sign in sign up
<<
Home , Anatalavis, Enaliornis, Neogaeornis, Rallus

762 ShortCommunications andCommentaries [Auk,Vol. 112

The Auk 112(3):762-767, 1995

Avian Premaxilla and Tarsometatarsusfrom the Uppermost of Montana

ANDRZEJ ELZANOWSKIa AND MICHAEL K. BRETT-$URMAN2 •Departmentof VertebrateZoology, National Museum of NaturalHistory, SmithsonianInstitution, Washington, D.C. 20560, USA; and 2Departmentof Geology,George Washington University, Washington, D.C. 20052,USA

Despitea variety of fragmentary,apparently neog- is rounded and smooth,and the sidesare very steep. nathousavian fossilsknown from the uppermostCre- The largest among the neurovascularforamina scat- taceousdeposits (Brodkorb 1963, Olson 1985, Olson tered on each side are two elongatedorsal foramina: and Parris 1987),we still lack even an approximate the vessel from the rostral one coursed rostrad, whereas idea of how many neognathouslineages survived be- the vesselfrom the caudalone apparentlybifurcated yond the Cretaceous/Tertiaryboundary. Most of the into a smaller rostral and a larger caudal branch. In avian bones reveal a charadriiform or addition, a number of smaller openingsperforates transitional charadriiform-gruiform morphology, eachside of the symphysis. which may be plesiomorphicfor most (Olson 1985) The ventral surfaceof the premaxillarysymphysis but probably not all of the neognaths(Elzanowski is strongly concave(Fig. lc, d). There are no distinct 1995). Other than that, there is some evidence neurovascularforamina on the ventral (palatal) sur- for the existence of in the Cretaceous(Olson face,with the possibleexception of one small opening 1992)and mostly indirect evidencefor the pre-Ter- on the left side. The palatal shelvesof the premaxilla tiary origins of the relict pelecaniforms(Phaethon- begin from the symphysialtip and graduallybroaden tidae and Fregatidae) and procellariiforms (Elza- caudally where each of them occupiesone-third of nowski and Gaiton 1991). The last of these are pos- thesymphysial width. They are flat and slightly sloped sibly representedin the basalportion of the Early dotsad.The tomial edgesare blunt. Betweenthe pal- PaleoceneHomerstown Formation in New Jersey atal shelvesis a deep, 1.1-mm-wide median groove (Olson and Parris 1987). whosebottom merges with the roof of the symphysis. In this paper, we describetwo fragmentaryLate The groove is imperceptibly expanded in the mid- Cretaceousavian :a premaxilla that fits in the length of the symphysis.A pair of neurovascularca- charadriiform-gruiformassemblage and maypossibly nals is enclosedby the shelvesventrally. representone of the alreadyestablished genera; and The preservedfragment of the dorsalbar is com- a distalfragment of the right tarsometatarsusthat may posedexclusively of the frontal processof the pre- represent the earliest record of the anseriform lin- maxilla. It cannot be determined whether the pre- eage. maxillary processof the nasal had extendedto the Both specimenscome from the locality known as symphysisand then fell off (which would be likely Bug Creek West, Montana, Hell Creek Formation, in a juvenilebird) or terminatedmore caudally. The which is of (Maastrichtian) age; the frontal processis 3.4 mm wide and 1.8 mm thick, specimensare part of the collectionsof the Museum including a strong median ridge on the ventral sur- of Paleontologyof the University of California at facebehind the symphysis(Fig. ld, e). Berkeley(UCMP). The premaxillaUCMP 117598was In the primitive condition retained by most , collected in 1974 by J. D. Archibald and the tarso- the premaxillarysymphysis is openventrally (i.e. ex- metatarsusUCMP 117599in 1975 by D. Lawler. cavatedup to its roof) at least along the midline. In Premaxilla.--We have made detailed comparisons the opposite,derived condition, the palatal shelves of this specimenwith the charadriiforms,gruiforms, are fusedin the midline, enclosinga medianchamber. podicipediforms,and Gavia(i.e. with thoseextant taxa (Elzanowski 1991:figs. I and 3) and most having a premaxilla that showsan overall similarity of the neognathousbirds with an open premaxillary to the fossilirrespective of size).The surveycovered symphysishave the palatal surfaceof the symphysis all generaof thesegroups represented in the avian perforatedby a pair of majorneurovascular foramina osteologicalcollection (Wood and Schnell 1986) of at the rostralend, a conditionpossibly plesiomorphic the National Museum of Natural History (USNM). for the Neornithes (Elzanowski 1995). The lack of The fragmentincludes the premaxillarysymphysis these foramina seems, therefore, to be a derived con- and the rostral fragment of the dorsal bar (Fig. 1). dition that evolved in the Scolopacidae,Rallidae, He- The symphysisis 17 mm long, slightly decurvedand liornithidae, Spheniscidae,and Gayla. approximatelyas high (4.3 mm) as it is wide at its In Hesperornis(Elzanowski 1991:figs.1 and 3) and midpoint;it is slightly broadercaudally (4.8 ram).The the neognathswith an openpremaxillary symphysis, rostralend is somewhatsquared, which may or may theventral (palatal) concavity of the symphysisshows not be due to postmortemdamage. The dorsalsurface a tripartite subdivisioninto two lateral elevationsen- July1995] ShortCommunications andCommentaries 763

