Hinoshima formation, Santonian, Japan - Fish tooth?

[David in Japan]

Hi TFF friends,

 

it's been a while. I hope you're all fine.

 

This week, I explored my favorite place in Kumamoto prefecture (trip report coming these week-end) and found the following fossil.

First time I saw such fossil from this location.

I have browsed the literature related to this location but I unfortunately didn't find any clues about what this fossil could be.

I suspect this could be some kind of fish tooth. In the all the papers I read about this location, I found some mentions of fish material found there but no description or further information.

 

I was wondering if this could be some kind of Pycnodont tooth, the general shape matches and we can see in cross section the kind of fold where the root is missing. However the regular grooves on the surface makes me doubt about my guess a little bit as I think that Pycnodont tooth are "smooth" .

 

If any one has a guess about what it could be, do not hesitate to throw it in the comments. Any help is welcome.

 

 

Size: 8mm by 3mm

Himenoura Formation (lower)

Late Cretaceous (Santonian)

Kumamoto prefecture, Japan

 

 

 

 

 

 

 

 

 

 

 

 

[Tidgy's Dad]

Hi, David.

My first thought is praying mantis egg case. 

[Rockwood]

The texture looks like. . . 

@Carl Maybe it's a coprolite ? 

[David in Japan]

2 hours ago, Tidgy's Dad said:

Hi, David.

My first thought is praying mantis egg case. 

Ootheca?

Your right it looks a little bit alike.

When i fist found it i thought it was a satsuma cockroach before realising it was a fossil.

 

 

 

 

 

[David in Japan]

2 hours ago, Rockwood said:

The texture looks like. . . 

@Carl Maybe it's a coprolite ? 

It is really smooth except the fact it has those grooves. The grooves are spaced very regularly.  It does not look like a bivalve.

 

I put in red the cross section.

 

 

I found in the past coprolites from this very location, they are usually

phosphatised and jet-black.

 

[caterpillar]

Maybe ostracod

[Rockwood]

13 minutes ago, David in Japan said:

found in the past coprolites from

It brings to my mind coprolites that I collected at Blue Beach in Nova Scotia Canada. The surface of them is smooth, the texture is too though. Those are almost the texture of modern excrement.

Maybe Carl is back to his break routine at the museum. He may be along soon.

 

[Carl]

4 hours ago, Rockwood said:

The texture looks like. . . 

@Carl Maybe it's a coprolite ? 

I'm thinking not: the lines are a bit too regular here.

[Rockwood]

There you have it, straight from. Well we won't go there. Carl's a good. 

 

[David in Japan]

2 hours ago, Rockwood said:

There you have it, straight from. Well we won't go there. Carl's a good. 

 

 

2 hours ago, Carl said:

I'm thinking not: the lines are a bit too regular here.

 

4 hours ago, caterpillar said:

Maybe ostracod

 

Yes, the pattern is too regular for something going straight out of an ...

Thank you. Reducing the possibilities is also a good thing.

 

Ostracod could be a good push. Would match the marine environment, a saw they can grow up to 5 cm so the size is in the good bracket. Still the pattern of the grooves is intriguing. I have never seen an ostracod fossil and i do not know anything about their ontogeny but shouldn t we see growth ring of some sort on the outside of the shell,

 a little bit like in bivalves?

 

Sorry, it is a stupid question but i do not know ostracod dev stages.

 

[Tidgy's Dad]

Newbie - Member Introductions - The Fossil Forum

[David in Japan]

5 hours ago, Tidgy's Dad said:

Newbie - Member Introductions - The Fossil Forum

Praying mantis ootheca ard really weird isn t it?

 

Have a lot in my garden, the cool thing is that it start like a foam and then harden.

[caterpillar]

On 11/5/2021 at 4:11 PM, David in Japan said:

Sorry, it is a stupid question but i do not know ostracod dev stages.

 

Ostracods exist from ordovician (maybe cambrian) to recent

[David in Japan]

On 11/5/2021 at 7:53 PM, caterpillar said:

Maybe ostracod

 

Thank you for the push. I contacted a friend working at Ehime University and he agreed this might be an ostracod.

 

Thank you all.