The first Cenozoic mammal fauna from the Chilean Altiplano

BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors nonprofit publishers academic institutions researchlibraries and research funders in the common goal of maximizing access to critical research

THE FIRST CENOZOIC MAMMAL FAUNA FROM THE CHILEANALTIPLANOAuthor(s) JOHN J FLYNN DARIN A CROFT REYNALDO CHARRIER GEacuteRARD HEacuteRAIL andANDREacute R WYSSSource Journal of Vertebrate Paleontology 22(1)200-206 2002Published By The Society of Vertebrate PaleontologyDOI httpdxdoiorg1016710272-4634(2002)022[0200TFCMFF]20CO2URL httpwwwbiooneorgdoifull1016710272-4634282002290225B02003ATFCMFF5D20CO3B2

BioOne (wwwbiooneorg) is a nonprofit online aggregation of core research in the biological ecological andenvironmental sciences BioOne provides a sustainable online platform for over 170 journals and books publishedby nonprofit societies associations museums institutions and presses

Your use of this PDF the BioOne Web site and all posted and associated content indicates your acceptance ofBioOnersquos Terms of Use available at wwwbiooneorgpageterms_of_use

Usage of BioOne content is strictly limited to personal educational and non-commercial use Commercial inquiriesor rights and permissions requests should be directed to the individual publisher as copyright holder

200

Journal of Vertebrate Paleontology 22(1)200ndash206 March 2002q 2002 by the Society of Vertebrate Paleontology

RAPID COMMUNICATION

THE FIRST CENOZOIC MAMMAL FAUNA FROM THE CHILEAN ALTIPLANO

JOHN J FLYNN1 DARIN A CROFT1 REYNALDO CHARRIER2 GERARD HERAIL3 and ANDRE R WYSS4

1Department of Geology The Field Museum Chicago Illinois 60605 jflynnfieldmuseumorg2Departamento de Geologıa Universidad de Chile Santiago Chile

3IRD 209-213 Rue La Fayette 75010 Paris France4Department of Geological Sciences University of California Santa Barbara California 93106

Despite its richness South Americarsquos Cenozoic mammal re-cord is strongly biased geographically towards a small portionof the continent mainly Patagonia The rapidly growing list ofmajor Cenozoic localities at lower latitudes thus marks a sig-nificant advance in our understanding of mammalian evolutionin South America (see summaries in Flynn and Swisher 1995Flynn and Wyss 1998)

This paper reports the discovery of the first Cenozoic mam-mal fauna known from the Chilean Altiplano It is part of anongoing collaborative effort to sample faunas of a variety ofages across a large latitudinal transect of western South Amer-ica the goal of which is to elucidate temporal patterns of pro-vincialism within the continent as well as the tectonic and up-lift history of the Andes Mountains and associated paleoenvi-ronmental changes An isolated well-preserved fossil mammalhumerus was discovered in 1992 in northern Chile by RC GHand Nelson Munoz and referred to the toxodontid notoungulateNesodon (Charrier et al 1994a) Our team returned to the areain 1998 to collect and assess its potential for more extensivepaleontological investigations (Flynn et al 1999)

Only two Cenozoic mammal specimens were known fromnorthern Chile prior to the discovery of the Chucal Fauna bothfrom the Huaylas Formation (late Miocene) The first a no-toungulate right lower jaw fragment (MLP 86-VIII-10-1) col-lected by D Pacci in 1969 in the area of Caragua (at the con-fluence of the quebradas of Lupica and Belen approximately188 259 S 698 359 E) was identified as a mesotheriine withaffinities to Eutypotherium (Bargo and Reguero 1989) Thesecond specimen a skull of the mesothere Typotheriopsis spwas probably recovered from the same locality (Salinas et al1991) The Huaylas Formation and its mesotheres are almostcertainly younger than the fossiliferous horizons described inthis paper based on dates bracketing that formation and strati-graphic superposition (Naranjo and Paskoff 1985 Munoz andCharrier 1996 Garcıa et al 1997)

Approximately contemporaneous or slightly younger faunasfrom Bolivia include Quebrada Honda (MacFadden and Wolff1981 MacFadden et al 1990) Nazareno (Oiso 1991) Cerdas(Villarroel 1978 MacFadden et al 1995) and small collec-tions from the Choqueta and Quehua formations (Marshall andSempere 1991) South American Land Mammal lsquolsquoAgersquorsquo (SAL-MA) chronology follows Flynn and Swisher (1995) The Fria-sian SALMA is controversial (Flynn and Swisher 1995 Mad-den et al 1997) we make a distinction between usage of Fria-sian in its traditional sense (Friasian sensu lato) of subsumingthe Mayoan Colloncuran and Friasian sensu stricto SALMAsand the termrsquos more restrictive definition (Friasian sensu stricto)whereby it is applied to the temporal interval characterized by

the type assemblage in southern Chile and correlative faunas(if indeed this biochron is valid)

Abbreviations FMNH Field Museum of Natural HistoryChicago MACN Museo Argentino de Ciencias NaturaleslsquolsquoBernardino Rivadaviarsquorsquo Buenos Aires MLP Museo de LaPlata La Plata SALMA South American Land MammallsquolsquoAgersquorsquo sl sensu lato ss sensu stricto Deciduous teeth areindicated with a lsquolsquodDrsquorsquo preceding the tooth position All spec-imens will receive National Museum of Natural History (San-tiago) collection numbers at the completion of this projectmdashfield numbers are reported below in the format CHILE-ALTI-PLANO-DATE-FIELD NUMBER (eg C-ALT-7-21-98-43)

