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O. dunkeli Kem Kem?


gigantoraptor

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Hello all

 

I recently bought a tooth from the Kem Kem beds that clearly belongs to the genus Onchopristis. The weird thing about the tooth is that it has two hooks instead of just one. I know the species Onchopristis dunkeli has two (or more) hooks, but I don't find any official rapports metioning them in the Kem Kem beds. The tooth has yet to arrive, but I already wanted to ask the question. 

What do you think? Is there a chance O. dunkeli occurs in the Kem Kem beds or would it just be a pathological example. I have been searching a long time for a specimen like this. The tooth has not yet arrived so sorry, no photo's yet.

 @LordTrilobite, @Haravex 

 

Greetings

Thijs

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That's pretty interesting. No, I haven't seen any sawfish teeth from the Kem Kem beds that have two barbs. I also can't say that I am familiar with O. dunkeli.

 

Hard to tell if it's a different species or pathological without any photos though.

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Olof Moleman AKA Lord Trilobite

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note the correct spelling 'dunklei'

text and figures from:

 

Martill, D.M., Ibrahim, N. 2012

Aberrant rostral teeth of the sawfish Onchopristis numidus from the Kem Kem beds (? early Late Cretaceous) of Morocco and a reappraisal of Onchopristis in New Zealand.

Journal of African Earth Sciences, 64:71-76

 

We do, however, pass the following comments: O. dunklei from the Cretaceous of Texas has multiple cusps on its posterior border (3 in the examples figured by McNulty and Slaughter, 1962, p. 776, Fig. 1), but lacks cusps on the anterior border.  Atlanticopristis possesses cusplets on both the anterior and posterior borders of the rostral teeth, with up to 5 on the posterior border and usually fewer on the anterior border.  On the grounds that no examples of Onchopristis have been recorded with cusplets on both borders, it seems apt to retain Atlanticopristis as a distinct genus.  The validity of O. dunklei is less certain.  The occurrence of rare multi-cuspleted examples of sawfish rostral teeth in the Kem Kem beds could be taken as evidence of two sympatric species, with one considerably rarer than the other, alternatively O. numidus and O. dunklei could be considered as a single taxon with morphological variation over a wide geographic range extending across the Atlanto-Tethyan province.

 

Abundant remains of O. numidus from the Moroccan Kem Kem beds occasionally display pathological morphologies and features that resemble other species of Onchopristis, notably the multicuspletted O. dunklei of Texas.  The double cuspletted example described and figured here is most likely an aberrant morph rather than an example of O. dunklei.  The smooth rooted, multicusped examples from the Late Cretaceous of New Zealand, referred to O. dunklei are considered here to represent a distinct genus and species of Sclerorhynchidae.  This referral thus restricts both the geographical range of O. numidus to the northern hemisphere and the temporal range to the Albian–Cenomanian part of the Cretaceous.

 

image.thumb.png.e08f9cc4eaf5b0e60cdc2cf53aae880b.png

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33 minutes ago, Troodon said:

2560px-Sawfish_Teeth_Comparison_by_PaleoGeek_svg.thumb.png.29a442af9dbf396212bd0a25fddd99b8.png

Interestingly all my Kem Kem sawfish teeth resemble that yellow image of Libanopristis hiram.

Olof Moleman AKA Lord Trilobite

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5 minutes ago, LordTrilobite said:

Interestingly all my Kem Kem sawfish teeth resemble that yellow image of Libanopristis hiram.

I wonder how much we really know about this group of sawfish in africa and how accurate those images are.  Then we have lots of positional variations 

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This might help for clarity, a rare find of vertebrae and rostrum with barbs. As for O. dunkeli the thousands of fossils from this region and the number of sellers and times I have dug I have never seen one.

56956480_2364012920496047_2513047324087812096_n.jpg

57427432_826720371043173_2295592687509700608_n.jpg

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On 6/30/2019 at 12:50 PM, gigantoraptor said:

Hello all

 

I recently bought a tooth from the Kem Kem beds that clearly belongs to the genus Onchopristis. The weird thing about the tooth is that it has two hooks instead of just one. I know the species Onchopristis dunkeli has two (or more) hooks, but I don't find any official rapports metioning them in the Kem Kem beds. The tooth has yet to arrive, but I already wanted to ask the question. 

What do you think? Is there a chance O. dunkeli occurs in the Kem Kem beds or would it just be a pathological example. I have been searching a long time for a specimen like this. The tooth has not yet arrived so sorry, no photo's yet.

 @LordTrilobite, @Haravex 

 

Greetings

Thijs

 

 

Hi Thijs,

 

First of all, your question is related to an old question.  McNulty and Slaughter named Onchoprisiis dunklei in 1962 on the basis that it appeared distinct from O. numidus.  In their study material O. dunklei rostral teeth always had 3-5 barbs while O. numidus always had just one.

 

In Slaughter and Steiner (1968) the authors wondered if O. numidus represented a later stage in evolution following a trend of a reduction of barbs while O. dunklei stood closer to the ancestral form which had at least three barbs.  Yet, they also asked if rare 2-3 barbed teeth found in the Cenomanian of Egypt (where the norm was also to have just the one main barb, as we see today in the Kem Kem beds) actually reflected a trend of an increasing number of barbs.  That question would have to be answered by reviewing collections from earlier in the Albian and before.  Onchopristis apparently became extinct by the end of the Cenomanian.

