MORPHOMETRICS OF FLIGHTLESSNESS IN THE ALCIDAE

BRADLEY C. LIVEZEY Museumof Natural History,University of Kansas,Lawrence, Kansas 66045 USA

ABSTRACT.--Datacollected from skin specimensof the 23 Recentspecies of Alcidae,skeletal material for Recentand fossilalcids, and publisheddata on body massand wing area were usedto describethe morphometriccharacteristics of flightlessnessin the GreatAuk (Pinguinus impennis)and the fossil mancallineauks. A regressionequation confirmed a body-masses- timate (5 kg) for P. impennis(Bfidard 1969). The size and relatively small wings produced wing-loadingsof roughly 22 g.cm-2, comparableto thoseof medium-sizedpenguins. Multi- variate analysisof external measurementsunderscored the uniquely large size, relatively short wings, and moderatelydeep bill of Pinguinuscompared to other Recentalcids. Analysis of skeletal measurementsrevealed that the genera of flightlessAlcidae (Pinguinus,Mancalla, Praemancalla,and Alcodes)were characterizedby relatively short distal wing elementsand dorsoventralflattening of all majorwing elements,in combinationwith relatively large core and pelvic dimensions.These differenceswere most pronouncedin Mancalla,moderately developedin Praemancalla,and smallestin Pinguinus.Estimated body mass (1-4 kg) for selected fossil mancallinesexceeded the largest flighted alcids (Uria) but was lessthan for Pinguinus. Pinguinuswas a comparativelylarge piscivoresharing many morphologicalfeatures with the Razorbill (Alca torda)and tourres (Uria spp.). Its flightlessnessevidently was a consequence of extremespecialization for pursuit diving, convergentwith that of the Spheniscidae.Loss of flight imposedsignificant requirements on breeding sites and foraging habitatsof the GreatAuk and presumablythe mancallines,and renderedPinguinus exceptionally vulnerable to human exploitation.Received 30 December1987, accepted 23 May 1988.

THE Great Auk (Pinguinusirnpennis), a flight- Blanc 1927, Storer 1945, Miller and Howard 1949, less alcid of the North Atlantic, is remembered Verheyen 1958).Even compilationsof standard most for its extinction in the 19th century. This external measurements for the Great Auk are is understandable, for the demise of the Great not available (cf. Coues 1868, Forbush 1912). Auk remains one of the most dramatic extir- The situationis relatedto the rarity of skin spec- pations in historicaltimes, one related to hu- imens and the variable distribution of the abun- man exploitationfor food (Grieve 1885,Nettle- dant skeletal material of Pinguinusin museums. ship and Evans1985) and possiblyto long-term The fossil flightless mancalline alcids of climatic trends (Bengtson 1984). Superstition coastalCalifornia are morphologically similar also took a toll: the last Great Auk taken in Great but less well known. Hundreds of elements of Britain reportedly was killed as a tempest-con- the group have been recovered,and 8 species juring witch (Ley 1935, Greenway 1967). The in 3 generaare recognizedfrom the late Mio- extermination of the specieswas complete by cene through the early Pleistocene:Praeman- 1844 (Greenway 1967), despite the prediction callalagunensis, P. wetrnorei, Mancalla californiensis, of this eventuality in the late 18th century(Net- M. diegensis,M. rnillerLM. cedrosensis,M. ernlongL tleship and Evans 1985). and Alcodes ulnulus (Lucas 1901; Miller 1933; Flightlessnessof the Great Auk, traditionally Howard 1947, 1966, 1968, 1970, 1971, 1976, 1978, less compelling to ornithologiststhan the de- 1982, 1983; Miller and Howard 1949; Olson 1981; mise of the species,is of comparableimportance Howard and Barnes1987). The Miocene genus to evolutionarybiology. Although the flightless Praemancallais considered to be a possible conditionof Pinguinuswas noted frequentlyby ancestorof the largely Pliocenegenus Mancalla early naturalists,particularly with respectto its (Howard 1966, 1976.) Neither genus is thought vulnerability to hunterson land, the anatomical to be closely related to Pinguinus.The Pacific correlatesof flightlessnessin the GreatAuk have generagenerally are placedin a separatefamily received relatively little attention. Existingan- or subfamily (Howard 1966, 1983) and may be atomical studies consistof basicdescriptive os- relatedmost closely to the puffins(Fraterculini; teology(Owen 1879,Wiman and Hessland1942) R. M. Chandlerunpubl. data). Pinguinus isjudged and limited mensural comparisons(Lucas 1890, to be closelyrelated to the Razorbill (Alca torda)

681 The Auk 105: 681-698. October 1988 682 BRADLEYC. LIVEZE¾ [Auk,Vol. 105 and murres (Uria spp.) on behavioral and mor- Cullen !982; Murray et al. !983; Dunning !984). Wing phologicalgrounds (Storer 1945,Strauch 1985). areas were traced (Raikow !973), from fresh birds or Alcids are wing-propelled diving birds. thawed, fresh-frozen specimens, and the resultant Strokesof the partly folded wings provide vir- areaswere measuredwith a compensatingpolar pla- nimeter.Additional wing areaswere taken from Mag- tually all of the propulsion and much of the nan (!9!2, 1922),Poole (!938), Kuroda(!967), Spring maneuverability for submarine locomotion (!97!), Stempniewicz(!982), and Pennycuick(!987); (Townsend 1909, Kelso 1922, Storer 1945). several tracings were provided by R. M. Chandler. Structuralconvergences between the GreatAuk Wing-loadingwas calculated as the ratio of body mass and the similarly flightless, wing-propelled divided by total wing area (g.cm-2;Clark !97!). penguins (Spheniscidae)have receivedconsid- Associated skeletal material of the Great Auk is not erable attention (e.g. Owen 1879,Wiglesworth available. One possible exception is an apparently 1900,Storer 1945). Aerial flight and submarine complete,largely articulatedskeleton of an immature propulsion clearly impose different selective bird at the British Museum. Mounted skeletons of Pinguinusare compositesof unassociatedskeletal ele- pressureson alar structureand the morphology ments. Extensive series of disassociated skeletal ele- of Pinguinusreflects the evolutionary substitu- ments are held at the U.S. National Museum of Nat- tion of aerial flight for extreme specialization ural History, AmericanMuseum of Natural History, for diving (Wiglesworth 1900;Bent 1919;Storer and Museumof ComparativeZoology (Harvard Uni- 1960, 1971;B•dard 1969;Bengtson 1984). Man- versity). Anatomical nomenclature follows Baumel callawas probably at least as specializedosteo- (!979). logically for diving as Pinguinus(Wiman and I soughtto measureat least 40 unworn specimens Hessland 1942, Miller and Howard 1949, How- of eachmajor skeletal element of P. impennis.The more ard 1970). fragile scapula,furcula, and distal phalangeswere not I comparedflightless and flighted alcids,em- availablein suchnumbers. Comparable data were col- phasizingmultivariate morphometric analyses. lected from all available material of Mancalla, Prae- mancalla,and Alcodes.Limited mensural data also were Data from study skins and skeletonsof all 22 collected from a new speciesof Mancalla (here re- extant alcid species,the Great Auk, and the fos- ferred to as Mancallalg. sp.; Chandler unpubl. data) sil mancalline auks were included. My objec- and Australcasp. (Brodkorb !955, Olson !977). Pin- tives were: to describequantitatively the mor- guinusalfrednewtoni, a poorly represented Pliocene form phological characteristicsassociated with loss similar to P. impennisin its measurements(Olson !977), of flight in the Alcidae; to estimatethe body was excludedfrom study.I alsosampled !0 complete massof adequatelyrepresented mancalline auks; skeletons (5 of each sex) of each of the 22 extant and, using available ecological and biogeo- speciesof alcid, although completesamples were not graphicalinformation, to considerselected as- available for severalspecies (e.g. Cepphuscarbo, Syn- pectsof the evolutionof flightlessnessin alcids. thliboramphuswumizusume, Aethia pygmaea). Forty-six skeletal measurementswere employed, most of which were describedpreviously (Livezey METHODS and Humphrey !984, !986) and !! of which were illustrated by Spring (!97!; measurements2, 6, 7, 12, Specimensand related data.--I collecteddata from 1! 13, !4, !6, 38, 39, 40, 4!). All skeletal measurements mounted skin specimensof the Great Auk. In addi- were made with dial calipers to 0.! mm. Sexual di- tion, colleaguesprovided comparabledata from an morphismwas consideredto be smallin extantspecies additional!4 mountedPinguinus skins (see Acknowl- of alcid (Storer!952), and in this studysexual differ- edgments).At least20 study skins(usually !0 of each enceswere found to be negligible.This similarity of sex) of each of the 22 extant speciesof Alcidae were the sexes,and the lack of information on sexfor spec- sampledfor comparisons.I measured total length (ex- imens of Pinguinusand the fossil species,prompted tended specimensonly, from bill to tail, feet exclud- the pooling of the sexesin the morphometric com- ed), culmen length (exposed,on midline), bill height parisons. (at gonys),wing length (chord of unflattened wing), Statisticalanalyses.--Linear measurements and log- tarsuslength (cranial surface),digit-III (middle-toe) transformed(base e) wing-loadings and skeletalratios length (excluding nail), and tail length (roedial arc) were comparedusing analysisof variance (ANOVA) (Baldwin et al. 193!). and analysisof covariance(ANCOVA). Spearmancor- Data on body massof extant alcids were collected relation coefficients(r) were used to measurebivariate from specimen labels and published compilations associations. (Johnson!935, !944; Belopol'skii!96!; B•dard !967, Allometry of bodydimensions, i.e. the relative rates !969; Kuroda !967; Dement'ev and Gladkov !968; Sea- of size changeamong variables, was quantified using ly !976; Threlfall and Mahoney !980; Vermeer and bivariate allometric equations (Gould !966). I based October1988] Flightlessnessin the Alcidae 683

