When did Placodontia go extinct?


When did the ichthyopterygians become extinct?

Ichthyopterygians are the second largest group of Mesozoic marine reptiles and produced some of the largest individuals. They are also the second in terms of the duration of their existence—they appeared in late Early Triassic and became extinct in the early Late Cretaceous (Fig. 2 ).

What are some examples of extinct reptiles?

In addition to the living reptiles, there are many diverse groups that are now extinct, in some cases due to mass extinction events. In particular, the Cretaceous–Paleogene extinction event wiped out the pterosaurs, plesiosaurs, and all non-avian dinosaurs alongside many species of crocodyliforms, and squamates (e.g., mosasaurs ).

When did the first fish-shaped ichthyosaurs appear?

Second, the truly fish-shaped ichthyosaurs (i.e., parvipelvians) existed as early as the Norian (Late Triassic), as seen in Hudsonelpidia (McGowan 1995) and Macgowania (McGowan 1996 ). This leaves about 30 million years between the invasion of the sea by early ichthyopterygians and the appearance of the true fish-shaped ichthyopterygians.

Are Reptiles Prehistoric?

Many species of reptiles look a little prehistoric. In fact, most dinosaurs could be classified as reptiles, and reptilian fossils that date back to over 300 million years. Reptiles existed well before any of the mammals we know today.

What kind of body shape did ichthyosaurs have?

The ichthyosaurs of the middle to late Triassic period, such as Grippia, Utatsusaurus and Cymbospondylus, tended to lack dorsal (back) fins and the streamlined, hydrodynamic body shapes of later members of the breed.

How did Ichthyosaurus get its name?

However, in 1817, Karl Dietrich Eberhard Koenig had already referred to the animal as Ichthyosaurus, “fish saurian” from Greek ἰχθύς, ichthys, “fish”. This name at the time was an invalid nomen nudum and was only published by Koenig in 1825, but was adopted by De la Beche in 1819 in a lecture where he named three Ichthyosaurus species.

Were ichthyosaurs warm-blooded or cold-blooded?

Whales and dolphins are mammals and warm-blooded. Of ichthyosaurs it was traditionally assumed that they were cold-blooded, being reptiles.

What is unique about ichthyosaur vertebrae?

This morphology is unique within the Amniota and makes discerning ichthyosaur vertebrae from those of other marine reptiles easy. The only process that kept its function was the spine at the top, serving as an attachment for the dorsal muscles.

What are the similarities between ichthyosaurs and dolphins?

Apart from the obvious similarities to fish, the ichthyosaurs also shared parallel developmental features with dolphins. This gave them a broadly similar appearance, possibly implied similar activity and presumably placed them broadly in a similar ecological niche.

Why are dolphins and ichthyosaurs so similar?

The similarity of these structures is one form of evidence that the organisms share a common ancestor natural selection could not occur without genetic variation in species fossil evidence shows that ancient aquatic reptiles called ichthyosaurs looked very similar to modern dolphins.

fossil evidence shows that ancient aquatic reptiles called ichthyosaurs looked very similar to modern dolphins. However, ichthyosaurs and dolphins are not closely related animals.

Can Dolphins share a common ancestor without genetic variation?

share a common ancestor natural selection could not occur without genetic variation in species fossil evidence shows that ancient aquatic reptiles called ichthyosaurs looked very similar to modern dolphins. However, ichthyosaurs and dolphins are not closely related animals.

Why are there so many ichthyosaurs in the textbook?

That’s why ichthyosaurs are a textbook staple. Mesozoic “fish lizards”, ichthyosaurs were marine reptiles that independently became adapted to a life at sea around 200 million years before dolphins.

Can two organisms have the same genetic code and evolutionary history?

You wrote “As I will explain, the genetic code is remarkably redundant and pliable, and you can have two very similar organisms with very different genetic codes and evolutionary histories”, as a way to rebutt the “essentialist argument” (i.e. frogs have frogs genes because otherwise they wouldn’t be frogs).

By identifying the bones as being homologous and proposing that humans, bats, and dolphins share a common ancestor. Ichthyosaurs were aquatic dinosaurs. Fossils show us that they had dorsal fin and tails, as do fish, even through their closest relatives were terrestrial reptiles that had neither dorsal fins nor aquatic tails.

Why do amphibians and reptiles share a common ancestor?

That’s not something that you would expect under creationism, but it is what evolution predicted, because the fossil record clearly showed that both modern amphibians and reptiles evolved from ancient amphibians. Thus, evolution predicted that modern amphibians and reptiles should share a common ancestor.

Do all mammals share a common ancestor?

We can continue to use the same methods to show that all mammals share a common ancestor, all animals share a common ancestor, and ultimately that all life on planet earth evolved from a common ancestor. Creationists, of course, object to this in the strongest possible terms.

Are ichthyosaurs reptiles?

On applying the new skills, paleontologists started to agree that ichthyosaurs were indeed reptiles of the group Diapsida, which includes snakes, lizards, crocodiles and dinosaurs.

Do all species have the same coding sequence?

Practically, having the same code means that you can put a coding sequence from any species into any other species, and it should produce the same protein. However, regulatory code has diverged much.

How are genes used to reconstruct the evolution of organisms?

As the ability to sequence the nucleotides making up DNA has improved, it also has become possible to use genes to reconstruct the evolutionary history of organisms. Because of mutations, the sequence of nucleotides in a gene gradually changes over time. The more closely related two organisms are, the less different their DNA will be.

Does all life have the same genetic code?

Does all life have exactly the same genetic code? If you the components of DNA, yes. The DNA of all living this is composed of adenine, cytosine, guanine, and thymine linked by a deoxyribose phosphate backbone. If you mean the sequence of those nucleotides in the DNA, that is different for all species.

How similar are echolocating bats and dolphins?

The researchers discovered genetic signatures consistent with convergence in nearly 200 genomic regions when it came to dolphins and echolocating bats. Many of these genes are linked with hearing or deafness. These similarities were not seen with non-echolocating animals.

Why do bats and dolphins use sonar?

This biological version of sonar evolved separately in bats and dolphins, helping these animals hunt prey and avoid obstacles. [ Deep Divers: A Gallery of Dolphins]

Do dolphins and bats have the same genes?

Bats and dolphins may live in radically different worlds, but the fact they both evolved a type of sonar means they resemble each other genetically, researchers now find. When different species live similar lives, they can evolve similar traits, a phenomenon known as convergent evolution.

How do dolphins sharks and ichthyosaurs differ from each other?

For instance, dolphins, sharks and the extinct marine giants known as ichthyosaurs all differ from each other greatly in origin — dolphins are mammals, sharks are fish and ichthyosaurs were reptiles.

Are two species that share a common ancestor closely related?

Also, in evolutionary terms, we would say that two species that share a common ancestor at junction [A] would be more closely related than those species sharing a common ancestor at junction [B]. All pretty straightforward – but, this is where the reptile label runs into a problem.