Fossils

[kingwinner]

1) Differentiate precisely between a chemically altered (petrified) fossil and a cast fossil.

A petrified fossil and a cast fossil seem to be the same to me. They are both mineral replica of the original organism...

 

 

 

 

 

2) For the above chart of index fossils, I don't know which is the name of the fossil and what does the other represent? For example, the second one, Pecten jeffersonius, MOLLUSCA, Pelecypoda, scallop, which is the name of the fossil and what does each of the above terms represent? For the "Tertiary-Quaternary" at the end, is it saying that this is a index fossil of both the Tertiary and Quaternary Periods?

 

3) For the first one (Oleneothyris harlani), unlike the other three, there is nothing written after BRACHIOPODA, why?

 

I didn't take biology so this stuff is a pain for me! Can someone explain? I would really appreciate! :rolleyes:

[MortenS]

As I understand petrified fossils vs cast fossil:

 

Petrified fossils are fossils where the dead organism gradually gets replaced by minerals. This means that you can study the internal structure of a petrified fossil.

 

A cast fossil, is an imprint of the surfaces of the fossil, while the organism itself has decayed away.

 

A petrified fossil of a tree would show the yearly growth rings, even when you cut the fossil, while a cast fossil would only show the surface of the tree.

 

I am no geologist, but that is my understanding.

 

I also undertand Tertiary-Quaternary to mean just that. If you find this fossil, you have an age of the strata set to between Tertiary and Quaternary.

[MortenS]

 

2) For the above chart of index fossils, I don't know which is the name of the fossil and what does the other represent? For example, the second one, Pecten jeffersonius, MOLLUSCA, Pelecypoda, scallop, which is the name of the fossil and what does each of the above terms represent? For the "Tertiary-Quaternary" at the end, is it saying that this is a index fossil of both the Tertiary and Quaternary Periods?

 

3) For the first one (Oleneothyris harlani), unlike the other three, there is nothing written after BRACHIOPODA, why?

 

I didn't take biology so this stuff is a pain for me! Can someone explain? I would really appreciate! :rolleyes:

 

First of all, you need to know that everything in biology is classified in a hiearchic system, including fossils.

Starting at the top-level going to the bottom, we usually group organisms into:

Domain, Kingdom, Phyla, Class, Order, Family, Genus, species

 

Sometimes the prefixes sub- and super-, infra- are added to some of these to create further divisions, especially in species-rich groups with lot of diversity (like crustaceans)

 

If we take Pecten jeffersonius, MOLLUSCA, Pelecypoda, scallop as an example, we have Pecten jeffersonius as the species name, MOLLUSCA as the name of the phylum this species belongs in, and Pelecypoda is the name of the class this species belongs in. Scallop is the name of the organism in english.

 

For the first species, Oleneothyris harlani, only the name of the phylum is given. There may be several reasons for this: the author doesn't know, or the classification might be uncertain (or there might be some other reason).

 

Many fossils are lumped together in a incerta sedis group, since further classification is not allways possible due to lack of characters to group the organism after or some other reason.

 

However, given the latin name, we can look up further classification, if it exists.

 

A quick search with Google tells us that the species belongs in the family Terebratulidae, and we can look up the rest of the classification.

 

So we have:

Domain Eukaryota

Kingdom Animalia

Phylum BRACHIOPODA

Class Articulata

Order Terebratulida

Family Terebratulidae

Genus Oleneothyris

species harlani

 

Classifications are a bit arbitrary at times, especially with fossils, and there might be some different opinions among authours on what rank various groups should have.

 

You can work out similar classifications for the others.

[kingwinner]

As I understand petrified fossils vs cast fossil:

 

Petrified fossils are fossils where the dead organism gradually gets replaced by minerals. This means that you can study the internal structure of a petrified fossil.

 

A cast fossil, is an imprint of the surfaces of the fossil, while the organism itself has decayed away.

 

A petrified fossil of a tree would show the yearly growth rings, even when you cut the fossil, while a cast fossil would only show the surface of the tree.

 

I am no geologist, but that is my understanding.

 

I also undertand Tertiary-Quaternary to mean just that. If you find this fossil, you have an age of the strata set to between Tertiary and Quaternary.

HI,

 

1) A cast fossil is when a mold is filled with minerals/sediments, so it is still a mineral replica of the organism...and now I am puzzled...I can't tell how cast fossil and petrified fossil are different...

[MortenS]

It is a difference...when you have a petrified fossil, the dead organism itself gets petrified, that is, gradually exchanged with minerals. A cast is just the filling of the empty space left behind by the organism after it has decayed or been destroyed in other ways.

 

You can even see cell structures inside petrified fossils some times.

 

http://waynesword.palomar.edu/plapr96.htm#ginkcell

 

Cell structures are not preserved in cast fossils.

[kingwinner]

First of all, you need to know that everything in biology is classified in a hiearchic system, including fossils.

