Morioka, Hiroyuki

English

Kyoto University Research Information Repository

RIGHT:URL:CITATION:AUTHOR(S):ISSUE DATE:TITLE:The Skull of Regulus regulus, withSome Remarks on the TaxonomicStatus of RegulidaeMorioka, HiroyukiMorioka, Hiroyuki. The Skull of Regulus regulus, with Some Remarks on the TaxonomicStatus of Regulidae. Memoirs of the College of Science, University of Kyoto. Series B 1960,27(1): 59-641960-07-25http://hdl.handle.net/2433/258594MEMOIRs olv TiiE CoLLEGE oF SclENcE, UNIVERS!Ty OF KYOTO, SERIES B,            Vo}. XXVII, No. 1, Article 9 (Biology), 1960The Skul} oÅí Regttlus regulus, with Some Remarks on           the Taxonoiactic Status of RegulidaeBy             Niroyuki MoRIoKAZoological Institute, College of Science, University of Kyoto             (Received June 15, l960)   Regulus which includes the Goldcrest, Firecrest aRd Kinglets is a smallgenus, with all the fouy knowfi species distributed widely in temperate Eurasiaand North America as far south as high mountains of Formosa. This genus,Åíogether with its possible relatives Leptopoecite and Lophobasileus, was oncereferred to Paridae (Regulinae) by HA.RTERT (1907, p. 394), HELLMAyR (1903,p. 2), and some earlier workers.   Recent taxonomists, however, have suggestecl that it should have the realaMnity with SylvHnae. To quote from WiT}iERBy et al. (1938, p. 314), "•••it isdiff}cult to $ee the ground for this view [association with Paridae], as they[Regulidae] do not agree with the tits in their skull form, limbs, or any otherdistinctlve structural features; their breeding-habits also differ. ++•[From Sylvi-idae] they differ in no important particular•+•" (see also RiDGwAy, 1904, p. 699).Although WETMoRE (1951) has retained Regulidae in his classificatioR, some efAmerican ornithologistsi) have placed Regulus in Sylviinae, and this arrangementhas also been fo}Iowed in the 1958 hand-list of Japanese birds. MAyR and AMADoN(1951, p. 19) placed it in the tribe Sylviini (Sylviinae), assuring of a close re-Iationship between Regulscs and PhyUescoPtts.   Apart from taxonomic argumenSs based upon general consideration, so littlehas been wriÅíten on the interRal aRatomy of regulids (SHvFF.LDT, 1889a, b).In this artic!e are presented some accouRts of the sl<ull of Regttlus reguttts,together with remarks on the taxonomic staÅíus of this group.   The writer wishes herewith to express his hearty thanks to Prof. KenjiNA.i<AMuRA aRd Dr. Mitosi ToKuDA for their kind guidance during the courseof this work.                              Descriptioll   The following description is based on four aduit skulls as weli as fragmentsfrom two other skulls:   1) MAyR and AMADoN, 1951;MAyR and GREENwAy, 1956; VAuRrE, 1959.60 ttiroyuki MoRiol<A   Skull aegithognathous. Basitemporal plate subtrapezoid, three times as wideas Iong, with front margiR a little produced at the middle and fused withparasphenoidal rostrum save a small apical portion; basipterygoid processentirely absent; parasphenoidal rostrum short. Foramen magnum cordiform; apair of well-marked grooves on the dorsai rim of occipital foramen, each groove        Fig. 1. Regulus regutu$ (LiNNE); left lateral view of the skull, $omewhat           oblique (upper), and ventral view ef the same (iewer).terminating in a small aperture; occipital condyle very small an.d spherical;lamboldal ridge rather obtuse ; cerebellar dome weil convex, forming a swelling,bounded on each side by supraoccipital fossa, which is not sharply defined;cerebral dome wide (wider than long) and gently convex, wlth the roof markedby a median groove; Iateral groove of "Sylvian fissure" very faintly indicated;interorbital region of frontal narrow, with a shallow median groove.   