AMERICAN MUSEUM Novttates PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, N.Y. 10024 Number 3098, 31 pp., 4 figures, 3 tables May 20, 1994

Paleogene Mammals from the Andes of Central Chile: A Preliminary Taxonomic, Biostratigraphic, and Geochronologic Assessment

A. R. WYSS,1 J. J. FLYNN,2 M. A. NORELL,3 C. C. SWISHER III,4 M. J. NOVACEK,5 M. C. MCKENNA,5 AND R. CHARRIER6

ABSTRACT Two highly unexpected and diverse fossil mam- appearances ofat least seven subfamilial or higher- mal assemblages have been discovered in the up- level taxa. This co-occurrence of formerly tem- per Rio Tinguiririca valley in the Andes Main porally disjunct taxa identifies the fauna as rep- Range of central Chile. This work brings to light resenting a new interval of South American land the first Paleogene mammal faunas from Chile, as mammal evolution. This fauna (here termed the well as the first fossil mammals from the central Tinguiririca Fauna) represents the youngest di- Andean Main Range. The younger fauna presently versely sampled pre-Deseadan fauna from South includes representatives of at least three higher- America, and records the earliest occurrence of level groups ofmarsupials, five notoungulate fam- rodents on the continent. Radioisotopic dates from ilies, two groups of edentates, a rodent, plus a volcanic units containing and associated with the probable litoptern, and represents the first well- Tinguiririca Fauna are the first available for the known transitional Eocene-Oligocene fauna from Eocene through early Oligocene South American South America. It documents the first or last mammal record, and thus represent a critical cal-

' Assistant Professor, Department of Geological Sciences, University of California, Santa Barbara, CA 93106.. 2 Curator, Department ofGeology, Field Museum ofNatural History, Roosevelt Rd. @ Lake Shore Drive, Chicago, IL 60605. 3Assistant Curator, Department of Vertebrate Paleontology, American Museum of Natural History. 4Geochronology Center, Institute of Human Origins, 2453 Ridge Rd., Berkeley, California 94709. 5 Curator, Department of Vertebrate Paleontology, American Museum of Natural History. 6 Professor, Departamento de Geologia, Universidad de Chile, Casilla 13518 Correo 21, Santiago, Chile.

Copyright K) American Museum of Natural History 1994 ISSN 0003-0082 / Price $4.70 2 AMERICAN MUSEUM NOVITATES NO. 3098 ibration point for mammalian biogeochronology. tory. Likewise they shed light on crucial and here- The second fauna (here termed the Tapado Fauna) tofore poorly understood phases of South Amer- is presently less completely known than the first, ican mammal evolution, and establish an im- but is clearly significantly older. Both faunas are portant new source ofgeochronologic information of demonstrated importance to the interpretation for this Andean region. of central Andean stratigraphy and tectonic his-

INTRODUCTION Prior to its Late Pliocene connection with migrant taxa stems from the length of the North America, South America was isolated faunal hiatus preceding the Deseadan and lack from other continents for a span of some 60 of radioisotopic control for Mustersan and million years. This long period of insularity Casamayoran sediments. and the peculiar biota it engendered have We have recovered two new fossil mam- captured the attention of evolutionary biol- mal faunas of transitional Eo-Oligocene and ogists and paleontologists for more than a probable early Eocene age from volcaniclas- century (Simpson, 1984). The best known, tic sediments assigned to the Abanico (= and perhaps most unusual, element of South Coya-Machali) Formation near the axis of America's endemic biotic history is its Ce- the Andean Main Range in the valley of the nozoic mammals, the succession of which is Tinguiririca River in central Chile (fig. 1). generally divided into a sequence of 13 dis- The first discovered (Novacek et al., 1989) tinct South American Land Mammal Ages and younger ofthese faunas is from exposures (SALMAs). Some of these (particularly Pa- near the town of Termas del Flaco (34°59'S, leogene) faunas remain very incompletely 70'26'W). This fauna, hereafter referred to as known, however, and decades of intensive the Tinguiririca Fauna, represents South investigation have failed to close several im- America's first diversely sampled pre-Desea- portant gaps. Among these, an approximately dan, post-Mustersan mammal assemblage. 15 million year interval between post-Mus- In addition to illuminating a crucial phase of tersan (?middle Eocene) and pre-Deseadan mammalian evolution, this fauna represents (late Oligocene-?early Miocene) horizons has the first chronologically significant paleon- previously represented the most poorly tological find for a major group of central known span ofthe South American Cenozoic Andean rock units, and is of broad signifi- mammal record (Marshall, 1985). Apart from cance for the interpretation of regional geo- its length (encompassing up to a third of Ce- logic history. Radioisotopic dates associated nozoic time), additional factors compound with the Tinguiririca Fauna are key calibra- the difficulties posed by this faunal hiatus. tion points for early Cenozoic South Amer- First, the faunas generally accepted as brack- ican biochronology, they aid in constraining eting this hiatus, the ?middle Eocene Mus- the timing of the immigration of rodents to tersan and ?Eo-Oligocene Divisaderan SAL- South America, and they help to date an im- MAs, (the latter sometimes being considered portant middle Cenozoic faunal turnover early Deseadan in age) are the two most poor- event. The bulk of the present contribution ly known of the entire South American Ce- represents a preliminary description of the nozoic mammal record. Second, this span co- Tinguiririca Fauna. incides with a crucial faunal transition, from A second fauna, here designated the Ta- mammal communities dominated by archaic pado Fauna (after Quebrada El Tapado which lineages to communities characterized by is near the principal locality), has been re- mammals of a markedly more "modern" covered from exposures approximately 12 km stamp (Pascual et al., 1985). And third, this NW of Termas del Flaco (Flynn et al., 1991; post-Mustersan pre-Deseadan hiatus encom- Wyss et al., 1992a, 1992b). As material from passes the inadequately dated first appear- this area is in preliminary preparation stages, ance ofprimates and rodents in South Amer- we make only cursory reference to the Ta- ica, two lineages ofmajor importance in later pado Fauna in this report. To clear up pos- Cenozoic and Recent faunas. Uncertainty sible confusion stemming from our expressed over the timing of arrival of these two im- earlier views (ibid.), it is necessary to mention 1 994 WYSS ET AL.: PALEOGENE MAMMALS FROM CENTRAL CHILE 3 that the Tapado Fauna is assuredly not youn- new mammal faunas) (Domeyko, 1862, ger than the Tinguiririca Fauna. Accepted Burckhardt, 1897, 1900; Philippi, 1899; stratigraphic interpretations of the region, Gerth, 1931; Groeber, 1947a, 1947b). These which place sediments producing the former led ultimately to the abandonment of Dar- fauna some 2000 m higher in the local strati- win's Porfiritica designation in favor of graphic section than those producing the lat- Klohn's (1957, 1960) finer stratigraphic sub- ter, had led us to expect a younger Tapado. divisions, which are still employed (table 1). Rather, the few specimens that have been Important, more recent, refinements of this prepared to date suggest that the Tapado Fau- sequence include: Arcos (1987); Charrier na is subtantially older than the Tinguiririca (1973,198 1b); Davidson and Vicente (1973); Fauna; subject to revision by ongoing prep- Gonzalez and Vergara (1962); and Charrier aration, preliminary comparisons indicate a et al. (submitted). Casamayoran age. This establishes that the The Porfiritica sequence is exposed over a much older Tapado Fauna has been tecton- 400 km north-south long, 50 km east-west ically superposed over the Tinguiririca Fauna wide, swath along this segment ofthe Andean via post-Oligo-Miocene thrust faulting, dem- Main Range and measures roughly 10,000 onstrating much greater tectonic complexity meters in stratigraphic thickness. Its lower than had been previously appreciated for this half (the Nacientes del Teno, Rio Damas, region of the Andes. Bafios del Flaco, and Colimapu Formations) In sum, the new faunas and associated geo- (table 1) consists of interbedded, sedimen- chronometric data are of demonstrated im- tary, marine and terrestrial formations re- portance in elucidating the tectonic history cording a series of transgressive and regres- of the rock units hosting them, the ages and sive phases of detrital back arc deposition. history of several related formations in the Marine levels contain abundant invertebrate region, and the ages of several related South fossils, firmly establishing these lower de- American faunas and faunal events. posits to be medial Jurassic through Late Cre- taceous in age (Klohn, 1960; Gonz'alez and ABBREVIATIONS Vergara, 1962; Charrier, 1981a, 1981b). Such clarity does not extend, unfortunate- AMNH American Museum ofNatural History BRCU Brownish Red Clastic Unit ly, to age determinations for the upper units LBLC Lomas Blancas (or La Curandera) of the Porfiritica assemblage (approximately MLP Museo de La Plata 5 km thick), ofwhich the Abanico Formation PU Princeton University forms an important component. These for- SGOPV Museo Nacional de Historia Natural, mations (none ofwhich had yielded chrono- Santiago, vertebrate paleontology col- logically useful fossils prior to our work) con- lections sist of continental, mainly volcanic, and volcaniclastic arc deposits. Stemming partly from this lack of paleontologic control, there GEOLOGICAL OVERVIEW AND has been considerable uncertainty about the PREVIOUS INVESTIGATIONS age of most of these upper units, including The work of Charles Darwin provides the the Abanico [= Coya-Machali (Klohn, 1960)] first systematic geological and paleontologi- Formation. Adding to these difficulties, per- cal accounts ofthe Andean Cordillera of cen- vasive low-temperature recrystallization has tral Chile and neighboring Argentina. Darwin hampered the use of conventional "whole characterized and formally named the rock rock" 40K/40Ar radioisotopic dating tech- unit forming the bulk of the central Andean niques for these units (Charrier, 1981a; Ver- Main Range in the technical account (1846) gara et al., 1988). The Abanico Formation, of his traverse of the Cordillera approxi- traditionally assigned a late Cretaceous age mately 100 km north of the Tinguiririca (Klohn, 1960), has yielded a highly variable drainage (Darwin, 1845), terming it the Por- range of 40K/40Ar age estimates, some as old firitica Formation. Over the next century there as early Paleocene but most being Miocene- followed a series of more detailed works in late Oligocene (Charrier and Munizaga, 1979; the region, some touching on the valley of Drake et al., 1982; Vergara, 1978; Vergara the Rio Tinguiririca specifically (site of our and Drake, 1978, 1979). Because of alter- 4 AMERICAN MUSEUM NOVITATES NO. 3098

