Month: March 2023

This blog will feature an especially interesting species of ancient fish, the coelacanth. These are among the most primitive fish, originating hundreds of millions of years before the dinosaurs.

Coelacanth are what is known as lobe-finned fish, which is a reference to their fins being attached to fleshy limbs each articulated using a single bone. It is almost like having an arm upon which the fins are then formed. This is most obvious in the tail and front/pectoral fins of the fish pictured above. That fat, wide structure that ends in a thin row of fins was a staple characteristic of ancient fish. It is believed that lobe-finned fish such as these eventually evolved into amphibians, reptiles, and eventually fully terrestrial quadrupeds. In essence, fish like this are the ancestor to all life on land.

Debatably the most incredible feature of the Coelacanth in particular is that it is still alive today.

Fossil evidence suggested that this animal had gone extinct 80 million years ago, until 1938 when a Museum Curator in South Africa found a dead Coelacanth in a pile of by-catch from local fishing boats. Following this first sighting, more specimens were seen in outdoor fish markets, and between 1938 and the early 2,000s several populations of coelacanth were identified in the West Indian Ocean, along the Eastern and Southern coasts of Africa as well as in Indonesia.

Coelacanths live in underwater caverns, between 100 and 500 meters deep,typically near areas of volcanic activity. Areas such as this attract many other fish, cephalopods, and other aquatic animals which the coelacanth feeds on. It is an extremely primitive fish, so it relies on a form of feeding called passive drifting. This boils down to the fish swimming aimlessly and eating whatever it happens upon. More complex hunting behaviors are not likely due to the extremely small brain of the Coelacanth, which occupies only 1.5% of its brain cavity, the rest of which is filled with fat. It seems as though its only instincts as far as hunting are to identify what in its environment is edible, through smell or sight, and then to consume it.

Two species of Coelacanth have been identified so far, the Comoros Coelacanth and the Sulawesi Coelacanth, each named for the islands near which they have been found. The total population of Coelacanths remaining in the world is unknown, though it is estimated to be in the ballpark of 10,000, though the Comoros Coelacanths found near Africa are significantly more vulnerable, with an estimated remaining population of 500 or less. However, Coelacanths are more or less safe from fishing by humans, as their scales and flesh produce large amounts of oil and urea which give them a poor flavor and can cause sickness. They are still accidentally caught in nets, though this is infrequent due to their cave-dwelling behavior, and they will never be intentionally hunted.

These ancient fish are representative of a once incredibly diverse clade that was the dominant form of fish on the planet at one point, and can be considered living fossils. This is one of few animals I can think of that provides us living proof as to what animals looked like hundreds of millions of years ago, and is certainly the oldest example of this.

Sources:

https://www.britannica.com/animal/coelacanth

https://australian.museum/learn/animals/fishes/coelacanth-latimeria-chalumnae-smith-1939/

https://animals.net/coelacanth/

In this blog I will be highlighting debatably the largest and most impressive of the ancient crocodilians, the Purussaurus.

Purussaurus is actually a giant species of Caiman, which are crocodilians in the same family as alligators. Many species of caiman still exist today, but none that resemble this massive animal. The normal length for this species was likely around 35 feet long, with some specimens being estimated to be over 40 feet long and 18,000 pounds, making Purussaurus twice the length and weight of the largest modern crocodiles.

The skull of this animal could be around 5 feet long on its own, and was also one of the most distinctive features of this animal when compared to similar species due to its shape.  The blocky, rounded skull and perfectly flat top of the head is not a feature seen in any modern crocodilians, though its vaguely similar to the rounded tips of alligator snouts.

This animal lived during the Miocene period, going extinct only 5 million years ago, in central South America, where most caiman still reside today. It was doubtlessly the top predator of its wetland ecosystem, preying on anything smaller than itself, including other crocodilians as well as the giant sloths which inhabited the same area. It had the strongest bite force of any four-legged animal so far known, able to produce over 15,000 pounds of force, which is about twice the bite force of a great white shark. It is also believed to be able to swim at the same speed as modern crocodiles, which is about 16 mph at full speed.