c d

Fig. 1. PremaxillaUCMP 117598in (a) left lateral, Or)dorsal, (c) ventral, (d) ventrocaudaloblique, and (e) right ventro-obliqueviews showing neurovascularcanals. White arrows in panel a point to frontal process and in panelb to ventralgroove in premaxillarysymphysis and palatalshelf of premaxilla.Scale bar equals 10 min. 764 ShortCommunications and Commentaries [Auk, Vol. 112

closingthe neurovascularcanals and a mediantrough. view. Trochlea II has a tongue-shapedwing and no In most of these neognaths,the two lateral elevations distinct ligamental pit. Trochlea III has the lateral take the form of well-defined palatal shelvesand the margin slightly sigmoid and the ventral part of the median trough is representedby a well-definedme- articular surfacepointed and strongly asymmetrical dian groove.In the majorityof cases,the shelvestaper at the end, which is embayedmedially. Trochlea IV rostrally, whereby the tripartite shelf-and-groove hasthe lateral lip descendinggradually onto the shaft configurationdoes not extendto the symphysialtip. and bears a distinct ligamental pit. The attachment In contrast,the grooveextends to the symphysialtip scarof the sesamoidligament is distinctand slightly in the BugCreek fossil. Among extant birds, the groove elevated distally. The distal foramen is large, elon- extendsto the symphysialtip in one of the two gate, and separatedby a very narrow bridge (which of the Rostratulidae(the American Painted Snipe; itself is much shorter than the foramen) from the Nycticryphessemicollaris), and the majority of Scolo- lateral intertrochlear incisure. pacidae,the exceptionsbeing the Broad-billedSand- The overall configurationof the trochleae agrees piper (Limicolafalcinellus), the Jack Snipe (Lymno- with: ,including Presbyornis(Wetmore cryptesminimus), the Red Phalarope(Phalaropus fuli- 1926:figs.10-12, Olson and Parris 1987:fig.7); small carius),and the turnstones(Arenaria). In the Red-necked , especially Odontophorinae; Gruidae, Phalarope(P. lobatus)the rounded tomial margins Aramus,and Rallidae, which are probably closelyre- could be regardedas vestigialshelves. lated within the gruiforms; and most of the Char- What makesthe fossilpremaxilla dramatically dif- adriiformes except for the Burhinidae, Jacanidae, ferent from all rhynchokinetic charadriiformsis the Haematopodidae,Rhynchopidae, and Telmatornis(Ol- presenceof a prominent ventral ridge or bulge on son and Parris 1987:fig.7). the ventral side of the frontal processnext to the A prominent character that is shared exclusively premaxillary symphysis(Fig. ld, e). Such a structure with the anseriforms is the extremely distal position makes the dorsal bar rigid at the rostral end. The of the distal foramen in ventral view, with only a significanceof this morphologyfor cranial kinesisis narrow bridge separatingit from the lateral intertro- well illustratedby its diversityamong the Rallidae. chlear fissure(Fig. 2e). This characterhas not been In those rails (e.g. ,Capellirallus) that are am- found in any other terrestrialor aquaticnonpasser- phikinetic (Zusi 1984:tableI) and, thus, have a distal ines. Although the distal foramenis relatively large bendingzone (seeOlson 1975:fig.3), the ventral sur- in the grebesand loons, it is separatedfrom the in- faceof the dorsalbar is flat, concave,or at mostslight- tertrochlearspace by a broadbony bridge.In addition, ly convex.By contrast,all prokinetic rails--including the fossil agreesspecifically with the anatids in the Atlantisia,Diaphorapteryx, Fulica, Gallinula, (see compactpositioning of the trochleae, which is prob- Olson 1977), Tribonyx(see Olson 1975:fig.1), Himan- ably a swimming adaptation,and with Presbyornisin tornis,Porphyrula, Porphyriops, Poliolimnas, and Pardir- the extraordinarysize of the distal foramen,which is allus--have the ventral surface of the dorsal bar mark- even larger than in the anatids.Since the anatidshave edly convexand/or with a distinctmedian ridge. This legsadapted for swimmingand Presbyorniswas a wad- evidencesuggests that the BugCreek had a pro- er, the large size and extreme distal position of the kinetic rather than rhynchokinetic or amphikinetic distal foramendo not seemto be correlatedwith any skull. particularlocomotory function. The consistentsimi- A combinationof a shelf-and-groovestructure of laritiesto Presbyornisand the anatidssuggest that the the symphysialtip (known only in the probing char- new tarsometatarsusrepresents a closerelative of the adriiforms)with a thick, ridged,and rigid rostralend anseriforms. of the dorsalbar (not found in the probing charad- However, the fossil differs from either the anatids riiforms) is unique to the Bug Creek fossiland pre- or Presbyornisin having trochlea III distinctly em- cludesits assignmentto any extantfamily of birds. bayed medially at its ventral end, a condition found Tarsometatarsus.--Thisfossil was comparedin detail elsewhereonly in the sheathbills(Chionis; Fig. 2f, g), with tarsometatarsiof charadriiforms,gruiforms, an- and in the tongue-shapedwing of its trochleaII, such seriforrns,galliforms, and fossil genera of the char- as seenin cranes(Gruidae) and limpkins (Aramus).In adriiform-gruiformassemblage (Brodkorb 1963, Ol- Presbyornisthis wing is more or lesstruncated at the son 1985, Olson and Parris 1987). Body-massvalues end, whereasin anatidsit takes the form of a flange are from Dunning (1993). descendingonto the shaft. In addition, the fossildif- As far as preserved, the distal end of the tarso- fersspecifically from the anatidsin lackinga distinct metatarsusis intact exceptfor a break between troch- furrow in trochleaII, and from Presbyornisin lacking lea II and trochleaIII. The arrangementof the troch- a distinct ligamental pit on the trochlea II and in leae is compact,with narrow intertrochlear spaces having the lips of trochleaIII barely set off from the (Fig. 2). TrochleaIII protrudesfar beyondthe troch- shaft in side view. leaeII and IV, trochleaIV protrudesfar beyondtroch- Presbyornisis known since the (Olson lea II, trochleaII is in a ventral position,and the entire 1994) and unquestionableanatids only since the Oli- roedial surfaceof trochlea III exposedin the roedial gocene(Olson 1985). Another possibleearly record July1995] ShortCommunications andCommentaries 765

