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MarcoSr

Some more Riker mount displays from the Eocene and Miocene of Maryland

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MarcoSr

Here are three more Riker mount displays that I just put together with my macro specimens from a site in Maryland with both Eocene and Miocene formations.

 

The first 16”X12” display has shark specimens with Miocene shark teeth above the shark vertebrae and Eocene shark teeth below the shark vertebrae.  The bottom Eocene shark teeth are mostly Otodus aksuaticus with a few Otodus auriculatus (for size reference the largest O. aksuaticus is 3").  The top Otodus teeth are Otodus chubutensis (for size reference the largest O. chubutensis is 3.5").  There is also a Miocene Parotodus in the top middle of the display.

 

 

5e24c937e70c4_EoceneMioceneNanjemoyCalvertFormationsPopesCreekCharlesCountyMarylandsharkspecimens116X12.thumb.JPG.e5b4b863c14397ee3f3260f9e85fbb78.JPG

 

 

The second 16”X12” display contains both marine and terrestrial mammal specimens, bird specimens, reptile specimens, bony fish specimens and two bivalve shell specimens.  Some of these specimens come from the Miocene like the two peccary teeth in the bottom right and some definitely come from the Eocene like the sea snake vertebrae in the bottom left and middle.

 

 

5e24c9324ff64_EoceneMioceneNanjemoyCalvertFormationsPopesCreekCharlesCountyMarylandbonyfishmarinemammalandreptilespecimens216X12.thumb.JPG.80f2d214bd37d49adbcb5f9e8483eba3.JPG

 

 

The third display (8”X12”) contains both Eocene and Miocene ray including sawfish specimens (for size reference the large partial eagle ray barb, which is in two pieces, is 6.5" total length).  This display also contains at the bottom two medial Eocene ray pavement teeth, Leidybatis jugosus.

 

5e24c93508474_EoceneMioceneNanjemoyCalvertFormationsPopesCreekCharlesCountyMarylandrayspecimens8X12.thumb.jpg.068005fbd01ab93b4f8ca8f3033cc688.jpg

 

 

Marco Sr.

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Darktooth

It is obvious that you have found many great specimens over the years. Any favorites? Also how can you tell the difference between Otodus akuaticus vs Otodus auriculatus? 

 

Thanks Dave

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MarcoSr
3 hours ago, Darktooth said:

It is obvious that you have found many great specimens over the years. Any favorites? Also how can you tell the difference between Otodus akuaticus vs Otodus auriculatus? 

 

Thanks Dave

 

Dave

 

My favorite specimen is the huge Oligocene tortoise that I collected from my sons' M&M ranch in 2016.  Not so much the tortoise itself, but the associated memories of the time spent with my sons excavating it, jacketing it, and getting it out of the ranch.  Then the possum and owl specimens, new species to science, from the Eocene of Virginia which I donated.  Lastly a specimen that I found in Virginia in 2019 which I can't say much about until the paper is published which hopefully will be this summer.

 

You can tell the difference between Otodus aksuaticus vs Otodus auriculatus by the serrations on the crown.  The serrations do not go all the way to the tip of the crown on O. akuaticus.  O. auriculatus are fully serrated all the way to the crown tip.

 

Marco Sr.

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Darktooth
32 minutes ago, MarcoSr said:

 

Dave

 

My favorite specimen is the huge Oligocene tortoise that I collected from my sons' M&M ranch in 2016.  Not so much the tortoise itself, but the associated memories of the time spent with my sons excavating it, jacketing it, and getting it out of the ranch.  Then the possum and owl specimens, new species to science, from the Eocene of Virginia which I donated.  Lastly a specimen that I found in Virginia in 2019 which I can't say much about until the paper is published which hopefully will be this summer.

 

You can tell the difference between Otodus aksuaticus vs Otodus auriculatus by the serrations on the crown.  The serrations do not go all the way to the tip of the crown on O. akuaticus.  O. auriculatus are fully serrated all the way to the crown tip.

 

Marco Sr.

