All Yesterdays!

Everybody loves Microraptor! This one is actually a redux of one of my earlier ones, but scientifically updated. Last year some research came out about Microraptors feathering, about the arrangement of it’s tail feathers and it’s colour. We know what colour this cool little Dinosaur, and if that doesn’t blow your mind with wonderment, then I don’t have time for you.

Also flitting around in the picture are a couple Confuciusornis, Microraptors favourite prey item, but the Microraptors aren’t really paying them much attention for a change.

On Etsy

Jeholornis was a primitive bird from the Early Cretaceous of China, about 120 million years ago. They were some of the largest early birds known, reaching adult lengths of up to 80cm (2.6ft).

Several specimens have been found to preserve evidence of a frond of feathers at both the tip and the base of the tail, earning it the nickname of the “two-tailed bird”. Whether this feature served any actual aerodynamic purpose is unclear — much like modern peacocks’ and roosters’ fancy ‘tail’ feathers, it may have been a plume of modified coverts serving as a sexual display feature.

Reconstructions vary on the exact placement of the feathers. The image seen in most news articles was… awkward-looking, and many other artists have chosen to depict the feathers along the side of the tail rather than the top. I’ve put them more dorsally here, in line with the discoverers’ interpretation.

The dinosaur formerly known as Brachiosaurus brancai was possibly the best dinosaur, but try as I might, I can never do it justice. Here’s another attempt at making it look regal by having it roll around in mud. I think I may have a strategy problem here.

I haven’t been puting much work up recently because of the top secret book project sapping nearly all my painting time. I’ve been working on this Photoshop painting for ages, and I’m glad to get it out the door. I’m considering making it part of a panorama.

How small birds evolved from giant meat eating dinosaurs

By Mike Lee and Gareth Dyke, University of Southampton

Spectacular transitional fossils, many from northern China, provide overwhelming evidence that dinosaurs evolved into birds and thus didn’t all perish when the deadly meteorite struck at the end of the Cretaceous period.

We now know that many bipedal, meat-eating dinosaurs (theropods) – including relatives of T. rex and Velociraptor – were adorned with a variety of feathers. They were preserved in such detail in fine volcanic ash that often even their colours can be reconstructed. Plumage might have even been present in all dinosaurs

A study by our team published today in the journal Science sheds new light on the evolutionary journey from bulky ground-dwelling dinosaurs to agile flying birds.

Our research shows that the ancestors of birds were the only lineage of dinosaurs to continually shrink in size for an extended period of time (at least 50 million years, and perhaps twice as long). They were also the fastest-evolving lineage of dinosaurs.

Five successive ancestors leading from dinosaurs to modern birds. From left to right: the ancestral neotheropod (~220 million years old), the ancestral tetanuran (~200 myo), the ancestral coelurosaur (~175 myo), the ancestral paravian (~165 myo), and the ancestral avialan (150 myo). See movie below for animated explanation. Davide Bonadonna, Author provided

These results also relate – unexpectedly – to human health and an implausible 1980s TV show.

The incredible shrinking dinosaur

We constructed a detailed family tree for theropod dinosaurs including birds, and nutted out the evolutionary events that happened on each branch – that is, did body size increase or decrease and did any novel adaptations evolve?

For instance, if all the dinosaurs above a branch possessed a unique adaptation (such a shoulder blades fused into a bird-like wishbone), then we can infer that the wishbone evolved on that branch.

We then identified the series of successive branches leading from the very base of the dinosaur tree all the way to living birds: this is the “bird stem lineage”.

A close analogy would be taking a real tree and tracing the single path that leads from the trunk all the way to a “special” little bunch of leaves somewhere high in the crown.

A Broad-billed Hummingbird (Cynanthus latirostris) in front of a tooth of a massive dinosaurian predecessor (the six-tonne Carcharodontosaurus). Terry Sohl/Christophe Hendrickx

It turns out that the bird stem lineage – the dinosaurs on the road to becoming birds – were evolving in a noticeably different manner to other theropod lineages around at the time.

This lineage kept shrinking in size, with each successive descendant smaller than its predecessor. In contrast, in other dinosaur lineages, body size was alternately increasing and decreasing, with no sustained trend in one direction.

Another recent study further shows that body size along the bird stem lineage often changed unusually rapidly (in addition to in a coherent direction).

Taking the evolutionary lead

Evolutionary novelties were appearing on the bird stem lineage at a faster rate than across the rest of the tree. Many were major innovations such as complex feathers, bigger brains, wings and wishbones. Stem-birds were out-evolving their contemporaries by changing approximately four times as fast.

This continual and often rapid shrinking was probably directly related to the accelerated evolution of anatomical novelties.

Reduced body size, for instance, allowed bird-stem dinosaurs to explore new postures (bird-like walking where the thigh bone is held horizontal) and habitats (such as arboreal and, later, aerial habitats). This in turn would have created pressure to evolve radical new adaptations such as reshaping fluffy feathers into wings.

Perhaps the movement of small dinosaurs into trees was one reason for the appearance of gliding flight, using aerodynamic feathers?

The feathered dinosaur Microraptor preyed on a group of primitive birds (Sinornis) in Jurassic-era China. Brian Choo, CC BY-NC-SA

Small theropods with feathered arms, legs and tails – such as Microraptor and the recently-described Changyuraptor – were very likely excellent climbers, as fossils have been found with small birds in their stomachs.

