An anatomical diagram of a hypothetical ancestral mollusc.
Its nervous system is hypoathroid. Throughout its unsegmented, bilaterally symmetrical body, organs occur either singly or in pairs; there is no metamerism. Its hemocoel circulatory system is filled with hemocyanin. Gametes are ejected into the pericardium before traveling through the nephridia to environment.
 Diagram illustration by K.D. Schroeder
(via: Wikipedia)

An anatomical diagram of a hypothetical ancestral mollusc.

Its nervous system is hypoathroid. Throughout its unsegmented, bilaterally symmetrical body, organs occur either singly or in pairs; there is no metamerism. Its hemocoel circulatory system is filled with hemocyanin. Gametes are ejected into the pericardium before traveling through the nephridia to environment.

Diagram illustration by K.D. Schroeder

(via: Wikipedia)

Ability to Regenerate Limbs/Digits Dates Back at Least 300 Million Years

by Ian Randall

Researchers have found the earliest evidence for limb regeneration in the fossil record. Rocks unearthed in southwestern Germany have captured 300-million-year-old amphibians that have one or more regrown limbs.

Unlike humans—who can only replace lost fingertips—salamanders are the only modern four-legged animals, or tetrapods, that maintain the ability to regenerate entire limbs throughout their lives. If tissue has been severely damaged or if the wound heals poorly, however, the regrown limb may grow back incorrectly. Such deformities can be quite common, especially if the same limb is repeatedly amputated or injured, leading to regenerated limbs with extra, missing, or fused-together digits in distinctive and unique patterns.

In their new paper, published online today in the Proceedings of the Royal Society B, the researchers report identifying these same types of deformity in exceptionally well preserved fossils of the early amphibian, Micromelerpeton (pictured, with an extra, partly fused digit, second from the top)…

(read more: Science News/AAAS)

images: Ghedoghedo and Kai Nungesser

Triassic Bites and a Carnivore Conundrum

by Brian Switek

The Triassic was one of the strangest times in the history of the planet. Rebounding from the worst mass extinction of all time, life flourished into startling new varieties, including the first dinosaurs, weird marine reptiles, and croc-line critters that came in forms like “armadillodiles” and huge, jagged-toothed carnivores, to name just a few Triassic stars. But the strange nature of the Triassic extends beyond the odd anatomy of the creatures that evolved during the period.

While paleontologists are still piecing together the details of Triassic life for the early parts of the period, researchers know that the landscapes of the Late Triassic were dominated by carnivores. At many classic Late Triassic localities – such as those in Petrified Forest National Park and Ghost Ranch, New Mexico – flesh-eaters outnumber herbivores in both abundance and species diversity.

This doesn’t fit with the classic ecosystem pyramid we learn in grade school, with a greater number of herbivores providing fodder for a small number of carnivores. No, something strange was going on during the Late Triassic, and a pair of damaged leg bones may hint at why the Late Triassic held an embarrassment of predators.

The two bones, studied by paleontologists Stephanie Drumheller, Michelle Stocker, and Sterling Nesbitt, were found in different localities at different times. But they have three important features in common. They both belong to large Late Triassic carnivores called paracrocodylomorphs, both are upper leg bones called femora, and both are pocked by bitemarks from different carnivores…

(read more: Laelaps blog - National Geographic)

images: Brian Switek; Drumheller et al. 2014

palaeopedia
palaeopedia:

The trident tooth, Thrinaxodon (1894)
Phylum : ChordataClass : SynapsidaOrder : TherapsidaSuborder : CynodontiaFamily : ThrinaxodontidaeGenus : ThrinaxodonSpecies : T. liorhinus
Early Triassic (248 - 245 Ma)
50 cm long and 2 kg (size)
South Africa and Antarctica (map)
Thrinaxodon probably lived in shallow burrows dug into hillsides or riverbanks.
A low-slung, sharp-toothed carnivore, Thrinaxodon lived in burrows, and its well-differentiated teeth suggest it ate small creatures like insects, reptiles, and other small animals. Clues to its remains show that this creature was more mammal-like than its synapsid ancestors.
It had a fairly large head/skull with pits in the snout area which have suggested to some that it had whiskers, but the modern lizard Tupinambis has pits in the same area that are almost identical. An enlarged dentary bone strengthened either side of the lower jaw and contained sockets for its teeth.
Along with other cynodonts, Thrinaxodon could chew and breathe at the same time, due to the evolutionary development of the secondary palate. Its chest and lower back regions were probably separated by a diaphragm - a muscular sheet that contracted to fill lungs, and would have enabled Thrinaxodon to breathe more efficiently than its ancestors.
In response to the wide daily temperature swings of the early Triassic, it may have been eurythermic, able to function at a broad range of temperatures; this could have laid the groundwork for the development of homeothermic endothermy. Like its predecessors, Thrinaxodon laid eggs, and there were many reptilian features in its skeleton.

palaeopedia:

The trident tooth, Thrinaxodon (1894)

Phylum : Chordata
Class : Synapsida
Order : Therapsida
Suborder : Cynodontia
Family : Thrinaxodontidae
Genus : Thrinaxodon
Species : T. liorhinus

  • Early Triassic (248 - 245 Ma)
  • 50 cm long and 2 kg (size)
  • South Africa and Antarctica (map)

Thrinaxodon probably lived in shallow burrows dug into hillsides or riverbanks.

