Ecomorphological diversification of squamates in the Cretaceous

Area of Science:

• Paleontology
• Evolutionary Biology
• Vertebrate Zoology

Background:

• Squamates (lizards and snakes) are a diverse and successful group of vertebrates with a fossil record extending over 240 million years.
• Previous research indicated increased squamate species richness during the Late Cretaceous and Early Paleogene periods.
• The evolutionary pressures and timing of morphological diversification in squamates remain an active area of research.

Purpose of the Study:

• To investigate the timing of major dietary functional morphology expansion in squamates.
• To determine if morphological diversification preceded or followed species diversification.
• To understand the relationship between the Cretaceous Terrestrial Revolution and squamate feeding evolution.

Main Methods:

• Analysis of fossil records to assess tooth types and jaw size disparity over geological time.
• Correlation of squamate morphological evolution with major paleoenvironmental events, such as the Cretaceous Terrestrial Revolution.
• Comparative analysis of diversity (species richness) and disparity (morphological variation).

Main Results:

• The major expansion of squamate dietary functional morphology occurred in the mid-Cretaceous (110-90 Ma), before significant species diversification.
• Tooth types diversified substantially during this period, leading to an expansion of ecomorphospace.
• Increased jaw size disparity, particularly in marine squamates like mosasaurs, was observed in the early Late Cretaceous (95-90 Ma).
• These findings confirm a decoupling of diversity and disparity, with feeding ecomorphology established before major species radiations.

Conclusions:

• Squamate feeding ecomorphology evolved significantly in the mid-Cretaceous, driven by environmental changes and new food sources associated with the Cretaceous Terrestrial Revolution.
• Jaw and tooth innovations expanded the feeding ecomorphospace, with some expansions occurring at the extremes during the Late Cretaceous.
• The study highlights that key evolutionary innovations in feeding morphology preceded major increases in species diversity in squamates.