Earliest tinamous (Aves: Palaeognathae) from the Miocene of Argentina and their phylogenetic position

2005·17.1 MB·English

by  Sara Bertelli

Earliest Tinamous (Aves: Palaeognathae) erom
THE Miocene oe Argentina and Their
Phylogenetic Position
Sara BertellT and Luis M. Chiappe^
ABSTRACT. Several isolated bones oftinamous from Miocene deposits ofSanta CruzProvince (southern
Patagonia, Argentina) are the oldest known remains ofthis paleognath lineage. The specimens includean
incomplete coracoid, proximal end offour coracoids, distal ends oftwo tibiotarsi, and distal ends oftwo
humeri. They represent at least two species but cannot be assigned to any known taxon. A detailed de-
scriptionandphylogeneticinterpretationofthismaterialisprovidedhere.Morphologicaldataofthefossils
are included ina matrixof63 osteologicalcharacters and 34 terminaltaxa incorporating24livingspecies
of Tinamidae in addition to the fossils under study. The cladistic analysis produced 81 optimal trees, in
which the fossils are more closelyrelated to the open-area tinamous (Nothurinae). PlacementoftheSanta
Cruz fossil tinamous betweenthe open-area (Nothurinae) and theforest-dwelling(“Tinaminae”)tinamous
is consistentwith the paleoenvironmentalconditions inferred from the associated fossil fauna.
RESUMEN. Varios fragmentos de huesos detinamidos de depositos delMioceno de laProvincia deSanta
Cruz (sur de Patagonia, Argentina), son los restos mas antiguos que se conocen de este linaje de paleog-
natas. Los espedmenes incluyen un coracoides incompleto, extremos proximales de cuatro coracoides,
extremos distales de dos tibiotarsos yextremos distales de dos humeros, cuya descripcioneinterpretacion
filogenetica son provistas aqui. Estos especimenes representan al menos dos especies, las que no pueden
ser asignadas a ninguntaxonconocido. Los datosmorfologicos de losfosilesaquidescriptossoninduidos
en una matriz de 63 caracteres osteologicosy34 taxonesterminalesqueincluyen24especiesdetinamidos
vivientes ademas de los fosiles. El analisis cladistico produjo 81 arboles optimos en los cuales los fosiles
estan mas relacionados con los tinamidos de areas abiertas (Nothurinae). La ubicacion de los fosiles de
Santa Cruz entre los tinamidos de areas abiertas (Nothurinae) y los de selva (“Tinaminae”) esconsistente
con las condiciones paleoambientalesinferidas a partir de la fauna fosil asociada.
INTRODUCTION 1832, from La Pampa Province (Tambussi, 1987).
A large collection of vertebrate remains from the Two extinct species, Eudromia olsoni Tambussi
continental Lower to Middle Miocene deposits of and Tonni, 1985, and Nothura parvula Tambussi,
southern Patagonia, Argentina (The Fleagle Collec- 1989,have beenfoundinsedimentsfromtheUpper
tion ofthe Museo Argentino de CienciasNaturales Pliocene ofBuenos Aires Province. ReportsofQua-
“Bernardino Rivadavia”), was recovered during a ternary tinamous include several extant species
series of expeditions in the 1980s and early 1990s. from Brazil (Brodkorb, 1963), the Pleistocene
Amongthese remains is a diversecollectionofbirds Crypturellus cf. C. transfaciatus (Campbell, 1979)
(Chiappe, 1991; Noriega and Chiappe, 1993) that from northwestern Peru, and the extinct Nothura
includes several isolated bones of tinamous, for paludosa Mercerat, 1897, from the Pleistocene of
which we provide a detailed description and phy- Argentina. Thus, the Early Miocene tinamous of
logenetic interpretation. the Fleagle Collectionarethe oldestknownremains
The Tertiary, and oldest, fossil record ofTinam- ofthis Neotropical group ofpaleognaths (Chiappe,
idae is restricted to Argentina (Tonni, 1977; Tam- 1991).