GEOGRAPHIC AND GEOLOGIC SETTING

The study site is located northwest of Salar de Surire (188439 S 698 109 W) in outcrops of the syntectonic fluvio-lacus-trine Chucal Formation exposed on both limbs of a major NndashSoriented growth anticline (Fig 1) The Chucal Formation un-conformably overlies the early Miocene Lupica Formation andis overlain conformably by the Lauca Formation (Riquelme1996 Riquelme and Herail 1997) Consisting of two membersit is composed of approximately 450 m (west limb 100ndash200m on the east limb) of sandstone conglomerate and mudstonewith numerous pyroclastic intervals (Charrier et al 1994aChavez 2001) The formation varies considerably in thicknessfrom west to east because of different paleodepositional envi-ronments within the basin (more dominated by lacustrine facieson the west and coarse fluviatile sediments on the east) anddevelopment of progressive syndepositional unconformitiesthinning the sequence on the east side (the most significantunconformity being D3 [of Charrier et al 2000 and Herail etal in review] in the upper part of the sequence)

The lower third of the formation including the lower datedwhite tuff (see below) is characterized by a fining-upwards se-quence The reverse is true in the upper third of the formationwith the uppermost layers consisting of fluvial conglomeratesA dated upper white ash layer (see below) occurs just abovethese conglomerates The middle third of the formation consistsof open lake deposits containing ostracodsmdashthis unit is espe-cially well developed on the western limb of the anticline Leafimpressions and pollen have been recovered from several ho-rizons in the lower to middle parts of the formation (Charrieret al 1994b)

Mammalian fossils have been recovered from several dozenlocalities in both members of the Chucal Formation spanningmuch of the thickness of the formation The vast bulk of thelocalities and specimens lie within the middle of the sequence(below unconformity D2D29) Lacking evidence that the sam-pled horizons are faunally distinct and given the stratigraphic

201FLYNN ET ALmdashMIOCENE MAMMALS FROM THE CHILEAN ALTIPLANO

FIGURE 1 Geography and geology of the Chucal Formation The map series indicates the location of the study area within South America(left) and Chile (middle) and a schematic geologic map (right) for the Chucal Formation in this region

TABLE 1 Miocene Chucal Fauna Chile taxonomic faunal list

MammaliaNotoungulata

ToxodontidaeNesodon imbricatus

MesotheriidaeMesotheriinae

Undescribed Taxon A aff Microtypotherium spUndescribed Taxon B aff Microtypotherium spUndescribed Taxon C aff Typotheriopsis Plesiotypotherium

or EutypotheriumHegetotheriidae

Hegetotheriinaecf Pseudohegetotherium torresi

LitopternaMacraucheniidae

Theosodon sp indetRodentia

ChinchillidaeChinchillinae

Undescribed TaxonTiny rodent indet

XenarthraCingulata

Glyptodontoidea indet (likely Glyptodontidae)

proximity for most of the material we provisionally considerthe assemblage to represent a single fauna herein named theChucal Fauna

DESCRIPTION OF CHUCAL FAUNA

A minimum of nine mammals distributed among a wide di-versity of taxa have been identified from the Chucal Formation

(Table 1) At least six of these species can be identified to whathas traditionally been considered the generic level

Notoungulates

Notoungulates are the most diverse and the most commonelement of the Chucal Fauna with at least five species repre-sented (Table 1) The toxodontid Nesodon is represented byexcellent material including a partial skull (Fig 2A) isolatedteeth and various postcranial elements Nesodon is best knownfrom the rich Santacrucian (late early Miocene) deposits alongthe Atlantic coast of Patagonia (Scott 1912) Identification ofthe Chucal Nesodon as N imbricatus is based on sizemdashits di-mensions are very similar to those provided by Scott (1912) forN imbricatus and are greater than those provided for otherspecies of Nesodon (which in general are poorly characterizedand not certainly distinct) There are less definitive reports ofNesodon from slightly younger strata of Friasian sl and Col-loncuran age (early middle Miocene) from the Andean pied-mont (Bondesio et al 1980) Bolivian Altiplano (Douglas1914) and the lsquolsquoLa Vela Seriesrsquorsquo near San Juan Venezuela(Schaub 1935)

Mesotheres are the most common fossils encountered in theChucal Formation (Fig 2B) Despite the abundance of mesoth-eriid material from Argentina and Bolivia (or perhaps becauseof it) the taxonomy and systematics of the group remain un-clear (Pascual and Bondesio 1985) There has been no recentcomprehensive review of mesothere systematics and it is un-certain as to how variation (age gender intraspecific interspe-cific) affects the characters (eg individual tooth sizes and pro-portions lobe shapes on teeth degree of imbrication) generallyused to diagnose taxa (see Pascual and Bondesio 1985) Hyp-sodont teeth in other notoungulates typically undergo dramatic

202 JOURNAL OF VERTEBRATE PALEONTOLOGY VOL 22 NO 1 2002

FIGURE 2 Representative mammalian fossils from the Chucal Formation A 5 Nesodon imbricatus partial skull (C-ALT-7-21-98-43 upper 5right lateral view lower 5 crown view) B 5 mesotheriine Undescribed Taxon A (C-ALT-7-18-98-28 upper 5 left lateral view lower 5 palatalview) Scale bars equals 5 cm

changes in size shape and occlusal features during wear (Mad-den 1990 Croft 2000) making it reasonable to also expectsuch wear-related changes in mesotheriids There appear to beat least four (Francis 1965) to six (adding Bolivian taxa Vil-larroel 1974a b) potentially valid mesotheriine lsquolsquogenerarsquorsquo Chu-cal Formation mesotheres share the diagnostic attributes of me-sotheriines (Francis 1965 Villarroel 1974a) including loss ofupper I2ndashP2 and lower i3ndashp3 among other characters Mesoth-eriines have previously been found only in Friasian sl or youn-ger faunas (Marshall et al 1983 Marshall and Sempere 1991)A comprehensive review of mesotheriine variation is beyondthe scope of this report and therefore we defer more precisetaxonomic placement of the Chucal specimens Nonetheless theChucal mesotheriines clearly represent at least three distincttaxa and each possesses at least one character state falling out-side the known range of morphological variation in all othernamed mesotheriids indicating that each may represent a newspecies Assuming the various localities in the Chucal Forma-tion represent a single fauna (and all the mesothere materialcomes from localities spanning less than 50 m below uncon-formity D2D29) this level of species diversity equals or ex-ceeds that of all other Cenozoic South American faunas

