The Early Permian Branchiosaurids (Amphibia) of Sardinia (Italy): Systematic Palaeontology, Palaeoecology, Biostratigraphy and Palaeobiogeographic ...
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Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383 – 404
www.elsevier.com/locate/palaeo
The Early Permian Branchiosaurids (Amphibia) of Sardinia (Italy):
Systematic Palaeontology, Palaeoecology, Biostratigraphy and
Palaeobiogeographic Problems
Ralf Werneburg a,⁎, Ausonio Ronchi b , Jörg W. Schneider c
a
Naturhistorisches Museum Schloss Bertholdsburg, Burgstr. 6, D-98553 Schleusingen, Germany
b
Dipartimento di Scienze della Terra, Via Ferrata 1, I-27100 Pavia, Italy
c
TU Bergakademie Freiberg, B.v.Cotta-Str.2, D-09596 Freiberg, Germany
Received 25 September 2006; received in revised form 23 March 2007; accepted 26 March 2007
Abstract
The branchiosaurid fauna from the Is Alinus-lake of Rio su Luda Formation (lithofacies c) in the Perdasdefogu Basin of
Sardinia (Italy) includes three species: Melanerpeton eisfeldi, Apateon kontheri and Apateon flagrifer. The same three species are
known from Gottlob-lake in the Thuringian Forest Basin of Germany and are interpreted as valid in the sense of the “biospecies”
concept, not closely related to each other and most probably reproductive in the same lake. That is a very surprising and convincing
conformity of both branchiosaurid faunas: parallel evolution of three different amphibian species in two different areas seems
impossible. Gene flow must have existed between the populations of the northern and southern parts of the Variscan mountain
chain. Additional findings of three-dimensionally preserved but isolated amphibian bones, such as jaw fragments with pleurodent
dentition, have been discovered in limestone of the Rio su Luda Formation (lithofacies d) from the Ortu Mannu section. They
belong very probably to those branchiosaurids. Occurrences in both Sardinia and Thuringia require corresponding migration routes
for the branchiosaurs, possibly via basins in southern France, the French Massif Central and southern Germany. Possibly all
branchiosaurids of these three species are neotenic and referable to the ecomorphological “stream-type” with favourable migration
capabilities, as in modern urodelans such as newts and salamanders.
The Perdasdefogu Basin of Sardinia is presently the southernmost known occurrence of branchiosaurid amphibians in Europe,
and its palaeo-position is of special interest. Sardinia was obviously part of a hydrographical system at the southern flank of the
Variscides. No insurmountable migration barrier, such as a marine sound or seaway, existed between Sardinia and Palaeo-Europe,
because the same species of obligatorily non-marine amphibians are known from these two areas. The Sardinian occurrence widens
significantly the amphibian migration routes described before.
On the basis of these amphibians, it is possible to correlate the Rio su Luda Formation of Sardinia with the Goldlauter to Lower
Oberhof Formation of the Thuringian Forest reference section by combined use of Melanerpeton eisfeldi and Apateon flagrifer as index
species of phylo(morpho)genetic lineages. In synthesis with isotopic ages, this time span is equivalent to the Asselian/Sakmarian transition
of the global scale; most likely the Rio su Luda Formation correlates directly with the Upper Goldlauter Formation (Late Asselian).
© 2007 Elsevier B.V. All rights reserved.
Keywords: Branchiosauridae; Palaeoecology; Palaeobiogeography; Biostratigraphy; Early Permian; Sardinia
⁎ Corresponding author. Tel.: +49 36841 531212; fax: +49 36841 531225.
E-mail addresses: museum.schleusingen@gmx.de (R. Werneburg), Ausonio.ronchi@manhattan.unipv.it (A. Ronchi),
schneidj@geo.tu-freiberg.de (J.W. Schneider).
0031-0182/$ - see front matter © 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.palaeo.2007.03.048384 R. Werneburg et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383–404
1. Introduction (Geinitz) (now Batrachichnus, referable to branchiosaur-
like amphibians, compare Voigt, 2005), from Upper
In the 1990s, the most significant Sardinian Ear- Carboniferous (Westphalian D?) strata of the San Giorgio
ly Permian basins (Perdasdefogu, Escalaplano, Seui, Basin (Iglesiente, SW Sardinia); four new tetrapod
Lu Caparoni; Italy, Europe), which, for more than a ichnospecies were recently described from the same
century had yielded much palaeontological data (al- succession (Conti et al., 2004).
most exclusively macroflora), were intensively rein- On the basis of numerous abundant palaeomagnetic data
vestigated and highlighted a new and diverse fossil collected over the last 30 years by many authors (see the
record (Broutin et al., 1996; Ronchi, 1997; Ronchi review by Speranza, 2000), the extent of counterclockwise
et al., 1998; Broutin et al., 2000; Cassinis et al., 2000; rotation of the Corsica–Sardinia block is presently
Cassinis and Ronchi, 2002; Freytet et al., 2002). A estimated to be about 60°. However, in spite of the close
rich amphibian fauna has been discovered for the first similarity between the Permian–Triassic successions of the
time in Italy in the Perdasdefogu Basin (Ronchi and Nurra and Toulon basins recently reported (Cassinis et al.,
Tintori, 1997). 2003), the palaeoposition of Sardinia is still debated.
Fossiliferous layers have yielded several specimens of Recent lithostratigraphical correlations unequivocally led
branchiosaurs, often in repeated mass mortality assem- Cassinis et al. (2003) to face Nurra (NW Sardinia) with the
blages. Prior to this discovery, tetrapods were only known Toulon area. Indeed, other authors (e.g. Westphal et al.,
by their trackways. Fondi (1979) reported the occurrence 1973, 1976; Ziegler and Stampfli, 2001) had correctly
of the ichnogenus Salichnium (Saurichnites) heringi placed Sardinia in an area between south-western France
Fig. 1. Geological map of Sardinia with locations of the Perdasdefogu, Lu Caparoni-Cala Viola and Guardia Pisano basins.R. Werneburg et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383–404 385
were attached or in very close proximity during the
Permocarboniferous.
2. Geological and stratigraphical setting
The Early Permian Perdasdefogu Basin is located in
southeastern Sardinia (Ogliastra region). The corre-
sponding literature is generally scarce (Maxia, 1938;
Sarria, 1987). Only recently have renewed PhD studies
(Ronchi, 1997; Ronchi et al., 1998; Ronchi and Sarria,
2000) provided new insights into biostratigraphy and
basin analysis.
This small intramontane trough (Fig. 1) is a half-
graben with a clearly asymmetric inner structure con-
trolled by major normal faults and tilted blocks, and by
transverse structures, as shown by a recent drilling
campaign in the basin (Sarria, 1987). It is bordered to
the west by a major fault, with associated “en echelon”
longitudinal normal faults, both antithetic and synthetic,
and shows a complex and significantly variable sedimen-
tary and volcanic evolution.
