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Re: [dinosaur] Lissamphibian origins from dissorophoids through miniaturization or from immature conditions



Actually, this paper says nothing about lissamphibian origins, except:
 
1) it presupposes that the lissamphibians are dissorophoids, and uses that to argue that therefore the other dissorophoids are interesting enough to be published on in Paleobiology;
 
2) it shows in detail that there's no miniaturization separable from a bit of paedomorphosis going on either in non-lissamphibian dissorophoids or even among the earliest lissamphibians – any miniaturization-related phenomena in caecilians and batrachians ( = frogs + salamanders) must have happened separately, not during the origin of Lissamphibia. This holds regardless of the phylogenetic position of Lissamphibia.
 
Gesendet: Freitag, 26. Januar 2018 um 08:11 Uhr
Von: "Ben Creisler" <bcreisler@gmail.com>
An: dinosaur-l@usc.edu
Betreff: [dinosaur] Lissamphibian origins from dissorophoids through miniaturization or from immature conditions
 
Celeste M. Pérez-Ben, Rainer R. Schoch & Ana M. Báez (2018)
Miniaturization and morphological evolution in Paleozoic relatives of living amphibians: a quantitative approach.
Paleobiology (advance online publication)
 
Miniaturization has been defined as the evolution of extremely small adult size in a lineage. It does not simply imply the decrease of the body size but also involves structural modifications to maintain functional efficiency at a strongly reduced size. Miniaturization has been proposed as a key factor in the origin of several major tetrapod clades. Current hypotheses propose that the living amphibians (lissamphibians) originated within a clade of Paleozoic dwarfed dissorophoid temnospondyls. Morphological traits shared by these small dissorophoids have been interpreted as resulting from constraints imposed by the extreme size reduction, but these statements were based only on qualitative observations. Herein, we assess quantitatively morphological changes in the skull previously associated with miniaturization in the lissamphibian stem lineage by comparing evolutionary and ontogenetic allometries in dissorophoids. Our results show that these features are not comparable to the morphological consequences of extreme size reduction as documented in extant miniature amphibians, but instead they resemble immature conditions of larger temnospondyls. We conclude that the truncation of the ancestral ontogeny, and not constraints related to miniaturization, might have been the factor that played a major role in the morphological evolution of small dissorophoids. Based on our results, we discuss the putative role of miniaturization in the origin of lissamphibians within Dissorophoidea.
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