TABLE 1 Stratigraphy of Andes Main Range, Central Chile [(after Klohn, 1960; Gonzalez and Vergara, 1962; Charrier, 1973, 1981a, 1981b; Charrier et al., submitted), showing currently accepted subdivision of Darwin's Porfinrtica Formation. Ages of post- Neocomian units are relatively uncertain, being based for the most part on suspect 40K/40Ar determi- nations (see text).] Unit/formation Lithology Thickness Age Young Andean volcanics Andesitic & dacitic lavas & Stratovolcanoes & Late Pliocene-Recent pyroclastics isolated flows, variable thick- ness UNCONFORMITY Farellones Continental, dacitic pyro- 2000-3000 m Miocene (25-7 Ma) clastics UNCONFORMITY Abanico (=Coya-Machali) Continental volcanic, pyro- 1000-2000 m ?Paleogene-early clastic & detrital deposits Neogene (62.3- 16.4 Ma) UNCONFORMITY Colimapu Continental sandstones & 2000-3000 m Late Early Creta- volcanic deposits ceous Banios del Flaco (=Lo Valdes) Marine fossiliferous lime- 2000 m Tithonian-Neocomi- stones an Leiias-Espinoza Pyroclastic turbidites > 1200 m Kimmeridgian Rio Damas Continental sandstones, 3000-4000 m Kimmeridgian conglomerates and lavas Nacientes del Teno Marine sandstones and 800-1000 m Bajocian-early Kim- limestones and 100-200 meridgian m thick gypsum upper member UNCONFORMITY Paleozoic Andean Basement ation, these dates are generally discounted as nosaur remains from the Vifiita Formation, anomalously young (Charrier, 1981a; Ver- approximately 200 km further north (Casa- gara et al., 1988). Discovery of fossil mam- miquela et al., 1969). The ichnofossils and mals and single-crystal laser fusion analyses the accessibility afforded by the road serving suggesting Paleogene ages for portions of the the summer resort town ofTermas del Flaco Abanico Formation (Charrier et al., submit- prompted our initial exploration in the Tin- ted), dictate, therefore, considerable age re- guiririca region. vision of upper Porfiritica units. JJF, MAN, MJN, and ARW spent one day Prior to the present series ofinvestigations, in February 1988 prospecting in exposures reports of fossil vertebrates within the Por- immediately surrounding Termas del Flaco. firitica units had been limited to dinosaur As all pre-Quaternary rocks in the vicinity footprints from the upper part of the Bafios had been consistently mapped as Mesozoic, del Flaco Formation at its type locality near the discovery offragmentary yet indisputably Termas del Flaco (Casamiquela and Fasola, Cenozoic mammals was completely unfore- 1968), ichthyosaur remains from the same seen. A field party from the AMNH (New area and undoubtedly from the same for- York), Field Museum of Natural History mation (Philippi, 1895), and fragmentary di- (Chicago), Universidad de Chile Santiago, 1 994 WYSS ET AL.: PALEOGENE MAMMALS FROM CENTRAL CHILE 5

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Museo Nacional de Historia Natural Santi- Tinguiririca-Fauna-producing localities are ago, and the University of California Santa concentrated in three main areas, all in the Barbara, returned to the site in January-Feb- vicinity of Termas del Flaco, and all repre- ruary 1989, at which point the paleontolog- senting apparently the same restricted strati- ical importance and geological implications graphic unit. The most important set of lo- of the discovery became apparent. calities occurs south of the Rio Tinguiririca in steep badlandlike exposures near an un- GEOGRAPHIC SETTING named pass [identified simply by its elevation The main part of the horizon producing 2738 m on the topographic sheet (Anony- the Tinguiririca Fauna occurs high within the mous, 1985); known locally as the "Porte- northwest-southeast trending valley ofthe Rio zuelo El Fierro" and will be referred to as the Tinguiririca near the town ofTermas del Fla- El Fierro localities] located 3 km nearly due co, Chile (figs. 2a, b, 3). The area of exposure south oftown (fig. 4). Fossiliferous exposures is in rugged mountainous terrain, slightly off- extend from approximately 1 km north of axis of the Main Andean Cordillera, approx- this pass, through the pass itself, and 1 km imately 7 km west of the Argentine border. south into the upper drainage ofthe Rio Teno. The north-south extent of the fossiliferous A second, much less extensive set of expo- unit is presently uncertain. Exposures of the sures occurs approximately 1 km west of the mammal-bearing unit may be rather exten- Fierro Pass on the steep eastern slope ofCerro sive south of the Rio Teno (the next major Alto del Padre. These localities are referred drainage to the south), but road closures have to as the Cerro Alto del Padre localities. The hampered access to that region. Exposures third set of Tinguiririca Fauna-producing lo- are likely equally widely distributed to the calities is north ofthe Rio Tinguiririca, some north as well, but again access is difficult. 4 km northwest of Termas del Flaco. Al- 6 AMERICAN MUSEUM NOVITATES NO. 3098

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though none of these three sets of localities Colimapu units (Farellones, Plan de los are laterally continuous directly, lithostrati- Yeuques, and Corona del Fraile Formations) graphic and biostratigraphic evidence sug- that have been mapped in the central Andes gests that they probably represent the same (Gonzalez and Vergara, 1962; Klohn, 1960). restricted stratigraphic unit. We have dis- Thus we cannot entirely exclude the possi- cerned no significant differences in fossil con- bility that the fossiliferous strata correlate with tent between the locality sets and therefore one ofthese latter units or that they represent presume them to be approximately contem- a new, unnamed unit. Even if future work poraneous. Similarly, we have observed no were to show the fossiliferous unit to pertain changes in faunal composition with differ- to something other than the Abanico For- ences in stratigraphic position within the mation, however, the fossiliferous sediments <100 m thick Tinguiririca-Fauna-producing unquestionably occur within the upper (post- horizon. Neocomian) half of the Porfiritica sequence. Irrespective of their formational allocation, mammals from the Termas del Flaco region STRATIGRAPHIC CONTEXT represent the first chronologically informa- tive fossils from a stratigraphically important The Tinguiririca Fauna occurs in 35-50° and geographically widespread set of rock westward dipping volcaniclastic sediments, units in this region of the Andes. ranging in color from brownish-red to violet, The contact ofthe Tinguiririca-Fauna-pro- to greenish-gray and buff, interbedded with ducing unit with underlying formations is flows and tuffs. The fossiliferous strata are most clearly observed for the series of local- assigned to the Abanico Formation (Charrier ities straddling the El Fierro Pass (see above). et al., submitted), a unit broadly distributed In the northern part of this area, the fossil- in this region ofthe Andes. Although the fos- bearing unit is approximately 50 m thick and sil localities occur in deposits identified as rests in slight angular unconformable contact the medial to Late Cretaceous age Colimapu on the underlying BRCU. The BRCU thins Formation on earlier large-scale maps ofthis to the south, disappearing altogether near the region (Klohn 1960; Gonzalez and Vergara, pass. South ofthe pass, the Cenozoic deposits 1962; Vergara, 1965; Charrier, 1973; Arcos, rest in disconformable contact on the Juras- 1987), new results from detailed mapping and sic, marine Ba-nos del Flaco Formation. The sedimentology show this identification to be latter formation appears to bend subtlely in error (Charrier et al., submitted). The Coli- along strike; north of the pass the Cenozoic mapu Formation, in fact, appears to be en- deposits and the Bainos del Flaco Formation tirely absent in the Termas del Flaco region; diverge by some 400 in strike, but south of a small wedge of Cretaceous, coarse, red, de- the pass they are indistinguishable in this re- trital sediments-informally termed the gard. Brownish Red Clastic Unit [BRCU] (Char- Two basaltic flow units in the region are rier et al., submitted) probably represents a relevant to the present discussion. An eastern new formation. In contrast to the fossiliferous flow unit occurs conformably beneath the El Paleogene unit, the BRCU is nonvolcani- Fierro Pass set of localities, and above the clastic, coarser grained, much redder in color, BRCU and the Ba-nos del Flaco Formation. more steeply dipping, and lacks extrusives. This flow is somewhat heterogeneous in com- The abrupt nature ofthe contact between the position, up to approximately 40 m thick, BRCU and underlying Baiios del Flaco For- shows a baked lower contact, and its upper mation, as well as several sedimentological surface bears a puddingstone conglomerate. features argue against referral of the BRCU To the west, at the set of localities on the to the Colimapu Formation (Charrier et al., eastern slope ofCerro Alto del Padre, at least submitted). one flow is intercalated within the fossil-bear- In connection with our referral ofthe Tin- ing unit. guiririca-Fauna-producing horizon to the Fossils occur in brownish-red to violet vol- Abanico Formation, it should be mentioned caniclastic sediments that may be the product that the lithology of this horizon also resem- of a lahar; internally, the relatively fine- bles that reported for portions of other post- grained fossiliferous horizon is uniform in 1 994 WYSS ET AL.: PALEOGENE MAMMALS FROM CENTRAL CHILE 9

