The tiniest newly-discovered fossils can upend paleontologists' understanding of the past. SciTech Daily reports that a team of paleontologists from Virginia Tech and the US Petrified Forest National Park uncovered the first "unmistakable" Triassic-era caecilian fossil, which is determined as the oldest known caecilian fossils ever found.
The findings expand the record of this tiny, burrowing animal by up to 35 million years. More so, it bridges an 87-million-year-old gap in the amphibian-like animal's historical fossil record.
Newly-Discovered Caecilian Fossils Highlights the Importance of Fossil Record
The newly-discovered fossils extend the history of caecilians of up to 35 million years back to the Triassic era, which is about 250 million to 200 million years ago. Prior to the study, only 10 fossil caecilian occurrences were known and they were dated back to Early Jurassic Period, which is about 183 million years ago.
However, DNA studies reveal that the creature's evolutionary origins could be traced back to the Permian eras or some 370 million to 270 million years ago, which indicates a gap when no fossils were found. But the new study, titled "Triassic Stem Caecilian Supports Dissorophoid Origin of Living Amphibians" published in the journal Nature, addresses the 87-million-year gap.
Doctoral candidate Ben Kligman explained that the discovery of the oldest caecilian fossils highlights the crucial nature of the fossil record. Fossilized caecilians are extremely rare and they are only accidentally found when paleontologists are looking for fossils of other more common animals.
Kligman and Idaho State University Ph.D. student Xavier Jenkins discovered the fossils in 2019 while they were processing fossiliferous sediment from Thunderstorm Ridge via a microscope. Kligman named the fossil Funcusvermis gilmorei and determined that it is approximately 220 million years old when Arizona was positioned near the equator at the central part of the Pangaea.
The name "Funcusvermis" was inspired by the 1972 song "Funky Worm", which is a favorite song of the authors that they usually play while excavating fossils at Thunderstorm Ride. Meanwhile, the "gilmorei" was taken from the name of Ned Gilmore who inspired Kligman in his interest in fossils and amphibians.
Differences Between Modern Caecilians From Their Ancient Counterparts
The 87-million-year gap in the historical record of caecilians led to a long debate amongst scientists over their relationships with other amphibians, such as frogs and salamanders, Science Daily reported. Kligman said that the Funcusvermis suggest caecilians have been restricted to humid equatorial settings due to physiological constraints and by the drift of continent plates.
Today, modern caecilians are limbless amphibians with cylindrical bodies as well as compact, bullet-shaped head that aids in burrowing underground. They can now only be found in South and Central America, Africa, and southern Asia, and spend their days digging in leaf litter or dirt in search of food such as worms and insects.
Scientists have found it challenging to research caecilians due to their subterranean life. Modern caecilians, according to Kligman, are "eyeless sock puppets with worm bodies."
On the other hand, Funcusvermis has skeletal traits that are more similar to early frog and salamander fossils, bolstering evidence for a shared origin and close evolutionary link between caecilians and these amphibians.
They also share skeletal characteristics with an ancient group of frogs that paleontologists call classified as Dissorophoid temnospondyls by paleontologists.
Kligman noted that unlike contemporary caecilians, Funcusvermis lacks several adaptations associated with subterranean burrowing, indicating a delayed acquisition of traits associated with an underground existence in the early stages of caecilian development.
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