bussi and Tonni, 1985; Tambussi, 1987, 1989; The specimens reported here include a partial
Tambussi et al., 1993; Tambussi and Noriega, coracoid, proximal ends of four coracoids, distal
1996). A Late Miocene tinamou was described as ends of two tibiotarsi, and distal ends of two hu-
an indeterminate species of Eudromia Geoffroy, meri (Table 1). Most of this material comes from
the Santa Cruz Formation in the Argentine prov-
1. Department of Ornithology, American Museum of ince of Santa Cruz, from the fossil localities of
Natural History, Central Park West at 79th Street, New Monte Observacion, Monte Leon, and Cahadonde
York, New York 10024. Email: [email protected]
2. Department of Vertebrate Paleontology, Natural las Vacas (Fig. 1). The distal end ofone tibiotarsus
History Museum of Los Angeles County, 900 Exposition comes from beds ofthe middle part ofthe Pinturas
Boulevard, Los Angeles, California 90007. Formation, from the locality ofPortezuelo Sumich,
Email: [email protected] also in the province of Santa Cruz (Fig. 1).
Contributions in Science, Number 502, pp. 1-20
Natural HistoryMuseum ofLos Angeles County, 2005
2 Contributionsin Science, Number 502 Bertelli and Chiappe: EarliestTinamidae
Table 1 Taxonomy, stratigraphic horizon, and locality ofthe specimens described herein. All specimenscome fromthe
Lower to MiddleMiocene ofSanta CruzProvince, Argentina.
Specimen Material Taxonomy Horizon Locailty
Coracoid Tinamidae
MACN-SC-3610 Proximal end Morphotype Cl Santa Cruz Formation Monte Observation
MACN-SC-3613 Proximal end -t- shaft Morphotype C2 Santa Cruz Formation Monte Observacion
MACN-SC-3609 Nearly complete Morphotype Cl or C2 Santa Cruz Formation Monte Observacion
MACN-SC-3611 Proximal end + shaft Morphotype Cl or C2 Santa Cruz Formation Monte Observacion
MACN-SC-3612 Proximal end Morphotype Cl or C2 Santa Cruz Formation Monte Observacion
Humerus Tinamidae
MACN-SC-1449 Distal end Morphotype HI Santa Cruz Formation Monte Observacion
MACN-SC-360 Distal end Morphotype H2 Santa Cruz Formation Canadon de las Vacas
Tibiotarsus Tinamidae
MACN-SC-1399 Distal end Morphotype T1 Pinturas Formation Portezuelo Sumich
MACN-SC-1440 Distal end Morphotype T1 Santa Cruz Formation Monte Leon
ABBREVIATIONS LACM Natural History Museum of Los An-
AMNH American Museum of Natural His- gelesUSCoAunty, Los Angeles, Califor-
BMNH Ntoartyu,rNalewHiYsotrokr,yNMeuwseYuomrk,, LUoSnAdon, LSUMNS Mniua,seum of Natural Science, Louisi-
ana State University, Baton Rouge,
COL UCnoilteecdciKoninOgrdnoimtologica Lillo, Facul- MACN MLouusiesioanAar,geUnStAino de Ciencias Natur-
tad de Ciencias Naturales e Instituto
ales “Bernardino Rivadavia”, Buenos
Miguel Lillo, Tucuman, Argentina
FMNH Field Museum of Natural History, MCZ AMiuresse,uAmrgeonftinCaomparative Zoology,
KU MChuisceaguom, oIlfliNnoaitsu,rUalSAHistory, Univer- HsaacrhvuasertdtsU,niUveSrAsity, Cambridge,Mas-
sity of Kansas, Lawrence, Kansas, MGUH DK GeologiskMuseum,UniversityofCo-
