Thanks for the reference to the poster by @dmac I looked a little more and found Neocortex in early mammals and its subsequent variations which states “In summary, early mammals had a small cap of neocortex on a forebrain that was dominated by a large olfactory bulb and olfactory (piriform) cortex…Early mammals, including the lines that led to present-day marsupials and monotremes, lacked motor and premotor areas, as these areas evolved with eutherian (placental) mammals.” and I wonder if that has implications for the essential motor features in Numenta’s theory. That references Why is Brain Size so Important:Design Problems and Solutions as Neocortex Gets Bigger or Smaller “The least shrew and the bumblebee bat are among the smallest of mammals, and they may represent the lower limits of size in mammals. Smaller mammals have smaller brains and smaller areas of neocortex.”
So we have a candidate winner: The least shrew
Also in that paper: “Areas can be quite small and still be functionally important. Yet areas less than 1 mm2 appear to be exceptional, and near the functional limit.”
From the Cheat Sheet : A cortical column is about 1.0 - 1.5 mm^2 in area and contains about 2000+ mini-columns