You’ve probably heard of several land animals that could swim. You’ve also read about several reptiles that could live on land and sea. But have you ever heard of a fish that could walk on land? The earth was once filled with different kinds of animals sporting unique characteristics. Paleontologists have tried to explain how aquatic animals transitioned from water to land for many years. They needed an animal that could help them bridge that gap. Luckily, they found the fossil of Tiktaalik.
Tiktaalik is a genus of extinct lobe-finned fishes. It is a transitional fossil. Tiktaalik shows that an intermediate existed between different types of vertebrates. It got the name ‘fishapod’ from Its unique mixture of tetrapod and fish characteristics. Read on to find out more about this unique ‘Fishapod.’
Tiktaalik: Scientific Name and Classification
The scientific name of Tiktaalik is Tiktaalik roseae. The genus name, Tiktaalik, means ‘freshwater fish’ in the Inuktitut language. The species name, roseae, is in honor of the person who sponsored the exhibition that led to the discovery of Tiktaalik.
Furthermore, you can classify Tiktaalik as a sarcopterygian. Sarcopterygians are a group of extinct lobe-finned fishes. Also, the species roseae is the only species classified under the genus Tiktaalik. The Tiktaalik is to tetrapods what the archaeopteryx is to birds.
Paleontologists classified Tiktaalik as a transitional fossil. The Tiktaalik had tetrapod characteristics such as ribs, appendages, skull, and neck. It also had fish-like characteristics like fin rays, scales, and gills. This mixture of characteristics made paleontologists deem Tiktaalik a transitional fossil.
Tiktaalik depicts an intermediate form between amphibians and fishes. It gives insight into the characteristics of the extinct close relatives of tetrapods. Unlike other fish-like transitional fossils, the fins of Tiktaalik had simple fingers. They also had basic wrist bones. This shows that the fins could bear weight. It also shows they were capable of supporting Tiktaalik’s weight on land.
Likewise, examination of the bones of the fore fins showed significant muscular facets. This suggests that the fin was muscular and could flex like a wrist joint. Also, these wrist-like traits would have helped the Tiktaalik anchor itself to the ground. This feature would have been helpful in fast-moving tides. Another notable body feature of the Tiktaalik is the spiracles on the top of the head.
Furthermore, the spiracles suggest that the Tiktaalik had primitive gills and lungs. These features would have been helpful in shallow waters where a higher water temperature results in low oxygen levels. Also, the presence of primitive gills and lungs would have led to the development of a more powerful ribcage. A robust ribcage is an evolutionary characteristic of land-living animals.
A more powerful ribcage would have helped the Tiktaalik support its body outside the aquatic habitat. Also, Tiktaalik lacked one body feature of most fishes. They lacked bony plates in the gill area. This helps to restrict lateral head movement. To this end, Tiktaalik is the first fish species ever to have a neck. Also, possessing a neck would have allowed the Tiktaalik to hunt freely in aquatic or terrestrial terrains. Scientists believe Tiktaalik could grow to a length of 2.7 meters.
Tiktaalik: Timeline and Habitat
Tiktaalik lived about 375 million years ago during the Late Devonian period. The Devonian Era is popularly known as the ‘Age of Fishes.’ It had this name because many fish species existed during the era. Lobefins, cartilaginous fish, ammonoids, and bony fish existed during the Devonian period.
Based on the modifications on its body, the Tiktaalik likely lived in mud flats. It could have also lived in shallow waters. Scientists believe it lived in marshy river habitats that rivaled today’s Amazon. Also, many of the Tiktaalik body characteristics support a shallow water habitat.
Tiktaalik: Diet and Behavior
Generally, Tiktaalik had characteristics of a lobe-finned fish. But it also had arm-like skeletal structures on its fore fins. These skeletal structures resembled those of a crocodile. While the fossil found in 2004 didn’t have a tail or rear fins, it had rows of razor-sharp teeth. These teeth indicate that the Tiktaalik was a predatory fish.