Chucal Formation mesotheriine Undescribed Taxon A is rep-resented by a palate (Fig 2B) and a mandible They resembleMicrotypotherium in size and morphology the smallest known

mesotheriine (Villarroel 1974b) although the palate differs inhaving significantly shorter M2 and M3 Taxon A is uniqueamong mesotheriines in having a single upper premolar allother mesotheriines have two permanent (and three deciduous)premolars

Undescribed Taxon B is represented by several maxillae andpalates It is distinguished from Taxon A (which it otherwiseclosely resembles) by shorter premolars (similar in width toTaxon A but similar in length to Undescribed Taxon C below)slightly smaller size and convex ectoloph The P4 is wider thanlong in Taxon B a unique character among mesotheriines

Undescribed Taxon C is represented by a palate a fragmen-tary mandible and various teeth but its affinities are enigmaticIt superficially resembles Eutypotherium in some respects butcompares closely to Typotheriopsis and Plesiotypotherium inthe degree of tooth imbrication (greater than in Eutypotheriumand Microtypotherium) Taxon C also possesses upper premolarfeatures (extremely quadrangular P3ndash4 a deep lingual sulcus)that appear to be uniquely derived among mesotheriines Atapproximately two-thirds the size of Taxon A Taxon C is oneof the smallest mesotheriines known The only smaller mesoth-eriine is a specimen from Bolivia referred by Oiso (1991) toPlesiotypotherium It is half the size of Taxon C but the re-mainder of its morphology has not yet been compared closelyto the other Plesiotypotherium material from that locality and


FIGURE 3 Fossil and modern chinchilline rodent specimens empha-sizing presence of three transverse plates in each cheek tooth crownA partial right maxilla from the Chucal Formation in crown view (C-ALT-7-20-98-38 and 39) B portion of right maxilla of modern moun-tain viscacha Lagidium peruanum (FMNH 49743 [Mammalogy]) incrown view Scale bar equals 5 mm

therefore we currently consider it of uncertain taxonomic affin-ity Thus we currently view Taxon C as distinct from but pos-sibly related to Typotheriopsis Plesiotypotherium andor Eu-typotherium

Hegetotheres are represented by various jaw fragments teethand postcranial elements We tentatively refer this material toa single taxon most similar to Pseudohegetotherium torresiThe Chucal taxon shares a suite of hegetotheriid synapomor-phies (including hypselodont I1 hypselodont molars lingualface of molars developed as a flat wall labial face of lowermolars bilobed and cementum present Cifelli 1993 Croft2000) It lacks derived features that would indicate membershipin the pachyrukhine clade and among the probably paraphyleticlsquolsquohegetotheriinesrsquorsquo it has derived features precluding assignmentto the oldest members (ie Ethegetotherium Prohegetother-ium and Hegetotherium) The Chucal taxon most closely re-sembles Pseudohegetotherium torresi from the Chasicoan al-though lsquolsquohegetotheriinesrsquorsquo from Friasian sl assemblages remainlittle studied If additional specimens from the Chucal Forma-tion corroborate the presence of Pseudohegetotherium it wouldrepresent the northernmost record of the taxon

Litoptern

The Chucal Formation macraucheniid litoptern is representedonly by forelimb and hind limb elements including proximalparts of metatarsals 2ndash4 These are large and subequal in sizesuggesting assignment to the Macraucheniidae (rather than tothe smaller monodactyl Proterotheriidae) Systematics withinthe family Macraucheniidae are in a state of lsquolsquogeneral disrepairrsquorsquo(Cifelli and Guerrero 1997298) Theosodon has been reportedfrom the Colhuehuapian (Simpson 1935 Soria 1981) throughthe Chasicoan (Pascual 1966)mdasha temporal range of some 10million yearsmdashbut many of the included taxa and occurrencesare based on fragmentary remains of questionable taxonomicutility (Cifelli and Guerrero 1997)

Rodents

The chinchillid from the Chucal Formation is extremely in-teresting It is represented by excellent dental cranial and post-cranial material from at least two individuals from a single

locality Its derived characters include hypselodont cheek teethocclusal surfaces of cheek teeth consisting of a series of trans-verse plates (Fig 3A) and upper tooth rows convergent ante-riorly suggesting assignment either to Chinchillidae or Dino-myidae We favor the former based on the following derivedcharacter states (Vucetich 1989) plates extend to tooth bases(making occlusal morphology relatively constant with wear)plates closely appressed and separated by little or no cementumenamel thin in places but variable in thickness and incisorssmall relative to the cheek teeth The Chinchillidae is dividedinto Lagostominae (including the modern plains viscacha) andChinchillinae (including chinchillas and the mountain visca-chas) based primarily on the number of transverse plates ineach cheek tooth The Chucal chinchillid has three transverseplates extending from the crown to the base of the cheek teethan apomorphy shared with chinchillines (juvenile Santacrucianlagostomines have three plates on the occlusal surface but onlytwo towards the base of the teeth G Vucetich pers comm)The fossil record of the Chinchillidae is extensive ranging backto the lsquolsquoTinguiriricanrsquorsquo of central Chile (pers obs) and the De-seadan of Bolivia (Vucetich 1991) However this record con-sists almost entirely of lagostomines the oldest published rec-ord of chinchillines being from the Lujanian of Peru (Walton1997) The presence of this new species in the middle Mioceneof Chile would represent a significant temporal range extension(some 15 million years) for the Chinchillinae This occurrencewould support Vucetich and Verzirsquos hypothesis (G Vucetichpers comm) of an Andean montane origin for the Chinchilli-nae and marked faunal provinciality for that region The onlyother rodent material from the Chucal Formation is a tiny iso-lated incisor of an indeterminate taxon

