Show me your six and seven gill shark teeth

[Coco]

My colleague had found a small tooth there that could belong to the Notorynchus, I don't know if she found the exact identification.

 

Coco

[fossilsonwheels]

On 10/19/2020 at 3:15 PM, siteseer said:

Here's is a tooth of the aptly named Notorynchus aptiensis because it comes from a Aptian-age (Early Cretaceous) site at Carniol, France.  It appears to be the earliest species of the genus.  This tooth is 11mm long (American rule in the photo).

 

I have an older hexanchid tooth, Eonotidanus, but I got a photo of this first because the Jurassic tooth is a little smaller.  If I couldn't get a decent shot of this N. aptiensis tooth, I would have no chance of getting one of the Eonotidanus.

 

Jess 

Oh man that is an AWESOME tooth my friend. I doubt I will see another one of those. Not only is it a rare bird, it is a pretty one too. Love the color on it. France produces some really amazing shark teeth. 

 

The photograph is excellent by the way lol

[fossilsonwheels]

On 10/19/2020 at 2:00 AM, siteseer said:

Here's an oddball tooth that I'm reasonably sure is a Hexanchus symphyseal.  I bought it about twenty years ago as part of a lot of small teeth from Copiapo , near Caldera, Atacama Desert, Chile.  Everyone was chasing megs, great whites, and sixgills and I was too but I looked for anyone with smaller teeth or micros as well.  A few dealers had them later, but not long after that, the Chilean government outlawed the export of fossils.

 

I've seen the normal range of Hexanchus teeth from the deposit and other sites, and I've seen some weird teeth, but this one is weird in a different way.  As you can see, it has just a main cusp with no real hint of additional cusps.  It's just 11mm wide and about 9mm high (you can see it next to an American ruler in the photos).  On the labial face it has an odd ridge of enameloid protruding outward - perhaps a minor pathology.  Because of the small size at that position for an essentially modern Hexanchus tooth.  I assume this is a juvenile.  The labial view came out clearer but I'm adding the lingual in case anyone is curious.

 

Jess

That is such a cool little tooth. I am partial to the small teeth anyway so it’s really nice to see a little one from Chile and quite unique 

[fossilsonwheels]

Hexanchus microdon

Paleocene

Ouled Abdoun

Morocco

 

 

[fossilsonwheels]

Hexanchus agasszi

Eocene

London Clay

Isle of Sheppey

UK

 

 

[fossilsonwheels]

@siteseer sent us these very small 6 Gill lowers. Jess has been a great friend and huge help to us in so many ways. Cool teeth from a cool location 

 

Hexanchus agasszi

 Eocene

Santee Limestone

Harleyville South Carolina

[fossilsonwheels]

Hexanchus sp

Miocene

Lee Creek

North Carolina 

 

We just got this beauty today from @Troodon . I am really happy to have this one. I know they are rare in the fauna and this one is a fantastic example. Super grateful to Frank  

[siteseer]

On 10/9/2020 at 9:04 PM, fossilsonwheels said:

Fantastic tooth Will. Thank you for sharing it with us. Great addition to the thread. 

 

Yes, partials are what they find of Notidanodon at Herne Bay.  That is one of the best ones, and maybe the best one, I've seen from there.  Great specimen.

 

Jess

[siteseer]

The Hexanchiformes is perhaps the oldest of the modern shark orders, appearing in the early Jurassic.  At the time the continents, which had been clustered together after drifting toward each other across the Paleozoic Era, were starting to separate again.  Over millions of years, one extensive coastline slowly became several different ones on top of all the islands that existed.  It all added up to new environments to be exploited among worldwide, tropical conditions.

 

Like other animal groups the hexanchiforms started small.  At the time hybodonts were the dominant shark group.  There were active hunters that were the tigers and great whites of their day, smaller forms that were lower level predators like today's reef sharks and there were shell-crushing forms some of which were at least as large as the active hunters.  They occupied the niche that rays took over later.  In the early Jurassic there were no rays yet.  All those niches belonged to hybodonts.  Small, odd sharks like Hexanchus lived on the edges of that world.  Other odd sharks like the earliest carpet sharks lived around this time and still others (angel sharks, horn sharks, and lamniform sharks) would be present by the end of the period.  As these sharks and others diversified across the rest of the Mesozoic Era, hybodonts declined in number and variety.

 

Eonotidanus was an early hexanchiform and belongs to the family still living today, Hexanchidae.  As far as I know, It is known only from European sites.  The tooth shown (just over 7mm wide) is the oldest hexanchid in my collection and a rare find generously traded to me by an old friend.

 

Eonotidanus sp.

Late Jurassic

Kimmeridgian age

Holderbank, Switzerland

 

 

[fossilsonwheels]

6 hours ago, siteseer said:

The Hexanchiformes is perhaps the oldest of the modern shark orders, appearing in the early Jurassic.  At the time the continents, which had been clustered together after drifting toward each other across the Paleozoic Era, were starting to separate again.  Over millions of years, one extensive coastline slowly became several different ones on top of all the islands that existed.  It all added up to new environments to be exploited among worldwide, tropical conditions.