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Fig. 3. Geology of the study region (after Charrier et al., submitted): 1, Rio Damas Formation; 2, Bafios del Flaco Formation; 3, 104 Ma White Tuff Unit; 4, brownish-red Clastic Unit; 5, volcaniclastic part of the Abanico Formation; 6, lower basalt flow of the volcaniclastic part of the Abanico; 7, sedi- mentary and volcanic upper part ofthe Abanico Formation; 8, fluidal felsic intrusives; 9, Andesitic dike; 10, Alto del Padre Volcanic Unit; 11, El Fierro Fault; 12, inferred contact; 13, strike and dip. 10 AMERICAN MUSEUM NOVITATES NO. 3098

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1> L~~ .1994 WYSS ET AL.: PALEOGENE MAMMALS FROM CENTRAL CHILE 11 lithology and is structureless. Roughly spher- TABLE 2 ical nodules, ranging between approximately Taxonomic List for the Tinguiririca Fauna 5 and 40 cm in diameter, are a characteristic (Identifications are based on direct comparison weathering feature ofthis horizon. In general, with relevant collections in North and South we have found these nodules to be more high- American museums.) ly fossiliferous and to yield better quality Marsupialia specimens than surrounding non-nodular but ?Groeberiidae lithologically identical sediments. These new genus and species nodules are broken with hand sledges in the ?Argyrolagidae field and most specimens are first observed new genus and species in cross section. Fragmented nodules are Polydolopidae reassembled in the laboratory and are then Polydolops, new species prepared mechanically. Didelphimorphia incertae sedis Fossils are invariably found isolated, gen- new genus and species erally consisting offragmentary dentitions or Eutheria partial skulls, isolated teeth or postcranial re- Edentata mains, less frequently articulated limbs, and, ?Dasypodidae incertae sedis in a few instances, complete skeletons. Fossils Phyllophaga appear rather evenly dispersed throughout the Pseudoglyptodon, new species fossiliferous horizon; although we have taken Litopterna Indaleciinae to harvesting nodules, we have found no sin- new genus and species gle locality with concentrations ofbone war- Rodentia ranting quarrying. ?Dasyproctidae new genus and species ANALYSIS Notoungulata TAXONOMIC Notostylopidae Preparation has been sufficient to reveal new genus and species wide taxic diversity, including representa- Interatheriidae tives of five mammalian ordinal or superor- "Notopithecinae" dinal groups (table 2). The most abundant new genus and species a Interatheriinae element of the fauna is suite of notoungu- new genus and species A lates, numbering approximately 15 taxa. new genus and species B Marsupials, edentates, a rodent, and a prob- Archaeohyracidae able litoptem are also represented. Nonmam- Pseudhyrax cf. eutracytheroides malian tetrapods are not presently known cf. "Bryanpattersonia sulcidens" from the fauna. new taxon A Of the nearly 400 specimens collected in new taxon B the Termas del Flaco region to date, an un- new taxon C usually large fraction consists ofjaws, skulls, new taxon D and partial skeletons. Induration of the en- Homalodotheriidae matrix makes Trigonolophodon cf. elegans casing volcaniclastic prepara- Notohippidae tion of these specimens difficult and time "Rhynchippinae" intensive; consequently nearly halfofour col- Eomorphippus, new species lection currently remains unavailable for de- "Eomorphippus" cf. pascuali tailed study. Offsetting this disadvantage is new taxon A the preservation and completeness ofthe ma- new taxon B terial, which is often excellent. Specimens of Isotemnidae incertae sedis exceptional quality include crania and partial skeletons oftwo families ofedentates, crania level marsupial groups (Didelphimorphia inc. and partial skeletons of members of at least sed., Polydolopidae, ?Argyrolagidae, and three notoungulate families (Archaeohyraci- ?Groeberiidae). dae, Notostylopidae, and Interatheriidae), and The faunal description provided below is nearly complete jaws ofat least three higher- necessarily incomplete and provisional, with 12 AMERICAN MUSEUM NOVITATES NO. 3098 a more comprehensive analysis awaiting matches in size, and is of the correct general preparation of a greater percentage of avail- morphology, to suggest association with the able material. Nevertheless, the fauna is suf- mandibles just described. The preserved por- ficiently important to warrant a brief discus- tions of its incisors (basically the labial faces sion of its major components, updating and of an enlarged anterior tooth, followed by a elaborating upon a preliminary faunal list smaller tooth of essentially similar form) are published previously (Wyss et al., 1990). reminiscent of G. minoprioi. The occlusal In the following discussion taxa are iden- pattern and shape of the molars of this spec- tified to the degree of specificity allowed by imen, however, are unlike those of any mar- existing nomenclature. Although the major- supial known to us. In sharp distinction to ity can be diagnosed as new with specimens triangular-shaped upper molars of G. mino- presently in hand, because ongoing prepa- prioi, those of the Tinguiririca form are rect- ration will improve representation of many angular in outline, the long axis aligned par- of them, we postpone their formal recogni- allel to the tooth row. This unusual upper tion. Our use of traditional family endings dentition either: 1) belongs to the taxon rep- for many of the higher-level taxa discussed resented by the groeberiid lowers and is sim- is only for convenience, and is not intended ply highly autapomorphic; 2) represents up- to imply equivalence of cladistic rank. pers ofthe argyrolagid recognized tentatively below; or 3) represents neither an argyrolagid nor a groeberiid, but a patagoniid (Pascual MARSUPIALIA and Carlini, 1987), or a new gliriform mar- ?Groeberiidae, new genus and species. A supial. highly distinctive new taxon represented by ?Argyrolagidae, new genus and species. several partial mandibles (e.g., SGOPV 2993, Argyrolagids represent another poorly known 2997), this find probably marks only the sec- endemic clade of South American marsupi- ond occurrence of this enigmatic group of als, the earliest previously known occurrence marsupials. The type and previously only of which is incomplete mandibular material known taxon Groeberia minoprioi (Patterson, from the Deseadan of Bolivia (Wolff, 1984). 1952), now represented by excellent cranial We provisionally refer one laterally crushed remains (Goin, 1988-89; Pascual et al., in mandible (SGOPV 2860) from the Tingui- press), is restricted to the Divisadero Largo ririca Fauna to the family. Although its pres- Formation of west-central Argentina. Al- ent state of preparation and poor preserva- though the two forms show numerous mor- tion do not permit us to rule out its reference phological differences, among adequately to the new groeberiid discussed above, there known South American marsupials the Tin- appear to be subtle differences. If an argy- guiririca form appears to show closest affin- rolagid identification is substantiated by ad- ities to G. minoprioi. Synapomorphic resem- ditional preparation and/or enamel micro- blances include the medial (relative to the structural analysis, this would represent the cheek tooth row) position ofthe posterior end oldest known occurrence for the group. Also, of the greatly enlarged lower incisor, plus a as discussed with reference to the probable distinctive bilobate molar crown pattern with groeberiid above, an upper dentition (SGOPV well-developed lingual and buccal flexids and 2952) possibly pertains to this family. similar paraconid development, and it is on Polydolopidae: Polydolops, new species. A this basis that we provisionally refer the Chil- new species of Polydolops is represented by ean form to the Groeberiidae. In contrast to a mandible (SGOPV 2941) preserving a com- G. minoprioi, the Tinguiririca groeberiid has plete dentition (see Wyss et al., 1990: fig. 4a). a relatively shallow mandibular ramus, only An enlarged procumbent ?canine and a "pla- three lower molars, and a distinctive peglike giaulacoid" blade immediately identify this last premolar. specimen as a polydolopid. The lack of in- One upper dentition (SGOPV 2952) con- cisors, a strong labial rib on p3, and retention sisting of three molars and a pair of incom- of pl permit assignment of this new species pletely preserved, high crowned, posteriorly to Polydolops, indicating closest affinities to curved incisors is perplexing. This dentition P. mayoi and P. thomasi. Of these two spe- 1994 WYSS ET AL.: PALEOGENE MAMMALS FROM CENTRAL CHILE 13 cies, the Tinguiririca form appears to be most metaconids closely spaced; cingulae are es- similar to, but is differentiable from, the for- sentially absent. Exclusive ofborhyaenids and mer (Flynn and Wyss, 1990). polydolopids, the Eocene through early Mio- Recognizing that its fragmentary nature cene record ofSouth American marsupials is precluded definitive assignment, Patterson virtually nonexistent, thereby precluding ex- and Marshall (1978) tentatively identified a tensive comparison of this specimen with large, edentulous, anterior mandibular frag- roughly contemporaneous taxa. The speci- ment (PU 21998) from the Deseadan of Bo- men exhibits a mixture of features (some of livia as a polydolopid, the only then recorded which cannot be determined with certainty post-Mustersan record for the family. Mar- from the cast) allying it with any number of shall (1982) tentatively referred this speci- higher level marsupial taxa. We have ex- men to Polydolops itself, a decision reversed amined casts of most ofthe marsupials from with the description of a large, fragmentary the Paleocene of Sao Jose de Itaborai, Brazil, paleothentine from Salla, and referral of PU and illustrations of specimens from the Tiu- 21998 to it (Villarroel and Marshall, 1982). pampa Fauna ofBolivia (Muizon, 1991), and Hence there is no positive evidence for a De- the Tinguiririca form agrees closely with none seadan occurrence of polydolopids, and the of them. Likewise, the Tinguiririca form new Tinguiririca taxon represents (with one shows no close similarities with any of the doubtful exception, see below) the last ap- Neogene taxa we have had available for com- pearance of the family. parison. For the moment, therefore, we can Discussion ofan important fossil mammal identify this specimen with no greater spec- collection made early this century by Santi- ificity than Didelphimorphia incertae sedis. ago Roth from Cainadon Blanco (Chubut, Ar- gentina) will be taken up in a subsequent sec- EUTHERLA tion. It is relevant to note here that Roth's collection includes