Re: What is a Dinosaur ?

[Patrx]

Is this Sideshow's first marine reptile? I don't count Spinosaurus as a marine reptile

lol Well that makes sense as it's not a reptile ! 

Eh? Sure it is. Unless I missed something?

[postsaurischian]

Is this Sideshow's first marine reptile? I don't count Spinosaurus as a marine reptile

lol Well that makes sense as it's not a reptile ! 

Eh? Sure it is. Unless I missed something?

As far as I know Dinosaurs are a class (clade) of their own, not reptiles.

Dr. Admin? ... or other paleontologists?

[Blade-of-the-Moon]

Is this Sideshow's first marine reptile? I don't count Spinosaurus as a marine reptile

lol Well that makes sense as it's not a reptile ! 

Eh? Sure it is. Unless I missed something?

There was probably some confusion there..I was referring to the Spinosaurus..hence it couldn't be a " marine reptile " .  Of course last I heard there was talk that made our prehistoric marine reptiles different from what we think when we here the term..even that they could warm blooded ?

[Patrx]

I was under the impression that dinosaurs were still considered reptiles - strange, warm-blooded reptiles. Perhaps my knowledge is outdated? Perhaps the term "reptile" is no longer taxonomically significant anyway?

[Blade-of-the-Moon]

I was under the impression that dinosaurs were still considered reptiles - strange, warm-blooded reptiles. Perhaps my knowledge is outdated? Perhaps the term "reptile" is no longer taxonomically significant anyway?

The dictionary lists them as such  but I think the term " reptiles " is outdated when applied to dinosaurs as it gives a false impression. So you say they are " birds " now with the general public ? The way this is phrased is honestly confusing as there are different implications. Birds are dinosaurs , but were all dinosaurs birds ?  Perhaps someone else can shed some light on this ?

[thelordsgym]

They are giant lizards....hence in the classification of reptiles....of those creatures is also the scientific knowledge that they grow their entire lives, from what we observe with modern reptiles anyways...which is what Science is supposed to be about....observations, and even demonstratable....after all what is the term Dinosaur? The roots of the word are broken down......Dino (Terrible) saur (Lizard). Now someone is changing what the term dinosaur means? This term was invented in 1842 by Sir Richard Owen....
If it has changed, then the word Dinosaur should also be changed into something else to describe them...

[Blade-of-the-Moon]

They are giant lizards....hence in the classification of reptiles....of those creatures is also the scientific knowledge that they grow their entire lives, from what we observe with modern reptiles anyways...which is what Science is supposed to be about....observations, and even demonstratable....after all what is the term Dinosaur? The roots of the word are broken down......Dino (Terrible) saur (Lizard). Now someone is changing what the term dinosaur means? This term was invented in 1842 by Sir Richard Owen....
If it has changed, then the word Dinosaur should also be changed into something else to describe them...

But some were giant feathered lizards ..and even warm-blooded.

That doesn't fit the definition of the word reptile :
" a cold-blooded vertebrate of a class that includes snakes, lizards, crocodiles, turtles, and tortoises. They are distinguished by having a dry scaly skin, and typically laying soft-shelled eggs on land. "

[thelordsgym]

They are giant lizards....hence in the classification of reptiles....of those creatures is also the scientific knowledge that they grow their entire lives, from what we observe with modern reptiles anyways...which is what Science is supposed to be about....observations, and even demonstratable....after all what is the term Dinosaur? The roots of the word are broken down......Dino (Terrible) saur (Lizard). Now someone is changing what the term dinosaur means? This term was invented in 1842 by Sir Richard Owen....
If it has changed, then the word Dinosaur should also be changed into something else to describe them...

But some were giant feathered lizards ..and even warm-blooded.

That doesn't fit the definition of the word reptile :
" a cold-blooded vertebrate of a class that includes snakes, lizards, crocodiles, turtles, and tortoises. They are distinguished by having a dry scaly skin, and typically laying soft-shelled eggs on land. "

I don't think theres enough evidence/proof to say that the giant ones had any feathers or were warm blooded...after all, they are extinct...what do we compare them to?

[Blade-of-the-Moon]

They are giant lizards....hence in the classification of reptiles....of those creatures is also the scientific knowledge that they grow their entire lives, from what we observe with modern reptiles anyways...which is what Science is supposed to be about....observations, and even demonstratable....after all what is the term Dinosaur? The roots of the word are broken down......Dino (Terrible) saur (Lizard). Now someone is changing what the term dinosaur means? This term was invented in 1842 by Sir Richard Owen....
If it has changed, then the word Dinosaur should also be changed into something else to describe them...