these estimateson linear regressionson log-trans- were mutually orthogonal). Despite this sacrificeof formed data, using "geometricmean" estimatesto orthogonality,this approachwas preferable to a stan- accommodateerror in both variables (Livezey and dard PCA. It produceda virtually isometric"size" Humphrey 1986). axisfor PC-I*, defineda singleimportant "shape" PC- Stepwiselinear regressionsof log-transformeddata II* for alcidsgenerally (using completeskeletons), were used to estimate the body mass of P. impennis andisolated the morphometricchanges associated with based on speciesmeans of external measurements of flightlessnesson separateaxes (PC-III* and PC-II*, skins.Body mass of fossilMancalla and Praemancalla for completeand reduceddata sets,respectively). To- was estimated from stepwise regressions of log- tal variancesincorporated on the standardprincipal transformedbody mass on significantlycorrelated (P componentsand correspondingmodified compo- < 0.05) principal componentsof available skeletal nents were virtually identical. The standardPCs ex- measurements.Components were derived from co- ceeded the modified axes by less than 0.05% of the variance matricesbased on log-transformeddata. total variance in the subspacesdiscussed. For external measurements that involved associated I usethe term "size" in its traditionally broadsense, measurements for samples of skins of Great Auks, i.e. in referenceto spatial extent or dimension. Var- canonicalanalyses of log-transformeddata for Recent iousmeasures of "size," none perfectfor all purposes, speciesof alcid were used.Canonical analysis (CA) is emerged from the morphometric comparisons;and a multivariate technique that is robust to moderate rationalesfor consideringthem as representativeof departuresfrom the assumptionsof multivariatenor- "size" are given. Correlationsbetween mean body mality and homogeneityof covariancematrices of mass (using log-transformeddata) and these emer- groups.CA providesmultivariate axes that maximally gent "size" measuresare probably the most useful discriminatepredefined groups (Pimentel 1979).CAs direct measure of overall size (Clark 1979), and are were also used for interspecificcomparisons of as- given to facilitate interpretation.I estimateddiver- sociated measurements of humeri, ulnae, and sterna. gencesbetween multivariate "size" axesand hypo- Variablesincluded in eachCA were backstep-selected theticalaxes of isometricsize using direction cosines from the complete suites of measurementsusing between vectors (Pimentel 1979). F-statistics (P < 0.05). For CAs of skins and separateskeletal elements, I usedprincipal component analyses (PCAs) of mean specimenslacking a minority of measurementswere measurementsfor the speciesof flightlessauks (sexes subjectedto missing-dataestimation. Missing data pooled)to assessmultivariate skeletal variation among were estimatedfrom stepwise regressionson avail- taxa. Componentswere extractedby singular value ablemeasurements for specimensgrouped by genus. decompositionsof covariancematrices based on log- Theseestimates comprised 0.9% of the skin and 1.5% transformed data. Pinguinusand the extant Alcidae of the skeletal data sets. were comparedusing 46 skeletal measurements,and Statisticalprocedures used were part of the Biomed- a reduced data set of 23 measurements was used to ical Computing Programs(Dixon 1985) and per- includefossil species in the comparisons.Because of formedon an IBM computerat the Universityof Kan- poor representationof the similarly sized Mancalla sas. californiensis,M. cedrosensis,and M. diegensis,the three specieswere pooled to derive a single mean vector RESULTS representing"medium-sized" Mancalla. My primary objectivesfor the PCAs were to determine the multi- EXTERNAL CHARACTERS variateaxis or axesof changesassociated with flight- Univariate comparisons.--External measure- lesshess,and to determine the relative positionsof flightlessspecies on the major axesof variation for ments demonstratethe substantially larger size alcidsgenerally. The flightlessspecies, because of their of the Great Auk comparedwith other Recent large size and exceptionalshape, acted as influential alcids (Table 1), including the large extant pi- outliers in the definition of axes in normal PCAs. This scivorousgenera Cepphus,Uria, and Alca. Alca seriouslyconfounded "size" with the shapecorrelates is considered to be the closest extant relative of of flightlessnesson PC-I and adverselyaffected the Pinguinus(Storer 1945,Strauch 1985). Pinguinus definition of subsequentaxes. Therefore, ! excluded sharedwith Alca its deep, laterally compressed the flightless speciesfor the definition of the first bill and, despiteits much larger body size, had principalcomponent. The flightlessspecies were pro- wing lengths comparableto those of Cepphus jected onto this PC-I a posteriori,and the residualsfor (Table 1). all specieswere subjectedto another PCA to extract the subsequentaxes. I refer to these modified com- Despitethe thousandsof Great Auks slaugh- ponents as PC-I*, PC-II*, and PC-III*. Becausethe tered during the eighteenth and nineteenth flightlessspecies were not used in the derivation of centuries,the only putativedatum for body mass PC-I* but were consideredin subsequentcompo- was the report by Feilden (1872) of a Pinguinus nents, the latter axeswere correlated with PC-I* (but killed in 1808 which weighed nine Danish 684 BPotr)i,E¾C. LIVEZE¾ [Auk,Vol. 105

T^I•I,Ii 1. Externalmeasurements (mm, g) of three flighted alcidsand the Great Auk (œ+ SD [n]).