one polydolopid mandib- Edentata: Dasypodidae incertae sedis. Da- ular fragment (MLP 52-XI-4-176), referred sypodids are a fairly common element of the by Marshall (1982), thinking it was Muster- Tinguiririca Fauna. We have recovered sev- san in age, to P. mayoi, an otherwise restrict- eral articulated carapace fragments; a few of ed Mustersan taxon. MLP 52-XI-4-176 is these are greater than 50% complete and con- clearly referable to P. thomasi, however, typ- tain large portions of the remainder of the ically a Casamayoran taxon (we are grateful postcranial skeleton. A relatively poorly pre- to M. Bond for pointing this out). The Ca- served partial cranium (SGOPV 2848) with fiadon Blanco polydolopid is probably not at least one articulated mandible is known associated stratigraphically with the bulk of from the collection. As little of the scute sur- the specimens known from this locale (see face detail is presently visible, we can only below), making this the last known appear- state that the material is clearly not glypto- ance for this family. dontid. Didelphimorphia incertae sedis, new genus Phyllophaga: Pseudoglyptodon, new spe- and species. An enigmatic didelphimorphian cies. One specimen consisting ofa partial cra- is represented by a small mandibular mold nium (SGOPV 2995) with articulating man- (SGOPV 2944) containing only minor enam- dibles of this enigmatic taxon has been el fragments but good impressions of much recovered; it preserves a complete dentition ofthe dentition. We have cast an epoxy resin and partial auditory regions (see Wyss et al., "positive" of this mold, making it possible 1990: fig.4b). Pseudoglyptodon is known from to discern crown morphology in considerable a partial mandible (PU 20552) from the De- detail. The preserved tooth row base of p2- seadan ofBolivia (Engelmann, 1987). A very m4 is approximately 11 mm in length. The similar mandibular fragment bearing one and last molar is the smallest in the molar series; a third teeth from the Mustersan ofPatagonia its lingual face is aligned with the lingual edge (AMNH 29483) was figured by Simpson of the remainder of the cheek tooth series. (1948: 93) who assigned it to the Glyptodon- The talonids are notably broad, and the tri- tidae, doubtfully to Glyptatelus. Engelmann gonids relatively low with paraconids and did not make comparisons to this latter spec- 14 AMERICAN MUSEUM NOVITATES NO. 3098 imen, but it is clear that it and PU 20552 are In a study proposing assignment of disas- very closely related. Glyptatelus Ameghino, sociated proximal tarsal bones from Riochi- 1897, is based on isolated (glyptodontid) can fissure fills of Itaborai to dental species scutes, justifying Simpson's hesitance to refer from the same locality, Cifelli (1983) has con- dental material to it, and Engelmann's rec- vincingly shown that some dentally "primi- ognition of a new taxon Pseudoglyptodon (to tive" (i.e., didolodontoid-like) taxa possessed which the Mustersan AMNH 29483 is refer- diagnostic litoptern ankle specializations. able). In addition, the Tinguiririca specimen More central to the question addressed here, confirms Engelmann's allocation ofPU 20552 Cifelli concluded also (although with less to the Phyllophaga, and clarifies the familial confidence) that one dentally "advanced" (i.e., placement of AMNH 29483. The Tinguirir- litoptem-like) taxon, Victorlemoinia, was as- ica specimen is distinct (at least at the species sociated with a distinctive didolodontoid an- level) from the Salla form (McKenna et al., kle. As pointed out by Cifelli, however, sev- in prep.); more importantly, it adds greatly eral Itaborai taxa represented by teeth are to morphological knowledge of the early di- unknown pedally, suggesting that the con- versification of sloths. verse might also be true; some taxa known Litopterna: Indaleciinae, new genus and from pedal remains might not be represented species. Although its ordinal placement is still by teeth. Although this poses a problem par- open to question, a small, well-preserved ticularly for taxa known from relatively few mandibular fragment containing p4-m3 specimens such as Victorlemoinia, the pro- (SGOPV 3072) represents the only possible posed association was nevertheless favored, litoptern presently known from the Tingui- with Victorlemoinia being excluded from the ririca Fauna. Among recognized litopterns Litopterna on that basis (Cifelli, 1983). and didolodontoids, this specimen clearly In an extensive recent numerical cladistic pertains to the Indaleciinae, a relatively poor- analysis of these groups, therefore, Victorle- ly known group which until recently has been moinia was scored assuming its filiation with considered one of two major subdivisions of a didolodontoid ankle (Cifelli, 1993). Maxi- the adianthid litopterns (Cifelli and Soria, mally parsimonious trees placed Victorle- 1983). Among members of the Indaleciinae, moinia within a dentally plesiomorphic the Tinguiririca form most resembles Inda- grouping termed the Didolodontoidea, along lecia grandensis from the Casamayoran of with Adianthoides and Indalecia (neither of northwestern Argentina (Bond and Vucetich, which is known postcranially), which are 1983), although much of this similarity re- placed as the most immediate outgroups to flects shared plesiomorphy. In light ofits age, Victorlemoinia itself. To determine to what it is interesting to note that the Tinguiririca degree this unexpected exclusion of Adian- form shares no apparent apomorphies with thoides and Indalecia from not only the the youngest previously known indaleciine Adianthidae, but also from the Litopterna, is Adianthoides leali from the Divisaderan of based on the assumed Victorlemoinia dental! west-central Argentina, nor does it share ap- ankle association, we reanalyzed Cifelli's parent apomorphies with the other known (1993) data matrix using PAUP (Swofford, member of this genus, A. magnus from the 1990), scoring Victorlemoinia as unknown for Casamayoran ofPatagonia (Cifelli and Soria, postcranial features. This resulted in group- 1983). If the Tinguiririca form shares special ing of the Victorlemoinia, Adianthoides, In- affinities with any other known indaleciine, dalecia triad with litopterns (but, interest- it is instead with the more northerly Inda- ingly, not near adianthines). Adianthoides and lecia. Indalecia were placed in a similar position A recently proposed phylogeny of archaic within the Litopterna when Victorlemoinia South American ungulates and litopterns (Ci- was simply deleted from the analysis. Pend- felli, 1993) bears on the ordinal allocation of ing a more detailed review of the evidence SGOPV 3072 and therefore requires brief originally used in referring didolodontoid comment. As noted, indaleciines have tra- tarsals from Itaborai to Victorlemoinia, we ditionally been allocated to the Litopterna, believe there is sufficient uncertainty about usually to the famiy Adianthidae. whether these elements might be ascribed to 1 99414WYSS ET AL.: PALEOGENE MAMMALS FROM CENTRAL CHILE 15 a didolodontoid unrepresented by teeth, to serve more detailed comment on this well- warrant continued placement of this taxon, known controversy for a future paper, initial Adianthoides, Indalecia, and the new Tin- analysis leads us tentatively to favor the latter guiririca form in the Litopterna. Although we assignment. differ on the question of ordinal placement, Biostratigraphic and radioisotopic evi- we share Cifelli's (1993; Cifelli and Soria, dence (see below) clearly indicates that the 1983) doubts that these taxa (Indaleciinae), Tinguiririca rodent represents the earliest are closely related to adianthines, therefore record for the order in South America (Wyss leaving familial allocation of the new taxon et al., 1993). In addition to substantially in- unspecified. creasing the minimum age of arrival of ro- Rodentia: ?Dasyproctidae, new genus and dents on the continent, the Tinguiririca ro- species. Undoubtedly the most unexpected, dent offers important new information as well as one of the scarcest, elements ofthe regarding the dental morphology of an early Tinguiririca Fauna is its rodent. Our first ex- representative of the South American en- tensive season ofcollecting produced several demic rodent radiation. specimens identified from cross-sectional views in the field as possible members ofthis NOTOUNGULATA order. As a few of these specimens were pre- pared it became evident that they represented Notostylopidae, new genus and species. A the gliriform marsupials described above. partial palate (SGOPV 2906) preserving Meanwhile, other elements of the fauna be- complete and unworn P4-M2, nearly com- gan to point to its pre-Deseadan age (see be- plete M3, and additional tooth fragments, re- low), and the remaining "presumptive ro- cords the presence of this family. In size and dents" slipped in preparation priority due to morphology the Tinguiririca notostylopid is increasing duplication ofmaterial ofthe mar- most closely comparable to Otronia muehl- supial taxa. Our earlier claim (Wyss et al., bergi from the Mustersan of Chubut Prov- 1990) that the Tinguiririca Fauna predates ince, and Boreastylops lumbrerensis (Vuce- the immigration ofrodents to South America tich, 1980) from the Casamayoran of Salta was overturned when a mandible (SGOPV Province Argentina. These two taxa plus the 2933) indisputably pertaining to this order Tinguiririca form are unique among notosty- was revealed by subsequent preparation lopids in the presence of a papillate mass de- (Wyss et al., 1993). rived from the ectoloph, which occupies the Aside from the anterior end of the incisor crochet region. The Tinguiririca form is dis- and most of p4, the mandible is essentially tinctive, however, in its more strongly de- complete. The cheek teeth are worn, but veloped metacone, more salient paracone and moderate hypsodonty allows a considerable parastyle, better developed cingula, and its amount to be inferred about their original rugose cuspidate protocone base. morphology. The combined length of ml-3 With one possible but unlikely exception is approximately 13 mm. In its development (see below, and under Faunal Comparisons) during wear of three medially placed, isolat- notostylopids are restricted elsewhere to ed, enamel lakes on m2-3, the Tinguiririca Mustersan and older deposits; given its post- rodent, although approximately 20% smaller, Mustersan age, the Tinguiririca occurrence is most closely resembles Branisamys from the probably the latest known for the family. In Deseadan of Bolivia. Otherwise, the Tingui- this context, attention is called to a mandible ririca rodent does not invite close compari- (MLP 12-15 11) from Caiiadon Blanco de- son to any described Deseadan forms from scribed as a notostylopid, Orthogenium either Patagonia or Bolivia. Branisamys is ameghinoi, by Roth (1901), amended (due to variously allocated to the Dinomyidae (Wood preoccupation) to Orthogeniops ameghinoi and Patterson, 1959; Patterson and Wood, (Ameghino, 1902). In discussing this taxon, 1982) and to the Dasyproctidae (Lavocat, Simpson (1948: 171), indicated that "Ortho- 1976), a discrepancy owing principally to dif- genium is probably ofDeseado age and is not fering interpretations of ancestral cavio- a notostylopid," a statement apparently based morph dental morphology. Although we re- on unpublished correspondence from Patter- 16 AMERICAN MUSEUM NOVITATES NO. 3098

