Top Story: May 6, 2014

Incredibly (Successful) Shrinking Dinosaurs

dinosaurs, maniraptoran, birds, size, evolution, adaptation

By Molly Michelson

Change. While it may be difficult in the workplace, in life it’s essential. Or at least that’s what evolution teaches us. And a paper published today in the open-access journal PLOS Biology demonstrates this clearly with dinosaur design. The dinosaur lineage that continues on today changed in one evidently successful way: size.

“Dinosaurs aren’t extinct; there are about 10,000 species alive today in the form of birds. We wanted to understand the evolutionary links between this exceptional living group, and their Mesozoic relatives, including well-known extinct species like T. rex, Triceratops and Stegosaurus,” says Roger Benson of Oxford University, who led the study. “We found exceptional body mass variation in the dinosaur line leading to birds, especially in the feathered dinosaurs called maniraptorans. These include Velociraptor, birds, and a huge range of other forms, weighing anything from 15 grams to 3 tonnes, and eating meat, plants, and more omnivorous diets.”

The team examined rates of body size evolution on the entire family tree of dinosaurs, sampled throughout their first 160 million years on Earth. If close relatives were fairly similar in size, then evolution was probably quite slow; conversely, if they were very different in size, it implies that evolution was fast.

The results show that the maniraptoran lineage kept experimenting with different, often radically smaller, body sizes—enabling new body ‘designs’ and adaptations to arise more rapidly than among larger dinosaurs. Other dinosaur groups failed to do this, got locked in to narrow ecological niches, and ultimately went extinct.

In an accompanying article, Daniel Moen and Hélène Morlon of the Ecole Normale Supérieure in Paris, who are not connected with the study, write, “What explains why some groups of organisms, like birds, are so species rich? And what explains their extraordinary ecological diversity, ranging from large, flightless birds, to small migratory species that fly thousands of kilometers every year? [Benson and colleagues] find that body-size evolution did not slow down in the lineage leading to birds, hinting at why birds survived to the present day and diversified. This paper represents one of the most convincing attempts at understanding deep time adaptive radiations.”

Image: FunkMonk (Michael B. H.)/Wikipedia


  • Ulises

    But, is there evolution if there is no time? How does evolutionary biology meet new physical paradigms about time, space and so on? Will new conceptual changes deny evolution? Or on the contrary, will it become a more extraordinary process, full of astonishing implications? If so, will dinosaurs and past human beings and the rest of living beings become different as science progresses? After all, is life something fix-finite-defined? That is, can one understand it by means of using a brain and its limited words? Does the whole of life fit into a bone box? Indeed, will science add indefinitely without understanding completely? Anyway, is it possible to understand something completely? Along these lines, there is a different book, a preview in Just another suggestion in order to free-think for a while

  • The Living Past

    To answer your questions, no, punctuated equilibrium, no, no, Dinosaurs certainly are changing as they are studied more, yes, no, yes, and no. Good questions though.

  • roberta4343

    and you know this how? when and how did the dinos become warm blooded, lighter than air, and grow feathers have soft skin develop complex nesting and nest building instincts and develop a four chambered heart from a three chambered dino heart? and how do you know what their physical makeup was beyond the bones? where is your evidence? so I am going to take that this is just your opinion, wishful thinking on your part. you do your science no good by pretending you have solid evidence on something when you don’t. science used to be a love of mine when young but as I have grown up and see the flaws, dishonesty, money grabbing, headline shooting, and personal agendas running, and totally fabrication of evidence/speculation without disclaimer for the public. all sciences have lost credibility to me, including the medical sciences, social sciences, political sciences, economic sciences etc. why are people so determined for evolution to be true? I have seen attempts at making it so by bold statements and use of authority to stifle disagreements in the public forum.(especially by climatologists) yet the more science tries to make evolution fact the more credibility they lose. sooner or later people figure out much of what they thought were true to find out later they were lied to. when scientists keep objective they go a lot further in increasing our knowledge of the universe but when they try to outshine others gain financial gains or politics gets into it look out the world will sink from all the flooding from lies/dishonesty. by the way I dig dinosaurs, ancient creatures, I do believe they existed and I find them fascinating. how they generally looked and maybe walked seems solid enough maybe even the timeline might be correct or that might be speculation, no matter just asking you guys to be honest in all things and don’t pretend something is true when it is not. thanks. by the way I still love science it is the people I don’t trust who are running it.

  • antiquatedtory

    I was thinking someone should answer this, and I found this fine passage from the Science of Doom blog:

    Argument from Inconceivability

    I personally find it hard to believe that we are hurtling through space at 67,000 miles per hour on a big spinning rock. It doesn’t feel like it. (Actually that’s just the speed that we orbit the sun, and the sun is moving as well, so its more complicated..)

    And is this table (you can’t see my table, but any table will do) really made of tiny atoms but science claims it’s mostly space between the little balls? What? Not likely.

    Satire over.

    For science, personal experience and imagination are not the deciding factors. They lead you astray. Instead, investigation of phenomena lead to hypotheses, experiments and eventually “theories” – as well-established science “facts” are known. Your intuition might be great for understanding people’s motivations, or whether a person can run 100m in 3 seconds, but not so great for the energy absorption characteristics of invisible molecules.

Previous Top Stories


About Science Today

Science Today is the California Academy of Sciences’ channel for current stories on cutting-edge technologies, life, Earth, space and sustainability. Content is produced in-house and is distributed throughout the museum, on the internet and through various partners. Please share your comments on what you find important in the changing world of science.