NO. 9 GRAND CANYON FOSSIL FOOTPRINTS GILMORE 1 3 



Genus LAOPORUS Lull 



The genus Laoporus is characterized by Lull as follows : 



Generic characters. — Quadrupedal, without tail trace, with four digits in the 

 manus and five in the pes, semiplantigrade, broad-soled, with short digits which 

 in the impressions lack phalangeal pads. Traces of claws appear to be present 

 but they have no grasping predatory function. Feet turned inward toward the 

 line of march. 



Footprints of the genus Laoporus are found more commonly than 

 any other at the Hermit Trail locality. The large slab shown in 

 plate I, figure i, has nearly one-half of its surface literally covered 

 with these tracks, and a second slab (see pi. i, fig. 2) is similarly 

 decorated. 



The closest affinities of Laoporus seem to be with Limnopus 

 Marsh ^ (see fig. 8), and while the latter has a similar digital formula, 

 the heavy, thickened toes with rounded extremities apparently lack- 

 ing claws, the strongly divergent fifth digit, and the overlapping of 

 the hindfoot impressions on those of the forefoot, seem sufficient 

 to distinguish this genus from Laoporus. 



Lull ^ comments on the character of the animals making the tracks 

 ascribed to Laoporus as follows : 



The creatures which made the footprints were quadrupeds of moderate size, 

 with broad, stumpy feet, apparently clawed, and having at least four toes in 

 front and five behind. The hindfoot, which is somewhat larger, bore a pro- 

 portionately greater share of the creature's weight, especially in the smaller 

 species \L. schuchcrti]. The limbs were apparently short, with a wide track- 

 way, implying a bulky body. No trace of a dragging tail is discernible on any 

 of the specimens, and the body was carried clear of the ground. 



These observations apply equally well to the new ixiaterials dis- 

 cussed in the following pages. At this time I see no way of definitely 

 determining whether the impressions are amphibian or reptilian in 

 origin. 



LAOPORUS NOBELI Lull 



Plate 5, fig. 2 ; plate 6 



Laoporus nobeli, Lull, Amer. Journ. Sci., Vol. 45, 1918, pp. 339-341, pi. 2, 

 text fig. 2. 



A beautifully preserved trackway (No. 11,148, U. S. N. M.) 

 from a level 150 feet above the base of the Coconino sandstone 

 (see pi. 5, fig. 2) is identified as pertaining to Laoporus nobeli Lull, 



'■ Marsh, O. C, Amer. Journ. Sci., Vol. 48, 1894, p. 82. 

 ^Lull, R. S., Amer. Journ. Sci., Vol. 45, 1918, pp. 339-341. 



