Within each ecosystem we find species that have a dominant role in its dynamics, since from the trophic point of view they have no predators and they head the pyramid. Thus, we have the sharks, who are undoubtedly survivors for having managed to escape the various mass extinctions that have occurred on the planet.
Throughout the evolutionary history of fish, various species became extinct, while some managed to continue on the path of life, either giving way to others or maintaining themselves over time, those that today we call living fossils. Here is an article from our site about prehistoric sharks, extinct and living examples Keep reading and learn more about these fascinating animals.
Characteristics of prehistoric sharks
Sharks (Selachimorpha) are a very ancient group of cartilaginous fish, which evolved around 400 million years ago. This indicates their presence even before the dinosaurs themselves. Shark fossils are more limited, than for other groups, due to:
- The time passed.
- The conditions of the marine environment that in many cases make it difficult to preserve remains.
- The characteristic cartilage body.
However, scientists have managed to estimate certain characteristics of prehistoric sharks, from teeth, fin spines, vertebrae or skulls that managed to be preserved and their peculiar scales. The oldest records of shark scales are around 420 million years old and correspond to what is now Siberia; As for the teeth, they come from about 400 million years ago in present-day Europe. There are also remains of a skull with an age of 380 million years, located in New South Wales in Australia.
Next, let's learn about some of the features:
- The teeth have been mineralogically stable, which allowed its maintenance throughout the geological history of the oceans. Also, like sharks today, these dental structures were replaceable.
- Some types of teeth of these prehistoric animals have been described as small, double-cuspedand did not have the sharp or serrated shape seen today.
- The scales were characterized by a tooth-like structure, which made it possible to verify that they indeed corresponded to sharks.
- It is estimated that these animals were less agile.
- Prehistoric sharks were much more diverse than today's, it is estimated that there were twice as many species. However, these have undergone major extinction events.
- Several of these ancient fish had rounded snouts, unlike the current ones that have elongated snouts.
- Brains were characterized by being smaller than the modern.
- As for the fins, they had less flexibility.
- Their bodies were also made up of a cartilage skeleton.
- They had, like now, various gill slits. Do not hesitate to consult this post with some Animals that breathe through the gills.
Extinct Prehistoric Sharks
As we mentioned before, these fish have gone through several episodes of extinction, which is why various types of prehistoric sharks became extinct. Let's get to know some of them:
Antarctilamna
This genus was described from a fossilized skull, which is considered the oldest found in freshwater bodies. Impressions of fin spines and teeth were also found. The discoveries have been in Australia, Saudi Arabia and other regions.
It has been described as about 40 cm, with the presence of strong spine in front of the fin dorsal and double-pointed teeth. The features are similar to prehistoric sharks of the xenacanthus group.
Xenacanthiformes
The term xenacanthus means strange spine Various genera of very primitive extinct sharks were grouped in this category. They were almost exclusive to freshwater environments, with the presence of a long backward-directed fin located at the back of the skull, two-pointed teeth, and the shape of the body was similar to eels
Elegestolepis
Corresponds to a genus of extinct prehistoric shark, considered one of the oldest. It lived more than 400 million years ago, in the Silurian and Devonian periods, and the remains of scales were found in present-day Russia in 1973. Due to the few known parts of its body, it is not known exactly what the body of this shark was like, although experts have a slight idea.
Aquilolamna milarcae
This is a single species of extinct shark within this genus, found in Mexico. The well-preserved fossil revealed that it was a peculiar individual, with a body torpedo-shaped, the tail similar to that of modern sharks, but the atypically long pectoral fins that looked like species of wings.
Orthacanthus
This genus includes various species of extinct sharks, with freshwater habits. It has been suggested that were carnivorous, with possible sexual dimorphism due to differences found in the tooth sizes. With dimensions of up to about 3 meters, they were located in present-day Europe and North America.
Don't hesitate to consult this other post about Sexual Dimorphism: definition, curiosities and examples, here.
Live prehistoric shark species
Sharks, having existed for so long, we could say that in general they are a very old group. However, today there are still species with traits that make them be considered as living prehistoric sharks, let's meet some of them:
Hexanchiformes
It is one of the oldest lineages currently in existence and they are known as Cowsharks, who fuse ancient and modern traits. They are grouped into 3 families and 5 species. Its main features are:
- They present 6 or 7 pairs of gill slits.
- They have an anal fin and a single dorsal fin.
- They are ovoviviparous and have exclusively marine habits, in waters temperate and tropical oceans of the Atlantic, Indian and Pacific oceans. We leave you this other post on our site with Ovoviviparous Animals: examples and curiosities to learn more about the subject.
- They live in very deep areas, almost inaccessible to humans.
- They have robust constitution, the largest species being Hexanchus griseus with about 4.8 meter s long, and the smallest Heptranchias perlo who reaches 1.4 meters.
Chlamydoselachiformes
Known as flying sharks, they are considered living fossils. The group has a single genus and two species, Chlamydoselachus anguineus and Chlamydoselachus africana. Among the main features we find:
- The body is eel-like.
- The snout is blunt in shape and the jaws are long.
- They have both a single anal and dorsal fin.
- They are ovoviviparous and of exclusively marine habits, in waters depths of the Atlantic, Indian and Pacific oceans.
- The largest is the species C. anguineus, which reaches up to about 2 meters long.
What was the largest prehistoric shark?
Sharks undoubtedly store a series of fascinating and curious data, and one of these aspects is related to size. If you've been wondering if Giant prehistoric sharks existed, the answer is yes. Fossil evidence has established that there was a prehistoric shark of enormous proportions which is commonly known as megalodon (Carcharocles megalodon).
This mega predator had a dimension around 16 meters and extinct about 2 years ago, 5 to 3 million years old The discovery of teeth, remains of jaws and vertebrae in countries such as the United States, Panama, Cuba, the Canary Islands, Africa, India, Australia and Japan, among others, confirm that, if it existed, it was also a species with a wide range of distribution.
Why did the megalodon become extinct? Discover the answer to this question in the following post that we suggest.