a b c

.t

d e

f

g Fig. 2. Distal ends of right tarsometatarsi.UCMP 117599in (a) lateral, (b) medial, (c) distal (d) dorsal,and (e) ventral view. Panel f is dorsal view and panel g is ventral view of Chionisalba (maximum width 9.8 mm) on left, Anasplatyrhynchos (maximum width 8.8 mm) in middle, and Fulicaatra (maximumwidth 9.7 mm) on right. Note differencesin positionof distal foramenand strongasymmetry of ventral end of trochleaIII in UCMP 117599and Ch/on/s.Scale bars equal 10 mm (upper scalefor panels a-e and lower for panels f and g). 766 ShortCommunications and Commentaries [Auk, Vol. 112

TABLE1. Measurements (in millimeters) of the tar- sometatarsus is close in size to the tarsometatarsus sometatarsus UCMP 117599. UCMP 117599(Table 2). It is therefore possiblethat the birds that yielded the premaxilla UCMP 117598 Character Measurement and tarsometatarsusUCMP 117599were of equal size, Maximum distal width 10.2 which in turn opensup a possibilityof their being conspecific.However, the length of the premaxillary Trochlea II symphysismay be only looselycorrelated with body Maximum depth 6.5 size even within a singlefamily, suchas the Rallidae Maximum width 3.2 (pers. obs.). Trochlea III Acknowledgments.--Thedescribed material was col- Medial depth 5.5 lected during the 1974 and 1975 expeditionsof the Lateral depth 5.7 University of California at Berkeley,which were part- Dorsal width 3.4 ly funded by a grant from the National ScienceFoun- Distal width 4.1 dation to William A. Clemens. We thank Storrs L. Ventral width 3.2 Olson, Richard L. Zusi (both of the Smithsonian In- Trochlea IV stitution),and Larry D. Martin (University of Kansas) Medial (internal) depth 6.8 for reviewing the manuscript,and Howard Hutchi- Lateral (external) depth 5.2 son (UCMP) for loan of the specimento M.K.B.-S. Ligamental pit 1.6 x 2.0

