ON THE ANATOMY OF NYCTIBIUS WITH NOTES ONALLIED BIRDS.
By Alexander Wetmore,Of the Biological Survey, United States Department of Agriculture.The sternum and foot of the genus Nyctibius have been describedby P. L. Sclater/ and an account of the palate was given many yearsago by Huxley,2 but little has been published on the anatomy ofthe soft parts of these birds so far as is known. Through the cour-tesy of Dr. C. W. Richmond, acting curator in the Division of Birds.United States National Museum, the writer has been permitted todissect the body, preserved in alcohol, of the type-specimen of thePotoo described recently as Nyctihius gnseus ahhofti.^ This bird(Cat. No. 225851, U.S.N.M.), a male, was collected by Dr. W. L.Abbott at Port de Pimenti, northwest Hayti, on March 9, 1917.Though this specimen comprised the trunk and viscera alone, severalpoints of interest were brought out by critical examination. Anaccount of the dissections made is given in the following pages.The esophagus was contracted, and in this state had strong thick-ened walls, with the inner surface thrown into a series of longi-tudinal folds or rugae that expanded anteriorly to join the broadersurface of the pharynx. Apparently the esophagus was capable ofgreat distension in life, and the bird must have been able to swallowany object that could pass the opening guarded by the furculum andthe vertebrae at the anterior end of the body cavity. The proven-triculus was large and glandular, and the stomach proper was com-paratively thick walled and strong. This bird probably regurgitatespellets composed of chitinous fragments of insects and other in-digestible matter, as the pyloric opening of the ventriculus was toosmall to allow particles of any size to pass. In the present instancethe stomach contained insect jaws and other fragments too large topass through into the small intestine and too firm in texture topermit of trituration.
1 Notes upon the American Caprlmulgldae, Proc. Zool. Sec. London, 1866, pp. 123-130.
? On the Classification of Birds, Proc. Zool. Soc. London, 1807, p. 454.
? Richmond, C. W., Descriptions of two new Birds from Haiti, Smiths. Misc. Coll.,vol. 68, No. 7, July 12, 1917, p. 1.PROCEEDiNGS U. S. NATIONAL MUSEUM. VOL. 54?NO. 2251.3343?19?Proc.N.M.vol.54 38 577
578 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 54.The convolutions of the gut were of the isocoelous type. Whenremoved from the body and dissected out, a large duodenal loop (seefig 1) was found, in which the intestine was larger in diameter thanelsewhere. The remainderof the small intestine wasthrown out in one largeloop with three smallerdivisions indicated. Theremnant of the vitellineduct apparently was nearthe summit of the secondof these smaller divisions,but it could not be madeout exactly and the posi-tion assigned to it in theaccompanying figure issomewhat uncertain. Thecaeca were paired andmuch elongated. At theopen end each caecum wasslender, while for its pos-terior half each was muchdilated. The intestinewas somewhat narrowedat the point where thecaeca were given off, and then expanded into the rectum. Measure-ments of the intestine were taken as follows
:
Fig. 1.
?
Diagram of the intestinal convolutions inNyctibius griseus abbotti (about natural size), a,Remnant of vitelline duct.
Total length 250Distance from caeca to anus 30Length of caeca 42The liver (fig. 2) was bilobate, with the left division only aboutone-fifth the size of the right. The leftlobe was elongate and flaplike, and meas-ured 20 mm. long by 11 mm. wide. Theright lobe was somewhat triangular in out-line, with a broad, square-angled lowermargin. The width of this lobe decreasedtoward its anterior end, where it was moreor less squarely truncated. The externalmargin was straight and the internalborder, forming one side of the cavity toreceive the lower end of the pericardium,was sinuate. Through the center this lobewas 33 mm. long. The tips of the twolobes converged toward one another, though medially the right andleft divisions were separated by a comparatively broad space. At
Fig. 2.?Outline of liver lobesOF Nyctibius griseus abbottiFROM the ventral SURFACE(slightly less than NATURALSIZE), r, Right lobe; I, leftLOBE.