Total Total Culmen Bill Wing Tail Tarsus Middle-toe Species length mass' length height length length length length Cepphus 309 + 18 427 30.6 + 1.4 7.3 + 0.6 159 + 5 46 + 3 32.7 + 1.4 36.4 + 1.6 grylle (20) (155) (20) (20) (19) (20) (20) (20) Uria aalge 423 + 25 1,030 44.9 + 1.7 13.3 + 0.8 200 + 6 44 + 3 38.7 + 2.1 43.8 + 2.5 (20) (613) (20) (20) (20) (20) (20) (20) Alca torda 403 + 29 722 34.7 + 1.7 21.9 + 1.7 197 + 10 79 + 7 33.7 + 1.6 41.9 + 2.3 (20) (217) (20) (20) (20) (20) (20) (20) Pinguinus 786 + 58 [5,000] 84.7 + 4.3 39.3 + 2.4 160 + 9 73 + 13 59.6 + 11.2 70.2 + 5.1 impennis (24) (25) (25) (23) (17) (22) (24) Means basedon publisheddata and specimenlabels; standard deviations not available.Mass of Pinguinusestimated (see text). pounds (4.5 kg). B•dard (1969) estimatedthe though the remigeswere substantiallyshorter body massof Pinguinusto be "c. 5000 [g]" but than in extant species. provided no details concerning this estimate. I Wing areasof 10 flighted speciesof the AI- attemptedan independentapproximation of the cidae are available, and the resultant estimates massof Pinguinusfrom a regressionequation of wing-loading closelymirrored the negative that related body massto six non-alar external allometry of wing length with body size. This measurementsfor the 22 extantspecies of alcids, relationship produced progressivelygreater using log-transformedmeans. I excludedwing wing-loadings as body massincreased. Wing- length becauseits relationshipto body size is loadings were, from smallest to largest mean obviouslyatypical in Pinguinus.Despite the small body mass(n = sample sizes for wing areas): number of data (n necessarilybeing 22), all six Aethiapusilla, 0.71 (n = 2); Alle alle, 0.94 (113); remaining variables entered significantly (P < Synthliboramphusantiquus, 1.02 (2); Aethia crista- 0.10). The resulting regressionmodel was: tella, 1.32 (1); Cyclorrhynchuspsittacula, 1.11 (1); Cepphuscolumba, 1.23 (1); Fraterculaarctica, 1.34 (21); Alca torda, 1.63 (4); Uria lomvia, !.69 (2); and M = -7.909 + 2.344(TOTLEN) U. aalge,2.06 (20). The allometriccoefficient for + 0.991(LDIGIT3) - 0.325(LTARSUS) wing area on body massfor flighted alcidswas - 0.508(LTAIL) + 0.172(HTBILL) • = 0.632 (SE [•] = 0.003;regression significant, - 0.121(LCULMEN). P < 0.001; R2 = 0.99), significantly less (P < 0.00!) than that for isometryof wing areawith The variablesare listed in order of entry into body mass(b = 0.667). The estimatedwing area the model;adjusted R: for the model was 98.8%. for Pinguinuswas 230 cm2, based on the doubled Substituting log-transformed mean measure- areaof a tracing of a partially folded wing that ments for the Great Auk into this equation (Ta- was "corrected"graphically to approximatean ble 1) and taking the antilog provided an esti- extendedwing. Togetherwith the 5-kg estimate matedbody massof 4,999 g, almostidentical to for body mass,this indicatesthat the wing-load- the value of B&dard (1969). ing of Pinguinuswas roughly 22 g-cm-2. This Relativewing size.--The extremely small rel- estimate was much higher than one from an ative wing lengthsof Pinguinuswas conspicuous allometric extrapolationof a "flighted" alcid to in a bivariateplot of wing lengthson bodymass a body massof 5 kg, which yielded a wing- for 23 speciesof alcids,using the estimatedbody loading of 3.26 g.cm-2. This projection,and the massof 5,000 g for Pinguinus(Fig. 1). The allo- empirical estimate of 22 g-cm 2 for Pinguinus, metric coefficient for the flighted species,• = exceed the threshold of flightlessnessof 2.5 0.322 (SE [•] = 0.001), was significantlyless (P g.cm 2 hypothesizedby Meunier (!951). < 0.001) than the coefficientfor isometry be- Multivariatepatterns.--A CA of the external tween a linear variate with mass (b = 0.333). measurementsfrom 481 skin specimensdefined The relatively shorter wings of Pinguinusre- three important axes of interspecificvariation. tained the 10 functional primary remigestyp- All seven variables entered the model signifi- ical of the Alcidae (6 specimensexamined), al- cantly (P < 0.001),and provided highly signif- October1988] Flightlessnessin the Alcidae 685

TABLE 2. Standardized coefficients and associated statistics for canonical variates of seven external measurementsof 23 alcid species(n = 481).

Canonical variate i c...... Character I II III Total length -0.26 0.24 -0.31 Culmen length -0.64 0.48 -0.34 Bill height -0.25 -0.99 0.15 Wing length - 0.18 0.39 0.97 Tail length -0.11 -0.17 0.07 Tarsuslength -0.03 0.24 -0.18 Middle-toe length -0.27 -0.24 -0.12 Fig.1. Logof themean body mass and wing length Eigenvalue 152.6 26.5 13.2 of the 23 Recentspecies of alcid.Regression line (Type- Variance (%) 73.3 12.7 6.4 II) was fitted for 22 flighted species,and massof Pin- Canonical R 1.00 0.98 0.96 guinusimpennis was estimated.The abscissawas bro- ken to accommodatePinguinus.

mediate on CV-II, with a score similar to those icant discriminationof the 23 Recentspecies of of Alca, Ptychoramphus,and Alle (Fig. 2). alcid (Wilks' lambda < 10-7; df = 7, 22, 458; P The third variate (CV-III) reflected "relative •<: 0.001)All pairwise interspecificdifferences wing length" (Table 2), and once again under- were significant(P < 0.001). scoredthe unique body form of Pinguinuscom- The first canonical variate (CV-I) had coeffi- pared to other Recent alcids. The highly sig- cients of like sign for all measurementsand nificant interspecific differences in scoreson reflectsin large part "general size," although CV-III (F = 295.1; df = 22, 458; P < 0.0001) the relatively great contribution of culmen resulted largely from the extremely low mean length and small contributionsof tail and tarsus scoreof Pinguinus,and reflected its relatively lengths resulted in an approximate 35ø diver- short wings (Fig. 2). Of the 22 flighted species, gencefrom isometry.Mean scoreson CV-I were only the two endomychurine Synthliboramphus strongly correlatedwith mean body mass(r = and Aethiapusilla showed any tendency toward -0.91 for flighted species,r = -0.95 including relative shortening of the wing. estimatedmass for Pinguinus).CV-I incorporat- ed almostthree-fourths of the total interspecific SKELETAL CHARACTERS variance (Table 2), and scores on the axis dif- fered significantlyamong species(ANOVA of Univariatecomparisons of species.--Mostskel- scores;F = 3177.6; df = 22, 458; P < 0.0001). etal measurementsalso reflected the large size Small species(e.g. Aethia,Alle, Brachyramphus) of Pinguinus(Tables 3, 4). Exceptfor distal wing were scoredhighly on this axis (reflecting the elements,Pinguinus exceeded all other Alcidae, negativecoefficients), whereas species with large Mancalla and Praemancalla, in its skeletal di- overall size (Uria, Fratercula,and especiallyPin- mensions.Measurements of the trunk and leg guinus)had low scores(Fig. 2). demonstratedthe differencemost clearly, e.g. The second most important axis (CV-II) was tibiotarsi of Pinguinusaveraged 4 cm (45%) lon- in large part a measureof "relative bill height," ger than thoseof Uria aalge(Table 4). Although with a lesser, correlated contribution from the humeri of Pinguinuswere the longest in the lengths of the tail and middle toe (Table 2). Alcidae, they averaged only 22% longer than Interspecificdifferences in scoreson CV-II were those of Uria. That is, the relativelength of the highly significant(F = 551.6;df = 22, 458; P < humerusof Pinguinuswas lessthan in Uria,Alca, 0.0001). Specieswith relatively deep bills and, and Cepphus,but was approachedby those of to a lesserextent, relatively long tails and mid- Mancalla and Praemancalla(Tables 3, 4). The ten- dle toes (e.g. Fratercula,Cyclorrhynchus, Aethia) dency toward alar shortening in the flightless had low scoreson CV-II, and groups with op- auks is more pronouncedin the mid-wing ele- positeproportionalities (e.g. Uria, Cepphus)had ments, especially lengths of the radius, ulna, high scores(Fig. 2). The Great Auk was inter- and carpometacarpus,which were absolutely 686 BP,ADEE¾ C. LIVEZE¾ [Auk,Vol. 105