Glyptodont

The glyptodontoid material from the Chucal Formation isvery poor consisting of a small number of complete osteodermsand a larger number of fragments They are small and hexag-onal with the best-preserved element showing an oval centerBecause they are similar to the osteoderms from any numberof named glytodontoids we conservatively consider this ma-terial indeterminate within the group

AGE AND CORRELATION

The fauna is directly constrained by three bracketing radio-isotopic dates from the Cerro Chucal sequence (Riquelme1996 Charrier et al 2000 Worner et al 2000 Chavez 2001Herail et al in review) The first a KndashAr date from an ash inthe upper portion of the underlying Lupica Formation indicatesthe fossiliferous layers are younger than 217 6 08 Ma Thesecond is a 40Ar39Ar date of 1879 6 011 Ma from a whitetuff within the lower member of the Chucal Formation Thethird is a KndashAr date from a white ash near the top of the uppermember of the Chucal Formation which indicates that themammalian fossils are older than 112 6 05 Ma

Dates from elsewhere in this region (Naranjo and Paskoff1985 Munoz and Charrier 1996 Garcıa 1996 Garcıa et al1997) further constrain the age of the base of the Chucal For-mation to be younger than 19 Mamdashthese include additionaldates from the older Lupica Formation (186 6 07 Ma [uppermember] 231 6 07 Ma [top of middle member]) and thetemporally correlative Oxaya Formation (193 6 08 196 607 and 199 6 11 Ma [KndashAr and 40Ar39Ar upper tuff] 2166 06 Ma [KndashAr tuff 300 m below the upper level])

Because of the tectonic complexity (differential uplift westand east verging thrusting syntectonic basin development andextensive late Cenozoic volcanic cover) stratigraphic relation-ships and correlations in the Chilean Altiplano are difficult toestablish Nonetheless intensive field studies over the past de-


FIGURE 4 Geochronology biochronologic ranges (elsewhere withinSouth America) for representative mammalian taxa (solid vertical bars)and available radioisotopic ages (asterisks) from the Chucal FormationThe radioisotopic ages are only those from directly within the CerroChucal area sequence (Riquelme 1996 Charrier et al 2000 Worneret al 2000 Chavez 2001 Herail et al in review) consisting of twoKndashAr dates (112 6 05 Ma upper Chucal Fm 217 6 08 Ma un-derlying Lupica Formation) and one 40Ar39Ar (1879 6 011 Ma) dateTaxa that do not appear to be informative as to age of the sequence arenot included rodents (chinchillines previously known only from Luja-nian to Recent [08ndash0 Ma] and the tiny rodent incisor is of indeter-minate affinity) glyptodontoid indet (glyptodontoids known from theCasamayoran-Lujanian) and mesotheriine Undescribed Taxon C (of un-certain taxonomic and phylogenetic affinities most similar known taxaoccur in the Friasian sl or Santacrucian Chasicoan and or Huayquer-ian consistent with ranges of more definitively assignable taxa in thisfauna) SALMA chronology from Flynn and Swisher (1995) Positionand naming of Friasian (representing Friasian ss) follows Flynn andSwisher (1995) who questionably inserted it between the Santacrucianand Colloncuran The indicated range for Microtypotherium does notinclude the late Miocene record from Micana Bolivia (MacFadden etal 1990) pending further review of the Bolivian material Preliminarystudy suggests possible reassignment of this specimen to Pseudotypoth-erium based on the following characters M1 in the Micana specimenlacks the small triangular middle lobe diagnostic of Microtypotherium(Villarroel 1974b) and instead possesses an enlarged and rounded mid-dle lobe typical of late Miocene mesotheriines of the genus Pseudoty-potherium (Francis 1965 Villarroel 1974a) and the m2 of the Micanaspecimen does not resemble the short broad m2 characteristic of Mi-crotypotherium (Villarroel 1974a) but rather is more elongate with apronounced anteroexternal extension of the trigonid as seen in speci-mens of Pseudotypotherium

cade including abundant new isotopic age determinations per-mit better substantiated correlation of the Chucal Formationwith the Joracane Zapahuira and lower part of the mammal-bearing Huaylas formations exposed on the west slope of theAltiplano or Precordillera (Garcıa 1996 Garcıa et al 1997see also Munoz and Charrier 1996 Charrier et al 1999 2000)In the Precordillera around Belen the Joracane Formation im-mediately overlies the Lupica Formation and has yielded su-perpositionally consistent KndashAr dates of 182 6 08 Ma and168 6 15 Ma and the Zapahuira Formation (overlying theJoracane Formation) has yielded a superpositionally consistentseries of three KndashAr dates (128 6 02 Ma 127 6 01 Ma and114 6 03 Ma) (Garcıa 1996 Garcıa et al 1997)

