285(1) A CONTRIBUTIONTO THE MORPHOLOGYAND PHYLOGENYOF THE FALCONIFORMES l'tralcoln Jol1ie, Biologica.l Sciences, -Northern Illinois LLriv., DeKalb, Il1. 60115 Received September 9r I9T5; December l0-, I9T6' ABSTMCT: Morphological studies of the falconiforms have suggested that.!h"- group is polyphyletic. The basic goal of the study-is to detail the anatomical variation observed in the 300-odd species, with major enphasis on the skeletal systen, and to search-for the neaning of similarities as well as differences. Similarities are evaluated in terms of being parallelisms, convergences or evidence of close relationship. The question is continually asked,are differences significant in terns of demonstrating lack of relationships or do they nerely represent gaps in continua. Ttre traditional pattern of tabulated points of sinilarity or difference--most of which are arbitrary (and ignore instances of approach or overlap)-- is avoided on the grounds that the real value of such information is in understanding how it is arrived at. The diversity of views relative to anatomical features is explored in an effort to clarify nethodologyl however, methodology, as such, is not discussed separately, it is revealed by the treatnent of the naterials. The account does not dictate conclusions--although the writerfs interpretations are included--but does try to expose the known sides of each question. The conclusion reached is that the four groups of falconiforns should not be associated in a single order. The Cathartidae and the Falconidae are recogni zabLy related to other orders of birds while the Accipitridae and Sagittariidae cannot be associated more closely with each other than to other orders. INTRODUCTION The Problen The order Falconiformes, as currently defined (Mayr and Amadon, 1951-; Wetmore, 1960; Brown and Amadon, 1968) is made up of five families of living birds, plus two of fossils. The interrelationships of some of these have been suspect and some authors have gone so far as to state that the suborder Cathartae and the family Sagittariidae of the suborder Falcones should be separated as distinct orders. The apparent heterogeneity of this array seems particularly worthy of investigation and analysis. The approaches developed might prove useful in the evaluation of other fanilies and orders of birds. It is not to be concluded from the assumed heterogeneity that the objective of this study is to dismember the order and to scatter its parts in some novel way. Recourse to the lengthy lists of associations for each family and aberrant genus conpiled by Ftirbringer (1888, vol.2) should convince one that this is hardly possible. It is true that the study was undertaken with certain preconceived notions as to the reLationships of the various parts of this order, but each of these ideas and its alternative(s) has been weighed again and again. The method of "phylogenetic studyfr has been discussed at length by Hennig (1966) , but I cannot foll-ow his recomnendations. I have sought to identify those "apomorphous" features which would identify Evol-. Theory I2285-z9B (Decen'ber19T6) I continued in vo]. 2 The editors thank two referees for help in evaluating this paper. 286(2) M. JOLL]E the various taxa but with no more success than other systenatists. I have looked for transformation series, again without success (the usual reticular relationships were seen). I started with the theory that this order is polyphyletic and have attenpted to indicate succinctly as possible, by summaries or tables wheie appropriate, -as how this conclusion has been reached both by ne and by othbrs-. It nay be that Hennig's system will prove applicable in the long run but it will require at least another step beyond that which I hive taken; again, it may remain only a theoretical possibility. I have looked in vain for model situations in Hennig that I could follow with the naterials at my disposal. (r have-been comforte4 by Hennig's inability to define the class Mammalia, pp. 2L5- 2t6, a situation not unlike the definition of the falconiform gioups.) rn lieu of such a "definitive" rnethod of analysis, r have been- satisfied to "advance'f our conception of the "order" by way of the comparative (I -approach far beyond hope) that of Sushkin or Pycraft-- whose works have served as rnodels. This is a descriptive study in which comparisons, tested and evaluated, are used to determine relationships, based on the belief, and contrary to Hennig, that this sti1l is the only practical way. The examples of paraphyletic (and polyphyletic) associations that sometimes result from such an approach are well known to evolutionary systernatists as are the failures of "overal1 sirnilarities" to reveal real relationships. Like others, although striving to identify monophyletic groups and abhoring paraphyletic or polyphyletic groups, I prefer a "typologicalr' or syncretic system in which birds are identified as a class with an order, or orders, for the falconiforms. I have not dwelt here on methodology, as I feel that it is best revealed by the treatment of examples. The goal of this study