A low-slung, sharp-toothed carnivore, Thrinaxodon lived in burrows, and its well-differentiated teeth suggest it ate small creatures like insects, reptiles, and other small animals. Clues to its remains show that this creature was more mammal-like than its synapsid ancestors.

It had a fairly large head/skull with pits in the snout area which have suggested to some that it had whiskers, but the modern lizard Tupinambis has pits in the same area that are almost identical. An enlarged dentary bone strengthened either side of the lower jaw and contained sockets for its teeth.

Along with other cynodonts, Thrinaxodon could chew and breathe at the same time, due to the evolutionary development of the secondary palate. Its chest and lower back regions were probably separated by a diaphragm - a muscular sheet that contracted to fill lungs, and would have enabled Thrinaxodon to breathe more efficiently than its ancestors.

In response to the wide daily temperature swings of the early Triassic, it may have been eurythermic, able to function at a broad range of temperatures; this could have laid the groundwork for the development of homeothermic endothermy. Like its predecessors, Thrinaxodon laid eggs, and there were many reptilian features in its skeleton.

Shattering DNA May Have Let Gibbons Evolve New Species
by Colin Barras
Gibbons have such strange, scrambled DNA, it looks like someone has taken a hammer to it. Their genome has been massively reshuffled, and some biologists say that could be how new gibbon species evolved.
Gibbons are apes, and were the first to break away from the line that led to humans. There are around 16 living gibbon species, in four genera. They all have small bodies, long arms and no tails. But it’s what gibbons don’t share that is most unusual. Each species carries a distinct number of chromosomes in its genome: some species have just 38 pairs, some as many as 52 pairs.
"This ‘genome plasticity’ has always been a mystery," says Wesley Warren of Washington University in St Louis, Missouri. It is almost as if the genome exploded and was then pieced back together in the wrong order.
To understand why, Warren and his colleagues have now produced the first draft of a gibbon genome. It comes from a female northern white-cheeked gibbon (Nomascus leucogenys) called Asia…
(read more: New Scientist)
image: Heather Angel/Natural Visions

Shattering DNA May Have Let Gibbons Evolve New Species

by Colin Barras

Gibbons have such strange, scrambled DNA, it looks like someone has taken a hammer to it. Their genome has been massively reshuffled, and some biologists say that could be how new gibbon species evolved.

Gibbons are apes, and were the first to break away from the line that led to humans. There are around 16 living gibbon species, in four genera. They all have small bodies, long arms and no tails. But it’s what gibbons don’t share that is most unusual. Each species carries a distinct number of chromosomes in its genome: some species have just 38 pairs, some as many as 52 pairs.

"This ‘genome plasticity’ has always been a mystery," says Wesley Warren of Washington University in St Louis, Missouri. It is almost as if the genome exploded and was then pieced back together in the wrong order.

To understand why, Warren and his colleagues have now produced the first draft of a gibbon genome. It comes from a female northern white-cheeked gibbon (Nomascus leucogenys) called Asia…

(read more: New Scientist)

image: Heather Angel/Natural Visions

Chisel-toothed Creature Pushes Back Origin of Mammals

Jurassic skeletons show that early mammals didn’t just hide in the undergrowth.

by Brian Switek

Squirrel-size mammals scampered through the trees above dinosaurs’ heads, newfound Chinese fossils show, revising our image of the first furry beasts. Three newly described species suggest that mammals evolved earlier, and faster, than previously thought.

Called haramiyids, the recently discovered mammals lived in Jurassic China around 160 million years ago. Slender and graceful, the animals appear to have been specialized for life in the trees, with hands and feet that could grasp branches and a long prehensile tail like today’s monkeys.

"The picture that Mesozoic mammals were shrew-like insectivores that lived in the shadow of the dinosaurs needs to be repainted," says American Museum of Natural History paleontologist Jin Meng, a coauthor of the new study. Discoveries during the past few decades, including the haramiyids, have shown that early mammals occupied a variety of habitats. “They walked on the ground; they also swam, dug to burrow, and glided in the forests,” Meng says…

(read more: National Geographic)

Photograph by Jin Meng; Illustration by Zhao Chuang

The evolutionary tree for modern humans a bit of a mess - humans haven’t had a close relative on this planet for over 10,000 years, but there used to be several other closely related species living at the same time.