son (on file at MLP). Indeed, among the spec- tain early Tertiary (post-early Casamayoran) imens from Cafiadon Blanco available to Pat- age (Pascual, 1983; Alonso et al., 1988), which terson, the one most closely matching Roth's is approximately 20% smaller than the Tin- description, MLP 12-1516 (not numbered in guiririca taxon. In addition to their size, the Roth's time, but apparently cataloged as Or- Catamarca and Tinguiririca forms share the thogenium when examined by Patterson), is distinctive resemblance of marked simplifi- an archaeohyracid. MLP 12-15 11 clearly per- cation of the internal crown pattern. All cris- tains to a notostylopid, although it appears tae and fossettes disappear from the cheek that Orthogeniops does not represent a valid teeth in these two forms, leaving behind a taxon (Bond and Reguero, personal com- featureless occlusal surface after even only mun.). Because the Cafiadon Blanco noto- moderate wear. stylopid is known only from a partial lower Interatheriinae, new genus and species, A, dentition, it cannot be compared directly with B. Two interatheriines are known from the the Tinguiririca form (presently known only Tinguiririca Fauna, one from exquisite ma- from uppers). The approximate length ofp4- terial. We are aware of no published diag- m3 of MLP 12-1511 (32 mm) is equal to the noses of this subfamily, cladistic or other- length of Ml -3 in the Tinguiririca form. The wise, but generally it is construed as including latter therefore seems slightly too large to per- "advanced" (i.e., Deseadan and younger) in- tain to "Orthogeniops." Because the anterior- teratheres. Pending complete formal descrip- posterior dimensions of the upper teeth in tion of these taxa, which will necessitate a the Tinguiririca form would have decreased rigorous analysis and diagnosis, we regard this significantly with wear, however, we caution assemblage as provisionally monophyletic. that referral to the taxon represented at Caina- The larger and more abundant of the two don Blanco is not certainly excluded. interatheriines (indeed, the most abundantly Interatheriidae: Three interatheriids, in- preserved taxon in the Tinguiririca Fauna), cluding members of both currently recog- new genus and species A, is represented by nized subfamilies, "Notopithecinae" and In- several skulls (e.g., SGOPV 2821), complete teratheriinae, are currently known from the dentitions, as well as multiple nearly com- Tinguiririca Fauna. plete postcranial skeletons (see Wyss et al., "Notopithecinae," new genus and species. 1990: fig. 4c). There is considerable variation A new, diminutive taxon is represented by in size and details ofmorphology in the spec- several nearly complete jaws and at least one imens now assigned to new taxon A, making partial cranium preserving an auditory re- it is possible that two species are represented. gion. As the "Notopithecinae" is typically The skull is approximately 95 mm in length regarded as a group of "early [pre-Deseadan] and its general shape is highly reminiscent of and primitive" interatheriids (Simpson, 1967: Notopithecus (see fig. 23 in Simpson, 1967). 74) and lacks an apomorphy-based diagnosis, It displays the hallmark interathere synapo- we employ its subfamilial designation in morphy, a splintlike jugal sandwiched be- quotes to highlight its likely paraphyletic sta- tween maxillary and squamosal contribu- tus. tions to the zygomatic arch (Riggs and Perhaps the most notable characteristic of Patterson, 1935). Establishing the interath- the Tinguiririca "notopithecine" is its mere eriine affinities of this taxon are its large size presence in what is clearly a post-Mustersan and reduction of external ribbing on the up- fauna (see discussion below). In addition to per cheek teeth. In previously known early its late occurrence, the Tinguiririca "noto- interatheriines, a deep, vertically oriented pithecine" is remarkable for its small size; in lingual cleft separates the protoloph and most dental dimensions it is approximately metaloph of the upper molars and posterior half the size of Guilielmoscottia from the premolars, persisting even after extensive Mustersan of Patagonia, for example, pre- wear. By contrast, in new taxon A a narrow viously the youngest known representative of lingual groove is lost after only moderate wear, the subfamily. The only smaller "notopithe- resulting in an undivided internal surface of cine" is an undescribed form from Catamar- these teeth; this condition is doubtless prim- ca Province, northwest Argentina, of uncer- itive for the Interatheriidae (ifnot for a more 1 994 WYSS ET AL.: PALEOGENE MAMMALS FROM CENTRAL CHILE 17 general group of notoungulates). Overall, in- generally we consider each form separately teratheriine, new genus and species A appears listed to be likely distinct. to present a morphology intriguingly transi- Cf. "Bryanpattersonia sulcidens." The tional between "notopithecine" and interath- smallest archaeohyracid in the Tinguiririca eriine interatheres. Fauna is presently represented by a single At lower taxonomic levels, new taxon A prepared specimen, a mandible bearing pl- does not closely resemble previously de- m3 (SGOPV 2954); additional material of scribed members of the Interatheriinae. It is this taxon (including an upper dentition) is most similar to a number of specimens from suspected to be in the collection but remains a pre-Deseadan, post-Mustersan faunule encased in matrix. Bryanpattersonia was known as Lomas Blancas (or La Curandera) erected by Simpson (1967) to accommodate [LBLC] from Patagonia, currently being de- the presumed Mustersan taxa referred to Ar- scribed by Marcelo Reguero of MLP. Agree- chaeohyrax by Ameghino. Ofinterest here is ment between the Tinguiririca interatheriine the smaller of Simpson's two recognized spe- new taxon A and the LBLC material is closest cies, B. sulcidens, erected on the basis ofspec- in the lower dentition; a maxilla (MLP 61- imens referred to Archaeohyrax sulcidens by VIII-3-27) from LBLC appears to be consid- Ameghino (1902) and to A. gracilis by Roth erably advanced relative to the Tinguiririca (1903), but considered conspecific by Simp- taxon. son. SGOPV 2954 agrees very closely with a The second, substantially smaller, Tingui- series of partial mandibles from Cainadon ririca interatheriine, new taxon B, is currently Blanco referred to A. gracilis by Roth. There represented by a single pair of partial man- are minor differences in tooth dimensions be- dibles (SGOPV 3065). As with the larger form, tween the Tinguiririca and Cainadon Blanco new taxon B does not invite close comparison material but these may be due to differences with published forms. Disregarding small dif- in wear. We postpone final decision on ferences in size and crown height, new taxon whether the Tinguiririca and Cainadon Blan- B closely resembles only an undescribed form, co material is referable to the same species known from a single specimen (MLP 12-1529) until additional Tinguiririca material be- from Cafiadon Blanco currently being de- comes available for examination, and until scribed by M. Reguero. The Tinguiririca Fau- completion ofongoing studies by M. Reguero na is the first known to record the co-occur- clarifying the taxonomy ofthe Argentine taxa. rence of both traditionally recognized For the moment, we simply note the close interathere subgroups, interatheriines mak- resemblance between the small Tinguiririca ing their first, and "notopithecines" their last, archaeohyracid and Roth's material from appearances. Can-adon Blanco. Using existing nomencla- Archaeohyracidae. Archaeohyracids con- ture, we therefore provisionally refer SGOPV stitute by far the most diverse element ofthe 2954 to "Bryanpattersonia sulcidens," fully Tinguiririca Fauna. Indeed, containing no aware that the generic and perhaps specific fewer than five and perhaps as many as nine designations of this material are likely to distinct taxa, the Tinguiririca Fauna records change in the near future. The Tinguiririca an archaeohyracid diversity unprecedented "B. sulcidens" is clearly distinct from the taxa among Cenozoic faunas ofany age or location listed below-i.e., none of the Tinguiririca in South America. Uncertainty about the archaeohyracids currently known from upper number of taxa represented owes primarily dentitions (new taxa A, B, D) matches this to the unknown association ofupper and low- taxon in size. er dentitions, and to similar size of most of Archaeohyracid new taxon A: A second the taxa. A few of these forms may, with Tinguiririca archaeohyracid is represented by varying degrees of confidence, be referred to a beautifully preserved rostrum (SGOPV previously known taxa. However, the ma- 2823) with little worn teeth; other than its jority appear to be new, most at supraspecific missing incisors and unerupted M3s, both taxonomic levels. We consider below the taxa sides of the upper dentition are complete. In currently recognized; possible associations of general morphology, degree of hypsodonty, upper and lower dentitions are discussed, but and molarization of posterior premolars this 18 AMERICAN MUSEUM NOVITATES NO. 3098 taxon shows affinities to (but is probably dis- from the Tinguiririca Fauna (see new taxon tinct from) forms variously known as Ar- D, below). II is greatly enlarged and strongly chaeohyrax propheticus Ameghino 1897, A. curved posteriorly. The tips of the opposite patagonicus Ameghino 1897, Archaeotypo- incisors meet but their roots are