Cheirolepis+Lovers

CHEIROLEPIS. = = Cyprinus Carpio (Modern Animal) >>
 * Cheryl Au**

Cheirolepis (pronounced CARE-oh-LEP-iss) is an extinct species from //paleoniscoids//, a group of primitive ray-finned fishes. An early form of //actinopterygii// (ray-finned fishes), they are one of the main prehistoric fishes in which many other species of fish including the Carp, have evolved from. Living through the middle to late Devonian period (approx. 408 to 360 million years ago) until the mass extinction where it wiped out approximately 50% of all animal species present at the time and a large portion of coral, which could have been the early form of the __blue coral__. Nonetheless the Cheirolepis managed to survive and evolve into the many species of fish we now are acquainted with.

Also during this period, these actinopterygii stared to evolve into the early forms of tetrapods which would later become vertebrates. These included all the mammals such as lions and Siberian tigers as well as reptiles such as the __frilled neck lizard__.

A primitive of the ray-finned fish species, the Cheirolepis lived in mainly in lakes of the Northern Hemisphere during the Devonian period, now known today as Europe and North America.

This report provides a general idea on the Cheirolepis, their features and habitat as well as giving an explanation on how the Cheirolepis that existed more than 300 million years ago came to be the ancestor of the many fish species today.

Habitat.
Fossils of the Cheirolepis showed evidence that they inhibited largely in lakes of the northern hemisphere during the Devonian period which today, is North America and Europe (Fig. 01). Similar to their descendant, the Carp, the Cheirolepis is a freshwater fish and since the Devonian period was somewhat a warm period, temperatures of the freshwater lakes would’ve been around 15 - 30 degrees. //Source:// //http://www.globalchange.umich.edu/globalchange1/current/lectures/Perry_Samson_lectures/global_warming_potential/DEVONIAN.jpg// ||
 * [[image:gdfdf.png width="618" height="296"]] ||
 * Red represents area where the Cheirolepis were found. ||
 * > **Fig.01: Cheirolepis in the Devonian Period**

The Cheirolepis mostly survived on other smaller species of fish that usually occupied the shallower waters of a freshwater lake. However the Cheirolepis was known to have preyed on fishes that were almost two thirds of its own size. The Cheirolepis would have most likely to be a middle dwelling fish as this was where most of the fish species at the time were found.

The Cheirolepis unlike the Common Carp did not rely on dense vegetation for protection or cover as they were one of the main freshwater predators of the Devonian period. However the Cheirolepis does tend to spawn in areas where they are able to hide their young such as in gaps between rocks, so the Cheirolepis can usually be found in large lakes with vegetation around the fringes of the lake (Fig.02).

//Source:// //http://www.arcadiastreet.com/cgvistas/earth/02_paleozoic/images/asteroxylon_swamp_600.jpg// ||
 * [[image:dfhd.png width="880" height="414"]] ||
 * > **Fig. 02: Cheirolepis Habitat**

1. Streamline Body
A feature of the Cheirolepis that is very much similar to those fish species found in modern days especially their close descendant, the carp, is their streamline-shaped body. Strong and muscular with highly developed fins allows the Cheirolepis to sustain swimming for long periods of time. It also allows the Cheirolepis to swim speedily and swiftly whilst remain stability in water.

Although the Cheirolepis and the Carp might have shared a common body structure, the purpose of this body shape was completely different. Streamline-shaped bodies allowed the Cheirolepis to swim faster and more stable in order for them to catch their prey more effortlessly and efficiently. The preys of the Cheirolepis could have also been strong swimmers and in order to catch these preys, the Cheirolepis would have had to develop features in which it would allow them to catch their prey, this meant that the Cheirolepis were able to catch more prey and have a better chance of survival whilst they were alive.

**2. Eyes** From the size of the Cheirolepis’s eyes, it is most likely that the Cheirolepis mainly relied on catching their prey by hunting with sight. Their eyes were large and placed well towards the frontal portion of the skull which made it easier for the Cheirolepis to spot their prey and it suggests that not only did the Cheirolepis hunt primarily during the day time, where large amounts of sunlight are available but also that the Cheirolepis had a good range of sight, possibly good peripheral vision as well.

Having the feature of large eyes that are placed forwards in the skull gives the Cheirolepis a better chance of survival as they rely on sight to hunt and with bigger eyes, allows them to see their preys more easily and therefore be able to hunt them down for food in order to survive.

//Source: http://pds.exblog.jp/pds/1/201101/03/64/e0133764_20323549.jpg// ||
 * [[image:http://pds.exblog.jp/pds/1/201101/03/64/e0133764_20323549.jpg width="558" height="375"]] ||
 * > **Big eyes and small sharp teeth**

**3. Sharp teeth** Another feature of the Cheirolepis is that in both the upper and lower jaws, they are actually lined with small, razor-sharp teeth. Having sharp teeth gives evidence that the Cheirolepis was once an active predator that hunted extensively. With these razor-sharp teeth, it enabled the Cheirolepis to consume prey that was possibly more that two thirds of its own size with assistance from their jaw that is able open up very wide.

These razor-sharp teeth means that the Cheirolepis can basically prey on fishes of any sizes, even those that might be larger that the Cheirolepis itself. With these teeth, the Cheirolepis would’ve been able to catch their prey more easily, as they had a wide selection of fish to choose from. For this reason, they were more likely to have survived than many other species of fish at the time.

**4. Well-developed Fins** Fossils of the Cheirolepis showing their well-developed fins also implied that the Cheirolepis was most likely to have been an active predator. The well-developed fins gave the Cheirolepis speed as well as stability, it also allowed the Cheirolepis to glide smoothly under water along with entitling the Cheirolepis to move forwards and backwards in all directions with ease and flexibility. They also have a single dorsal fin, which mainly assists the Cheirolepis in preventing them from rolling over and sudden stops.

