NO. 9 GRAND CANYON FOSSIL FOOTPRINTS GILMORE 33 



In looking at this specimen, one is struck by the general distinct- 

 ness of the outlines and the perfection of preservation, but an attempt 

 to refer it to a particular class of animals results in great perplex- 

 ity. The wonder is that an animal, apparently so small and light, 

 should have left any impression that could be converted into rock. 

 It is quite unlike any of the described trails attributed to crustaceans, 

 myriapods, or insects, and yet it gives every indication of having been 

 made by some invertebrate animal. The specimen has been examined 

 by the several specialists in the United States National Museum deal- 

 ing with these groups, and all disclaim its relationship to any with 

 which they are familiar. 



Regardless of my inability to definitely classify these tracks, their 

 distinctive character makes it desirable to name them, and the new 

 genus and species Paleohelcura tridactyla is proposed for their re- 

 ception. It is my impression that they represent the trail of some 



*|9 





Fig. 21. — Undescribed trackway in museum at Weimar, Germany, 

 from the Triassic. -\ natural size. Sketch by O. Abel. 



invertebrate ; they certainly do not display features indicative of the 

 foot of any known vertebrate animal. 



On a recent visit to the United States National IMuseum, the dis- 

 tinguished paleontologist, Prof. Othenio Abel, called my attention to 

 a series of tracks preserved in the museum at Weimar which bear a 

 certain resemblance to the tracks under consideration. These are 

 shown in figure 21, reproduced from a sketch by Professor Abel who 

 generously permitted its use. This series of tracks is from the 

 Bundsandstein (Triassic) between Schonalkalden and Trowback 

 near Nesselberg, and are therefore somewhat younger than the Grand 

 Canyon specimen. They show the same grouping in threes set at an 

 oblique angle to the median line of movement, and with a similar 

 relative width of trackway. They differ, however, in their larger size, 

 lack of tail trace, and in having the clusters of the two sides opposite, 

 whereas the clusters alternate in the Arizona form. While these dis- 

 tinctions are important, the Austrian specimen is of interest in being 



