WERE THE TRACKMAKERS FOR THE DINOSAUR 
ICHNOTAXA GRALLATOR, ANCHISAURIPUS,  AND 
EUBRONTES  REALLY THEROPODS?

	SMITH, Joshua B., Department of Geology, University of 
		Pennsylvania, 
		240 South 33rd Street, Philadelphia, PA  19104-6316
	FARLOW, James O., Department of Geosciences, Indiana 
		University - Purdue
		University at Fort Wayne, Fort Wayne Indiana  46805

As paleoecology and biostratigraphy using footprint taxa require 
confident assignments of trackmakers to the tracks, and as such 
studies in the Newark Supergroup would involve the common 
dinosaur ichnotaxa Grallator, Anchisauripus, and Eubrontes , it is 
desirable to determine if trackmakers for these taxa can be assigned.  
These taxa have historically been referred to the Theropoda.  
Comparisons of the pedal foot skeletons of potential trackmakers of 
tridactyl dinosaur tracks show that theropods tend to have long, thin 
digits, with digit III relatively longer than digits II and IV.  In 
addition, theropod feet tend to have relatively short unguals and 
relatively long phalanges in the middle portions of the digits 
compared with ornithischians and prosauropods.
	Using specimens of these taxa from collection and outcrop, we 
have made statistical comparisons between the track morphologies 
and the morphologies of several types of theropod and ornithischian 
dinosaurs.  Farlow and Lockley (1993) calculated means and ranges 
for variables that distinctly show variation between theropods and 
non-theropods for a number of taxa.  We have analyzed these 
ichnotaxa in the same manner.  
	The means of digit III/digit II lengths are: for Grallator, 1.47, 
Range 1.27-1.87; Anchisauripus, 1.37, R 1.08-1.71; Eubrontes , 1.25, 
R 0.9-2.6.  Grallator is close to Farlow and Lockley's (1993) mean for 
theropods (1.48, R 1.03-1.79), while Anchisauripus  is close to 
ornithischians (1.38, R 1.19-1.57) and Eubrontes  is near 
prosauropods (1.21, R 0.99-1.38).  The means for digit III/digit IV 
lengths are: for Grallator, 1.28, R 1-1.58; Anchisauripus, 1.14, R 
0.84-2.30; Eubrontes, 0.96, R 0.81-1.73, in this case all are closest to 
the Early Mesozoic theropod mean of 0.94 (R 0.81-1.05) and a 
moderate distance from the means of all non-theropods (ca. 0.77).  
The means for the ungual II3/phalanx II2 lengths are: for Grallator, 
1.26, R 1.04-1.43; Anchisauripus, 1, R 0.66-1.29; Eubrontes , 1.08, R 
0.89-1.73.  All plot closest to the Early Mesozoic theropods (1.00, R 
0.73-1.38), but Grallator is close to Early Mesozoic ornithischians 
(1.35).  The means for the phalanx III2/phalanx IV1 lengths are: for 
Grallator, 1.64, R 1.64; Anchisauripus, 1.43, R 1-1.76; Eubrontes, 
1.10, R 0.84-1.37.  Grallator  and Anchisauripus  fall near the Early 
Mesozoic theropods 
(1.38 R 0.78-2.24), but Eubrontes  is very close to prosauropods 
(0.85, R 0.67-1.20).
	Although there is significant variation between these mean 
values, the amount of overlap in the ranges dramatically reduces the 
usefulness of this data.  Many of the proportions fall just as close to 
non-theropod groups as they are to theropods or are well within non-
theropod ranges, raising some doubt about how accurate any 
trackmaker assignments are likely to be using this method.
	However, relationships between the phalanx measurements 
and the relationships between the digit measurements are both linear, 
and theropods and non-theropods tend to separate nicely if these 
proportions are compared.  The three ichnotaxa tend to cluster well 
within the theropods on a plot of digit III /digit IV lengths vs. digit 
III/digit IV lengths.  On a plot of phalanx III2/phalanx IV1 lengths vs. 
ungual II3/phalanx II2 lengths, the ichnotaxa again fall within the 
theropod cluster, with Grallator and Anchisauripus plotting close to 
Coelophysis.  Interestingly enough, Eubrontes falls much closer to 
Herrerasaurus and Liliensternus than to its hypothesized trackmaker 
Dilophosaurus.

Farlow, J.O., and Lockley, M.G., 1993, An osteometric approach to the 
identification of the makers of early Mesozoic tridactyl dinosaur footprints.  In 
Lucas, S.G., and Morales, M. (eds.), The Nonmarine Triassic:  New Mexico 
Museum of Natural History and Science Bulletin, No 3, p. 123-131.