But some were giant feathered lizards ..and even warm-blooded.

That doesn't fit the definition of the word reptile :
" a cold-blooded vertebrate of a class that includes snakes, lizards, crocodiles, turtles, and tortoises. They are distinguished by having a dry scaly skin, and typically laying soft-shelled eggs on land. "

I don't think theres enough evidence/proof to say that the giant ones had any feathers or were warm blooded...after all, they are extinct...what do we compare them to?

Say the giant ones didn't.  There are still smaller dinosaurs that did. They are still dinosaurs..so where does that leave us ?

Not sure where exactly the proof is on the issue of warm-blooded-ness..but it has been taken as fact for quite some time now.

[Patrx]

They are giant lizards....hence in the classification of reptiles....of those creatures is also the scientific knowledge that they grow their entire lives, from what we observe with modern reptiles anyways...which is what Science is supposed to be about....observations, and even demonstratable....after all what is the term Dinosaur? The roots of the word are broken down......Dino (Terrible) saur (Lizard). Now someone is changing what the term dinosaur means? This term was invented in 1842 by Sir Richard Owen....
If it has changed, then the word Dinosaur should also be changed into something else to describe them...

But some were giant feathered lizards ..and even warm-blooded.

That doesn't fit the definition of the word reptile :
" a cold-blooded vertebrate of a class that includes snakes, lizards, crocodiles, turtles, and tortoises. They are distinguished by having a dry scaly skin, and typically laying soft-shelled eggs on land. "

I don't think theres enough evidence/proof to say that the giant ones had any feathers or were warm blooded...after all, they are extinct...what do we compare them to?

Generally, when it comes to taxonomical nomenclature, definitions can change, but the names don't. So, we can redefine what it means to be a dinosaur, but the name stays the same even if it doesn't really fit. Ergo, assuming I am correct in thinking that dinosaurs are still considered "reptiles", birds are reptiles - something that would likely perplex the likes of Carl von Linné, or even Sir Richard Owen!

[tyrantqueen]

Yes, I consider dinosaurs to be reptiles, just not in the traditional sense. After all, crocodiles are called reptiles and they are archosaurs as well. Some scientists include birds as reptiles, under a very broad definition of what a reptile is considered to be.

Of course last I heard there was talk that made our prehistoric marine reptiles different from what we think when we here the term..even that they could warm blooded ?

Even though mosasaurs had ectothermic ancestors, I think they probably evolved a warm blooded (or close to warm blooded) metabolism.

As far as I know Dinosaurs are a class (clade) of their own, not reptiles.

Dr. Admin? ... or other paleontologists?

Dr Bakker suggested putting dinosaurs in their own group, along with birds and crocodiles, but the idea never caught on. And dinosaurs still belong in the archosaur group of reptiles.

There was probably some confusion there..I was referring to the Spinosaurus..hence it couldn't be a " marine reptile " .  Of course last I heard there was talk that made our prehistoric marine reptiles different from what we think when we here the term..even that they could warm blooded ?

To clarify, when I referred to "marine reptiles", I was talking about the sea going variety. The group that most people refer to when they talk of marine reptiles usually consists of plesiosaurs, mosasaurs, etc. Besides, Spinosaurus wasn't fully aquatic.

Speaking of metabolism, I read somewhere that it is possible that the dinosaurs' metabolism could have slowed down as they grew older. I think also that many non-avian dinosaurs could have been somewhere between endothermic and ectothermic, but not pure examples of either.

[Concavenator]

I read something about Dilophosaurus being very weak and with some aquatic lifestyle like spinosaurs...
(Yeh,I've gone out topic  )

[Patrx]

Birds are dinosaurs , but were all dinosaurs birds ?  Perhaps someone else can shed some light on this ?

Just saw this, and I think I can answer. Birds are a clade of dinosaur. All birds are dinosaurs, but not all dinosaurs are birds. There again, however, I recall that there is some dissension regarding the definition of "bird", because it's not the name of a clade in itself, but an informal word. Passer is most certainly a bird, but is Velociraptor? If it isn't, why not? Where is the separation? I certainly don't know.