Perennial alluvial to lacustrine environments are pre-
served within the basin fill. The Rio su Luda Formation
(Ronchi and Falorni, 2004), averaging 120 m thickness,
has been formally subdivided into four different lithofacies
(Fig. 2): lithofacies a is a basal polygenic conglomerate,
max. 30 m thick, resting unconformably on the Variscian
metamorphic basement, the source of the pebble content;
lithofacies b, only developed in Escalaplano (not in
Perdasdefogu) is made up of varicoloured fine epiclastic
rocks with intercalations of freshwater limestones and
palustrine nodules (up to 25m thick); lithofacies c, the
“shaly–sandy lithofacies”, is represented by mm-to cm-
Fig. 2. Stratigraphically representative section of the Early Permian laminated blackish and grey shales and sandstones, locally
Rio su Luda Formation in the Perdasdefogu Basin (SE Sardinia). exceeding 100 m in thickness; lithofacies d, the “cherty-
Vertical distances are not time- or thickness-related. carbonate lithofacies”, is composed of up to 70 m of
freshwater limestones and dolostones, with frequent chert
intercalations and hyaloclastic tuffs at the top. The latter
(Provence) to the north-eastern part of Spain (Catalonian two lithofacies interfinger with intermediate to acidic
Pyrenees). Paleontological affinities (particularly micro- calcalkaline volcaniclastic and lavic products. Decimetre-
and macrofloras: Ronchi et al., 1998; Broutin et al., 1999, thick conglomeratic horizons, thin subordinate anthracite
2000) confirm close relationships between Sardinia and the layers and horizons of completely devitrified pyroclastic
cited southern border of paleo-Europe and also to inner deposits also occur in the lacustrine carbonate sequence.
sectors (Massif Central). On the other hand, some old and Along the SW margin of the basin, the Rio su Luda
recent palaeogeographical works (e.g. Arthaud and Matte, Formation is covered by 180 m thick calcalkaline dacitic
1977; Bard, 1997; Stampfi and Borel, 2002; von Raumer lava flows, while in the NW sector of the basin the same
et al., 2003) set Sardinia more far to the SW in the prox- strata are followed by rhyolitic volcaniclastic strata and by
imities of the Iberian Plate and south of a main structural several tens of metres of sub-intrusive rhyolitic bodies.
line (North Pyrenean Fault). The Permian sedimentary and volcanic succession of the
Under any circumstances, as discussed below, Perdasdefogu Basin averages 250–300 m in thickness.
this amphibian fauna provides very strong proof – in With unconformable and erosive contacts over these
fact confirmation – that Sardinia and Palaeo-Europe deposits, massive conglomerates and/or dolostones of the386 R. Werneburg et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383–404
Table 1 Genna Selole and Dorgali Formations can be found, both
Comparative measurements of the determinable Sardinian branchiosaurids of Middle Jurassic age (Bajocian to Kimmeridgian).
(see Werneburg, 1989a)
Among many plant specimens recently collected in
Specimens Sl (mm) IOw/Sl Hl/Sl Hw/Sl HUMl/Sl lithofacies c of the Rio su Luda Formation, Broutin et al.
Melanerpeton eisfeldi (1999, 2000) reported a macroflora association of which
UM-38 16.3 0.21 0.36 0.80 – the following are the more representative forms: Annularia
NHMS-WP 2192/5 ca. 12.5 ca. 0.27 – – –
mucronata Schenk, Odontopteris lingulata (Goeppert)
NHMS-WP 2180 11.7 0.24 0.29 0.85 –
UM-42/1 10.9 0.24 0.37 0.80 – Schimper, Neuropteris osmundae (Artis) Kidston, Autu-
UM-14/1 10.8 0.26 0.37 0.74 0.33 nia (al. Callipteris) conferta (Brongniart) Haubold et
UM-5 10.5 0.21 – – – Kerp, Rhachiphyllum schenkii (Heyer) Kerp, Dichophyl-
NHMS-WP 2191/1 10.5 0.26 0.33 0.85 – lum flabellifera (Weiss) Kerp et Haubold, Lodevia nicklesii
NHMS-WP 2165/1 9.8 0.26 0.30 0.77 –
(Zeiller) Haubold et Kerp, Ernestiodendron filiciforme
NHMS-WP 2190/2 9.8 0.26 – –
UM-16 9.3 0.25 0.30 0.70 – (Sternberg) Florin, and Otovicia hypnoides (Florin) Kerp
UM-10 9.0 0.27 0.33 0.94 0.42 et al. This meso- to xenophile flora is of typical “Autunian”
NHMS-WP 2178/4 9.0 0.27 0.29 0.90 – aspect, but some of the most characteristical elements, such
UM-10/1 8.9 0.25 0.36 0.88 – as Autunia, Neuropteris, Otovicia, Dichophyllum and Er-
NHMS-WP 2190/1 8.8 0.27 0.34 0.79 0.34
nestiodendron, occurred abundantly in the Stephanian, e.g.
UM-27 8.1 0.24 – – 0.35
NHMS-WP 2187 7.7 0.25 0.32 1.0 0.34 in Morocco and in the Donetsk Basin (cw. Broutin et al.,
7.7– 0.21– 0.29– 0.70– 0.33– 1999; Schneider, 2001; Hmich et al., 2003). Only R.
16.3 0.27 0.37 1.00 0.42 schenkii, L. nicklesii and O. lingulata seem to be restricted
to the Autunian (considering this term as a latest Gzhelian
Apateon kontheri
to Early Sakmarian floral association, sensu Broutin et al.,
NHMS-WP 2267 15.5 0.25 0.37 0.77 –
NHMS-WP 2193 12.0 0.25 – – – 1999).
NHMS-WP 2194 12.0 0.25 0.40 0.88 0.29 The amphibian skeletons of the Is Alinus locality occur
UM-24/1 11.0 0.28 0.33 0.76 – in mm-scale blackish-grey/pale-grey laminated silty
UM-11/8 8.2 0.28 0.36 1.06 – claystone of 0.70 m thickness, about 1 m below the base
NHMS-WP 2184/2 7.2 0.27 0.32 – –
of lithofacies d of the Rio su Luda Formation. Isolated
NHMS-WP 2192/1 6.8 0.27 0.36 0.91 –
NHMS-WP 2188/1 5.6 0.30 – – – amphibian remains, preliminarily reported herein, come
5.6– 0.25– 0.32– 0.76– 0.29 from the limestone beds of the Ortu Mannu locality 50 m to
15.5 0.30 0.40 1.06 the NW of the Is Alinus site, and about 2 m above the base
of lithofacies d.