USA
penhagen, Copenhagen, Denmark
MLP Facultad de CienciasNaturalesyMu-
seo de La Plata, Division Paleontolo-
gia de Vertebrados, La Plata, Argen-
tina
PVL Paleontologia de Vertebrados, FacuL
tad de Ciencias Naturales e Instituto
Miguel Lillo, Tucuman, Argentina
UCMVZ Museum of Vertebrate Zoology, Uni-
versity of California, Berkeley, Cali-
fornia, USA
UMMZ Museum of Zoology, University of
Michigan, Ann Arbor, Michigan,
USA
USNM National Museum of Natural Histo-
ry, Washington, D.C., USA
YPM PeabodyMuseum ofNaturalHistory,
Yale University, New Haven, Con-
necticut, USA
GEOLOGICAL SETTINGS
The material describedherewasfoundinsediments
ofthe Pinturas and Santa Cruzformationsinsouth-
ern Argentina. The Pinturas Formation (Bown et
ah, 1988; Bown and Larriestra, 1990) is a pyro-
Figure 1 Lower to Middle Miocene localities where the clastic and epiclastic aeolian depositexposed inthe
studied specimens come from (modified from Marshall, upper valley of the Rio Pinturas in southern Pata-
1976). gonia (Fig. 1). The Santa Cruz Formation is ex-
Contributions in Science,Number 502 Bertelli and Chiappe: EarliestTinamidae 3
posed over much of southern Patagonia (Ameghi- SYSTEMATIC PALEONTOLOGY
no, 1906; Feruglio, 1938). This formation differs Aves Linnaeus, 1758
from the Pinturas Formation in having less unre- Palaeognathae Pycraft, 1900
cycled pyroclastic sediment, more fluvially depos- Tinamidae Gray, 1840
ited epiclastic sand bodies, significant marine inter-
calations, less paleodune sand, and relatively im- DIAGNOSIS. Paleognathous birds with supra-
mature paleosols (Fleagle et ah, 1995). orbital bones (i.e., superorbital ossicles of Parker
The sites in the Pinturas and Santa Cruz forma- [1866]) roofing the orbit, lacrimal and ectethmoid
tions have yielded an important collection ofMio- partially fused into a lacrimal-ectethmoidcomplex
cene fossil mammals, in particular primates, mar- (Cracraft, 1968), fossae piercing the interorbital
septum (Bertelli, 2002), a sternum lacking a rostral
supials, and rodents (Ameghino, 1906; Marshall,
1976, 1990; Barrio et ah, 1984; Bown and Fleagle, eaxntderbneaalrisnpigneel(oPnagrakteerd, l1a8t6e6ra;lBtaruambeecluleatea(k,Ble1d9s9o3e),
1993). Among birds, representatives of Rheidae, 1988), a coracoid with a proximodorsal foramen
Ciconiiformes, Galliformes, Anseriformes, and (Parker, 1866) and lacking dorsodistal foramina
Cruiformes are present in the Santa Cruz Forma- (Bertelli, 2002), a humerus with a shallow trans-
tion (Ameghino, 1891, 1895); whereas membersof verse ligamental groove (Lee et ak, 1997) and a
the Falconiformes are known from both the Santa ventral condyle longer than the dorsal condyle
Cruz and Pinturas formations (Ameghino, 1895, (Clarke and Chiappe, 2001), and a strong,rounded
1899; Chiappe, 1991). The PinturasFormationhas depression between tibiotarsal condyles (Bertelli,
also yielded the oldest known tinamou, a specimen 2002
).
