f y/ EVIDENCE FOR A POLYPHYLETIC ORIGIN OF THE PICIFORMES STORRS L. OLSON National Museum of Natural Histojy, Smithsonian ¡nstitiiiion, Washington, D.C. 20560 USA ABSTRACT.•Despite two recent anatomical studies to the contrary, the order Piciformes appears to be polyphyletic. The structure of the zygodactyl foot in the Galbulae is very distinct from that in the Pici, and no unique shared derived characters of the tarsometatarsus have been demonstrated for these two taxa, The supposedly three-headed origin of M. flexor hallucis longus shared by the Galbulae and Pici is doubtfully homologous between the two groups, leaving only the Type VI deep flexor tendons as defining the order Piciformes. This condition is probably a convergent similarity. Evidence is presented supporting a close relationship between the Galbulae and the suborder Coracii and between the Pici and the Passeriformes. There are fewer character conflicts with this hypothesis than with the hy- pothesis that the Piciformes are monophyletic. Problems concerning fossil taxa are also addressed. Received 24 September 1981, accepted 15 May 1982. A MONOPHYLETIC origin of the Piciformes with outside groups in a manner indicating that appears to have gained support from the si- the zygodactyl condition in cuckoos, parrots, multaneous appearance of two cladistic, ana- and Piciformes had arisen independently, tomical papers (Swierczewski and Raikow 1981, through convergence. Simpson and Cracraft 1981) that concur in the Although I certainly do not advocate a traditional concept of the order•a concept that monophyletic origin of zygodactyl birds, the has prevailed at least since the time of Gadow arguments that Simpson and Cracraft (1981) and (1893). I depart from this view in considering Swierczewski and Raikow (1981) present against each of the two major subdivisions of the Pic- such a hypothesis do not meet the require- iformes, the Galbulae (Bucconidae, Galbuli- ments of their cladistic methodology. Simpson dae) and the Pici (Capitonidae, Ramphastidae, and Cracraft (1981: 484) conclude only that "the Indicatoridae, Picidae), to be more closely re- relationships of cuckoos and parrots remain lated to another group than to each other. My among the most enigmatic within ornithology purpose here is (1) to show that the evidence . ," although "there is a general acceptance for monophyly is weak, uncorroborated, and among avian systematists . that piciforms has in part been misrepresented by Simpson are most closely related to coraciiforms or to and Cracraft (1981), and (2) to make prelimi- passeriforms and that cuckoos and parrots are nary suggestions as to the probable closest rel- not." They concede that "this hypothesis has atives of the Galbulae and the Pici. yet to be tested cladistically . ." Swier- czewski and Raikow (1981: 469) state that: "The muscular component of the foot mechanism is THE WEAKNESS OF THE EVIDENCE FOR quite different in [the Cuculidae, Psittacidae, PiciFORM MONOPHYLY and Piciformes] . tvhich supports the con- Zygodactyly.•Obligate zygodactyly, the tention (Bock and Miller 1959: 30) that those condition in which the fourth toe is perma- groups became zygodactyl independently." nently reversed and has an enlarged accessory Both sets of authors have thus tacitly accepted articulating process (the "sehnenhalter"), oc- differences between taxa as evidence of non- curs in cuckoos (Cuculidae, Cuculiformes), relationship, a procedure of which Cracraft has parrots (Psittacidae, Psittaciformes), and in the been outspokenly critical (see Olson 1982). Piciformes. This is obviously a derived con- The most complete and original work on the dition in birds that could be used to define nature of the zygodactyl foot is that of Stein- these taxa as a monophyletic group in a cla- bacher (1935), whose results have seldom been distic sense, unless it were shown that each of accurately represented (a notable exception these zygodactyl taxa shares derived characters being Sibley and Ahlquist 1972). Steinbacher 126 The Auk 100; 126-133. January 1983 January 1983] Polyphyletic Origin of the Piciformes 127 ^OK c 1 ^B<Wi (.'1 \jK|,,• • ~~/l^m^ 4E^ Or Or r 1S mi f1 Fig. 1. Posterior (top row) and lateral (bottom row) views of the distal end of the tarsometatarsus in the four groups of birds with obligate zygodactyly (illustrations from Steinbacher 1935). A, cuckoo, Centropus ateralbus (Cuculidae, Cuculiformes); B, jacamar. Gálbula mficauda (Galbulidae, Galbulae, "Piciformes"); C, toucan, Ramphastos toco (Ramphastidae, Pici, Piciformes); D, parrot. Amazona ochrocephala (Fsittacidae, Psittaciformes). Abbreviations: Sh = sehnenhalter, C II = trochlea for digit II, C III = trochlea for digit III, C IV = trochlea for digit IV, G IV = articulating surface for digit IV, Gsh = articulating surface of sehnen- halter, M 16 = depression for origin of M. extensor brevis digiti IV, R = groove for tendon of M. extensor brevis digiti IV, M 4 = depression for tendon of M. flexor perforatus digiti IV. It can be seen that the form of zygodactyly in the