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)

Hallucigenia:  Worm-like creature with legs and spikes finds its place in the evolutionary tree of life
via: University of Cambridge
One of the most bizarre-looking fossils ever found - a worm-like creature with legs, spikes and a head difficult to distinguish from its tail – has found its place in the evolutionary Tree of Life, definitively linking it with a group of modern animals for the first time.
The animal, known as Hallucigenia due to its otherworldly appearance, had been considered an ‘evolutionary misfit’ as it was not clear how it related to modern animal groups. Researchers from the University of Cambridge have discovered an important link with modern velvet worms, also known as onychophorans, a relatively small group of worm-like animals that live in tropical forests. The results are published in the advance online edition of the journal Nature.
The affinity of Hallucigenia and other contemporary ‘legged worms’, collectively known as lobopodians, has been very controversial, as a lack of clear characteristics linking them to each other or to modern animals has made it difficult to determine their evolutionary home…
(read more: PhysOrg)
illustration by Elyssa Rider

Hallucigenia:  Worm-like creature with legs and spikes finds its place in the evolutionary tree of life

via: University of Cambridge

One of the most bizarre-looking fossils ever found - a worm-like creature with legs, spikes and a head difficult to distinguish from its tail – has found its place in the evolutionary Tree of Life, definitively linking it with a group of modern animals for the first time.

The animal, known as Hallucigenia due to its otherworldly appearance, had been considered an ‘evolutionary misfit’ as it was not clear how it related to modern animal groups. Researchers from the University of Cambridge have discovered an important link with modern velvet worms, also known as onychophorans, a relatively small group of worm-like animals that live in tropical forests. The results are published in the advance online edition of the journal Nature.

The affinity of Hallucigenia and other contemporary ‘legged worms’, collectively known as lobopodians, has been very controversial, as a lack of clear characteristics linking them to each other or to modern animals has made it difficult to determine their evolutionary home…

(read more: PhysOrg)

illustration by Elyssa Rider

Dinosaurs shrank for 50 million years to become birds
by Andy Coghlan
It took 50 million years of continual shrinking to turn massive, lumbering dinosaurs into the first small flying birds.
"No other dinosaur group has undergone such a long and extended period of miniaturisation," says Mike Lee of the South Australian Museum in Adelaide. “Statistically this trend was far stronger than by chance, analogous to flipping a coin a dozen times and getting all heads.”
Lee and his colleagues have performed the most comprehensive analysis yet of fossil theropods, the two-footed meat-eating dinosaurs, like Velociraptor, from which birds evolved. They have charted how 224-million-year-old dinosaurs weighing 238 kilograms evolved into proto-birds, including Archaeopteryx, that weighed just 0.8 kg.
The analysis reveals that the ancestors of birds shrank without interruption. “What was impressive was the consistency of the size change along the dinosaur-to-bird transition, with every descendant smaller than its ancestor,” says Lee. Getting smaller must have offered advantages at every turn…
(read more: New Scientist)
illustration by Davide Bonnadonna

Dinosaurs shrank for 50 million years to become birds

by Andy Coghlan

It took 50 million years of continual shrinking to turn massive, lumbering dinosaurs into the first small flying birds.

"No other dinosaur group has undergone such a long and extended period of miniaturisation," says Mike Lee of the South Australian Museum in Adelaide. “Statistically this trend was far stronger than by chance, analogous to flipping a coin a dozen times and getting all heads.”

Lee and his colleagues have performed the most comprehensive analysis yet of fossil theropods, the two-footed meat-eating dinosaurs, like Velociraptor, from which birds evolved. They have charted how 224-million-year-old dinosaurs weighing 238 kilograms evolved into proto-birds, including Archaeopteryx, that weighed just 0.8 kg.

The analysis reveals that the ancestors of birds shrank without interruption. “What was impressive was the consistency of the size change along the dinosaur-to-bird transition, with every descendant smaller than its ancestor,” says Lee. Getting smaller must have offered advantages at every turn…

(read more: New Scientist)

illustration by Davide Bonnadonna

Where Did These Hybrid Fish Come From?
by Xochitl Rojas-Rocha 



In the Calnali River in Mexico, two pure species of swordtail fish live side by side with a third population that’s a mix of the original two. Classical models of evolution predict that pure females would not mate with these hybrids, as the hybrids are considered less fit from an evolutionary perspective.
But a new study shows that’s not the case. Researchers examined the two pure swordtail species, X. birchmanni and X. malinche, as well as the hybrids, tagging the animals and extracting DNA to probe their mating patterns. They discovered that X. birchmanni and X. malinche did not mate with each other, but that females of both species mated with the hybrids.
Hybrids can therefore act as a channel for genes to flow between the pure species populations, the team will report next month in The American Naturalist. But if the two pure species can’t mate, how did the hybrids form in the first place? …
(read more: Science News/AAAS)
photo: Daniel L. Powell

Where Did These Hybrid Fish Come From?

by  

In the Calnali River in Mexico, two pure species of swordtail fish live side by side with a third population that’s a mix of the original two. Classical models of evolution predict that pure females would not mate with these hybrids, as the hybrids are considered less fit from an evolutionary perspective.

