasasaurus would have been about the size of a Labrador retriever, but with a much longer tail. In a paper published last year in Biology Letters.
They argue that it lived in the southern part of the supercontinent Pangea about 243 million years ago, predating all other known dinosaurs by at least 10 million years.
Feathered Dinosaurs were Diverse, Like Darwin’s Finches
by Megan Gannon
Flightless feathered dinosaurs with parrotlike beaks and long, skinny claws that scampered around North America may have been the Darwin’s finches of the Late Cretaceous era.
Fossils of at least five species of vegetarian birdlike dinosaurs known as caenagnathids have been found from West Texas to Canada with wide variation in their beak shapes and body size, giving scientists clues about how the small creatures could coexist by carving out different dietary niches.
Charles Darwin’s theory of evolution by natural selection was famously inspired by the diversity of beak shapes among finches on the Galapagos Islands, which he took as a sign that the birds had somehow adapted to the specific environments where they lived. More recent research has shown that Darwin’s finches can evolve quite quickly. For instance, one species shrunk its beak size to better compete with another bird for small seeds in a mere two decades.
Millions of years ago, different species of caenagnathids may have similarly adjusted their beak size across western North America…
(illustration by Nicholas R. Longrich/Yale - This new species, Leptorhynchos (“little jaw”) gaddisi, belongs to a broader group of bird-like dinosaurs characterized by toothless beaks and long, slender claws.)
Dinosaur predecessors gain ground in wake of world’s biggest biodiversity crisis
Many scientists have thought that dinosaur predecessors missed the race to fill habitats emptied when nine out of 10 species disappeared during the Earth’s largest mass extinction, approximately 252 million years ago. The thinking was based on fossil records from sites in South Africa and southwest Russia. It turns out that scientists may have been looking for the starting line in the wrong places.
Newly discovered fossils from 10 million years after the mass extinction reveal a lineage of animals thought to have led to dinosaurs taking hold in Tanzania and Zambia in the mid-Triassic period, many millions of years before dinosaur relatives were seen in the fossil record elsewhere on Earth.
“The fossil record from the Karoo of South Africa remains a good representation of four-legged land animals across southern Pangea before the extinction event. But after the event animals weren’t as uniformly and widely distributed as before. We had to go looking in some fairly unorthodox places,” said Christian Sidor, University of Washington professor of biology. He’s lead author of a paper appearing the week of April 29 in the early edition of the Proceedings of the National Academy of Sciences…
I don’t know why a raven is like a writing desk, but I do know that Microraptor was like a cat. The feathery little dinosaur was cute and glossy, but those adorable features were offset by the carnivore’s excessive pointiness. Even though the non-avian dinosaur was about the size of a raven, and even had feathers with an iridescent corvid sheen, Microraptor still bore pointed teeth, grasping hand claws, and the classic deinonychosaur switchblade talons on each foot. All of this made Microraptor a cuddly-looking little cutter, much like a cat. And the dinosaur shared something else with felines – a fondness for fish.
Since the time the dinosaur was named in 2000, paleontologists have discovered multiple specimens of Microraptor in the 120 million year old lake deposits of China. Many of these are not only articulated, but fossilized to such a fine degree that the petrified remains of their feathers remain intact. This hi-def preservation also safeguarded tatters of Microraptor meals. One Microraptor individual, described two years ago, had feasted on an early bird shortly before perishing in a case of non-avian dinosaur eats avian dinosaur. But a Microraptor known as QM V1002 enjoyed a different last meal.
Fossilized in the position of QM V1002′s stomach, paleontologist Lida Xing and colleagues explain in a new Evolution paper, are the scraps of bony fish. A small mass of fin rays, vertebrae, and other piscine tidbits are tucked between the dinosaur’s ribs, some of which had been etched by digestive fluids when the Microraptor was still alive. The question is whether this Microraptor actually caught fish or just happened along some convenient snacks thrown up onto the lakeshore…
Birds and humans are the most common bipedal species in the modern world, but their legs are strikingly different. Humans are basically straight-legged, which allows their bones to support their resting body weight. But bird legs are bent into a zigzag, putting them in a crouched position that requires much more muscular effort to stand.
Turtle Genome Analysis Sheds Light On Turtle Ancestry and Shell Evolution
by Science Daily staff
Apr. 28, 2013 — From which ancestors have turtles evolved? How did they get their shell? New data provided by the Joint International Turtle Genome Consortium, led by researchers from RIKEN in Japan, BGI in China, and the Wellcome Trust Sanger Institute in the UK provides evidence that turtles are not primitive reptiles but belong to a sister group of birds and crocodiles. The work also sheds light on the evolution of the turtle’s intriguing morphology and reveals that the turtle’s shell evolved by recruiting genetic information encoding for the limbs…
Zhuo Wang, Juan Pascual-Anaya, Amonida Zadissa, et al. The draft genomes of soft-shell turtle and green sea turtle yield insights into the development and evolution of the turtle-specific body plan. Nature Genetics, 2013; DOI: 10.1038/ng.2615