Taxa in the Chucal assemblage elsewhere range in age fromthe Santacrucian to Chasicoan Huayquerian or even youngerSALMAs with most overlapping in the Friasian sl (Fig 4)Nesodon arguably is the best indicator of age as it (Nesodongenerally and Nesodon imbricatus in particular) is geographi-cally widespread within southern South America and restrictedto the Santacrucian and Friasian sl SALMAs Mesotheriinesare Friasian sl or younger in distribution Two Chucal me-sotheres appear to be closely allied to Microtypotherium a tax-on known from the Choquecota Formation of Bolivia (consid-ered by Villarroel [1974a b] to be Friasian) and a site nearCerdas Bolivia (which has an associated paleomagnetic stratig-raphy spanning a time range of 165ndash153 Ma MacFadden etal 1995) The third mesothere is of more uncertain affinitiesresembling Typotheriopsis (Chasicoan and possibly Huayquer-ian assemblages) Plesiotypotherium (Huayquerian and Col-loncuran [or possibly Friasian or Santacrucian] of Bolivia) andEutypotherium (Friasian sl) The youngest hegetotheriines arefrom the Huayquerian and the resemblance of the Chucal formto Pseudohegetotherium suggests a Chasicoan age Macrauch-eniid litopterns have a broad temporal range as does Theosodon(Colhuehuapian through Chasicoan) which the Chucal formmost closely resembles providing little chronological utilityAlthough chinchillid rodents extend at least as old as the De-seadan early taxa are lagostomines onlymdashchinchillines havenot been recorded previously in strata older than the Pleisto-cene-aged Lujanian All other taxa in the Chucal Fauna andthe radioisotopic dates bracketing it indicate that this occur-rence must be a substantial range extension for the clade Insum the Chucal Fauna may be as old as Santacrucian (late earlyMiocene) or as young as Chasicoan (late Miocene) The balanceof available biochronologic evidence suggests a correlation tothe Friasian sl making the fauna middle Miocene in age be-tween about 14 and 175 Ma A Friasian sl age for the ChucalFauna is also consistent with the bracketing radioisotopic datesand would be in close agreement with the age estimate for theCerdas Fauna (165ndash153 Ma MacFadden et al 1995) withwhich the Chucal Fauna shares some similarities The datesfrom the top of the Chucal Formation argue against ages asyoung as Chasicoan and also probably the Mayoan (see Flynnand Swisher 1995 Madden et al 1997) Dates from the lowerChucal Formation and the underlying Lupica Formation appearto preclude an age any older than Santacrucian

CONCLUSIONS

Regardless of which SALMA the Chucal Fauna representsthe assemblage documents many new taxa and unique taxonco-occurrences implying various small to large temporal rangeextensions The largest of these is the chinchilline a group pre-viously known only from the Lujanian to Recent revealing agap in the fossil record of some 15 million years As there arefew significant time gaps between known Miocene SALMAs(Flynn and Swisher 1995 Kay et al 1997) and middle Mio-cene faunas are documented from a broad geographic distri-

bution (lowlandhighland Patagonia through Bolivia and Ec-uador to Colombia) it is unlikely that the Chucal assemblagesamples a previously unrecognized temporal interval Insteadthis new middle Miocene fauna broadens the geographic sam-pling of fossils and provides the potential for new insights intopatterns of mammalian evolution during an important temporalinterval (coinciding with significant global climate changes andintracontinental provincial and paleoenvironmental shifts Kayet al 1997 Flynn and Wyss 1998)

Several preliminary indications of diversity and abundanceof taxa within the Chucal Fauna are noteworthy Mesotheresthe most common fossils are more species-rich than in mostother South American middle Cenozoic sites (Miocene assem-


blages from Bolivia being closest to the Chucal Fauna in thisregard) Interatheres are not yet known from this fauna in con-trast to most non-Altiplano Miocene faunas (eg Patagonia andColombia) where they are typically abundant By way of com-parison the rich and well-studied tropical middle Miocene LaVenta Fauna of Colombia lacks mesotheres and the interathereMiocochilius is so abundant that it is the name-bearer for theassemblage zone upon which the Laventan Stage and SALMAwere erected (Madden et al 1997) As Chucal is the northern-most Cenozoic mammalian fauna from Chile it will allow im-proved comparisons of middle Cenozoic faunas across an ex-tensive latitudinal span (more than 308) from west of the An-dean crest The occurrence of this fauna near an important mod-ern biotic disjunction (between the Atacama Desert and lsquolsquothetropicsrsquorsquo) and west of varied Cenozoic faunas from a varietyof paleoelevations in Bolivia will begin to allow assessment ofbiotic history along an eastndashwest transect from eastern Boliviathrough Chile Preliminary observations suggest that Miocenefaunas from the Altiplano (Chile and Bolivia alike) are similarcompositionally but may differ from contemporaneous faunasin the low-latitude tropics (Colombia) and the high-latitudes(Patagonia) An interesting group of modern mammals (chin-chillines) appears to originate within this montane region re-maining unsampled elsewhere until much later These patternsmay be due to marked regional provinciality in the Miocenewhich in turn may be the result of Andean tectonics and as-sociated paleoenvironmental changes

ACKNOWLEDGMENTS

National Geographic Society (Grant 5371-94) provided thesupport for this exploratory project with additional supportfrom US NSF grant DEB-9317943 and FONDECYT ChileNelson Munoz participated in the original expedition yieldingmammal fossils from the Chucal Formation and encouraged usto seek FONDECYT support for continued geologic study ofthe region For their exceptional efforts during fieldwork wethank Gabriel Carrasco Andres Charrier Claude Herail andSergio Villagran Rick Madden Christian de Muizon andGuiomar Vucetich provided taxonomic advice Fossils wereably prepared by Lorie Barber Matt Brown Wendy Taylor andConnie Van Beek and specimen photographs were taken byMark Widhalm

LITERATURE CITED

Bargo M S and M A Reguero 1989 El primer registro de un mam-ıfero fosil en el extremo septentrional de Chile Ameghiniana 26239

Bondesio P J Rabassa R Pascual M G Vucetich and G J ScillatoYane 1980 La Formacion Collon Cura de Pilcaniyeu Viejo y susalrededores (Rıo Negro Republica Argentina) Su antiguedad y lascondiciones ambientales segun su distribucion su litogenesis y susvertebrados Actas del Segundo Congreso Argentino de Paleonto-logıa y Bioestratigrafıa y Primer Congreso Latinoamerica de Pa-leontologıa 385ndash99