• 5 • • • •0

I•rge "general body s•e" small CANONICAL VARIATE [

•. 2. •[ot o• mean sco•eso• 23 spedeso• a[dd on the fi•t 3 canonicalradiates based on seven external measurements.•[i•hted speciesa•e n•mbe•edas •oHows: (]) AZZ•,JJ•, (2) AJc,tor•,, (3) Urm (5) C•h,s c,r•o,(6) C. col,m•,, (7) C.•ryJJ•, (8) Br,chyr, m•h,s •r•rostr•s, (•) •. marinorates,(]0) a•t•s, (]]) S. crn•H, (•2) S. hy•oJ•c•s,(13) S. •m•z•s•m•, (]&) P•ychor,m•h,s ,J•,•c,s, •s•ttac•Ja,(16) A•t•n cr•statdJa,(17) A. •s•JJa,(18) A. •y•maca,(]9) C•ror•ca mo•oc•rata, (2•) •. cor•c,J,t,, and (22) •.

shorter in Pinguinusthan in the much smaller (Table 3), as demonstratedby their compara- Uria (Table 3). Reductionsin the lengthsof the tively large maximal widths (MWMs). An AN- mid-wing elements were even greater in Prae- COVA of "relative flatness" (ratios of maximal mancalla and Mancalla. and least shaft widths) confirmed these shape Greater shaft widths also characterized the differences in humeri (F = 84.8; df = 6, 113; P wing elements of the three flightless genera < 0.001) and ulnae (F = 24.1; df = 6, 120; P <

TABLE3. Summarystatistics (œ ñ SD In]) for selectedmeasurements of major skeletalwing elementsof three flighted and 6 flightlessalcids. MWM = maximal width at midpoint.

Humerus Ulna Carpometa- Species Length MWM Length MWM carpuslength Cepphusgrylle 59.6 +__1.6 4.4 _+0.2 51.4 _+ 1.7 4.2 _+0.3 34.0 _+1.3 (1•) (11) (11) (11) (11) Uria aalge 87.3 _+2.4 7.9 _+0.5 65.9 ñ 1.6 6.3 _+0.3 43.3 -+ 2.8 (12) (12) (12) (12) (12) Alca torda 75.5 _+ 3.0 6.9 _+ 0.3 60.1 _+ 2.6 5.8 -+ 0.3 40.2 _+ 1.8 (10) (10) (10) (10) (10) Pinguinusimpennis 106.1 ñ 7.3 12.3 ñ 0.7 57.4 ñ 1.8 8.6 ñ 0.4 42.7 _+ 1.4 (69) (69) (59) (59) (59) Mancalladiegensis 72.9 _+6.9 9.7 _+ 1.0 29.3 _+ 1.7 6.0 _+0.6 35.7 -+ 2.4 (12) (15) (15) (15) (7) M. cedrosensis 71.7 ñ 2.3 9.6 ñ 1.3 30.0 _+ 1.0 6.2 ñ 0.3 35.8 (2) (2) (9) (9) (1) M. milleri 63.0 _+ 2.8 8.3 ñ 0.8 26.4 ñ 1.3 5.5 -+ 0.4 31.6 _+ 1.7 (18) (24) (21) (21) (12) M. emlongi 87.1 _+4.4 11.3 _+0.1 -- -- 40.6 -+ 1.1 (2) (2) (2) Praemancallaspp. 78.0 _+5.3 9.8 _+1.1 40.6 ñ 5.2 7.3 _+0.0 36.3 (4) (5) (2) (2) (1) October1988] Flightlessnessin the Alcidae 687

TABLE4. Summarystatistics (œ + SD [n]) for lengthsof two trunk and three leg elementsof three flighted and six flightlessalcids.

Sternal carina Coracold Femur Tibiotarsus Tarsometa- Species length length length length tarsuslength Cepphusgrylle 81.2 + 3.0 30.4 + 0.9 36.2 _+ 1.0 64.5 + 1.9 31.3 _+ 1.2 (11) (11) (11) (11) (11) Uria aalge 122.5 + 5.8 40.1 + 1.1 47.8 + 1.5 91.1 + 2.9 38.0 + 1.3 (12) (12) (12) (12) (12) Alca torda 108.7 + 2.8 36.3 + 1.2 41.2 + 1.9 76.1 _+ 1.4 33.2 + 1.0 (10) (10) (10) (10) (10) Pinguinusimpennis 189.7 + 11.3 60.3 + 2.8 73.0 + 2.4 132.8 + 4.6 52.2 + 1.8 (28) (62) (62) (62) (60) Mancalla diegensis -- 47.8 + 4.6 52.3 + 5.5 89.3 + 8.7 41.4 + 2.7 (6) (3) (7) (5) M. cedrosensis -- -- 54.8 87.0 41.2 (1) (1) (1) M. milleri -- 42.8 + 5.1 48.3 + 2.9 78.4 + 4.5 35.2 + 2.3 (6) (8) (S) (10) M. emlongi -- 58.6 65.7 + 2.3 -- 47.3 (1) (3) (1) Praemancallaspp. -- -- 68.8 108.0 47.6 (1) (1) (1)

0.001). This "flattening" of the wing bones in lengths and maximal shaft widths of humeri, flightless auks also was confirmed by an AN- i.e. measured "relative shaft width" (Table 5). COVA of maximal shaft widths (MWMs) for the Speciesdiffered significantly in scoreson CV- species tabulated (excluding the inadequate II (F = 135.6; df = 8, 115; P < 0.0001). Those samplesof M. emlongiand Praemancalla),while with comparativelynarrow humeri (Uria, Alca, correctingfor interspecificdifferences in lengths and Cepphus)scored highly; P. impenniswas in- of elements, for both the humerus (F = 194.6; df = 6, 113; P < 0.001) and ulna (F = 334.2; df = 6, 120; P < 0.001). TABLE5. Standardizedcoefficients and summarysta- Canonicalanalyses of singleelements.--Separate tistics for canonical variates of humeri, ulnae, and sterna of selected Recent and fossil alcids. CAs of humeri, ulnae, and sterna of flightless and selectedflighted alcids permitted a multi- Element Variable CV-I CV-II variateassessment of morphologicaldifferences among a maximal number of taxa (Fig. 3). The Humerus Length -0.55 1.01 (n = 125) Head width -0.18 -0.12 CA of 125 humeri of 10 speciesof alcid incor- LWM 0.06 0.11 poratedall four measurementssignificantly (P MWM -0.50 - 1.08 < 0.001), and effectively discriminatedthe six Eigenvalue 36.7 9.1 adequatelysampled species (Wilks' lambda = Variance (%) 77.4 19.2 Canonical R 0.99 0.95 0.0009; df = 4, 5, 113; P < 0.001) and five ad- Ulna Length 1.19 0.15 ditionally plotted taxa (Australcasp., Mancalla (n = 13i) LWM 0.02 -0.15 cedrosensis,M. emlongi,M. lg. sp., Praemancalla MWM -0.55 -0.98 spp.).The first axis (CV-I) reflectedthe lengths, Eigenvalue 125.8 13.7 head widths, and maximal shaft widths of hu- Variance (%) 90.0 9.8 Canonical R 1.00 0.97 meri (Table 5), and interspecific differences in scoreswere significant (F = 518.6; df = 8, 115; Sternum Carina length -0.44 1.14 (n = 43) Basinlength -0.54 -0.79 P < 0.0001). Specieswith large measurements Least width -0.34 -0.39 had low scores(P. impennis),smaller speciesin- Caudal width 0.15 -0.52 curred higher scores(Cepphus grylle), and the Eigenvalue 86.5 3.4 remaining taxa (e.g. Alca, Uria, and Mancalla) Variance (%) 94.9 4.8 Canonical R 0.99 0.89 were intermediate (Fig. 3A). CV-II contrasted 688 BRADLEYC. LIVEZE¾ [Auk,Vol. 105

