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Sharktooth Hill Dorsal Spine?


ArrowHead

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I'd like to get some opinions on my tentative id of this specimen as a dorsal spine from the Bullhead/Horn shark (Heterodontus sp.).  I haven't been able to locate many good images of these spines and this specimen is significantly larger than the few photos I've found. Is this a dorsal spine and if so what is the normal size range? This was collected this past weekend at Ernst Quarries, Slow Curve (Sharktooth Hill), Round Mountain Formation, Middle Miocene.  Any help on the id is appreciated. Also curious if the Heterodontus from that period were larger than the extant Pacific species which don't seem to grow much larger than a meter in length.

Heterodontus1.JPG

Heterodontus2.JPG

Heterodontus3.JPG

Heterodontus4.JPG

Heterodontus5.JPG

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Here are isurus90064 images from his gallery of Heterodontus

gallery_92_999_105006.jpg.5550642904bdb5ef6d6b950549a881ba.jpg

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My son Mel has two shark spines from the Ernst Ranch.  The one below is 4+ inches.

 

image.thumb.png.f4b970ec252dbe040fde026c38cbcf89.png

 

 

Marco Sr.

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It appears the spines over 4" are on the upper end but still within the expected size range for this location. Thanks for the additional information.

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On 12/6/2017 at 1:46 PM, ArrowHead said:

It appears the spines over 4" are on the upper end but still within the expected size range for this location. Thanks for the additional information.

 

I agree that 4 inches would be at the upper end of the size range for the first dorsal fin of an adult.  The second dorsal fin was likely smaller as in modern horn sharks and therefore had a smaller spine so the smaller ones do not necessarily belong to juveniles.  The teeth appear to be around the same size range of modern horn sharks though tooth and spine size might not be the best indicators of body size.  However, I tend to think a modern horn shark around a meter (+/- 39 inches) might have a 4-inch first dorsal fin spine since much of the spine is not exposed in life.

 

That is a good find as they are rare in any condition.  I didn't find one in 14 years of digging the STH Bonebed.

 

As an extra note, I guess it could be possible that at least some of the spines found in the Sharktooth Hill Bonebed could belong to Squalus occidentalis, the dogfish from there, Dogfishes also have fin spines.  A friend once gave me two modern ones - S. acanthias, I believe..  Those two are smaller and more slender compared to horn shark spines but I haven't seen a study that compares and contrasts them.

 

Jess

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Hey Jess - thanks for the perspective on spine size. I suspect there are Squalus spines at STH as well, but I have yet to find one.. The spines of modern dogfish are significantly smaller and thinner so maybe they did not fossilize as easily. I'll keep looking.

 

I was lucky on this horn shark find because a block of sediment came out with the spine fully exposed on a cleaved face. It was easy to remove undamaged. Better lucky than good...

 

I had a good weekend digging at STH this past weekend. Found a very nice Squalodon tooth, a partial Neotherium jaw with three teeth, my largest to date Hemipristus upper (1 5/8") and a jumbo C. planus (2 1/8"). The weather was perfect and I had the place to myself all weekend. I guess everyone else was Christmas shopping....

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Hi,

 

5 hours ago, ArrowHead said:

The spines of modern dogfish are significantly smaller and thinner so maybe they did not fossilize as easily.

Please, what is the latin name for dogfish ? Because translator says "roussette" in french. But that corresponds to the Scyliorhinus genus and Scyliorhinus hasn't any spine !

 

Coco

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3 minutes ago, Coco said:

Hi,

 

Please, what is the latin name for dogfish ? Because translator says "roussette" in french. But that corresponds to the Scyliorhinus genus and Scyliorhinus hasn't any spine !

 

Coco

Squalus acanthias

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Just a minor clarification because the thread was about Sharktooth HIll. The north Pacific dogfish from the STH location are described as Squalus occidentalis though I expect the morphologies were very similar to the extant S. acanthias

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