Your favourite "living fossils"?

[freeztar]

Originally Posted by Eclogite

We should be careful not to presume superficial phenotypic similarities are tantamount to genotypic near identity.

Indeed. Which were you referring to specifically?

[Eclogite]

Originally Posted by freeztar

Indeed. Which were you referring to specifically?

All of them, probably. The 'popular' ones definitely.

The star entrant for undergraduate palaeontologists is probably Lingula. It certainly has an excellent pedigree, being a genus of brachiopods from the Cambrian that continues to this day 'unchanged', we are told.

This turns out not to be the case. While the gross morphology and favoured environment have been constant there have been changes going on 'behind the scenes'. Thus the apatitic rods that form part of the shell have been replaced by botryoidal aggregates from Carboniferous times onwards. These brachiopods are evolving and have evolved, its just their gross appearance that seems unchanged. Their genetic make up is different and different in important ways.

It seems to me that the interest in finding 'living fossils' is one based more in romance than science. I see nothing wrong with that: fascination with the peculiarities of the universe is what attracts many of us to science, but we blind ourselves to important processes if we believe that living fossils are 'unchanged'.

Thunderbird, I am unfamiliar with the fascinating bird you have cited. Has it been found fossilised? If not we can scarcely call it a living fossil. I suspect - but await clarification from yourself - that it is a bird with primitive features. A bird has many of the genes that would let it develop even more reptilian characteristics than it already has. Rather than being a living fossil, this may be a retrogression.

[Moontanman]

Originally Posted by Eclogite

All of them, probably. The 'popular' ones definitely.

The star entrant for undergraduate palaeontologists is probably Lingula. It certainly has an excellent pedigree, being a genus of brachiopods from the Cambrian that continues to this day 'unchanged', we are told.

This turns out not to be the case. While the gross morphology and favoured environment have been constant there have been changes going on 'behind the scenes'. Thus the apatitic rods that form part of the shell have been replaced by botryoidal aggregates from Carboniferous times onwards. These brachiopods are evolving and have evolved, its just their gross appearance that seems unchanged. Their genetic make up is different and different in important ways.

It seems to me that the interest in finding 'living fossils' is one based more in romance than science. I see nothing wrong with that: fascination with the peculiarities of the universe is what attracts many of us to science, but we blind ourselves to important processes if we believe that living fossils are 'unchanged'.

Thunderbird, I am unfamiliar with the fascinating bird you have cited. Has it been found fossilised? If not we can scarcely call it a living fossil. I suspect - but await clarification from yourself - that it is a bird with primitive features. A bird has many of the genes that would let it develop even more reptilian characteristics than it already has. Rather than being a living fossil, this may be a retrogression.

You are of course correct but I really don't think anyone who is talking about living fossils really thinks any animals alive today are genetically the same as a similar animal from even thousands of years ago much less many millions of years. I've always understood the term to mean animals that share common decent and are physically very similar to life forms from millions of years ago.

[Eclogite]

Originally Posted by Moontanman

You are of course correct but I really don't think anyone who is talking about living fossils really thinks any animals alive today are genetically the same as a similar animal from even thousands of years ago much less many millions of years.

I fully accept that most - hopefully all - of the posters in this thread appreciate that fact, but what of the casual reader who is trying to learn a little biology from the posts. My point is that the distinction is not made with sufficient vigour for the idea to get across to everyone. That was my motivation for my somewhat tangential post.

Now we should return to our living fossils, where I join with several others in agreeing that birds are undoubtedly dinosaurs. And I ask, since some birds can speak, and some scientists claim that they can understand some of that speech, then how do we find evidence from the Cretaceous for talking dinosaurs?

[Thunderbird]

Originally Posted by Eclogite

Thunderbird, I am unfamiliar with the fascinating bird you have cited. Has it been found fossilised? If not we can scarcely call it a living fossil. I suspect - but await clarification from yourself - that it is a bird with primitive features. A bird has many of the genes that would let it develop even more reptilian characteristics than it already has. Rather than being a living fossil, this may be a retrogression.

Probably so.. fascinating and telling nonetheless.

[Moontanman]

Originally Posted by Eclogite

I fully accept that most - hopefully all - of the posters in this thread appreciate that fact, but what of the casual reader who is trying to learn a little biology from the posts. My point is that the distinction is not made with sufficient vigour for the idea to get across to everyone. That was my motivation for my somewhat tangential post.

Now we should return to our living fossils, where I join with several others in agreeing that birds are undoubtedly dinosaurs. And I ask, since some birds can speak, and some scientists claim that they can understand some of that speech, then how do we find evidence from the Cretaceous for talking dinosaurs?

Hmmm, talking dinosaurs? Maybe some of those odd objects that have come to light in mine shafts and other places are the result of a dinosaurian civilization?

[Turtle]

Originally Posted by mynah

I'm doing an article on the topic, which is more directed towards the popular and high school market than most of the stuff I write, and wondered which animals, plants and other almost unchanged from the dawn of time organisms to include in a frozen-in-time top 10. ...

Uhmmmm.... I pick 's of course.

[mynah]

There was a reason for the quotation marks in the title, and I certainly plan to clarify the issue in my article. As for the hoatzin, genetic studies confirm that it is somewhat remote from other birds, being basal to a large clade in which cuckoos, cranes, turacos, penguins and shorebirds are more closely related to each other than to the hoatzin.

Although not strictly a scientific concept, "living fossils' do contribute greatly to our understanding of evoltion as a result of making transitional characteristics and their underlying genetic mechanisms available for scientific study.

[Thunderbird]

Originally Posted by mynah

There was a reason for the quotation marks in the title, and I certainly plan to clarify the issue in my article. As for the hoatzin, genetic studies confirm that it is somewhat remote from other birds, being basal to a large clade in which cuckoos, cranes, turacos, penguins and shorebirds are more closely related to each other than to the hoatzin.

Although not strictly a scientific concept, "living fossils' do contribute greatly to our understanding of evoltion as a result of making transitional characteristics and their underlying genetic mechanisms available for scientific study.

Thank you for the classification perspective on the hoatzin. I've been wondering about that.

[Thunderbird]

The Frilled Shark is a truly ancient species that has changed very little since pre-historic times—fossil evidence of the shark dates back to 95 million years. The shark is rarely seen alive since its natural habitat is over 1600 feet (488 meters) below sea level. Specimens have been found scattered around the globe, but the majority of Frilled Sharks have been found in Japanese waters.
The Frilled Shark resembles a giant eel more than a shark. However, the species possesses six gill slits, which identify it as a shark rather than an eel. The Frilled Shark has an upper jaw that is part of its skull, which is unique among living sharks. Most sharks living today have a hinged top jaw.
The Frilled Shark gives birth to live young and remains pregnant for as long as 3 1/2 years—the longest gestation period of any vertebrate known on Earth

Rare, Prehistoric Frilled Shark in Japan