widely sep- therium transitum Roth 1902, Bry- arated. It is unclear whether the posterior in- anpattersonia nesodontoides (Ameghino cisors, canines, and anterior premolars were 1901) (genus erected by Simpson 1967), and absent or simply reduced; in either case a Archaeohyrax sp. (MacFadden et al., 1985). substantial diastema is indicated. From I1- As post-Mustersan archaeohyracids have not M3 the tooth row measures approximately been revised for nearly a century, their no- 66 mm. We defer more detailed analysis and menclature is in a considerable state of con- description until the right side of this speci- fusion; some of the names listed above men has been prepared. For present purposes doubtless represent synonyms. Whatever the it suffices to note that its enlarged incisor and resolution ofthese nomenclatural uncertain- low-crowned cheek-teeth, particularly in the ties, SGOPV 2823 appears not to pertain to premolar region, sharply differentiate this any previously recognized species. Although taxon from all previously known Mustersan the shape and dimensions of individual up- and Deseadan members of the Archaeohy- per cheek-teeth vary considerably with wear racidae. in these taxa, comparisons of lengths of con- Archaeohyracid new taxon C: This ar- tiguous sections ofthe tooth row are probably chaeohyracid is represented by a fragmentary more reliable indicators of true size differ- mandible (SGOPV 2901) bearing parts offour ences among taxa. In comparison to the taxa teeth, including (with minor damage lin- listed above known from relatively complete gually) most ofm 1-3. It is approximately the material, such measures indicate SGOPV same size as specimens discussed below un- 2823 to be slightly (circa 5%) smaller than A. der Pseudhyrax, and shares some morpho- patagonicus, and 20% smaller than A. pro- logical similarities with that taxon. Setting pheticus, but slightly larger than an unnamed SGOPV 2901 apart from all previously species from Salla (MacFadden et al., 1985; known archaeohyracids, however, is a bizarre personal obs.). No lowers are known to be anteroposteriorly shortened talonid on m2. certainly associated with this taxon but sev- The talonid of this tooth is roughly rectan- eral unprepared specimens are likely candi- gular in outline, but its longest axis lies per- dates for referral. pendicular to the tooth row, resulting in a In addition, we have recovered at least one structure roughly twice as wide as long. Add- skull (SGOPV 2900) which is possibly refer- ing to the tooth's peculiarity is its posteroex- able to this taxon. Although the dentition of ternal termination which forms a tight, nearly this specimen is imperfectly preserved be- 900, corner, in contrast with the smoothly cause ofpostmortem deformation, in general curving form of this region of the talonid it appears similar but slightly smaller than typical of other archaeohyracids. Although SGOPV 2823 (in fact, in terms of size, currently incompletely represented, archaeo- SGOPV 2900 seems to agree closely with the hyracid new taxon C is unmistakably distinct Salla form). Either archaeohyracid new taxon from any archaeohyracid known. Based on A is characterized by strong dimorphism and/ its overall morphology and complimentary or variation, or this skull represents a distinct size, SGOPV 2901 may represent the lowers taxon. In view of the number of certainly to Archaeohyracid new taxon B, but this is distinctive archaeohyracids already known presently speculative. from the Tinguiririca Fauna, we conserva- Archaeohyracid new taxon D: A largely tively consider SGOPV 2900 a small morph complete palate (SGOPV 2851) may repre- of new taxon A. sent a second low-crowned archaeohyracid, Archaeohyracid new taxon B: This highly but more likely is an extremely worn example distinctive taxon is currently represented by of a high-crowned taxon represented by a a single palate (SGOPV 2877). It is one of maxilla (SGOPV 2918). SGOPV 2851 pre- two possible (but probably the only) low- serves a dentition complete except for both crowned archaeohyracids presently known canines and the right incisor series; the entire 1 994 WYSS ET AL.: PALEOGENE MAMMALS FROM CENTRAL CHILE 19 toothrow measures approximately 63 mm. II strangulatus (compared to numerous speci- is small relative to the condition seen in Ar- mens referred to this taxon housed at the chaeohyrax patagonicus, A. propheticus, new MLP), a smaller than average P. euthrachy- taxon B, and the skull tentatively referred to theroides, or a new species of Pseudhyrax. new taxon A. 12 and 3 are similar in shape Choice between these alternatives must await to Il but are only about one-half and one- revision ofP. strangulatus and P. euthrachy- third ofthe latter's size respectively; the three theroides in progress by M. Bond, and the incisors are separated by short diastemata. A establishment of ranges of variation for the 10 mm wide gap separates the premolar and large single-locality samples now available for incisor series; it is not known whether this these taxa. was interrupted by a canine, but even if it The larger morph, represented by SGOPV was, a significant diastema would have been 2985, agrees almost exactly in size and mor- present. The premolars are worn nearly to phology with typical sized specimens of P. the roots; the molars retain 5-10 mm ofcrown euthrachytheroides from the Mustersan of thickness (measured on the external face). Patagonia (Bond, in prep.), and the Chilean We tentatively refer an unusual, extremely form is therefore reasonably referred to this highly crowned, and only moderately worn species. No upper dentitions obviously re- maxilla (SGOPV 2918) bearing P2-M3 to new ferable to Pseudhyrax occur in the Tinguirir- taxon D. Apart from being within about 30% ica Fauna. Given the generally conservative of the same size, SGOPV 2918 and SGOPV morphology of archaeohyracid lower denti- 2851 appear utterly dissimilar at first glance. tions, however, it is conceivable that the low- The molars of SGOPV 2918 are particularly ers of the taxa represented by SGOPV 2887 notable for their extreme hypsodonty and and 2985, although indistinguishable from highly bowed form. The crown height ofM3, Pseudhyrax, are actually the counterparts of measured from the center of the ectoloph at other taxa discussed in this section currently the wear surface to the base ofthe roots along known only from uppers. the tooth's curved external face, is approxi- The Tinguiririca archaeohyracid collection mately 27 mm. Although this contrasts is by far the most important known. It greatly sharply with the condition seen in the palate extends knowledge of the family, both in SGOPV 2851, the "low-crowned" morphol- terms of taxonomic diversity and morpho- ogy ofthe latter specimen is plausibly derived logical completeness. The skulls (in addition from the hypsodont morphology represented to SGOPV 2900 we have at least two more by SGOPV 2918 through extreme wear. The unprepared archaeohyracid crania) are the strongest indicators ofsuch a relationship are earliest known. Prior to discovery ofthe Tin- the concave form and texture of the external guiririca Fauna only a single archaeohyracid face of the base of the molars, and general cranium was known (Ameghino's holotypic cheek-tooth outlines. SGOPV 2918 is sub- material for Archaeohyraxpatagonicus). Un- stantially larger than SGOPV 2851, regard- prepared cranial material promises to clarify less of how much wear is envisioned. Nev- possible associations ofupper and lower den- ertheless, we conservatively allocate these two titions discussed above, permitting a more specimens to the same taxon pending recov- accurate appraisal of the unprecedented di- ery of material in an intermediate wear state versity represented. In addition, the Tingui- or preserving the anterior dentition of a less ririca Fauna provides the first associated worn individual. Several lower jaws (e.g., postcranial material for the family. SGOPV 2917) correspond closely in size and Homalodotheriidae. Trigonolophodon cf. degree of hypsodonty to the less worn of the elegans: The posterior ends ofa pair of large two upper dentitions just described. mandibles (SGOPV 2820) record the occur- Pseudhyrax sp.: Two poorly known but rence of a homalodothere in the Tinguiririca nonetheless distinct morphs are, to all ap- Fauna. In size and morphology SGOPV 2820 pearances, assignable to Pseudhyrax. Both are is virtually identical, in the few elements represented by single mandibular fragments comparable, to the syntype of Trigonolopho- bearing m2-3. The smaller form, SGOPV don elegans (MLP 12-1727), an excellent 2887, is a slightly bigger than average P. mandible including symphysis from Cafna- 20 AMERICAN MUSEUM NOVITATES NO. 3098 don Blanco (Roth, 1903). We have been un- Patagonia. It is significant to note that some able to examine the other species ofthis taxon (ifnot all) ofthese other occurrences are likely named by Roth from the same locality in the from "late" rather than typical Mustersan same publication (T. modicus, T. inflatus), horizons (Bond, personal commun.). Some but dimensions presented by Roth would Ameghino specimens, for example, are la- seem to rule out the former-we provision- beled as coming from "Partie la plus supe- ally refer SGOPV 2820 to T. elegans because rieure de couches a Astraponotus" (latest of their close resemblance. Trigonolophodon Mustersan in current terminology), and species have never been revised and seem to Simpson (1967: 185) made special mention have been nearly universally ignored. Several that his specimen likely referable to this tax- specimens of homalodothere upper molars on (AMNH 29462) was collected from high (which we previously attributed to Periphrag- within his Mustersan section. Moreover, E. nis, Wyss et al., 1990) are represented in the obscurus is not known from typical Muster- Tinguiririca Fauna; it seems reasonable to san deposits that have been well sampled and refer them to the same taxon. Unfortunately collected intensively by Rosendo Pascual, his we have not yet been able to compare these students and colleagues, during the past three upper molars with the specimens collected decades in Patagonia. Again, we are indebted by Roth. to M. Bond for this information. Notohippidae. Four notohippids are pres- Notohippid new taxon A. A second rela- ently known in the Tinguiririca Fauna, all tively large, but far more poorly known no- members of the undoubtedly