included in this study, and indeterminate remains REFERENCED SPECIMENS AND TAXONO-
of members of the Passeriformes (Noriega and MY. All studied specimens constituteisolated,right
Chiappe, 1993) and Strigiformes (Chiappe, 1991). elements (Eigs. 2-4): MACN-SC-3609, a nearly
The environmental conditions prevailing during complete coracoid; MACN-SC-3610 and MACN-
deposition of the Pinturas Formation varied. Pa- SC-3612, two proximal ends ofcoracoids;MACN-
leoenvironmental studies indicate thatthe lowerse- SC-3611 and MACN-SC-3613, two proximal ends
quence accumulated under warm, subtropical con- and shafts of coracoids; MACN-SC-1449 and
ditions and that the subsequent depositional se- MACN-SC-360, two distal ends of humeri; and
quences may have been characterized by periodi- MACN-SC-1399 and MACN-SC-1440, two distal
cally drier conditions and more open areas (Bown ends of tibiotarsi. The size of all these elements
agrees well withthatexpectedfortinamousslightly
and Larriestra, 1990; Genise andBown, 1994).The
smaller than the Spotted Nothura, Nothura macu-
deposition ofthe Santa Cruz Formation appears to losa Temmink, 1815. There are two morphotypes
have occurred under warm, humid conditions, as of coracoids, two morphotypes of humeri, and a
indicated by calcareous steinkerns of trees. The single morphotype of tibiotarsus (Table 1). Al-
presence ofnests ofscarabaeid beetles and burrows though none of these morphotypes can be associ-
ofsolitary bees suggests the existence ofopenareas ated to one another on the basis of anatomical ev-
(Genise and Bown, 1994). Thus, the Pinturas and idence, differences between the two coracoids and
Santa Cruz formations appear to have been depos- the two humeri (see Anatomical Description sec-
ited at a time when open areas were expanding. tion) indicate that the referred specimens represent
Ameghino (1906) and laterworkersregardedthe at least two species. Because these specimens can-
Pinturas Formation as slightly older than the Santa not be assigned to any known living or extinctspe-
Cruz Formation (Frenguelli, 1931; Barrio et ah, cies, we believe that they represent new species.
1984). However, others have questioned the dis- However, given the fragmentary nature of the ma-
ttionctthieveSnaensstaofCrthuezPFionrtumraatsiofnau(nPaasacnudalatatnrdibuOtderdei-t terLiaOl,CwAeLIreTfYraiAnNfrDomHnOaRmIiZngONth.emS.ee Table 1 for
man-Rivas, 1971; Marshall, 1976). Bown and Lar- details on the locality and horizon for each speci-
men.
riestra (1990) described the Pinturas deposits as a ANATOMICAL DESCRIPTION. Anatomical
separate formation, distinct from the Santa Cruz
Formation. Biostratigraphic evidence, mainly de- nomenclature mainly follows Baumel et ak (1993);
rived from the record of paleothentid marsupials, certain structures not cited herein follow Howard
(1929). The Latin terminology used by Baumel et
supports an Early to Middle Miocene age for the
Pinturas beds (Bown et ak, 1988; Bown and Lar- wakher(e1a9s93)ostiesolroegtiacianledstfrourctmuuressclaerse adnesdcrliibgeadmewnittsh,
riestra, 1990; MacFadden, 1990; Fleagle et ak, the English equivalents of the Latin terms.
1995). Radioisotopic analysis supports an age be- Coracoid. All studied specimens (MACN-SC-
tween 17.5 and 16.5 Ma for the mammal-bearing 3609,MACN-SC-3610,MACN-SC-3611,MACN-
beds ofthe Pinturas Formation and an age younger SC-3612, and MACN-SC-3613) exhibit a foramen
than 16.5 Ma for the localities of Monte Obser- on the dorsal surface, just distal to the triangular-
vacion and Monte Leon from the Santa Cruz For- shaped scapular facet (Eigs. 2A, B, E, E). This fea-
mation (Fleagle et ak, 1995). ture is here interpreted as a synapomorphy ofTin-
4 Contributions in Science, Number 502 Bertelli and Chiappe: EarliestTinamidae
A
mm
5
Figure 2 Coracoids. A, MACN-SC-3609, dorsal view; B, MACN-SC-3611, dorsal view; C, MACN-SC-3613, ventral
view; D, MACN-SC-3610, ventral view; E, MACN-SC-3612, dorsal view; F, MACN-SC-3610, dorsalview. Anatomical
abbreviations: ap, acrocoracoidprocess; bt, brachialtubercle;f,foramen;gl,grooveforligamentumacrocoracohumerale;
hf, humeral articular facet; il, impression for insertion of musculus biceps brachii; im, impression for the origin of
ligamentum sternoprocoracoideum ofmembrana sternocoracoclavicularis; pp,procoracoidprocess;sf,scapulararticular
facet; sg, supracoracoidalgroove; st, sternal articular facet.