(Australca, Alcodes, Praemancalla) which were representedby smallsamples (Fig. 3B). The three variablesentered the model significantly(Table 5; P < 0.001) and contributed to two axes in- corporatinginterspecific differences in scores; (ANOVA of scores;F = 1669.8 and 213.2, re- spectively;df = 8, 122; P < 0.0001). CV-I con- trastedlengths and maximal shaft widths of the ulna (Table 5). Mancalla had short, wide ulnae and hence low scores,Praemancalla and Pingui- nuswere intermediate,and the three flighted genera and the fossilAustralca had high scores which reflectedtheir comparativelylong, slen- der ulnae (Figs. 3B, 4). The vertical axis (CV-II) implied residual robustnessof the ulnar shafts, which was greatest in the stout bones of Pin- (C)Sterna __••-A/c..,•,•o guinusand progressivelyless so in Mancallaand the flighted genera(Fig. 3B). Sterna of the Great Auk, similar in overall conformation to that of Uria (Pinguinusillus- Fiõ. 3. ?lotsof first 2 canonJ.cal ¾ariates for flight- trated in Eyton 1875,Wiman and Hessland1942; less and selectedfliõhted alcids of: (A) 4 measure- Uria in Kuroda 1954), were contrasted with those merits of humeri, (B) 3 measurementsof ulnae, and of three flighted speciesof alcid using a CA of (C) 4 stemal measurements.Polyõons connect ex- five measurements, four of which entered the treme individuals in each taxon. model significantly(P < 0.01;Table 5). No ster- num of the fossil specieswas preserved ade- termedlate; and the mancallines had the broad- quately for analysis.The resultantCA signifi- est humeral shaftsand lowest scores(Figs. 3A, cantly differentiated the four species(Wilks' 4). The undescribed,large Mancalla ("M. lg. sp.") lambda = 0.003; df = 4, 3, 39; P < 0.001). CV-I closelyresembled Pinguinus in its humeral di- for sternaessentially ordinated the taxaby gen- mensions.A third variate (CV-III, not figured) eral sternal size, exclusive of caudal width contributed only 3% of total intergroup vari- (Table 5). Taxa differed significantlyon this axis ance,but provided significantinterspecific dif- (F = 864.1; df = 3, 39; P < 0.0001), and the low ferences in scores (F = 30.0; df = 8, 115; P < scoresfor Pinguinuson thisaxis reflect their large 0.0001). CV-III primarily separatedAlca, Uria, sterna(Fig. 3C). CV-II contrastedcarina length and M. millerifrom Cepphus,Pinguinus, and the with the remaining sternal dimensions (Table larger mancallinesby relative leastshaft width 5). Scoresdiffered among taxa (F = 43.7; df = and relative head width. 3, 39; P < 0.0001), and indicated that Alca and A CA of ulnae of selectedalcids significantly Uria slightly exceededPinguinus and Cepphusin separatedthe seven speciesanalyzed (Wilks' "relative carina length" (Fig. 3C). lambda = 0.0004; df = 3, 6, 121; P < 0.001); an PCA of completeskeletons.--A modified PCA additional three taxa were plotted on the axes of mean vectors of 46 skeletal measurements

Fig. 4. Illustrationsof majorwing elementsof (A) Alca torda(Univ. S. Florida4358), (B) Pinguinusimpennis (U.S. Nat. Mus. 1285,Los Angeles County Mus. 90055,90057), and (C) Mancalladiegensis (San Diego Nat. Hist. Mus. 24868, 21044, 28603, 25002); dorsal views of left elements in probable positionsused in submarine propulsionwith diagramsof mean intra-alar skeletal proportions(H = humerus,U = ulna, C = carpometa- carpus,M = proximal phalanxof digiti majoris,not illustrated).Note the comparativelygreat extensionof distal elements(positions inferred from qualitativeosteology) and dorsoventralflattening of alar elements in flightlessPinguinus and Mancalla;Mancalla is further derived in the proxi.malposition of the processus supracondylarisdorsalis or "ectepicondylarprocess" (ep), shortening of thef•rewing, and curvature of the humerus. October1988] Flightlessnessin the Alcidae 689

I 10M I 20c I •1u I •9H

B

ep

I I0M I 19c I 25u I 46H %1

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iMi C I U I H 12 22 19 4? %1 690 BRADLEYC. LIVEZEY [Auk,Vol. 105

TABLE6. Correlation coefficientsof 46 original skeletal variableswith first (modified) principal component (PC-I*, see text), and the first and secondprincipal componentsof the residualvariance from PC-I* for 23 Recentalcids (PC-U*, PC-III*). Signs to right of coefficientsfor PC-III* indicate variables so correlated with residuals from PC-I* (Irl >- 0.20).

PC- PC- PC- PC- PC- PC- Variable I* II* III* Variable I* II* III* Bill length 0.95 0.30 -0.48 Tibiotarsuslength 0.98 -0.03 -0.52 - Cranium length 0.99 0.18 -0.48 LWM 0.97 -0.08 -0.54 - Height 0.95 0.07 -0.59 - Tarsometatarsuslength 0.89 -0.11 -0.42 Width 0.96 0.0! -0.50 APW 0.96 -0.07 -0.54 - Humerus length 0.99 0.!5 -0.39 + LMW 0.94 -0.!! -0.6! - Head width 0.99 0.10 -0.39 + Digit III, Ph. ! length 0.96 -0.!3 -0.5! - LWM 0.98 0.08 -0.37 + Ph. 2 length 0.98 -0.08 -0.50 MWM 0.96 0.35 -0.51 - Ph. 3 length 0.95 -0.15 -0.55 - Radiuslength 0.92 -0.02 -0.15 + Scapulalength 0.98 0.24 -0.44 LWM 0.98 0.!1 -0.33 + Blade width 0.9! 0.29 -0.61 - MWM 0.99 0.21 -0.52 - Coracoldlength 0.99 0.02 -0.50 Ulna length 0.92 -0.02 -0.!4 + Basalwidth 0.95 0.36 -0.41 LWM 0.99 0.!3 -0.37 + Sternalcarina length 0.93 0.44 -0.44 MWM 0.99 0.!8 -0.46 + Basinlength 0.98 0.20 -0.51 - Carpometacarpus Least width 0.98 0.2! -0.39 + length 0.95 0.06 -0.2! + Caudal width 0.95 0.05 -0.38 + APW 0.98 0.13 -0.35 + Carina depth 0.97 0.!4 -0.53 - DVW 0.98 0.!6 -0.33 + Furcula height 0.97 -0.06 -0.55 - Digit II, Ph. ! length 0.97 0.07 -0.29 + LWM 0.96 0.29 -0.46 Ph. ! MWM 0.97 -0.0! -0.33 + MWM 0.93 0.40 -0.47 Ph. 2length 0.95 -0.0! -0.26 + Synsacrumlength 0.98 0.2! -0.50 - Femur length 0.96 -0.15 -0.54 - Interacetabularwidth 0.89 0.07 -0.40 Head width 0.97 -0.11 -0.57 - LWM 0.98 -0.04 -0.55 - Eigenvaluea 3.90 0.!2 0.06 MWM 0.99 0.!2 -0.53 - Percentageof variance 9!.9 2.8 !.9

aEigenvalues and percentagesof varianceinclude contributions from all 23 species;variance shared between PC-I* and PC-II* attributedto PC-I*.

