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A living fossil is an extant taxon that phenotypically resembles related species known only from the fossil record. To be considered a living fossil, the fossil species must be old relative to the time of origin of the extant clade. Living fossils commonly are of species-poor lineages, but they need not be.
Previously considered to be the oldest known true crab, a 2010 revision concluded that Eocarcinus could not be accommodated among the Brachyura, and was instead transferred to the Anomura. [6] However, a 2020 reanalysis found that it was again the earliest known stem-group crab, but that it had not undergone the process of carcinisation. [2]
Currently, there are only four living species. Xiphosura contains one suborder, Xiphosurida, and several stem-genera. The group has hardly changed in appearance in hundreds of millions of years; the modern horseshoe crabs look almost identical to prehistoric genera and are considered to be living fossils. The most notable difference between ...
Predating dinosaurs, the horseshoe crab has roamed the earth for 445 million years, surviving five mass extinctions and three ice ages, but overfishing and habitat loss pose the greatest challenge ...
The tiny crab bridges an evolutionary gap that stumped scientists for years. Fossil stuck in 100 million-year-old amber is oldest "true crab" ever discovered Skip to main content
Reconstruction of Eocarcinus, the earliest known crab. The earliest unambiguous crab fossils date from the Early Jurassic, with the oldest being Eocarcinus from the early Pliensbachian of Britain, which likely represents a stem-group lineage, as it lacks several key morphological features that define modern crabs.
Scientists have identified the oldest living species on Earth is a deep sea organism that hasn't evolved in more than two billion years. And, it may prove Charles Darwin's Theory of Evolution.
Horseshoe crabs have changed little in appearance since they first evolved in the Triassic, earning them the title of "living fossil". Only four species of horseshoe crab are extant today. Most are marine, though the mangrove horseshoe crab is often found in brackish water. Additionally, certain extinct species transitioned to living in freshwater.