LITERATURE CITED of the anseriformlineage is a humeruswith a ducklike BRODKORB,P. 1963. Birdsfrom the Upper Cretaceous appearancethat wasdescribed as rex (Olson of Wyoming. Pages55-70 in ProceedingsXIII In- and Parris 1987) from the , ternationalOrnithological Congress (C. G. Sib- which now provesto be of Paleoceneage (Olson 1994). ley, Ed.). Ithaca, New York, 1962. American Or- Thus, the tarsometatarsusUCMP 117599 may repre- nithologists'Union, Washington,D.C. sent the oldest known bird with anseriform affinities. DUNNING, J. B., JR. 1993. CRC handbook of avian Sizecomparisons.--The distal width of the fossiltar- body masses.CRC Press,Boca Raton, Florida. sometatarsus(Table 1) is close to that of the Red- EI•ZANOWSKI,A. 1991. New observations on the skull knobbedCoot (Fulicacristata; 10.7 mm, body mass826 of Hesperorniswith reconstructionsof the bony g) and falls within the rangeof this measurementin palateand otic region. Postilia207:1-20. the Double-stripedThick-knee (Burhinus bistriatus; body EI•ZANOWSKI,A. 1995. Cretaceous birds and avian mass787 g), being slightly below the figure for the phylogeny.Cour. Forschungsinst. Senckenb. 181: largestsubspecies B. b. vocifer(Table 2). The fossil 37-53. tarsometatarsuscomes from a bird of approximately ELZANOWSKI,A., AND 1:'.M. GALTON. 1991. Braincase the samesize as two early Paleocenefossils from New of the Early Cretaceousbird Enaliornis.J. Vertebr. Jersey(Olson and Parris 1987):a humerus described Paleontol. 11:90-107. as Anatalavis rex; and a tibiotarsus described as Palaeo- OL3ON, S. L. 1975. A review of the extinct rails of tringalittoralis (Table 2). All three fossils,therefore, the New Zealand region (Aves: Rallidae). Natl. mayrepresent the samegenus if not the samespecies. Mus. New Zealand Records 1:63-79. In addition to size, the fossil tarsometatarsus UCMP OLSON,S. L. 1977. A synopsisof the fossil Rallidae. 117599and A. rexagree in showinganatid similarities. Pages339-373 in Railsof the world (S. D. Ripley). The premaxillary symphysisin UCMP 117598is D. S. Godine, Boston. almost of the same length (17 mm) as that of the OLSON,S. L. 1985. The fossil record of birds. Pages Double-stripedThick-knee (B. b. vocifer),whose tar- 79-238 in Avian biology, vol. 8 (D. S. Farner, J.

TABLE2. Size comparisonof Bug Creek bird (as representedby tarsometatarsusUCMP 117599)with two Early Paleoceneavian fossils,using an extantburhinid (Burhinusbistriatus vocifer; male, USNM 492371)as a reference (100%). All measurements (in millimeters) are of width of bones.

Tarsometatarsus Tibiotarsus Humerus Species/ fossil (distal) (supracondylar) (distal) B. b. vocifer 11.0 7.4 14.1-14.2 UCMP 117599 10.2 (93%) -- -- Palaeotringalittoralis -- 7.0• (95%) -- Anatalavis rex -- -- 13.2-13.6 a (94-96%)

ß From Olson and Parris (1987). July1995] ShortCommunications andCommentaries 767

