scientificillustration
dendroica:

Coloured feathers readied first birds for take off

Before the first birds could take flight, they needed a lift from an unexpected source: colourful feathers. As well as giving birds the most colourful plumage on earth, it seems pigment factories in their feathers primed their feathery dinosaur ancestors for flight by creating feathers of many different shapes. The same pigment factories may also have turbocharged the proto-birds’ metabolism, helping them into the air.
This insight comes from a study of cellular pigment factories called melanosomes from the feathers, hairs and skin of 181 living birds, mammals and reptiles, plus 13 fossils of ancient lizards, turtles, dinosaurs and pterosaurs.
Julia Clarke of the University of Texas at Austin and her colleagues found that melanosomes suddenly became much more diverse in the lineage leading to birds. This happened at the same time that feather-like appendages appeared in maniraptoran dinosaurs, the forerunners of birds. These “pinnate” feathers resembled the familiar branched structure of modern bird feathers, and contained vastly more diverse melanosomes, in terms of their length, width and shape than the samples from ancient lizards and dinosaurs….
But it’s not just about feathers. The melanosome diversity explosion may also have led to higher metabolic rates in the forerunners of birds. Such rapid metabolisms are essential for powered flight.
"Many of the genes involved in the melanin colour system are also involved in other core processes such as food intake, stress responses, reproductive behaviour and more," says Clarke. That means the change in pigment could be linked to larger changes in the animals’ energetics and physiology.
This is corroborated by the modern animals, where melanosome diversity is linked to metabolism. “Only in living warm-blooded terrestrial vertebrates which independently evolved higher metabolic rates did we find the melanosome diversity we also see in feathered dinosaurs,” says Clarke.

(via New Scientist)
Photo: Analysis for the distribution of shapes of melanin-containing organelles (melanosomes) in fossil and living amniotes shows that fuzz-covered dinosaurs like Sinosauropteryx share similarities with living lizards, turtles and crocodilians. In these living taxa color and the shape of the melanosomes are not linked in such a way that color can be reconstructed from melanosome shape alone. Melanosomes in Sinosauropteryx don’t presently tell us if this animal was brown, blackish or grey. However, feathered dinosaurs are similar to birds, and we can estimate their color. Credit: Li et al. (authors).
Journal reference: Nature, DOI: 10.1038/nature12973

dendroica:

Coloured feathers readied first birds for take off

Before the first birds could take flight, they needed a lift from an unexpected source: colourful feathers. As well as giving birds the most colourful plumage on earth, it seems pigment factories in their feathers primed their feathery dinosaur ancestors for flight by creating feathers of many different shapes. The same pigment factories may also have turbocharged the proto-birds’ metabolism, helping them into the air.

This insight comes from a study of cellular pigment factories called melanosomes from the feathers, hairs and skin of 181 living birds, mammals and reptiles, plus 13 fossils of ancient lizards, turtles, dinosaurs and pterosaurs.

Julia Clarke of the University of Texas at Austin and her colleagues found that melanosomes suddenly became much more diverse in the lineage leading to birds. This happened at the same time that feather-like appendages appeared in maniraptoran dinosaurs, the forerunners of birds. These “pinnate” feathers resembled the familiar branched structure of modern bird feathers, and contained vastly more diverse melanosomes, in terms of their length, width and shape than the samples from ancient lizards and dinosaurs….

But it’s not just about feathers. The melanosome diversity explosion may also have led to higher metabolic rates in the forerunners of birds. Such rapid metabolisms are essential for powered flight.

"Many of the genes involved in the melanin colour system are also involved in other core processes such as food intake, stress responses, reproductive behaviour and more," says Clarke. That means the change in pigment could be linked to larger changes in the animals’ energetics and physiology.

This is corroborated by the modern animals, where melanosome diversity is linked to metabolism. “Only in living warm-blooded terrestrial vertebrates which independently evolved higher metabolic rates did we find the melanosome diversity we also see in feathered dinosaurs,” says Clarke.

(via New Scientist)

Photo: Analysis for the distribution of shapes of melanin-containing organelles (melanosomes) in fossil and living amniotes shows that fuzz-covered dinosaurs like Sinosauropteryx share similarities with living lizards, turtles and crocodilians. In these living taxa color and the shape of the melanosomes are not linked in such a way that color can be reconstructed from melanosome shape alone. Melanosomes in Sinosauropteryx don’t presently tell us if this animal was brown, blackish or grey. However, feathered dinosaurs are similar to birds, and we can estimate their color. Credit: Li et al. (authors).

