1. The living fossils: coelacanth
Celeste Thomas
Department of biodiversity and conservation biology
University of the western cape
Private bag x17
Bellville 7535

2. Classification The coelacanth classification are as follows.
Kingdom: animalia
Phylum : chordate
Class : sarcoterygii
Order : coelacathiformes
Family : latimeriidae
Genus : latimeria
en.wikipedia.org/wiki/coelacanth

3. Origin of the coelacanth
The living vertebrates consists mainly of two groups in the modern classification.
The Gnasthostomata and the jawless Agnatha are divided into two groups cartilaginous chondrithyes and bony Osteichthyes.
The actinopterygii and sarcpoterygii are the two main groups of the bony vertebrates.
The latter comprises of three groups the coelacanth, lungfishes and the four-limbed tetrapods.
The sarcopterygii is applied to a group comprising the coelacanth and the lungfishes.
The jawless agnatha, are represented by hagfish and lampreys and jawed gnathostomata are the living vertebrates (Pough et al. 1989). The ray-finned fishes being the bony vertebrates are the actinoptergyii and the lobed-limbed sarcoptergyii. The groups comprised by the latter are the lungfishes and the four –limbed vertebrates the tetrapods. The sarcoptergyii comprises the coelacanth and the lungfishes. However these groups had diverged within a short time interval and at this level of analyses, their relationship appeared to be irresolvable trichonmy.

4. Thus few scientist believe that the coelacanth is the missing link.
A modern scientist J L B Smith thus believed that four-legged land dwellers evolved from the extinct groups like the coelacanth.
However, although the coelacanth share characteristics with early land dwellers the lungfishes shared more.
Thus few scientist believe that the coelacanth is the missing link.
The research that has been done showed that the coelacanth latimeria chalumnae has not radically evolved from the way coelacanths appeared millions of years ago.
Thus by studying latimeria chlumnae is studying an ancient fossil that is alive.
JLB Smith is a modern scientist that believed that tetrapods evolved from the extinct coelacanth, rhipidistians or the lungfish (Walker, 2002). Many characteristics are shared by the coelacanth and the land dwellers but even more are shared by the lungfish and the tetrapods. Therefore there are few scientist that believe that the coelacanth is the missing link. A common ancestor shared by groups or these lobed fined fishes has not yet been found. Thus tests conducted in 1991 showed that coelacanths seem more closely related to ancient frogs than to lung fishes. However by studying modern coelacanth specimens palaeontologists confirmed many theories based on ancient fossils.

5. The choanichthyes is made up by crosspterygii and dipnoi.
The Crossopterygii and Dipnoi were the only vertebrates orders between Devonian period and recent times.
The choanichthyes is made up by crosspterygii and dipnoi.
The rhipidistia and coelacanthini are two suborders included in crossopterygii.
The rhipistians however, became extinct in early Permian.
Even though the rhipidistians became extinct in the early Permian, they were important because they gave rise to the tetrapods as well as to the coelacanths.
The lungfishes were derived from the primitive rhisidistians or from their common ancestral group.
In the middle Devonian were the coelacanth already well defined.
The only vertebrates that is known to span the long time interval between the Devonian and recent times are the crossopterygii and dipnoi. The subclass choanichthyes is made up of crossoptergii and dipnoi and set apart from other major groups of bony fishes, the actinopterygii because they have a presence of internal nostrils and features of skeleton. The subclasses in crossoptergii are rhipidistia and coelacanthini which persisted to present time. Although the rhipidistia became extinct , they were important because they gave rise to the tetra pods aswell as the coelacanth. The coelacanth was already well defined by middle Devonian, thus the time of its first known appearance in fossil record.

6. Fossil records
Thus the coelacanths studied by scientist since 1839 were only through their fossils.
The fossil fish Coelacanthus granulatus were found by Louis Agassiz.
Over the next century scientists had found fossils of dozens of species of coelacanth.
400 million years ago was the appearance of the earliest fossils, while the most recent were 70 million years ago.
Thus according to the fossils record coelacanths disappeared completely.
Coelacanths had been studied by scientists since 1839, but only through their fossil records. A Swiss naturalist Louis Agassiz described a fossil fish found in England and named it Coelacanthus granulatus. The meaning coelacanthus came from two Greek words meaning hollow and spine and referring to the fishes hollow fin spines. Thus scientists had found fossils of a dozen species of the coelacanth over the last century. These fishes ranged in length from 5inches to 20inches. About 400 million years ago had the first species appeared. Thus according to fossil record , coelacanth then disappeared completely (Walker, 2002).

