Flying Squirrels, Pteromyini, are today represented in Europe by
only a single species, the Siberian Flying Squirrel, Pteromys volans, which is found in the Coniferous forests of Russia,
Finland and other areas in the northeast of the continent, but in the lowland
tropical forests of Southeast Asia as many as six species may be found living
alongside one-another, able to co-exist because they occupy slightly different
ecological niches. In the much warmer climate of the Miocene, Flying Squirrels
are known to have been more numerous and diverse in Europe, with sites in
Central Europe producing up to five species, suggesting a similar ecological
diversity to that of modern Southeast Asia. However this level of diversity has
not been recorded from the Late Miocene of Iberia, where three species have
been recorded from Catalonia and none from the rest of the peninsula. This is
in keeping with current reconstructions of the Miocene climate of Iberia, which
suggests a more arid climate then the rest of Europe, with an intermediate
climate in Catalonia, wetter than the rest of Iberia but dryer than most of
Europe, a situation that persists to this day.
In a paper published in the journal Palaeobiodiversity and Palaeoenvironments
on 8 May 2015, Isaac Casanovas-Vilar of the Institut Català dePaleontologia Miquel Crusafont at the Universitat Autònoma de Barcelona, SergioAlmécija of the Institut Català de Paleontologia Miquel Crusafont at the
Universitat Autònoma de Barcelona and the Department of Anatomical Sciences at
Stony Brook University and David Alba, also of the Institut Català de
Paleontologia Miquel Crusafont at the Universitat Autònoma de Barcelona describe a
series of new Flying Squirrel remains from the Late Miocene Can Llobateres 1
site in the Vallès-Penedès Basin of Catalonia, and discuss the implications of
these for the climate and environment of Miocene Catalonia.
The Can Llobateres 1 was discovered in the 1920s during a road
construction project and has been the subject of intermittent excavations ever
since, particularly since the discovery of Ape remains at the site in the
1950s, which resulted in a prolonged collaboration between Spanish palaeontologist
Miquel Crusafont and Johannes Hürzeler from the Museum of Basel, during which
many tons of sediment were removed and sieved for microfossils, resulting in
(amongst other things) a number of Flying Squirrel teeth being recovered in the
1960s. Excavations at Can Llobateres 1 were resumed in 2010 after a 12 hiatus
by a team from the Institut Català de Paleontologia Miquel Crusafont, resulting in
a number of new Flying Squirrel remains.
In order to determine that a Squirrel was capable of flying (or more
technically gliding, since no squirrel can actually fly) it is necessary to be
able to reconstruct a reasonable proportion of its post-cranial skeleton. This
is not possible to do from any of the Catalan material, which comprises only
Teeth, but it is usually possible to assign Rodents to species level from their
teeth (as with most Mammals), and all of the Can Llobateres 1 material is
assigned to species described elsewhere, enabling either a more complete
knowledge of their anatomy or at least a confident assignment to the tribe Pteromyini
(Flying Squirrels).
The species Albanensia grimmi,
was first described from three cheek teeth from Marktl in Germany in the 1960s.
It is distinctive within the genus Albanensia
for its large size and the thicker posterolophid and stronger metalophid tooth
cusps. In 1970 a partial jaw fragment with two molars and an isolated premolar
were described from Miocene sites in the Vallès-Penedès Basin and tentatively
assigned to this species, though they were larger than the German material and
showed some morphological differences. Since then more specimens of the species
have been described from other sites in Europe, notably Rudabánya in Hungary
and Götzendorf and Richardhof-Golfplatz in Austria, which have led to a more
complete understanding of morphological variation within the species. Due to
this the Catalan material is no longer considered to be outside the range of
morphological variation for the species, but is still exceptionally large. In
addition to the previously described material, Casanovas-Vilaret al. describe a new specimen, a third
molar, from Can Llobateres 1. They assign all these specimens to ‘Albanensia aff. grimmi’ (i.e. a member of the genus Albanensia showing affinities with Albanensia grimmi).
A molar of a Flying Squirrel from Can Llobateres 1
showing strong affinities to Albanensia grimmi. Casanovas-Vilaret al. (2015).
The species Miopetaurista neogrivensis
was described from La Grive in France in 1970 to describe large members of this
genus. In 1991 a single molar assigned to this species was described from Can
Llobateres 1. Casanovas-Vilar et al.
redescribe this specimen and agree with its taxonomic placement, as well as
noting that other specimens of the species have recently been collected from
other sites in the Vallès-Penedès Basin, which are likely to have formal
descriptions published in the near future.
Second molar of Miopetaurista neogrivensis from
the Late Miocene Can Llobateres 1 site in the Vallès-Penedès Basin of Catalonia. Casanovas-Vilar et al. (2015).
