|Pipistrellus pygmaeus (image)|
|The postdentary jaw bones of mammals reduced through time (left to right) and became incorporated into the ear. This probably happened more than once in different lineages (from Luo, 2011)|
|The fossil of docodont mammal, Docofossor brachydactylus (top left), a specialist digger similar to the modern golden mole (top right) (Images Luo et al 2015, and April Neander)|
|Digital reconstructions of the left petrosal (front and back) of Borealestes, a docodont mammal from the Middle Jurassic of the Isle of Skye, Scotland. Bottom left: location of petrosal bones on bottom of skull.|
In the picture above, the petrosal is semi-transparent, showing the pathways that snake through it carrying nerves (yellow) and blood vessels (blue). You can see how dense the network of blood vessels is in this bone - some of these pathways have not been seen or described before in such an ancient mammal. We created a digital endocast of the inner ears - basically like pouring plaster into a hollow to see the shape - and one such endocast is pictured below for the right petrosal. You are basically looking at the shape of a mammal ear from the Middle Jurassic of the UK. Pretty cool eh?
|Endocast of the right petrosal of Borealestes, a docodont mammal from the Middle Jurassic of the Isle of Skye, Scotland.|
We'll now need to explore what those morphological differences might mean in terms of their hearing capabilities and broader evolution. In the coming years you'll be seeing a lot more of these and many other Jurassic Skye mammals.
Luo Z-X. 2011. Developmental patterns in Mesozoic evolution of mammal ears. Annual Review of Ecology, Evolution, and Systematics, 42: 355-380.
Panciroli E, Schultz JA, and Luo Z-X. 2018 Morphology of the petrosal and stapes of Borealestes (Mammliaformes, Docodonta) from the Middle Jurassic of Skye, Scotland. Papers in Palaeontology.