Miniaturization and morphological evolution in Paleozoic relatives of living amphibians: a quantitative approach

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 fac...

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Bibliographic Details
Published in:Paleobiology 2018-02, Vol.44 (1), p.58-75
Main Authors: Pérez-Ben, Celeste M, Schoch, Rainer R, Báez, Ana M
Format: Article
Language:English
Subjects:
allometry
Amphibia
Amphibians
Animal morphology
Aquatic reptiles
biologic evolution
biometry
Body size
Chordata
Evolution
Frogs
Genomes
Labyrinthodontia
Miniaturization
Morphology
Museums
Ontogeny
Paleontology
Paleozoic
Phylogenetics
phylogeny
regression analysis
Reptiles & amphibians
size
Size reduction
skull
statistical analysis
Temnospondyli
Tetrapoda
Vertebrata
vertebrate
Vertebrates
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Summary: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.
ISSN:0094-8373
1938-5331
DOI:10.1017/pab.2017.22