Charrier R G Herail J J Flynn R Riquelme M Garcıa D Croftand A R Wyss 1999 Opposite thrust-vergencies in the precor-dillera and western cordillera in northern Chile and structurallylinked Cenozoic paleoenvironmental evolution Fourth ISAG (In-ternational Symposium on Andean Geodynamics) GoettingenGermany155ndash158

mdashmdashmdash mdashmdashmdash mdashmdashmdash mdashmdashmdash mdashmdashmdash and mdashmdashmdash 2000 El cordonChapiquina-Belen en el borde occidental del Altiplano Chilenosignificado paleogeografico y contexto tectonico regional IX Con-greso Geologico Chileno (Puerto Varas Chile) Actas 1763ndash767

mdashmdashmdash N Munoz A R Wyss J J Flynn and G Herail 1994aHallazgo de un humero de toxodonte (Mammalia) en la FormacionChucal (Oligoceno tardıo-Mioceno inferior) en el Altiplano de Ar-ica Chile VII Congreso Geologico Chileno Actas 1430ndash433

mdashmdashmdash mdashmdashmdash and S Palma-Heldt 1994b Edad y contenido paleo-

floristico de la Formacion Chucal y condiciones paleoclimaticaspara el Oligoceno Tardıo-Mioceno Inferior en el Altiplano de AricaChile VII Congreso Geologico Chileno Actas 1434ndash437

Chavez A 2001 Evolucion paleoambiental y sedimentacion sintecton-ica durante el Mioceno en el sector del cerro Chucal (CordilleraOccidental Region de Tarapaca 698 109 Ondash188 459 S) y su relacioncon la estructuracion del Altiplano Thesis Departamento de Geo-logıa Universidad de Chile 73 pp

Cifelli R L 1993 The phylogeny of the native South American un-gulates pp 195ndash216 in F S Szalay M J Novacek and M CMcKenna (eds) Mammal Phylogeny Placentals Springer-VerlagNew York

mdashmdashmdash and J Guerrero 1997 Litopterns pp 44ndash59 in R F Kay RH Madden R L Cifelli and J J Flynn (eds) Vertebrate Pale-ontology in the Neotropics The Miocene Fauna of La Venta Co-lombia Smithsonian Institution Press Washington DC

Croft D A 2000 Archaeohyracidae (Mammalia Notoungulata) fromthe Tinguiririca Fauna central Chile and the evolution and paleo-ecology of South American mammalian herbivores PhD disser-tation The University of Chicago Chicago 311 pp

Douglas J A 1914 Geological section through the Andes of Peru andBolivia I From the coast at Arica in the north of Chile to La Pazand the Bolivian lsquolsquoyungasrsquorsquo Quarterly Journal of the GeologicalSociety of London 2771ndash49

Flynn J J R Charrier G Herall D Croft and A R Wyss 1999The first Cenozoic mammal fauna from the Chilean Altiplano Pro-grama y Resumenes Congreso Internacional Evolucion Neotropı-cal del Cenozolco La Paz Bolivia 19ndash22 May23

mdashmdashmdash and C C Swisher III 1995 Cenozoic South American LandMammal Ages correlation to global geochronologies pp 317ndash333in W A Berggren D V Kent and J Hardenbol (eds) Geochro-nology Time Scales and Global Stratigraphic Correlation SEPMSpecial Publication 54

mdashmdashmdash and A R Wyss 1998 Recent advances in South Americanmammalian paleontology Trends in Ecology and Evolution 13449ndash454

Francis J C 1965 Los generos de la subfamilia Mesotheriinae (Ty-potheria Notoungulata) de la Republica Argentina Boletin del La-boratorio de Paleontologıa de Vertebrados 17ndash31

Garcıa M 1996 Geologıa y estructura del borde del Altiplano occi-dental en el area de Belen (Chile) Memoria de Tıtulo Departa-mento de Geologıa Universidad de Chile Santiago 111 pp

mdashmdashmdash G Herail and R Charrier 1997 Evolucion estratigrafica ytectonica del borde oeste de la cordillera occidental en el area deBelen (Chile) VIII Congreso Geologico Chileno Actas 160ndash64

Herail G R Charrier M Garcıa P Rochat and R Riquelme In re-view Late Cenozoic evolution in the Northern Chilean Andes andimplications for tectonic development of the Altiplano of Chile andwestern Bolivia Tectonics

Kay R F R H Madden R L Cifelli and J J Flynn 1997 VertebratePaleontology in the Neotropics The Miocene Fauna of La VentaColombia Smithsonian Institution Press Washington DC 592pp

MacFadden B J F Anaya H Perez C W Naeser P K Zeitler andK E Campbell Jr 1990 Late Cenozoic paleomagnetism and chro-nology of Andean basins of Bolivia evidence for possible oroclinalbending Journal of Geology 98541ndash555

mdashmdashmdash mdashmdashmdash and C C Swisher III 1995 Neogene paleomagnetismand oroclinal bending in the central Andes of Bolivia Journal ofGeophysical Research 100(B5)8153ndash8167

mdashmdashmdash and R G Wolff 1981 Geological investigations of late Ce-nozoic vertebrate-bearing deposits in southern Bolivia Anais IICongreso Latino-Americano Paleontologıa (Porto Alegre) 2765ndash778

Madden R H 1990 Miocene Toxodontidae (Notoungulata Mamma-lia) from Colombia Ecuador and Chile PhD dissertation DukeUniversity Durham North Carolina 407 pp

mdashmdashmdash J Guerrero R F Kay J J Flynn C C Swisher III and AH Walton 1997 The Laventan Stage and Age pp 499ndash519 in RF Kay R H Madden R H Cifelli and J J Flynn (eds) Verte-brate Paleontology in the Neotropics The Miocene Fauna of LaVenta Colombia Smithsonian Institution Press Washington DC

Marshall L G and T Sempere 1991 The Eocene to Pleistocene ver-tebrates of Bolivia and their stratigraphic context a review pp631ndash652 in R Suarez-Soruco (ed) Fosiles y Facies de Bolivia


Vol I Vertebrados Vol 12(3ndash4) Revista Tecnica de YacimientosPetrolıferos Fiscales Bolivianos Santa Cruz Bolivia

mdashmdashmdash R Hoffstetter and R Pascual 1983 Mammals and stratigra-phy geochronology of the continental mammal-bearing Tertiary ofSouth America Palaeovertebrata Memoire Extraordinaire 19831ndash93

Munoz N and R Charrier 1996 Uplift of the western border of theAltiplano on a west-vergent thrust system Northern Chile Journalof South American Earth Sciences 9171ndash181