But a new study shows that’s not the case. Researchers examined the two pure swordtail species, X. birchmanni and X. malinche, as well as the hybrids, tagging the animals and extracting DNA to probe their mating patterns. They discovered that X. birchmanni and X. malinche did not mate with each other, but that females of both species mated with the hybrids.

Hybrids can therefore act as a channel for genes to flow between the pure species populations, the team will report next month in The American Naturalist. But if the two pure species can’t mate, how did the hybrids form in the first place? …

(read more: Science News/AAAS)

photo: Daniel L. Powell

Siberian Discovery Suggests Almost All Dinosaurs Were Feathered
Jurassic fossils may mean that feathers were all in the family.
by Dan Vergano
Almost all dinosaurs were probably covered in feathers, Siberian fossils of a tufted, two-legged running dinosaur dating from roughly 160 million years ago suggest.
Over the past two decades, discoveries in China have produced at least five species of feathered dinosaurs. But they all belonged to the theropod group of “raptor” dinosaurs, ancestors of modern birds. 
Now in a discovery reported by an international team in the journal Science, the new dinosaur species, Kulindadromeus zabaikalicus, suggests that feathers were all in the family. That’s because the newly unearthed 4.5-ft-long (1.5 m) two-legged runner was an “ornithischian” beaked dinosaur, belonging to a group ancestrally distinct from past theropod discoveries…
(read more: National Geographic)
illustration by Andrey Atuchin

Siberian Discovery Suggests Almost All Dinosaurs Were Feathered

Jurassic fossils may mean that feathers were all in the family.

by Dan Vergano

Almost all dinosaurs were probably covered in feathers, Siberian fossils of a tufted, two-legged running dinosaur dating from roughly 160 million years ago suggest.

Over the past two decades, discoveries in China have produced at least five species of feathered dinosaurs. But they all belonged to the theropod group of “raptor” dinosaurs, ancestors of modern birds.

Now in a discovery reported by an international team in the journal Science, the new dinosaur species, Kulindadromeus zabaikalicus, suggests that feathers were all in the family. That’s because the newly unearthed 4.5-ft-long (1.5 m) two-legged runner was an “ornithischian” beaked dinosaur, belonging to a group ancestrally distinct from past theropod discoveries…

(read more: National Geographic)

illustration by Andrey Atuchin

palaeopedia
palaeopedia:

The first whale, Protocetus (1904)
Phylum : ChordataClass : MammaliaOrder : CetaceaSuborder : ArchaeocetiFamily : ProtocetidaeGenus : ProtocetusSpecies : P. atavus
Middle Eocene (42 - 38 Ma)
2,5 m long and 100 kg (size)
Mokattam formation, Egypt (map)
Despite its name, Protocetus wasn’t technically the “first whale;” as far as we know, that honor belongs to the four-legged, land-bound Pakicetus, which lived a few million years earlier.
Whereas the dog-like Pakicetus ventured only occasionally into the water, Protocetus was much better adapted to an aquatic lifestyle, with a lithe, seal-like body and powerful front legs. Also, the nostrils of this prehistoric whale were located midway up its forehead, foreshadowing the blowholes of its modern descendants, and its ears were better adapted to hearing underwater.

palaeopedia:

The first whale, Protocetus (1904)

Phylum : Chordata
Class : Mammalia
Order : Cetacea
Suborder : Archaeoceti
Family : Protocetidae
Genus : Protocetus
Species : P. atavus

  • Middle Eocene (42 - 38 Ma)
  • 2,5 m long and 100 kg (size)
  • Mokattam formation, Egypt (map)

Despite its name, Protocetus wasn’t technically the “first whale;” as far as we know, that honor belongs to the four-legged, land-bound Pakicetus, which lived a few million years earlier.

Whereas the dog-like Pakicetus ventured only occasionally into the water, Protocetus was much better adapted to an aquatic lifestyle, with a lithe, seal-like body and powerful front legs. Also, the nostrils of this prehistoric whale were located midway up its forehead, foreshadowing the blowholes of its modern descendants, and its ears were better adapted to hearing underwater.