Study of Fossil: Icthyosaur
Systematic Position:
Kingdom: Animalia
Phylum: Chordata
Sub Phylum: Vertebrata
Super Class: Gnathostomata
Class: Reptilia
Clade: Eoichthyosauria
Order: Ichthyosauria
Origin:
Observed from late Early Triassic period through to the early Late Cretaceous.
Termed as “Swimming Dinosaurs” & ‘Lizard with flippers’
Their fossil remains span almost the entire Mesozoic Era (251 million to 65.5 million years ago); but they were most abundant and diverse during the Triassic and Jurassic periods (251 million to 145.5 million years ago). Excellent fossil specimens occur in the fine-grained Early Jurassic shelves of southern Germany.
Ichthyosaurs were particularly abundant in the Late Triassic and Early Jurassic periods.
Streamlined body. Head is blended smoothly into the body.
No distinct neck was present.
It was about 3 meters (10 feet) long and was probably able to move through the water at high speeds. Very fishlike in appearance.
The limbs were modified into paddle-like appendages used to steer the animal. It propelled itself by using a well- developed fishlike tail and by undulating the body.
The vertebral column, which was formed from disk-like structures, bent downward into the lower lobe of the caudal, or tail, fin.
The skull and jaws of Ichthyosaurus were long and contained numerous sharp teeth.
Several specimens were found in which the skeletal remains of small, immature ichthyosaurs are fossilized within the bodies of larger individuals, even within the birth canal.
Evolutionary Significance:
Ichthyosaur, are an extinct group of aquatic reptiles, most of which were very similar to porpoises in appearance and habits. These distant relatives of lizards and snakes (Lepidosaurs) were the most highly specialized aquatic reptiles.
Their eyes are large, a trait some scientists believe gave these reptiles the ability to discern large shapes, such as those of the Pliosaurs, at long distances.
The nostrils were positioned far back on the top of the skull, specialized adaptation to an aquatic existence.
Ichthyosaurs persisted into Late Cretaceous times and may have been well adapted for deep diving as well as near-shore predation, but all species became extinct well before the end of the Cretaceous Period.
Ichthyosaurs are Index fossils for plate tectonics and continental drift. They are commonly found, but distantly (on erstwhile Gondwana land remnants) distributed fossils that are limited in time span (Early Triassic to Late Cretaceous)
Some 240 million years ago, a dolphin-like ichthyosaur ripped to pieces and swallowed another marine reptile only a little smaller than itself. Then it almost immediately died and was fossilized, preserving the first evidence of megapredation, or a large animal preying on another large animal.(Guizhou province, China in 2010)
Ichthyosaur fossils find in Kutch, Gujrat shows India's biological connect as part of Gondwanaland during Jurassic. The discovery hints at the movement of animals between Indo-Madagascar & Mediterranean faunal provinces, during the Jurassic period.
The discovery hints the movement of animals between Indo-Madagascar & Mediterranean faunal provinces, during the Jurassic Period.
Ichthyosaur Fossil found in Kutch desert region of Gujarat. Photo Credit:Times of India
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