07/12/13 at 1:41 am
We like to think of evolution as constantly changing, altering and keeping up with a world of changing environments. We think of animals migrating and then adapting to a new environment, their old genetic structure no longer suitable and new features making its way into the makeup of a species. But that is not always the case. Some species have become so adapted to their environment that they have seen little (if any) change over the course of millions of years. Here is a list of ten common creatures in the world today that have barely changed since the time of the dinosaurs.
Believed to be extinct for over 65 million years and a lineage traced to way before the dinosaurs, scientists were shocked when a specimen was found just off the coast of South Africa in 1938. It has barely changed in over 400 million years and is closely related to the various species of lung fish, which means it is actually a closer relation of all mammals than it is to most species of fish. There are two distinct species now discovered, the Indonesian and the West Indian Ocean variety.
2. Goblin Shark
This bizarre looking shark is an ancestor species of most common form of shark and therefore looks “primitive” in comparison. It is not very well understood, a shy deep-sea creature that can trace its lineage back 118 million years. Interactions with humans are rare and they tend not to survive very long in captivity. Japanese fisheries catch approximately thirty specimens per year, but purely by accident as there is little to no economic value to the species. It is referred to as a living fossil for being the only member of the Mitsukurinidae family.
This bizarre species of large, venomous rodent very closely resembles extant remains that exist close to the end of the age of dinosaurs. They exist purely in the Caribbean – on Cuba and Haiti and the Cuban variety is slightly smaller than its Haitian counterpart. They are fairly diverse creatures, able to live in a wide range of habitats. They look like giant shrews and are often compared to those species. Before the arrival of European settlers they were the primary hunters and therefore had no prey. They are now a threatened species and subject to conservation laws.
One of the most surprising entries on the list, this large and easily identifiable seabird has been discovered in fossils some 30 million years old, with the oldest fossil itself found in southern France. Very few examples have been found in North America, with most examples found across Europe. They are distinct with their long beaks and large throat pouch and are often seen migrating across oceans. Famously, a flock of pelicans was seen in the closing scene of the dinosaur film Jurassic Park.
This small reptile native to New Zealand has been traced in the fossil record back to 220 million years ago; it is the only remaining example within its lineage. Until recently, they were believed to be almost incapable of breeding in the wild and most of the conservation work existed in hatcheries. That was until 2008 when a large nest was discovered during building work. When discovered in the 19th century, they were misclassified as lizards but having bird and crocodile features that was soon corrected.
The only living creature known to have a skull but not a vertebrate column, this eel-like fish has a fossil record going back almost 300 million years – samples are remarkably similar in morphology. It is a matter of some debate whether it is more closely related to lampreys or lancelet. For classification they are all grouped together but experts feel that one may precede the other. They are also known as “slimefish” for the copious amounts of milky slime that they produce to escape from the jaws of prey when trapped.
Similar to the hagfish in that it is rather eel-like, it doesn’t have a skull like those creatures it resembles – nor does it have a jaw – but it does have a large sucker for a mouth by which it attaches itself to other creatures in order to suck the blood from its victims. Its lineage has been traced back some 360 million years which is quite an achievement seeing as it is made entirely from cartilage which does not survive as well as bone. It is a matter of several studies – mostly for the examination of autoimmune systems. It is thought to share common traits with a lot of other early fish.
8. Horseshoe Crab
This rather primordial looking arthropod lives, like most crabs, around shallow marine areas. Due to that hard shells survive very well, we have found fossils of the species going back some 445 million years and the morphology has barely changed in that time. It resembles most crustaceans but exists in a category all on its own. They are more closely related to arachnids (spiders, scorpions and fleas) than to other crabs. Its entire body is protected by its shell.
This peculiar looking sea mollusc has a lineage dating back some 500 million years – way before the dinosaurs. Like most other cephalopods such as the octopus and the squid, it has tentacles. It also has a hard shell that covers most of its body and in that respect it resembles the most identifiable sea-front fossil – the ammonite which it probably resembled in life too (however these were probably more closely related to the other cephalopods).
These beautiful and sometimes dangerous free-floating creatures of the deep have been found in deposits dating back some 505 million years; it is estimated that they go back much further than this with projections going up to 700 million. If this is true then they will be the world’s oldest multi-organ creature. They are common in most coastal regions and though all are venomous, not all of them are harmful to humans.
Some of the creatures above were believed to be extinct until their discovery revealed otherwise. Our understanding of evolution does not just come from the study of extinct ancestor species, but also through examining those creatures that have barely changed – what hasn’t changed can teach us as much as the study of what has changed. All of these species survived the extinction of the dinosaurs and are still around today. How many more species do we believe to be extinct are still alive and waiting to be discovered?