The Condor 87:402-417 0 The Cooper Ornithological Society 1985 MYOLOGY OF THE PECTORAL APPENDAGE IN KINGBIRDS (TYZWWUS) AND THEIR ALLIES MARY C. McKITRICK ABSTRACT. -The forelimb musclesof several speciesof the kingbird group are here described and illustrated, with the goal of discovering character statesof use in delineating cladeswithin the Tyrannidae. These musclesconform in all species to the oscine pattern as described by other authors, with the exception of a few features. Special attention is given to M. latissimus dorsi caudalis, the only muscle that varies widely among, as well as within, the speciesexamined. Absence of this* musclein the speciesofMyiozetetes could mean that this group is a clade. Variation in other tyrannids, however, indicates that closely related speciesmay be losing M. latissimus dorsi caudalis independently. The present study of wing muscles in the Flycatcher (Legatus leucophaius USNM “kingbird assemblage”(Traylor 1977) was un- 5 10867), and Variegated Flycatcher (Empi- dertaken as part of a larger study, to determine donomusvarius FMNH 288494), all members whether the appendicular musculature of New of the kingbird group. One muscle, M. latis- World flycatchers (Tyrannidae) can provide simus dorsi caudalis, was intraspecifically information of use in constructing phyloge- variable, and I examined this muscle in 39 netic hypotheses for this group. Anatomical other speciesof Tyrannidae to assessthe extent data from the work of Garrod (1876), Ames of variation. Dissections were done under a (197 l), Midtgard (1982), and W. E. Lanyon stereomicroscopeat 6 x , 12 x and 25 x , with (pers. comm.) have recently been used in a the use of iodine stain (Bock and Shear 1972) cladistic analysis of relationships within the to enhancevisibility of muscle fibers. Anatom- Tyrannoidea (McKitrick 1985). Other ana- ical nomenclature is from Baumel et al. (1979) tomical data for this group are scarce and in- and abbreviations are, for the most part, from complete, and much additional information is Zusi and Bentz (1984). Descriptions of mus- needed from a variety of anatomical (and mo- cles refer to Tyrannusmelancholicus, and are lecular) systemsto clarify relationships within the same in the other speciesunless otherwise this group. stated. Comparisons with other passerine A few published studiesof the forelimb mus- speciesare noted where differences occur. cles of oscinesexist, e.g., Swinebroad (1954) Abbreviations for museums from which Hudson and Lanzillotti (1955), George and specimens were borrowed are as follows: Berger (1966), Borecky (1977), and Raikow AMNH, American Museum of Natural His- (1977, 1978), but I have found virtually no tory; CM, Carnegie Museum of Natural His- such information for suboscines.I undertook tory; FMNH, Field Museum of Natural His- to describe and illustrate the forelimb muscles tory; KU, University of Kansas; LSU, of several speciesof the kingbird group, and Louisiana State University; USNM, National compare them with what is known of these Museum of Natural History; YPM, Peabody musclesin other passerinebirds. My purpose Museum, Yale University. Collection data were was to determine polarities of character states, reported in McKitrick (1984). and thereby assessthe potential of this ana- tomical system for phylogenetic analysis.Sim- ilar data for the hindlimb musclesare provided RESULTS AND COMPARISONS in McKitrick (in press). My working hypoth- M. rhomboideussuperjcialis (Fig. l:RS) is a esis was that the Tyrannidae is monophyletic thin, flat, essentially parallel-fibered muscle, (M&it&k 1985) and, further, that the king- lying deep to M. latissimusdorsi pars cranialis bird group is also a clade (Lanyon 1984). and superficial to M. rhomboideus profundus. It arises by an aponeurosis from the neural MATERIALS AND METHODS spines of the last two cervical vertebrae and I dissected fluid-preserved specimens of the the neural spines of the first dorsal vertebrae. following species:Tropical Kingbird (Tyrun- It passescraniolaterally to insert by a narrow nus melancholicus USNM 504538 and aponeurosison the dorsomedial surface of the 504539), Rusty-margined Flycatcher (Myio- cranial two-thirds of the scapula.The cranial- zetetescayanensis USNM 504542), Piratic most fibers insert at the very cranial tip of the [4021 FORELIMB MYOLOGY OF KINGBIRDS 403 I SSM ’ SHCA FIGURE 1. Superficialdorsal musclesof the forelimb (all figuresillustrate ~jwunnusmelancholicus). Abbreviations for Figs. l-l 1: ABA, M. abductor alulae;ADA, M. adductor alulae;ADM, M. abductordigiti majoris; B, M. brachialis; BB, M. biceps brachii; CCA, M. coracobrachialiscaudalis; DMACA, M. deltoideus major caudalis; DMACR, M. deltoideus major cranialis; DMI, M. deltoideus minor; EC, M. ectepicondylo-ulnaris;EDC, M. extensor