A fossilized specimen, once disputed by some researchers, has now been confirmed as the world’s oldest modern-type lizard, reshaping our understanding of the evolutionary timeline of lizards by millions of years.
The 205-million-year-old skeleton, discovered in Triassic rocks in a quarry near Bristol, has been identified as the earliest known member of the Squamata group, which includes all modern lizards and snakes. The new findings, published in Royal Society Open Science, confirm that the fossil belongs to the Anguimorpha suborder, which includes modern anguids and monitor lizards. This pushes back the origin of Squamata by 35 million years, redefining the evolutionary history of these reptiles.
The specimen, initially described by the University of Bristol research team as Cryptovaranoides microlanius—meaning “hidden lizard, small butcher” due to its sharp teeth and predatory nature—was first identified by Dr. David Whiteside, Dr. Sofia Chambi-Trowell, and Professor Mike Benton. The fossil’s features, including its skull and skeleton, showed clear similarities to modern lizards, particularly anguimorphs, a group that includes some of the most well-known modern reptiles, like monitor lizards.
“We anticipated that our paper would spark some debate, but we were confident that our analysis was thorough and based on the most detailed comparisons,” Dr. Whiteside explained.
However, in 2023, a competing team of scientists questioned the findings, suggesting that Cryptovaranoides might not be a lizard at all, but instead an archosauromorph—an ancient group of reptiles more closely related to crocodiles and dinosaurs. This hypothesis challenged the Bristol team’s conclusions and prompted further scrutiny.
In response, the Bristol researchers revisited their original study, re-examining the fossil and its CT scan images, which had revealed hidden anatomical details. “We had access to high-resolution scans of the specimen and additional time with the fossil to address the concerns raised by our critics,” Dr. Chambi-Trowell said. “After careful analysis, we found that the objections raised were largely unfounded.”
Professor Benton emphasized the strength of their findings, stating, “The skull, jaws, teeth, and limb bones of Cryptovaranoides all align with characteristics found in modern lizards, not crocodilians or dinosaurs.”
In their latest paper, the team details their responses to each of the criticisms, providing new photographs and 3D images of the fossil. This transparency allows other researchers to verify their results.
To further bolster their conclusions, the researchers conducted a phylogenetic analysis, comparing hundreds of anatomical features from both modern and fossil lizards, as well as archosauromorphs. The analysis consistently placed Cryptovaranoides within the lizard lineage, confirming it as the oldest known modern-type lizard.
“Our findings are now backed by comprehensive data and analysis, reaffirming our original conclusion,” Dr. Whiteside concluded. “This fossil truly represents the world’s oldest known modern-type lizard, fundamentally altering our understanding of lizard evolution.”
With this new confirmation, Cryptovaranoides not only stands as a key specimen in the history of reptiles but also challenges long-standing assumptions about the origins of lizards, offering new insights into the evolutionary path that led to the diversity of lizards and snakes we see today.
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