paraphyletic tohippid occurs in the Tinguiririca Fauna. It "Rhynchippinae." The Chilean specimens is currently represented by a distinctive par- sort into two size classes, each including an tial upper incisor battery (SGOPV 3004); the "advanced" and a "primitive" form. Our closed incisor arcade indicates its notohippid discussion begins with the currently best affinities. A maxillary fragment with two teeth known form, the large "advanced" type, and (P4-M1) roughly three-quarters complete proceeds in order of decreasing size. (SGOPV 2883) may represent the same tax- Eomorphippus, new species. A relatively on. Little may presently be said about this large notohippid is represented by a rostrum taxon, but it clearly does not pertain to preserving a complete upper dentition Eomorphippus, new species, described above (SGOPV 3046), at least one nearly complete (although it is approximately the same size), lower dentition, as well as some additional nor does it closely resemble any known no- mandibular fragments. This taxon is similar tohippid. In contrast to E. obscurus and E., (and undoubtedly closely related to) but dis- new species, the incisors are low-crowned tinct from MLP 12-1508, the type ofEurys- (enamel is restricted to the tips and does not tomus stehlini Roth, 1901, referred (on Pat- extend to the roots), and the canine is similar terson's recommendation) by Simpson (1967) in size and shape to the incisors. Similarly, to Eomorphippus obscurus Ameghino, 1901. the cheek-teeth of this taxon are much less The Tinguiririca form differs from MLP 12- hypsodont than their counterparts in E. ob- 1508 principally in being approximately 20% scurus and E., new species. larger, in having a slightly more reduced up- "Eomorphippus cf. pascuali." A fragmen- per canine, and in minor differences in upper tary maxilla preserving P2 through the an- incisor widths. Otherwise, the two forms are terior halfofMl and an erupting M3 (SGOPV extremely similar in tooth crown morphol- 2991), plus an isolated m3 (SGOPV 3096) ogy and high degree ofhypsodonty (including represent a taxon provisionally referable to the incisors). "Eomorphippus pascuali." The taxonomy of For several reasons, E. obscurus is proba- "rhynchippine" notohippids is badly in need bly latest Mustersan or younger in age, rather of revision and is plagued with inadequate than a typical Mustersan taxon as it is usually types, greatly complicating proper designa- considered. E. obscurus is best known from tion of the Tinguiririca material. E. pascuali the post-Mustersan, pre-Deseadan (at least in was erected by Simpson (1967) on the basis part) Cafiadon Blanco fauna (see below), but of a maxilla (AMNH 29405) selected as its also occurs elsewhere in the Mustersan of type, and a mandible (AMNH 29474) doubt- 1994 WYSS ET AL.: PALEOGENE MAMMALS FROM CENTRAL CHILE 21 fully referred, collected from the same local- clude the relatively poorly known ?middle ity (high in the Mustersan section) that pro- Eocene Mustersan (known almost exclusively duced AMNH 29462 (see above). It is clear, from Argentine Patagonia), the very incom- however, that E. pascuali (whether or not pletely known and peculiar ?Eocene-Oligo- AMNH 29474 is correctly referred) is only cene Divisaderan (west-central Argentina- relatively distantly related to the only other the age of neither of these SALMAs is con- recognized species of Eomorphippus, and strained by independent dating), and the pre- therefore warrants a different generic desig- sumably slightly younger and much better nation. M. Bond has identified the distinc- represented Deseadan (known also primarily tiveness of a taxon previously placed in syn- from Argentine Patagonia and the Salla beds onymy with Eomorphippus (Simpson, 1967), ofBolivia) (Simpson et al., 1962; Hoffstetter, and its similarity to specimens currently re- 1976, MacFadden et al., 1985). Whether the ferred to E. pascuali; pending his formal res- Divisaderan is in fact distinct from the urrection of that name (which has priority Deseadan has recently been questioned over E. pascuali), we employ current no- (MacFadden et al., 1985; Marshall et al., menclature, inadequate as it is. Thus, while 1986 -but see Bond, 1991 for contrary view). SGOPV 2991 is referable (or is very closely Moreover, there remains considerable dis- related) to specimens currently identified as agreement about temporal calibration of the Eomorphippus pascuali, both halves of this Deseadan (ibid.). Nonetheless, a growing body binomial are subject to change in the near ofradioisotopic and paleomagnetic data sug- future. gest most or all of the Deseadan SALMA to Notohippid new taxon B. A fourth noto- be significantly younger than early Oligocene hippid from the Tinguiririca Fauna is pres- (MacFadden et al., 1985; Sempere et al., 1990; ently known from a pair of mandibles Flynn and Swisher, in prep.), its traditional (SGOPV 2855) preserving at least one rep- placement, a view consistent with results pre- resentative of each tooth position except the sented here. The enormous length of time canine and pl. Notohippid new taxon B is encompassing the poorly known interval be- strikingly similar in most comparable mor- tween the Mustersan and Deseadan SALMAs phological details to the taxon described (likely 15-25 m.y., depending on which cal- above as Eomorphippus, new species, but is ibration of the Deseadan is accepted), is rel- only slightly greater than one-half its size. evant to the comparisons presented below. Otherwise it is quite unlike any other known Biostratigraphic evidence indicates the notohippid. This taxon may therefore rep- Tinguiririca Fauna to be neither Mustersan resent a second new species of Eomorphip- nor Deseadan in age, but to represent some pus, or a distinct generic-level taxon; choice intermediate interval not corresponding to between these alternatives awaits recovery of the Divisaderan either (Wyss et al., 1993). referable upper dental remains and a system- Ruling out assignment of the Tinguiririca atic analysis of the taxa involved. Fauna to the Mustersan (or older SALMAs) Isotemnidae, incertae sedis. Several man- is the occurrence of numerous higher-level dibular fragments, a partial mandibular mold, taxa known elsewhere only from Deseadan and other fragmentary dental remains refer- and younger faunas. These include interath- able to this family have been recovered from eriine interatheres, Rodentia, members or the Tinguiririca deposits. These specimens close allies of the genus Archaeohyrax, and are generally too incomplete to allow confi- perhaps argyrolagids. Arguing against assign- dent identification, but one appears to agree ment of the Tinguiririca Fauna to the De- rather closely with Rhyphodon. More precise seadan or younger faunas is the occurrence taxonomic assignment of the Tinguiririca of taxa not certainly known elsewhere from isotemnid(s) must await collection and prep- post-Mustersan faunas including notostylo- aration of additional material. pids, "notopithecids," polydolopids, and Pseudhyrax. With the caveat necessary for all FAUNAL COMPARISONS cases of negative evidence, it is important to South American mammal faunas brack- point out a few characteristically commonly eting the Eocene-Oligocene transition in- preserved Deseadan taxa absent from the 22 AMERICAN MUSEUM NOVITATES NO. 3098

Tinguiririca Fauna. Hegetotheres, Pyrothe- rodents (Wyss et al., 1993). Geochronologic rium, advanced members of the Interather- evidence further substantiates a pre-Desea- iinae (including for example Plagiarthrus), dan age for the Tinguiririca rodent (ibid.). In notohippine notohippids, mesotheres, neso- sum, several independent lines of evidence dontine toxodonts, caenolestids, and glyp- suggest that the Tinguiririca rodent is pre- todontids are all unrecorded in the Tingui- Deseadan in age. ririca Fauna. Similarly, the joint occurrence of Pseudo- Aside from their containing markedly dif- glyptodon in the Tinguiririca Fauna and the ferent groeberiids and indaleciines, the Tin- Deseadan of Bolivia cannot be used to argue guiririca and Divisaderan faunas share few for a Deseadan age assignment for the former. taxonomic resemblances. Oldfieldthomasiid It may be recalled that in addition to the notoungulates, the dominant element of the occurrence ofPseudoglyptodon at Salla, a very Divisaderan fauna, are unknown in the Tin- similar Mustersan mandibular fragment guiririca Fauna. Beyond stating that the Tin- (AMNH 29483), doubtfully referred to Glyp- guiririca Fauna and the Divisaderan are ob- tatelus by Simpson (1948), almost certainly viously distinct, significant difficulties and pertains to Pseudoglyptodon (McKenna et al., contradictions are encountered in attempting in prep.). Hence Pseudoglyptodon is not re- to place the two faunas in any temporal se- stricted to the Deseadan, and its presence in quence. These problems will be taken up after the Tinguiririca Fauna does not require ref- further consideration ofthe Tinguiririca Fau- erence to that interval. na relative to the much better known Desea- Although primates are not presently known dan SALMA. from the Tinguiririca Fauna, the group's rar- The Tinguiririca Fauna shares two impor- ity in the South American fossil record gives tant resemblances with the Deseadan, neither cause for optimism that they may yet be of which necessarily indicates, however, an found. If, as is often assumed, rodents and assignment of the fauna to that SALMK It primates arrived in South America roughly is remarkable that a rodent is known from simultaneously, these hiatus-filling deposits the Tinguiririca Fauna-this marks the first from the Tinguiririca valley of Chile afford known co-occurrence of the gliriform mar- what is perhaps the most promising oppor- supials Polydolopidae and Groeberiidae, with tunity for discovery of platyrrhine primates true members of the superorder Glires, for significantly older than those presently example (Wyss et al., 1993). By itself, the known. biostratigraphic evidence set forth above As repeated references to close morpho- strongly indicates the Tinguiririca Fauna to logical similarities in many ofthe taxonomic predate the Deseadan, implying that the Tin- descriptions above suggest, the Tinguiririca guiririca form is the earliest known rodent on Fauna appears most closely related tempo- the continent. rally to a collection of specimens described Because of their high diversity in known by Santiago Roth between 