 

One thing to keep in mind is that the two species seem to have the same chronologic range, both being reported from the Late Albian to Cenomanian.  However, O dunklei is clearly smaller.  An average tooth is around 10-12mm long (approx. one half-inch) while a small O. numidus rostral tooth is about twice that size with some specimens over 50mm long (approx. 2 inches).  Also, in my experience O. dunklei seems to be a rarer find in both the late Albian of Texas and the Cenomanian of France than O. numidus is in the Kem Kem Beds but my observation may not reflect the actual abundance of either form.   I don't know if anyone has proposed that O. dunklei could be a juvenile form of O. numidus.

 

From all that I would have to agree with Martill and Ibrahaim (2012) that your double-barbed rostral tooth is an example of variation within O. numidus.  Whenever we see a large number of a particular tooth, we are going to get to see a few rare variations that existed (pathological or unusually large or small, etc.)  It seems to me that someone else I know once picked up a 2-barbed tooth at Tucson some years ago but am not sure.  I can't say I've ever seen one.  I have noticed that O. numidus rostral teeth don't come to shows in the large numbers they did in the 1990's.

 

Jess

 

 

McNulty, C.L. and B.H. Slaughter.. 1962.
A new sawfish from the Woodbine Formation (Cretaceous) of Texas. Copeia (4): 775–777, 1 fig.

 

Slaughter, B.H. and M.S. Steiner.  1968.
Notes on rostral teeth of ganopristine sawfishes, with special reference to Texas material.  Journal of Paleontology, 42 (1): 233–239, 4 fig.

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On 6/30/2019 at 1:47 PM, Troodon said:

I wonder how much we really know about this group of sawfish in africa and how accurate those images are.  Then we have lots of positional variations 

 

Hi Troodon,

 

Those images are not to scale and O. dunklei rostral teeth have 3-5 barbs with one or more of them sometimes looking more like serrations.  I've seen specimens from Lussant, France as well as the "Motorola site" in Texas.  Remember when some teeth from there were coming on the market in the early-mid 90's?   And yes, there would be positional variations like stumpier teeth near the base of the rostrum or near the tip. 

 

Jess

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On 6/30/2019 at 1:42 PM, LordTrilobite said:

Interestingly all my Kem Kem sawfish teeth resemble that yellow image of Libanopristis hiram.

 

Keep in mind that Libanopristis hiram rostral teeth tend to be about 5mm long  - much smaller than the typical rostral teeth from the Kem kem Beds.

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The tooth came in today. After looking at it I am pretty sure it's indeed a pathological specimen, since the second 'hook' is twisted. If O. dunklei is indeed very small this one is certainly not one of them. The tooth measures about 8.5 cm.

It has been repaired, but it's not composited. All pieces show a connection in at least one point.

65974632_344500926221698_71220483437101056_n.thumb.jpg.062cde88e00592e2f14fa90c82ed3b64.jpg

 

 

Thanks for all the help @LordTrilobite, @Troodon @piranha, @Haravex @siteseer

 

 

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Following up on my previous comments, I checked Welton and Farish (1993) to see what they said about O. dunklei.  They have the maximum size for a rostral tooth at 30mm or more which is still significantly smaller than many O. numidus specimens I've seen from the Kem Kem beds.  They also note it as common though I've seen very few specimens for sale or trade.  Obviously, that's my limited experience and what's available within the hobby isn't a solid gauge of abundance (just an indicator).  Bruce Welton has been doing bulk screening for decades so he's been collecting more efficiently and for a longer time than most people. 

 

They also reported specimens with two barbs though those might be the shorter, stumpier ones and they gave the chronologic range of O. dunklei as Albian to Coniacian which is extends it more distantly and more recently than I allowed by perhaps 5-10 million years in both directions.

 

Welton, B. and R. Farish.  1993.

The Collector's Guide to Fossil Sharks and Rays from the Cretaceous of Texas.  Before Time. Lewisville, Texas. 204 pp.

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All I can say is after spending maybe 60 hours digging in the kem kem beds I have yet to see a rostral barb like this and looking over the collections of numerous miners who work most days digging in these formations, I do believe they exist just to say I have not ever encountered one yet so they must be very rare.

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  • 4 months later...

Today this has changed I have finally been shown one, sadly the very tip has been added but it does have the double barb.

onchopristisdunkeli.jpg

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8 minutes ago, Haravex said:

Today this has changed I have finally been shown one, sadly the very tip has been added but it does have the double barb.

Bingo! 

Got one at last. 

Glad about that, very interesting, and the tips a bit of a shame but not a huge problem in this case. :)

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On 7-12-2019 at 4:49 PM, Haravex said:

Today this has changed I have finally been shown one, sadly the very tip has been added but it does have the double barb.

Very nice, only the third more or less complete one I have seen. I'm also curious to what happened with the partial skeleton you showed before.

 

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  • 2 years later...
On 12/7/2019 at 10:49 AM, Haravex said:

Today this has changed I have finally been shown one, sadly the very tip has been added but it does have the double barb.

onchopristisdunkeli.jpg

 

 

See this updated post:

 

 

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