Also, yeah, I don't think Spinosaurus really qualifies as aquatic.

[HD-man]

Is this Sideshow's first marine reptile? I don't count Spinosaurus as a marine reptile

lol Well that makes sense as it's not a reptile ! 

Eh? Sure it is. Unless I missed something?

To quote Holtz (See "So, What Are Dinosaurs? A Basic Classification": http://www.geol.umd.edu/~tholtz/tyrdeintree.pdf ), "Cladistic analyses of the tetrapods consis-tently show that dinosaurs are a subgroup within the archosaurian reptiles, a group that includes crocodilians among living forms, as well as many extinct creatures.11 Note that call-ing dinosaurs "reptiles" in the cladistic sense tells us nothing about whether dinosaurs were cold-blooded or warm-blooded. Like all cladis-tic names, Reptilia is a group defined by com-mon ancestry, rather than by a general grade of organization. Dinosaurs and their closest rela-tives, such as Marasuchus, are distinguished from all other reptiles by a fully upright stance of the hindlimbs and a simple ankle joint. Fur-thermore, Dinosauria itself is distinguished by an open hip socket. Because of the incomplete-ness of the fossils of the immediate closest rela-tives of dinosaurs, there is some uncertainty as to what other features characterize the com-mon ancestor of all dinosaurs."

[Splonkadumpocus]

"Reptile" is more of an evolutionary grade than an actual clade in my opinion, sort of like "fish" or "invertebrate". I personally define Aves as Passer > Troodon or Velociraptor.

As for marine reptiles and warm blood, there are a number of large, fast-moving fish today (including most sharks) that have an elevated metabolism like mammals, but with a varying body temperature like reptiles. I would expect most of the Mesozoic marine reptiles had something similar.

[Newt]

I have a background in taxonomy.  Perhaps I can help.

First, you have to understand that taxonomic concepts have changed a lot in the last few decades.  Some major changes that are pertinent to this problem:

1) The traditional Linnaean ranks above the genus level - Phylum, Kingdom, Class, Order, Family- are increasingly being replaced by unranked groups called 'clades'.  This is mostly a house-keeping issue; it got too complicated to provide ranks for all the groups, partly due to issue 2 (see below).

2) Only monophyletic clades are recognized as valid.  "Monophyletic" means that the clade includes ALL of the descendants of a common ancestor.  The mammals are a monophyletic group.  So are the birds.  The living amphibians (frogs, salamanders, and caecilians) are a monophyletic group, but if you include all the extinct "amphibians", the group becomes paraphyletic.  The fishes are also a paraphyletic group.

"Paraphyletic" groups are similar to monophyletic groups, except that they exclude some of the descendants of that common ancestor.  You may also come across the term "polyphyletic", which means that the constituents have no particular relationship to one another; for example, if you tried to make a taxonomic group that included all the flying vertebrates (and excluded all the non-flying ones), it would be polyphyletic.

The traditional Class Reptilia was paraphyletic, as it excluded birds and mammals, which are descended from the same common ancestor as the various "reptile" groups.  If you include birds and mammals in the Reptilia, it becomes monophyletic, but is also exactly equivalent to the clade Amniota, and so is redundant.

The upshot is, the traditional Class Reptilia is invalid.  Some taxonomists have proposed a restricted clade Reptilia that would include the nearest common ancestor of Squamata (snakes and other lizards) and Rhynchocephalia (tuataras and many extinct groups) and all its descendants, thus excluding turtles, mammals, and archosaurs (such as crocodilians, dinosaurs, birds, etc.).

The vernacular word "reptile" is still useful as a catch-all for the non-monophyletic group of all amniotes that are neither mammals nor birds, but has no formal taxonomic standing.  In that sense it is similar to the word "fish", which means all craniates that are not tetrapods.

So, all clear now? :p

*EDIT* Several replies were made while I was typing.  Sorry for any redundancy.

[Spinosaurus Aegyptiacus]

I have a background in taxonomy.  Perhaps I can help.

First, you have to understand that taxonomic concepts have changed a lot in the last few decades.  Some major changes that are pertinent to this problem:

1) The traditional Linnaean ranks above the genus level - Phylum, Kingdom, Class, Order, Family- are increasingly being replaced by unranked groups called 'clades'.  This is mostly a house-keeping issue; it got too complicated to provide ranks for all the groups, partly due to issue 2 (see below).

