Today, lepidosaurs—encompassing lizards, snakes, and the unique New Zealand tuatara—rank among Earth’s most diverse vertebrates. Yet, their early evolutionary journey is still not fully understood. A recently unearthed jaw fossil from southern Brazil is aiding paleontologists in unraveling the intricacies of early human anatomy and evolution. This fossil belongs to Karguninia Enigmatica, a small lepidosaur relative that roamed the Earth during the late Triassic period, alongside some of the earliest dinosaurs.
A Late Triassic landscape in southern Brazil, featuring Karguninia Enigmatica as observed by sauropod dinosaurs Macrocollum itaquii. Image credit: Marcio L. Castro.
Karguninia Enigmatica existed during the early Norian period of the late Triassic, approximately 225 million years ago.
This fascinating creature shared its habitat with early dinosaurs, primitive mammal relatives, ancestral crocodilians, and several ancestors of the tuatara.
Initially discovered in 2010, Karguninia Enigmatica was identified from a single lower jaw fragment, providing crucial insights into its anatomical features.
Belonging to the Lepidosauromorpha group, this species is part of a larger lineage that eventually led to modern lepidosaurids.
Determining Karguninia Enigmatica‘s exact position within this phylogenetic tree has long intrigued paleontologists.
“Lepidosauria encompasses a diverse array of species, including squamates and rhinocephalan Mucaci,” noted Dr. Lissy Vitoria Soares Damke from the Federal University of Santa Maria.
“The origins date back to the end of the Permian, marking the divergence of stem lineages Lepidosauromorpha and Arcosauromorpha.”
“Several species within the lepidosauromorph lineage have exhibited unstable phylogenetic placements.”
In Brazilian strata, this lineage is exemplified by Karguninia Enigmatica, a rare taxon represented solely by a fragmentary left dentary tooth.
Upon its discovery in 2010, paleontologists proposed that Karguninia was a non-rhinocephalic lepidosaur based on its dental characteristics and a suspected subodontian implantation pattern.
Shared dental traits with Calgunia and Ikarosaurus, a cueneosaur from the Late Triassic of the United States, led to further discussions about its classification.
However, researchers concluded that these features alone did not justify its reassignment to Ikarosaurus or a closely related taxon.
A new specimen of Karguninia Enigmatica was unearthed at the Linha San Luis site in Facinal do Soturno, Rio Grande do Sul, Brazil.
This fossil comprises a fragment of the left lower jaw measuring less than 9 mm, but includes 12 preserved teeth, suggesting a potential total of 18 teeth.
The researchers utilized micro-CT scans to analyze the internal structures of the specimen, allowing them to trace the trigeminal nerve, which governs facial sensation and motor control.
The branching neural patterns observed in Karguninia Enigmatica closely resemble those found in modern lepidosaurs.
“Karguninia Enigmatica likely perceived its environment similarly to its modern relatives, particularly regarding trigeminal sensory inputs,” the research team stated.
Through large-scale computational phylogenetic analysis, scientists confirmed that Karguninia Enigmatica consistently aligns as a non-lepidosaur lepidosaur, supporting its classification as an early diverging branch predating true lepidosaurs.
“For the first time, its phylogenetic position has been analyzed computationally, and results place this species among non-lepidosauromorphs, reinforcing prior assumptions,” the authors emphasized.
For further details, refer to their research paper, published this month in anatomical records.
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Lissie Vitoria Soares Damke et al. present new fossil insights unveiling unusual lepidosaur tooth anatomy of Karguninia Enigmatica from the late Triassic in southern Brazil, published online on July 4, 2026, in anatomical records. doi: 10.1002/ar.70268
Source: www.sci.news