Evolution of Sharks
Insert Name:
Instructor’s Name:
Course:
Date: 08/July/2010
Sharks have been in existence for more than 300 million years. Their evolution occurred over 150 million years earlier than that of the dinosaurs. Most of the existing fossil data of early sharks was collected from fossilized teeth together with several skin impressions. primitive sharks (Cladodonts) , had teeth which were double-pointed, up to 2metres in length, ate fish as well as crustaceans, and existed approximately 360 million years ago. The earliest shark-like beings shown in the fossil records seem to have existed towards the start of the Silurian age, close to 450 million years ago, however the earliest fossil teeth known of actual sharks was not discovered until the Devonian age, about 400,000,000 years ago. Their teeth were not more than 4 millimeters or 0.16 inches across. A candidate for close comparison is Antarctilamna, whose bones have been discovered in the Antarctic continent rocks. This fish was forty centimeters long, and conspicuously shark-like. Its spine was located at the front of a long dorsal fin, additionally its teeth that had 2 huge splayed cusps, and smaller cusps positioned between them. The era of fishes During the Devonian period the first key radiation of sharks began. This is referred to as the 'age of fishes'—during this period all fishes, including sharks, began to diversify greatly. Cladoselache was one of the most primitive true shark skeletons discovered intact. Fossils of ray-finned fish were found intact in some of their stomachs, their direction shows that they were captured tail-first, and therefore Cladoselache must have been skilled in swimming faster than its prey. Close to twenty five per cent of species so far discovered had been feeding on Convaricaris crustacean which obscured itself in sediments on the sea floor and fed on the lifeless flesh of squid and
Instructor’s Name:
Course:
Date: 08/July/2010
Sharks have been in existence for more than 300 million years. Their evolution occurred over 150 million years earlier than that of the dinosaurs. Most of the existing fossil data of early sharks was collected from fossilized teeth together with several skin impressions. primitive sharks (Cladodonts) , had teeth which were double-pointed, up to 2metres in length, ate fish as well as crustaceans, and existed approximately 360 million years ago. The earliest shark-like beings shown in the fossil records seem to have existed towards the start of the Silurian age, close to 450 million years ago, however the earliest fossil teeth known of actual sharks was not discovered until the Devonian age, about 400,000,000 years ago. Their teeth were not more than 4 millimeters or 0.16 inches across. A candidate for close comparison is Antarctilamna, whose bones have been discovered in the Antarctic continent rocks. This fish was forty centimeters long, and conspicuously shark-like. Its spine was located at the front of a long dorsal fin, additionally its teeth that had 2 huge splayed cusps, and smaller cusps positioned between them. The era of fishes During the Devonian period the first key radiation of sharks began. This is referred to as the 'age of fishes'—during this period all fishes, including sharks, began to diversify greatly. Cladoselache was one of the most primitive true shark skeletons discovered intact. Fossils of ray-finned fish were found intact in some of their stomachs, their direction shows that they were captured tail-first, and therefore Cladoselache must have been skilled in swimming faster than its prey. Close to twenty five per cent of species so far discovered had been feeding on Convaricaris crustacean which obscured itself in sediments on the sea floor and fed on the lifeless flesh of squid and
Cited: James Seth. Voracious Evolution. New York: Scribner 's, 2008: 62-87. Ezekiel, G. Robinson. Silent Hunters of the Deep. NewYork: Burdett, & co, 2008: 35-47. Steve and Jane Parker. The Encyclopedia Of Sharks. London: Elsevier, 2006 : 96-123 .