Cosmos
Cosmos is a quarterly science magazine. We aim to inspire curiosity in ‘The Science of Everything’ and make the world of science accessible to everyone.
By Cosmos
Dinosaurs were the dominant creatures on land for more than 150 million years.
The Mesozoic era (252–66 million years ago) is sometimes called the “Age of Dinosaurs” or “Age of Reptiles”. During this time, dinosaurs grew to be the largest land animals and biggest predators of all time.
We are endlessly amazed by these magnificent ancient beasts.
But dinosaurs shared the Earth with a plethora of other creatures. Some were equally impressive, such as the giant pterosaurs or marine reptiles. Others were more unassuming, scampering about in the shadows of giants, but would help shape the evolution of life on our planet for millions of years to come.
The Mesozoic saw the emergence of the first mammals, birds and flowering plants.
As palaeontologists shift the limelight away from dinosaurs and find out more about the ancient ecosystems, science is building a richer understanding of this prehistoric world.
Fossils of species described for the first time this year have helped in this pursuit.
How did pterosaurs fly
While dinosaurs dominated on land, growing to enormous sizes, the Mesozoic skies belonged to the pterosaurs.
These flying reptiles are not dinosaurs but are their evolutionary cousins.
Some pterosaurs, such as Quetzalcoatlus and Hatzegopteryx, were massive. These animals were as tall as giraffes when on the ground and had wingspans of more than 10m – larger than some aircraft.
Scientists have long wondered how such large creatures could get off the ground and fly. New fossil discoveries, including a new species of pterosaur, in Jordan have helped solve this mystery.
The animals lived 72–66 million years ago.
Analysis of the bone structure of Arambourgiania philadelphiae and new species Inabtanin alarabia revealed that large pterosaurs may have employed different flying styles. Some species may have flapped more than others, while soaring may have evolved later for flying in different environments, such as over open ocean.
New Zealand’s marine Mesozoic monster
Another group often mistakenly called “dinosaurs” are the ancient marine reptiles which swam Earth’s ancient oceans while the dinosaurs walked on land.
This year, scientists reported the oldest fossil of a marine reptile in the southern hemisphere. It lived 246 million years ago – right at the start of the Mesozoic – and its fossilised remains were discovered in modern-day New Zealand.
Although it was dug up in 1978, it wasn’t until this year that palaeontologists confirmed that it was a type of nothosaur – an ancestor of the more familiar plesiosaurs, known for their long necks and small heads. The New Zealand nothosaur challenges previous conceptions about when and where marine reptiles evolved.
Marine reptiles later in the Mesozoic could grow to more than 10m, but nothosaurs were usually about 3m long.
Dino croc from Germany
Nothosaurs look a little like today’s crocodiles. But the lineage which would evolve into crocodiles had already separated by the time of the Mesozoic. While nothosaurs were marine specialists, today’s crocodilians require some freshwater and can traverse land to look for it.
A 135-million-year-old crocodile fossil was found in Germany. The ancient croc, Enalioetes schroederi, was described for the first time this year.
It came from an extinct group of crocodyliforms, called metriorhynchidae, which were fully aquatic. They had flippers and tailfins instead of legs and feet. These strange Mesozoic crocodiles went extinct at the end of the Age of Dinosaurs 66 million years ago.
Giant Jurassic tadpole
Another familiar group of animals which lived during the time of the dinosaurs are anurans – the group which includes frogs and toads.
Palaeontologists in Argentina found a 16cm-long tadpole fossil. The creature lived 168 million years ago during the Jurassic period (201–145 million years ago).
While the tadpole is from a known species of ancient frog, Notobatrachus degiustoi, the find is the oldest tadpole ever found. This shows the two-stage life cycle of anurans was already present nearly 170 million years ago.
Predatory bird lived with T. rex and Triceratops
The mass extinction event at the end of the Age of Dinosaurs wiped out about 75% of life on Earth. Entire families of animals disappeared, including the pterosaurs, marine reptiles and non-avian dinosaurs.
But one group of dinosaurs lived on – the group which evolved into birds.
In fact, early birds had already evolved before the mass extinction 66 million years ago. Two species, Avisaurus darwini and Magnusavis ekalakaensis, lived 68 million years ago and were described in a paper published in October.
These arethe oldest examples of predatory birds in the fossil record.
Both species were found at the famous dinosaur fossil site at the Hell Creek Formation in the northern US. The site is a hotspot for finding some of the most well-known dinosaurs such as Tyrannosaurus rex and Triceratops horridus.
Our mammal ancestors in the time of dinosaurs
What were the ancestors of mammals – including humans – up to when dinosaurs were around?
The earliest mammals emerged during the Jurassic period. They were small, shrew-like creatures.
Papers published in April described 2 newly discovered species of mammal ancestors found in China. One, Feredocodon chowi, is from the Middle Jurassic (174–163 million years ago). The other, Dianoconodon youngi, dates to the Early Jurassic (201–174 million years ago).
Neither animal is a true mammal – they are our ancestors, yet to evolve all the features present in modern mammals.
The researchers found that the diversity even among these early Jurassic mammaliforms shows that the evolution of mammals may not have followed a straight-line path.