Naranjo J A and R Paskoff 1985 Evolucion Cenozoica del piede-monte andino en la pampa del Tamarugal norte de Chile (188ndash218S) IV Congreso Geologico Chileno (Antofagasta) Actas 5149ndash164

Oiso Y 1991 New land mammal locality of middle Miocene (Collon-curan) age from Nazareno southern Bolivia pp 653ndash672 in RSuarez-Soruco (ed) Fosiles y Facies de Bolivia Vol I Vertebra-dos Vol 12(3ndash4) Revista Tecnica de Yacimientos Petrolıferos Fis-cales Bolivianos Santa Cruz Bolivia

Pascual R 1966 Litopterna Paleontolografıa Bonaerense Vol 4 Ver-tebrata A V Borello Buenos Aires pp 161ndash170

mdashmdashmdash and P Bondesio 1985 Mamıferos terrestres del Mioceno me-dio-tardıo de las cuencas de los rıos Colorado y Negro (Argentina)evolucion ambiental Ameghiniana 22133ndash145

Riquelme R 1996 Evolucion tectosedimentaria post-oligocenica delborde occidental del Altiplano entre Tignamar y Salar de Surire IRegion Chile Thesis Departamento de Geologıa Universidad deChile 123 pp

mdashmdashmdash and G Herail 1997 Puesta en evidencia de discordancias pro-gresivas en el Cenozoico Superior del Altiplano de Arica impli-cancias en la interpretacion de la Cordillera Occidental VIII Con-greso Geologico Chileno (Antofagasta) Actas 1231ndash235

Salinas P C Villarroel L Marshall P Sepulveda and N Munoz1991 Typotheriopsis sp (Notoungulata Mesotheriidae) mamıferodel Mioceno Superior en las cercanıas de Belen Arica norte deChile VI Congreso Geologico Chileno (Vina del Mar) Actas 1314ndash317

Schaub S 1935 Saugetierfunde aus Venezuela und Trinidad Abhan-dlungen der Schweizerischen Palaeontologischen Gesellschaft 551ndash21

Scott W B 1912 Mammalia of the Santa Cruz beds Part 2 Toxo-donta pp 111ndash238 in W B Scott (ed) Reports of the PrincetonUniversity Expeditions to Patagonia 1896ndash1899 Vol 6 PrincetonUniversity Princeton New Jersey

Simpson G G 1935 Early and middle Tertiary geology of the Gaimanregion American Museum Novitates 7751ndash29

Soria M 1981 Los Litopterna del Colhuehuapense (Oligoceno tardıo)de la Argentina Revista del Museo Argentino de Ciencias Natur-ales lsquolsquoBernardino Rivadaviarsquorsquo Paleontologıa 31ndash54

Villarroel C 1974a Les Mesotherines (Notoungulata Mammalia) duPliocene de Bolivie Leurs rapports avec ceux drsquoArgentine Annalesde Paleontologie 60245ndash281

mdashmdashmdash 1974b Un Mesotheriine nouveau (Notoungulata Mammalia)dans le Miocene superieur de Bolivie Academie des Sciences (Par-is) Comptes Rendus Serie D 279551ndash554

mdashmdashmdash 1978 Edades y correlaciones de algunas unidades litoestrati-graficas del altiplano Boliviano y estudio de algunos representantesmesotheriinos Revista de la Academia Nacional de Ciencias Bo-livia 1159ndash170

Vucetich M G 1989 Rodents (Mammalia) of the Lacayani fauna re-visited (Deseadan Bolivia) Comparison with new Chinchillidaeand Cephalomyidae from Argentina Bulletin du Museum NationalDrsquoHistoire Naturelle (Paris) Serie 4 Section C 11233ndash247

mdashmdashmdash 1991 Los roedores de Salla y Lacayani (Bolivia) y su corre-lacion con los de otras faunas de edad Deseadense (Oligoceno)pp 625ndash629 in R Suarez-Soruco (ed) Fosiles y Facies de BoliviaVol I Vertebrados Vol 12(3ndash4) Revista Tecnica de YacimientosPetrolıferos Fiscales Bolivianos Santa Cruz Bolivia

Walton A H 1997 Rodents pp 392ndash409 in R F Kay R H MaddenR L Cifelli and J J Flynn (eds) Vertebrate Paleontology in theNeotropics The Miocene Fauna of La Venta Colombia Smithson-ian Institution Press Washington DC

Worner G K Hammerschmidt F Henjes-Kunst J Lezaun and HWilke 2000 Geochronology (40Ar39Ar KndashAr and He-exposuresages) of Cenozoic magmatic rocks from Northern Chile (188ndash228S)implications for magmatism and tectonic evolution of the centralAndes Revista Geologica de Chile 27205ndash240

Received 20 February 2001 accepted 8 July 2001

200

Journal of Vertebrate Paleontology 22(1)200ndash206 March 2002q 2002 by the Society of Vertebrate Paleontology

RAPID COMMUNICATION

THE FIRST CENOZOIC MAMMAL FAUNA FROM THE CHILEAN ALTIPLANO

JOHN J FLYNN1 DARIN A CROFT1 REYNALDO CHARRIER2 GERARD HERAIL3 and ANDRE R WYSS4

1Department of Geology The Field Museum Chicago Illinois 60605 jflynnfieldmuseumorg2Departamento de Geologıa Universidad de Chile Santiago Chile

3IRD 209-213 Rue La Fayette 75010 Paris France4Department of Geological Sciences University of California Santa Barbara California 93106

Despite its richness South Americarsquos Cenozoic mammal re-cord is strongly biased geographically towards a small portionof the continent mainly Patagonia The rapidly growing list ofmajor Cenozoic localities at lower latitudes thus marks a sig-nificant advance in our understanding of mammalian evolutionin South America (see summaries in Flynn and Swisher 1995Flynn and Wyss 1998)