Thanks for your reply.  I will be looking forward to hearing about the new specimen.

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Praefectus
1 hour ago, MarcoSr said:

 

Dave

 

My favorite specimen is the huge Oligocene tortoise that I collected from my sons' M&M ranch in 2016.  Not so much the tortoise itself, but the associated memories of the time spent with my sons excavating it, jacketing it, and getting it out of the ranch.  Then the possum and owl specimens, new species to science, from the Eocene of Virginia which I donated.  Lastly a specimen that I found in Virginia in 2019 which I can't say much about until the paper is published which hopefully will be this summer.

 

You can tell the difference between Otodus aksuaticus vs Otodus auriculatus by the serrations on the crown.  The serrations do not go all the way to the tip of the crown on O. akuaticus.  O. auriculatus are fully serrated all the way to the crown tip.

 

Marco Sr.

How does O. poseidoni fit into the evolutionary line? I thought O. auriculatus had serrations that went up 2/3 of the way up the crown and that O. poseidoni was the first fully serrated tooth. Mark Renz's book, Megalodon, Hunting the Hunter, states that O. auriculatus serrations did not reach the tip of the crown. I usually classify teeth older than 50 million years as O. aksuaticus and younger, but not fully serrated teeth as O. auriculatus. Can the serrations themselves be used to differentiate the species? I notice that O. aksuaticus teeth have more jagged, uneven serrations while O. auriculatus serrations are regularly spaced. 

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MarcoSr
10 hours ago, Praefectus said:

How does O. poseidoni fit into the evolutionary line? I thought O. auriculatus had serrations that went up 2/3 of the way up the crown and that O. poseidoni was the first fully serrated tooth. Mark Renz's book, Megalodon, Hunting the Hunter, states that O. auriculatus serrations did not reach the tip of the crown. I usually classify teeth older than 50 million years as O. aksuaticus and younger, but not fully serrated teeth as O. auriculatus. Can the serrations themselves be used to differentiate the species? I notice that O. aksuaticus teeth have more jagged, uneven serrations while O. auriculatus serrations are regularly spaced. 

 

Truthfully I hadn't heard of O. poseidoni before your post.  Otodus is a lineage from obliquus to megalodon.  A researcher could make as many species as the researcher wants if a splitter or as few as the researcher wants if the researcher is a combiner.  There are no universal rules that I'm aware of that guide when features of a tooth change enough to warrant a change in the species or genus name.  You really can't even tell the difference between some specimens of different species in the Otodus lineage because the tooth features of the species are so variable and overlapping and researchers use the age of the formation to id the species.  I collect from the Eocene Woodstock Member of the Nanjemoy Formation in Maryland (for over 45 years) which contains the transition from O. obliquus to O. auriculatus.  I have many tooth examples in this transition, only a sample of which are contained in the Riker mount display in this post.  I can tell you from my specimens those that I label as O. aksuaticus can have very fine, uniform serrations and others can have ragged, irregular serrations that do not go down to the crown tip and that the specimens that I label as O. auriculatus have very ragged, large serrations that go to the very tip of the crown.  Researchers like Cappetta use a totally different terminology for these species.  Russian researchers break down the lineage further.  Trying to debate some of this naming is not productive.

 

Marco Sr. 

 

Further Edit:  I use the following criteria to ID Otodus teeth from the Eocene Woodstock Member of the Nanjemoy Formation:  O. obliquus - No serrations at all, O. aksuaticus - Partially serrated, serrations do not go all the way down to the tip, O. auriculatus - fulled serrated, serrations go down to the tip

Edited by MarcoSr
Acknowledge the diversity of different species naming by different researchers and give my naming criteria

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WhodamanHD

O. poseidoni is to my understanding a synonym to O. auriculatus, just a bit further on its way to O. sokolovi. It’s a splitters game, doesn’t really matter what you call them as long as you understand where they stand ecologically and evolutionarily.

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Praefectus

Thanks for the informative response. I find the classification of the transitional species difficult to understand because of contrasting opinions of different researchers.

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