Spinolestes
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.
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