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Gliding Jurassic Mammals, Huge Dinosaurs and Ice Age Birds

A 160-million-year-old gliding mammal (Maiopatagium) discovered in China. Credit: Prof Zhe-Xi Luo, University of Chicago

A 160-million-year-old gliding mammal (Maiopatagium) discovered in China. Credit: Prof Zhe-Xi Luo, University of Chicago

By John Long

Gliding Jurassic Mammals, Huge Dinosaurs and Ice Age Birds

Perfectly preserved remains of gliding mammals have been dated to 160 million years ago.

The mammals that lived in the shadows of the dinosaurs were always depicted as small, shrew-like beasts. We now have clear evidence that early mammals had diversified into a number of specialised niches, such as aquatic forms like the beaverine Castrocauda from the Jurassic of Mongolia, and large predatory forms like Repanomamus from the Cretaceous.

Now, perfectly preserved remains of gliding mammals have been dated at 160 million years old (Jurassic) from the fine-bedded shales of Liaoning Province in China. Both Maiapatagium and Vilevolodon show skin-covered membranes extending between the limbs, similar to today’s gliding possums. The work by Prof Zhe-Xi Luo of The University of Chicago and colleagues from China came out as two papers in Nature on 10 August. Detailed study of the lower jaws pertaining to the inner ear anatomy of Vilevolodon shows that the inner ear structure was very primitive compared with other early mammals.

When I asked Luo what was so significant about his discoveries, he replied: “Early mammal history has now turned out to be surprisingly diverse, far more so than we had previously thought. The 160-million-year-old gliders from an archaic group show that even the stem mammals that are the extinct side-branches on the mammalian evolutionary tree can have their own ecological exploration and interesting adaptations. These exquisite fossils represent the most primitive-known evolutionary experiment in gliding, more than 100 million years before the modern mammals gliders, such as the sugar gliders and feather-tailed gliders.”

The latest claim for the “largest dinosaur ever” is another long-necked sauropod named Patagotitan mayorum, which lived about 100 million years ago in Chubut Province, Argentina. It was just bigger than its titanosaur kin Argentinosaurus. Patagotitan is known from six partial skeletons, the most complete known by its neck, chest and tail vertebrae, shoulder girdles, hip bones, thigh bone and ribs. It was estimated at 36.5 metres long and weighing around 63 tonnes, the equivalent weight of 12 normal African elephants). Others claim it was about as large as Argentinosaurus as the limb bones are of similar size.

Closer to home, an enigmatic dinosaur named Austrosaurus mckillopi from a few presacral vertebrae found on Clutha Station near Richmond, Queensland, in 1932 has been augmented with fresh material recovered from the original site. The site was considered lost after two attempts to relocate it failed. However, a team led by Tim Holland and Steve Poropat was able to relocate it in 2014. Austrosaurus was Australia’s first named sauropod dinosaur, and for years its validity as a species was cast in doubt.

A new paper published in Alcheringa by Dr Steven Poropat of Swinburne University has described the complete history of the beast’s discovery, as well as new material discovered from the site. The additional material of ribs and vertebral elements confirm that it is a distinct species, thereby adding to the growing diversity of large dinosaurs known from this continent.

A recent paper published in Royal Society Open Science by Ellen Shute, Gavin Prideaux and Trevor Worthy of Flinders University announced that giant scrub fowls (megapodes) weighing three times the mass of the largest living species once abounded in the early–mid Pleistocene of southern Australia. A new genus was named Latagallina, meaning “nuggety chicken” in deference to its robust build.

One doesn’t always need bones to tell a good fossil story, as shown by a publication in Alcheringa by Aaron Camens of Flinders University and colleagues. It details a great diversity of well-preserved fossilised animal trackways and invertebrate tracks and burrows from the Pleistocene coastal outcrops of Kangaroo Island.

John Long is Strategic Professor in Palaeontology at Flinders University, and is current President of the Society of Vertebrate Paleontology.