(seemethods) concisely summarized the multi- PC-II* contrastedbill length and the size of the variatedifferences among Recent species (Table pectoral girdle with the pelvic limb. Genera 6, Fig. 5). The first three componentstogether characterizedby long bills and robust pectoral incorporated 96.7% of the total interspecific girdles relative to their leg measurements(e.g. skeletalvariation. Loadings of variableson the Brachyramphus,subgenus Endomychura of Synthl- first component(PC-I*) were all positiveand iboramphus)had high scoreson this axis, and of high magnitude(r -> 0.89, 38 r, -> 0.95), and genera with oppositeproportions (e.g. Aethia, identifiedPC-I* as a measureof "generalskel- Cyclorrhynchus)had low scores(Fig. 5). Pinguinus etal size" (Table6). Scoreson this component was moderatelyhigh in this dimension,as were were highly correlatedwith mean body mass Uria and Alca. (r = 0.99 for extantspecies, r = 0.98 including The third modified component(PC-III*) sum- estimate for Pinguinus),and the axis deviated marized the unique morphometric character- fromstrict isometric size by only8 ø . Smallspecies isticsof Pinguinusimpennis relative to other Re- (e.g.Aethia, Alle, Synthliboramphus) had low scores cent alcids, notably the skeletal correlatesof in PC-I*, whereasthe largesttaxa (Uria, Pin- flightlessness(Fig. 5). This axis contrastedleast guinus)had the highestscores (Fig. 5). shaft widths and lengths (to a lesser extent) of The secondaxis (PC-II*) for completeskele- wing elements,and widths of the sternumwith tons was a shape variable, characterizedby cranial height, maximal shaft widths of the hu- loadingsof varyingmagnitude and sign(Table merus and radius, scapularblade width, basin 6). Bill length, maximal humeral shaft width, length and carina depth of the sternum, most sternal carina length, and widths of the cora- dimensionsof the pelvic limb, and synsacrum coidand furculahad relativelylarge loadings, length (Table 6). The large negative score for whereasdimensions of leg elements,especially Pinguinusrevealed that, comparedwith flighted lengths,had negativecorrelations with PC-II*. alcids, the Great Auk had flattened humeri and October1988] Flightlessnessin the Alcidae 691

Fig. 5. Trivariateplot of meanscores of Recentspecies of alcid on first 3 (modified)principai components of 46 skeletalmeasurements; PC-III*, the axiswhich separatesPinguinus from flighted alcids,is explainedin text. Flighted speciesare numbered as in Fig. 2.

radii, was (slightly) shortenedin the mid-wing mancallaand Pinguinuswere progressivelylarg- and manus, and had comparatively large leg er (on this axis)than any flighted alcid (Fig. 6). elements(except tarsometatarsus length), broad The second component (PC-II*) contrasted scapulae,long and narrow pelvises,and sterna lengthsand leastshaft widths of wing elements that were long and narrow with relatively deep (especially humeri and radii) with maximal carina.Although none approachedthe extreme widths of wing elements,lengths and widths position of Pinguinuson PC-III*, the Dovekie of leg elements,and synsacrumlength (Table (A. alle) and puffins (Cerorhinca,Fratercula) had 7). This axis correspondedclosely with PC-III* the lowest scoreson this axis of the flighted for completeskeletons (Table 6). The 4 flightless Alcidae (Fig. 5). speciesor species-groupshad extremely low PCA of reducedskeletal vectors.--A PCA of scoreson PC-II*, whereas the flighted alcids mean vectors for the reduced data sets for "me- varied little in this dimension. The low scores dium-sized" Mancalla, M. milleri, Praemancalla of the flightlessspecies reflect their relatively spp.,and 23 Recentspecies identified two major short, flattened wing elements, and their rela- axes of skeletal variation. Together, these ac- tively long leg elements and long synsacra. countedfor 96.1%of the interspecificdispersion Scoreson PC-II* indicate that, of the flightless in the reduced morphometric space (Table 7). genera,Mancalla was most extreme in thesepro- As in the PCA of completeskeletal vectors, PC- portions, Praemancallawas next most distinc- I* of the reduceddata set largely reflected "gen- tive, and Pinguinuswas the leastmodified in this eral skeletalsize" (Table 7). Mean body mass dimension (Fig. 6). wasstrongly correlated with scoreson this com- Estimatedbody massesof mancallineauks.- ponent (r = 0.99 for flighted species,r = 0.98 Regressionsof total body mass on principal including the estimatefor Pinguinus),and the componentsof mean skeletalmeasurements for axisdeviated from strict isometricsize by only Recentalcids (including the estimatedbody mass 5ø. PC-I* indicatedM. milleriwas comparablein of 5 kg for Pinguinusimpennis) provided esti- "generalskeletal size" to Alca;the medium-sized mates of body massesfor selectedfossil man- Mancalla spp. were similar to Uria; and Prae- calline species.For each taxon, principal com- 692 B•DLE¾C. LIVEZE¾ [Auk,Vol. 105

TABLE 7. Correlation coefficients of 23 skeletal vari- small. "general skeletal size"-- ableswith first(modified) principal component (PC- I*, see text) and the first principal componentof the residual variance from PC-I* for Recent and fossilalcids (PC-II*). Signsto right of coefficients of PC-II* indicate variables so correlated with re- siduals from PC-I* (Irl > 0.20).