is to deterrnine in detail the anatomical variation in each of the groups of falconiforms that have been recognized and to assess the differences and similarities in terns of phylogenetic relationship, or lack of it. This does not involve the compilation of tables of unanalysed anatomical details to be treated in some numerical fashion (Gadow, Filrbringer, and others). The study is, as far as possibler 3r original descriptive anatomy based on comparisons of hornologous features and the evolutior.ary trends of such features; it involves recognition of nonhomologous, parallel or convergent features and theii evaluation,so that they can participate in the establishrnent or disestablishrnent of groups. A consideration of the anatomical facts, as described here, will lead directly to the conclusions--at least in terms of the hypotheses presented. These hypotheses relate to the identification of phylogenetically important features and the directions of change in each feature. Such hypotheses are more meaningful if the fossil record is extensive. In birds, such is not the case. Without fossils, the selection of phylogenetically important features nay be based on the palimpsest theory of Gregory (1947), which assumes that one can separate those anatomical details which have been modified in adaptation (habitus) from the underlying structural pattern (heritage) indicative of the ancestry of the species. The problen is not quite this sinple, since Richardson (L942:234-236) pointed out that the new adaptive features are FALCONIFORMES 287(3) superinposed on old. Thus, the heritage itself consists of successive layers of adaptive features. It has been suggested that the discovery of useful anatomical features with which to characterize the diurnal predators is made difficult by the profound rnodifications needed for their raptorial existence. Such extrerne adaptations, if shared as a common habitus, could prove either cornmonancestry or convergence. Since such a common habitus is not apparent, 3r alternate view would be that only linited nodification was required to produce the several types of predators from distinct ancestral types (not sharing a common heritage) . Studies of paralle1 or convergent adaptations in other birds (Richardson, L94Z; Stolpe, L935) show that superficial agreement in way of life and method of locomotion (Hespenornis, 1oon, grebe; auk or heron, crane, stork, flamingo) nay alter greatly the general proportions, but many minor details of structure reveal the heritage. If the falconiform groups are interrelated, then the problen is one of discovering underlying sinilaritiesr or combinations of basic features shared by the different families of this order. It is doubtful if the hooked bill and carnivorous habit originally used in the association of these families constitutes the heritage. If the falconiform groups are not interrelated, then comparisons with other kinds of birds nay lead to identification of the heritage. The deternination of phylogenetically important features is not made easier by reports in the literature. First the Anerican student is handicapped by the inaccessibility of rnajor works written in foreign languages and of such mass as to defy adequate translation without mastery of these languages. Second, the foundation works belong to the last century and there has been continued developnent of the subject, or at least in the interpretation of its facts. Third, in the opinion of the writer, the jargon of anatomy makes understanding and comparisons difficult and at tines impossible. Last, there has been far too much deference to authority (although authorities are frequently right) and far too 1itt1e effort directed toward broad systenatic investigations. From the anatomical reviews in the literature, most features seem to fall into one of three categories: relatively uniform from species to species, variable without apparent phylogenetic or functional correlation, or adaptive. Any of these is of questionable value for establishing relationships, with the result that, having chosen from the available criteria, we seen to be torn between separating groups on the basis of certain characteristics and uniting then on others. Utilizing what appears to be the same "factsr" two morphologists nay come up with conflicting conclusions. The difficulties of identifying and using phylogenetically irnportant features will become increasingly evident in the following chapters. The greatest difficulty will be to overcome some of the prevalent views concerning avian anatomy and its taxonomic utif:-zation. Unfortunately, the "facts" do not reveal a "black and white" situation, nor do they fix even the shades of gray. This indeterrninacy of result is in itself important since it helps to destroy the belief which exists, in spite of rnuch evidence to the contrary, that sirnple "key characters'r can be defined and utilized' 288(h ) M. JOLLTE at least in the case of the Falconiformes. Final1y, assuming that the anatomical facts can be narshaled to support a phylogetrL changes in existing classification may' be necessary.