NO. 2251. THE ANATOMY OF NYCTIBIUS?WETMORE. 579the anterior end the two lobes were connected by a band of livertissue 7 mm. long. This band was broad where it joined the leftlobe, expanded by a rounded process on its lower margin, and thencontracted to a narrow neck to join the right lobe. The small sizeof the left liver lobe is unusual, as in allied forms concerning whichinformation or specimens are available (Podargus, Caprimulgus,Phalaenoptilus, Setochalcis, Nyctidromus, and Chordeiles) the leftlobe is much larger, being from one-third to more than one-half thebulk of the right hand division.A small elongate gall bladder similar to that found in other Capri-mulgi (including Chordeiles'^) underlaid the right lobe of the liver ina notch near the external margin. The pancreas was small, consistingof a single lobe that was rounded and full at the lower end, elongateand attenuate above. It was not possible to trace the hepatic andpancreatic ducts in this specimen to the point where they entered theintestine.The spleen was placed against the anterior end of the gizzard onthe right side, beneath the upper end of the right liver lobe. It waselongate with bluntly rounded ends, flattened somewhat from sideto side, but in general form was cylindrical. The spleen measured10 mm. long and the flattened face was 2.5 mm. broad.There was only one carotid artery, a character in which Nyctibiusresembles Podargus and differs from the Caprimulgidae. The leftcarotid passes up out of the body cavity, and then swings over torun on up the neck through the hypapophysial canal, as in aspecimen of Podargus strigoides (Cat. No. 19361, U.S.N.M.) ex-amined. In Nyctibius there is a small artery on the right side thatextends to the right thyroid gland. A branch of this artery thenproceeds inwards as a vertebral artery but extends no farther upthe neck.In the specimen of Nyctihius at hand the trachea was injured sothat a detailed study of it was not practicable. It was ascertained,however that the syrinx was tracheo-bronchial, in which characterthis genus resembles the Caprimulgidae.The sternum has been studied so no details of the trunk skeletonneed be given save to note that the procoracoidal process is small,not reaching the clavicle, and that there are 14 cervical vertebrae ofwhich three bear free ribs.There is some confusion in published accounts as to the numberof cervical vertebrae in this group. Beddard ^ states that Chordeilespossesses 13. Gadow^ gives 14 for Podargus and Batrachostomusand 13 for Caprimulgus. Fiirbringer * says that Caprimulgus has 131 Wetmore, Proc. Biol. Soc. Washington, vol. 28, 1915, pp. 175-176.2 Structure and Olassiflcatlon of Birds. 1808, p. 241. See also Oberholser, A mono-graph of the Genus Chordeiles, U. S. Nat. Mus. Bull. 80, 1914, p. 9.? Bronn's Klassen and Ordnungen des Thier-Reichs, Vogel, vol. 1, 1891, p. 950.* Untorsuchungen zur Morphologic and Systematik der Vogel, vol. 1, 1888, table 23.pp. 780-781.
580 PROCEEDINGS OF TEE NATIONAL MUSEUM. VOL, 54.and Batrachostomus 14. In the following table is given the numberof cervical and cervico-dorsal vertebrae (those possessing free ribs)and the number of complete ribs reaching the sternum in the speciesat hand at the present time:
List of soecies. Cervical
NO. 2251. THE ANATOMY OF NYCTIBIUS?WETMORE. 581
Fig. 3.?Tongue of Nyctib-lus griseu3 abbotti (x2.Cat. No. 225851, U.S.N.M.).
sharply pointed, but bend readily. The upper surface of tlie tongueappears smooth to the unaided eye, but when examined with a handlens it is found to have a few minute spines scattered over its sur-face. The tongue measured 20 mm. long andthe posterior prongs were 12 mm. apart.Examination of other species available be-longing to the suborder Nycticoraciae showsfour main types of tongue structure in thisgroup. The material available includes thefollowing: Steatornis caripensis^ Podargtisstrigoides, Nyctibius griseus, Cho7'deiles acufi-pennis, Chordeiles virginianus^ Phalaenoptilusnitidus, Nyctidromus alhicolUs, Caprimivlguseuropaeus^ and Setochalcis vocifera. The formof tongue peculiar to Nyctibius griseus has beendescribed above. Of the remaining forms Po-dargus (fig. 4) possesses a tongue most remark-able in form. This organ has been briefly de-scribed by Beddard^ as "a curious tough but transparent mem-branous organ," but no other reference to its peculiarities has beenfound in literature available. The tongue in Podargus is elongateand much larger in proportion to the size of the mouth cavity thanin other forms examined. The anterior endof the hyoidean apparatus forms a thickened,pointed projection in the tongue base, as shownby the line x in the text figure. Anterior tothis strong base the tongue is thin and trans-lucent, being not much thicker than a sheet ofordinary writing paper. The lateral outlinesof this portion are slightly convex, and aresomewhat irregular, due to wear of the thin,delicate margins. The tip forms an obtusepoint. At the base the tongue is dilated oneither side, and terminates in two pointed pro-jections. The margins of these projections arearmed with spinose papillae projecting back-GUS STEIGOIDES (ABOUT NAT- i , IX:' L J & ^URAL SIZE. Cat. No. 19361, ward, which continue around on the inner side.lo''.^L:i^'':.::Z These papillose points are not symmetricallySTRONG BASE AND THIN, PA- dcvelopcd ou the opposlug side. The base ofPEE-LIKE TIP. ^^^ tongue lies only a short distance in frontof the glottis. It seems questionable whether the thin anterior por-tion of the tongue can serve any purpose in feeding, although thatis a point to be settled only by observation of living specimens. The