Variable PC-I* PC-II* Humerus length 0.99 - 0.42 + Head width 0.99 -0.41 + LWM 0.98 -0.39 + MWM 0.94 -0.55 - Radius length 0.94 -0.14 + LWM 0.98 - 0.35 + MWM 0.98 - 0.55 - Ulna length 0.93 -0.14 + Fig. 6. Plot of mean scoresof Recentand selected LWM 0.99 - 0.40 + fossilalcids on first 2 (modified)principal compo- MWM 0.99 - 0.48 nents of 23 skeletalmeasurements. Flighted species Carpometacarpuslength 0.96 -0.23 + are numbered as in Fig. 2; "medium" Mancalla rep- APW 0.97 -0.35 DVW 0.98 -0.35 + resentsmean vector for pooleddata of similarlysized Femur length 0.97 -0.51 - M. californiensis,M. cedrosensis,and M. diegensis. Head width 0.98 -0.56 - LWM 0.99 -0.57 - DISCUSSION MWM 0.99 -0.57 - Tibiotarsuslength 0.99 -0.54 - LWM 0.98 -0.56 - Locomotorcompromise and convergence.--The Tarsometatarsuslength 0.91 -0.50 - Alcidae are morphologically committed to a APW 0.97 -0.56 - largely aquatic existence.The compromisein LMW 0.94 - 0.54 - wing shapenecessary for wing-propelled div- Synsacrumlength 0.97 -0.55 - ing is substantial(Storer 1960, 1971; Pennycuick Eigenvaluea 2.23 0.22 1975, 1987), and in flighted alcids is associated Percentageof variance 87.6 8.5 with their comparativelyheavy wing-loadings aEigenvalues and percentagesof variancesinclude contributions from (Greenewalt 1962; this study) and high wing- all 26 species.Variance shared between PC-I* and PC-II* attributed to PC-I*; r (PC-I*, PC-II*) = 0.48. beat frequencies(Meinertzhagen 1955). Wing- loadingsof tourres (Uria) are moderately high, but do not approach closely the threshold of flightlessnessof 2.5 g.cm • (Meunier 1951). Us- ponents of available skeletal measurements ing available wing areas,allometric extrapola- which were significantly correlated (P < 0.05) tions of wing-loadings of flighted alcids to with body masseswere used as estimator vari- greater body massesyielded estimatesof 2.10 ables. However, unlike the rough "size" com- parisons permitted by PC-I* for the reduced skeletaldata set (Fig. 6), these regressionesti- TABLE8. Estimatedbody masses for fossilalcids, based matesalso incorporated"shape" variables that on regressionsof bodymasses of 23 Recentspecies distinguishedthe larger flightlessalcids from on principal componentsof (p) skeletal measure- flighted confamilials(Table 8). My estimatesin- ments available for each fossil taxon. • dicate that the mancalline auks were more mas- sive than the flighted alcids and less than P. R 2 nents impennis,varying between ! and 4 kg in total Species Mass• p (%) entered mass. An estimate was not attempted for the Mancalla (inter- very large, as yet undescribedspecies of Man- mediate) • 2,400 38 99.1 I, III, IV calla (Fig. 3A). Furthermore, the estimatescon- M. milleri 1,650 29 99.2 I, III, IV firmed that M. milleri was the smallest of the M. emlongi 3,800 24 98.9 I, IV, V group, followed by the "medium-sized" Man- Praemancallaspp. 3,050 23 98.8 I, III, IV calla and Praemancalla,and the largest was the Includedestimated mass for Pinguinusimpennis (5,000 g, seetext). Estimatesrounded to nearest50 g. relatively poorly representedM. emlongi(Table Pooledfor similarlysized M. californiensis,M. diegensis,and M. ced- 8). rosensts. October1988] Flightlessnessin the Alcidae 693 at 1,500 g, 2.33 at 2,000 g, and 2.53 at 2,500 g. logical modificationsobserved in flightless al- Allometric enlargementprobably would result cids and penguins. There also is osteological in impaired flight, and might compromisethe evidencethat the remigesof Mancallawere at wing-body proportionsoptimal for submarine leastas reduced as those of Pinguinus(Miller and propulsion(B•dard 1969).The mean areaof two Howard 1949). Other unusual characters of Pin- half-folded wings (the positionused for diving; guinus--sequentialmolt of the primary remiges Spring 1971) of Pinguinuswas 77 cm2. Doubled (Storer 1960), comparatively extensive fusion and divided into the estimated5-kg body mass, and short transverse processesof vertebrae this yields a "flipper-loading" of 32 g.cm 2, a (Storer 1945),and a large number of caudalver- value comparable to those of the spheniscid tebrae(Owen 1879)--may also have been con- generaMegadyptes, Pygoscelis, and someSphenis- vergent with the mancallines,but currently cus(Stonehouse 1967). This reductionin wing available material does not permit such infer- area,and other morphologicalcharacteristics of ences.Contrary to the referenceto "... degen- the flightlessalcids, are aptly termed "special- eration of the wing and keel ..." in Pinguinus izations."They are of obviousadaptive signif- by Greenway (1967), the flightlessauks had ro- icancefor one function (diving), limiting with bust wing elements and deep sternal carinae. respectto another (aerial flight), and uniquely Pinguinuswas unique among the Alcidae for associatedwith flightlessness,unquestionably its large size, exceedingthe describedmancal- a derived condition in carinate birds. lines in skeletaldimensions (Tables 2, 3; Fig. 6) Parallels have been drawn between the div- and in estimatedbody mass(Table 8). The man- ing petrels(Pelecanoididae) and flighted alcids callineswere more specializedthan Pinguinus (Verheyen 1958, Kuroda 1967, Harrison 1977), in morphometricshape characters (Figs. 3, 4, 6), and betweenthe flightlessalcids and the pen- and had wing elementsthat more closelyap- guins(Storer 1960, 1971; Pennycuick 1975; Fed- proached those of the penguins in relative uccia1980; Sparks and Soper1987) and the fossil length, flatness,curvature, and articulative ri- Plotopteridae(Olson and Hasegawa1979, Ol- gidity (Lucas 1901, Miller 1933, Wiman and son 1980).Despite these notable convergences Hessland 1942, Miller and Howard 1949). The in pectoral anatomy, obvious differences in lo- exceptionalmodification of the wing for sub- comotor adaptationsand diagnosticosteologi- marine propulsionin Mancallais indicated by cal synapomorphiesdemonstrate their homo- the degree of shaft compressionof major ele- plasious nature (e.g. Harrison 1977), the ments,well developedsulcus musculus scapu- predictionsby Olson(1980) concerning the fal- lotrioipitis, the proximal position of the hu- libility of a cladisticanalysis of such groups meral processussupracondylaris dorsalis, and notwithstanding.Particularly manifestare the by the obsoleteprocessus pisiformis, distally numerousand extreme morphologicalnovel- extended processusextensorius, and dorsoven- ties of the penguins, which include signifi- tral compressionof the trochlea carpalisof the cantly reducedmobility of the wing articula- carpometacarpus(Fig. 4; Howard 1966). There tions and radical modificationsof the remiges is also significant qualitative variation in skel- (Coues1872, Owen 1879,Sparks and Soper1987, etonswithin Mancalla(Howard 1970).The geo- Raikow et al. 1988). logicallyolder Praemancalla,as confirmedby its Alcinevs. mancallinefiightlessness.--Members morphometric intermediacy (Figs. 3, 6), wasnot of different supragenericgroups within the A1- as specializedas Mancalla osteologically(How- cidae,Pinguinus (Tribe Alcini) and the subfamily ard 1966, 1976, 1978;Howard and Barnes1987). Mancallinae share several morphologicalcor- The poorly known mancalline genus Alcodes, relatesof flightlessness.Those include large size describedby Howard (1968:19) as "progressing (Tables 1, 2, 8), relatively short wings (Figs. 1, towardsflightlessness," appears on the basisof 2), and dorsoventrallyflattened skeletal wing its ulnar proportions to have been completely elements(Figs. 3-6). Thesecharacteristics were flightless(Fig. 3B). among the first to be recognized, largely be- Ontogeneticconsiderations.--The likely impor- causeof similaritiesto the anatomyof penguins tanceof heterochrony,specifically neoteny, in (Newton 1861, Owen 1879, Lucas 1901). Raikow the evolution of avian flightlessnesshas been et al. (1988) concludedthat in flighted, wing- suggested(Lowe 1928, Olson 1973, Jamesand propelled diving birds the functional demands Olson1983) largely on the basisof morpholog- of aerial flight precludethe skeletaland myo- ical similaritiesbetween the wing and pectoral 694 BR•DLœ¾C. LZV•ZE¾ [Auk,Vol. 105 girdle of adults of flightlessspecies and juve- sharedby Pinguinus,Alca, and Uria is compar- niles of flighted relatives. However, the ob- atively large size (Figs.1, 2, 5). Largebody mass viouslocomotor specializations of Pinguinusand is an advantagefor diving birds,especially ma- the Spheniscidaeled Olson (1973: 31) to rec- rine pursuit-divers, because it reduces buoy- ommend that thesegroups "... not be included ancy and makes available a greater range of in discussionsof flightlessness."Olson (1977: water depths for foraging (Sparksand Soper 690) also stated:"The great modificationsseen 1987).A direct relationshipbetween body mass in the wing of Pinguinis[sic] are not the result and maximal diving depth was documentedin of neoteny, as seen in many other flightless alcids (Piatt and Nettleship 1985), and the div- birds .... Instead, these modifications repre- ing ability of Uria appearsto be comparableto sent highly derived specializationsfor wing- that of medium-sizedpenguins (Burger and propelled diving." Simpson1986). Implicit in this conclusionare the assump- Avian flightlessnessgenerally is associated tions that "neotenic" flightlessnessis necessarily with large, often absolute, increasesin body "degenerate,"pervasive in its impact on the size (Pennycuick 1975), and it is probable that pectoral girdle, and not associatedwith loco- the exceptionallylarge size of flightlessalcids motor specialization.Although the compres- representsan adaptive body form for subma- sion and curvatureof wing elementscannot be rine foraging (Storer 1960, B•dard 1969). Al- attributed to neoteny becauseneither charac- though Olson et al. (1979) presentedevidence terizes developing alcids, the relatively short that breedingGreat Auks at Funk Island, New- distal wing elementsof flightlessauks resemble foundland, may have fished primarily in water the intra-alar proportionsof embryonicalcids lessthan 18 m deep, it is agreedgenerally that and other nonpasserines(B6ker 1927, Marpies Pinguinustypically foraged in deeper waters 1930). Hence, they are by definition paedo- (Bradstreet and Brown 1985, Brown 1985). A morphic (Gould 1977). Definitive support for relatedadvantage of large body size is the abil- heterochronyin the extinct auks is probably ity to captureand swallow larger prey, also in- unattainable,but Livezey and Humphrey (1986) ferredfor Pinguinus(Bradstreet and Brown1985). presentedevidence of a heterochronicbasis for The relatively large contribution of culmen flightlessnessin the pectorally "nondegener- length to the size-relatedfirst canonicalvariate ate" steamer-ducks(Anatidae: Tachyeres). (Table 2, Fig. 2) underscoresthe important re- Ecologicalimplications.--The Great Auk is lationship between body size and the size of probably related most closelyto Alca and Uria the feeding apparatusin alcids (B•dard 1969). (Strauch 1985), and all three genera are consid- Although sexualdifferences in skeletal mea- ered to be comparativelyspecialized for pisciv- surementswere negligible in extant speciesof ory (Storer 1945, B•dard 1969, Hudson et al. alcid, samplesof Pinguinusfrom Funk Island 1969). Although Pinguinusis morphologically indicated bimodality in sampledistributions of specialized(Figs. 2, 3, 5), the genusand its close several measurements,especially bill length. relatives are characterized by only moderate The larger samples(n = 200) of Pinguinusmea- proportionson several major axes of skeletal sured by Lucas (1890) suggestthat sexual dif- variation in the Alcidae (Figs. 2, 5). Pinguinus ferencesin length of the femur were present, had only moderatescores on PC-II* for com- although Lucas (1890: 523) concludedother- plete skeletons(Fig. 5), an axiswith profound wise. The likelihood of sexualdimorphism of locomotory and ecological implications and bill length in Pinguinusis enhancedby the im- which reflects, in part, the patterns in pelvic portanceof bill size in the feeding niches of proportions(Storer 1945).Hudson et al. (1969) alcids(B•dard 1969),wherein sexualdifferences concludedthat the close relatives of Pinguinus in bill size may reflect intersexualniche differ- (Alca and Uria) were myologically "special- ences.Increased sexual dimorphism in flight- ized," whereas the puffins were "primitive." lessspecies characterizes at leastone other fam- The myologicaldetails of Pinguinuswill in all ily of diving birds, the grebes(Podicipedidae; probabilitynever be known;although it seems Livezey in press). likely that the genuswas at leastas specialized Another benefit of large body size is a ther- in its pectoralmusculature as its closerelatives modynamically efficient surface: volume ratio (Miller and Howard 1949). (Calder 1974, Sparksand Soper 1987). This ad- Probablythe most conspicuouscharacteristic vantage would be greater in colder waters at October1988] Flightlessnessinthe Alcidae 695