Tympanic cavity moderately developed, more or le$s shallow, with a sub-crescent aperture of opening; free edge running from processus articularissquamosi meetiRg at a sharp angle with the exteRsioR of the free edge of lateraloccipital wing and not merging into the latter, whiclt curves forwards as a well                          The Skull of RegUIUS regUlteS 61defined rldge and joiRs postorbital proces3•; postorbital proceo.s very e.hort;temporal fossa wholly obliterated; processus zygomaticus squamosi prominent;processus articularis squamosi rather indistinct; antorbital plate naryow, withlateral border rather `truncated' than `winged'; ectethmoid foramen eeingie;Iachrymal fused, not free ; interorbital septum largely fenestrated, remaining onlya very sleRder bar in the middle.    Premaxilla slender co.nd of mederate leRgth, slightly decurved in front;dentary process of premaxilla fairly broacl, feebly bending outwards; nasalprocess narrow. Nasal holorhinai, with an oblong-ovtal aperture of narico.l orifice ;descen({ing proce.es of nasal very narrow; nasal hinge iRdistinct; ossified nasalseptum composed of a thin sheet of fragile rudimentary bone, which protrudesvertically from the nasal process at about oRe-third from the posterior end.Mandible flexible and slightly bowed downwards, with narrow .eymphysial regionand narrow lateral vacuity.    Maxilla clecidedly small and ill-defined, and not perforated by small pneu-matic foramina; mcrtxillo-palatine process fairly long and slender, extendingobliqtiely backwards on the veBtral side of the free end of vomer for nearlya half the length; pedice} very slender; pedate free end forming a thin fiatplcate of oblong bone, with the apex slightly hooked outwards. Anterior palatalBFig. 2. Regitltis regulus (LiNNE).--A. Left maxillo-palatine, ventral view.      B. Vomer, ventral viexv.--C. Left palatine, ventral view.62 Miroyul<i MoRIoKAvacuity widely open in front of maxillo-palatines. Jugal and quadrato-jttgaislender ancl nearly straight. Vomer broacl, rather short and robust, diiatedanteriorly, more or less trough-skaped iR diorsal aspect, ancl with a weli degnedmedian ventral keel; front margiR deeply notched oR either side of mediaRline in front, with lateral angles well produced into a pair of delicate quadran-gular processes, each twisted Iateraliy towarCls the apex which is dilate(l lntoa cup ; posterior part deeply cleft oR the mediait line for more than a half tkelength. IRterpalatine process long and conspicttous, with tke apex poiRted andslightly turned up ; external lamina narrow, with the postero-external angle eitherobtuse or subtyuncatecl at apex; prepalatine bar long, slender and closely ad-jacent to dentary process of premaxilla for `"tbout aRterior two-fifths of its fulileRgtk. Pterygoid nearly straight, compressed and relatively short, wlth theanterior end hooked but not dilated into laminar plate; quadrate relativelysrnall, with moderately developed articular precesses.    The fo}lowing measurements were taken from skull$. Average measure-ments and raRges are iR millirnetres. (For method employed, see FisHER, 1944,p. 272.)    Skull length, 23.3 (22.4-23.5) ; skull width (greatest width of cranium), 12.0(11.7-12.0) ; basal length (from ventral lip of foramen magRum to tip of bill),20.2 (19.4-20.4); cranial length, 13.3 (12.9-13.5); cranial height (from plane ofbasitemporal plate), 8.5 (8.3-8.7) ; postorbital width, 101 (9.TIO.2) ; interorbitalwidth (fiarrowest width of interorbital region of frontal), 1.5 (1.5-1.7) ; premaxll-lary length, 9.7 (9.4-9.9) ; premaxlllary anterior to nares, 4.6 (4.4-4.7) ; bill depth,1.1 (1.0-1.2); bil} width, 1.9 (1.8-1.9); narial iength, 43 (4.1-4.4); mandibularlengtlt, 16.6 (16.0-16.8) ; symphysial Iength, 3.7 (3.7-3.8).                           