2) Only monophyletic clades are recognized as valid.  "Monophyletic" means that the clade includes ALL of the descendants of a common ancestor.  The mammals are a monophyletic group.  So are the birds.  The living amphibians (frogs, salamanders, and caecilians) are a monophyletic group, but if you include all the extinct "amphibians", the group becomes paraphyletic.  The fishes are also a paraphyletic group.

"Paraphyletic" groups are similar to monophyletic groups, except that they exclude some of the descendants of that common ancestor.  You may also come across the term "polyphyletic", which means that the constituents have no particular relationship to one another; for example, if you tried to make a taxonomic group that included all the flying vertebrates (and excluded all the non-flying ones), it would be polyphyletic.

The traditional Class Reptilia was paraphyletic, as it excluded birds and mammals, which are descended from the same common ancestor as the various "reptile" groups.  If you include birds and mammals in the Reptilia, it becomes monophyletic, but is also exactly equivalent to the clade Amniota, and so is redundant.

The upshot is, the traditional Class Reptilia is invalid.  Some taxonomists have proposed a restricted clade Reptilia that would include the nearest common ancestor of Squamata (snakes and other lizards) and Rhynchocephalia (tuataras and many extinct groups) and all its descendants, thus excluding turtles, mammals, and archosaurs (such as crocodilians, dinosaurs, birds, etc.).

The vernacular word "reptile" is still useful as a catch-all for the non-monophyletic group of all amniotes that are neither mammals nor birds, but has no formal taxonomic standing.  In that sense it is similar to the word "fish", which means all craniates that are not tetrapods.

So, all clear now? :p

*EDIT* Several replies were made while I was typing.  Sorry for any redundancy.

Really helpful; thanks for sharing!

[Gwangi]

Just to expand on and illustrate what Newt is saying...

Below are the animals traditionally classified as reptiles, you can see the problem here because it excludes groups that evolved from reptiles. A species cannot evolve outside its parent group. You know how you've always been told apes are not monkeys? Wrong! Apes evolved from old world monkeys therefore...they are monkeys. The old world monkeys are more closely related to apes than they are to new world monkeys so if old world monkeys are still monkeys, apes are as well. For these same reasons, birds are dinosaurs and ALL tetrapods are lobe-finned fishes...because those fish from which we evolved are more closely related to us than to the other fishes. Fishes in terms of cladistics, is also paraphyletic.


So really what we are living through is a conversion from the old ways to the new in terms of classification and it is messy. Reptiles and Fishes in terms of classification are defunct terms that don't help us all understand how various animal groups are related but they do help us differentiate between the living groups of animals. If I say "oh look, a reptile"....you'll know what I'm talking about but the usefulness of the term ends there.

As for birds and where to draw the line on what is or is not...it is all arbitrary. There is no line. There is no point during evolution where you can draw a line and say..."this is a bird and this is not" because the lines are blurred. It helps to look at it like this...



You can differentiate between blue and white but there is no point in-between where you can draw a line to divide them. The new method of classification called cladistics attempts to reconcile the problems of the old. We now place groups of animals in clades...smaller groupings within the whole. So not instead of saying...the house sparrow is a bird and Velociraptor is a dinosaur you would say...

Housesparrow<Aves (birds)<Eumaniraptora (along with Velociraptor)<Paraves<Maniraptora (along with Therizinosaurus, Oviraptor etc.)<Maniraptoriformes (along with Ornithomimosaurs)<Coelurosauria (along with Tyrannosaurus and kin)<Avetheropoda (along with Carnosaurs)<Theropoda.

And even that is simplified, I left out some clades. What grouping organisms in clades does though is groups closely related animals together by looking at their shared characteristics. It is still not ideal because like the colors, parent groups bleed into their daughter groups with not clear line where one ends but we have to draw lines somewhere. Hope all that helps.

[Yutyrannus]

I agree. I, to be honest, have never thought of dinosaurs as reptiles. I think really either birds need to get lumped into reptilia or they and other dinosaurs as well as crocodiles get put into an entirely new group (the better decision in my opinion).

[tyrantqueen]

I agree. I, to be honest, have never thought of dinosaurs as reptiles. I think really either birds need to get lumped into reptilia or they and other dinosaurs as well as crocodiles get put into an entirely new group (the better decision in my opinion).

What do you think of them as, then?