Мьянмараас олдсон эртний хув нь өнөөгийн гүрвэлүүдийн махчин амьтнаас зугтахдаа сүүлээ тасдан хаядаг хамгаалалтын аргыг цэрдийн галавын үед ч ашигладаг байсныг баталлаа.
Тель-Авивын их сургуулийн палеонтологич Долев Фабрикантаар ахлуулсан судалгааны баг Мьянмарын Качин мужийн Хукаунг хөндийгөөс олдсон 99 сая жилийн настай хуваас гүрвэлийн тасарсан сүүлийг илрүүлжээ. Palaeontologia Electronica сэтгүүлд нийтлэгдсэн уг олдвор нь гүрвэлийн сүүл тасдах (caudal autotomy) зан үйлийн хувьслын түүхийг судлах чухал баримт болж байна. Эрдэмтэд рентген микро-компьютерын томографийн аргаар сүүлний бүтцийг шинжлэхэд тасарсан хэсгийн булчингийн эд нь өнөөгийн гүрвэлүүдийн сүүлээ зориудаар хаях үед үүсдэгтэй ижил,楔 хэлбэртэй байсныг тогтоожээ.
Сүүлээ тасдах нь гүрвэлийн хувьд махчин амьтны анхаарлыг сарниулж, амьд гарах боломж олгодог боловч хөдөлгөөн, өсөлт болон нөхөн үржихүйд сөрөг нөлөөтэй өндөр өртөгтэй стратеги юм. Судлаачид уг сүүл хув дотор хэрхэн хадгалагдсан талаар хоёр таамаглал дэвшүүлж байгаа бөгөөд үүнд гүрвэл давирхайд наалдах үедээ эсвэл махчин амьтантай тэмцэлдэх явцдаа сүүлээ тасалсан байж болзошгүй гэж үзжээ. Аль ч тохиолдолд энэхүү олдвор нь сүүл тасдах үйл явц бүрэн гүйцэд баримтжуулагдсан анхны тохиолдол болж байна.
Энэхүү судалгаа нь сүүл нөхөн төлжих чадвартай холбоотой генүүд дор хаяж 99 сая жилийн өмнө үүссэн байж болохыг харуулж байна. Орчин үеийн гүрвэлүүдийн гуравны хоёр нь сүүлээ тасдах чадвартай байдаг нь энэхүү хамгаалалтын стратеги нь эрт дээр үеэс үргэлжилж ирсэн болохыг баталж байна. Эрдэмтдийн үзэж буйгаар хув нь эртний амьтдын зан үйл болон үйл ажиллагааны хариу урвалыг хадгалан үлдэж, палеонтологийн судалгаанд чухал ач холбогдолтой мэдээллийг өгдөг ажээ.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
A small piece of amber from Myanmar has preserved a defensive trick that lizards still rely on today: leaving part of the tail behind to escape a predator. The fossil offers direct evidence that this strategy was already at work in mid-Cretaceous forests.
Tail shedding is common among living lizards. When threatened, an animal can abandon its tail while fleeing, and the detached piece may keep moving, distracting the attacker long enough for the lizard to get away. It sounds like a neat bargain, but it comes with costs that touch locomotion, growth, reproduction and other parts of life.
For all its prevalence, the evolutionary history of the behavior has been hard to pin down. A team led by Tel Aviv University paleontologist Dolev Fabrikant now reports a specimen that changes that, published in the journal Palaeontologia Electronica.
A Tail Frozen in Resin
The researchers examined a piece of mid-Cretaceous amber containing a detached lizard tail, its skin and muscle tissue remarkably well preserved. It comes from a mine in the Hukawng valley, in Kachin state, northern Myanmar.
According to the scientists, the specimen was legally acquired in 2022 through commercial channels and is permanently housed in the publicly accessible research collection of the Steinhardt Museum of Natural History at Tel Aviv University.
Using X-ray micro-computed tomography, the team analyzed the tail’s structure and compared it with the tails of living skinks and lizards. The scans showed a ring of muscle tissue around the break, arranged in a rosette or wedge pattern. Living lizards form this structure when their muscles contract during a deliberate tail drop. The tail itself belonged to a relative of monitor lizards or of lacertids, the group that includes European wall lizards.
How Did It End Up There?
The authors of the study say the circumstances behind the tail‘s preservation remain uncertain, and they offer two scenarios. In the first, a tree-dwelling lizard became stuck in the resin and escaped by dropping its tail. In the second, a predator caught the lizard, lost the tail in the struggle and dropped it onto the sticky surface. Either way, what matters is that a completed event was captured. In the researchers’ words:
“By documenting a completed autotomy event rather than anatomical predisposition alone, the specimen provides a behavioral calibration point for the evolution of the predominant antipredator strategy in squamates.”
Why Caudal Autotomy Matters
Fabrikant and colleagues describe caudal autotomy, the voluntary shedding of the tail, as “one of the most distinctive and best-studied antipredator behaviors” in present-day squamate reptiles, the most diverse clade of terrestrial vertebrates. The mechanism relies on contracting muscles along specialized fracture planes. The behavior is ecologically consequential and energetically costly, influencing locomotor performance, growth, social interactions and reproduction, and it may even inspire novel biomimetic technologies.
Phylogenetic studies, the team notes, indicate that the behavior arose at the root of squamate phylogeny and is present in at least two thirds of modern-day lineages, with repeated secondary losses.
There is a regeneration angle too. Because autotomy in living lizards is often developmentally coupled to tail regenerative capacity, its confirmed presence in the mid-Cretaceous also constrains the antiquity of associated regenerative programs. The authors conclude that candidate genes involved in tail regeneration may have arisen by at least 99 million years ago. The study team added that:
“More broadly, it showcases that amber can preserve discrete defensive events and functional responses, thereby extending the deep-time behavioral resolution of the vertebrate fossil record.”
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