4 p. : ill. ; 24 cm.Includes bibliographical references

Cockerell, Theodore D. A. (Theodore Dru Alison), 1866-1948.

American Museum of Natural History Scientific Publications

AMERICAN MUSEUM NOVITATESNumber 62 March 16, 192356.85.D(1181 :78.8)THE SUPPOSED PLUMAGE OF THE EOCENE BIRDDIATRYMABY T. D. A. COCKERELLPlumage, the unique possession of birds, dates back to at least theUpper Jurassic. It is so v~ell developed in the Archaxopteryx of that erathat we may reasonably expect to find it considerably earlier, shouldthere exist a deposit capable of preserving recognizable traces of it.According to Petronievics, the specimens of supposed Archaeopteryx inthe British and Berlin Museums represent different genera, not merelyspecies as Dames had maintained. It appears that the Berlin specimenmust take the name Archaxornis siemensii (Dames), and in certaincharacters it is said to approach the carinate type, while the BritishMuseum example shows more ratite features. As the genus Archeopteryxwas based by Meyer (1861) on a feather, it appears to be somewhathazardous to identify it with one or another of the well-preserved formsand, according to the facts given by Lydekker ('Cat. Fossil Birds,' p.362), the British Museum specimen seems to be entitled to the nameGriphosaurus problematicus.In the light of these facts, and in consideration of all we know aboutMesozoic birds, we have little ground for considering any Tertiary ormodern bird primitive on account of its lacking the power of flight orpossessing hair-like feathers. Even, in the Cretaceous, certain birdswere so far advanced that Shufeldt has not hesitated to refer one of them(Graculavus lentus Marsh) to the modem genus Pedioecetes, judging fromthe distal end of a tarso-metarsus. In the heading of his account (Trans.Conn. Acad., XIX, p. 25) he actually calls it P. phasianellus (L.), but thetrue purport of the observations below would be better indicated bycalling it Pedioecetes (?) lentus. As Matthew and Granger indicate, it ishardly to be doubted that the discovery of the whole skeleton wouldcompel us to recognize a perfectly distinct genus. Nevertheless, mod-ernization and differentiation had gone far by the time we come to theEocene and, as regards the feathers, there was probably no strikingadvance remaining to be made. The promise of the future was ratherin the development of the voice and in arboreal and nest-building adapta-tions and developments. Even the mechanism for maintaining a hightemperature must have been already perfected.2 AMERIdAN MUSEUM NOVITATESIn the midst of this rather orderly and consistent developmentcertain extraordinary types appear, both in the living and extinct faunas.They do not represent the expectations of orthogenesis and must beregarded as specially adapted forms, made, like the caricatures of thecartoonist, by exaggerating certain features to the point of grotesqueness.Such a bird is the Diatryma of the Wasatch, fully elucidated from a mag-nificent specimen by Matthew and Granger (Bull. Amer. Mus. Nat.Hist., XXXVII, pp. 307-326). Of the four species ascribed to Diatryma,only D. steini is known by the major part of the skeleton. The others arerepresented by very imperfect fragments of the feet. Nothing has beenknown of the plumage but, although the authors (p. 309) suggest that thebird is closest to Cariama, the very convincing restoration by Mr.Erwin S. Christman (P1. xxxiii) shows hair-like plumage like that of acassowary.The vicinity of Roan Creek in western Colorado has long beenknown to palaeontologists on account of the discovery of numerous fossilinsects, ascribed to the Green River Eocene. It is a region of high mesasor hills, separated by gigantic valleys, which have not yet been accu-rately mapped, topographically or geologically. The enormous exposuresare all in the Eocene, apparently Wasatch at the bottom of the valleysand Green River at the top. Before going there I was prepared to be-lieve that the shales ascribed to the Green River were not really con-temporaneous with the typical beds in Wyoming; but the longer oneworked in them the closer seemed to be the resemblance to the genuineGreen River deposit, and no hesitation remains in ascribing the wholeseries to a single epoch. Granting this, it is of course still true thathorizons will have to be elucidated and will probably show marked differ-ences in theiy contents. The good fossiliferous levels in the Roan Moun-tains are high up, but some distance below the tops of the mesas. Incertain places they are indeed on top, but this occurs on spurs from themain elevations which have been worn down to a lower level. Thefossil-bearing beds are known as the oil shales, and the hard gray rock willburst into flame when placed on a fire. At very numerous places assess-ment holes have been dug and, although it is doubtful whether the moneythus invested will be recovered, the palaeontologist finds most of hisheavy work done for. him and has only to pick up and split the shale uponthe dumps. Now indeed is the golden time to collect fossils in this area,as in five yeasr time the exposed shales will have crumbled to dust and itis not probable that the digging of holes will continue indefinitely.[No'. 6219231 PLUMAGE OF THE EOCENE BIRD DIATRYMAABFig. 1. Feathers from the Eocene.A, Contour feather of unknown bird.B, C, Plumage of Diatryma (?) fihifera.Passing up the old Ute trail above Seller's Ranch, a mile or morebefore reaching the Osborn cabin, there is a considerable excavationwhich we designated Station No. 1. The holes, blasted out in successiveyears, are like so many gigantic steps on the side of the mountain, theuppermost practically on the top. Later on it will be possible to describeC3AMERICAN MUSEUM NOVITATESthe fossil insects and plants taken from this location. Among otherthings, we found a typical contour feather of a bird, perhaps the oldestordinary feather known (Fig. 1). At the lowest hole, which was ingeneral unproductive, Mrs. Cockerell was so fortunate as to find longstrands of plumage which look as if they might have come from the veryDiatryma figured by Mr. Christman.. Repeated study, with lens andmicroscope, shows that they are not vegetable fibres, nor are they mam-malian hairs. They are not filoplumes, according to Chandler's ('AStudy of the Structure of Feathers, with Reference to their TaxonomicSignificance,' Univ. of Calif. Publ., Zool., 1916) definition, but are likethe very slender simple feathers of the Casuariformes, particularly thecassowary. Chandler says of the cassowary:The naked terminal portion of the feather, which sometimes constitutes three-fourths of the entire feather and reaches a length of over 20 cm., sometimes has thestiff bristle-like naked barbs present in decreasing numbers all the way to the tip,where there are only two or three per centimeter on each side, while in other cases,especially in shorter feathers, the naked shaft is produced as a very coarse, stiffbristle.The fossil plumage now described had a length of fully 20 cm., prob-ably much more. It was apparently very dark, appearing black upon thestone. It was soft and wavy, not bristly. All the filaments appear to beperfectly simple. The average filament has a diameter of about 65 ,u;but there also occur slender, pale brown ones only half as wide. Thesurface mottling resembles that in Chandler's figure of Casuarius. Inplaces the filaments are bent instead of curved. There is no resemblanceto the plumage of Cariama, but, as compared with the cassowary, theplumage seems to have been even more filiform, more delicate and soft,less bristly.Among the known Eocene birds, this could only have come fromDiatryma. The horizon is considerably higher than any known for thatgenus and no doubt a different species' at least, is concerned. Until weknow more about the matter, this plumage may be designated Diatryma(?) fflifera, new species.4 [No. 62

Plumage of the Eocene bird Diatryma

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