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Determinate growth is predominant and likely ancestral in squamate reptiles

  • Frýdlová, Petra1, 2
  • Mrzílková, Jana3, 2
  • Šeremeta, Martin3, 2
  • Křemen, Jan3, 2
  • Dudák, Jan4
  • Žemlička, Jan4
  • Minnich, Bernd5
  • Kverková, Kristina1
  • Němec, Pavel1
  • Zach, Petr3, 2
  • Frynta, Daniel1
  • 1 Department of Zoology, Faculty of Science, Charles University, Prague 12844 , (Czechia)
  • 2 Department of Anatomy, Third Faculty of Medicine, Charles University, Prague 100 00 , (Czechia)
  • 3 Specialized Laboratory of Experimental Imaging, Third Faculty of Medicine of Charles University, Institute of Technical and Applied Physics and Faculty of Bioengineering, Prague 100 00 , (Czechia)
  • 4 Institute of Experimental and Applied Physics, Czech Technical University in Prague, Prague 110 00 , (Czechia)
  • 5 Department of Biosciences, University of Salzburg, Hellbrunnerstrasse 34, Salzburg 5020 , (Austria)
Published Article
Proceedings of The Royal Society B Biological Sciences
The Royal Society
Publication Date
Dec 23, 2020
DOI: 10.1098/rspb.2020.2737
PMID: 33352069
PMCID: PMC7779497
PubMed Central


Body growth is typically thought to be indeterminate in ectothermic vertebrates. Indeed, until recently, this growth pattern was considered to be ubiquitous in ectotherms. Our recent observations of a complete growth plate cartilage (GPC) resorption, a reliable indicator of arrested skeletal growth, in many species of lizards clearly reject the ubiquity of indeterminate growth in reptiles and raise the question about the ancestral state of the growth pattern. Using X-ray micro-computed tomography (µCT), here we examined GPCs of long bones in three basally branching clades of squamate reptiles, namely in Gekkota, Scincoidea and Lacertoidea. A complete loss of GPC, indicating skeletal growth arrest, was the predominant finding. Using a dataset of 164 species representing all major clades of lizards and the tuataras, we traced the evolution of determinate growth on the phylogenetic tree of Lepidosauria. The reconstruction of character states suggests that determinate growth is ancestral for the squamate reptiles (Squamata) and remains common in the majority of lizard lineages, while extended (potentially indeterminate) adult growth evolved several times within squamates. Although traditionally associated with endotherms, determinate growth is coupled with ectothermy in this lineage. These findings combined with existing literature suggest that determinate growth predominates in both extant and extinct amniotes.

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