524 BULLETIN 5 0, UNITED STATES NATIONAL MUSEUM 



= Pandionidae Gadow, in Bronn's Thier-Reich, V6g., ii, 1891, 159, 300. — 

 Oberholser, Outl. Classif. North Amer. Birds, 1905, 2. 



Strictly piscivorous long-winged Accipitres with outer toe reversible, 

 claws long, very strongly curved, of equal length, and contracted and 

 rounded on under surface; tarsus very stout, covered with small rough, 

 somewhat imbricated, projecting scales; under surface of toes covered 

 with prominent spicules, and plumage of thighs very short, dense, and 

 compact. 



Skull essentially Buteoninc (most resembling that of Elan aides) but 

 descending process of lachrymal firmly and cntu^ely blended with the 

 ectethmoid and without any backwardly projecting frontal portion, 

 and superciliary process of lachrymal exceedingly small and short 

 (more so even than in Elanoides) ; anterior orifice of eustachian tube 

 entirely closed; coracoids overlapping at sternum (as in Ardeidae, etc., 

 but as in no other Accipitres) ; upper portion of tarsometatarsus with 

 a bony ring, through which passes the common tendons of the toes 

 (as in Striges) ; outer (fourth) toe reversible (as in Striges) ; claws very 

 long and very strongly curved, acute, of equal length, contracted 

 toward their lower surface, where smooth and rounded in transverse 

 section; deep plantar tendons of type XI (Coraciine), blending com- 

 pletely (as in Striges, Bucerotidae, etc.), the area of fusion ossified; 

 tendons of biceps split for nearly entire length; tensores patagii pecul- 

 iar; cervical vertebrae, 15; caeca large; plumage in general dense, 

 compact, and hard, that of upperparts with feathers distinctly out- 

 lined (squamate), that of underparts more blended, that of thighs 

 very short, dense, and compact.®^ 



In matters of pterylosis the Panchonidae agree with the Cathar- 

 tidae, and not with either the Accipitridae or the Falconidae.^* 



The Pandionidae agree with the Accipitridae but differ from all the 

 Falconidae in possession of the following characters. 



Palate indu'ectly desmognathous ; vomer not separated anteriorly, 

 not closely applied to maxilla-palatines; squamosal prominence not 

 strongly developed; ventral suface of maxilla without median bony 



'^ It has been stated that Pandion lacks aftershafts to the contour feathers; 

 but according to W. DeW. Miller (Bull. Amer. Mus. Nat. Hist., xxxiv, 1915, 139, 

 140) there is "a perfectly distinct aftei'shaft with stiff, elastic shaft, on feathers 

 of the interscapulars, rump, and crissum," although "the plumage of the under- 

 parts in general has no aftershaft." 



" Compton (Univ. California Publ. Zool., xlii, No. 3, 1938, 173-212) has amply 

 demonstrated the remarkable similarity in the pterylosis of the Pandionidae and 

 the Cathartidae. He suggests, on the strength of these data, that the Pandionidae 

 should be placed in the suborder Cathartes. It seems better, however, in view of 

 the closer agreement between the ospreys and the Falcones in other characters, 

 to keep them in the latter suborder, but to place them as a separate family of that 

 series, as is done here. 



