Mammal Teeth and Dental Terminology/Information

[RyanDye]

Have you ever wondered what a diagram such as one of these actually means?

 

                                    

Well today hopefully I will answer your questions! 

To start with lets understand what the letters C, P, I, and M these abbreviations stand for Canine, Premolar, Incisors, and Molar. The incisors are the front most teeth, and in any scientific article they would be described as the anterior most teeth. Now, to better explain the diagram above on the left, when numbering teeth we number them by the distance from the centerline; if you have four incisors the gap between the two middle teeth would be considered the centerline. So if you see a dental formula with 2 incisors or 1 molar it is talking about on ONE side, NOT both sides. The numerators on the formula represent the upper teeth, and the denominators represent the lower teeth. 

 

 While teeth are NOT the same in all mammals! For example, rodents have less incisors than other mammals. Also, if the letter representing the tooth is capitalized it is referring to the top set of teeth, if the letter is lowercase it is referring to lower set. (P4 = top, fourth premolar; i1 = lower, first incisor)

 

Now as I was saying, how you would number teeth such as I3, or P2, M1 etc. there is an exception to every rule. Sometimes the ancestral tooth makeup will change the labelling. Let's use the evolutionary timeline of the modern feline as an example; Proailurus lemanensis, a very primitive species that gave rise to many of the modern feline genera today; as you can see below, had many teeth! Later in the geological timeline, a descendant genera Pseudaelurus appeared, but as you can see it had seemed to lost the 2nd molar, while this wouldn't affect how the teeth are numbered, when the modern cat was formed it lost even more teeth. Why is this important? Because as you can see there are only 3 cheek teeth (molars + premolars) in the modern cat yet the model says there is a P4; you and I know that it is referring to the tooth structure of Proailurus and Pseudaelurus, but had you seen the labels on the modern cat alone it wouldn't make sense because there are only 3 cheek teeth there. So don't always assume the number of teeth will correlate with the tooth number that it's labeled as.

 

The two kinds of cheek teeth; alright this is where it gets confusing so pay close attention, before I explain the two types of cheek we need to understand what 'cusps' are.  This diagram labels the cusps, the primary cusps on the upper molars are called the protocone, metacone and the paracone.

To review, this image shows the various labeling for each tooth, traditionally primitive mammals had cheek teeth with bumpy, distinguished cusps between each tooth. These types of teeth are described as bunodonts. Bunodonts  are commonly seen in carnivores, however the diet does not necessarily have to be carnivorous to have bunodont styled teeth. Humans are an example of bunodont teeth that do not possess a carnivorous only diet.

 

 

The other kind of cheek teeth are ones with less distinguished cusps between each tooth, the cusps separating teeth are called lophs, which is why these teeth are described as lophodonts. Horses, rodents, and elephants are common lophodonts, to name a few. Lophodont teeth are made to grind at a surface such as roots or other types of plant matter. 

 

(sorry for low quality, but had to compress) 

 

 

So we've gone over the primary cusps, the primary cusps are only formed in the middle portion of the tooth, the shelf surrounding the middle is called the cingulum, on the cingulum, more cusps form, these are called secondary cusps. The three primary cusps will ALWAYS form in mammalian cheek teeth, however the secondary cusps differ between species. The only exception to this rule is many insectivorous mammals have a fourth primary cusp called the hypocone. While technically the hypoconid cusp is a secondary cusp, since it is regularly seen in a large group of mammals, I call it a 'fourth primary' because it acts as one in many different animals. 

 

Varying primary and secondary cusps are set in stone, there are also 'cross breeds' between the two. For example, a "paraconule" would be a mix between a paracone and a metacone. 

With this said, making a key to abbreviations of cusps in particular would be a very lengthy process, so we will have to move on to the next subject. This is a very active and complex field of study so bare in mind this is only just a glimpse of what there is to offer; the basics, I digress.

 

Along with the cingulum there is another 'ridge' in the tooth called the stylar shelf, this is found on the side of the tooth, like in the image below.

 

 

Along this shelf you will find a multitude of 'styles' such as parastyle, while I'd love to list the styles individually you might be a fossil yourself by the time I would finish! 

 

You may want to read this a couple times to understand it if you are hearing about this for the first time, as it took me many times to understand the concepts of teeth and dental terminology. I hope this was informative as its very helpful to know what a model or diagram is actually saying, it can be very tough to understand at times, but I hope this helps!

