Osmotic tolerance and habitat of early stegocephalians: indirect evidence from parsimony, taphonomy, palaeobiogeography, physiology and morphology - The Terrestrialization Process: Modelling Complex Interactions at the Biosphere-Geosphere Interface - page 161

Reptiliomorpha Amphibia

268.0
270.6 270.6
275.6 275.6

Roadian
Kungurian

Artinskian

284.4 284.4

Sakmarian

294.6 294.6
299.0 299.0
303.9 303.9
306.5 306.5

Asselian
Gzhelian
Kasimovian
Moscovian

311.7 311.7

Bashkirian

318.1 318.1

Serpukhovian

326.4 326.4

Amphibia Amphibia Amphibia Amphibia
Tetrapoda Tetrapoda Tetrapoda Tetrapoda Tetrapoda

Visean

Move onto land?

345.3 345.3

Tournaisian

Loss of caudal lepidotrichia
Appearance of pentadactyly

359.2 359.2

Famennian

374.5 374.5

Appearance of the limbs Frasnian

Stegocephali Stegocephali
Stegocephali Stegocephali
Stegocephali

385.3 385.3

Givetian

391.8 391.8

Eifelian

397.5 397.5

Emsian

407.0 407.0
411.2 411.2
416.0

Pragian
Lochkovian

Tetrapodomorpha Tetrapodomorpha Tetrapodomorpha Tetrapodomorpha Tetrapodomorpha

Fig. 3. Time-calibrated supertree of sarcopterygians emphasizing early tetrapodomorphs showing the evolution of
habitat according to traditional interpretations. White: marine; grey (green in the electronic version): brackish water;
black: freshwater. States were ordered. The phylogeny was compiled using the Stratigraphic Tools (Josse et al. 2006)
for Mesquite 2.01 (Maddison & Maddison 2007) using the geological timescale of Gradstein et al. (2004) with trees and
taxonomies from Smithson (1980), Foreman (1990), Laurin (1998a, c), Beaumont & Smithson (1998), Laurin et al.
(2000), Zhu et al. (2001), Ruta et al. (2002, 2007), Zhu & Yu (2002), Anderson et al. (2003), Laurin (2004), Lebedev
(2004), Long & Gordon (2004), Vallin & Laurin (2004), Clack & Finney (2005), Laurin & Soler-Gij´n (2006), Clack
(2007) and Ruta & Coates (2007).

that interpretation, most stegocephalian remains are
interpreted as autochtonous elements which were
not transported far from their habitat. This character
includes a strong phylogenetic signal ( p , 0.0001).
This optimization differs from the former in that the
move from a marine environment to a marginal
marine environment probably took place in the
smallest clade which includes panderichthyids and
stegocephalians. That marginal marine environment
appears to have been the cradle of stegocephalian
diversification,

taphonomic artefact (this is the environment into
which most fossiliferous sediments in which stego-
cephalians could be preserved were deposited).
There is little evidence that some early stegoce-
phalian species were freshwater stenohaline forms,
although this could reflect the same taphonomic
artefact and could result from the difficulty of
demonstrating the freshwater nature of a locality.
If we take this evidence at face value, the relative
intolerance of most lissamphibians to moderately
saline brackish (more than about 10‰) water or although that may well be a