This paper reports the discovery of the first Cenozoic mam-mal fauna known from the Chilean Altiplano It is part of anongoing collaborative effort to sample faunas of a variety ofages across a large latitudinal transect of western South Amer-ica the goal of which is to elucidate temporal patterns of pro-vincialism within the continent as well as the tectonic and up-lift history of the Andes Mountains and associated paleoenvi-ronmental changes An isolated well-preserved fossil mammalhumerus was discovered in 1992 in northern Chile by RC GHand Nelson Munoz and referred to the toxodontid notoungulateNesodon (Charrier et al 1994a) Our team returned to the areain 1998 to collect and assess its potential for more extensivepaleontological investigations (Flynn et al 1999)

Only two Cenozoic mammal specimens were known fromnorthern Chile prior to the discovery of the Chucal Fauna bothfrom the Huaylas Formation (late Miocene) The first a no-toungulate right lower jaw fragment (MLP 86-VIII-10-1) col-lected by D Pacci in 1969 in the area of Caragua (at the con-fluence of the quebradas of Lupica and Belen approximately188 259 S 698 359 E) was identified as a mesotheriine withaffinities to Eutypotherium (Bargo and Reguero 1989) Thesecond specimen a skull of the mesothere Typotheriopsis spwas probably recovered from the same locality (Salinas et al1991) The Huaylas Formation and its mesotheres are almostcertainly younger than the fossiliferous horizons described inthis paper based on dates bracketing that formation and strati-graphic superposition (Naranjo and Paskoff 1985 Munoz andCharrier 1996 Garcıa et al 1997)

Approximately contemporaneous or slightly younger faunasfrom Bolivia include Quebrada Honda (MacFadden and Wolff1981 MacFadden et al 1990) Nazareno (Oiso 1991) Cerdas(Villarroel 1978 MacFadden et al 1995) and small collec-tions from the Choqueta and Quehua formations (Marshall andSempere 1991) South American Land Mammal lsquolsquoAgersquorsquo (SAL-MA) chronology follows Flynn and Swisher (1995) The Fria-sian SALMA is controversial (Flynn and Swisher 1995 Mad-den et al 1997) we make a distinction between usage of Fria-sian in its traditional sense (Friasian sensu lato) of subsumingthe Mayoan Colloncuran and Friasian sensu stricto SALMAsand the termrsquos more restrictive definition (Friasian sensu stricto)whereby it is applied to the temporal interval characterized by

the type assemblage in southern Chile and correlative faunas(if indeed this biochron is valid)

Abbreviations FMNH Field Museum of Natural HistoryChicago MACN Museo Argentino de Ciencias NaturaleslsquolsquoBernardino Rivadaviarsquorsquo Buenos Aires MLP Museo de LaPlata La Plata SALMA South American Land MammallsquolsquoAgersquorsquo sl sensu lato ss sensu stricto Deciduous teeth areindicated with a lsquolsquodDrsquorsquo preceding the tooth position All spec-imens will receive National Museum of Natural History (San-tiago) collection numbers at the completion of this projectmdashfield numbers are reported below in the format CHILE-ALTI-PLANO-DATE-FIELD NUMBER (eg C-ALT-7-21-98-43)

GEOGRAPHIC AND GEOLOGIC SETTING

The study site is located northwest of Salar de Surire (188439 S 698 109 W) in outcrops of the syntectonic fluvio-lacus-trine Chucal Formation exposed on both limbs of a major NndashSoriented growth anticline (Fig 1) The Chucal Formation un-conformably overlies the early Miocene Lupica Formation andis overlain conformably by the Lauca Formation (Riquelme1996 Riquelme and Herail 1997) Consisting of two membersit is composed of approximately 450 m (west limb 100ndash200m on the east limb) of sandstone conglomerate and mudstonewith numerous pyroclastic intervals (Charrier et al 1994aChavez 2001) The formation varies considerably in thicknessfrom west to east because of different paleodepositional envi-ronments within the basin (more dominated by lacustrine facieson the west and coarse fluviatile sediments on the east) anddevelopment of progressive syndepositional unconformitiesthinning the sequence on the east side (the most significantunconformity being D3 [of Charrier et al 2000 and Herail etal in review] in the upper part of the sequence)

The lower third of the formation including the lower datedwhite tuff (see below) is characterized by a fining-upwards se-quence The reverse is true in the upper third of the formationwith the uppermost layers consisting of fluvial conglomeratesA dated upper white ash layer (see below) occurs just abovethese conglomerates The middle third of the formation consistsof open lake deposits containing ostracodsmdashthis unit is espe-cially well developed on the western limb of the anticline Leafimpressions and pollen have been recovered from several ho-rizons in the lower to middle parts of the formation (Charrieret al 1994b)

Mammalian fossils have been recovered from several dozenlocalities in both members of the Chucal Formation spanningmuch of the thickness of the formation The vast bulk of thelocalities and specimens lie within the middle of the sequence(below unconformity D2D29) Lacking evidence that the sam-pled horizons are faunally distinct and given the stratigraphic














XenarthraCingulata






Notoungulates














Litoptern


Rodents



Glyptodont


AGE AND CORRELATION








CONCLUSIONS






ACKNOWLEDGMENTS


LITERATURE CITED































































XenarthraCingulata






Notoungulates














Litoptern


Rodents



Glyptodont


AGE AND CORRELATION








CONCLUSIONS






ACKNOWLEDGMENTS


LITERATURE CITED





























































Litoptern


Rodents



Glyptodont


AGE AND CORRELATION








CONCLUSIONS






ACKNOWLEDGMENTS


LITERATURE CITED






















































Litoptern


Rodents



Glyptodont


AGE AND CORRELATION








CONCLUSIONS






ACKNOWLEDGMENTS


LITERATURE CITED






















































CONCLUSIONS






ACKNOWLEDGMENTS


LITERATURE CITED




















































ACKNOWLEDGMENTS


LITERATURE CITED









































































Documents

The first Cenozoic mammal fauna from the Chilean Altiplano