Tusk? Really no idea..

[JBar]

Hello one and all!

This unknown fossil was part of a large group of fossils I purchased a few years back. I wondered if anyone might be able to tell me a bit more about this tusk like fossil I have posted as I have limited knowledge of such items.

The fossil measures just about 7" inches long and the weight is 12.5 ounces.

Thank you in advance.

 

 

[Tidgy's Dad]

I see schreger lines, so I think this is a member of the proboscidea. 

 

[JBar]

Tidgy's Dad, thank you.

 

So a Mammoth tusk is a possibility? 

[Thomas.Dodson]

18 minutes ago, JBar said:

Tidgy's Dad, thank you.

 

So a Mammoth tusk is a possibility? 

Certainly a possibility. I'm having difficulty discerning the intersection of schreger lines in this picture but if you're able to see them better yourself you can measure the angles. See the thread below for examples and information. Mammoths have acute angled schreger lines and mastodon have obtuse angled schreger lines. Modern elephants also have obtuse schreger lines.

USFWS also has a guide to ivory that includes mammoth. https://www.fws.gov/lab/ivory_natural.php#elephant

[Shellseeker]

9 hours ago, Thomas.Dodson said:

Certainly a possibility. I'm having difficulty discerning the intersection of schreger lines in this picture but if you're able to see them better yourself you can measure the angles. See the thread below for examples and information. Mammoths have acute angled schreger lines and mastodon have obtuse angled schreger lines. Modern elephants also have obtuse schreger lines.

USFWS also has a guide to ivory that includes mammoth. https://www.fws.gov/lab/ivory_natural.php#elephant

  Great Thread that Thomas has provided.

 

The diagnostic part of a tusk is usually the butt end.  In your case.... about 90 degrees === Mammoth

 

Here is a thread, I posted recently on your same question. Mine also a little over 7 inches is Mastodon or Gomphothere.

http://www.thefossilforum.com/index.php?/topic/114912-rivergods-smiled/&tab=comments#comment-1269195

 

[darrow]

1 hour ago, Shellseeker said:

The diagnostic part of a tusk is usually the butt end.  In your case.... about 90 degrees === Mammoth

 

 

Jack, I think the Schreger angle should be measured in an area further from the center of the tusk…

 

In which case the angles are are distinctly greater than 90 degrees suggesting something other than mammoth.

 

Histogenesis of the Unique Morphology of Proboscidean Ivory, Attila Virag 2012

 

Recent reading on the topic has made me realize these angles are not the diagnostic tool I once thought they were.  At least not without a more methodical approach to measuring them and building a comparative dataset.

 

 

 

 

Virag2012JMOR.pdf SCHREGER LINES, Dinesh Kumar Jha, etal..pdf

[Thomas.Dodson]

3 hours ago, darrow said:

Jack, I think the Schreger angle should be measured in an area further from the center of the tusk…

 

 

Far from an expert but from what I've read this seems to be the case as the outer and inner schreger angles differ quite a bit.

 

Due to large variation in the angles it seems an average is much better than relying on a single intersection. From the USFWS source: "Because specimens from both extinct and extant sources may present angles between 90 degrees and 115 degrees in the outer Schreger pattern area, the differentiation of mammoth from elephant ivory should never be based upon single angle measurements when the angles fall in this range."

"When averages are used to represent the angles in the individual samples, a clear separation between extinct and extant proboscideans is observed. All the elephant samples had averages above 100 degrees, and all the extinct proboscideans had angle averages below 100 degrees."

 

I am curious as to what their sample size is. I'm guessing the second paragraph is better said as extinct proboscideans=mammoth since I thought mastodon had angles similar to modern elephants.

 

[PrehistoricWonders]

Mammoth or Mastodon tusk. Nice buy!!!

[JBar]

Had not checked in for some time but am now getting caught up.

 

I wanted to thank everyone who shared their knowledge and expertise with me.

 

I so appreciate your help!

[darrow]

On 5/9/2021 at 1:05 PM, Thomas.Dodson said:

Due to large variation in the angles it seems an average is much better than relying on a single intersection. From the USFWS source: "Because specimens from both extinct and extant sources may present angles between 90 degrees and 115 degrees in the outer Schreger pattern area, the differentiation of mammoth from elephant ivory should never be based upon single angle measurements when the angles fall in this range."

"When averages are used to represent the angles in the individual samples, a clear separation between extinct and extant proboscideans is observed. All the elephant samples had averages above 100 degrees, and all the extinct proboscideans had angle averages below 100 degrees."

 

I am curious as to what their sample size is.

Excellent question! 

 

For the "averages" method to be a reliable (repeatable & reproducible) there must be a clearly defined protocol controlling not only the number of samples in the average but also from where in the cross-section of the tusk each sample is to be taken.  Without such controls the “average” could easily be skewed with intention to make a specimen appear to be what it is not.