Fig. 12. Copy of Marsh's drawing of footprint of Thinopus antiquus, from the Devonian of Pennsylvania. × 1/3.
This still remains after nearly 20 years the only evidence of air-breathing vertebrates in the Devonian of the world.
Dromopus aduncus Branson.
Branson, Jour. Geol., XVIII, No. 4, pp. 356-358, fig. 1, 1910.
Type and other specimens in Oberlin College Museum.
Horizon and type locality: Near the bottom of the Hinton formation in Giles County, Virginia. ([Plate 18, fig. 3.])
The following description of the shales and footprints are from Dr. Branson's paper cited above:
"The Hinton shales, like the Mauch Chunk, seem to have been subaerial in origin and are made up for the most part of variegated shales interbedded with thin layers of argillaceous, fine-grained sandstone. The footprints occur in fine-grained sandstone, and remains of land plants are not uncommon in the same beds.
"Twenty-two footprints made by one animal walking in a straight course were collected in a slab. They give the impression of having been made by a bipedal animal for part of the distance, but after the fourth print of the right foot impressions of the forefeet appear. The hindfeet had 5 digits, the middle digit being longest and the 2 inside of it being only slightly shorter and lying close together. Their outer ends were slender and flexible and usually curved inward toward the middle toe. The 2 outer digits formed wide angles with the middle one and were shorter than the inner ones. The second toe was webbed to within 8 mm. of the tip, the third toe to within 23 mm. of the tip. The impression of the web is well preserved in only one impression of the hindfoot.