The Two Medicine Formation: Identification, Faunal Lists and Localities

[Troodon]

More and more dinosaur material is becoming available from the Two Medicine Formation.   I see lots of misidentified material and some with questionable localities that might fit other deposits.  I would like to summarize what I believe is currently known and published.  If you see any omissions or errors, please let me know

 

Not a lot of good maps out there to show the formation but here are two.   The TMF is about 650 meters thick and is the western equivalent of the Judith River Formation.  Most of the sediments were deposited in streams, rivers and lakes.  It overlies the Virgelle Sandstone and underlies the Bearpaw Formation.

 

More important, for collectors buying material to be aware of the counties that have the majority of exposures they include but not exclusive to: Glacier County, Teton County, Lewis and Clark County and Pondera County

 

 

 

 

 

 

 

Faunal List:  9/13/22  (excludes Avialae) Lots of changes in recent years so older hard copy books are most likely out of date e.g. Dinosauria 2nd edition.  This list was developed based on looking at a number of different reference sources, not Wikipedia, and like most lists some paleontologists or collectors may have different opinions, which is fine

 

Tyrannosauridae:

- Daspletosaurus horneri (Carr et al. 2017)

- Gorgosaurus sp.

 

Dromaeosauridae:

- Dromaeosaurus indet.

- Saurornitholestes indet.

- Bambiraptor feinbergorum (Burnham et al. 2000)

 

Theropods:

- cf Troodon formosus

- cf Richardoestesia sp.

- cf Paronychodon?

 

Ankylosayria:

- Scolosaurus cutleri (Nopcsa 1928)

- Edmontonia rugosidens (Sternberg 1928)

 

Ceratopsidae:

- Rubeosaurus (Styracosaurus) ovatus (Gilmore 1930) 

- Einiosaurus procurviconis (Sampson 1994)

- Achelosaurus hornei (Sampson 1994)

- Prenoceratops pieganesis (Chinnery 2004)

 

Hadrosauroidae:

- Maiasaura peeblesorum (Horner & Makela 1979)

- Prosaurolphus maximus (Brown 1916)

- Gryposaurus latidens (Horner 1992)

- Hypracrosaurus stebingeri (Horner & Currie 1994)

 

Thescelosauridae:

- Orodromeus makelai (Horner & Weishample 1988)

 

Pachycephalosauridae:

- Stegoceras sp.

 

Caenaganathidae:

- Chirostenotes pergracilis (Gilmore 1924)

 

 

References:

-  Dinosaurs under the Big Sky, Jack Horner, 2001 Mountain Press Publishing Co.

 

- Rogers RR. Sequence analysis of the Upper Cretaceous Two Medicine and Judith River formations, Montana: nonmarine response to the Claggett and Bearpaw marine cycles. J Sediment Res. 1998; 68: 615–631.

 

- McDonald AT (2011) A Subadult Specimen of Rubeosaurus ovatus (Dinosauria: Ceratopsidae), with Observations on Other Ceratopsids from the Two Medicine Formation. PLoS ONE 6(8): e22710. doi:10.1371/journal.pone.0022710

 

- Caleb Marshall Brown , David C. Evans , Michael J. Ryan & Anthony P. Russell (2013) New data on the diversity and abundance of small-bodied ornithopods (Dinosauria, Ornithischia) from the Belly River Group (Campanian) of Alberta, Journal of Vertebrate Paleontology, 33:3, 495-520, DOI: 10.1080/02724634.2013.746229

 

- Michael J. Ryan , Robert Holmes & A. P. Russell (2007) A revisionof the late campanian centrosaurine ceratopsid genus Styracosaurus from the WesternInterior of North America, Journal of Vertebrate Paleontology, 27:4, 944-962, DOI:10.1671/0272-4634(2007)27[944:AROTLC]2.0.CO;2

 

 

[Troodon]

I'll continue to develop this topic like the one on the Judith River Formation..   Need to collect some data before I can proceed....