Troodontid Teeth – WP#6


A small selection of troodontid theropod teeth is presented below. Before you get to it, however, note that for among some of these taxa, their identities are a little shaky. This has a lot to do with one of the more persistent “wastebasket” taxa among theropods, Paronychodon lacustris [1]. Among other tooth-based taxa, Paronychodon lacustris and Paronychodon sp. (a general container for a large variety of things, several of which may be unique taxa on their own) includes the morphology of triangular theropod teeth with vertical ridges. Aberrant ridges, carinae, and the apparent absence of denticles in some otherwise theropodan teeth appear on occasion in collections, and most, if not all, of them are referred to the taxon Paronychodon in one of several ways, which I will get into in a different post dedicated to the taxonomy of taxonomy (you heard me).

Troodontid teeth, among others. Scale bar in all figures is 1 mm. mc: mesial carina; r: ridges.

Most of these are troodontid teeth. The reason Paronychodon lacustris is included among these is because some of the teeth included among the collection referred to it are shaped much like troodontid teeth are. This morphology is not unique to troodontids, but it is instructive: A blade-shaped (ziphodont) crown, with a “bulbous” base and a constriction between crown and root; the distal margin is often shallowly curved, while the mesial margin is strongly curved, creating a strongly arcuate tooth morphology. This morphology is relatively consistent among troodontid teeth, but it is also found in basal dromaeosaurids, Archaeopteryx, and in some cases a few miscellaneous basal coelurosaurians. As such, even including some of these Paronychodon lacustris morphotypes among troodontids is questionable.

Key to the figure:

A. Troodon formosus, ANSP 9259 (holotype), isolated crown.
B. Troodontidae, TMP 83.12.11, isolated crown.
C. Zanabazar junior, GIN 100/1 (holotype), premaxillary crown.
D. Zanabazar junior, GIN 100/1 (holotype), mesial maxillary crown.
E. Sinornithoides youngi, IVPP V9812 (holotype), mesial dentary crown.
F. Zanabazar junior, GIN 100/1 (holotype), distal dentary crown.
G. Zanabazar junior, GIN 100/1 (holotype), distal maxillary crown.
H. Sinornithoides youngi, IVPP V9812 (holotype), mesial maxillary crown.
I & J. Non-theropodan teeth whose identities will be revealed at a later date.
K. Paronychodon lacustris, morphotype B, isolated crown.
L. Byronosaurus jaffei, GIN 100/983 (holotype), mesial maxillary crown.
M. Troodontidae, TMP 2000.21.11, isolated crown.
N. Euronychodon, isolated crown.

Photos of most of this material served as the primary data. Additional material used includes [2] for Sinornithosaurus youngi and [3] for Byronosaurus jaffei, while [4] complemented B. [5] complemented Paronychodon lacustris (morph A & B, morph A not shown), as well as M.

[1] Cope, E. D. 1876. Descriptions of some vertebrate remains from the Fort Union Beds of Montana. Paleontological Bulletin 22:1-14.
[2] Currie, P. and Dong Z.-m. 2001. New information on Cretaceous troodontids from the People’s Republic of China. Canadian Journal of Earth Sciences 38:1753-1766.
[3] Makovicky, P.J., Norell, M.A., Clark, J.M. & Rowe, T.E. 2003. Osteology and relationships of Byronosaurus jaffei (Theropoda: Troodontidae). American Museum Novitates 3402:1-32.
[4] Currie, P. J. 1987. Bird-like characteristics of the jaws and teeth of troodontid theropods (Dinosauria, Saurischia). Journal of Vertebrate Paleontology 7(1):72-81.
[5] Sankey, J. T., Brinkman, D. B., Guenther, M. & Currie, P. J. 2002. Small theropod and bird teeth from the Late Cretaceous (Late Campanian) Judith River Group, Alberta. Journal of Paleontology 76:751-763.

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4 Responses to Troodontid Teeth – WP#6

  1. Ian Eaves says:

    I found this page most useful: exactly what I was looking for in fact. I was investigating a supposed Troodon formosus tooth from the Judithian of Alberta, Canada. Although its shape was very Troodontid, its serrations were noticeably different from those of T. formosus: they looked more like those of Saurornitholestes langstoni. So, I decided to investigate the degree of variation in Troodontid teeth. You had already done the necessary research for me. Many thanks. Ian

    • I’m glad you found it useful. Note that much of this is just a visual depiction of other work, and that I highly recommend you take the opportunity to examine the literature on tooth collections from the Dinosaur Park, Juidth River, Lance, and Hell Creek Formations, from which this is based. There, sampling and variance analyses from such as Currie, Varricchio, Balko, and Sankey will be certainly better! Note also that in some selections, teeth may vary along the tooth row (as in troodontid-like teeth in therizinosauroids), which stress that tooth-row variance in situ is a different element than gross variance of morphology, which may be reflective of taxic variation.

  2. Great and very helpful information/diagrams! ;)

    Is there any new information/find that may better indicate what family or subfamily Paronychodon or Richardoestesia may be from?

    I often wondered if Paronychodon teeth may be for helping to hold a glutinous or sticky type of salivary substance… to better enable the capturing of insects and little furry mammals.

    I wonder if Richardoestesia could be a larger form of microraptor (that survived, like Hesperonychus, into the later Cretaceous)?

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