As is the case with any massive animal species, Purussaurus likely went extinct due to climate change. When the environment changes in a given ecosystem, smaller animals are able to move or adapt more easily if necessary, whereas larger animals such as this are immobile and much less adaptable to change as a result. This is probably why smaller crocodile species have survived since the age of the dinosaurs, while massive species such as Purussaurus are only around for relatively short periods of time. Larger animals also have much smaller population densities, so individual deaths have a much greater impact on the welfare of the entire species. This is why elephants are in such danger of extinction, because individual deaths can lead to an exponential decline in population.

One of the things I find most interesting about this species is that it was not especially unique, as there were many species in other time periods that closely rivaled its size. Crocodyliforms such as this have existed in an incredible range of variety throughout the history of the Earth, and modern alligators, caimans, gharials, and crocodiles represent a very narrow view of what once lived here. Purussaurus is merely the one I find most interesting, but there are have been many that walked on long legs like horses, ate only plants, or had whale-like mouths, and it is fascinating to me to think that if evolution had been slightly shifted in one way or the other, we could be coexisting with any one of them. It almost makes the crocodyliforms we know today seem boring by comparison.

Sources:

https://allthatsinteresting.com/purussaurus

Purussaurus

http://www.prehistoric-wildlife.com/species/p/purussaurus.html

For this blog I wanted to discuss an often overlooked variety of prehistoric animals, the whales. In my opinion, the most impressive animal of this group was Livyatan Melvillei, a toothed whale that rivaled sperm whales in size and appearance.

Livyatan lived between 5 and 10 million years ago during the Miocene era. Remains have only been found in Peru near the Southern Pacific, but like most whales, these animals likely had a much wider range.

As said earlier, these whales strongly resembles sperm whales given their toothed jaws and bulbous head, but unlike their more gentle relatives, Livyatan was an apex predator of its time. Sperm whales have a thin and weak lower jaw, and no teeth on the upper jaw, limiting their diets to soft-bodied animals like squid. In contrast, Livyatan had a wider, robust mouth with massive teeth on the upper and lower jaws. Its relative jaw muscle size was comparable to that of killer whales of today, and had the largest teeth of any carnivore in history, at about the size of a two liter soda bottle. Their teeth were also densely packed and curved outwards to provide extra grip on struggling prey. They likely used these capabilities to feed on baleen whales.

Given their predatory adaptations and their inherent intelligence as mammals, it is possible that Livyatan used hunting strategies similar to that of killer whales, such as tiring their prey out via direct pursuit and then drowning them once they were exhausted. With orcas, this is usually done in groups, but Livyatan’s size suggest it was possibly a solitary animal. It is also possible that they used their large melon (the big round part of their head) to ram prey, or struck from below to capture prey as great white sharks do. Livyatan also had a bulbous forehead, as mentioned and pictured before, which is a trait shared by sperm whales. Beluga whales look most similar to livyatan in this regard. This structure is made up of the melon and the spermaceti organs, which are used in echolocation, which was et another tool Livyatan had at its disposal while hunting.

Oftentimes, people draw comparisons between Livyatan and Megalodon (a giant shark) due to their similar size and predatory nature. There was a period of time in which both of these animals would have existed simultaneously, and it is therefore possible that they were in direct competition with one another. Megalodon would have possessed a stronger bite and was maybe 5 feet longer, but livyatan would have possessed superior speed and intelligence, so it is hard to say which of these animals would have been apex.

Overall, Livyatan Melvillei would have been an incredible animal to see alive, and comparing them with sperm whales, serve as an impressive example of how the food chain shifts over time.

Sources:

http://www.prehistoric-wildlife.com/species/l/livyatan.html

https://www.nyit.edu/medicine/livyatan_melvillei

https://carnivora.net/livyatan-melvillei-v-sperm-whale-t8891.html

https://www.nationalgeographic.com/science/article/behold-leviathan-the-sperm-whale-that-killed-other-whales