Name: Spinolestes.
Phonetic: Spy-no-les-teez.
Named By: T.‭ ‬Martin,‭ ‬J.‭ ‬Marugán-Lobón,‭ ‬R.‭ ‬Vullo,‭ ‬H.‭ ‬Martín-Abad,‭ ‬Z.-X.‭ ‬Luo‭ & ‬A.‭ ‬D.‭ ‬Buscalioni‭ ‬-‭ ‬2015.
Classification: Chordata,‭ ‬Mammalia,‭ ‬Eutriconodonta,‭ ‬Gobiconodontidae.
Species: S.‭ ‬xenarthrosus‭ (‬type‭)‬.
Diet: Insectivore.
Size: About‭ ‬24‭ ‬centimetres long.
Known locations: Spain‭ ‬-‭ ‬La Huérguina Formation.
Time period: Barremian of the Cretaceous.
Fossil representation: Complete specimen including soft tissue remains of fur,‭ ‬internal organs,‭ ‬scutes and even the ears.

       Spinolestes is a genus of small mammal that lived in Spain during the early Cretaceous,‭ ‬and one that has told us more about‭ ‬Mesozoic mammals that most other genera combined.‭ ‬This is all down to the truly exceptional level of preservation in the xenarthrosus type specimen that not only contains the skeleton,‭ ‬but impressions of soft internal organs,‭ ‬hair,‭ ‬and even the ears.
       The level of preservation of the hair of Spinolestes can be done to the cellular level,‭ ‬and this has revealed that the hair of Spinolestes was already like that of modern animals.‭ ‬Spinolestes had also developed spine-like guard hairs that were similar to those seen in species of the modern day Acomys genus,‭ ‬more commonly referred to as spiny mice which are native to Africa.‭ ‬Some of these hairs were also broken near the skin as well as discoloured at the point of breakage,‭ ‬which may well be signs that this individual had a skin infection at the time of death.‭ ‬Aside for the spines,‭ ‬Spinolestes also possessed scutes,‭ ‬plates of bone that grew within the skin that would have provided a defence against the mouths of very small predators.‭
       Usually at best only the inner ear of ancient mammals is preserved,‭ ‬but in Spinolestes we not only have that but the outer ear structure as well.‭ ‬This is an exceptionally rare feature that has been preserved,‭ ‬and in Spinolestes we know that the ears of Spinolestes were well developed and rounded in a similar fashion to what we would see in a mouse today.
       As far as the general body is concerned,‭ ‬Spinolestes had powerful limbs and feet,‭ ‬way beyond what would be necessary for just walking about.‭ ‬It is possible that Spinolestes was also a digger,‭ ‬perhaps digging burrows,‭ ‬or perhaps even into the ground for food.‭ ‬The dentition of Spinolestes is suggestive of an insectivore,‭ ‬and so combined with a strong digging ability,‭ ‬Spinolestes may have been breaking open ancient termite mounds to hunt for food.

Further reading
-‭ ‬A Cretaceous eutriconodont and integument evolution in early mammals.‭ ‬-‭ ‬Nature‭ ‬526:380-384.‭ ‬-‭ ‬T.‭ ‬Martin,‭ ‬J.‭ ‬Marugán-Lobón,‭ ‬R.‭ ‬Vullo,‭ ‬H.‭ ‬Martín-Abad,‭ ‬Z.-X.‭ ‬Luo‭ & ‬A.‭ ‬D.‭ ‬Buscalioni‭ ‬-‭ ‬2015.


Random favourites