Figure2 Continued.
6 Contributionsin Science, Number 502 Bertelli and Chiappe: EarliestTinamidae
C D
Figure 3 Humeri. A, MACN-SC-1449, cranial view; B, MACN-SC-360, cranial view; C, MACN-SC-1449,dorsalview;
D, MACN-SC-360, dorsal view. Anatomical abbreviations: al, attachmentofmusculuspronatorbrevis (Howard, 1929);
am, attachmentofligamentumarticulatecraniale (i.e.,anteriorarticularligamentofHoward [1929]);dc,dorsalcondyle;
df,distalfossae;dp,dorsalsupracondylarprocess;mb,impressionforinsertionofmusculusbrachialis;vc,ventralcondyle.
amidae. Although a similar condition has been de- distal ridge ofthe procoracoidprocess istentatively
scribed for Opisthocomidae (Ericson, 1997), the identified as a surface for the origin of the memb.
presence of other tinamid synapomorphies in the sternocoracoclavicularis (Baumel etah, 1993). Like
acrocoracoid process of the Santa Cruz fossils (see in many other birds (including the outgroups used
below) supports our interpretation. Immediately in this study), the surface of the humeral facet of
above the scapular facet, on the dorsal surface of allofthesecoracoidsisslightlyconvexandoriented
these coracoids, there is a deep fossa excavated on laterally (Figs. 2A, B, E, F).
the upper edge of the procoracoid process. Distal On the proximal end of MACN-SC-3610 and
to the base of this process, there is a distinct im- MACN-SC-3613, the acrocoracoid process is slen-
pression for the ligamentumsternoprocoracoideum der and itprojects beyond the proximal edge ofthe
of the membrana sternocoracoclavicularis (Baumel humeral articular facet (Figs. 2E, F). The poorly
etah, 1993). Unlikethe tinamous CrypturellusBra- developed acrocoracoid process ofthese specimens
bourne and Chubb, 1914, Nothura Wagler, 1827, approaches theconditionpresentin mosttinamous,
Nothoprocta Sclater and Salvin, 1873, Eudromia, differing fromthestrongerdevelopmentseeninEu-
Tinamotis Vigors, 1837, Rhynchotus Spix, 1825, dromia, Tinamotis, and Nothocercus Bonaparte,
and Taoniscus Gloger, 1842, the base of the pro- 1856, in which the acrocoracoid process reaches
coracoid process of the Santa Cruz coracoids does the development seen in galliforms. Immediately
not project distally into a ridge (Figs. 2A, B). This distal to the acrocoracoidprocess, there isadistinct
Contributions in Science, Number 502 Bertelli and Chiappe: EarliestTinamidae 7
A B
impression for the insertion ofthe musculus biceps MACN-SC-3613 as well as from that of the tina-
brachii (Figs. 2E, F). On the ventral border of this mous Nothocercus, Taoniscus, Nothura, Notho-
impression, a distinctivelinearscarprojectsdistally. procta, and Rhynchotus, and the condition in gal-
In MACN-SC-3610, the brachial tubercle pro- liforms, in which the supracoracoidal groove and
jectsstronglyonthemedialsideoftheacrocoracoid that for the lig. acrocoracohumerale are confluent.
process as well as projecting ventrally, toward the The only specimen preserving the coracoidal
triossial canal (Figs. 2D, F). In medial aspect, this shaft, MACN-SC-3609, is narrowandelongatedin
projection gives a concave appearance to the distal dorsal aspect (Fig. 2A). As in most othertinamous,
margin of the clavicular articular facet. Only in its distal end shows no evidence ofpneumatization
Tinamus Hermann, 1783, Eudromia, and Cryptu- (among tinamous, the presence ofdistal coracoidal
rellus does the brachial tubercle project toward the pneumatization near to the scar of the musculus
triossial canal. sternocoracoidei is only present in Nothura and
On the ventral surface of MACN-SC-3610, a Nothoprocta).