Galbulae is completely different from that in the Pici, and the two can in no way be regarded as homologous. The best interpretation of the evidence from the tarsometatarsus is that zygodactyly evolved independently in all four of these groups. showed that there were four distinct types of viding evidence "that osteological . char- morphology of the tarsometatarsus in birds with acteristics of zygodactyly are distinct for the obUgate zygodactyly, with that in the Galbulae piciforms and different from cuckoos and par- being as different from that in the Pici as either rots," Simpson and Cracraft (1981: 484) have of these two is from parrots or cuckoos (Fig. 1). clearly misrepresented the facts and Steinbach- In each of these four groups there is a sehnen- er's interpretation of them. halter. Steinbacher (1935: 234) even identified Nowhere do Simpson and Cracraft, nor any a sehnenhalter in owls (Strigiformes), which other authors (e.g. Bock and Miller 1959), show are facultatively zygodactyl. Thus, the state- that there are derived characters of the tarso- ment by Simpson and Cracraft (1981: 485) that metatarsus that will distinguish the Galbulae "zygodactyly and the presence of a sehnen- and Pici from parrots and cuckoos and that will halter can be interpreted as derived characters establish the Piciformes as a monophyletic defining the piciforms as monophyletic" is dis- group. In fact, the apparently less modified ingenuous. In citing Steinbacher (1935) as pro- trochlea IV and sehnenhalter in the Galbulae 128 STORKS L. OLSON [Auk, Vol. 100 are actually more similar to the condition in expanded so that fibers also originated from cuckoos, whereas the larger, more discrete, and the proxirnal end of the fibula and from the distally projecting sehnenhalter in the Pici is median raphe of the adjacent M. flexor perfor- more like that in parrots (Fig. 1). There simply atus digiti III. [Incidentally, Fig. 6d in Simpson is no evidence in the structure of the tarso- and Cracraft (1981) is mislabelled•"Fpp3" metatarsus that will demonstrate a close rela- should read "Fp3."] In Trachyphonus the fibers tionship between the Galbulae and the Pici. originating on the fibula, and those originating Swierczewski and Raikow (1981) present six on the raphe of M. flexor perforatus digiti III, myological characters to define their Clade B are slightly separated from the main belly of (= Galbulae) and six additional myological the muscle that originates in the popHteal fos- characters to define their Clade G (= Pici). Thus, sa, thus making the muscle three-headed. these two taxa differ from each other in at least Clearly, M. flexor hallucis longus, in contrib- 12 myological characters of the hind limb, as uting to the flexion of two toes in addition to well as having a completely different structure the hallux, has become strengthened by ex- of the tarsometatarsus associated with their re- panding the area of its origin to the two nearest spective forms of zygodactyly. May we not, available structures. This is directly correlated then, apply the same statement that Swier- with the Type VI arrangement of the flexor ten- czewski and Raikow used against monophyly dons and is part of the same character complex. of all zygodactyl birds to argue against mono- I could not detect any separate heads of or- phyly of the Piciformes, namely that "the mus- igin in the bucconid Hypnelus, however. In- cular component of the foot system is quite dif- deed, Swierczewski (1977: 57) states that in the ferent in those groups," a difference supporting Galbulidae and Bucconidae the heads are the contention that they "became zygodactyl "somewhat difficult to separate from each oth- independently" (Swierczewski and Raikow er." He also notes that the "common belly ex- ¡ 1981: 469)? tends only about two-thirds the length of the Origin of M. flexor hallucis longus.•Swier- tibiotarsus" in the Galbulae, versus almost the czewski and Raikow state that M. flexor hal- entire length of the tibiotarsus in the Pici. Thus, lucis longus has three heads in the Piciformes, it seems far from certain that the nature of the which they interpret as a derived condition that origin of this muscle is homologous between supports monophyly. Simpson and Cracraft the Galbulae and the Pici or even that it can (1981: 483) imply this condition to be unique really be said to have three heads in the Gal- to the Piciformes by stating that "the muscle bulae. arises by one or two heads in other birds," Type VI flexor tendons.•Gadow (1893) de- whereas Swierczewski and Raikow discuss the fined the Piciformes by their possession of the fact that M. flexor hallucis longus also has three Type VI configuration of the deep flexor ten- heads in most passerines. Because the lateral dons, whereby M. flexor hallucis longus, which head has a different relationship to the tendon ordinarily has a direct tendinous connection of M. iliofibularis in Passeriformes, Swier- only with the hallux (digit I), flexes digits II czewski and Raikow (1981: 473) consider that and IV as well, and M.