Massive Miocene Shark Vert

[Doctor Mud]

This is a fossil hunting trip report, but also a mystery story. Why? All will become clear  soon.

 

I made a few trips to the north Canterbury coastline in the last few weeks. The home of the mighty Tumido crabs.

Ive been finding that good concretions are getting harder to find and it takes more effort to find them. You need a good storm to mix things up every now and then.

 

That seems to have happened on one stretch of beach I frequent uncovering 30 crab concretions in a 100 m stretch of coastline. Most are " heart breakers" massive crabs (bigger than any in my collection) but split through the middle.

Strangely mostly only one half is usually there.

 

I did s lot of digging around concretions hoping to find a big guy mostly complete, No luck

What I did find was this;

 

 

an impession (With some bone) of very large (> 5 inches across) shark vert.

It was near the end of the day and the block was huge so I buried it in the sand so I could come back and trim it.

 

I went back 2 days later and - it was gone!

I had marked the location with a pile of rocks (not right on top of it). I had even brought I shovel to look for the rest.

So I looked thoroughly. The tide would have just reached the spot and probably exposed it a bit (it was about the high tide mark) but I was surprised that someone would have hauled it out. There's no evidence for trimming. The tide may have moved it? Although other concretions were in place. More in the next post....

[Doctor Mud]

It was mostly an impression, but I was a bit sad as shark verts are so rare here and its size made me think it could belong to a certain large shark that existed at this time. Meg verts are very rare. 

 

I went back again today, no luck with this bit, but I got lucky. I spent an hour flipping more concretion halves, digging around them and levering them out.

Then I saw it..... I flipped one over and brushed off the sand to reveal half of the actual shark vert. 

No burying this one in the sand! It took me over an hour to trim down the rock to haul it out:

 

 

This bit was about 20 m down the beach from the concretion with the impression. So there must be a bit of movement over time. 

The other bit must still be out there somewhere..., perhaps still buried under the sand? Perhaps it has been collected?

Ill be keeping an eye out for it!!

 

As for the other piece I originally found - its disappearance will remain a mystery.

[cfin1974]

Nice find but what bad luck losing the other piece.

[ynot]

WOW, that is a big shark vert.

Congratulations on finding the actual vert, so much better than the imprint!

 

Tony

[RJB]

One mighty big shark vert my friend !!!

 

RB

[gavialboy]

congrats on finding that massive shark vert

[jcbshark]

Wow, that's an absolute monster! Biggest I've ever found would be hard pressed to be 1 1/4 in in diameter

[Doctor Mud]

Thanks guys,

 

I felt very lucky to find this bit. I'm a bit sore today. I'm used to walking a lot but not flipping boulders. The rock here is also very hard so trimming is hard work.

 

Just measured the vert and its 16 cm or 6.3 inches in diameter. I would love to find the other half!

 

Its been a dream of mine to find Meg material at this site and this could be it. Only other candidates could be Basking Shark (Cetorhinus maximus) or Whale Shark (Rhincodon typus). 

 

Basking Shark verts appear quite distinctive and I don't believe it is from one of these:

 

 

I couldn't find an image of Whale Shark verts yet.

[Doctor Mud]

I went back to the beach and hunted for the other half of the vert. Not the imprint, but the other half of the actual vert. I took a garden hoe to clear away the sand and then used my pick to lever up the boulders. This was a lot of work. I moved a lot of sand and flipped a lot of boulders.

 

No luck unfortunately. It could be still buried under the sand, or even still in the cliff face.

 

While I was having a break I walked along the front of the cliff and explored the geology. the concretions are popping out of the toe of a 400 m wide slump. I spotted this crab bearing concretion half still in the cliff face:

 

 

And this made me think that the other part of the vert could still be in there somewhere slowly creeping in the moving soil, waiting to pop out on the beach one day. This also solved the puzzle of the missing concretion halves. Many of the crab concretions on the beach don't have matching halves. I think they are splitting in the cliff face and soil creep might eventually take the halves on slightly different trajectories.

This could take hundreds of years for the concretions to work their way out.

 

Most of the split concretions have a layer of calcite on the split face. I wonder if calcite dissolves in groundwater and crystallizes in the small pores or fissures in the concretion. The expanding calcite zone eventually forces the concretion apart over many years.

 

So no other half, but I left learning more about one of my favourite sites which is almost as valuable in my book.

 

I'll keep my eyes peeled when I visit. Who knows it may pop up one day..... 

 

[Doctor Mud]

I was cleaning the rock and I noticed that wetting the calcite on the split surface showed up the cross section of the vertebra.

Impressive!

Really reveals the size of this thing. The edge of the vert goes to the 170 mm (6.5 inches) mark on the top of the image.

 

 

I think I'll prep the underneath at least as it is more complete.

I feel lucky to find this but you can't blame me for wanting the other half eh?

 

Im surprised at how thin it is for its diameter. I don't know much about shark verts, but imagine there might be differentiation in the vert column like mammals with cervical verts being thinner. 

Could also be compression during diagenesis?

 

Now to juggle baggage weights for the flight home.