Taxonemic Remarks    The skull of ReguZus may be distinguished fyom those of the other sylviinegeRera by the follow2ng points: ossified nasal septum present ; maxillo-paiatine                                                                          'process long and slender, with pedate free end thin, oblong and neither infiatednor pneumatic; vomer broad and short, with a trifurcate front margin andwidely spaced posterior limbs; interpalatine process prominent; external laminaof palatine narrow, wlth the postero-external angle more or le.es obtuse; anindistinct nasal l}inge preseRt; (lescending process of nasal slen(ier; externalaperture of tympanic cavity narrow, with small postorbital proce$$ and devel-oped w2ng of exoccipital. Besides these there are other minor differences toosubtle to be constant. The characteristlcs glven above will, however, besuthcient to separate Regwi tts Åírom the remainlng genera of $ylviinae, thoughthe diagnosis is based only oR R. regulus.    In all the six sylviine genera examined by the writer2), the ossthed nasal   2) The following species were available for comparison : PhylloscoPus borealisl P. ecciPit-alis, P. ijimae, Cettia d-iPhone, UrosPhena squameicePs (damaged skull), Locttstella ocltotensis,L. lanceolata, Aerecet}haLus arttndinaceus, A. bistrigicePs and Cisti.cota Mtnciais.                          The Skull of Regulus regulteS 63septum is xxot represented even by a vestige. Maxillo-palatine processes aremore or lee.s pxxeumatic or spongy iR character, especially so in Cett'ia andAcrocePh.altts. In this subfamily, as here represented, these boRes Åíend to berather variable iR their configuration. They are short and very muclt dilateddista!ly, having the free distal eRd usually infiated to enclose air-cell. Only inLocscstella the free end of maxillo-palatiRe is fiat aRd lacks air-pocl<et. It maywell be noted that the vomer of the sylviids has been reduced to a very smallbone. Here, the bone is represeRted by a thin oblong plate, which is narrow,mttch shorter in length and with decldedly shorter llmabs. It is as a rule del-icately dentate (subject to a certain variation) along the front margin butwithout any "horns" suclt as met with in Regultcs.    Regttlus may be different from the sylviids in the shape of palatiRe. In thelatter group, external lamina of palatine is spacious, with promineRt postero-extemal angles, whereas the interpalatine pyecess i$ small. The nasai hinge isperfectly effaced. Some difference may a!so be found in tke relative size of thedescending process of nasal, which is much wider in the sylviids. Althoughthere remains some doubt about the taxonomic value of this bone, the characterwas once claimed by LucAs (1889, p. 173) to be very much usefu! in thrushes,Miminae and wrens. Sylviinae may agree with Regulscs in the form of theoccipital, squamosal and ethmoidal regioRs of the skull and the tympanic cavity,but in one point the former is dfierent .qignificantly from the latter. In theformer group tke postoybital process is prominent (rather short !n Locttstella>.    Despite great similarity in external structure, the subfamily Sylviinae is nodoubt a most heterogeneous group in the large assembiage of thrushes-fiycatchers.The six genera of the sylviids examified are variabie to some exteRt in thecharacters of the skull. They somewhat vary iR the configuration of maxillo-palatine.a and vomer, a character which is very stab}e in some other groups,e.g. Turdinae. Hence the warblers may be consideredpossibly to be sttbdividedinto two or more. There is, however, scarcely any doubt about the arrangementto place Regulecs in a group, either as a subfamily or as a family, quite distinctfrom ail the other warblers. This rnay be known from the view that some ofthe discriminative characters are not of species or genus but of higher categeries.    