R. King, and K. C. Parkes,Eds.). Academic Press, WETMORE,A. 1926. Fossil birds from the Green River Orlando, Florida. depositsof easternUtah. Ann. CarnegieMus. 16: OLsoi•, S. L. 1992. Neogaeorniswetzeli Lambrecht, a 391-402. Cretaceous from Chile (Aves: Gaviidae). J. WOOD, D. S., AND G. D. SCHNELL. 1986. Revised world Vertebr. Paleontol. 12:122-124. inventory of avian skeletal specimens, 1986. OI•soi•,S.L. 1994. A giant Presbyornis(Aves: Anser- AmericanOrnithologists' Union and Oklahoma iformes)and other birds from the PaleoceneAquia BiologicalSurvey, Norman, Oklahoma. Formationof Maryland and Virginia. Proc.Biol. ZusI, R.L. 1984. A functionaland evolutionaryanal- Soc. Wash. 107:429-435. ysis of rhynchokinesisin birds. Smithson.Con- O•.soi•, S. L., Ai•D D. C.P.•gIs. 1987. The Cretaceous trib. Zool. 395:1-40. birds of New Jersey.Smithson. Contrib. Paleo- biol. 63:1-22. Received21 February1994, accepted 17 April 1994.

The Auk 112(3):767-770, 1995

Forest Fragmentation and Nest Predation: Are Experiments with JapaneseQuail EggsMisleading?

DAVID G. HASKELL Sectionof Ecologyand Systematics, Division of BiologicalSciences, Corson Hall, CornellUniversity, Ithaca, New York, 14853, USA

There is recent concern over the status of many (e.g. Sieving 1992,Terborgh 1992,B6hning-Gaese et Neotropicalmigrant bird populations.Reports of de- al. 1993). clining numbersand the continuing loss and deg- The lack of parentaland nestlingactivity and the radationof breedingand overwinteringhabitats have potentially unnatural positioningand appearanceof prompted an upsurgeof interest in the conservation artificial nestscomplicates the interpretation of arti- biology of thesebirds (review papersin Hagan and ficial-nestexperiments. Studies that haveinvestigated Johnston1992). Fragmentation of the breeding hab- these, and other, potential biases(Boag et al. 1984, itat in North America often is cited as one of the Martin 1987, Storaas1988, Yahher and Voytko 1989, factorscontributing to the decline of many species. G6tmark et al. 1990,Reitsma et al. 1990,Roper 1992) Fragmentationis thought to act in two ways. First, have reachedconflicting conclusions as to the utility brood-parasitic Brown-headed Cowbirds (Molothrus of artificial-nest experiments. Basedon the scratch ater)thrive in fragmentedlandscapes, decreasing the marks found on many of the quail in artificial productivityof many species(Brittingham and Tem- nests,Reitsma et al. (1990)suggested that smallmam- ple 1983).Second, fragmentation is widely believed mals may have attemptedto consumethe eggs,but to increaserates of nestpredation, further decreasing failed to break them because of the ' small productivity(e.g. Wilcove 1985, Terborgh 1989, 1992). mouths.Roper (1992) used a similar line of reasoning The evidencethat fragmentationof forestsin east- to accountfor the differenc• between predation rates ern North America increasesrates of nest predation on his real and artificial nestsin the tropics,and con- is based on the results of experimentsin which ar- cluded that quail-eggexperiments were inappropri- tificial nestsbaited with JapaneseQuail (Coturnixco- ate for making comparisonsbetween rates of nest turnix)eggs are usedto comparerates of predation in predation in tropical and temperate habitats. fragmentsof differentsizes (Wilcove 1985,Small and In this paper, I report the resultsof an experiment Hunter 1988; see also Yahher and Scott [1988] who testingthe suggestionsof Reitsmaet al. (1990). I dis- used chickeneggs). There is someevidence for the cusswhether quail-eggexperiments are an appropri- fragmentationeffect based on studiesof real nestsin ate tool for investigatingamong-fragment differences Europe (Moller 1988) and in grasslandhabitats in in the rate of predation on Neotropical migrant bird North America(Patoh's [1994] reanalysis of Best1978, nests.The potentialinappropriateness of usingquail Gatesand Gysel 1978,Johnson and Temple 1990;Gates eggsto estimatedifferences in rates of predation on and Gysel's[1978] analysis included 10 nestsof forest- the nestsof Neotropicalmigrant birds becomesevi- dwelling birds). Despite the absenceof data on the dent when the eggsizes of forest-nestingNeotropical effectsof fragmentationon the nestingsuccess of real migrant birds are comparedto the size of quail eggs nestsof forest-dwellingbirds, the resultsof quail- (Fig. 1). All Neotropicalmigrant passerinesnesting studieshave been widely acceptedas reflectingrel- in forests or scrub in eastern North America have ative trends for rates of predation on real bird nests eggsthat are much smaller than quail eggs.I tested