high latitudes,and probablycontributed to the by: Departmentof Biology,University of SouthFlor- extreme size of Pinguinuscompared with the ida, Tampa;Museum of Natural History, University mancallines.Furthermore, the larger body size of Connecticut,Storrs; and the Departmentof Biol- of Pinguinusmay have compensated, in part, for ogy, Universityof California,Los Angeles. Data on specimensof the GreatAuk were providedby col- its only moderateskeletal specializations,ren- leaguesfrom the following institutions:Staatliches dering it comparablein diving ability to the Museum fi•r Naturkunde, Stuttgart,B. R. D.; Zoolo- osteologicallymore extremeMancalla. gisk Museum,Copenhagen, Denmark; Mus•es de In spiteof theseadvantages of large size and Metz, Metz, France; Museum d'Histoire Naturelie, specialized wing morphology, the resultant Autun, France;Instituto di Zoologia, Universit&di flightlessnessimposed significant ecological Bologna,Italy; ZoologiskaMuseet, Lund, Sweden; constraintson the Great Auk. Inability to fly Mus•e d'Histoire Naturelie, Neuch&tel, Switzerland; undoubtedly limited the foraging radius of Museum National d'Histoire Naturelie, N&ntes, adultsduring nestingand its large size proba- France; Staatliche Museen fiir Tierkunde und Volk- erkunde, Dresden, East Germany; Naturhistoriska bly increasedincubation and developmental Rijksmuseet,Stockholm, Sweden; Zoologisches Mu- periods,thus making the speciesmore vulner- seum der Universitat, Oslo, Norway; Rijksmuseum able to climatic variations in the lengths of van NatuurlijkeHistorie, Leiden, The Netherlands; breeding seasons(Bengtson 1984). Even more Mus•e Zoologique, Strasbourg,France; Landesmu- importantwas the requirementfor nestingsites seum Joanneum, Graz, Austria. P.S. Humphrey, R. that were free from terrestrialpredators, suffi- M. Chandler, R. J. Raikow, D. S. Wood, J. Vanden ciently near rich food supplies,and accessible Berge,A. H. Bledsoe,and R. W. Storermade com- to flightlessbirds (Bengtson1984, Harris and ments on the manuscript.M. Jenkinsonand R. M. Birkhead 1985). Similar nesting habitatswere Mengel provided work spaceand accessto specimens inferred for the mancallines (Miller and How- at the University of Kansas,and K. Corbin and M. ard 1949). In addition to rendering Pinguinus Schmalz typed the manuscript. more vulnerable to human exploitation, these requirements,in combinationwith otherbreed- LITERATURE CITED ing constraintsand long-term fluctuationsin BALDWIN, $. P., H. C. OBERHOLSER,& L. G. WORLEY. climate in the North Atlantic, may have pre- 1931. Measurements of birds. Cleveland Mus. disposedthe Great Auk to a natural decline Nat. Hist. Sci. Publ. 2: 1-143. (Bengtson 1984). BAUMEL,J. J. (ED). 1979. Nomina anatomica avium. New York, Acad. Press.

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