shallow groove for the origin of the ligamentum The lateral angle ofthe distal end ofMACN-SC-
acrocoracohumeraleextends fromtheapexandlat- 3609 is broken and the morphology of the lateral
eralsurface oftheacrocoracoidprocess;thisgroove process cannot be determined. As in most tina-
contacts the margin of the clavicular facet (Figs. mous, the angular margin of this coracoid is trun-
2D, F). In MACN-SC-3610, this groove does not cated. However, this condition contrasts with the
converge with the dorsal margin of the supracora- pointed aspect of the angular margin of the cora-
coidal groove. Such a condition differs fromthatof coids of the tinamous Eudromia and Tinamotis. A
8 Contributionsin Science, Number 502 Bertelli and Chiappe: EarliestTinamidae
Figure 4 Tibiotarsi. A, MACN-SC-1339, cranial view; B, MACN-SC-1440, cranial view; C, MACN-SC-1339, medial
view; D, MACN-SC-1440, medial view. Anatomical abbreviations: ct, carpal trochlea; dt, depressionfortheintercotylar
prominence; ec, extensor canal; Ic, lateral condyle; me, medial condyle; md, medial epicondyle depression;me, medial
epycondyle; st, supratendinal bridge.
truncated aspect ofthe angular margin ofthe distal separates these condyles. The distal margin of the
coracoid is also typical ofgalliforms. In the medial dorsal condyle is flat.
aspect of MACN-SC-3609, the areas occupied by As in most tinamous, the flexor process projects
the ventral and dorsal sternalfacetsarecomparable distally as faras the ventralcondyle. OnlyinNoth-
insize, andthe distalmarginofthisfacetisstraight, ocercus, Nothoprocta, and Taoniscusdoesthispro-
as observed in the examined tinamous (Fig. 2A). cess project farther distally than the ventral con-
Humerus. On the cranial surface ofbothhumeri, dyle.
MACN-SC-1449 and MACN-SC-360, the main The origin for the musculus brachialis, on the
axis of the ventral condyle is longer than that of cranial surface of the humerus, is developed as a
the dorsal condyle (Figs. 3A, B). This condition is flatscar (Figs. 3A, B) insteadofasthefossa ofother
presentin allexamined tinamousexceptTinamotis, basal neornithine birds. This faint scar is crescent-
where the main axis of both condyles is subequal shaped inMACN-SC-1449 andMACN-SC-360,as
in length. Ashallowandwide intercondylarfurrow it is in Crypturellus. However, its shape is less an-
Contributionsin Science, Number 502 Bertelli and Chiappe: EarliestTinamidae 9
Figure4 Continued.
gular and broader than in Nothura and Notho- ticulate craniale (i.e., anterior articular ligament of
procta. Howard [1929]) formsacircularanddistinctivede-
In MACN-SC-1449 and MACN-SC-360, the pression (Figs. 3A, B). This depression differs from
ventral supracondylar tubercle for the attachment that ofall other tinamous in that it is very strongly
ofthe musculus pronator brevis (Howard, 1929) is developed.
located on the cranioventral margin (Figs. 3A, B). On the dorsal border of MACN-SC-1449 and
This is generally the condition of species of Tin- MACN-SC-360, the dorsal supracondylar process
amidae, although it is also present in many other is developed as a round, conspicuoustubercle(Figs.
neornithine birds. Only in the tinamous Tinamotis 3A-D). This condition is typical of most tinamous
and Eudromia is this pit directly on the cranial sur- except Nothocercus bonapartei Gray, 1867, Taon-
face. Just distal to this pit, on the cranial surface of iscus, Tinamotis, and Eudromia, which lack such a
both humeri, the attachment ofthe ligamentum ar- tubercle. Specimen MACN-SC-360 differs from
a
10 Contributionsin Science, Number 502 Bertelli and Chiappe: EarliestTinamidae
Figure5 Coracoids ofextanttinamous (seecharacters21-23,27-28 ofAppendix2).A,NothocercusnigrocapillusGray,
1867, ventral view; B, Crypturellus soui Hermann, 1783, ventral view; C, Tinamotis pentlandi Vigors, 1837, ventral
view; D, Nothoprocta dnerascens Burmeister, 1860, ventral view; E, Nothura darwinii Gray, 1867, ventral view.
