Assessing ontogenetic maturity in extinct saurian reptiles

Area of Science:

• Vertebrate palaeontology
• Evolutionary biology
• Reptile anatomy

Background:

• Morphological interpretation is fundamental to identifying taxa and forming evolutionary hypotheses.
• Assessing maturity in saurian reptiles (Lepidosauria and Archosauria) is difficult due to disparity, ambiguity, and inconsistent terminology.
• Understanding saurian ontogeny is crucial for studying evolutionary changes, population structure, palaeoecology, and life-history strategies.

Purpose of the Study:

• To critically examine how saurian reptile maturity has been diagnosed by compiling and analyzing over 900 literature instances.
• To review and clarify the inconsistent terminology and methods used in saurian maturity assessment.
• To provide recommendations for improved clarity, cross-study coherence, and future research directions.

Main Methods:

• Compilation of a novel database of >900 literature instances of saurian maturity assessment.
• Critical review of terminology (e.g., 'juvenile', 'mature') and diagnostic methods across major saurian groups.
• Integration of data from both extant and extinct taxa to provide a comprehensive overview.

Main Results:

• Identified significant methodological and terminological ambiguity in current saurian maturity assessments.
• Documented various methods used across saurian groups, highlighting pitfalls and best practices.
• Highlighted the need for integrating extant and fossil data for robust maturity assessments.

Conclusions:

• Recommended adding a standardized 'Ontogenetic Assessment' subsection to systematic palaeontology descriptions.
• Advocated for using phylogenetic context and multiple, independent lines of evidence for maturity diagnoses.
• Emphasized the necessity of integrating well-represented growth series from extant taxa with the fossil record.