7. Macropoma a extinct genus of crustaceous resembled the living specie.
Although only two representatives present, as a group the coelacanths were once successful.
These species left abundant fossil record from Devonian to the cretaceous period.
The coelacanth have been known to remain unchanged for millions of years.
Macropoma a extinct genus of crustaceous resembled the living specie.
Although only two represented by the living species, the coelacanth as a group were once very successful with several genera. From the Devonian to the end of the cretaceous period had species left abundant fossil record at a point they suffered nearly complete extinction and past the point no fossils are known. It is thus believed coelacanth had remained unchanged for million of years but in fact the living species and genus are unknown from fossil record. Macropoma is an extinct species genus which are particularly those of last known fossil records closely resembles the living fossils.

8. The discovery
Marjorie courtenary-latimer were first person that discovered the specimen in 1938 in coastal waters of South African.
The coelacanth were not particularly successful in total numbers of distinct genera even in spit of their long history.
The specimen was discovered by Marjorie courtenary-latimer, she was the curator of a museum in East London, South Africa. While she was busy inspecting lobed fishes she caught the unusual marine in she caught the fish near the chalumnae river were she was looking for a fishing boat that had been fishing for sharks. She took the fish to the museum where it was named by the modern scientist JLB smith, latimeria chulmnae. The coelacanths in spite of their long history were not particular successful in terms of total numbers of described genera or in terms of adaptative radiation.
#Biological_characteristcs

9. The diversity of these fishes reached a peak in Triassic, only with 11 genera of this period.
The Devonian coelacanth has been found in marine formations suggesting marine origin.
Thus negative evidence were available that showed coelacanth deserted marine environment by missippian.
Thus on the basis of evidence, their peak of their diversification was reached in the Triassic, but which only had 11 genera for the period reported and morphological specialization exceptions which was rather a minor significance. The Devonian coelacanths had been found in marine formations thus suggesting the fish originated from a marine origin or a an early marine radiation. Thus negative evidence supposed that coelacanth as a group deserted the marine environment by the missisipian.

10. The lungfishes were equally well defined group.
The carboniferous and Permian coelacanths occurred in freshwater sediments and Triassic genera were about 60% marine.
The lungfishes were equally well defined group.
They arose in early Devonian having same total number of genera like coelacanthini.(
In fresh water sediments had the known carboniferous and Permian coelacanth occur, while the Triassic genera were 60 percent marine. The genus latimeria which is a mesozoic are a marine. The lung fishes is the group that a is also well defined, with representatives occurring in marine rocks of the early Devonian age. With a genus that retains a high percentage of primitive rhisipidistian characters. However even though total number of genera is about the same as in the coelacanthini the greatest number recorded from the Devonian, suggest that the maximum radiation occurred early in the history of the group.

11. The Anatomy
Major unique features are present that distinguishes among the coelacanth and other fishes.
This involves aspects like external forms, skeleton anatomy etc.
The feature in the coelacanth in particular being the extra tail the epicaudal.
The fins of coelacanth are also different instead of 1 dorsal fins they have 2.
Dentricales are present which aids in protection.
There are major features present in the coelacanth that can distinguishes it from the other fishes. This in particular having the extra tail found on the caudal fin. This tail that protrudes from the caudal is called a epicaudal fin. Thus no other modern fishes are known to have this fin. This tail is quit unique in that the coelacanths can beat and bend the epicaudal fin to maneuver into a headstand and to steer around obstacles. Thus in all modern fishes are there smooth scales but only in the coelacanth are the smooth scale on the lower half. Thus toothlike spines called denticles protects the lower half of each scale . When the denticles cover the upper half of each scale it it makes the scale rough like sandpaper (Walker, 2002).

12. The skeleton of the coelacanth was also different from modern fishes.
The skeleton were made mostly of cartilage.
A notochord, which are fibrous, elasticity are usually thick walled in coelacanth.
Thus most creatures with backbones, have vertebrae which replaces their notochord.
The notochord in the coelacanth are thick-walled a tube filled with oil which serves as a kind of a backbone. Thus in most creatures, the vertebrae replaces the notochord in the embryonic stage of development. Thus the coelacanth has no vertebrae and the notochord therefore provides its longitudinal backbone support. Most vertebrates thus has both products of the embryonic mesoderm, but some species has permanently ossified skeletons not because they are degenerated but for sound adaptive reasons. Thus cartilage and bone can be easily differentiated from one another. The cartilage is a group of cells surrounded by an amorphous ground substances, made by cells. Bone however are stronger because the extracellular material is calcified (Rogers, 1986).

13. The head region of the coelacanth is also a mystery.
It is occupied by 6 small holes , two near each eye and two towards the tip of the snout.
This identification was never observed in coelacanth fossils.
These strange holes led to a space in the coelacanths head in which this cavity had never been seen in a living fish.
The six holes were an outer opening of a tube filled with jelly-like substances.
The rostral organ are formed together by the tube and cavity .
Thus this organ has unique functions which are not observed in modern fishes.
The observation made on the coelacanths head was 6 small holes, it was thus found that these 6 holes was the outer opening of a tube filled with a jellylike substance, leading into a jelly-filled head cavity. In which tube and cavity formed the rostral organ. It is known that many fishes gives off electrical pulse as their muscles move and as chemicals inside the body react with one other. Thus modern fishes had other means of sensing the pulses, by using this ability allow them to track food. In the coelacanths the electrical pulses may travel through the jelly-tube. Into the cavity, where the nerves sense them (Walker, 2002).