Survival of the ‘MacGyver dinosaurs’

Ultimately, the dinosaurian lineage that was the most evolvable during the Mesozoic also proved to be the most long-lived (there are 10,000 species of birds still alive today).

It is not surprising that the ability to adapt rapidly is a key to long-term survival.

A timely example concerns the influenza virus in the (southern) winter. Of the many and varied flu strains circulating now, the fastest-evolving strains are more likely to outwit our immune systems and to persist and cause problems next winter.

A certain resourceful 1980s TV character fits into this picture in two ways: secret agent Angus MacGyver epitomised the ability to adapt quickly to any novel situation – just like the avian stem lineage.

But there is a more profound point of relevance. The methods we used to infer dinosaur evolutionary trees and patterns of size evolution were actually originally developed to better understand the molecular evolution and geographic spreading of viruses (such as influenza and HIV) in real time.

The intricate theory and mathematics required are virtually identical for both situations. So rather than re-invent a very complex wheel, we “MacGyvered it” by transferring the analytic tools from molecular biology over to palaeontology.

Mike Lee receives research funding from the Australian Research Council, the South Australian Museum, and the Environment Institute (University of Adelaide).

Gareth Dyke does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

This article was originally published on The Conversation. Read the original article.

Some dinosaurs were birdbrains (and that's a good thing)

By Mike Lee

Birds are some of the brainiest creatures on earth, while their direct ancestors – the dinosaurs – are often stereotyped as dull and doomed. But a new study published today in Nature challenges this notion: many dinosaurs were just as brainy as early birds, such as Archaeopteryx. With their small size and (proportionately) big brains, birds were probably dinosaurs that never grew up.

The expression “birdbrain” should be interpreted more as a compliment than an insult. Getting and staying airborne is a highly complex activity requiring finely-tuned coordination and sensory perception, which is partly why birds fill us with wonder and pilots are generally held in high esteem.

Birds accordingly have large brains with swollen cerebral hemispheres, more sophisticated than those of most creatures apart from some mammals. These big brains not only allow birds to stay aloft, but also to perform some impressive mental feats: Caledonian crows and many other birds make and use complex tools, and some resourceful blue tits learnt how to open the foil tops once used in milk bottles, then taught others across the UK this useful skill.

Great spikes – shame about the brain.

Dinosaurs, on the other hand, have long been caricatured as lumbering behemoths with tiny brains: children learn that Stegosaurus was as big as a car but had the brain the size of a walnut.

This is a bit of an exaggeration: nevertheless, the peach-sized brain in the elephant-sized Stegosaurus, or the apple-sized brain in the much larger Apatosaurus, were very unimpressive. Certainly, many dinosaurs, especially quadrapedal herbivores such as these, had relatively small, reptile-like brains.

But it is now increasingly clear that other dinosaurs were much brainier. We now know that birds (with their finely-tuned brains that help them stay aloft) evolved from bipedal carnivorous dinosaurs (theropods), so enlarged brains might be expected in some of these bird relatives. Indeed, the theropods most closely related to birds, such as the Velociraptors of Jurassic Park fame, “look” intelligent: small, agile, lightly-built predators with swollen braincases and large eyes.

Until now, though, it was generally thought even the most bird-like dinosaurs still had smaller brains than primitive birds such as Archaeopteryx, which in turn was less brainy than living birds.

Dinosaurs get a brain scan

The new study in Nature, by Amy Balanoff (palaeontologist at the American Museum of Natural History) and colleagues, has challenged this assumption.

The team examined in detail the brains of a range of theropod dinosaurs (such as Citipati shown below), Archaeopteryx, and living birds (such as the golden-fronted woodpecker shown below).

To peer inside their skulls, they used three-dimensional CT scans similar to those used in hospitals and medical laboratories. Surprisingly, many theropod dinosaurs had brains proportionately as large as those of Archaeopteryx: indeed, some were even brainier, according to measurements.

A 3D rendering from CT scans of the oviraptorosaur dinosaur Citipati osmolskae. The endocast (brain) is rendered opaque and the skull transparent. The large central hole is the orbit, and the deep snout (with large dorsal crest) faces left. Amy Balanoff, AMNH

A 3D rendering from CT scans of the living golden-fronted woodpecker, Melanerpes aurifrons. The bulging green regions are the cerebral hemispheres, which are enlarged in birds (just as in ourselves). Amy Balanoff, AMNH

Many of these bird-like dinosaurs had long stiff feathers on their arms and legs which they might have used for gliding or even flying. The presence of large brains is certainly consistent with some sort of aerial ability in these bird-like dinosaurs.

The new study adds to the mountain of evidence demonstrating that dinosaurs evolved into birds in a gradual series of changes.

Theropod dinosaurs exhibit many bird-like features, such as feathers, wishbones, and a three-toed foot. These dinosaur-bird similarities are even more impressive when we examine juvenile dinosaurs: their skulls, with typical “baby-face” features such as proportionately large eyes and brains, and small slender snouts, strongly resemble primitive birds such as Archaeopteryx.

Birds therefore evolved from a lineage of theropod dinosaurs which retained many juvenile traits (such as small size and baby-like skulls) into maturity. In this respect, human evolution might have followed a similar trajectory: we retain many traits of baby chimpanzees (our nearest living relatives) well into adulthood, such as our small jaws, flat faces, swollen brains and propensity for play.

Mike Lee does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

This article was originally published at The Conversation. Read the original article.