Starting at the top-level going to the bottom, we usually group organisms into:

Domain, Kingdom, Phyla, Class, Order, Family, Genus, species

 

Sometimes the prefixes sub- and super-, infra- are added to some of these to create further divisions, especially in species-rich groups with lot of diversity (like crustaceans)

 

If we take Pecten jeffersonius, MOLLUSCA, Pelecypoda, scallop as an example, we have Pecten jeffersonius as the species name, MOLLUSCA as the name of the phylum this species belongs in, and Pelecypoda is the name of the class this species belongs in. Scallop is the name of the organism in english.

 

For the first species, Oleneothyris harlani, only the name of the phylum is given. There may be several reasons for this: the author doesn't know, or the classification might be uncertain (or there might be some other reason).

 

Many fossils are lumped together in a incerta sedis group, since further classification is not allways possible due to lack of characters to group the organism after or some other reason.

 

However, given the latin name, we can look up further classification, if it exists.

 

A quick search with Google tells us that the species belongs in the family Terebratulidae, and we can look up the rest of the classification.

 

So we have:

Domain Eukaryota

Kingdom Animalia

Phylum BRACHIOPODA

Class Articulata

Order Terebratulida

Family Terebratulidae

Genus Oleneothyris

species harlani

 

Classifications are a bit arbitrary at times, especially with fossils, and there might be some different opinions among authours on what rank various groups should have.

 

You can work out similar classifications for the others.

Thank you for explaning!

 

Why doesn't the third picture have the name for "Species"? (only the Genus with the first letter captalized is written there, is it?)

 

Another index fossil:

Equus

CHORDATA, Mammalia

(horse tooth; Quaternary)

 

The class here is written as "Mammalia", but in another source, everything is written the same way except the class is written as "Mammal". Why is it so strange? Which one is the correct form?

Is Equus the name of the genus?

[MortenS]

Thank you for explaning!

 

Why doesn't the third picture have the name for "Species"? (only the Genus with the first letter captalized is written there, is it?)

 

Another index fossil:

Equus

CHORDATA, Mammalia

(horse tooth; Quaternary)

 

The class here is written as "Mammalia", but in another source, everything is written the same way except the class is written as "Mammal". Why is it so strange? Which one is the correct form?

Is Equus the name of the genus?

 

I am not familiar with identifying fossils, but when I identify insects, sometimes I do not manage to find out what species it is, but I can easily see what genus a fly belongs to. Some genera may have so many species in it, so that identification to species level might be difficult, while other genera have few species within it, and may be more easy to separate. I think it mainly has to do with the ease of identification.

 

As for the horse tooth, it might be easy to identify a tooth to belonging to a horse, but it might not be that easy to identify it to a specific species.

 

Just naming the genus means that you are uncertain about the species.

 

Mammal is the english name of an organism within the class Mammalia.

Mammalia is the correct latin form.

 

Hope that helps..

[kingwinner]

I am not familiar with identifying fossils, but when I identify insects, sometimes I do not manage to find out what species it is, but I can easily see what genus a fly belongs to. Some genera may have so many species in it, so that identification to species level might be difficult, while other genera have few species within it, and may be more easy to separate. I think it mainly has to do with the ease of identification.

 

As for the horse tooth, it might be easy to identify a tooth to belonging to a horse, but it might not be that easy to identify it to a specific species.

 

Just naming the genus means that you are uncertain about the species.

 

Mammal is the english name of an organism within the class Mammalia.

Mammalia is the correct latin form.

 

Hope that helps..

 

For this organism, as an example,

 

Crinoid

ECHINODERMATA, Crinoidea

(sea "lily" stem, Mississippian)

 

Is the following the correct interpretation of it??

Species: (Not given)

Genus: Crinoid

Phylum: ECHINODERMATA

Class: Crinoidea

English common name: sea "lily" stem

Time period: Mississippian

 

So Mammal = Mammalia, both are "class"??

 

When writing the names of Kingdom, Phylum, Class, Order, Family, Genus, species of an organism, do we always have to use the Latin name?

[MortenS]

I am afraid it is not that easy. It seems like your textbook is using mixture of latin and english terms.

 

Crinoid is an anglification of the class name in this instance, not the genus name.

 

In this instance, the only thing that is known is the phylym and class name.

 

Why use latin names?

 

It is mostly a communication issue. When you refer to a latin name of an organism, I know and all other biologists know what you refer to, and we can easily mine literature for all available data about the organism, because all scientific articles about the organism use latin names.

 

If every scientist used only their local names for organisms, you would only get up the articles made in your own language, but not in other languages (like german, french, russian, chinese or japanese).

 

As a scientists, you might have to hunt down information in an article of a language you do not understand. To get such an article translated, it is nice to at least know that it deals with the organism you are interested in, before you go to the step of translating it.

 

This is just a few of the beneficial aspects of usig latin names in geological and biological sciences.

 

When you speak to a native audience, you use local terms if possible.