Apateon flagrifer
UM-42/2 11.7 0.30 0.32 0.88 –
NHMS-WP 2268 9.7 0.28 0.32 0.85 0.30
NHMS-WP 2174 9.6 0.31 – – –
NHMS-WP 2175 9.5 0.30 – 0.94 – Table 2
UM-11/2 9.5 0.32 0.39 – – Comparison of the most common branchiosaurid genera Apateon and
NHMS-WP 2168 9.2 0.29 0.33 0.95 0.38 Melanerpeton (based on dates of Boy, 1986, 1987; Werneburg, 1986a,
UM-32 9.0 0.27 0.37 0.89 0.42 1989a, 1991)
UM-7 8.7 0.29 0.36 0.84 –
NHMS-WP 2188/2 8.1 0.38 – – – Features Apateon Melanerpeton
UM-99/1 7.9 0.32 0.32 0.90 0.37 Sclerotical Posteromedially Posteromedially
UM-14/2 7.8 0.33 0.40 0.78 – ring elements short and wide elongated and
NHMS-WP 2183/1 7.6 0.31 0.33 0.98 – narrow in the
NHMS-WP 2169 7.3 0.31 0.34 0.97 – juvenile stage
NHMS-WP 2189/1 6.8 0.36 0.34 0.97 – Ectopterygoid Wide and short Narrow and elongated
UM-1 6.5 0.30 0.35 – – Intraorbital More wide (IOw/ More narrow (IOw/
UM-11/1 6.2 0.31 0.36 0.88 – region (frontals) Sl = 0.25–0.37 Sl = 0.16–0.28
6.2– 0.27– 0.32– 0.78– 0.30– Orbit Relatively short Elongated, especially in
11.7 0.38 0.40 0.98 0.42 posterior direction
Skull roof Relatively high More flat and lower
Abbreviations: Hl: length of the postorbital skull; Hw: width of the
postorbital skull; HUMl: length of the humerus; I0w: width of the (lateral view)
intraorbital region; Sl: length of the skull. Preorbital region Short and blunted Mostly elongated
(nasals) and narrow
Palatine Mostly short Mostly long and narrow
and wideR. Werneburg et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383–404 387
3. Systematic Palaeontology or the Carboniferous Branchiosaurus (Werneburg,
1987) and Milnererpeton (Hunt et al., 1996), e.g. with
Nearly 100 branchiosaur skeletons are known from highly ossified ventral scales, are significantly different
the Perdasdefogu Basin. Ronchi and Tintori (1997) from the Sardinian branchiosaurids. These specimens
first presented taxonomic remarks of the so-called can be assigned to the common branchiosaurid genera
Branchiosaurus cf. B. petrolei and pointed out a very Apateon and Melanerpeton. They are distinguished by
high variability in the width of the intraorbital region. skeletal features (Table 2), which, however, are difficult
Now it is clear that the Sardinian branchiosaurs belong to utilize in small or poorly preserved specimens. The
to three species, with different widths of the intraorbital width of the interorbital region (IOw — the shortest
regions (Table 1). distance between the orbits) is very useful for
All specimens are members of the family Branchio- providing a general overview of the material. Subse-
sauridae, which includes six genera. The genus quently additional features must be examined. Our
Schoenfelderpeton with a specialised otic notch (Boy, analyses indicate that the Sardinian branchiosaurids are
1986), the Permo-Triassic Tungussogyrinus with tricus- represented by one species of Melanerpeton and two
pid teeth (Shishkin, 1998; Werneburg, in preparation) species of Apateon (Fig. 3). The representatives of
Fig. 3. Three branchiosaurid species of the Perdasdefogu Basin (Sardinia) and the Thuringian Forest Basin (Germany); reconstruction of the dorsal
skull roof (a, c, e) and the palatal view (b, d, f) after Thuringian specimens (cw. Werneburg, 1986b, 1988a). Abbreviations: ectp — ectopteryoid, fr —
frontal, ju — jugal, la — lacrimal, max — maxilla, na — nasal, pal — palatine, par — parietal, pmx — premaxilla, po — postorbital, ppar —
postparietal, prf — prefrontal, psph — parasphenoid, pt — pterygoid, ptf — postfrontal, qj — quadratojugal, scl — sclerotical ring elements, Sl —
skull length, sq — squamosal, st — supratemporal, tab — tabular, vo — vomer.388 R. Werneburg et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383–404
Melanerpeton are similar to M. eisfeldi and M. gracile Table 3
(e.g. short, nearly square supratemporal, see Table 3). Comparison of Melanerpeton eisfeldi and the most related species
Melanerpeton gracile (based on dates of Werneburg, 1988a,b, 1991)
The characteristics of the postorbital, maxilla, para-
sphenoid, palatine and ilium are diagnostic (bold Features Melanerpeton eisfeldi Melanerpeton gracile
printed in Table 3 and with “!” in Fig. 4). Analysis Size of the species Large, slightly Relatively small,
of these features (see below) indicates that the Sardinian sculptured dorsal more strongly sculptured
skull roof
Melanerpeton specimens belong to Melanerpeton
Skull 10–34.7 mm 7–11.3/23 mm
eisfeldi (Figs. 3 and 4). length (Sl)
Most similar to the two Sardinian species of Apateon Snout region Pointed Rounded
are A. kontheri and A. pedestris (e.g. I0w, kontheri-type (in a late stage)
of hyobranchial apparatus and parasphenoid; see Intraorbital region Narrow Narrow
IOw/Sl = 0.19–26, IOw/Sl = 0.16–27,
Table 4) as well as A. flagrifer and A. caducus (e.g.
∅ = 0.23 ∅ = 0.24
I0w, flagrifer-type of hyobranchial apparatus and Postorbital skull Abbreviated Abbreviated
postfrontal; see Table 4). One Sardinian Apateon Supratemporal Nearly square shaped Nearly square shaped
species is Apateon kontheri (Figs. 3 and 5) with Postorbital Elongated and narrow Short and very wide
diagnostic features of the postfrontal, parasphenoid, Nasal Narrow Wider
Maxilla Middle long, Relatively short and
ectopterygoid, vomer and clavicle, and the second is
ontogenetically high, ontogen.
Apateon flagrifer (Figs. 3 and 6) with the diagnostic shape later elongated later elongated
of parietal, postparietal, tabular, maxilla, parasphenoid, Parasphenoid Slightly build; short Robust build; elongated
palatine, vomer and ilium (bold printed in Table 4 and with base; elongated and large base; relatively
“!” in Figs. 5 and 6). cultriform process. short cultriform process
ontogen. later wider
Palatine Even elongated Mostly short and variably
Abbreviations of collections and narrow wide, ontog. later
BMNH British Museum of Natural History London elongated and narrow
(D.M.S. Watson-collection) Vomer Elongated and Short and wide, probably
FG TU Bergakademie Freiberg narrow, with without posteromedial
posteromedial process process
MNG Museum der Natur Gotha
Ilium Slightly ossified, with Robust build, with a
NHMS Naturhistorisches Museum Schloss Bertholds- a relatively narrow wide dorsal process
burg Schleusingen dorsal process
SD Hessisches Landesmuseum Darmstadt Number of 20–21 20–22
SWC Cambridge University Museum of Zoology presacral
vertebrae
(England),
UM University of Milano.
Further occurrences:
Order: Temnospondyli Zittel, 1888 – Radelsgraben near Gebrannter Stein between Tabarz
Superfamily: Dissorophoidea Bolt, 1969 and Inselsberg, Thuringian Forest/Germany (Upper
Family: Branchiosauridae Fritsch, 1879 Goldlauter Formation, Lower Rotliegend)
Genus: Melanerpeton Fritsch, 1878 – Is Alinus-lake horizon, Perdasdefogu Basin, Oglias-
tra region, SE Sardinia, Italy; lithofacies c, Rio Su
3.1. Melanerpeton eisfeldi Werneburg, 1988 Luda Formation, Late Asselian, Early Permian
Material from Sardinia: Nearly 40 specimens in the
Synonymy: partim Branchiosaurus brachyr- palaeontological collections of the University of Milano
hynchus, Watson (1963, fig. 2e; Paratypus, BMNH R. (UM) and of the Museum of Natural History Schleusin-
5469); ?Leptorophus sp.-G, Boy (1987) gen (NHMS)
Holotype: MNG 2992-68, Werneburg (1988a: Bild Diagnostic features (in comparison to the most
7a, 8a) closely related species Melanerpeton gracile, juvenile
Locus typicus: Gottlob quarry in the town of stage, see Table 3):
Friedrichroda, Thuringian Forest, Germany 1. parasphenoid with a short base and an elongate cul-
Stratum typicum: Gottlob-lake horizon, Upper triform process
Goldlauter Formation, Lower Rotliegend, Late Asse- 2. palatine even, elongated and narrow
lian, Early Permian 3. vomer narrowR. Werneburg et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383–404 389 Fig. 4. Melanerpeton eisfeldi, skulls in dorsal (d, f, h) and ventral view (a–c, e, g); a—UM-38; b — UM 16; c—NHMS-WP 2165a/1; d—UM 42/1 (=42/d); e—NHMS-WP 2180; f—NHMS-WP 2178/4; g—NHMS-WP 2191/1; h—NHMS-WP 2191/1. Abbreviations: atl — atlas, bb — basibranchial, ch — choane, e.s — endolymphatical sac, o.s — orbital sac; other abbreviations in Fig. 3. 4. maxilla relatively elongated 7. ilium slightly ossified, with a relatively narrow dorsal 5. postorbital elongated process 6. nasal narrow 8. large sized species (up to 35 mm skull length).
