Потребителски вход

Запомни ме | Регистрация
Постинг
18.01.2016 21:46 - Largest prehistoric animals Vol.1 Vertebrates part11 Sharks - Relatives of Carcharocles megalodon and their cousins
Автор: valentint Категория: Забавление   
Прочетен: 531 Коментари: 0 Гласове:
0

Последна промяна: 03.12.2016 02:53


Family of  Megalodon and other large sharks

image

Otodus obliquus may have reached lengths of 12 m (39 ft) and are estimated to have weighed in at 8 tonnes.
image
Otodus is an extinct genus of mackerel shark which lived during the Paleocene and Eocene epochs, approximately 60 to 45 million years ago. The name Otodus comes from Greek τ (oûs "ear") and δούς, "odous (tooth)", or "ear-shaped tooth".

This shark is known from the fossil teeth and fossilized vertebral centra. Like other elasmobranchs, the skeleton of Otodus was composed of cartilage and not bone, resulting in relatively few preserved skeletal structures appearing within the fossil record. The teeth of this shark are large with triangular crown, smooth cutting edges, and visible cusps on the roots. Some Otodus teeth also show signs of evolving serrations.

The fossils of Otodus indicate that it was a very large macro-predatory shark. The largest known teeth measure about 104 millimetres (4.1 in) in height.The vertebral centrum of this shark are over 12.7 cm (5 inch) wide.Scientists suggest that this shark at least approached 9 metres (30 ft) in total length ,with a maximum length of 12 metres (39 ft).

Otodus had a worldwide distribution, as fossils have been excavated from Africa, Asia, Europe, and North America.

Otodus likely preyed upon marine mammals, large bony fish, and other sharks. It was among the top predators of its time.

Scientists determined that Otodus evolved into the genus Carcharocles, given substantial fossil evidence in the form of transitional teeth. Some teeth have been excavated from the sediments of the Potomac River in Maryland, USA, Ypres clay in Belgium, and western Kazakhstan, which are morphologically very similar to Otodus teeth but with lightly serrated cusplets and a serrated cutting edge. These transitional fossils suggest a worldwide evolutionary event, and support the theory that Otodus eventually evolved into Carcharocles aksuaticus and thus initiated the Carcharocles lineage


Carcharocles chubutensis may have reached lengths of 12 m (39 ft) and are estimated to have weighed in at 10 tonnes.
image
Carcharocles chubutensis,meaning "glorious shark of Chubut", from Ancient Greek is a prehistoric megatoothed shark that lived during Oligocene, Miocene, and Pliocene epochs, approximately 28 – 5 million years ago.This shark is considered to be a close relative of another prehistoric megatoothed shark, C. megalodon. However, as is the case with C. megalodon, the classification of this species is disputed.

This species is also known from fossil teeth and some fossilized vertebral centra. Shark skeleton is composed of cartilage and not bone, and cartilage rarely gets fossilized. Hence, fossils of C. chubutensis are generally poorly preserved. Although the teeth of C. chubutensis are morphologically similar to teeth of C. megalodon, they are comparatively slender with curved crown, and with presence of lateral heels feebly serrated.Fossils of this species have been found in North America,South America,Cuba,Puerto Rico,Africa  and Europe.

C. chubutensis was larger than C. angustidens. Teeth of C. chubutensis can approach 130 mm in slant height (diagonal length), which according to size estimation method proposed by Gottfried at al, in 1996, indicate 12.2 m (40 ft) long specimen.

Paleontological research suggests that this species may have changed habitat preferences through time, or it may have had enough behavioral flexibility to occupy different environments at different times.

C. chubutensis was likely an apex predator and commonly preyed upon fish, sea turtles, cetaceans (e.g. whales)  and sirenids.



Carcharocles auriculatus was about 30 feet long (9 meters)

image
Carcharocles auriculatus is a large extinct shark species of the family Otodontidae, closely related to the sharks of the genus Otodus, and also closely related to the later species megalodon. Its teeth are large, having coarse serrations on the cutting edge, and also with two large cusplets. The teeth can reach up to 130 mm, and belonged to a large "megatoothed" shark.

It is known that there is at least one genus in the family Otodontidae, that being Otodus. But the names and number of the genera in Otodontidae is controversial and the family's accepted phylogeny varies among paleontologists in different parts of the world. In the USA and Britain the most widespread genus name for otodontids with serrated teeth is Carcharocles, and the owners of unserrated ones Otodus. In countries of the former USSR, like Ukraine or Russia, all of these genera were attributed to Otodus, because scientists like Zhelezko and Kozlov thought that the absence or presence of tooth serrations is not enough to place these sharks in different taxa.