Well-developed fins also assists the <span style="background-color: transparent; color: #000000; font-family: Arial; font-size: 13pt; text-decoration: none; vertical-align: baseline;">Cheirolepis during hunting fins allowed the Cheirolepis to swim faster as well as being more stabilized. With these fins, they are less likely to ‘roll-over’ when they are swimming and help the Cheirolepis survive by balancing their weight so that they can catch their prey.

<span style="background-color: transparent; color: #000000; font-family: Arial; font-size: 13pt; text-decoration: none; vertical-align: baseline;">**5. Caudal Fin** <span style="background-color: transparent; color: #000000; font-family: Arial; font-size: 13pt; text-decoration: none; vertical-align: baseline;">The caudal fin of the Cheirolepis is a basic feature of all fish species, even those found today. Known basically as the tail fin, the one and only function of the caudal fin is to propel the Cheirolepis into motion once in water. The caudal fin of the Cheirolepis is heterocercal meaning that the top of the fin is longer than the bottom half and therefore asymmetrical. Many fishes nowadays still have heterocercal fins, one of them being the <span style="background-color: transparent; color: #000000; font-family: Arial; font-size: 13pt; vertical-align: baseline;">__shark__ <span style="background-color: transparent; color: #000000; font-family: Arial; font-size: 13pt; text-decoration: none; vertical-align: baseline;">. //source:// http://images.yourdictionary.com/images/3768.16.heterocercal.jpg ||
 * [[image:http://images.yourdictionary.com/images/3768.16.heterocercal.jpg width="464" height="218"]] ||
 * > **Heterocercal Tail**

<span style="background-color: transparent; color: #000000; font-family: Arial; font-size: 13pt; text-decoration: none; vertical-align: baseline;">With their caudal fin, the Cheirolepis could swim faster and propel itself forwards.As they a strong and active predator, the caudal fin would’ve helped the Cheirolepis to hunt the out-swim their prey. Using their caudal fin, the Cheirolepis would have had abundant amounts of prey, hence the Cheirolepis would’ve have higher chances of survival.

<span style="font-family: Verdana,Geneva,sans-serif; font-size: 210%;">ENVIRONMENTAL Pressure.
== Environmental pressures that could have give rise to these adaptations are the cause of the evolution of the Cheirolepis. The Cheirolepis has adapted to have well-developed fins, long caudal tail, sharp teeth, streamline body and large eyes are all because of making their hunting of prey a more easier task for the Cheirolepis. Their eyes help the Cheirolepis to track down their prey before using their highly developed fins, tails to propel themselves forward to lunge onto the prey. The shape of the streamline body means that the water will not hinder them and their sharp teeth allows for the Cheirolepis to rip apart of their prey and digest it. All of these features have not only evolved but they have evolved so that they can work together to better accomplish the task of hunting for food. ==

<span style="font-family: Verdana,Geneva,sans-serif; font-size: 210%;">SELECTION Pressure.
== <span style="background-color: #ffffff; color: #000000; font-family: Arial; font-size: 12pt; text-decoration: none; vertical-align: baseline;">The disappearance of the <span style="background-color: transparent; color: #000000; font-family: Arial; font-size: 13pt; text-decoration: none; vertical-align: baseline;">Cheirolepis is closely linked with the period know as the Late Devonian extinction which wiped out a large majority of marine life. One of the five major extinction events in the history of the Earth, it is unclear what caused the extinction of many of the aquatic species, but some believe that oceanic volcanoes erupted and affected a large portion of the marine life. With portions of the marine life destroyed, there would’ve been insufficient food left for the other species and because of the decrease in food, the Cheirolepis chance of survival declined. However at this time, the Cheirolepis had already begun evolving and had spawn off other species of fish that we, today recognize. ==

<span style="font-family: Verdana,Geneva,sans-serif; font-size: 130%;">Bibliography.

 * Cheirolepis. (n.d.). //Imperial Hub//. Retrieved June 19, 2011, from http://205072.xobor.com/g16p99-Cheirolepis.html
 * Cheirolepis. (n.d.). //Universalium//. Retrieved June 24, 2011, from http://universalium.academic.ru/262572/Cheirolepis
 * Cheirolepis. (n.d.). //UCMP - University of California Museum of Paleontology//. Retrieved June 23, 2011, from http://www.ucmp.berkeley.edu/vertebrates/actinopterygii/cheirolepis.html
 * Cheirolepis (fossil fish) -- Britannica Online Encyclopedia. (n.d.). //Encyclopedia - Britannica Online Encyclopedia//. Retrieved June 26, 2011, from http://www.britannica.com/EBchecked/topic/108366/Cheirolepis
 * Cheirolepis - Encyclopedia. (n.d.). //Online English Encyclopedia UK (encyclo.co.uk)//. Retrieved June 19, 2011, from http://www.encyclo.co.uk/define/Cheirolepis
 * Cheirolepis : Ancient Actinopterygii : Prehistoric Fish. (n.d.). //Animal Planet : Pets, Wild Animals, Dog Breeds, Cat Breeds//. Retrieved June 26, 2011, from http://animal.discovery.com/prehistoric/cheirolepis/
 * Strauss, . (n.d.). Cheirolepis - Prehistoric Fish Cheirolepis Characteristics, Behavior and Habitat. //Dinosaurs - Types, Behavior and Evolution of Dinosaurs//. Retrieved June 20, 2011, from http://dinosaurs.about.com/od/tet