most other tinamous examined in thatanotherdor- ally than the lateral condyle and its proximal ex-
sally projected tubercle is developed proximal—to tension is shorter than ofthe latter (Figs. 4A, B). In
the dorsal supracondylar process (Figs. 3B, D) cranial view, the outline of the lateral condyle is
vaguely similarcondition has been observed in Tin- straight and of subequal width along its extension.
amus, Crypturellus tataupa Temminck, 1815, and This character state is present in mosttinamousex-
Crypturellus parvirostris Wagler, 1827. Thus, we cept for Tinamus, Nothocercus, and Eudromia, in
regard this condition as an autapomorphy of which the distal end ofthe lateralcondyle is broad-
MACN-SC-360. er than its proximal end, with an acuminate prox-
Two fossae can be observed in dorsal view on imal margin. The proximal edge ofthe medialcon-
the mostdistal end ofbothspecimens (Figs. 3C,D). dyle ofMACN-SC-1440 iswelldefinedandslightly
While two comparable fossae are present in Taon- more deflected medially than in MACN-SC-1399
iscus, Nothura, Nothoprocta, Rhynchotus, Eu- (Figs. 4A, B). This deflection may be associated
dromia, and Tinamotis, three are presentinthefor- with the relative deepening and medial displace-
est-dwelling tinamous and in galliforms. In con- ment ofthe impression ofthe ligamentumintercon-
trast, only one fossa appears to be present in the dylaris (Livezey, 1997).
humeri ofratites. Onthecaudal surface ofMACN- As in all tinamous examined, MACN-SC-1440
SC-1449 and MACN-SC-360, the olecranon fossa and MACN-SC-1399 present a strong, rounded
is weakly defined. cranial depression between the condyles that at
Tibiotarsus. On the cranial surface of the two maximal flexion accommodates the intercotylar
preserved tibiotarsi, MACN-SC-1399 and MACN- prominence of the tarsometatarsus. In contrast to
SC-1440, the extensor canal is medially placed, some tinamous, such as Nothocercus, Tinamus,
opening adjacent to the medial condyle (Figs. 4A, and Crypturellus, the depression ofthe Patagonian
B). Both specimensexhibitanossifiedsupratendinal fossils is not bordered proximally by a distinctive
bridge proximal to the latter condyle. ridge.
In MACN-SC-1399 and MACN-SC-1440, the In medial view, the medial epicondyle forms a
lateral condyle extends slightly more proximally small and pointed projection enclosed by a deep
than the medial condyle, although not as far prox- excavation (Figs. 4C, D). Only in Crypturellus and
imally as the proximal extension of the supraten- Nothocercus is this depression more excavated on
dinal bridge (Figs. 4A, B). The tibiotarsi of these the cranial margin and developed as a fossa.
fossil tinamous share with those of most tinamous On the caudal surface of MACN-SC-1440 and
the presence of a medial condyle that is narrower MACN-SC-1399, the carpal trochlea is wide; the
transversely than the lateral condyle. Only in the margins on either side of it are broken (Figs. 4C,
Andean species of Nothoprocta (i.e., Nothoprocta D).
ornata Gray, 1867, and Nothoprocta perdicaria
Kittlitz, 1830) are both condylesofsubequalwidth. CLADISTIC ANALYSIS
The fossil tibiotarsi also resemble the general con-
dition ofthose ofextanttinamous intheelongation Morphological data of the fossils here described
ofthe condyles. The medial condyle ofMACN-SC- were included in a matrix of 63 osteological char-
1399 and MACN-SC-1440 projects farther crani- acters (Figs. 5-7; Appendices2, 3). The 34 terminal