A reconstruction of a multituberculate endocranial cast is made on the basis of a complete natural cast prepared from the skull of Chulsanbaatar vulgaris, and other less complete endocasts, all from the Late Cretaceous of Mongolia. The multituberculate endocast is of mammalian pattern but it has retained a therapsid-like lateral profile with a deep rhombencephalon and a shallow telencephalon. It is characterized by: a heart-shaped cross-section of the telencephalon; an extensive lissencephalic neocortex; a very prominent pons placed far anteriorly; a lack of cerebellar hemispheres, and very large paraflocculi. Its structure, very different from the brains of other mammals, suggests thats the Multituberculata branched very early from the main mammalian stock. This supports Simpson's (1945) idea that the Multituberculata should be placed in a subclass of their own: Allotheria MARSH. The endocast and braincase structure show that the Multituberculata had strongly developed senses of smell and hearing. The encephalization quotient of approx. 0.55 evaluated for Ch. vulgaris is relatively high for a Mesozoic mammal. 

The formic acid preparation of a nodule collected from the Lower Triassic of Spitsbergen, and containing a skull with some associated postcranial elements of Lyrocephaliscus euri (WIMAN), precises and enriches previous descriptions of the reputedly well-known trematosaur. lt permits more detailed descriptions of the occipital region, of the course of the carotid arteries and collateral vessels, and refutes the previous description of a stapedial foramen in trematosaurs. The discovery of pleurocentres associated with the other vertebral components confirms the primitive rhachitomy of trematosaurs.