 

Like other animal groups the hexanchiforms started small.  At the time hybodonts were the dominant shark group.  There were active hunters that were the tigers and great whites of their day, smaller forms that were lower level predators like today's reef sharks and there were shell-crushing forms some of which were at least as large as the active hunters.  They occupied the niche that rays took over later.  In the early Jurassic there were no rays yet.  All those niches belonged to hybodonts.  Small, odd sharks like Hexanchus lived on the edges of that world.  Other odd sharks like the earliest carpet sharks lived around this time and still others (angel sharks, horn sharks, and lamniform sharks) would be present by the end of the period.  As these sharks and others diversified across the rest of the Mesozoic Era, hybodonts declined in number and variety.

 

Eonotidanus was an early hexanchiform and belongs to the family still living today, Hexanchidae.  As far as I know, It is known only from European sites.  The tooth shown (just over 7mm wide) is the oldest hexanchid in my collection and a rare find generously traded to me by an old friend.

 

Eonotidanus sp.

Late Jurassic

Kimmeridgian age

Holderbank, Switzerland

 

 

Oh that is just awesome Jess. I have a fondness for Jurassic teeth in general but THAT is the dream tooth. I have seen a couple on TFF and in internet searches from Germany. I can not recall seeing one from Switzerland though which just adds to the coolness.

 

One of the things that make Cow Sharks so interesting as an educator is how far back they go and the amazing adaptability in takes for any critter to last as long as they have. Theirs is an amazing story and that is one amazing tooth.

[fossilsonwheels]

Some German Notorhynchus teeth. These came from @siteseer. I really like these. I am fond of German shark teeth. 

 

Notorhynchus primigenius

Oligocene

Rheinhesen

Weinheim Germany 

[fossilsonwheels]

Another German tooth from @siteseer. Jess sold us this little beauty. Different location and our first Cow Shark symphseal tooth !! I am so happy to have knocked that off the want list. 

 

Notorhynchus primigenius

Oligocene

Neumuhle near Alzey

Rheinlandpfalz Germany 

[siteseer]

I was going to post a couple of more photos about two weeks ago but I recalled hearing about a new hexanchid genus erected back in 2011.  I didn't have the article that described the genus, Gladioserratus, until a few days ago.

 

Back in the late 80's when I started collecting fossils, the world of hexanchids was rather clear in that they appeared in the Jurassic with Hexanchus, Notidanoides, Paranotidanus and Eonotidanus being the known genera from that time.  The Cretaceous was populated by Hexanchus, Notorynchus, and Notidanodon.  

 

Since the late 80's, the Mesozoic hexanchids have been re-evaluated by a few researchers.  Eonotidanus and Paranotidanus are now considered invalid genera although the latter remains at least in question by some.  I'd need to read up more but it appears the Eonotidanus specimen I showed may not be complete enough to assign to a genus.  I have an even more fragmentary specimen too.

 

Teeth that that have been identified as Notorynchus aptiensis have been referred to the genus Gladioserratus and Notorynchus is no longer considered to have been present in the Cretaceous at all.  Its earliest known occurrence is now the early Eocene with N. serratissimus.  Gladioserratus bears a lower root with a straight mesial edge.  Adult teeth have regular mesial edge serrations while those of Notorynchus gradually increase in size to the first cusp.

 

At least one species that has been assigned to Notidanodon may end up in a new genus in the future.  There seem to have been different species in the Cretaceous than in the Paleocene.

 

The species Hexanchus microdon appears to be valid for only Cretaceous specimens with H. agassizi for Paleocene and Eocene teeth but that has not been confirmed for all areas.  The numerous specimens collected from the late Cretaceous and early Paleogene of Morocco could provide enough of a sample to draw a conclusion that would confirm or refute that.   

 

The tricky thing about hexanchids is that the teeth are quite fragile so specimens tend to be rare in their known localities and incomplete when you find one.  As was often the case in the 1800's, names were given to partial shark tooth specimens and it took time to sort out the well-supported names from the invalid ones to the extent that they are understood now by researchers.

 

The largest hexanchid of the Cretaceous is still considered to be Notidanodon.  Teeth over an inch and a half have been found all over the world (California, England, eastern Europe, New Zealand) but they are rare finds where they occur.  That puts it in the size range of some of the larger Hexanchus teeth of the late Neogene and modern times.  Notidanodon apparently avoided shallow seas, frequenting deepwater and that was likely why it managed to survive the K/T extinction event.  Hexanchus was still a small shark that likely also frequented deepwater but occasionally ventured into shallow seas as it does today.

