Shark Tooth Identification Help

[HunterMeg]

Hi,

 

I recently bought this tooth from a friend, but I am uncertain which species it belongs to.  The root is very thin with great white characteristics, but the lack of serrations on the blade is more like a mako.  
 

My best guess is that it is a Giant White Shark (Charcharodon Plicatitis).  It measure 2.75 inches.

 

The last 2 photos show the tooth in comparison to a Great White tooth on the right side and a Mako Shark tooth on the left side of the tooth in question.

 

What do you believe it is?  

Thank you for helping me out.

[Praefectus]

The left and middle tooth are both the same species. I call them Cosmopolitodus hastalis, but I believe that name is outdated. The current name is Carcharodon hastalis (I think). They are informally referred to as either the "Giant Mako" or "Giant White Shark."

[caldigger]

Thats a "big boy"!  I agree with C. hastalis.

[Macrophyseter]

Kent and Ward (2018) defines C. plicatilis as being a Pliocene species characterized by teeth with broad, triangular, and unserrated crowns with rectilinear "squared-off" roots. This means that differentiating between C. plicatilis and broad-form C. hastalis would be based on primarily root structure and age. That being said, the far left tooth shows more rounded roots and is comparable with the broad-form C. hastalis specimen CMM-V-245 as illustrated in the paper, which the authors stated were not from C. plicatilis due to such rounded roots. The middle tooth cannot really be determined by the root as it is worn down, but if it is Miocene, it's likely C. hastalis and possibly C. plicatilis if it's Pliocene. The far right tooth is C. carcharias due to the presence of serrations.

[HunterMeg]

Thank you to everyone who provided feedback on my question! 

It is a great tooth no matter what name it is called.

[hemipristis]

12 hours ago, Macrophyseter said:

Kent and Ward (2018) defines C. plicatilis as being a Pliocene species characterized by teeth with broad, triangular, and unserrated crowns with rectilinear "squared-off" roots. This means that differentiating between C. plicatilis and broad-form C. hastalis would be based on primarily root structure and age. 

Begs the question why not stick with C. xiphodon. 

[Macrophyseter]

10 minutes ago, hemipristis said:

Begs the question why not stick with C. xiphodon. 

This is because it was declared a nomen dubium as the locality of the syntypes are forgotten, rendering the taxon unreliable (Ward and Bonavi, 2001). However, Agassiz (the guy who first described the species) did erect different taxons for what was essentially the same species in many cases; in the case for C. xiphodon, Agassiz erected another taxon C. plicatilis from a tooth of the same species as the former C. xiphodon. Since C. plicatilis is currently a valid taxon, the most logical thing to do was to simply "transfer" the species represented by the former C. xiphodon into it. (Cione et al., 2012)

[Praefectus]

@Macrophyseter

What is a C. plicatilis and where does it fall in the mako to white shark evolutionary line? I thought C. xiphodon and C. plicatilis were synonymous with C. hastalis (broad form). 

[Macrophyseter]

28 minutes ago, Praefectus said:

What is a C. plicatilis and where does it fall in the mako to white shark evolutionary line? I thought C. xiphodon and C. plicatilis were synonymous with C. hastalis (broad form). 

As implied above, C. plicatilis is the Pliocene representative of broad, triangular, and unserrated species of Carcharodon. Newer studies like Kent and Ward (2018) suggest that it is most likely the final culmination of the unserrated Carcharodon lineage (as in broad-form C. hastalis evolved into C. plicatilis by the Pliocene after the "breakaway" of C. hubbelli/carcharias). As far as I know, the synonymity thing was brought up by Ehret et al. (2012), which reasoned the possibility of sexual dimorphism or ontogenetic differences as the rationale for synonymizing the fossils represented by C. xiphodon with C. hastalis. However, this has been criticized by a number of newer studies such as Kent and Ward (2018), who claim that Ehret et al.'s rationale is overly conservative and ignores a number of important morphological and stratigraphic data that supports the existence of a distinct species. Whether you agree to this or not or consider this just another battle in the lumper vs. splitter debate is up to your rationale, but for those who consider C. plicatilis a distinct species, this is basically what it is.

[Praefectus]

7 hours ago, Macrophyseter said:

As implied above, C. plicatilis is the Pliocene representative of broad, triangular, and unserrated species of Carcharodon. Newer studies like Kent and Ward (2018) suggest that it is most likely the final culmination of the unserrated Carcharodon lineage (as in broad-form C. hastalis evolved into C. plicatilis by the Pliocene after the "breakaway" of C. hubbelli/carcharias). As far as I know, the synonymity thing was brought up by Ehret et al. (2012), which reasoned the possibility of sexual dimorphism or ontogenetic differences as the rationale for synonymizing the fossils represented by C. xiphodon with C. hastalis. However, this has been criticized by a number of newer studies such as Kent and Ward (2018), who claim that Ehret et al.'s rationale is overly conservative and ignores a number of important morphological and stratigraphic data that supports the existence of a distinct species. Whether you agree to this or not or consider this just another battle in the lumper vs. splitter debate is up to your rationale, but for those who consider C. plicatilis a distinct species, this is basically what it is.

Very interesting. Thank you for the thorough answer.