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altitude (Poplin 1994; Boy & Schindler 2000; Boy
& Sues 2000; Sanchez et al. 2010).
However, Schultze & Soler-Gij
´
n (2004) have
recently suggested marine influence in these Euro-
pean basins because of the presence of several
brackish or saline water indicators: marine calcar-
eous algae (dasycladaceans and udoteaceans), anne-
lids, euthycarcinoids, xiphosurans, euryhaline
sharks (xenacanths, Sphenacanthus and Lissodus),
the actinopterygians Bourbonnella and haplolepi-
forms, myxinoids (Poplin et al. 2001) and shark
egg capsules (Fayolia, Palaeoxyris, Vetacapsula).
According to Schultze & Soler-Gij
´
n (2004), the
analysis of the distribution of fossil egg capsules
in the basins is a powerful tool for the determination
of palaeosalinities. This suggestion is based on the
fact that no recent oviparous shark is known to
deposit egg capsules in freshwater. In contrast,
the few recent elasmobranchs adapted to more or
less permanent life in freshwater (i.e. stenohaline
freshwater) are viviparous (e.g. potamotrygonid
rays). Chondrichthyan egg capsules (Palaeoxyris
and Vetacapsula) have been reported in Mazon
Creek and Hamilton, both localities with evidence
of tides, and egg capsules have been described
from Commentry (Massif Central) and from
several localities of Saar-Nahe, Saale and
Bohemian basins, which suggests a connection to
marine areas of the Palaeotethys (Schultze & Soler-
Gij
´
n 2004).
Palaeotopographic features of the Variscan
mountain chain and altitude of the western and
central Permo-Carboniferous basins have important
implications in the study of development and
growth pattern of stegocephalians. Recently,
Schoch & Fr ¨bisch (2006) and Fr ¨bisch & Schoch
(2009) explained neoteny, very common in bran-
chiosaurids from Saar-Nahe basin, by the high
elevation (up to 2000 m or more above sea level)
of the lakes where those stegocephalian lived.
Sanchez et al. (2010) explained a double growth
line pattern in bones of Apateon as the consequence
of hibernation-estivation events similar to those
which affect recent amphibians living in mountain
lakes at temperate latitude (several localities in
north of Portugal).
Both studies are based on a model of limnic
basins located at a very high altitude (a few thou-
sands of metres) as proposed by Becq-Giraudon
et al. (1996) for the Stephanian basins of the
Massif Central. However, recent estimations of the
altitudes of the basins indicate a relative low topo-
graphy (Opluˇtil 2005a, b; Roscher & Schneider
2006; Schneider et al. 2006), which suggests that
the environmental factors which induced hetero-
chrony in branchiosurids were not low temperature;
perhaps fluctuations in the salinity of the waters is a
more plausible cause.
Studies of the euryhaline toad Bufo calamita and
other recent amphibians (Gomez-Mestre & Tejedo
2002, 2005; Gomez-Mestre et al. 2004) which are
adapted to a brackish environment show variations
of thyroid hormone linked to increase in the salinity
(see below for more information about salt tolerance
of recent amphibians). Furthermore, double growth
patterns as described in Apateon are also shown in
several groups of recent tropical actinopterygians
living in low altitudes in coastal and estuarine
areas. For example, two annuli and two zones per
year have been described in bones of teleosts
(Ariidae, Anastomidae and Serrasalmidae) from
French Guyana; the annual growth marks have
been connected to the existence of two dry seasons
and a bimodal rainfall pattern (Lecomte et
al.
1986, 1993; Meunier et al. 1994).
The growth pattern of the tropical stegocepha-
lian Apateon (probably a stem-tetrapod, although
many authors consider it a stem-amphibian), which
probably lived in a low altitude as indicated by the
most recent analyses of the Permo-Carboniferous
basins, probably results from factors other than the
growth pattern of recent lissamphibians of Portugal
living at a temperate latitude and in high altitude.
For Opluˇtil (2005a), the recent analogue of the
Late Palaeozoic continental basins of central and
western Bohemia is the Tasek Bera Basin in
central Peninsular Malaysia; this is a dendritic
basin, located at about 38N, 35 m above sea level,
surrounded by lowland hills rising up to 240 m
above sea level.
For localities of the Cutler Formation from New
Mexico, other localities which yielded seymouria-
morphs (Berman et al. 1987; Klembara & Mesz
´
ros
1992; Berman & Martens 1993) and the Sangre de
Cristo Formation from Colorado, we are not aware
of clear evidence of marine influence. However,
many of the taxa found there (such as xenacanthi-
form chondrichthyans, acanthodians and dipnoans)
are also known from marine and brackish environ-
ments (Table 2). Even the seymouriamorphs are
also found in other, presumably brackish environ-
ments (Montceau-les-Mines, Texas redbeds).
Nevertheless, the great abundance of seymouria-
morphs in basins showing the least marine influ-
ence, and their lesser abundance or absence from
basins which show more marine influence, suggests
that they may have been less tolerant of brackish and
saltwater than many other early stegocephalians.
Vaughn's (1969) palaeogeographic reconstruc-
tions placed some localities in New Mexico and
Colorado in 'somewhat more upland' environments
in contrast to other localities located in the 'truly
deltaic' environments (or 'coastal plain', as pro-
posed by Berman & Reisz 1980). In the Cutler
Formation, the abundance of caliche (Berman
et al. 1985, 1987), a hardened deposit of calcium