 

The tooth shown is:

 

Notidanodon lanceolatus

Early Cretaceous - Albian

Stary Oskol, Russia

1 1/16 inches long (approx. 27 mm)

 

 

[fossilsonwheels]

12 hours ago, siteseer said:

I was going to post a couple of more photos about two weeks ago but I recalled hearing about a new hexanchid genus erected back in 2011.  I didn't have the article that described the genus, Gladioserratus, until a few days ago.

 

Back in the late 80's when I started collecting fossils, the world of hexanchids was rather clear in that they appeared in the Jurassic with Hexanchus, Notidanoides, Paranotidanus and Eonotidanus being the known genera from that time.  The Cretaceous was populated by Hexanchus, Notorynchus, and Notidanodon.  

 

Since the late 80's, the Mesozoic hexanchids have been re-evaluated by a few researchers.  Eonotidanus and Paranotidanus are now considered invalid genera although the latter remains at least in question by some.  I'd need to read up more but it appears the Eonotidanus specimen I showed may not be complete enough to assign to a genus.  I have an even more fragmentary specimen too.

 

Teeth that that have been identified as Notorynchus aptiensis have been referred to the genus Gladioserratus and Notorynchus is no longer considered to have been present in the Cretaceous at all.  Its earliest known occurrence is now the early Eocene with N. serratissimus.  Gladioserratus bears a lower root with a straight mesial edge.  Adult teeth have regular mesial edge serrations while those of Notorynchus which gradually increase in size to the first cusp.

 

At least one species that has been assigned to Notidanodon may end up in a new genus in the future.  There seem to have been different species in the Cretaceous than in the Paleocene.

 

The species Hexanchus microdon appears to be valid for only Cretaceous specimens with H. agassizi for Paleocene and Eocene teeth but that has not been confirmed for all areas.  The numerous specimens collected from the late Cretaceous and early Paleogene of Morocco could provide enough of a sample to draw a conclusion that would confirm or refute that.   

 

The tricky thing about hexanchids is that the teeth are quite fragile so specimens tend to be rare in their known localities and incomplete when you find one.  As was often the case in the 1800's, names were given to partial shark tooth specimens and it took time to sort out the well-supported names from the invalid ones to the extent that they are understood now by researchers.

 

The largest hexanchid of the Cretaceous is still considered to be Notidanodon.  Teeth over an inch and a half have been found all over the world (California, England, eastern Europe, New Zealand) but they are rare finds where they occur.  That puts it in the size range of some of the larger Hexanchus teeth of the late Neogene and modern times.  Notidanodon apparently avoided shallow seas, frequenting deepwater and that was likely why it managed to survive the K/T extinction event.  Hexanchus was still a small shark that likely also frequented deepwater but occasionally ventured into shallow seas as it does today.

 

The tooth shown is:

 

Notidanodon lanceolatus

Early Cretaceous - Albian

Stary Oskol, Russia

1 1/16 inches long (approx. 27 mm)

 

 

Awesome and interesting information as always Jess !! Plus a beautiful Cretaceous tooth from a great location. 

[Chimera]

Hexanchus Agassizi Cappetta, 1976

 

From Aquitaine, France

 

Ypresian

[fossilsonwheels]

1 hour ago, Chimera said:

Hexanchus Agassizi Cappetta, 1976

 

From Aquitaine, France

 

Ypresian

Beautiful tooth and a location I’ve not seen. Thank you for posting that. 

[Chimera]

Thanks Fossilonwheels.

 

 

This basin was deep during the Eocene due to local tectonic activity.

This species is therefore not rare unlike the much shallower Paris basin.

[Chimera]

Another less common species

[fossilsonwheels]

52 minutes ago, Chimera said:

Another less common species

Looks like a Heptranchias

[Chimera]

Need to be confirmed, Heptanchias howellii (Reed, 1946) is mentioned in this area, but i have also think to Weltonia ?

[Coco]

Hi,

 

I don’t think it’s Weltonia because its main cusp isn’t straight, and on your tooth it is.

 

Coco

[fossilsonwheels]

I agree with @Coco. Not Weltonia. 

[Chimera]

Thank you for replies

 

Yes is perfectly true for Weltonia ancistrodon, but with W. burnhamenis is not so clear. For some position the main cusp is almost straight or slightly curved.

 

In Heptranchias (lower teeth) most of lateral cusps have a regular size :

 

https://www.semanticscholar.org/paper/A-study-of-the-sharks-and-rays-from-the-Lillebælt-(-Carlsen-Cuny/0d394a0f1306d1db48c4b54f29e8f6e4a7ad2a3c/figure/16

 

or very irregular as Paraheptranchias repens.

 

For Weltonia lateral cusps have a regular dicreasing size, another link to illustrated my argue :

 

http://www.sheppeyfossils.com/pages/weltonia_burnhamensis.htm

[Coco]

Seeing your last link, I think your tooth looks a lot like the one on the bottom left. This is a species that I did not know about and apparently there is not much information on the web about it.

 

Coco

[Chimera]

that's one of the reason for my doubts about this tooth,

 

if that is the case, it will be the first Weltonia from France

 

Chimera