digitorum communis: ELA. M. extensor longus alulae: ELDM. M. extensor longus digiti maioris: EMR, M. extensor metacarpi radialis; EMU, M. extensor metac&pi ulna& ES, M. extensor secundario&m; FCU, M. flexor carpi ulnaris; FCU a, M. flexor carpi ulnaris, accessorybelly; FDM, M. flexor digiti minoris; FDP, M. flexor digitorum profundus;FDS, M. flexor digitorum superficialis; HUP a, humero-ulnar pulley, pars accessoria;HUP ha, humero-ulnar pulley, pars humeralis accessoria;HUP u, humero-ulnar pulley pars ulnaris; ICR, M. iliotibialis cranialis; ID, M. interosseus dorsalis;IV, M. interosseusventralis; LDCA, M. latissimusdorsi caudalis;LDCR, M. latissimusdorsi cranialis; P, M. pectoralis;PPB, M. pectoralispars propatagialisbrevis; PPL, M. pectoralispars propatagialislongus; PRP, M. pronator profundus: PRS, M. pronator superficialis;RP, M. rhomboideus profundus; RS, M. rhomboideus superficialis;SBC h, M. subcoracoideusidorsal head; SBC v, M. subcoracoideus,ventral head; SBS LA, M. subscapulariscaput laterale; SBS M. M. subscauulariscauut mediale: SC. M. sternocoracoideus:SHCA, M. scapulohumeraliscaudalis; SHCR, M. scapuldhumeraliscranialis; SP, M. serratusprofundus; SP ca, M. serratusprofundus, caudal head, SP cr, M. serratus profimdus, cranial head; SSCA, M. serratussuperficialis pars caudalis;SSCR, M. serratussuperficialis pars cranialis; SSM, M. serratussuperficialis pars metapatagialis; SU, M. supinator;SUP, M. supracoracoideus;TH, M. humerotriceps; TPB, M. tensor propatagialispars brevis; TPL, M. tensor propatagialispars longa; TS, scapulotriceps;UD, M. ulno- metacarpalisdorsalis; UV, M. ulnometacarpalisventralis. 404 MARY C. McKITRICK DMI SUP SHCR -TH SSCA FIGURE 2. Second layer of dorsal musclesof the forelimb. scapulaand are slightly separatedfrom the rest tendinous sheet on the ventromedial surface of the belly. of the distal end of the scapula. In Myiozetetesand Legatus,this muscle in- Pars metapatagialis(SSM) is a narrow, strap- serts on the cranial three-fourths of the scap- shapedbelly, arising fleshily on the lateral sur- ula. face of the true ribs ventral to the distal end M. rhomboideusprofundus (Figs. 1,2:RP) is of the scapulaand inserting under the patagial a thin, flat, triangular muscle, lying deep to M. skin near the elbow. rhomboideus superficialis. It arises by a nar- Pars cranialis (SSCR) has lateral and medial row aponeurosisfrom the neural spinesof the heads of origin. The medial head ariseson the dorsal vertebrae, caudal to the proximal origin cervical rib, from just distal to the uncinate of M. rhomboideus superficialis; it inserts processto nearly the distal end of the rib. The fleshily on the caudal two-thirds of the scapula. lateral head arisesfrom the first true rib, from In the other species that I examined, this its uncinate processall the way to the articu- muscle is as described above, except for the lation with the sternal rib. Both bellies are es- relative length of the insertion (see McKitrick sentially strap-shaped, the lateral one being 1984). wider than the medial one. They are separated M. serratussuperficialis (Figs. 1, 2:SS) con- by a slight gap on the dorsal surface of the sistsof a caudal, a metapatagial, and a cranial origin. The two bellies extend cranidorsally be- part. Pars caudalis (SSCA) is a fan-shaped bel- tween the two heads of M. subscapularis,and ly, arisingby an aponeurosisfrom the true ribs. insert together by a tendon on the ventral mar- The caudal fibers insert fleshily on the apex of gin of the cranial end of the scapula. the scapula and the cranial fibers insert by a Whereas in Tyrannusmelancholicus the lat- FORELIMB MYOLOGY OF KINGBIRDS 405 SBS M FIGURE 3. Left: muscleson the lateral surfaceof the scapulaand coracoid. Right: muscleson the medial surfaceof the scapulaand coracoid. era1belly of pars cranialis completely overlies M. scapulohumeraliscaudalis (Fig. 1:SHCA) the medial belly, in Myiozetetesand Legatus, is a bipennate, fan-shaped muscle arising on the two bellies are farther apart because the the caudal two-thirds of the scapula. The su- origin of the lateral belly is limited to the region perficial fibers arise fleshily on the dorsal sur- of the uncinate process.In Tyrannus,the two face and medial border of the scapular blade, bellies fuse at the insertion and insert by a while the deeper ones arise by an aponeurosis singletendon, but, in Myiozetetesand Legatus, on the caudolateral margin of the blade. The the two bellies remain separated.The insertion muscle narrows considerably as it passescra- is, therefore, slightly broader in Myiozetetes nially; it inserts by a broad, dense tendon on and broader still in Legatus.In Empidonomus, the dorsal surface of the bicipital crest of the the lateral belly is as in Tyrannus,extending humerus,