Geoscience Reference
In-Depth Information
Palaeoecological and palaeoenvironmental influences revealed
by long-bone palaeohistology: the example of the Permian
branchiosaurid Apateon
SOPHIE SANCHEZ
1,2
*, J. S
´
BASTIEN STEYER
1
, RAINER R. SCHOCH
3
&
ARMAND DE RICQL
`
S
4
1
UMR 5143 CNRS, D´partement Histoire de la Terre, Mus´um national d'Histoire naturelle,
CP 38, 57 rue Cuvier, 75005 Paris, France
2
UMR 7179 CNRS, D´partement Ecologie et Gestion de la Biodiversit´, Mus´um national
d'Histoire naturelle, CP 55, 55 rue Buffon, 75005 Paris, France
3
Pal ¨ontologische Abteilung, Staatliches Museum f ¨r Naturkunde, Stuttgart, Germany
4
UMR 7179 CNRS, Case 7077, Coll`ge de France and Universit´ Pierre et Marie Curie,
Paris 6, 2 place Jussieu, 75005, Paris, France
*Corresponding author (e-mail: sanchez@mnhn.fr)
Abstract: Apateon, a small temnospondyl from the Permian freshwater-lake deposits of the Saar-
Nahe Basin (SW Germany), is known by exceptionally well-preserved material. Here we report the
first palaeohistological analysis of Apateon that focuses on its life-history traits and palaeoenviron-
ments. Different samples (different localities and horizons) of Apateon caducus and Apateon
pedestris have been analysed. Their stylopod histology shows different growth rhythms that
might be correlated to changes in palaeoecosystems: food availability and/or presence of preda-
tors. Palaeoenvironmental influences are also recognized during the limb-bone osteogenesis by
the expression of simple and/or double patterns of Lines of Arrested Growth (LAG). A double-
LAG pattern expresses hibernating and aestivating arrests of growth in extant newts. The fossil
samples from the two stratigraphically oldest horizons preserved a similar double-LAG pattern,
suggesting that they may have hibernated and aestivated every year because of harsh climatic con-
ditions. The Saar-Nahe lake system probably passed from a higher altitude zone into a lower one,
possibly because of subsidence and/or erosion. It could also be correlated to the size of the lakes
that differs from one locality to another, inducing different responses of the organisms to the
climatic variations.
Apateon Meyer, 1844 is a well-known dissorophoid
from the Carboniferous and Permian of Europe
(France, Germany and Czech Republic) (Boy
1972, 1987; Heyler 1994; Boy & Sues, 2000).
Hundreds of well-preserved specimens, falling into
different growth classes interpreted as growth
series, have been collected in the Permian of
Germany. This has permitted studies of the bran-
chiosaurid anatomy (e.g. Boy 1986), palaeobiology
(e.g. Boy & Sues 2000), ontogeny (Schoch 1992,
2004; Fr ¨bisch et al. 2007), palaeoecology (e.g.
Boy & Sues 2000; Werneburg 2002) and phylogeny
among temnospondyls (e.g. Boy 1987; Steyer 2000).
Branchiosaurids form a speciose clade probably
closely related to the Amphibamidae (Schoch &
Milner 2008), a group of small dissorophoids that
has been hypothesized as lissamphibian stem-group
by some authors (Milner 1993; Ruta et al. 2003;
Schoch & Milner 2004) or at least closely related
to batrachians (Anderson 2007; Anderson et al.
2008).
Regarding the palaeoecology of Apateon, numer-
ous hypotheses have been put forward. Some of
them suggest that this small aquatic branchiosaurid
was an opportunist and adapted to lacustrine
environments (e.g. A. pedestris) or even to mountai-
nous streams (e.g. A. dracyiensis) (Werneburg
2002) according to the size of external gills and
the body shape. It has also been considered as an
R-strategist (Boy & Sues 2000; Werneburg 2002).
So far, these palaeoecological inferences were
exclusively based on anatomical and morphological
features of Apateon in comparison with those of
living amphibians. The palaeohistology of Apateon
has never been observed, although the available
material is very promising and would be an extra-
ordinary
source
of
information
(Ricql`s
et
al.
2004).
Indeed,
new
data
on
time
recording
