New quantitative data from a digital cranial endocast of Kryptobaatar dashzevegi (Multituberculata, Mammalia) and a new estimate of body mass

We extracted a digital cranial endocast from a high-resolution X-ray computed tomography scan of a specimen of the Late Cretaceous Mongolian multituberculate Kryptobaatar dashzevegi . The digital endocast shows qualitative and quantitative differences from a previously published description of a natural endocast of K . dashzevegi . In particular, the endocranial volume (EV) of the digital endocast, measured from high-resolution X-ray computed tomography (CT) scans of a skull, is considerably smaller than a previous estimate of EV for Kryptobaatar from the natural endocast determined using the equation for the partial volume of a cylinder. The new, more accurate measure of EV for Kryptobaatar (EV = 0.34 mL), along with a new estimate of body mass, has implications for calculating the encephalization quotient (EQ) for this taxon and making comparisons with relative brain size in mammals in general. In particular, the EQ of Kryptobaatar was calculated as 0.32, which is significantly lower than other reported EQs for multituberculates, multiple basal mammals, and the stem mammal Hadrocodium wui .