The Galapagos Islands are equatorial islands in the eastern Pacific Ocean, approximately 900 kilometers (500 miles) west of northern South America. Scientists have identified more than 1,500 native species of birds, reptiles, and other animals that live only on these islands, which are known for their biodiversity. One famous example is the Galapagos tortoise. This giant tortoise can weigh up to 400 kilograms (nearly 1,000 pounds), making it the largest cold-blooded land animal.
Scientists have speculated about the evolution of Galapagos tortoises. Charles Darwin visited this island for the first time aboard the HMS. Beagle 1835. Researchers agree These turtles originate from the South American continent, but it is still unknown how they migrated to the island and when they reached their impressive size.
Some scientists believe that Galapagos giant tortoises became large after immigrating to the islands, while others argue that the tortoises grew large before leaving the mainland. Proponents of the “then” hypothesis cite several examples in which island birds and snakes similarly grew larger than continental birds and snakes. Proponents of the “before” hypothesis argue that gigantism may have helped turtles cross oceans. They suggest that larger turtles have slower metabolisms, so they lose less body heat in the water, and have larger, more buoyant shells.
Researchers from the United States and Ecuador recently reconsidered the Galapagos tortoise debate based on new fossils collected off the coast of Ecuador. Paleontologists have previously discovered fossilized large turtles in southern South America, which they claim are ancestors of Galapagos giant tortoises. However, these fossils are located far south of the equatorial islands, and scientists have found no direct evidence that they are related to the Galapagos species. These researchers therefore wanted to test giant tortoise fossils found near the island.
The new turtle fossil was composed of shell material collected from sandstone of the Tablazo Formation on mainland Ecuador. The researchers explained that these fossils were only briefly described by researchers studying mammal fossils in the 1950s, so they may have been missed by earlier scientists. Researchers estimated that the fossil belonged to a turtle that was more than 1 meter (or 3 feet) long, and about the size of a Galapagos giant tortoise. Past researchers Researchers narrowed down the age of the Tabrazo Formation to between 780,000 and 12,000 years, making it the oldest giant tortoise fossil discovered by scientists in northern South America.
The researchers compared the new Ecuadorian giant tortoise fossils with fossils from other South American and Caribbean giant tortoises, as well as with extant Galapagos tortoises. They use features such as shape, structure, size, and age of fossilized and modern turtle shells to create a picture of how these turtles and their potential ancestors are related. Created. Phylogenetic tree. They called these trees: Tip dateThat’s because they placed different types of turtles at the ends, or “tips,” of trees and assigned each species an estimated age, or “dated.”
They used a statistical method called . Bayesian analysis Evaluate the probability that each tree is correct based on known relationships between several species and new data from Ecuadorian fossils. The research team found that Galápagos tortoises are more closely related to Ecuadorian tortoise fossils than any other species included, based on the most likely tree shape, and that the two groups have a common Confirmed that they share a common ancestry.
The researchers interpreted the phylogenetic analysis as supporting previous researchers’ claims that a population of giant tortoises lived on the coast of Ecuador more than 2 million years ago. The researchers explained that this was around the same time and place that scientists believe Galapagos tortoises hitchhiked to the islands on the Humboldt Current, which flows north along the west coast of South America. Therefore, they suggested that their findings support the “previous” hypothesis proposed by some scientists.
Researchers concluded that Galapagos tortoises were gigantic before they left mainland South America. However, researchers cautioned that South America’s fossil record is incomplete and poorly preserved, and dating the evolution of Galapagos tortoises remains difficult. They will collect more giant tortoise fossils from South America, possibly incorporating ancient DNA, to help future scientists further examine when and where the Galapagos giant tortoise species originated. Recommended to describe and analyze.
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Source: sciworthy.com