Fig. 4.?Tongue of Podar-
1 Structure and Classification of Birds, 1898, p. 2.34.
582 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 54.tongue in Podargus strigoides is certainly one of the most curiousfound in the Class of Birds.The tongue of Steatomis caripensis (fig. 5) has been briefly de-scribed by Garrod.i In two alcoholic specimens in the UnitedStates National Museum collections the tongue is shaped like anarrowhead with a rather elongate bluntly pointed tip, convex lateraloutlines, and spreading, somewhat slender pos-terior processes that project beyond the hinderborder. The margins of these posterior proc-esses are armed with soft, slender, backwardprojecting papillae, and smaller papillae of thesame nature are found on the upper surfacesof these projections. The arrangement of thesepapillose points is not symmetrical and thetongue is somewhat thickened basally, becom-ing thin at the anterior end. In the specimenfigured (a male. Cat. No. 18309, U.S.N.M.) thetongue measured 19.5 mm. along the sides by12 mm. broa,d across the spreading base. TheseFig. 5.?Tongue of Stea.toknts caripensis (x2Cat. No. 18309, U.S.N.M.) measurements are slightly in excess of thosegiven by Garrod.The remaining genera examined all belong in the family Capri-mulgidae, and in all the tongue is small, more or less triangular inform, with the posterior lateral margins and upper surface armedwith papillae of varying sizes. Various modifications of this generaltype mark the different genera, as may be noted in the followingpages. Though the tongue is small in all these forms, it must beconsidered that it plays a definite part in manipulatingfood in swallowing; otherwise the development of thebasal papillae would be less marked.In a treatise on the anatomy of Phalaenoptilusthat species as " slender and pointed. Posteriorly it isnitidus Miss M. E. Marshall,^ describes the tongue ofbifid and fimbriated." In a specimen at hand thisorgan (fig. 6) is small, measuring 9.5 mm. long by3 mm. broad. The postero-lateral spinose processesare elongate and pointed. The lateral margins in out-line are approximately straight lines. Spinose, back-ward projecting papillae begin at a point anterior to the center andbecome stronger and heavier toward the base of the tongue. Theupper surface of the tongue for its basal two-thirds is thickly setwith small horny papillosities, all projecting backward. Because ofiProc. Zool. See. London, 1873, p. 531.2 A Study of the Anatomy of Phalaenoptilus Ridgway, Proc. Amer. Philos. Soc, vol.44, 1905, p. 215. (See pi. 4, fig. 10.)
Fig. 6.?TongueOF Phalaen-optilus NITID-US (X2. Cat-No. 19146, U.S.N.M.).
NO. 2251. THE ANATOMY OF NYCTIBIUS?WETMORE. 583the posterior elongation of the lateral processes, the basal marginappears deeply incised, in this respect exceeding any of the othergenera examined save Nyctidromus. The arrangement of the lateralpapillary processes is not bilaterally symmetrical.In a specimen of Nyctidromus albicollis the tongue is very similarto that just described and figured in Phalaenoptilus. Strong back-ward directed papillae are found on the lateral margins posterior tothe middle and the arrangement of the papillae on the upper surfaceis somewhat different than in Phalaenoptilus. A row of strongspicules, four or five in number is developed on either side, and atthe base the number of papillae is reduced to two or three. A slenderpapillus arising on the inside, at the tongue base, is about two-thirdsas long as the postero-lateral process. The margins of the latter aresmooth, and the processes are elongate as in Phalaenoptilus. Thetongue measures 10.5 mm. long by 2.5 mm. broad at the base.The tongue of Caprimulgus europaeus has been described brieflyby William MacGillivray ^ who notes (p. 634) that it "is ex-tremely small, slender, slightly papillate at base, having also somepapillae on its upper surface, tapering to an obtuse point." In aspecimen at hand (Cat. No. 19359, U.S.N.M.) the tongue resemblesthat of Phalaenoptilus nitidus, but has the postero-lateral spinesmuch less elongate. The tongue in this specimen measures 10 mm.long by 3 mm. broad at the base. In outline the lateral margins arenearly straight, so that in profile the tongue is like an elongatetriangle. Pointed papillae projecting backward begin on the mar-gins at a point anterior to the middle and continue to the base. Thelast in the series toward the base of the tongue are the largest.The postero-lateral spines are moderately elongate and there are noother projections from the posterior margin. Small scattered coni-cal papillae cover the posterior half of the upper surface. Towardthe base there is one row on either side of the center composed, re-spectively, of two and three papillae each that point in toward thecenter.The tongue of Setochalcis vocifera has likewise been described byMacGillivray 2 who notes that it is "slender, tapering to a point,very thin, with two long-pointed papillae at the base, and numeroussmall papillae on its upper surface." In specimens examined by thewriter the tongue in this species also resembles that described inPhalaenoptilus nitidus. In form it is slender and elongate with atriangular outline. One specimen seen (Cat. No. 223661, U.S.N.M.)is 10.5 mm. long by 3 mm. broad at the base. Spinose processesappear on the margin about one-half of the distance back from thetip; these increase slightly in size toward the posterior part of the
1 History of BriUsh Birds, London, vol. 3, 1840, pp. 630 and 634.2 Tn A.udubon, J. J., Ornitholigical Biography, Edinburgh, 1839, vol. 5, p. 306.
