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Identification of Marshosaurus Teeth


Troodon

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Marshosaurus bicentesimus is a midsize theropod in the Morrison Formation in the Megalosauridae family. Over the past few years, teeth are becoming available in the open market simply because dealers/diggers are now more aware of this species and like to sell them.  Isolated teeth from the Morrison Formation are very difficult to diagnose because of their similarity and all require an understanding of additional characteristics than normal, in hopes of properly identifying them.   The best I can do is to look at other reference publications some which include similar teeth from Portugal and Germany which describe morph types and then assign them to the best taxon.  I also have been able to obtain information from  C. Hendrickx recent publication Taxonomic identification of isolated theropod teeth 2019 that took measurements of these teeth and this edit reflects that information.  .

 

The following information is needed to identify these teeth: 

 

1)Photo of tooth, both sides and base and one of the mesial edge (outer)

2)Serration density of both edges 5 mm wide at midline

3)Dimensions: CBL, CBW, CH

4) Locality: State and County

 

2051082515_TheropodtoothID2.thumb.jpg.c270be5183857b1f87f6a6fcbacb498d.jpg

 

 

 

 

Three Key Characteristics :. 

 

1) Mesial Carina should extend down at least 2/3 

First and most important since this is a Megalosaurid the anterior carina (serrations) only come up to  2/3 of the way down the keel. 

post-10935-0-09351400-1440683250_thumb.jpg

 

2) Serrations on both edges should be different  (Hendrickx Study 8 teeth)

The serrations are finer than most other large theropods in the Morrison.  Mesial edge must be finer than Distal

 

DSDI : Denticle size density index =  Mesial Density ÷ Distal Density   Should be Greater than 1.15  

 

Mesial at Centerline MC : around 20/ 5 mm

 

Distal at Centerline DC : 15-17/ 5mm, posterior teeth may be higher

 

3) Crown Base and Height ratios

These teeth are compressed and the ratio looks at that compression.  Marshosaurus teeth must fall into these parameters 

 

CBR: Crown Base Width (CBW) ÷ Crown Base Length (CBL) = Dentary (around 0.5-0.6), Maxillary (around 0.3)

 

CHR: Crown Height Ratio (CH) ÷ Crown Base Length (CBL) = 1.5 to 2.5 may be lower on distal teeth

 

4) Other Characteristics 

Might show light transverse undulations

Might show some short Interdental sulci but typically absent

 

 

Representation of teeth that are similar to Marshosaurus  C1-3

Screenshot_20180903-083147.thumb.jpg.c19196f116983cdf54c8d0871b8e991c.jpg

 

 

 

Reconstruction  Skull of Marshosaurus from Utah Museum of Natural History.

So you can see variation of the teeth in jaw

DSC_0168.thumb.JPG.6e8e6a30918bbbfd087609ef83459e45.JPG

 

Reference:

1) Hendrickx, C., Mateus, O., and Araújo, R. 2015. The dentition of megalosaurid theropods. Acta Palaeontologica Polonica 60 (3): 627–642.

 

2) Journal of Iberian Geology

June 2017, Volume 43, Issue 2 , pp 257-291

Analysis of diversity, stratigraphic and geographical distribution of isolated theropod teeth from the Upper Jurassic of the Lusitanian Basin, Portugal

 

3) Multivariate and Cladistic Analyses of Isolated Teeth Reveal Sympatry of Theropod Dinosaurs in the Late Jurassic of Northern Germany

Oliver Gerke, Oliver Wings

Published: July 6, 2016

https://doi.org/10.1371/journal.pone.0158334

 

4) A second new Theropod dinosaur from the late Jurassic of east central Utah  1979 by J Madsen 

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This is some awesome reading.

Troodon man, you gotta get the MoTM award!

Looking forward to meeting my fellow Singaporean collectors! Do PM me if you are a Singaporean, or an overseas fossil-collector coming here for a holiday!

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Thank you for posting these helpful and informative posts about teeth from the Morrison. Will die tell be using these in the future.

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This is some awesome reading.

Troodon man, you gotta get the MoTM award!

Sorry haha I meant,"I will definitely be using these in the future."

Thanks guys, hope you get good use of the information

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Completely updated first page based on obtaining published information versus my personal collection.

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