Journal reference: Nature, DOI: 10.1038/nature12973

rhamphotheca

rhamphotheca:

The Trees That Miss The Mammoths

Trees that once depended on animals like the wooly mammoth for survival have managed to adapt and survive in the modern world.

by Whit Bronaugh

Warning: Reading this article may cause a whiplash-inducing paradigm shift. You will no longer view wild areas the same way. Your concepts of “pristine wilderness” and “the balance of nature” will be forever compromised. You may even start to see ghosts.

Consider the fruit of the Osage-orange, named after the Osage Indians associated with its range. In the fall, Osage-orange trees hang heavy with bright green, bumpy spheres the size of softballs, full of seeds and an unpalatable milky latex. They soon fall to the ground, where they rot, unused, unless a child decides to test their ballistic properties.

Trees that make such fleshy fruits do so to entice animals to eat them, along with the seeds they contain. The seeds pass through the animal and are deposited, with natural fertilizer, away from the shade and roots of the parent tree where they are more likely to germinate. But no native animal eats Osage-orange fruits. So, what are they for? The same question could be asked of the large seed pods of the honeylocust and the Kentucky coffeetree.

To answer these questions and solve the “riddle of the rotting fruit,” we first need to go to Costa Rica. That is where tropical ecologist Dan Janzen of the University of Pennsylvania noticed that the fruits of a mid-sized tree in the pea family called Cassia grandis were generally scorned by the native animals, but gobbled up by introduced horses and cattle. Janzen, who received the Crafoord Prize (ecology’s version of the Nobel) for his work on the co-evolution of plants and animals, had the idea that the seeds of Cassia grandis, and about 40 other large-fruited Costa Rican trees, were adapted to be dispersed by large mammals that are now extinct. He teamed up with Paul Martin, a paleoecologist at the University of Arizona, to develop the concept of ecological anachronisms…

(read more: American Forests)

images: mammoth/mastodon reconstruction by Dantheman9758 | Wikipedia; fossil photo by Wolfmansf | Wiki; plant photos by Mark Wells and Dxlinh

mad-as-a-marine-biologist

griseus:

CONVERGENT EVOLUTION: BATS AND DOLPHINS EVOLVED ECHOLOCATION IN THE SAME WAY

Elizabeth Pennisi / Science Mag

Dolphins and bats don’t have much in common, but they share a superpower: Both hunt their prey by emitting high-pitched sounds and listening for the echoes. Now, a study shows that this ability arose independently in each group of mammals from the same genetic mutations. The work suggests that evolution sometimes arrives at new traits through the same sequence of steps, even in very different animals. The research also implies that this convergent evolution is common—and hidden—within genomes, potentially complicating the task of deciphering some evolutionary relationships between organisms. Two kinds of bats and toothed whales, a group that includes dolphins and certain whales, that have converged on a specialized hunting strategy called echolocation. Until recently, biologists had thought that different genes drove each instance of echolocation and that the relevant proteins could change in innumerable ways to take on new functions.

But in 2010, Stephen Rossiter, an evolutionary biologist at Queen Mary, University of London, and his colleagues determined that both types of echolocating bats, as well as dolphins, had the same mutations in a particular protein called prestin, which affects the sensitivity of hearing. Looking at other genes known to be involved in hearing, they and other researchers found several others whose proteins were similarly changed in these mammals.

The discovery that molecular convergence can be widespread in a genome is “bittersweet,” Castoe adds. Biologists building family trees are likely being misled into suggesting that some organisms are closely related because genes and proteins are similar due to convergence, and not because the organisms had a recent common ancestor. No family trees are entirely safe from these misleading effects, Castoe says. “And we currently have no way to deal with this.”

rhamphotheca
rhamphotheca:

700,000 Year Old Horse Becomes Oldest Animal To Have its Genome Sequenced
A genome sequence derived from a 700,000-year-old horse fossil (inset) sheds new light on equine evolution and confirms that Przewalski’s horse (pictured) is indeed genetically distinct from domesticated breeds.
by Gisela Telis
Scientists have sequenced the oldest genome to date—and shaken up the horse family tree in the process. Ancient DNA derived from a horse fossil that’s between 560,000 and 780,000 years old suggests that all living equids—members of the family that includes horses, donkeys, and zebras—shared a common ancestor that lived at least 4 million years ago, approximately 2 million years earlier than most previous estimates. The discovery offers new insights into equine evolution and raises the prospect of recovering and exploring older DNA than previously thought possible…
(read more: Science NOW/AAAS)
images:  Claudia Feh/Association pour le cheval de Przewalski, France; (inset) Ludovic Orlando

rhamphotheca:

700,000 Year Old Horse Becomes Oldest Animal To Have its Genome Sequenced

A genome sequence derived from a 700,000-year-old horse fossil (inset) sheds new light on equine evolution and confirms that Przewalski’s horse (pictured) is indeed genetically distinct from domesticated breeds.

by Gisela Telis

Scientists have sequenced the oldest genome to date—and shaken up the horse family tree in the process. Ancient DNA derived from a horse fossil that’s between 560,000 and 780,000 years old suggests that all living equids—members of the family that includes horses, donkeys, and zebras—shared a common ancestor that lived at least 4 million years ago, approximately 2 million years earlier than most previous estimates. The discovery offers new insights into equine evolution and raises the prospect of recovering and exploring older DNA than previously thought possible…

(read more: Science NOW/AAAS)

images:  Claudia Feh/Association pour le cheval de Przewalski, France; (inset) Ludovic Orlando

scientificillustration
scientificillustration:

Evolutionary Developmental Model for the Origin of the Turtle Shell
“Results of a phylogenetic analysis of shelled reptiles and characters important in constructing a shell are plotted against the ontogeny of pleurodire turtles. Thin sections through turtle embryos show the initial outgrowth of (sub)dermal bone through the costals first (carapace length [CL] = 13.0mm in the pleurodire Emydura subglobosa) and then the neurals (CL = 18.0 mm in the pleurodire Pelomedusa subrufa). The timing of ontogenetic transformations of those features (in red) important in the construction of the shell (i.e., the number of dorsal vertebrae or ribs does not change through ontogeny) is congruent with the phylogenetic transformation of those same features based on our recovered tree topology. Our model makes explicit morphological and histological predictions for the lineage prior to the most recent common ancestor of Eunotosaurus africanus and turtles that are met by the morphology found in Milleretta rubidgei. Numbers above each node represent bootstrap frequencies obtained in the phylogenetic analysis.”
Evolutionary Origin of the Turtle Shell Lyson, Tyler R.; Bever, Gabe S.; Scheyer, Torsten M.; Hsiang, Allison Y.; Gauthier, Jacques A. Current biology : CB doi:10.1016/j.cub.2013.05.003 
See also:
How the turtle got its unique hard shell
http://news.yale.edu/2013/05/30/how-turtle-got-its-shell

scientificillustration:

Evolutionary Developmental Model for the Origin of the Turtle Shell

“Results of a phylogenetic analysis of shelled reptiles and characters important in constructing a shell are plotted against the ontogeny of pleurodire turtles. Thin sections through turtle embryos show the initial outgrowth of (sub)dermal bone through the costals first (carapace length [CL] = 13.0mm in the pleurodire Emydura subglobosa) and then the neurals (CL = 18.0 mm in the pleurodire Pelomedusa subrufa). The timing of ontogenetic transformations of those features (in red) important in the construction of the shell (i.e., the number of dorsal vertebrae or ribs does not change through ontogeny) is congruent with the phylogenetic transformation of those same features based on our recovered tree topology. Our model makes explicit morphological and histological predictions for the lineage prior to the most recent common ancestor of Eunotosaurus africanus and turtles that are met by the morphology found in Milleretta rubidgei. Numbers above each node represent bootstrap frequencies obtained in the phylogenetic analysis.”

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

See also:

How the turtle got its unique hard shell

http://news.yale.edu/2013/05/30/how-turtle-got-its-shell

rhamphotheca

rhamphotheca:

Salamander DNA reveals evidence of older land connection between Central and South America

by Smithsonian staff

The two continents are generally believed to have been joined together around three million years ago by the formation of a land bridge–what is now Panama–that sealed up the sea channel between them.

However, a new study of salamanders in South America by a research team lead by Kathryn Elmer of the University of Glasgow, has found evidence that challenges these assumptions and supports a controversial claim by Carlos Jaramillo, a paleontologist at the Smithsonian Tropical Research Institute in Panama, that most of the Isthmus of Panama was formed around 23 million years ago.

The fusion of both land masses led to a two-way migration of animals called the ‘Great American Biotic Interchange’, where animals that had previously evolved separately moved between the two continents, increasing the biodiversity in both regions.

