Mei: Beast of the Week

 This week we will look out a dinosaur that helped solidify the connection between extinct dinosaurs and modern birds.  Let's check out Mei long!

Mei was a theropod dinosaur that lived in what is now China, during the Early Cretaceous period, about 125 million years ago.  It only measured about two feet (60cm) long as an adult, about the size of a modern duck, and would have eaten meat and possibly some plant material when alive.  The genus and species name, Mei long, translates from Chinese to "sleeping dragon" in reference to how this amazing fossil was discovered.  

Life reconstruction of Mei in watercolors by Christopher DiPiazza.

Mei's biggest claim to fame is how it was unearthed in a sleeping position, similar to how modern birds sleep with their head curled back and tucked under one wing and legs folded under the rest of the body.  Not only is this interesting purely because we know what kind of posture a dinosaur had millions of years ago, but it also strongly implies this dinosaur had feathers when alive, since the pose of the head tucked under the arm is so often done by modern birds with the use of wing feathers to shield the eyes.  The minerals between and over the bones of Mei imply the dinosaur was buried alive extremely quickly by ash from an erupting volcano, resulting in a beautifully preserved complete dinosaur skeleton for paleontologists to learn from.  

Cast of the juvenile specimen of Mei on display at the American Museum of Natural History in the seasonal "Dinosaurs Among Us" exhibit in 2014.

Mei was a member of the troodontid family of theropods.  Troodontids were birdlike, typically smaller dinosaurs that appear to have specialized in hunting small animals and possibly some plants when alive.  Troodontids typically had proportionally large eyes, narrow snouts, short arms, and long slender legs tipped with sharp claws, including a retractable second toe claw, which could have been an adaptation for pinning prey.  

Mei is known from two specimens, one young juvenile and one adult.  The adult retains what are generally considered juvenile characteristics, like proportionally short snout and large eyes.  Both specimens also exhibit relatively large nares (nostril holes in the skull) which is unusual for troodontids.  

Photograph of the second discovered specimen of Mei from the 2012 paper by Gao et al., which was an adult when it died. 

The environment that Mei lived in during the early Cretaceous appears to have been heavily forested with rivers and lakes throughout with nearby active volcanoes.  Since Mei was so small, it may have relied on hiding in the underbrush, or possibly even climbing trees to avoid predation from larger predators that shared its environment, like the gliding dinosaur, Changyuraptor, or even the large tyrannoysauroid, Yutyrannus.  Mei also would have crossed paths with dinosaurs like Beipiaosaurus and Tianyulong to name a few more.

References

Gao C, Morschhauser EM, Varricchio DJ, Liu J, Zhao B (2012) A Second Soundly Sleeping Dragon: New Anatomical Details of the Chinese Troodontid Mei long with Implications for Phylogeny and Taphonomy. PLoS ONE 7(9): e45203. https://doi.org/10.1371/journal.pone.0045203

Junchang Lü; Li Xu; Yongqing Liu; Xingliao Zhang; Songhai Jia & Qiang Ji (2010). "A new troodontid (Theropoda: Troodontidae) from the Late Cretaceous of central China, and the radiation of Asian troodontids" (PDF). Acta Palaeontologica Polonica. 55 (3): 381–388.

Xing Xu & Mark A. Norell (2004). "A new troodontid dinosaur from China with avian-like sleeping posture" (PDF). Nature. 431 (7010): 838–841.