390 R. Werneburg et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383–404
Table 4
Comparison of Apateon kontheri and Apateon flagrifer with their most related species (based on dates of Boy, 1978, 1987; Werneburg, 1986b,
1988a)
Apateon kontheri Apateon pedestris Features Apateon flagrifer Apateon caducus
Large; slightly sculptured Relatively small; more Size of the Relatively small; more Large; slightly
strongly sculptured species; sculpture strongly sculptured sculptured
of dorsal skull roof
6–27 mm 5–18/20 mm Skull length 5–15.5 mm 6–32 mm
IOw/Sl = 0.25–29 ∅ = 0.27 IOw/Sl = 0.25–30 Intraorbital region IOw/Sl = 0.26–35 IOw/Sl = 0.29–0.35
∅ = 0.28 ∅ = 0.29/30
Longer as wide Longer as wide Supratemporal Longer as wide Longer as wide
Wide Wide Parietal Wide Narrow
(posterior)
Relatively elongated Middle elongated Postparietal Elongated Short
Middle elongated Middle elongated Tabular Elongated Short
Short, ontogenetically later elongated Short Postfrontal Long and wide Long and wide
(posterior)
Middle elongated Middle elongated Maxilla Rel. short and high, Elongated and narrow,
without especially with a pronounced
pronounced dorsal process
dorsal process
kontheri-type kontheri-type Hyobranchial flagrifer-type flagrifer-type
apparatus
Wide, base narrow and elongated Narrow to middle wide, Cultriform Narrow, base wide Relatively narrow, base
base wide and short process and base and short wide and short
of parasphenoid
Relatively wide and short Relatively wide and short Palatine Wide Relatively narrow
Wide and short, ont. later elongated Relatively wide and short Ectopterygoid Relatively wide Wide and short
and short
Elongated Short Ventral plate Short Short
of clavicle
Short, with a little posterior process, Always short and wide, Interclavicle Mostly wider as long Mostly wider as long
ont. later elongated, nearly so long with a large
as wide with a convex posterior margin posterior process
II/1 N III/1 II/1 b = N III/1 Phalanges of manus II/1 b III/1 II/1 b III/1
Dorsal process wide and straight, Dorsal process wide and Ilium Robust, with a wide Only slightly ossified
ontogen. later more narrow and straight, ontogen. later and straight dorsal (as juvenile), with a
posterior directed posterior directed process straight dorsal process
3.1.1. Skull roof f). The short supratemporal of mostly square shape is
The Sardinian specimens have a skull length up to characteristical for both species (Fig. 4a, d). The tabular
16.3 mm. The sculpture of the dorsal skull roof is not has a large tabular process in the posterior direction
very coarsely developed in the recorded stage (Fig. 4d). (Fig. 4b, d, e). The length of the postparietal is variable
So the skeletons belong to a large sized species. (Fig. 4d, h and e), the occipital lamella is variably paired
The intraorbital region of the skull roof (frontals) is (Fig. 4d) or unpaired developed (Fig. 4b, e). The
narrow: IOw/Sl = 0.21–0.27. The preorbital region postfrontal is elongated and relatively narrow. A wide
(especially the nasal) is narrow and elongated, the jugal is observed in the largest specimen (Fig. 4a).
postorbital region is relatively short and variably wide
(Table 1). The orbit is large and, especially in the 3.1.2. Palate
posterior direction, elongated. The posteromedial elon- The parasphenoid shows a very narrow and elongated
gated and narrow sclerotic elements are preserved in one cultriform process (Fig. 4a, g). The base of the para-
specimen (Fig. 4f). sphenoid is moderately elongated in the largest specimen.
The maxilla is not well preserved, but in general it is Ventrally there are the characteristic foramina of the arteria
relatively elongated (Fig. 4b). The postorbital is carotis interna (Fig. 4a). In one case a short groove from
elongated in contrast to Melanerpeton gracile (Fig. 4d, another arteria is preserved on the anterolateral edge ofR. Werneburg et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383–404 391
the ventral base of the parasphenoid (Fig. 4a). The palatine notch, short postorbital, narrow posterior part of the
process of the pterygoid is strongly curved (Fig. 4g, a). parietal, short maxilla, short elements of the sclerotic ring,
The vomer is probably narrow and possibly developed and a very short humerus (Boy, 1986).
an unpaired posteromedial process (Fig. 4a, b, f). The
palatine is narrow and elongated, with one large and three
small teeth in ventral view (Fig. 4a, c, f). The two other species are comparable with the
species of the genus Apateon. It is necessary to provide
3.1.3. Visceral ossifications and gills a brief remark regarding the grammar of the Apateon
The stapes shows a curved shaft and a wide plate species names. For a long time it was not clear whether
with the stapedial foramen (Fig. 4a). The nearly circular the grammatical gender of the genus was masculine or
mineralised remains of the endolymphatic sacs are feminine. The type species is Apateon pedestris Meyer,
clearly visible (Fig. 4b, g). 1844. Werneburg (1988a ff.) had used the feminine
From the hyobranchial apparatus, only two basibran- gender for several species of Apateon (e.g. A. flagrifera,
chials (Fig. 4b, c), some isolated narrow hypobranchials A. caduca or A. umbrosa), but now it is clear that the
and sometimes branchial denticles are preserved. genus Apateon is of masculine gender (Rainer Schoch,
personal communication). Consequently, the species
3.1.4. Postcranial skeleton names of Apateon have the following endings now:
Remains of the postcranial skeleton are rarely Apateon pedestris, A. caducus, A. flagrifer, A. kontheri,
preserved. The humerus is relatively elongated A. dracyiensis, A. intermedius and A. umbrosus.
(HUMl/Sl = 0.33–0.42). One postcranial skeleton with- Genus: Apateon Meyer, 1844
out skull shows a pair of tiny, slightly ossified ilia with
relatively narrow dorsal processes, which are character- 3.2. Apateon kontheri Werneburg, 1988
istic for Melanerpeton eisfeldi (UM 33b/2).
