Hinoshima formation, Cretaceous (Santonian), Japan

[David in Japan]

2 weeks ago, I surface hunted fossils at my favorite spot in Kumamoto Prefecture, Japan.

 

It was a very hot day of November and as I was alone and had plenty of time, I have been able to return to several spots (same formation though) I do not often go to.

As usual, as the places I went are part of a national park, you are not allowed to take fossils directly from the formation however you can still take back rocks that felt from the cliff or which lies on the beach.

 

I first stopped at Kojima's camp site. Kojima is a very small island (the name Kojima means small island in Japanese) that was transformed in a small camp site.

 

 

Before being transformed into a touristic spot, the place yielded lots of late cretaceous sharks teeth and heteromorphs ammonite unfortunately, the rich fossil layers has been covered in concrete and it is hard now to find teeth there. I walked around the island and despite the fact I didn’t find any tooth, I found a bunch of Inoceramus (Platyceramus) higoensis and fossils of Sea Urchins

 

 

however I wasn’t as lucky as my new little friend as didn’t bring anything back from from this specific location.

 

[David in Japan]

Next stop was at my usual prospecting location. It’s been a while since last time (almost 1 year) and I wow, I had changed a lot. Waves made what they do the best and eroded a lot the formation, discovering part of the formation I never explored and covering with sand the most promising places.

 

I found quite a lot of ammonites (Gaudryceras tenuilratum and Polyptychoceras Haradai), Inoceramus and bivalves stranded on the beach but because of the poor preservation state I left them there. Kids often looks for fossils there and I guess they would be happy to find them.

 

 

[David in Japan]

As I walked back to the car thinking It had been a sweet day and even if I didn’t find anything interesting, I enjoyed a very nice walk , I found 3 tiny treasure poking out of the same rock.

 

First: what I thought to be some kind of fish tooth and that proved to be (thanks to your help) an Ostracod.

 

 

 

Second: my first shark vertebra. It is a tiny one but I was very excited!

 

 

 

Third: this very tiny shark tooth found just few centimeters from the vertebra. Before preparation I thought it was a small Cretalamna tooth which are very common in this part of the formation however after cleaning I am more inclined to think that it is a small Protolamna sp. tooth.  Protolamna teeth are not as common as Cretalamna’s one but Protolamna sokolovi has been described from that location.

The tooth (2-3mm high) is almost complete and some feeding wear can be seen on the main cusp the cusplet. I think that this tooth might be a juvenile tooth as it has 2 pairs of cusplets, fainted fold on the main cusp and cusplets on the lingual surface and very deep fold on the labial surface (from the base to the half of the main cusp). That’s one of the coolest tooth I found there with Chlamydoselacus tooth).

 

lingual view:

 

 

 

Labial view:

 

 

[Fossildude19]

I took the liberty of brightening your shark vertebra.

Nice finds!

 

[David in Japan]

8 hours ago, Fossildude19 said:

I took the liberty of brightening your shark vertebra.

Nice finds!

 

Thank you, if anybody wants more picture from different angles, feel free to ask.

[Jared C]

very cool, seeing Japanese cretaceous stuff is a nice break from all the texas cretaceous posts (...even though I make so many of them myself)

[David in Japan]

Worked a little bit on the tooth today.

Here is a better photo. I think it is a Protolamna sokolovi.

 

[minnbuckeye]

On 11/17/2021 at 1:41 AM, David in Japan said:

Is this the shadow of a merman?

 

[David in Japan]

On 11/18/2021 at 4:06 PM, Jared C said:

very cool, seeing Japanese cretaceous stuff is a nice break from all the texas cretaceous posts (...even though I make so many of them myself)

I enjoy Texas cretaceous posts, in awe when I see Mosasaurus material.

On 11/18/2021 at 11:15 PM, minnbuckeye said:

Is this the shadow of a merman?

 

Even in my wildest dream...

I have a six pack too but it is the drinkable one