14. The presence of color rods assist the coelacanth in vision.
The eye features of the coelacanth is normally large which is attached to the optic nerves.
The presence of color rods assist the coelacanth in vision.
The brain is quit small and occupies about 1.5 percent of the braincase in mature individuals it differs in the pups.
The gills of the coelacanth normally indicates that they found in depth of m. (
The large eyes of the coelacanth are attached to the thick optic nerves. Few cones are present in each which register color, but many rods which detect light. The coelacanth is virtually color-blinded that can see extremely well in dimlight of great depths where it lives. The tapetum lucidum which is a layer behind the retina gives the coelacanth the ability to see in near darkness. However this layer acts as a mirror intensifying weak light.

15. Locomotion
The coelacanth has unique ways of swimming and gliding through the water.
Their lobed pectoral and pelvic fin move similar to the way a son moves his arms.
In spite of thickness of fins they quit flexible.
When swimming pairs lobed fins move the way horses legs do when trots.
A intentional fin locomotion is thus unique to the coelacanth.
The coelacanths indeed has a locomotion which is different from modern fishes. The pairs of lobed fins moves the way a horse legs do when it trots, when coelacanth swims the left pectoral fin moves up at same time as the right pelvic fin moves up, then the fin reverses direction. This thus resembles a crawling child when its left arm moves forward as right knee does and the lizards walk in same manner (Walker, 2002).

16. The coelacanth rests close to the bottom of the ocean bed.
Its fins are used for many functions like balance and steering as it swims.
To escape its prey the fish uses its large thick, caudal fin.
The coelacanth thus has limited energy, it only swims fast enough to escape its predator.
Thus observation has been made that coelacanth live at depth of between 117 and 198m. Its paired lobed fins might brush or briefly rest on the bottom at times. thus the coelacanth never walk or stalk prey on fins, instead it uses its fins to balance itself, to steer as it swims and brake when it needs to stop moving. Thus occasionally when predators come along than coelacanth lifts its thick caudal fins which allows the coelacanth to propel like a rocket. Their energy level is limited, they only swim fast to escape danger than settle down.

17. Hunting
The coelacanth are usually opportunistic feeders, hunting on cuttlefish,
squids etc
They are known to be nocturnal with unique feeding habits.
Instead of hunting in packs they usually hunt alone.
They usually allowed themselves to be steered by the water currents.
This type of hunting displayed by the coelacanth is called drift hunting.
The coelacanth are usually opportunistic feeders, hunting on squids and cuttlefish. fishes are nocturnal and usually hunts alone. They do this by drifting on the ocean currents drift on the water currents. As the coelacanth drifts it uses its fin to steer. However the coelacanth saves energy by letting the water currents move its body instead of swimming simultaneously, the coelacanth saves energy in order to catch its prey. (Walker 2002).

18. Its natural habitat
The coelacanth in its natural habitat are distinguish from one another by having white marks present on their body.
They usually assist in camouflaging the fish.
During late hours of the night are these fishes usually active, performing all sorts tricks.
Coelacanth in their natural habitat are distinguished from one another by the white marks that dotted their bodies. These marks usually help the fish blend in with surrounding rocks, which are speckled with light-colored sponges oysters. These patterns of white markings are thus distinct found on each coelacanth. These species are mostly active during the night. Thus the pilot Jurgen Schauer observed headstands made by these fishes, and how they gracefully moves through the water in the late nights (Walker 2002)

19. Conclusion
The coelacanth are indeed declared as an endangered species.
Many programmes are available, like the CITES for eg that decides what needs to be done with a captured coelacanth.
Thus it can be concluded looking at the conservation status the coelacanth is indeed a endangered species. The organisation Convention on International Trade had declared the coelacanth in 1989 endangered. This organisation thus controls the trade of threatened and endangered species. The legal trade ended when Comoro islands signed the agreement in thus when a coelacanth is accidentally caught it can only be send to a scientist or museum and only if CITES grants permits.( Walker 2002).

20. References
Blaxter, J.H.S, Marshall N.B, Bone Q Biology of fishes. Chapman and Hall, New York. pp323. ISBN
Rogers, B 1986 Looking at vertebrates. Longman,USA.PP189. ISBN
Pough,FH, Heiser J.B, and Mcfarland W.N 1989 Vertebrate life. Macmillan Publishing, New York.
Walker, S.M (2002) Fossil fish found live. INC./ Minneapolis,USA.pp 64. ISBN