684 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 54.tongue. The postero-lateral spines are elongated as slender, pointedprocesses, and there are six or seven small backward-projectingpapillae on the upper surface of the tongue near the base. Thehyoidean muscles in this species are very slight in development.No alcoholic specimen of Antrostomus caroliTiensis is at hand, butthe tongue in this species (also described by William MacGillivray ^)is said to be " very small, * * * attenuated, tapering, flat above,covered with papillae, of which there is a large one at the base oneach side; the tip is narrow, but rather obtuse." No drawing show-ing the tongue is given, but from the description quoted it is evidentthat it resembles in general type the tongues of Phalaenoptilus^ Cap-rimulgus^ and Setochalcis.The tongue of Ghordeiles virginianus, while similar to that ofother Caprimulgidae, shows a slightly different development. Thisorgan in the nighthawk (fig. 7) is small in comparison to the sizeof the mouth opening, but is strong and heavy. It measures approxi-mately 9 mm. long by 4.7 mm. broad at the base, so that it is shortand broad in comparison with the lingual appendagesof other genera in this family that have been described.This difference was noted by MacGillivray^ in hisdissections of birds made for Audubon. In outlinethe tongue of Ghordeiles virginianus is triangular,/ \ with the lateral margins slightly concave. The pos-FiG. 7.?Tongue tero-lateral angles are produced as curved spinose proc-oF Ghordeiles esses, and the line of the base is incised at the center.(x2!^cat^no! '^^^ lateral margins of the tongue are armed with225265, U.S. spinosc papillae, which are small and weak anteriorlyand become strong and heavy toward the base.Stronger processes arm the posterior margin, and the broadenedbasal third of the tongue has its dorsal surface covered with pointed,harsh papillosites, all directed toward the pharynx. The hyoidianmuscles are fairly strong and well developed.In Ghordeiles acutipennis the tongue resembles that described inG. virgini-anus but is smaller, measuring only 7.5 mm. long by 4.5mm. broad at the base. The postero-lateral spines are somewhatlonger so that the posterior margin appears more deeply incised.The lateral outlines and the arrangement and size of the spines arepractically the same as in the larger nighthawk. The tongue is thesebirds, though small, appears so much stronger than in the otherCaprimulgidae and is so heavily armed with papillae that it mustbe supposed that it plays an important role in the swallowing of food.Certainly the development of spines is so striking that the tongue inthis genus can not be considered rudimentary or functionless.