 

 

Image Source(s):

http://palaeos.com/vertebrates/mammaliformes/mammaliformes3.html

https://www.fossilhunters.xyz/age-of-mammals/boreosphenida.html

http://www.geocities.ws/chunniemonster/dental_formula.html

https://inside.ucumberlands.edu/academics/biology/faculty/kuss/courses/Digestive system/

http://resizing.info/openphoto.php?img=http://donsmaps.com/images7/dentaldiagram.jpg (May not be orginal source, I couldn't find orginal)

http://www.siamese-cat-breeder.co.uk/dental-care-for-cats/

https://en.wikipedia.org/wiki/Molar_(tooth)#/media/File:Carnassials.jpg

http://journals.openedition.org/paleo/2861

(Couldn't find Mammal Characteristics Diagram Image)

http://animaldiversity.org/collections/mammal_anatomy/tooth_diversity/

 

Edited February 23, 2018 by RyanDye
Revisions in info.

[izak_]

Just wondering where you got the last pic from?

[Fossildude19]

Ryan,

Nice post, however,  you should really state the source of your pictures.

[Harry Pristis]

 

 

Good effort, Ryandye.  I hope you'll continue to work on this project . . . more research, especially about canine teeth.  Be certain that the illustrations support the text.  Clear up the misspellings and the faulty verb agreements.  It's best to work from an outline to avoid the "Oh, I forgot to mention . . . ."  interjections.  This essay could be potentially useful with some work.   

[jpc]

I agree with Harry, but let me make some corrections.  (Yes, I took a mammalian paleontology class many years ago, and I still use these terms in my work).

 

Where did you read that there is no lower canine in mammals?  Yes there is.  Some mammals have no canines (rodents, rabbits), but in general the lower canine exists, even in you and me, but have a look at your cat or dog at home.  

 

This line is unclear:

"If I said I3 I would be referring to the top incisors on the 3rd row from left to right, if I said i3 it would be the same thing, except it would be on the lower jaw rather than the top jaw."  The numbers are labeled from the centerline headed towards the jaw hinge, I3 is the third incisor from the centerline... nothing to do with left and right because that changes if you are looking at the left or right jaw/maxilla.  Your next paragraph also uses the left and right model, so it also needs clarification.  The human M3 (and m3) is the wisdom tooth.  the two molars in front of it are M/m2 and M/m1.  Mammalian dental formulas are generally written like this 

 

(These examples are of 'unusual' dental formulas).  

The upper numbers are maxilla teeth, the bottom are lower jaws (dentary).  Incisors are on the left, canines next, premolars, then molars.  Last total number of teeth.  

 

Bunodont means the cusps are rounded, not pointy, as opposed to varied that you said. 

 

The section on cusps is a good start.  The Protocone, Paracone and Metacone and Hypocone are all part of the upper teeth.  You mentioned the  Hypoconid when talking about uppers, but this cusp is part of the lower molars.  These terms are best suited for primitive Therian mammals (placentals like us and marsupials like the opossum) teeth patterns, but when you get into elephants, rodents and some others, the terms all go to lophs.  And in more primitive mammals, they terms are not quite standardized.    

 

As I said, I do use these terms at work, and in my own private prep work, but I also keep a printout that labels all the cusps on my wall.  I do not have these terms memorized, except protocone.

 

Not that I am trying to criticize, but I thought that if someone does want to know all this, it should be clear and free of mistakes.  

 

[Miocene_Mason]

This is all a bit technically for me at the moment, but I will say that (and you probably know this as you were only saying “suppose that”) all old world monkeys (including apes, hominins and humans) have the dental pattern 2-1-2-3 over 2-1-2-3. Also I have a question for anyone here willing to answer, what is the difference)if there is one) between lophodonts and hyspholodonts?

[RyanDye]

14 hours ago, Foozil said:

Just wondering where you got the last pic from?

 

9 hours ago, Fossildude19 said:

Ryan,

Nice post, however,  you should really state the source of your pictures.

 

2 hours ago, Harry Pristis said:

 

 

Good effort, Ryandye.  I hope you'll continue to work on this project . . . more research, especially about canine teeth.  Be certain that the illustrations support the text.  Clear up the misspellings and the faulty verb agreements.  It's best to work from an outline to avoid the "Oh, I forgot to mention . . . ."  interjections.  This essay could be potentially useful with some work.   

 

1 hour ago, jpc said:

I agree with Harry, but let me make some corrections.  (Yes, I took a mammalian paleontology class many years ago, and I still use these terms in my work).