The validity of the arrangement may further be supplemented by charactersotker than those shown by the skull. Of the four main characters enumeratedby RipLEy (1952, p. 3) in discriminating subfamilies within Muscicapidae, twofeaÅíures (moult and tarsus) are available to distinguislt Regutus from Sylviinaeand one (juvenile p}urr)age) may be commoR between the two. Double moult,a partial or complete spring moult in addition to the complete autumn moult,is far prevalent in Sylviinae, whereas only a single annual moult takes placein Regultts. Tar$us is primarily scute}late, either distinct}y or indi$tinctly, inSylviinae, but booted in Regulus (quasi-booted iR LePtoPoecile). It has beennoted, however, that there is a tendency towards booted tarsi in the formergroup. The fourth character of RipLEy, the rictal bristles, is most arnbiguous,64 Hiroyuki MoRIoi<Aand may not have so a definite value. These bristles are present in both thegroups as well as the other re}ated ones. Regttlus also possesses a single minutestiff feather covering each nosÅíril (except R. calend"la). In addition to these,the differeRces in plumage and behaviour between the two sexes and betweenadult and young are more pronouRced in Regulus than in Sylvlinae.    It should be noted that even these `generaHzed' characters, now of frequentuse, are more or less conffuent and not so perfectiy diagno$tic of the `groups'.There usually occur sorne transitioltal forms among them. Such `generalized'characters are, however, stiil useful in recognizing natural groups, and theoccurrence of exceptional forms may better be regarded as the results of rapiddiversification. In some cases, the presence of such intermediates may indicatethe afinity between certain two gro"ps, but in other cases, it may be a mereresult of superficial coBvergence. It seems to the writer that Reguitts hasltitherto been related to Sylviinae on the basls of certain unreliable characters.So far as iRdicated by the features discussed oR the Åíoregoing pages, Regutttsmay be related to Sylviinae but distantly, and tke relationship between themmay not be so close as has generally been understood up to the present. Inshort, Regulidae may better be retaiBed as afl independeRt subfamily under thepresent circumstances of avian classification.                                ReferencesFIs}iER, }I. I., 1944. The skulls of the cathartid vultures. Condor, 46: 272-296.HARTER'r, E., 1907. I])ie V6gel der palljarktischen Fauna.---I. Berlin, R. Friedltinder & Sohn.ffEuMAyR, C. E., 1903. Paridae, Sittidae und Certhiidae. In Sc}iuLzE, Tierreich, 18. Berlin,       R. Friedlander & Sohn.LucAs, E A., 1889. Notes on the osteology of the thrushes, Miminae, and wrens. Proc. U. S.      nat. Mus., 11 (fer 1888): 173-180.MAyR, E., & D. AMADoN, 1951. A classification of recent birds. Amer. Mus. Nov., 1496: 1-42.------- & J. C. GREENwAy, JR., 1956. Sequence oÅí passerine families (Aves). Breviora, 58:      1-11.RIDGwAy, R., 1904. The birds of North and Middle America. Bull. U. S. nat. Mus., 50 (3):      i-xx -l- 1-801.RipLEy, S. D., 1952. The thrushes. Postilla, 13: 1-48.SHuFELDT, R. W., 1889a. Contributions to the comparative osteology of the families of North      American Passeres. J. Morph., 3; 81-114.....,S8g?,bl,,O,? `\g."&i.tk'gn.;f,,C3a,"gfgS,ge,,`h,%SXEI.eMA gXfg.vaÅígi,,..,.. o,,.,p,,.      seriformes. London, H. F. & G. Witherby.WETMoRE, A., 1951. A revised classification for the birds of the world. Smithson. misc.      Coll., 117 (4): 1-22.Wm{ERBy, H. F., F. C. R. JouRDAIN, N. F. [irlcE}iuRsT & B. W. Tuci<F.R, 1938. The Hand-      book of British Birds.-II. London, H. F. & G. Witherby.

The Skull of Regulus regulus, with Some Remarks on the Taxonomic Status of Regulidae

https://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/258594/1/mcsuk-b_27_1_59.pdf

The Skull of Regulus regulus, with Some Remarks on the Taxonomic Status of Regulidae

Abstract

Similar works

Full text

Available Versions

Kyoto University Research Information Repository