Synonymy: cf. Melanerpeton pulcherrimum FR. —
3.1.5. Comparison Langenhan (1909, pl. 1, fig. 15)
Based on the analysed features, the specimens clearly Holotype: FG 321/9/1 (counterpart SD-V70), Wer-
belong to Melanerpeton eisfeldi. The most closely neburg (1988a, figs. 2b, 4a)
related species Melanerpeton gracile is similar, but Locus typicus: Gottlob quarry in the town Fried-
important differences are used to separate the two (below richroda, Thuringian Forest, Germany
and Table 3). The feature common to both is the short, Stratum typicum: Gottlob-lake horizon, Upper
nearly square-shaped supratemporal, which is an Goldlauter Formation, Lower Rotliegend, Late Asse-
excellent diagnostical difference from other Melaner- lian, Early Permian
peton species and from the related Schoenfelderpeton Other occurrence: Is Alinus-lake horizon, Perdasde-
prescheri. fogu Basin, Ogliastra region, SE Sardinia, Italy; litho-
The stratigraphically oldest Melanerpeton species, M. facies c, Rio Su Luda Formation, Late Asselian, Early
sembachense from the Ilmenau Formation of the Thurin- Permian
gian Forest (Fig. 10), has a much larger vomer plate and a Material from Sardinia: Nearly 20 specimens in the
well ossified ilium (Werneburg, 1989b). Melanerpeton palaeontological collections of the University of Milano
tenerum from NW Saxony shows a wider and shorter (UM) and of the Museum of Natural History Schleusin-
postorbital as well as a nearby position of post- and gen (NHMS).
prefrontal at the orbital margin (Boy, 1986). From the Diagnostic features (in comparison to the most
Saar–Nahe basin, Melanerpeton humbergense possesses a closely related species Apateon pedestris, see Table 4):
ventrally sculptured parasphenoid, and a shorter and wider 1. parasphenoid with a wide cultriform process and a
nasal and vomer (Boy, 1987). The smaller species Mela- narrow and elongated base
nerpeton pusillum from the Intrasudetic Basin (Werne- 2. ectopterygoid wide, in later ontogenetic stages
burg, 1986a) and M. arnhardti from the Thuringian Forest elongated
Basin (Werneburg, 1988b) have a shorter postorbital, a 3. vomer wide and short
larger vomer and a shorter and wider palatine (Fig. 10). M. 4. postfrontal posterior more elongated in a later stage
pusillum has a narrower postorbital skull and a heavily 5. clavicle with an elongated ventral plate
ossified ilium too. Schoenfelderpeton prescheri from NW 6. interclavicle firstly wide oval with a short posterior
Saxony and the Thuringian Forest shows many differ- tip, ontogenetically later elongated, nearly as long as
ences: supratemporal with a “semilunar flange” at the otic wide, with a slightly convex posterior margin392 R. Werneburg et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383–404 Fig. 5. Apateon kontheri, skulls in dorsal (b) and ventral view (a, c–i), plus skeletal parts; a, b — NHMS-WP 2193b, a; c—UM 24/1; d—NHMS-WP 2267; e, f — NHMS-WP 2192a/1, b; g—NHMS-WP 2184b/2; h—NHMS-WP 2194 a; i—NHMS-WP 2184b/3. Abbreviations: atl—atlas, b.o— branchial ossicles, cl — clavicle, cth — cleithrum, e.g. external gills, e.s — endolymphatical sac, fem — femur, hum — humerus, icl — interclavicle, il — ilium, l.asc — lamina ascendens, r — rib, sc — scapulocoracoid, stp — stapes; other abbreviations in Fig. 3. 7. ilium with a more narrow dorsal process in a later 3.2.1. Skull roof ontogenetic stage The skull length of the Sardinian specimens reaches 8. large sized species (up to 27 mm skull length) up to 15.5 mm (Table 1). The sculpture of the median
R. Werneburg et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383–404 393
elements of the dorsal skull roof is slightly developed features with the next related species Apateon pedestris
(Fig. 5b). These specimens also belong to a large sized are included in Table 4 and in the diagnostic features
species. above.
The shortest distance between the orbits (intraorbital Two smaller sized species, Apateon intermedius from
region, frontals) is intermediate (I0w/Sl = 0.25–0.30). The the Stephanian of the Thuringian Forest Basin, the Saale
preorbital region is short and blunt, while the postorbital Basin and the Ilfeld Basin (Werneburg, 1996) as well as A.
region is relatively elongated and variably wide (Table 1). dracyiensis from the Early Permian of the Thuringian
The orbit is intermediate in size. The elements of the Forest, NW Saxony and the Autun Basin (Werneburg,
sclerotic ring are also short in the posteromedial part. 2001; here both in Fig. 10), possess many features in
The maxilla is intermediate in size and elongated in a common with and differing from Apateon kontheri. These
later ontogenetic stage (Fig. 5d, h). The postorbital was at different features of A. intermedius and A. dracyiensis are:
first short (Fig. 5e–g), ontogenetically later elongated short maxilla, contact of post- and prefrontal, narrow
(Fig. 5b, d). The posterior part of the postfrontal is short, parietal, wide palatine process of pterygoid and the small
ontogenetically later more elongated and larger (Fig. 5b, c, ilium with a narrow dorsal process. The other Apateon
d, h). The supratemporal is longer than wide (Fig. 5d, e). group with the small Apateon flagrifer from the Early
The posterior part of the parietal is in general wide Permian of the Thuringian Forest (Werneburg, 1986b)
(Fig. 5b, e), but sometimes also narrower (Fig. 5d). The (now also from Sardinia) as well as A. caducus from the
parietal ridges are preserved on a ventral skull roof (Fig. 5e). Early Permian of the Saar–Nahe Basin (Boy, 1978), have
The tabular process is not very large (Fig. 5c, d–h). many features in common with and differing from
A. kontheri. These differences of A. caducus are: wide
3.2.2. Palate intraorbital region, large posterior region of postfrontal,
The shape of the parasphenoid is very significant for parasphenoid with narrow cultriform process and wide
this species. The cultriform process is wide and the base base, hyobranchial apparatus from the flagrifer-type, short
is long and narrow (Fig. 5a, c, f–i). The pterygoid has a clavicle and interclavicle plus other proportions of
straighter palatine process and a large lamella increases the manus phalanges. For differences to A. flagrifer see
in the larger specimens (Fig. 5h, i). The vomer is wide Section 3.3.5.
