Шинээр илрүүлсэн олдвор нь гүрвэл, могой болон туатарагийн өвөг дээдсийн хувьслын үе шатыг ойлгоход чухал ач холбогдолтой юм.
Бразилын өмнөд хэсэгт орших Линха Сан Луиз талбайгаас 225 сая жилийн тэртээх Триасын галавын үед амьдарч байсан Cargninia enigmatica хэмээх ховор төрлийн хэвлээр явагчийн эрүүний ясыг олжээ. Уг олдвор нь 2010 онд анх бүртгэгдсэн, маш бага хэмжээний ясны хэлтэрхий дээр суурилсан судалгааг гүйцээх боломжийг эрдэмтдэд олгож байна. 9 миллиметрээс бага урттай энэхүү яс нь 12 шүдтэй бөгөөд амьд ахуйдаа нийт 18 шүдтэй байсныг илтгэж байна.
Судлаачид орчин үеийн микро-CT сканнердах технологийг ашиглан олдворын дотоод бүтцийг гэмтээлгүйгээр шинжилжээ. Энэхүү шинжилгээгээр нүүрний мэдрэхүй болон эрүүний хөдөлгөөнд оролцдог гурвалсан мэдрэлийн сувгийн бүтэц нь өнөөгийн гүрвэлүүдтэй төстэй болохыг тогтоосон байна. Мөн уг амьтны шүд суултын хэлбэр нь АНУ-аас олдсон Icarosaurus төрлийн хэвлээр явагчтай ижил төстэй шинжүүдийг агуулж байгааг судалгааны баг онцолжээ.
Филогенетик шинжилгээгээр Cargninia enigmatica нь Лепидозавроморфа (Lepidosauromorpha) буюу орчин үеийн гүрвэл, могойнуудын үүсэл болсон бүлэгт хамаарах нь дахин нотлогдов. Хэдийгээр энэ бүлгийн амьтад дэлхийн сээр нуруутан амьтдын хамгийн олон төрөл зүйлтэй бүлгүүдийн нэг боловч тэдний хувьслын эхэн үеийн олдвор ховор байдаг. Энэхүү шинэ олдвор нь эртний хэвлээр явагчдын хувьслын мод дахь байр суурийг тодорхой болгож, шинжлэх ухааны мэдлэгийн цоорхойг нөхөж байна.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
A tiny fossil jaw discovered in southern Brazil is helping scientists fill a gap in the early history of reptiles that eventually gave rise to modern lizards, snakes, and the tuatara. The specimen belongs to Cargninia enigmatica, a rare species that lived around 225 million years ago during the Late Triassic.
The newly described reptile fossil provides researchers with anatomical details that were missing from the original discovery made more than a decade ago. Combined with modern imaging techniques and a new phylogenetic analysis, the remains offer a clearer view of where this elusive reptile fits in the evolutionary tree.
Today, lepidosaurs are among the most diverse vertebrates on Earth, yet their earliest evolution is still difficult to reconstruct because fossils from the group’s first members are uncommon. Cargninia enigmatica is part of Lepidosauromorpha, the broader lineage that eventually gave rise to living lepidosaurs, making every new fossil especially valuable.
The animal lived during the early Norian age of the Late Triassic and shared its habitat with some of the first dinosaurs, mammal relatives, primitive crocodile-line reptiles, and several early relatives of the tuatara. Until now, the species was known from a single fragment of its lower jaw, leaving many aspects of its anatomy unresolved.
Second Jaw Adds Anatomical Evidence
Cargninia enigmatica was first described in 2010 from a fragmentary left dentary. That single fossil formed the basis for every study of the species, making its evolutionary relationships difficult to test.
The new specimen was recovered from the Linha São Luiz site in Faxinal do Soturno, in Brazil’s Rio Grande do Sul State, where the original fossil was found. Although the partial left lower jaw measures less than 9 millimeters long, it preserves 12 teeth and shows that the complete dentary likely carried as many as 18 teeth.
The researchers saitd that Cargninia enigmatica is still the only known representative of this stem lineage from Brazilian strata. When the species was first described, its small teeth, measuring roughly 0.4 to 0.5 millimeters across from front to back, and a proposed subacrodont implantation pattern led scientists to identify it as a non-rhynchocephalian lepidosaur. The original study also noted that:
“They also noted similarities between the tooth implantation ofCargniniaand that ofIcarosaurus, a kuehneosaurid reptile from the Late Triassic Lockatong Formation of the United States.”
Micro-CT Scans Uncover Hidden Structures
To learn more about the fossil, the team examined the jaw using micro-CT scanning, allowing them to study its internal anatomy without damaging the specimen.
The scans revealed the course of the trigeminal nerve, which is involved in facial sensation and jaw movement. As reported in The Anatomical Record, the nerve’s branching pattern closely matches the arrangement seen in living lepidosaurs.
The researchers say this suggests reptile likely processed trigeminal sensory information in much the same way as its living relatives. The new fossil also provides anatomical information that could not be observed in the fragment originally described in 2010.
An Early Place on the Evolutionary Tree
For the first time, researchers also included Cargninia enigmatica in a large phylogenetic analysis. The species consistently emerged as a non-lepidosaur lepidosauromorph, backing up earlier ideas about its place in reptile evolution.
The study also highlights how much remains to be learned about the group’s earliest history. Lepidosauromorpha and Archosauromorpha diverged near the end of the Permian, but several early members of the lepidosauromorph lineage still don’t have a clear place on the evolutionary tree.
Enjoyed this article? Subscribe to our free newsletter for engaging stories, exclusive content, and the latest news.
