A separate study of volumetric breed comparisons showed that the relative volume of hindbrain parenchyma in CKCS is greater than in other small breed dogs (it is approximately equal to the Labrador - a mesaticephalic breed)[18]. (journals.plos.org)
In humans, «Classical» Chiari type I malformation is believed to result from hypoplasia of the basioccipital bone and a consequent reduction in the volume of the posterior cranial fossa (which extends from the petrosal crests and dorsum sellae to the foramen magnum), leading to overcrowding by hindbrain parenchyma (cerebellum, pons and medulla oblongata) and herniation of the cerebellum through the foramen magnum [12], [13], [14]. (journals.plos.org)
Tobias Langenberg (Brand, MPG)-- «Neuromeric organization of the midbrain hindbrain boundary region in zebrafish» (2004) (dresden-ipp.de)