and short. Also the palatine and ectopterygoid are short
and relatively wide (Fig. 5g, i). 3.3. Apateon flagrifer (Whittard, 1930)
3.2.3. Visceral ossifications and gills Synonymy: Branchiosaurus flagrifer Whittard, 1930;
Some small bones of basi- and hypobranchials of the Branchiosaurus brachyrhynchus Watson, 1963 (holo-
hyobranchial apparatus and rows of branchial ossicles are type); Apateon pedestris ?brachyrhynchus, Boy (1987)
preserved (Fig. 5a, g). One specimen shows three rela- Holotype: SWC-T 22 (= D.M.S.W. - B 48), Werne-
tively short and narrow external gills in soft-part burg (1986b, Bild 2a, 4a)
preservation (Fig. 5f). Locus typicus: Gottlob quarry in the town Fried-
The small mineralised concretions, as remains of the richroda, Thuringian Forest, Germany
endolymphatic sacs, are situated on the posterolateral Stratum typicum: Gottlob-lake horizon, Upper
sides of the parasphenoid base (Fig. 5 a, e, f, g, i). Goldlauter Formation, Lower Rotliegend, Asselian,
The stapes shows a wide foot plate with the stapedial Early Permian
foramen and a narrow shaft (Fig. 5 i). Remarks: Two chronosubspecies are known (Fig. 10):
Apateon flagrifer flagrifer (Whittard, 1930) from the
3.2.4. Postcranial skeleton Lower and Upper Goldlauter Formation, Late Asselian
Some important features are known from the (Werneburg, 1986b), and Apateon flagrifer oberhofensis
postcranial skeleton. The ventral plate of the clavicle is from the Lower and Upper Oberhof Formation of the
very elongated (Fig. 5a) and the interclavicle is long (Fig. Thuringian Forest basin, Sakmarian (Werneburg, 1988b)
5d). The phalanges of the manus are not well preserved. Further occurrences:
The massive ilium has a wide and straight dorsal process – nearly 10 localities in the Lower Rotliegend of the
(Fig. 5h). Thuringian Forest/Germany
– probably in the Bourbon l´Archambault Basin/France
3.2.5. Comparison – Is Alinus-lake horizon, Perdasdefogu Basin, Oglias-
The preserved features show the best congruence with tra region, SE Sardinia, Italy; lithofacies c, Rio Su
those of Apateon kontheri. The different and common Luda Formation, Late Asselian, Early Permian394 R. Werneburg et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383–404 Fig. 6. Apateon flagrifer, skulls in dorsal (a, f, h) and ventral view (b–e, g) plus skeletal parts; a, b—NHMS-WP 2268a, b; c—NHMS-WP 2174; d — NHMS-WP 2188/2; e — NHMS-WP 2182 a/1; f — UM 32; g — UM 42/2; h — NHMS-WP 2168. Abbreviations: atl — atlas, bb — basibranchial, b.o — branchial ossicles, cl — clavicle, cth — cleithrum, e.g — external gills, fem — femur, hb1,2 — hypobranchial 1 and 2, hh — hyohyal, hum — humerus, icl — interclavicle, il — ilium, o.s — orbital sac, sc — scapulocoracoid. v.s — ventral scales; further abbreviations in Fig. 3.
R. Werneburg et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383–404 395
Material from Sardinia: Nearly 40 specimens in the characteristically elongated and narrow. The hypobran-
palaeontological collections of the University of Milano chial 1 is narrower than the hypobranchial 2, but of the
(UM) and of the Museum of Natural History Schleusin- same length. The basibranchial is relatively elongated,
gen (NHMS) more elongated than in the type series of the Thuringian
Diagnostic features (in comparison with the most Forest (Werneburg, 1986b).
closely related species Apateon caducus, see Table 4): Some branchial denticles are preserved, but without
1. parietal posterior wide details. One short branch of the external gills shows
2. postparietal and tabular elongated some little diversification — see Fig. 6a.
3. maxilla relatively short and high (without notably
pronounced dorsal process) 3.3.4. Postcranial skeleton
4. palatine wide The interclavicle is wider than long and with a
5. ilium robust ossified, with a wide dorsal process posteromedian processus (Fig. 6h). The clavicle prob-
6. relatively small sized species (up to 15.5 mm skull ably has a relatively short ventral part (Fig. 6e). The
length). ilium is robust ossified, with a short, wide and straight
dorsal process (Fig. 6e, a).
3.3.1. Skull roof Thin ventral scales of circular shape are preserved
The Sardinian specimens reach a skull length only up (Fig. 6e). The sculpture consists of three nearly
to 11.7 mm (Table 1). Unfortunately, the sculpture of the concentric rings together with fine radial elements.
dorsal skull roof is not well preserved. Only some strong
radial elements may indicate more developed sculpture 3.3.5. Comparison
(Fig. 6a, d). Therefore, these skeletons very probably The specimens described above belong to the species
belong to a relatively small sized species. Apateon flagrifer. Sardinian specimens are not well
The intraorbital region of the skull roof (frontals) is enough preserved for determination of subspecies. The
wide (IOw/Sl = 0.27–0.38). The postorbital region of the subspecies Apateon flagrifer oberhofensis shows a short
skull roof is relatively elongated and variably wide; the and wide postorbital, up to 22 presacral vertebrae and
preorbital part is short and blunted (Table 1). lateral line grooves on the skull roof (Werneburg,
The supratemporal is longer than wide (Fig. 6f, h). The 1988b). However, some features have to be determined
posterior parietal is widened (Fig. 6a, f, h). The elongated (postorbital, postfrontal, vomer, basibranchial). The
postparietal (Fig. 6a, f, h) and tabular are large (long tabular Sardinian material may represent a third subspecies,
process, Fig. 6f–h). The length of the posterior postfrontal but this is currently uncertain.
and postorbital is in agreement. It is mostly elongated The different and common features to the most
(Fig. 6a, c, d, g), but sometimes smaller. Unfortunately the closely related species, Apateon caducus, are included
nasal is not well preserved; therefore, the narrower in Table 4 and in the diagnostic features above.
character in this species is only postulated (Fig. 6a, h). The Apateon group with the large sized species
Especially interesting is the shape of the maxilla. It is Apateon kontheri from the Asselian, Early Permian of
relatively short, and the dorsal process is high, but not the Thuringian Forest (Werneburg, 1988a, now also
pronounced (Fig. 6a, b, h) as in Apateon caducus. The jugal from Sardinia), as well as the small sized A. pedestris
is ossified and relatively elongated; the width is unclear from the Asselian, Early Permian of the Saar–Nahe
(Fig. 6g, h). The elements of the sclerotic ring are short. Basin (Boy, 1978), have many features in common
with A. flagrifer. They differ from A. flagrifer by: nar-
3.3.2. Palate rower interorbital region, smaller posterior region of
The parasphenoid has a wide and short base, the postfrontal, parasphenoid with a wider cultriform
cultriform process is narrow. The anterior palatine and process and a narrower base, hyobranchial apparatus
so the choane are wide (Fig. 6b–d, e). The ectopterygoid from the kontheri-type, longer ventral plate of clavicle,
is short; the width is unclear (Fig. 6b). The vomer is a more elongated interclavicle and other proportions of
wide (Fig. 6b, d, g) and has a row of denticles at the the manus phalanges.
margin of the choane. One vomer is narrower shaped The other group of the small-sized Apateon species
(Fig. 6c). with Apateon intermedius from the Stephanian of the
Thuringian Forest, the Saale Basin and Ilfeld Basin
3.3.3. Visceral ossifications and gills (Werneburg, 1996), as well as A. dracyiensis from the
In one specimen the ossified hyobranchial apparatus Early Permian of the Thuringian Forest, NW Saxony and
is preserved (Fig. 6b). The shape of the hyohyal (hh) is the Autun Basin (Werneburg, 2001), show many common396 R. Werneburg et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383–404
features with Apateon flagrifer (Fig. 10). The differences
to A. flagrifer are: short maxilla, contact of pre- and
postfrontal, narrow parietal, wide palatine process of
pterygoid and small ilium with a narrow dorsal process.