The species Miopetaurista crusafonti
is well represented at Can Llobateres 1, with 17 isolated cheek teeth and six
molar fragments recorded to date. This is considered to be a medium-sized member
of the genus Miopetaurista, larger
than the numerous species known from earlier Miocene deposits, but not as large
as other Late Miocene species such as Miopetaurista neogrivensis,
Miopetaurista thaleri and Miopetaurista tobieni. The species was
originally described from a fragment of maxilla bearing the fourth premolar and
first two molars from the Vallès-Penedès Basin, though this material is stored
at the Faculté des Sciences de Montepellier and Casanovas-Vilar et al. have not seen it. The species has
been described from several other sites in Catalonia, and may possibly also be
present in southern France.
Specimens assigned to Miopetaurista crusafonti from the Late Miocene Can Llobateres 1 site
in the Vallès-Penedès Basin of Catalonia. (b) Left fourth premolar, (c) left
first or second molar, (d) right third molar collected in 2011, (e) right lower
fourth premolar, (f) right first molar, (g) left second molar, (h) right third
molar. Casanovas-Vilar et al. (2015).
The species Blackia miocaenica
is considerably smaller and simpler than the other Catalan material. The small
size and simple morphology of the specimens is considered enough to assign them
to the genus, which contains only two species, and the measurements of the
specimens place them within the species Blackia miocaenica rather
than the slightly larger Blackia woelfersheimensis.
The species has previously been recorded from the Early Miocene of Valencia
(six million years older than the Can Llobateres 1 deposits), as well as from
sites in the Czech Republic, Germany, Switzerland, France, Slovakia, Hungary,
Romania and Austria. Casanovas-Vilar et al.
report two first molars (one left and one right) of Blackia miocaenica fromCan Llobateres 1, the first time this species
has been recorded from the Late Miocene of Catalonia.
Specimens assigned to Blackia miocaenica from the Late Miocene Can Llobateres 1 site in the
Vallès-Penedès Basin of Catalonia. (l) Left first molar, (m) right first molar.
Casanovas-Vilar et al. (2015).
Finally Casanovas-Vilaret al.
report twoworn lower cheek teeth which fall loosely within the size range of
two species, the Flying Squirrel Pliopetaurista kollmanni
and the Ground Squirrel Spermophilinus bredai (which
is also known from Can Llobateres 1). However the specimens have crenulated
enamel, a feature associated with Flying Squirrels but not Ground Squirrels, so
they are tentatively described as cf. Pliopetaurista
sp. (i.e. probably a species of Pliopetaurista).
Specimens assigned to cf. Pliopetaurista sp. from the Late Miocene Can Llobateres 1 site in the
Vallès-Penedès Basin of Catalonia. (j) Left fourth premolar (k) right third
molar. Casanovas-Vilar et al. (2015).
Several decades of intensive sampling, including the sifting of many
tons of sediment for microfossils, have now raised the number of Flying
Squirrels found at Can Llobateres 1 to five, comparable with Miocene sites in
central Europe and modern lowland forest ecosystems in Southeast Asia, though
there is a clear disparity in the frequency of specimens, suggesting that some
species were far more common than others.
As well as Flying Squirrels the Late Miocene sediments of the
Vallès-Penedès Basin have produced a variety of other Mammals, such as Apes,
Tapirs and Rhinoceroses, which indicate a humid forest environment. The
sediments have also produced plant fossils such as Reeds, Figs, Palms and
Cinnamon Trees, further supporting this environmental interpretation. Middle
Miocene sites in Spain have produced evidence of three different ecosystems,
herb-dominated wetlands, Legume-dominated woodlands with species such as Casia, Acacia and Caesalpina,
indicative of a much drier climate and evergreen Laurel forests which could
indicate wetlands or montane forests. Unfortunately most Late Miocene sites in
Spain lack sufficient plant material for such interpretations, though sites in
the Pyrenees have produced evidence of a mixed flora, with evergreen Laurels
alongside more northerly species, such as Alders, Chestnuts, Willows and Elms.
The Late Miocene Vallès-Penedès Basin appears to have been home to
wet forests with similarities to those of contemporaneous central Europe,
though with a more restricted fauna; many central European species are absent
and others, such as Flying Squirrels, were apparently much rarer. A total of
five Flying Squirrel species from one site is exceptional, with only a few
sites in Germany and France achieving this, but this detection cannot be
divorced from the sheer scale of investigations that have occurred at Can
Llobateres 1, where decades of excavations have taken place and tons of
sediments sieved, and it is likely that many European sites which have produced
more samples of common species with much less effort would also produce more species
were they subjected to the level of sampling carried out at Can Llobateres 1.
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