1 Audubon, J. J., Ornithological Biography, Edinburgh, 1839, vol. 5, pp. 402-403.2 Idem, p. 407.
NO. 2251. THE ANATOMY OF NYCTIBIUS?WETMORE. 585The relationships of the goatsuckerlike birds of the groups char-acterized by the genera Podargics, Nyctibius, and Caprimulgus havebeen interpreted in various ways by different authors. Sharpe^placed Podargus in a suborder Podargi of the Coraciiformes, whilehe united Nyctibius^ which he considered as the type of a distinctfamily, the Nyctibiidae, with the Caprimulgidae in another suborder,the Caprimulgi. Beddard^ and Gadow^ on anatomical groundsjoined all these with Steatornis under one suborder known as theCaprimulgi.Mr. Ridgway* in his recent treatment of the group has proposeda suborder Nycticoraciae to include the superfamilies Caprimulgi(Caprimulgidae + Nyctibiidae), Podargi (Podargidae) and Steator-nithes (Steatornithidae).The grouping of Steatornis^ Podargus and its allies, Nyctibius, andthe various genera belonging to the Caprimulgidae in one suborderunder the Coraciiformes is one that seems logical in view of the factsknown through modern research into the affinities of these birds.Steatornis as an outlying aberrant form, though seeming to belongto this suborder, is so different from the other genera included in theNycticoraciae that it is readily separated from them in a well cir-cumscribed division, and may be dismissed without further comment.A survey of the facts now known concerning the anatomy of Nycti-bius, however, together with the structural characters of this genuspreviously recorded, serve to show that the gap between the two re-maining superfamilies recognized by Mr. Ridgway is less trenchantand sharply defined than has been supposed. In the following tableare given the details of 12 of the main structural characters of use inthe classification of the members of this group remaining afterSteatornis is removed.
Oil glandPowder down patches .
.
Carotid arteriesSyrinxLeft liver lobeTongue
Cervical vertebrae ......SternumProcoracoidal process. .Basipterygoid processesPalatinesNumber of phalanges infourth toe.
Podargus.
AbsentPresentOne (left)BronchialMore than one-half aslarge as right.Large, with transparentpaperlike tip, spinosebasally.13Four notchedLarge, reaching furcu-lum and scapula.AbsentBroad throughout,slightly expandedposteriorly.Five
Nyctibius.
AbsentPresentOne (left)Tracheo-bronchialOne-flfth as large asright.Medium, shaped like aspearhead, feebly pa-pillate.14Four notchedSmall, not reaching fur-culmn.PresentNarrow anteriorly,greatly expandedposteriorly.Five
Caprimulgidae.
Present.Absent.Two.Traeheo-broncliial.One-tliird to one-halfas large as right.Small, triangular inoutline, more or lessspinose.14.Two notched.Small, not reachingfurculum.Present.Narrow anteriorly,greatly expandedposteriorly.Four-.
1 Review of Recent Attempts to Classify Birds, 1891, pp. 79, 81.? Structure and Classification of Birds, 1898, pp. 231-244.? Classification of Vertebrata, 1898, pp. 36-37.* Birds of North and Middle America, Bull. 50, U. S. Nat. Mus., part 6, 1914, pp.487-489.
586 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 54.It will be noted that in five of the characters outlined, NyctiMusagrees with the Podargidae, and in five with the Caprimulgidae. Inthe absence of an oilgland, presence of powder down patches, singlecarotid artery, four notched sternum, and the possession of fivephalanges in the fourth toe Nyctibius resembles Podargus (heretaken as typical of the family Podargidae). While in its tracheo-bronchial syrinx, 14 cervical vertebrae, presence of basipterygoidprocesses, development of the procoracoidal process, and the form ofits palatines Nyctibius is similar to the Caprimulgidae. It is seenfrom a study of these points then, that, as Gadow stated,^ theNyctibiidae seem to form an intermediate group between the othertwo. Study and comparison of the known characters of Aegotheleswhich forms another family of this group, the Aegothelidae, servesto narrow the gap between Podargidae and Caprimulgidae stillmore.^ , It is thought that the two major groups will be found stillmore closely allied when more is known of Aegotheles, and whenBatrachostomus has been more carefully investigated. From presentknowledge Batrachostomus seems to belong in the family Podargidaeas it is said to have a four-notched sternum, a bronchial syrinx, anda desmognathous palate, while it lacks basipterygoid processes. Itdiffers from Podargus in possessing an oil gland.From the facts outlined above it seems that the suborder Nyctico-raciae of the Order Coraciiformes may be divided into two super-families, the Steatornithoidae with the single genus Steatornis andthe Caprimulgoidae with the families Podargidae, Nyctibiidae,Aegothelidae, and Caprimulgidae. In the second superfamily thePodargidae, though specialized, are considered lowest and the Capri-mulgidae highest in development. The Nyctibiidae and the Aegothe-lidae seem to be about on the same level, though on the whole the lat-ter seems the more primitive.
1 Bronn's Klassen und Ordnungen des Thier-Reichs, Vogel, vol. 2, p. 243.2 As alcoholic specimens or skeletons of Aegotheles are not available, the writer isindebted for information on this genus and on Batrachostomus to the following : Bed-dard, Structure and Classification of Birds, 189S, pp. 231-244 ; Gadow, Bronn's Klassenund Ordnungen des Thier-Reichs, Vogel, vol. 2, pp. 242-243 ; to brief notes gleaned fromother sources, and to such characters as are available from the study of skins.