TRANSACTIONS

ON THE DISCOVERY OF A FOSSIL BIRD-TRACK IN THE DAKOTA SANDSTONE.

BY PROF. F. H. SNOW, OF THE UNIVERSITY OF KANSAS

              During the past two years Mr. E. P. West has been assisting the writer in the collection of geological specimens for the University cabinets. In the month of August, 1885, he was so fortunate as to discover, near Thompson's creek, in Ellsworth county, Kansas, a single well-marked impression, which I believe to be a genuine bird track. The piece of rock containing the impression was picked out from a pile of material which had been removed from a well excavation 44 feet in depth. This well was sunk in the Dakota sandstone, and the geological horizon of the bird track is about 200 feet below the upper level of the Dakota rocks. The horizon of the bird track appears to be identical with that of a fine series of dicotyledonous leaves obtained on Thompson's creek, at a distance of about a mile and a half from the well.

toe just reaching the ground at its extremity, as in the modern snipes and other wading birds, or in the family of sea-gulls and terns. That the track is probably that of the right foot, rather than the left, is indicated by the wider separation of the outer toe from the middle toe, resulting from the greater versatility of the outer toe as compared with the inner toe – a character illustrated in many families of existing birds, and carried to an extreme in the cuckoos and the woodpeckers, in which the outer anterior toe is entirely reversed in its direction and becomes a backward-pointing member.

           It will be seen, from the accompanying cut, that our bird track exhibits the imprint of all four of the toes. The outer anterior toe is represented for fully two-thirds of its length. The middle and inner anterior toes are entirely impressed, even to the claws at their extremities -the claw being very distinctly marked upon the middle toe. The ball of the foot has left a very deep impression, and the posterior toe has made an unmistakable imprint upon the sand similar to those made at the present time by birds whose hind toes just reach the ground. That this impression is avian in character, rather than reptilian, is evident front the imprint of the hind toe, for no dinosaur or other reptile, either recent or extinct, is known to have a backwardly directed toe. Some dinosaurs have a fourth small or rudimentary anterior toe, but in no case has a posterior toe been discovered. The absence of the impression of a posterior to in the so-called bird tracks of the Connecticut river Triassic sandstone has led the best authorities to consider those tracks reptilian rather than avian. The small size of our Dakota track is a confirmatory indication of its avian character. It measures only two inches from anterior middle claw to claw of posterior toe, being a little larger than the foot of Prof. O. C. Marsh's Ichthyornis victor as restored by him in his famous monograph of the Odontornithes. The restoration of the foot of Ichthyornis, however, was based upon a single phalangal bone, the only portion of the foot yet found, the rest of the skeleton of the foot having been restored in exact imitation of a living species of tern, which among recent birds Ichthyornis seems most closely to resemble.

material for Marsh’s magnificent work upon the “Toothed Birds.” This is the highest group represented in Kansas, the Benton and the Dakota lying beneath it. The Dakota rests uncomformably upon the Permo-Carboniferous rocks with apparently an entire exclusion of the Triassic and Jurassic formations. The evidence of the existence of bird-life is thus extended down from the highest to the lowest division of the Kansas Cretaceous, and if Professors Mudge and St. John are correct in maintaining the absence of the Triassic and Jurassic formations in our State, this evidence cannot be extended lower down in Kansas, unless we admit the somewhat suggestion that the class of birds existed in Paleozoic time.

            The discovery of this Dakota bird-track enables us to supply an important element hitherto lacking in that earliest of Cretaceous eras. The wonderful luxuriance of the land vegetation of the Dakota and its marvelous similarity to the dicotyledonous forest growths of the warm temperate climes of the present day, have rendered these sandstone beds a most fascinating field of investigation for both Paleo-botanists and Neo-botanists. The finely developed and perfectly preserved foliage of Oaks, Willows, Poplars, Laurals, Sarsaparillas, Magnolias, Sassafras, and other kindred forms belonging to genera now long extinct, have hitherto suggested a beauty of landscape whose perfection was only marred by the apparent scarcity of animal forms. It is true that these fossil leaves give abundant evidence that the vegetable kingdom was subjected in those ancient times to the attacks of injurious insect. But our imaginations require the presence of more conspicuous animal forms to harmonize with the extremely luxurious development of vegetable life. Our bird-track supplies the missing element of graceful aërial forms. From the size of the footprint it may be safely inferred that the bird which left it was somewhat larger than a pigeon. It was probably a bird with teeth, in that respect resembling its predecessor the European Archæopteryx of Jurassic times and its successors of the Middle Cretaceous, the Hesperornis and the Ichthyornis of the Niobrara Group. If our Dakota bird was an Ichthyornis, as is by no means improbable, its habits were doubtless similar to those of the modern Tern.

            Prof. Marsh writes of the Ichthyornis that “its sharp cutting teeth prove beyond a doubt that it was carnivorous. Its great powers of flight, long jaws, and its recurved teeth , suggest moreover that it captured its prey alive. Its food was probably fishes as their remains are found in great abundance mingled with those of Ichthyornis. Besides Ichthyornis and its allies, the only other denizens of the air at present known to have inhabited the same region were the toothless Pterodactyls. The Ichthyornis doubtless competed with these huge dragons for the fishes in the tropical ocean about which they lived.”

