KOL

When Turner, Nesbitt and Norell coined Kol ghuva in 2009, they expanded the already illustrious list of critters discovered at the Ukhaa Tolgod locality in Mongolia's Djadokhta Formation. This area has been worked for over a century and generously yielded near-complete specimens of mammals, lizards, crocodiles, dinosaurs and even eggs. Unfortunately, Kol isn't one of them, and palaeontologists have tried but failed to find a single scrap, in rock or museum, to bolster the tridactyl (three-toed) foot that represents the entirety of its remains.

As seen in most ornithomimids and some tyrannosaurs, and universally accepted as an adaptation for fast running, the lonely foot of Kol exhibits an extreme "arctometatarsalian condition", meaning its middle metatarsal (MT-III) is "pinched" by the flanking two (MT-II and MT-IV) and squeezed into a tapering wedge shape that is completely obscured from view at the ankle end. A slender build and diddy first metatarsal (MT I, a "dewclaw") allowed experts to whittle its potential family groups further, until they eventually recovered Kol as a parvicursorine (aka mononykine) alvarezsaurid: one of a strange bunch of feathered theropods with short but powerful forelimbs and a single functional digit (the thumb) adorned with a huge claw.

Despite its short name, along with Mei, the shortest among the dinosaurs until Yi arrived, Kol was quite big for an alvarezsaurid. In fact, the length of its metatarsals makes Kol the largest known alvarezsaurid, assuming its clan were all similarly proportioned, and fully twice the size of the contemporaneous parvicursorine Shuvuuia, which is represented by infinitely better fossils.