The relative dearth of species of salamander in South America–around 30–compared to Central America, where there are more than 300 species, is usually attributed to the relatively short time the tiny amphibians have had to make their way south down the Isthmus of Panama–a thin strip of land only 30 miles wide at its narrowest point.

However, using DNA analysis, Elmer found that salamanders in South America had much greater genetic divergence from their Central American cousins than should be expected if salamanders migrated across a three- million-year-old land bridge…

(read more: Smithsonian Science)

(photos: T - Bolitoglossa sp. in the upper Amazon basin by Santiago Ron; B - B. peruviana by Kristiina Ovaska)

source: Carlos Jaramillo - Univ. of Glasgow

queensimia

biomedicalephemera:

aspidelaps:

biomedicalephemera:

The Juvenile Hoatzin (Opisthocomus hoazin)

It should first be noted that all birds are dinosaurs (order Saurischia, clade Theropoda), not just descendents of dinosaurs - modern genetic analysis strongly supports this cladistic organization. But given what we’re too often taught in schools, birds and dinosaurs are hard to reconcile in many peoples’ minds.

The juvenile hoatzin, however, makes it easy to see the reptilian traits that once dominated the early birds, and displays the unused genetic codes that lurk in the genome of modern avians. When they hatch, they’re equipped with lizard-like claws in front of their wings. Their use is described here, but in short, they use them to return to their nest and avoid predators. Their claws disappear by the time they leave the nest, having grown together into the metacarpals that support the wing structure.

Another fascinating trait of the hoatzins is their vegetarianism and their digestive tract. They have gut flora and fermentation similar to ruminants, which no other bird has. This is actually what leads to their being called “stink birds” - they exude a lot of stench with the fermentation process. The gut fermentation is so important to the hoatzin that the flight muscles attached to their keel are significantly reduced, to allow for more space for the stomach. They are weak flyers because of this. After a large meal, an adult hoatzin can spend up to two days doing almost nothing, allowing the leaves and greenery to have their nutrients released by their symbiotic gut flora.

Images:

Top: Attitudes of the juvenile hoatzin while climbing
Second row, left: Hoatzin nest with two eggs - Note proximity to water
Second row, right: Two hoatzin chicks preparing to dive, after appearance of threat from above
Third row, left: Hoatzin chick demonstrating strong swimming abilities
Third row, right: Hoatzin chick demonstrating poor locomotion on land
Bottom: Detail of hoatzin chick climbing, using neck, feet, and claws.

Tropical Wild Life in British Guinea, Vol 1. Curated by William Beebe, 1898.

It should be noted that the claws of Hoatzin are not actually simply because they are related to dinosaurs. Their claws actually re-evolved independently - they are not evolutionary leftovers at their core. While it could be considered a re-appearing gene because of their evolutionary history, it’s still something that would have to be selected over time and could have vanished again just as easily, not to mention it’s very unlikely (and impossible to prove) that it is the exact genome coming out of dormancy.

It’s more similar to dinosaurs when one thinks about convergent evolution than when one thinks about descendence, even if they are descendents too.

All of this is true, but I still like the hoatzin as an example of how to start to show people how birds really *are* dinosaurs - it’s a concept that many people don’t even begin to accept easily.

Hoatzin claws aren’t so much elongated talons-turned-wings like the Archaeopteryx seems to have, as they are a set of hooks on the front of a “chicken wing” structure. Note too, that Archaeopteryx and the hoatzin are not closely related at all (also the archaeopteryx may not even be a bird or bird relative/ancestor, but that’s a whole different matter).

Either way, the hoatzin (btw, if anyone’s wondering, that’s basically pronounced “Watsin”) is an interesting bird. The morphological changes in the wing bones as it matures are interesting enough, but the fact that it’s got such a weird digestive system are what really intrigue me.

It should be noted that while the hoatzin is a poor flyer, it’s not because it’s “primitive” or anything - it’s completely because they have a huge gut, and smaller flight muscles because of that. While their gut is a characteristic that some pretty ancient ancestors of theirs had (at least back to the Eocene), the species as a whole isn’t some evolutionary throwback, like some of the Crocodilians. The “hook-hands” of the hoatzin are relatively recent developments, as was noted. But their morphological similarities to the extinct Therapods still helps to remind people that dinosaurs and birds aren’t so different, after all.

scientificillustration
scientificillustration:

“A phylogenetic blueprint for a modern whale (Balaenoptera musculus). The topology traces the inferred evolutionary history of an extant cetacean based on results summarized in Figs. 7–9 and Table 1. Changes extend back to the base of Artiodactyla (A–D). The long sequence of character transformations on the stem lineage to crown Cetacea (branches E–O), on the stem lineage to crown Mysticeti (branches a–f), and within crown Mysticeti (branches g–h) has culminated in the extant blue whale. A subset of the changes on these internal branches (Table 1) are marked by colored circles that indicate the internode where each character evolved and, when applicable, the approximate anatomical position of each derived character state (delayed transformation optimization): B-1 = three primary lung bronchi and multi-chambered stomach, B-2 = fibro-elastic penis with sparse cavernous tissue, C-1 = sparse hair, sebaceous glands absent, and transition to freshwater, C-2 = scrotum absent, can give birth underwater, and can nurse underwater, D = involucrum (thickening of medial wall of auditory bulla), E = robust tail, F–G = transition to saltwater, G = incisive foramina absent and vomeronasal organ inferred absent, H = short cervical (neck) vertebrae, K = posterior positioning of nasal aperture, L = no articulation between vertebrae and pelvis (sacroiliac joint absent), M1 = very short hindlimbs, M2 = tail flukes inferred present, O-1 = external ears absent, O-2 = immobile elbow joint, O-3 = sweat glands absent, a = broad rostrum, b = thin lateral margins of maxillae, c-1 = lateral nutrient foramina on palate and baleen inferred present, c-2 = unsutured mandibular symphysis, d = no teeth in adults, e-1 = telescoping of skull (anterior extension of occipital shield), e-2 = bowed mandibles, g-1 = fibrous temporomandibular joint, g-2 = muscle of tongue reduced (predominantly connective tissue) and ventral throat pouch with numerous grooves, h = enormous body size. Branch lengths are not proportional to time. Artwork is by Carl Buell. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)”
A phylogenetic blueprint for a modern whale. Gatesy J, Geisler JH, Chang J, Buell C, Berta A, Meredith RW, Springer MS, McGowen MR. Mol Phylogenet Evol. 2012 Oct 26. pii: S1055-7903(12)00418-6. doi: 10.1016/j.ympev.2012.10.012. (pdf) 

scientificillustration:

“A phylogenetic blueprint for a modern whale (Balaenoptera musculus). The topology traces the inferred evolutionary history of an extant cetacean based on results summarized in Figs. 7–9 and Table 1. Changes extend back to the base of Artiodactyla (A–D). The long sequence of character transformations on the stem lineage to crown Cetacea (branches E–O), on the stem lineage to crown Mysticeti (branches a–f), and within crown Mysticeti (branches g–h) has culminated in the extant blue whale. A subset of the changes on these internal branches (Table 1) are marked by colored circles that indicate the internode where each character evolved and, when applicable, the approximate anatomical position of each derived character state (delayed transformation optimization): B-1 = three primary lung bronchi and multi-chambered stomach, B-2 = fibro-elastic penis with sparse cavernous tissue, C-1 = sparse hair, sebaceous glands absent, and transition to freshwater, C-2 = scrotum absent, can give birth underwater, and can nurse underwater, D = involucrum (thickening of medial wall of auditory bulla), E = robust tail, F–G = transition to saltwater, G = incisive foramina absent and vomeronasal organ inferred absent, H = short cervical (neck) vertebrae, K = posterior positioning of nasal aperture, L = no articulation between vertebrae and pelvis (sacroiliac joint absent), M1 = very short hindlimbs, M2 = tail flukes inferred present, O-1 = external ears absent, O-2 = immobile elbow joint, O-3 = sweat glands absent, a = broad rostrum, b = thin lateral margins of maxillae, c-1 = lateral nutrient foramina on palate and baleen inferred present, c-2 = unsutured mandibular symphysis, d = no teeth in adults, e-1 = telescoping of skull (anterior extension of occipital shield), e-2 = bowed mandibles, g-1 = fibrous temporomandibular joint, g-2 = muscle of tongue reduced (predominantly connective tissue) and ventral throat pouch with numerous grooves, h = enormous body size. Branch lengths are not proportional to time. Artwork is by Carl Buell. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)”

A phylogenetic blueprint for a modern whale. Gatesy J, Geisler JH, Chang J, Buell C, Berta A, Meredith RW, Springer MS, McGowen MR. Mol Phylogenet Evol. 2012 Oct 26. pii: S1055-7903(12)00418-6. doi: 10.1016/j.ympev.2012.10.012. (pdf