3.4. Isolated amphibian remains from the Ortu Mannu
limestone
Formic acid processing of limestone samples of
lithofacies d of Rio su Luda Formation from the Ortu
Mannu section, still in progress, provide isolated fish
remains such as teeth of the freshwater sharks Xena-
canthus and Bohemiacanthus (comp. Schneider, 1996),
Acanthodes scales and spine fragments, palaeoniscid
teeth and scales and scale fragments of sarcopterygians
(Schneider et al. 2003). Additionally, nearly 30 isolated
amphibian remains, such as jaws, teeth and limb bones,
have been extracted. These remains very probably
belong to branchiosaurs for the following reasons:
Fig. 7. Branchiosaurid dentary of the lower jaw with pleurodent
– The general shape and size of the isolated bones, dentition; limestones of the Ortu Mannu section in the Perdasdefogu
including 11 lower jaw fragments (Fig. 7), three Basin (compare Fig. 2); a — FG 20354, b — FG 20338.
probable premaxillas and one palatine, resemble
those of the branchiosaurid anatomy. aridisation plus tectonism and volcanism, produced a
– The type of dentition is rarely well observed in the wide variety of lake environments during the Upper
compressed preservation of skeletons in laminated Carboniferous and Early Permian (Schneider, 1989; Boy
shales and laminated limestones. The three-dimen- and Schindler, 2000; Roscher and Schneider, 2006).
sionally preserved jaw bones from the non-laminated Short-term changes in ecological parameters imply the
limestone of Ortu Mannu display a very clear existence of unstable environments, especially for
pleurodent dentition (Fig. 7). This dentition type is smaller, shallow lakes; these contrast with better
also known from the branchiosaur Apateon dra- buffered large and deep lakes. The most critical
cyiensis of the Dracy St. Loup locality, where the parameter for aquatic animals is oxygen content.
specimens are exceptionally well preserved in Undisturbed fine lamination of Corg-rich grey to black
slightly compacted shales (Werneburg, 2001). shales indicates, for most of the Late Palaeozoic, the
– The isolated amphibian remains from the Ortu existence of a belt of lakes of tropical to subtropical
Mannu limestone are found only 3 m above the climate with variable levels of oxygen. Some of these
laminated Is Alinus shales, which contain the three lakes, or discrete single stages of lake development, were
branchiosaurid species. inhabited only by amphibians — the so-called bran-
chiosaur lakes, as is the case with the Is Alinus-lake. The
Micropalaeontological processing of rock samples Is Alinus shales have provided exclusively branchio-
from Sardinia indicate further occurrences of bran- saurids — no other vertebrate remains. Why?
chiosaurs. Limestones from the Guardia Pisano Basin The branchiosaurid amphibians coped with ecolog-
(Sulcis) in the SW of Sardinia have provided an ical stress using facultative neoteny (neoteny in the
indeterminable jaw fragment of a small branchiosaur- sense of Duellman and Trueb, 1986; Boy and Sues,
like amphibian with acrodent-like dentition, occurring 2000). These branchiosaurs reached sexual maturity in
together with isolated fish remains of Acanthodes and the larval stage; this, along with the small size, rapid
teeth of the hybodont shark Lissodus. growth rates and a high reproduction rate, resulted in a
high number of individuals. These features are charac-
4. Palaeoecology teristic of branchiosaurs, so-named r-strategists (Boy,
1993; Boy and Sues, 2000), which were successful in
In western Europe annual and long-lasting (thousands living under environmental changes or ecological stress.
to million years) changes between dry and wet periods of This strategy is a significant advantage in the bran-
a monsoonal climate, as well as generally increasing chiosaur occupation of the lakes, in contrast to fish,R. Werneburg et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383–404 397
which need more constant conditions with a higher
content of oxygen. Additionally, using a combination of
lungs and external gills for breathing allowed amphi-
bians to overcome oxygen deficiency to some extent.
Oxygen depletion occurs in stratified eutrophic mer-
omictic lakes at night, when the assimilation of plants
and algae stops and organic matter on the lake bottom
decays by (bacterial) oxidation. The results are anoxic
conditions ranging from inside the sediment up into the
hypolimnion. During episodic events of complete
mixing of the water column, the epilimnion could also
develop oxygen deficiency. Together with ascending
hydrogen sulphide from decaying organic matter, this
could cause mass mortality of fish and/or amphibians.
Such mass-mortality events are well known from the
Saar–Nahe Basin (e.g. Odernheim-lake) or the Thurin-
gian Forest Basin (e.g. Cabarz-lake, see Werneburg,
2002) in Germany. For the Is Alinus-lake, Ronchi and
Tintori (1997) have also reported repeated mass-
mortality events (here Fig. 8). From the Thuringian
Forest Basin a mass-mortality rate is known of nearly
145 Apateon dracyiensis skeletons per 1 m2 in the
Cabarz-lake (Werneburg, 2002). This rate is sometimes
higher than in the Is Alinus-lake.
Most of the known branchiosaurid populations are
neotenic. The single observed exception is Melanerpeton
gracile from Niederhäslich in the Döhlen Basin near
Dresden, with metamorphosed specimens (Werneburg, Fig. 8. Mass mortality of branchiosaurids in siltstones of the Is Alinus-
1991), whereas other populations of M. gracile from the lake in the Perdasdefogu Basin (UM 11) 9 specimens may be identified
Upper Protriton horizon of the Thuringian Forest Basin on the slab of not greater than 10 cm.
(Werneburg, 1988b), or from the Upper Buxières
Formation of the Bourbon l'Archambault Basin (Werne-
burg, 2003), are presently known only as neotenic maxilla for additional carnivorous feeding (con-
individuals. The populations of Apateon flagrifer, A. chostracans, ostracods etc.).
kontheri and Melanerpeton eisfeldi from the Thuringian C) Large sized forms, with a skull length more than
Forest and from Sardinia were probably neotenic as well. about 16 mm, fed on small vertebrates (palaeo-
The largest specimen of a branchiosaur known from the niscids, branchiosaurids, also with cannibalism).
species M. eisfeldi (skull length 35 mm) still shows an
ossified hyobranchial apparatus and branchial ossicles The latter two types are known from the branchio-
(Werneburg, 1988a). In any case, the Niederhäslich popu- saurs of Gottlob-lake (Thuringian Forest Basin), through
lation of M. gracile demonstrates that not all branchiosaurs preservation of the stomach contents along with skeletal
were neotenic, and some more terrestrial populations of remains. Type B is known from Apateon flagrifer, which
branchiosaurs were able to migrate more easily. fed on conchostracans (Werneburg, 1986b). The large
The type of food consumed by branchiosaurids sized specimens of Apateon kontheri and especially
depended on their growth stage (Werneburg 1986b, Melanerpeton eisfeldi represent type C, with their
1988a, 1989b; Boy and Sues, 2000): stomach contents including early juveniles of the
A) Small forms, up to a skull length of 8 to 9 mm, palaeoniscide Elonichthys and branchiosaurids (Werne-
employed the hyobranchial apparatus and gills burg, 1988a). Large individuals of Melanerpeton
with the branchial ossicles for exclusively plank- sembachense were cannibals and preserve smaller
ton feeding (like acanthodian fishes). specimens of the same species in the stomach contents
B) Middle sized forms, with a skull length of 10 to (Werneburg, 1989b). The same feeding strategies
15 mm, have a more solid construction of the probably applied to the Sardinian branchiosaurs.398 R. Werneburg et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383–404
Short external gills are observed in the Sardinian controlled basins and basin systems which cut into the
specimens of Apateon kontheri (Fig. 5f) and Apateon flanks of the orogen – the N–S striking Boskovice graben
flagrifer (Fig. 6a). This feature is characteristic for one in Moravia, the NW–SE striking Elbe lineament and the
ecomorphotype of branchiosaurs (Werneburg, 2002) Franconian line of the same strike in Germany, as well as
and recent larval salamanders (Duellman and Trueb, the basin systems along the N–S striking French Grand
1986), which is named “stream-type”. The construction Sillon Houiller. They form potential migration pathways,
of the external gills is important for respiration due to but none of them really cross the orogen. Perhaps cross-
the changing oxygen levels in the water. The environ- cutting deep fault systems formed additional pathways
ments of the “stream-type” branchiosaurs were pools, along NW–SE as well as NNE–SSW directions during
ponds, small lakes or parts of lakes with a high content Stephanian and Early Permian times (Ziegler and
of oxygen intercalated in river courses or situated on Stampfli, 2001). According to some authors (e.g. Bard,
their flood plains. Werneburg (2002) documented this 1997), large NE–SW dextral wrench faults or mega-
ecomorphotype, with short external gills, in specimens wrench fault “corridors” also truncated the Variscan belt.
