Paleontologists have identified a new fossil jaw from southern Brazil that clarifies the evolutionary position of Cargninia enigmatica, a 225-million-year-old reptile. According to a study published in The Anatomical Record by Dr. Lísie Vitória Soares Damke and colleagues, the specimen confirms that this tiny creature was a non-lepidosaur lepidosauromorph, representing a branch that diverged before the rise of modern lizards, snakes, and the tuatara.
Anatomy of the Triassic Specimen
The new fossil, a partial left lower jaw measuring less than 9 mm, was recovered from the Linha São Luiz site in Faxinal do Soturno, Rio Grande do Sul. While the original 2010 description of the species relied on a single jaw fragment, the new specimen preserves 12 teeth. Researchers estimate the animal would have possessed up to 18 teeth in its dentary.
To understand the creature’s sensory capabilities, the team utilized micro-CT scanning. This technology allowed them to trace the path of the trigeminal nerve, which manages motor and sensory functions in the jaw. The study reports that the nerve’s branching pattern closely mirrors that of living lepidosaurs, suggesting Cargninia enigmatica perceived its environment through similar sensory inputs.
Solving the Lepidosauromorph Family Tree
For years, the classification of Cargninia enigmatica remained a point of debate among researchers. Initial 2010 interpretations suggested it might be a non-rhynchocephalian lepidosaur, drawing comparisons to Icarosaurus, a kuehneosaurid reptile found in the United States. However, the lack of complete skeletal data left its placement on the evolutionary tree unstable.
By running a large computational phylogenetic analysis, the research team placed the species firmly among non-lepidosaur lepidosauromorphs. This confirms that the taxon belongs to the broader lineage that eventually produced modern lepidosaurs but branched off before the group fully evolved. This distinction helps fill a critical gap in understanding how reptile lineages diverged at the end of the Permian period.
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Frequently Asked Questions
- What is Cargninia enigmatica?
- It is a rare, small reptile that lived approximately 225 million years ago in what is now Brazil. It belongs to the lepidosauromorph lineage, which includes the ancestors of modern lizards and the tuatara.
- Why was the classification of this fossil difficult?
- For years, the species was known only from a single, incomplete jaw fragment, making it difficult to determine its exact relationship to other early reptiles.
- What did the micro-CT scan reveal?
- The scan showed that the branching pattern of the trigeminal nerve in Cargninia enigmatica is similar to that of living lepidosaurs, suggesting similar sensory and motor control.
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