The tooth length of C.auriculatus is relatively large - from 25 to 114 mm. However, it is smaller than that of megalodon and Carcharocles angustidens; the tooth length of C. megalodon is 38–178 mm and C. angustidens 25–117 mm.

Most C. auriculatus teeth come from South Carolina. However, many Eocene shark teeth are known from Khouribga Plateau, in Morocco.

Carcharocles auriculatus is the most primitive known member of the genus Carcharocles.

The family of Otodontidae is well known and famous because of its last member - Megalodon. Yet, there were many other genera in this family, first appearing in the Cretaceous. The first one was Cretalamna, one of the largest sharks in the Cretaceous. The teeth basal morphology was similar to the teeth of later Otodus. First, the crown was triangular. This feature helped the shark to bite harder, and this is the feature to which the otodontid evolution was leading for. Second, there was a small protuberance on the labial side of the crown, which is also present in many other species of the family. But there was a feature, which limited the bite force, decreasing the area of the bite, the cusplets. The completely similar absolutely triangular unserrated (all the teeth of Cretalamna had no serrations, the cutting edge was smooth) cusplets were present in a later Otodus obliquus from Paleocene and Eocene. Otodus obliquus is the first large form of otodontid. The maximum size of the teeth was up to 100mm.


C. angustidens may have reached lengths of 9.3 m (31 ft) and are estimated to have weighed in at 4-5 tonnes.
image
Carcharocles angustidens is a prehistoric megatoothed shark, which lived during the
Oligocene and Miocene epochs approximately 35 to 22 million years ago.This shark is believed to be closely related to another extinct megatoothed shark, C. megalodon. However, just as in the case of C. megalodon, the classification of this species is also under dispute.

As is the case with most extinct sharks, this species is also known from fossil teeth and some fossilized vertebral centra. Shark skeleton is composed of cartilage and not bone, and cartilage rarely gets fossilized. Hence, fossils of C. angustidens are generally poorly preserved. To date, the best preserved specimen of this species have been excavated from New Zealand, which comprises 165 associated teeth and about 35 associated vertebral centrum.This specimen is around 26 million years old. C. angustidens teeth are noted for their triangular crowns and small side cusps that are fully serrated. The serrations are very sharp and very well pronounced. C. angustidens was a widely distributed species with fossils found in North America, South America,Europe, Africa, New Zealand, Japan,Australia and Malta.

Like other known megatooth sharks, the fossils of C. angustidens indicate that it was considerably larger than the extant great white shark, Carcharodon carcharias. The well preserved specimen from New Zealand is estimated at 9.3 metres (31 ft) in length.This specimen had teeth measuring up to 9.87 cm (3.89 in) in diagonal length, and vertebral centra of around 1.10 cm (0.43 in) in diameter. However, there are reports of larger C. angustidens fossils.

C. angustidens was an apex predator and likely preyed upon penguins, fish, dolphins, and baleen whales.

 

Cosmopolitodus hastalis was a giant mako shark, up to 8 metres long.
image

Cosmopolitodus is an extinct genus of sharks  known in the fossil records from the Cretaceous to the Quaternary (age range: from 20.43 to 3.6 million years ago). Fossils are found in the marine strata in the Pliocene of Libya, the Netherlands, Portugal,india,Italy and in the Miocene of Chile, the Czech Republic, France, Malta, the Netherlands, Peru and Portugal.

Paratodus benedeni
image
Paratodus is an extinct genus of mackerel shark belonging to the family Lamnidae.
This genus is known in the fossil records from the Miocene to the Quaternary (age range: from 15.97 to 0.781 million years ago). Fossils are found in the marine strata of Italy, Madagascar, Spain, Japan, Malta and United States.
There are different estimates for P. benedi, based on C. carcharias data.Using the measured upper tooth row length yields a total length of 6.5 m. Adding spaces between the tooth would increase the tooth row length by 17% (assuming a spacing comparable to the modern great white shark), yielding a total length of 7.6 m for the animal.
Published weight estimates for the lower end range from 928 to 1,066 kg, and estimates for the higher end range from 4,118 to 4,822 kg.Teeth from private collections indicate specimens 20% longer than the studied ones.
During time, the teeth of P. benedeni got larger and more robust. The ones known from the Oligocene are quite small, but teeth from younger periods are larger and more robust. They likely did so, because marine mammals (which likely made up a great part of P. benedeni's diet) got larger and more diverse within the time.













Тагове:   сова,   prehistoric animals,   giant animals,   sharks,


Гласувай:
0
0



Няма коментари
Търсене

За този блог
Автор: valentint
Категория: Политика
Прочетен: 96994
Постинги: 148
Коментари: 24
Гласове: 12
Архив
Календар
«  Август, 2017  
ПВСЧПСН
123456
78910111213
14151617181920
21222324252627
28293031