of Apateon dracyiensis of Cabarz-lake and A. flagrifer Very likely, the branchiosaurs migrated via wetlands in
of Gottlob-lake. In contrast, representatives of Apateon the neighbouring catchment areas of the headwaters of
pedestris possessing long external gills are known from river systems, which run in opposite directions from the
the large Oderheim-lake of the Saar–Nahe Basin; watershed. Recent examples include the headwaters of the
specimens of the same species with short external gills Loire and Rhòne as well as the Rhine, Po and Danube
also occur in the Jeckenbach-lake of the same basin. which are situated very close together. Interestingly, the
Long-gilled forms belong to the “pond ecomorphotype”, populations of two or all three branchiosaur species of the Is
adapted to oxygen depletion. This feature has no Alinus-lake belong to the “stream ecomorphotype”; their
taxonomical but considerable ecological significance. migration ability in river courses was obviously very high.
A second feature of the “stream-type” is the low The next question is the location of the evolution centres
dorsal fin of the tail, which begins in the posterior half of of branchiosaurs. The oldest stratigraphical record is that of
the trunk (Werneburg, 2002). Unfortunately, soft parts Branchiosaurus salamandroides, from the oxbow lake of
or skin shadows are not preserved in the Sardinian the Westphalian D from Nýřany and Tremošna in the
material, so this feature cannot be observed directly. Central Bohemian Basin of the Czech Republic (Milner,
1980, 1986; Werneburg, 1987). Up to now that is the
5. Palaeobiogeography unique record of branchiosaurids worldwide from this early
time. Contemporaneous localities are known from North
The association of Melanerpeton eisfeldi, Apateon America (Linton or Mazon Creek) with dissorophoid and
kontheri and Apateon flagrifer was only known from the many other amphibian species but no true branchiosaur.
Thuringian Forest Basin at the northern flank of the The succeeding oldest branchiosaurs, much more common,
Variscan orogen up to now. The discovery of the same are of Stephanian age. In France we know Branchiosaurus
association of obligatorily non-marine branchiosaurids in fayoli from the Stephanian B of Commentry (Thevenin,
Sardinia, at the southern flank of the same Palaeozoic 1906) and B. cf. fayoli from Montceau-les-Mines (Civet,
mountain chain raises some interesting and fundamental 1983). The oldest record of the branchiosaur genus Apa-
questions on the diversification and migration of non- teon comes from the Stephanian C (Carboniferous–
marine animals in Northern Pangaea, which will hereafter Permian transition) of several German basins: Apateon
be discussed and – partly – answered. Independent co- intermedius from the Thuringian Forest, Ilfeld and Saale
evolution of three different species belonging to two basins (Werneburg, 1990, 1996) and Apateon sp. from the
different genera could be excluded for both occurrences. Altenglan Formation (Early Asselian) of the Saar–Nahe
Therefore, some genetic exchange must have existed Basin (Boy and Schindler, 2000). The branchiosaurid
between the two areas. Migration of exclusively aquatic genus Melanerpeton is firstly known from the Early
animals, such as fish, is strongly restricted to dewatering Asselian Ilmenau Formation of the Thuringian Forest
systems (before the appearance of active flying verte- Basin (Werneburg, 1989b). These data allow the following
brates, which could transport fish eggs by chance). In scenario: the branchiosaurs had the cradle of their evolution
contrast, semi-aquatic animals such as modern urodelans in the (Central) Bohemian basin (Westphalian D), from
like newts and salamanders could migrate between which they migrated in a first step to the intramontane
different river systems as pond-hoppers. basins of the Massif Central (Stephanian B) and in a second
How did branchiosaurids cross the watershed of the step (perhaps from the Central Bohemian Basin too) to the
Variscan mountain chain? There are some deep fault- Central German basins (Thuringian Forest, Ilfeld and SaaleR. Werneburg et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 383–404 399
Fig. 9. Palaeogeographical map with possible migration routes of branchiosaurs between Sardinia (SAR) and Thuringia (TH). Redraw and modified from
Deroin and Bonin (2003). Abbreviations: AA: Austro–Alpine; AP: Apulia; AU: Autun Basin; BAR: Barrot; BC: Basque Country; BD: Belledonne
Massif; BLC: Blanzy-Le Creusot; BRI: Brive Basin; BSK: Boskovice graben; CAT: Catalonian Cordillera; CO: Corsica; CP: Calabro–Peloritans; CRP:
Carpathians; CV: Cévennes; IB: Iberian Belt; IS: Intra-Sudetic Basin; JE: Jeffara Basin; LO: Lodève Basin; LOR: Lorraine; MOR: Morvan; PR:
Provence; RO: Rodez; SA: Saint-Affrique; SAR: Sardinia; SI: Sicily; SN: Saar-Nahe Basin; SW: Schwarzwald; SX: Saxony; TH: Thuringia; VO: Vosges.
basins; Stephanian C; Werneburg, 1988c). At the beginning peaks in bioproduction/oxygen depletion, firstly appear at
of Permian times the Variscan area was more and more the Pennsylvanian/Permian transition in Europe. They are
dismembered into an increasing number of basins. In this well known from intramontane basins, such as the
time interval the branchiosaurids were very successful in Bohemian basins and the basins of the Massif Central, as
the colonisation of about 15 basins (so far as known) in well as from perimontane basins, such as the Saar–Nahe,
Europe. the Saale and the Thuringian Forest basins. Furthermore,
All branchiosaurs show adaptations against environ- these continental basins are characterised by frequent
mental stress as discussed above. Such stress situations splitting into sub-basins and basin reorganisation caused by
occur most frequently in shallow lakes and pools and also volcanotectonic processes and events. From this resulted a
in the pelagial of large and deep lakes, which are all very high areal dynamic of amphibian populations, giving
commonly characterised by laminated sediments. But this rise to the observed rapid speciation processes (e.g.
kind of branchiosaur lake has never been discovered in the Werneburg, 1996). A single one or – more likely – some
drill core investigations during natural gas exploration in closely neighbouring basins acted as evolutionary centres,
Westphalian and Early Stephanian sediments (Bashkirian from which dispersal and gene flow took place as a
to Kasimovian) of the Variscan foredeep in North consequence of changing hydrological basin interconnec-
Germany, the North Sea and the Netherlands (Rössler, tions caused by tectonics. Periods of wet climate with
1995; Gaitzsch et al., 1999). Laminated sediments, extensive development of river systems and lake land-
pointing to a monsoonal climate with annual to seasonal scapes may have enhanced migrations, e.g. at theYou can also read
