acrylics, photography & digital, 2012
124,600,000 years ago, Early Cretaceous (earliest Aptian), Beipiao, Liaoning, China
On a chilly noon in Early Cretaceous Liaoning, the roar of an unfamiliar Yutyrannus rouses the emperor and his entourage to action. With the previous night's snowfall melting underfoot, they confidently stride along the territorial borders to face off any potential incursion by rival predators. A pair of squabbling Beipiaosaurus are slow to give way to the imperial procession and a sharp rebuke from a lieutenant sends them running for cover.
This is a depiction of life in the Cretaceous Yixian Formation of Liaoning, China, focusing on fossils collected in the Beipiao district.
Yutyrannus huali (beautiful feathered tyrant), described in April 2012, is by far the largest known Yixian theropod and likely the top predator of itís time (a slightly bigger fragmentary cousin, Sinotyrannus, is from the overlying Jiufotang Formation).
Yutyrannus was basal tyrannosauroid, anatomically close to the Tyrannosauridae proper. At over 8 metres long and about 1.5 tons in weight, it was approaching the size of classic Late Cretaceous tyrannosaurs like Albertosaurus. The skull, up to 90 cm long, was decked out with spectacular ornamentation with triangular allosauresque brow horns and a long crenulated median crest stretching from between the horns to above the nostrils.
This remarkable species is known from three articulated skeletons. 2 of them are effectively complete and found in very close proximity to one another (inches apart) at a quarry at Batuyingzi. They represent a mature animal (the holotype) and a pair of smaller subadults. There are no signs of violence or scavenging implying some degree of social behaviour. _Perhaps a group of Yutyrannus of varying ages all died together on a lakeshore, perhaps succumbing to disease or volcanic fumes.
Oh, and they had feathers.
Between the three individuals, long filamentous feathers are preserved along the tail, arms, legs and neck. Feathers were already known to have been present in small tyrannosauroids thanks to the description of little Dilong in 2004, a contemporary of Yutyrannus*. With this new discovery, we now know that full-sized baddass tyrannosaurs were fluffy as well. Whiners who bemoan the absence of feathers in the Jurassic Park raptors can now do likewise for T.rex.
Yutyrannus is another piece of evidence that EK Liaoning featured a dinofauna that was distinct from the rest of Asia, one adapted for the unusually cool conditions of that time and place. Far from the stereotypical tropical jungle, mid-Cretaceous Liaoning experienced a mean annual air temperature of 10 degrees centigrade and was blanketed in cool temperate coniferous forests.
Throughout most of Asia during the mid-Cretaceous, big allosauroids were the top terrestrial carnivores but were rare or absent in the Yixian and the slightly younger Jiufotang faunas of Liaoning. In those chilly forests, tyrannosaurs in their warm feathery coats reigned supreme; a reign that would eventually spread to the rest of Asia and North America towards the end of the Mesozoic.
*One of the first things I asked Xu Xing when presented with Yutyrannus in 2011 = "Could Dilong be a juvenile one of these?". He quickly showed me that the largest Dilong (at under 2 m in length) was a much more mature individual than the smallest Yutyrannus whelp (over 5 m long).
OTHER CREATURES =
From near Beipiao city, this decidedly dopey-looking creature was a small member of the long-clawed therizinosauroid group. Prior to the discovery of Yutyrannus, this 2 metre long herbivore was the largest known feathered non-avian dino.
From the same area as Beipiaosaurus, Eoenantiornis was a starling-sized enantiornithine bird with a deep, toothy snout.
A mid-sized pterosaur (known from a 40 cm long skull) from Heitizigou with two low sagittal crests: one over the snout and the other on the noggin. Is from a slightly lower unit (probably latest Barremian) than the rest of the critters in the picture.
Xu, X., Wang, K., Zhang, K., Ma, Q., Xing, L., Sullivan, C., Hu, D., Cheng, S., and Wang, S. (2012). "A gigantic feathered dinosaur from the Lower Cretaceous of China." Nature, 484: 92-95. doi:10.1038/nature10906
<update: 10-04-2012: extended feathering to the metatarsals based on the holotype. Early draft of the manuscript I used as a reference didn't mention pedal feathers - nor were they visible in the casts I viewed.>