Genetic analyses on bone fragments from Neanderthals and Denisovans has given us new insight into our not-so-distant evolutionary past. The results indicate that not only did Denisovans and Neanderthals interbreed with modern Homo sapiens, but they also mated with an unidentified fourth hominin group…

Fish Out of Water Learn to Walk

Around 400 million years ago, fish left the water and started to evolve into land-loving creatures. But how did the transition happen? A new and unusual experiment could shed some light on the kinds of changes that enabled fins to become limbs. Researchers took a fish species known to be able to walk on its fins from time to time, and raised it on land. Watch the fish promenade in this Nature Video.

Read the paper: http://dx.doi.org/10.1038/nature13708

Read the News & Views: http://dx.doi.org/10.1038/nature13743

STORIES I CANT STOP POSTING ABOUT:
If A Fish Grows Up On Land, Will It Learn To Walk?
Flipping your fins actually does get you pretty far.
by Lauren Grush
The old idiom about “being a fish out of water” just lost some of its luster. Researchers from McGill University in Canada successfully trained a group of fish to live on land and strut around.
The idea was to simulate what might have happened 400 million years ago, when the first group of ancient fish moved from water to land, eventually evolving into the amphibians, reptiles, birds and other animals roaming the Earth today. The researchers wanted to see if their land-dwelling fish looked and behaved similarly to the ancient fish, based on what has been learned about them from fossil records.
For their experiment, the research team raised 111 juvenile Polypterus senegalus – African fish also known as the “dinosaur eel” — on land. These fish already look a lot like the ancient fish that evolved millions of years ago, and they’re already capable of “walking” with their fins and breathing air.  According to the Verge, their terrestrial environment had mesh flooring covered in pebbles, as well as 3 millimeters of water, so the fish didn’t dry out completely…
(read more/ watch video: Popular Science)
photo: NATURE

STORIES I CANT STOP POSTING ABOUT:

If A Fish Grows Up On Land, Will It Learn To Walk?

Flipping your fins actually does get you pretty far.

by Lauren Grush

The old idiom about “being a fish out of water” just lost some of its luster. Researchers from McGill University in Canada successfully trained a group of fish to live on land and strut around.

The idea was to simulate what might have happened 400 million years ago, when the first group of ancient fish moved from water to land, eventually evolving into the amphibians, reptiles, birds and other animals roaming the Earth today. The researchers wanted to see if their land-dwelling fish looked and behaved similarly to the ancient fish, based on what has been learned about them from fossil records.

For their experiment, the research team raised 111 juvenile Polypterus senegalus – African fish also known as the “dinosaur eel” — on land. These fish already look a lot like the ancient fish that evolved millions of years ago, and they’re already capable of “walking” with their fins and breathing air.  According to the Verge, their terrestrial environment had mesh flooring covered in pebbles, as well as 3 millimeters of water, so the fish didn’t dry out completely…

(read more/ watch video: Popular Science)

photo: NATURE

griseus

griseus:

USING LIVING FISH TO STUDY ANCIENT EVOLUTIONARY CHANGES: How plasticity works in evolution race

Ambitious experimental and morphological studies of a modern fish show how developmental flexibility may have helped early ‘fishapods’ to make the transition from finned aquatic animals to tetrapods that walk on land.

The origin of tetrapods from their fish antecedents, approximately 400 million years ago, was coupled with the origin of terrestrial locomotion and the evolution of supporting limbs. Polypterus is a ray-finned fish (actinopterygians) and is pretty similar to elpistostegid fishes, which are stem tetrapods.

Polypterus therefore serves as an extant analogue of stem tetrapods, allowing us to examine how developmental plasticity affects the ‘terrestrialization’ of fish. How else would you find out what behavioral and physiological changes might have taken place when fish first made the move from sea to land over 400 million years ago? putting a fish walking on land…

(read more)

Study probes why humans are more cooperative than other animals

Humans are generally highly cooperative and often impressively altruistic, quicker than any other animal species to help out strangers in need. A new study suggests that our lineage got that way by adopting so-called cooperative breeding: the caring for infants not just by the mother, but also by other members of the family and sometimes even unrelated adults. In addition to helping us get along with others, the advance led to the development of language and complex civilizations, the authors say…

Skeletons of primitive fish adapt as they take to land.

When raised on land, a primitive, air-breathing fish walks much better than its water-raised comrades, according to a new study. The landlubbers even undergo skeletal changes that improve their locomotion. The work may provide clues to how the first swimmers adapted to terrestrial life…

Guiyu is an extinct genus of bony fish, and is the earliest known bony fish from the fossil record. It lived during the Late Silurian (419 million years ago) in China and was 33 cm long. It has the combination of both actinopterygian and sarcopterygian features, although analysis of the totality of its features place it closer to Sarcopterygii (lobe finned fishes).
illustration of G. oneiros by Ron Weasly
(via: Wikipedia)

Guiyu is an extinct genus of bony fish, and is the earliest known bony fish from the fossil record. It lived during the Late Silurian (419 million years ago) in China and was 33 cm long. It has the combination of both actinopterygian and sarcopterygian features, although analysis of the totality of its features place it closer to Sarcopterygii (lobe finned fishes).

illustration of G. oneiros by Ron Weasly

(via: Wikipedia)