 

Where did you read that there is no lower canine in mammals?  Yes there is.  Some mammals have no canines (rodents, rabbits), but in general the lower canine exists, even in you and me, but have a look at your cat or dog at home.  

 

This line is unclear:

"If I said I3 I would be referring to the top incisors on the 3rd row from left to right, if I said i3 it would be the same thing, except it would be on the lower jaw rather than the top jaw."  The numbers are labeled from the centerline headed towards the jaw hinge, I3 is the third incisor from the centerline... nothing to do with left and right because that changes if you are looking at the left or right jaw/maxilla.  Your next paragraph also uses the left and right model, so it also needs clarification.  The human M3 (and m3) is the wisdom tooth.  the two molars in front of it are M/m2 and M/m1.  Mammalian dental formulas are generally written like this 

 

 

17 minutes ago, WhodamanHD said:

This is all a bit technically for me at the moment, but I will say that (and you probably know this as you were only saying “suppose that”) all old world monkeys (including apes, hominins and humans) have the dental pattern 2-1-2-3 over 2-1-2-3. Also I have a question for anyone here willing to answer, what is the difference)if there is one) between lophodonts and hyspholodonts?

(These examples are of 'unusual' dental formulas).  

The upper numbers are maxilla teeth, the bottom are lower jaws (dentary).  Incisors are on the left, canines next, premolars, then molars.  Last total number of teeth.  

 

Bunodont means the cusps are rounded, not pointy, as opposed to varied that you said. 

 

The section on cusps is a good start.  The Protocone, Paracone and Metacone and Hypocone are all part of the upper teeth.  You mentioned the  Hypoconid when talking about uppers, but this cusp is part of the lower molars.  These terms are best suited for primitive Therian mammals (placentals like us and marsupials like the opossum) teeth patterns, but when you get into elephants, rodents and some others, the terms all go to lophs.  And in more primitive mammals, they terms are not quite standardized.    

 

As I said, I do use these terms at work, and in my own private prep work, but I also keep a printout that labels all the cusps on my wall.  I do not have these terms memorized, except protocone.

 

Not that I am trying to criticize, but I thought that if someone does want to know all this, it should be clear and free of mistakes.  

 

http://animaldiversity.org/collections/mammal_anatomy/tooth_diversity/ (For @Foozil)

 

@Fossildude19 Yes, I will try and go find where I found the pictures for this post, if I can't I will make sure to do so in the future. 

 

@Harry Pristis Unfortunately, I couldn't write the entire essay at once, so my thoughts were a little organised when I returned to writing it. I'll make an outline beforehand next time so I don't lose my train of thought, which would avoid 'forgot to mentions'. As for grammatical errors, I will do my best to recheck over, I think the more I write the less and less I will make these errors. I was really having a hard time finding pictures that I could compress that showed exactly what I wanted so that also had to do with some of the pictures not matching up to what I was saying.

 

@jpc I apologize for the mistakes, undoubtedly you are more well informed on the subject than me, my intention was to explain it more than help people memorize the terms. However it would not be helpful for me to leave these errors in the essay. I will definitely edit and take the recommendations you gave me, I completely understand what your saying and I don't take it personally; more rather, I take it as very helpful! With the bunodont and lophodont, I was more or less trying to say the CUSPS on the tooth were varied or distinguishable more so than the lophodont as the lophs are more 'blurred'. With the human example was just an example of how the number of the tooth isn't necessarily the order the tooth is in, however it would of been clearer had I used an actual example; I will definitely revise that. Thank you for your comment I'm glad to take constructive thoughts since this is one of my first full out essays. 

 

@WhodamanHD Yes I was just saying a "suppose that", but it would of been more valid with an accurate example, which I will revise into a more perfect paper. Unfortunately I cannot answer your question, more than likely it has a different arrangement of cusps. 

[jpc]

I am glad you are open to suggestions and corrections.  Some folks get sensitive about this, and I knew I maybe hitting a nerve.  Glad it didn't. No need to apologize.  And as a last grammar correction.... 'would of' should be 'would have'.  

 

I am still curious as to where you found that mammals have no lower canine...  

 

[RyanDye]

1 hour ago, jpc said:

I am glad you are open to suggestions and corrections.  Some folks get sensitive about this, and I knew I maybe hitting a nerve.  Glad it didn't. No need to apologize.  And as a last grammar correction.... 'would of' should be 'would have'.  

 

I am still curious as to where you found that mammals have no lower canine...  

 

Nowhere, it was just a misunderstanding from a diagram that I made

[RyanDye]

Just wanted to tell everyone that this post has been edited!