Panchronic Organisms, Those That Refuse To Disappear

Panchronic organisms, also known as living fossils, are those species of animals that, since their origin, have lived virtually unchanged for millions of years.

Panchronic organisms or living fossils are species very similar to what they were in their origin, something that makes them extraordinary and surprising organisms, since they are extremely similar to older animals.

They are surprising not only because of their strange appearance, but also because they continue to live today as they did in ancient times.

What are panchronic organisms?

Species, from their appearance to their extinction, go through three stages. The first is the evolution of a species from an ancestor. Then there is the continuous growth of the individuals in the group, until their maximum distribution and abundance. The last step is to reduce the number of individuals in the group, thus culminating in their extinction.

On the other hand, species have different evolutionary trends. They are:

1. Rapid transformations due to species competition or survival processes.
2. Slow transformations over time, almost imperceptible.
3. Remain unchanged for millions of years.

In this last group are the panchronic organisms ( pan: all, chronos: time), although they are also popularly referred to as living fossils.

The designation of living fossils can be misinterpreted or considered wrong because a fossil is something dead (at least 10,000 years old) and therefore no living plant or animal could be classified as a fossil.

Thus, a panchronic organism, be it an animal or a plant, is one that has remained unchanged throughout the period in which it prospered and beyond.

Panchronic organisms are generally seen abundantly in the geological past, as they were very well adapted and fully distributed.

Compared to the number of species currently alive, there are few organisms considered panchronic.

the coelacanths

Coelacanths ( Latimeria chalumnae ) were among the vertebrate species believed to be extinct from the Cretaceous period until 1938.

It was at this time that a live specimen was found at the mouth of the Chalumna River in southern Africa. It was 1.5 meters long and weighed about 50 kg.

A second coelacanth was found in 1952 on the shores of the island of Comoro, in the Indian Ocean, between Mozambique and Madagascar.

In 1987, the first underwater images of the coelacanth in its natural habitat were captured. At that time, around 170 coelacanths were photographed, all close to the Comoros archipelago and in the Celebes.

Coelacanths are fleshy fin fish of the order Coelacanthiformes, relatives of terrestrial vertebrates. They appeared in the Devonian period (400 million years), although traces have been classified in the Carboniferous period (350 million years).

Their scarcity currently indicates that they may be on the brink of extinction. Or maybe they might have found a hidden, cold, dark, and deep place to live peacefully on our planet.

the horseshoe crab

The crab, an arthropod known as the horseshoe crab ( Limulus polyphemus ), is another living fossil. This species of the Merostomata class of the order Xiphosura is related to arachnids.

Its oldest specimens were located in rocks 500 million years old from the Ordovician period. Its proximity to missing forms and the fact that it is the only survivor of its kind make it a panchronic organism.

Horseshoe crab is usually found in the Gulf of Mexico, along the coast of the North Atlantic. It can reach 50 centimeters and feeds on molluscs, larvae and other invertebrates. It spends much of its life buried in the sand, where it captures its prey.

the tuataras

The tuataras (Sphenodon) are another excellent example of a panchronic being. They are part of the endemic reptiles of islands near New Zealand, of the family Sphenodontidae and of the order Rhynchocephalia .

The meaning of its popular name comes from Maori and means thorny back.

The tuatara have undergone very few physical changes over the past 150 million years. These reptiles appeared in the Triassic period and coexisted with the dinosaurs.

Their populations began to decline after the Triassic, and their evolutionary line continued to a limited extent. In the age of mammals, tuatara disappeared from Earth, remaining only in New Zealand, the country in which mammals never arrived.

The tuatara has no living relatives. Its only relatives are fossils, except for the two living species of tuatara found in New Zealand.