            The distribution of land and water in Kansas during the formation of the Dakota sandstones was of such character as to favor the belief that our bird was either a wading-bird, or allied to Ichthyornis and the modern Terns. The occurrence of the fossil leaves in  restricted areas shows that the land was in the form of islands of limited extent, while the marine character of the fossil shells indicates that these islands were surrounded by a salt-water ocean.

dawn to dewy eve” they were incessantly upon the wing, exhibiting a dash and buoyancy of flight unknown to other birds. In the protection of their eggs and young they exhibited unmistakable promptness and valor, swiftly descending along graceful but vigorous curves to a perihelion point in uncomfortable proximity to the face and eyes of the intruding naturalist.

            The birds of the Dakota period were doubtless even more active than the Terns of the present day. The probable presence of teeth in their jaws was an advantage evidently employed with disastrous effect not only to the fishes which constituted their food, but also to their rivals and enemies – the flying reptiles without teeth. The later were overcome in conflict, and teeth were no longer a necessity to birds.

.... (portion removed)

     In the Transactions of the Kansas Academy for 1888, p. 3, Prof. F. H. Snow described more fully and figured a footprint from the Dakota as follows: ²⁸

     "During the past two years Mr. E. P. West has been assisting the writer in the collection of geological specimens for the University cabinets. In the month of August, 1885, he was so fortunate as to discover, near Thompson's creek, in Ellsworth county, Kansas, a single well-marked impression, which I believe to be a genuine bird track. The piece of rock containing the impression was picked out from a pile of material which had been removed from a well excavation forty-four feet in depth. This well was sunk in the Dakota sandstone, and the geological horizon of the bird track is about 200 feet below the upper level of the Dakota rocks. The horizon of the bird track appears to be identical with that of a fine series of dicotyledonous leaves obtained on Thompson's creek, at a distance of about a mile and a half from the well.

     "The impression appears to have been made by the right foot of some bird with elevated hind toe just reaching the ground at its extremity, as in the modern snipes and other wading birds, or in

28. On the Discovery of a Fossil Bird Track in the Dakota Sandstone.

WILLISTON.]                        Birds                                               53

the family of sea-gulls and terns. That the track is probably that of the right foot, rather than the left, is indicated by the wider separation of the outer toe from the middle toe, resulting from the greater versatility of the outer toe as compared with the inner toe, a character illustrated in many families of existing birds, and carried to an extreme in the cuckoos and the woodpeckers, in which the outer anterior toe is entirely reversed in its direction and becomes a backward-pointing member." (See opposite page.)

     "It will be seen, from the accompanying cut, that our bird track exhibits the imprint of all four of the toes. The outer anterior toe is represented for fully two-thirds of its length. The middle and inner anterior toes are entirely impressed, even to the claws at their extremities -the claw being very distinctly marked upon the middle toe. The ball of the foot has left a very deep impression, and the posterior toe has made an unmistakable imprint upon the sand similar to those made at the present time by birds whose hind toes just reach the ground. That this impression is avian in character, rather than reptilian, is evident front the imprint of the hind toe, for no dinosaur or other reptile, either recent or extinct, is known to have a backwardly directed toe. The small size of our Dakota track is a confirmatory indication of its avian character. It measures only two inches from anterior middle claw to claw of posterior toe, being a little larger than the foot of Prof. O. C. Marsh's Ichthyornis victor as restored by him in his famous monograph of the Odontornithes."

     The slab on which were the prints described by Mudge was left at the Agricultural College. In the general neglect of Mudge's collection after his connection with the Institution ceased, the specimen has been lost. The specimen described by Snow is now preserved in the University of Kansas Museum. The description and figure given by Snow describe the specimen sufficiently well. I agree with him in his conclusions. The print is in all probability that of a bird.

     A CRETACEOUS BIRD-TRACK.-Professor F. H. Snow has recently, in the Trans. Kansas Acad. Sciences, described a fossil bird-track discovered in the Dakota sandstone, in Ellsworth county, Kansas. The impression appears to have been made by the left foot of some bird with an elevated hind-toe just reaching the ground. The ball of the foot is deeply impressed and the posterior toe has made an unmistakable imprint, proving: the avian character of the footprint. It measures two inches from anterior middle claw to claw of posterior toe. This discovery considerably lowers the geological horizon of Kansas birds, since nearly all the material for Marsh's Toothed Birds was obtained from the Niobrara, the highest group of the Cretaceous represented in Kansas. Below this lies the Benton, followed by the Dakota, resting unconformably on the Permo-Carboniferous rocks.

     Professor Snow continues thus: "The wonderful luxuriance of the land vegetation of the Dakota, and its marvellous [sic] similarity to the Dicotyledonous forest-growths of the warm- temperate climes of the present day, have rendered these sandstone beds a most fascinating field of investigation for both Paleo-botanists and Neo-botanists. The finely-developed and perfectly-preserved foliage of oaks, willows, poplars, laurels, sarsaparillas, magnolias, sassafras and other kindred forms belonging to genera now long since extinct have hitherto suggested a beauty of landscape whose perfection was only marred by the apparent scarcity of animal forms. Our bird-track supplies the missing element of graceful aerial forms. From the size of the footprint, it may be safely inferred that the bird which left it ,vas somewhat larger than a pigeon. It was probably a bird with teeth," "with habits similar to those of the modern tern."