Evolutionary relationship between lizards and dinosaurs

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Evolutionary Origins: Lizards, Dinosaurs, and Major Reptile Groups

Lizards and dinosaurs both belong to the larger group of reptiles, but they evolved along separate branches early in reptile history. Lizards are part of the Lepidosauromorpha, which includes squamates (lizards, snakes) and sphenodontians (tuataras), while dinosaurs are part of the Archosauromorpha, which also includes crocodiles and birds. These two groups split from a common diapsid ancestor, meaning they share a distant evolutionary relationship but are not directly descended from one another 12.

Lepidosauromorpha and Archosauromorpha: Divergent Evolutionary Paths

The early evolution of lepidosauromorphs (lizards and their relatives) is less well-documented than that of archosauromorphs (dinosaurs and their relatives) due to a patchy fossil record. However, recent fossil discoveries, such as the Triassic reptile Taytalura, have helped clarify that lepidosauromorphs were already distinct from archosauromorphs by the Triassic period. This means that the ancestors of lizards and dinosaurs were evolving separately for at least 240 million years .

Squamate (Lizard) Evolution and Fossil Record

Lizards, snakes, and amphisbaenians together form the Squamata, the largest group of living reptiles. Although the fossil record for early squamates is incomplete, indirect evidence suggests that squamates had already evolved by the middle Triassic, around the same time as early dinosaurs. However, the earliest confirmed squamate fossils are from the Jurassic period, indicating a significant gap in the fossil record during which key features of lizards evolved .

Dinosaur Evolution and Classification

Dinosaurs are divided into two main groups based on hip structure: Saurischia ("lizard-hipped") and Ornithischia ("bird-hipped"). Despite the name, "lizard-hipped" dinosaurs are not closely related to modern lizards. Instead, this term refers to the shape of their pelvic bones, not their evolutionary relationship. Dinosaurs and lizards evolved independently after the initial split between lepidosauromorphs and archosauromorphs .

Coexistence and Ecological Interactions

During the Mesozoic era, lizards and dinosaurs coexisted, but they occupied different ecological niches. Fossil evidence shows that some dinosaurs, like the small predatory Microraptor, even preyed on lizards, indicating direct interactions between these groups in ancient ecosystems .

Conclusion

Lizards and dinosaurs share a distant common ancestor among early diapsid reptiles, but they represent two distinct evolutionary lineages: lepidosauromorphs (lizards) and archosauromorphs (dinosaurs). Their evolutionary paths diverged in the Triassic period, and while they coexisted for millions of years, they are not directly related beyond their shared reptilian heritage 125.

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Most relevant research papers on this topic

A Triassic stem lepidosaur illuminates the origin of lizard-like reptiles

The discovery of Taytalura alcoberi gen. et sp. nov. from the Late Triassic of Argentina suggests that lizard-like reptiles originated earlier than previously thought, with a broader geographical distribution than previously thought.

Rigorous Journal

2021·

29citations

·R. Martínez et al.

At the feet of the dinosaurs: the early history and radiation of lizards

Squamates evolved by the middle Triassic and diversified into major lineages before the end of this period, but the early squamate fossil record is extremely patchy, constraining palaeobiogeographic discussions and limiting our understanding of squamate skull kinesis.

Literature ReviewHighly Cited

2003·

254citations

·S. Evans

Repeated Evolution of Herbivorous Crocodyliforms during the Age of Dinosaurs

Herbivorous crocodyliforms were more common than previously thought during the Mesozoic Era and lived alongside omnivorous or herbivorous synapsids, indicating herbivory was a beneficial dietary strategy.

Very Rigorous JournalHighly Cited

2019·

84citations

·K. Melstrom et al.

Microraptor with Ingested Lizard Suggests Non-specialized Digestive Function

Microraptor zhaoianus, a small dromaeosaurid from the Early Cretaceous Jehol Biota, ingested a previously unrecognized lizard species, suggesting a non-specialized digestive function and a closer relationship between paravians

Very Rigorous Journal

2019·

25citations

·J. O'Connor et al.

Relationships between dinosaurs

Dinosaurs are split into two main clades: Saurischia (lizard-hipped) and Ornithischia (bird-hipped), with the dynamic Earth influencing their evolution through changes in latitude, longitude, and climatic conditions.

2017·

0citations

·D. Norman

The functional origin of dinosaur bipedalism: Cumulative evidence from bipedally inclined reptiles and disinclined mammals.

Dinosaur bipedalism evolved for enhanced cursoriality, with modern lizards serving as analogs, and is more prevalent among diapsids than mammals.

2017·

24citations

·W. Persons et al.

The origin of squamates revealed by a Middle Triassic lizard from the Italian Alps

Megachirella wachtleri is the oldest known stem squamate, filling the fossil gap in lizard origins and indicating a more gradual acquisition of squamatan features in diapsid evolution than previously thought.

Rigorous JournalHighly Cited

2018·

191citations

·T. Simões et al.

Cortical Evolution: Introduction to the Reptilian Cortex

The reptilian brain shares evolutionary, anatomical, developmental, physiological, and functional features with other amniote species, making it a reasonable concept for a "reptilian brain."

2016·

9citations

·G. Laurent et al.

Phylogenetic relationships among the phrynosomatid sand lizards inferred from mitochondrial DNA sequences generated by heterogeneous evolutionary processes.

The mitochondrial DNA sequences of phrynosomatid sand lizards support recent divergences and monophyly of "earless" taxa, with a single species (Holbrookia maculata) possibly consisting of multiple species.

Highly Cited

2000·

83citations

·James C. Wilgenbusch et al.

Developmental and evolutionary novelty in the serrated teeth of theropod dinosaurs

Theropod dinosaurs' serrated teeth evolved to facilitate their hypercarnivorous diet, potentially playing a role in their initial radiation and success as terrestrial apex predators.

2015·

62citations

·K. Brink et al.

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