Bourlette help

[Tg2031]

Can someone please explain the bourlette or give a source ( reliable) that explains it?

 

I feel I have a general understanding of what people are referring to and it appears obvious to me in pictures.

 

 However teeth that aren’t “ Meg teeth” sometimes have what I think looks like a shadow line like eyeliner ( I am a woman, if anyone can visualize what I mean here). This would be a feature I only see in a small fraction of teeth I find.  I am no great fossil hunter but I have no problem walking a beach and finding many, many teeth.  I am accustomed to looking at teeth. Likely hundreds a summer-sometimes in a day. Mostly very small but I am not a novice at shark toothing.  

 

Can someone please explain?

I specifically want information on this topic and microscopic comparison.

 I have recently discovered on my own that fossilized shark enamel looks like crazy silver hair or fiber under magnification.

 Can anyone help me find more information related to ID?

 

A lot of snarge is so worn off the beach.  I would appreciate some insight.  I understand a lot of people dive etc to find huge full specimens.  

What about us jack legs who are just curious about what we are looking at?  Thanks so so much in advance! 
tg

[DPS Ammonite]

I found this:

 

https://www.uky.edu/KGS/fossils/fossil-month-01-2017-megalodon.php#:~:text=The border between the crown,the bourlette or dental band.

Edited August 29 by DPS Ammonite

[Tg2031]

Thank you!  I am clicking the link as I type my thanks

[Tg2031]

‘Anyone else?

[Randyw]

The proper name for the bourlette is the dental band or collum. About 1/2 way down the following entree it talks about the bourlette or dental band.

 

It’s from https://depositsmag.com/2021/07/14/talking-sharks-teeth/amp/

 

I hope it works. thank you @DPS Ammonite for reminding me and helping me provide the link.

 

 

"The morphological function of the roots of lower anterior teeth of the Great White shark, like in Megalodon and all other Otodontidae, is to penetrate and stop the prey from escaping. The pressure of the tearing forces comes from the inner side (lingual) outwards. The roots lobes work like supports to keep the tooth to the jaw. Like a physical lever, the longer the tooth, the less energy needs to be used and vice versa.

 

Fig. 7. Carcharodon carcharias.

 

 

Cappetta (1987) described the different types of junction between root and crown in terms of “Dental characters and terminology” that “the neck (= collar or lingual furrow) [is] especially distinct on the lingual face of the tooth”. Other names for the large transitional area between the crown and root are ‘collum’ (Latin, translated: neck) and ‘bourlette’ (Kent, 1994). Welton and Farish (1993) describe a ‘dental band’ as being “a narrow, smooth, enameloid-free band at the crown-root junction on the labial or lingual surfaces or completely encircling the tooth”.

 

 

Fig. 5. Carcharocles auriculatus.

 

 

Fig.6. Carcharocles auriculatus.

 

 

In Megalodon, like in all other giant-toothed sharks (Otodontidae), the dental band is large and chevron-shaped. It often bears a thin dark ‘enameloid’ wash and on the lingual side of the tooth only and can therefore be called ‘collum’. The teeth of a Great White shark, like its ancestor Makos (Isurus hastalis and I. praecursor), have none or, at most, a weak and narrow transitional area, which fits the description of the “dental band”.

 

 

Fig. 3. Otodus obliquus.

Dental band

This ‘collum’, in Megalodon, is apparently additional collagenous tissue, and apparently helps fix the tooth to the jaw, for the same reason mentioned above (tearing forces). The higher the starting point is towards the crown (physical lever), the stronger are the retaining forces. The function of the ‘dental band’ for teeth of the Great White shark, and its ancestor, the big-toothed Mako (Isurus hastalis), is apparently of less relevance and without any different crown shapes.

The lingual face of the upper anterior teeth of all Otodontidaeis strongly convex which can clearly be seen in cross section. The tooth crowns of the Great White shark, and his ancestor the big-toothed Mako (Isurus hastalis), are not convex, but flat in cross section."

 

 

 

[Randyw]

I find that most of our members are just trying to be helpfull…..

Edited August 29 by Randyw