Similarly, Tiktaalik also had well-developed jaws they could use to catch prey. The exact diet of the Tiktaalik is unknown. But scientists believe it fed on terrestrial and aquatic animals. Also, fishes use the suction mode of feeding to catch prey. But this method cannot be effective on land. Research shows that Tiktaalik was capable of biting and suction feeding. It had a flat skull like the crocodile, which aided in snapping and biting prey.
Tiktaalik: Fossil Discovery
Tiktaalik was first discovered in 2004 in the Late Devonian floral frame formation on Ellesmere Island in Northern Canada. Ellesmere island had a warm climate and was on the earth’s equator when Tiktaalik lived. Scientists discovered the fossil sample of Tiktaalik when one of the specimen’s skulls was sticking out of a cliff. There were three fossil samples of Tiktaalik found on Ellesmere Island.
Similarly, the fossils consisted of several dozen incomplete specimens and a few nearly complete skeletons. After investigating the fossils, scientists discovered that the Tiktaalik resembled a cross between a crocodile and a fish. It had sharp teeth and a broad flat head.
Until recently, researchers had only examined the front portion of Tiktaalik fossils. When they found and studied the rear portions of the Tiktaalik, they found something unexpected. The rear part of the Tiktaalik had partial pelvic material and hips. Researchers found out that the solid pelvic bones of the Tiktaalik are characteristics of early tetrapods.
Furthermore, researchers thought that hips and hind limbs were characteristics of limbed animals. To this end, Tiktaalik shows that our close fish relatives had expanded hind limbs and hips. Still, the hip of the Tiktaalik remained fishlike. Also, the increased mobility and size of the fin, pelvic girdle, and hip joint would have made swimming and walking possible for the Tiktaalik.
There is not enough information on what caused the extinction of Tiktaalik. The end of the Late Devonian era is considered one of earth’s mass extinction events. Tiktaalik lived during the start of the Late Devonian period. Thus, it probably died out after the extinction event that ended the Devonian period.
Furthermore, most lobe-finned fish species died out during the Devonian period. The only lobe-fish species left alive today are the lungfish and coelacanths. Between the end of the Devonian period and the start of the Carboniferous period, ray-finned fishes replaced the lobe-finned fishes as the dominant fish on the food chain.
Also, tetrapods were absent for 15 million years at the start of the Carboniferous period. This time was called the ‘Romer’s Gap.’ The tetrapods that appeared after the ‘Romer’s Gap’ are considered the ancestors of today’s land vertebrates. Scientists are puzzled about what could have caused the Devonian mass extinction millions of years ago.
Additionally, some researchers propose that the appearance of substantial glacier formation at the end of the late Devonian period would have lowered sea levels and affected animals living in shallow waters. The proliferation of plants could have also created atmospheric changes that would be fatal to animal life. More research will need to be done to determine the exact cause of the Tiktaalik extinction.
Did Tiktaalik Have Any Natural Predator?
There is no information on the exact natural predator of the Tiktaalik. But the late Devonian period was home to cartilaginous fishes like the sharks and rays. Thus, any of these animals could have fed on the Tiktaalik. Adequate research is needed to back this theory.
Similar Lobe-finned Fishes During The Devonian Period
Tiktaalik wasn’t the only lobe-finned fish that existed during the Late Devonian Period. Here are some other lobe-finned fishes like the Tiktaalik.
Ichthyostega is a genus of extinct animals closely related to the tetrapods. It lived during the Late Devonian period, around 367-363 million years ago. Ichthyostega had limbs and lungs that guided it through shallow waters in the swamp. This early tetrapod genus had seven digits on each hind limb and was about 1.5 meters long. Ichthyostega was discovered in East Greenland.
Eusthenopteron is a genus of extinct lobe-finned fishes closely related to tetrapods. Early descriptions of this prehistoric fish show it emerging on land. Eusthenopteron lived during the Late Devonian period, around 385 million years ago. Also, it was first described in 1881 by J.T. Whiteaves. Eusthenopteron was found among a collection of fossil samples recovered from Miguasha, Quebec.
Till today, the discovery of Tiktaalik proves to be a fascinating find in understanding evolution. This prehistoric fish has bridged between aquatic vertebrates and terrestrial vertebrates. Tiktaalik is the missing link that scientists searched for to understand how aquatic animals evolved into terrestrial creatures.
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