Identification of Theropod Teeth of the Morrison Fm

[Troodon]

I periodically get asked about theropod teeth, so this is what I know.  If you have additional tooth related information please pass it on since very little is known or published.

 

Tanycolagreus topwilsoni

The holotype included a fragmented skull with one premaxillary and two lateral teeth.  Unfortunately, the teeth were crushed with no visible serrations so it's unknown how to describe them.

 

Holotype skull

 

 

 

 

 

Koparion douglassi

Oldest known Troodontid and only known from a single maxillary tooth.  Pictures says it all.  A tooth taxon!

Scale: A 1 mm, B-F 100 micrometers

Chure, D. J. (1994). "Koparion douglassi, a new dinosaur from the Morrison Formation (Upper Jurassic) of Dinosaur National Monument; the oldest troodontid (Theropoda: Maniraptora)." Brigham Young University Geology Studies, 40: 11-15

 

 

Hesperornithoides miessleri

A new Troodontid.  The serrations on the mesial carinae of maxillary teeth are smaller than the distal serrations as in basal dromaeosaurids. Mesial serrations are restricted to the apical third of the crown and appear absent in some teeth. Serrations are small (5.5 per mm distally).  The teeth are labiolingually compressed, and the enamel shows no trace of longitudinal grooves.  Unfortunately the paper does not identify the sizes of these teeth.

 

Distal Serration Density  5.5/mm

FABL: around .45

 

 

 

https://peerj.com/articles/7247/

 

 

Coelurus fragilis

Known from a fairly complete skeleton however there is a question if the dentary, below, belongs to the skeleton.  No teeth were recovered and cannot find any additional information on teeth. 

 

Ken Carpenter recently responded to my inquiry about these teeth.  He stated that we have no teeth from this dinosaur.  Teeth have been called Coelurus because they are small but there is no proof of association

Carpenter, K., Miles, C., and Cloward, K. (2005). "New small theropod from the Upper Jurassic Morrison Formation of Wyoming." in Carpenter, K. 2005. The Carnivorous Dinosaurs, Indiana University Press: 23-48

 

 

Ornitholestes hermanni

Skull with both mandibles are part of the holotype.   Osborn et. al (1917) paper just comments that the teeth are small and feeble.  Carpenters book mentions that the skull is presently being studied by Mark Norell.  C. Hendrickx 2019 paper shows some data on these teeth which  I present here, 11 teeth were included in this study.

 

Although very little is known with these teeth here is some data taken from AMNH holotype skull.  Looks like the serrations are extremely fine.

 

Maxillary teeth CH range from: 3.1 to 6.5 mm

Dentary teeth CH range from: 3.9 to 5.6 mm

Crown Height Ratios : 1.5 to 2.3

Crown Base Rations : 0.52 to 0.8

Interdental Sulci: Absent

Transverse Undulations: Absent

 

Serration density : Distal serrations were present on two teeth: a Maxillary Tooth 50/ 5/mm and Dentary Tooth 60/ 5mm

 

 

 

 

Carpenter, K., Miles, C., and Cloward, K. (2005). "New small theropod from the Upper Jurassic Morrison Formation of Wyoming." in Carpenter, K. 2005. The Carnivorous Dinosaurs, Indiana University Press: 23-48

 

Reconstructed Skull AMNH

Osborn, Henry Fairfield (1917). "Skeletal adaptations of Ornitholestes, Struthiomimus, Tyrannosaurus". Bulletin of the American Museum of Natural History. 35 (43): 733–771. hdl:2246/1334.

 

 

 

Allosaurus fragilis (updated 6/19/22)

Very little is published to aid in identification of these teeth.  A recent paper by C. Hendrickx provided information on 60 teeth included in his study that I present in this edit.

 

The following information is needed to help identify these teeth

From Study: 

Premaxillary Positions: 

Serration Density:

DSDI:  0.83 to 1.05 (Average : 0.98)

Distal Density:  9.5 to 12.5 / 5 mm (Average : 10.3/ 5mm)

Mesial Density: 8.3 to 11 .3 / 5 mm  (Average : 10.1/ 5 mm)

 

Other characteristics:

Transvers Undulations:  Can be present

Interdental Sulci:  Can be present

 

Maxillary Positions:

Serration Density:

DSDI:  0.8 to 1.1 (Average : 0.95)

Distal Density:  10 to 17.5 / 5 mm (Average : 12.5/ 5mm)

Mesial Density: 9.5 to 14.0 / 5 mm  (Average : 11.9/ 5 mm)

 

Crown Height Ratio CH / CBL :  1.7 to 2.2 (Average : 2.1)

Crown Base Ratio CBW / CBL :  0.37 to 0.8 (Average : 0.57)

 

Other characteristics:

Transvers Undulations:  Can be present

Interdental Sulci:  Can be present

 

Dentary Positions:

Serration Density:

DSDI:  0.91 to 1.3 (Average : 1.08)

Distal Density:  10 to 13.75 / 5 mm (Average : 12.0/ 5mm)

Mesial Density: 10 to 16.25 / 5 mm  (Average : 13.1/ 5 mm)

 

Crown Height Ratio CH / CBL :  1.8 to 2.5 (Average : 2.2)

Crown Base Ratio CBW / CBL :  0.7 to 1.1 (Average : 0.86 )

 

Other characteristics:

Transvers Undulations:  Can be present

Interdental Sulci:  Can be present

 

Unknown Positions:

Serration Density:

DSDI:  0.87 to 1.4 (Average : 1.07)

Distal Density:  9 to 13.5 / 5 mm (Average : 11.4/ 5mm)

Mesial Density:  8.8 to 17.5 / 5 mm  (Average : 11.9/ 5 mm)

 

Crown Height Ratio CH / CBL :  1.75 to 2.3 (Average : 2.2)

Crown Base Ratio CBW / CBL :  0.46 to 1.1 (Average : 0.73 )

 

Other characteristics:

Transvers Undulations:  Can be present

Interdental Sulci:  Can be present

 

 

Base shape can assist in identification.  They can be J shaped

 

 

The morphologically space occupied by Allosaurus is also seen by Ceratosaurus

 

Poster with these illustrations

Testinet.al.2011Poster.pdf

 

 

 

cf Aviatyrannus

Zone 2 South Dakota 

Not much is known on the teeth, its a tyrannosauroid

 

Stokesosaurus clevelandi

Zone 5 Utah late Kimmeridgian-early Tithonian

Not much is known on the teeth, its a tyrannosauroid

 

Saurophanganax maximus

Zone 5 Oklahoma late Kimmeridgian- early Tithonian

Allosaurid - might be an adult Allosaurus- teeth should be the same as one

 

Torvosaurus

 

Ceratosaurus 

 

Marshosaurus

 Reconstruction  Skull of Marshosaurus from Utah Museum of Natural History.

So you can see variation of the teeth in jaw

 

 

 

 

 

 

[jpc]

There are also smaller theropods known from Morrison microsites.  No work has been done on these.  Some are as small as 5mm.  Could be babies, could be unknown animals.  

[Troodon]

Updated:

Ornitholestes hermanni

Allosaurus

Ceratosaurus

Marshosaurus

Torvosaurus 

[Troodon]

Updated Allosaurus