1901 and 1903 Deseadan faunas (with more than a dozen from a locale currently referred to as Caina- taxa from as many as six families currently don Blanco (but as "Terciario inferior de recognized), rodents are generally believed to Cainadon Blanco" by him). Because this fau- have arrived in South America substantially na has largely been ignored since then, a brief earlier than strict reading oftheir fossil record account of its history is warranted. would suggest. This is indicated both by their Several factors have contributed to obscure high diversity at first appearance in Deseadan the significance ofRoth's relatively small col- strata, and by recognition that this debut fol- lection from Caniadon Blanco. First, most of lows a lengthy hiatus, which has lead to a Roth's taxonomic descriptions for this fauna longstanding expectation that pre-Deseadan were intended only as brief, preliminary notes, rodents would eventually be found. In agree- consisting of no more than a few sentences, ment with biostratigraphic evidence, it is of providing only rudimentary anatomical and interest that the Tinguiririca form is not mensural information, and lacking illustra- clearly assignable to, or obviously closely al- tions. Second, Roth, a rival of the Ameghi- lied with, any previously known Deseadan nos, kept the location of many of his most 1 994 WYSS ET AL.: PALEOGENE MAMMALS FROM CENTRAL CHILE 23 productive localities secret, and to this day residuum of specimens from Cainadon Blan- Cainadon Blanco has not been relocated (it is co (including the notostylopid and polydo- known only to be within Chubut Province). lopid-see above) are suggestive of a Casa- And third, the taxonomic assemblage attrib- mayoran age (Bond and Reguero, personal uted to Ca-nadon Blanco was unlike any commun.). Unless similar forms are even- known until nearly a century later. This led tually identified in the Tinguiririca Fauna, to Patterson's suggestion (unpublished notes caution dictates that we assume a small num- on file MLP, in-and adopted by-Simpson, ber of Casamayoran specimens "contami- 1967, e.g., pp. 13, 114) that contrary to Roth's nates" the otherwise pre-Deseadan post- affirmations, the Ca-nadon Blanco fauna was Mustersan Caiiadon Blanco collection. not derived from a single stratigraphic ho- Pending the results of ongoing taxonomic rizon, but represented a mixture ofspecimens analysis, we comment only briefly on the rel- from Casamayoran, Mustersan, and Desea- ative age of the Tinguiririca and Cafiadon dan age faunas. In subsequent descriptions, Blanco faunas. Age comparisons are compli- therefore, Cainadon Blanco specimens were cated by incomplete knowledge of the Ca- variously allocated (on the basis of unstated nadon Blanco Fauna (in terms ofnumbers of but presumably "stage ofevolution" criteria) specimens-small bodied taxa especially- Casamayoran, Mustersan, or Deseadan ages, and taxic diversity) relative to that from Tin- and Roth's collection ceased to exist as a rec- guiririca, and the uncertain stratigraphic as- ognized fauna. We have studied Roth's col- sociation ofthe Argentine specimens, raising lection at the Museo de La Plata firsthand the issue ofwhich faunal differences are sam- and have found the bulk ofit to be uncannily pling artifacts and which are real. Thus it is similar to the Tinguiririca Fauna, with sev- difficult to judge the significance of the ap- eral taxa identical at the species level (or near- parent absence from Cainadon Blanco ofsuch ly so) being shared. Discovery of the Tin- "archaic" Tinguiririca forms as "notopithe- guiririca Fauna has demonstrated rather cids" and "Eomorphippuspascuali," and the conclusively, therefore, that most of Roth's apparent absence of such "progressive" Tin- Ca-nadon Blanco collection does indeed con- guirirican forms as the rodent and Interath- stitute a fauna. eriinae new taxon A. Given these limitations, Ongoing, more detailed description of the and instances of apparently conflicting data Tinguiririca Fauna by ourselves, and revision (a rodent in the Tinguiririca Fauna but ap- ofthe Cainadon Blanco fauna by M. Reguero parent absence ofthe group at Cafnadon Blan- ofMLP, will define more precisely the degree co, presence of an hegetothere at Cafiadon of congruence between the two faunas. For Blanco but not in Chile), all that can presently now we wish merely to emphasize again the be stated with confidence is that the two fau- close similarity between Eomorphippus ob- nas are very similar in age. scurus from Cainadon Blanco and Eomor- Temporal placement of the Divisaderan phippus, new species, from Tinguiririca, the relative to other better known Eocene-Oli- close correspondence between the taxon de- gocene SALMAs is also not satisfactorily re- scribed above as Interatheriinae, new genus solved and discovery ofthe Tinguiririca Fau- and new species B with an undescribed form na only increases this uncertainty. Since its from Caniadon Blanco, and the close simi- recognition as a distinct SALMA (Pascual et larity of the homalodothere and "Bryanpat- al., 1965, 1966) the Divisaderan has been tersonia sulcidens" from the two faunas. typically regarded as latest pre-Deseadan or Apparent even from these preliminary com- earliest Deseadan in age, a view called into parisons is that a long sought fauna inter- question by identification of the Tinguiririca mediate in age beteen the Deseadan and Mus- Fauna as pre-Deseadan. tersan was found by Santiago Roth -it simply If "advanced" faunal elements from Divi- took nearly a century to be recognized as such. sadero Largo are emphasized for correlation, Discovery ofthe Tinguiririca Fauna thus lends then at least partial equivalence with the De- impetus to a renewed search for Cainadon seadan might be indicated. This has come to Blanco. be the accepted view in some recent treat- Finally, it should be added that a small ments of the problem (MacFadden et al., 24 AMERICAN MUSEUM NOVITATES NO. 3098

1985; Marshall et al., 1986), with Trachythe- crowned herbivores, a changeover likely re- rus, Acamana, and Ethegetotherium serving lated to climatic shifts and establishment of as proposed "taxonomic ties" between the seasonally drier and more open habitats (e.g., Deseadan and Divisaderan [we recognize that grasslands and/or savanna woodlands; ibid.; at least some ofthese identifications are open Janis, 1989). From geochronologic data pre- to question (Bond, 1991), but accept them sented below, the Tinguiririca herbivore fau- here for the sake of simplifying the discus- na appears to indicate that a shift to this type sion]. Alternatively, but not usually empha- ofdentition, accommodating an abrasive diet, sized, if more "primitive" aspects of the Di- occurred significantly earlier in South Amer- visaderan fauna are considered, a closer ica than in various taxa on the northern con- correlation of it to older faunas is suggested tinents. (Bond, 1991). This would be indicated, for Another intriguing feature of the Tingui- example, by the occurrence of oldfieldtho- ririca Fauna is that it documents a mixture masiids and indaleciines in Divisaderan and of northern and southern South American Casamayoran SALMAs, and their absence in faunal elements, reflecting early Cenozoic lat- the Deseadan. itudinal biogeographical zonation, long ad- Discovery of the Tinguiririca Fauna (and vocated by Rosendo Pascual (see Pascual and acceptance of its pre-Deseadan age) intro- Ortiz Jaureguizar, 1990, and references duces a new wrinkle to the Divisaderan prob- therein). In that contemporaneous deposits lem. The Tinguiririca Fauna is not presently are unknown outside of Patagonia (i.e., in known to contain hegetotheres, mesotheres, northern South America), and given its great- orAcamana, all ofwhich imply that it is older er proximity to that southern region, it is not than the Divisaderan. Unlike the Divisa- surprising that the bulk of the Tinguiririca deran, however, the Tinguiririca Fauna lacks Fauna is "Patagonian" in character. Less ex- oldfieldthomasiids, it has a groeberiid that is pected, perhaps, is the occurrence of a "no- "advanced" in certain respects relative to the topithecid," an indaleciine, and a groeberiid, Divisaderan Groeberia, and it contains such all ofwhich are either unknown in Patagonia Deseadan elements as rodents and interath- or show closest affinities to northern repre- eriines not known from the Divisaderan. All sentatives ofthese groups. Hence the peculiar possible temporal sequences of these faunas mixture of taxa present in the Tinguiririca present certain inconsistencies which are be- Fauna is probably attributable to temporal ing explored in ongoing work. On balance, as well as geographic factors, its novel com- we cannot discount the possibility that the position reflecting the sampling ofpreviously Tinguiririca Fauna is younger than the Divi- poorly known time and latitudinal intervals. saderan, which would imply in turn that the Divisaderan is considerably older than gen- erally believed (Bond, 1991). GEOCHRONOLOGY High levels of endemism preclude corre- lation of most of the South American Land FAUNAL DISCUSSION Mammal Age succession to the global geo- A striking feature ofthe Tinguiririca Fauna logic timescale by traditional biostratigraphic is its domination by extremely high-crowned methods. Aside from rare marine intercala- notoungulates, including several species of tions, magnetostratigraphy and radioisotopic notohippids, interatheres, and archaeohyra- dating provide the two most powerful means cids. Conspicuous in their absence are such of global correlation for Cenozoic South low-crowned forms as oldfieldthomasiids, American terrestrial deposits. Single crystal other "archaic" lineages such as archaeopith- 40Ar/39Ar dates for horizons within, above, ecids, and low-crowned representatives ofthe and below the fossil-bearing sequence at the Archaeohyracidae, which characterize pre- Cerro Alto del Padre and El Fierro Pass lo- Deseadan faunas elsewhere in South America calities (see Geographic Setting) are present- (Pascual et al., 1985). The Tinguiririca Fauna ed in table 3. Special significance attaches to thus represents the first South American these results because the Abanico Formation mammalian community dominated by high- represents the single known post-Riochican, 1 994 WYSS ET AL.: PALEOGENE MAMMALS FROM CENTRAL CHILE 25 pre-Deseadan mammal-producing unit con- nozoic mammal evolution has long been taining datable volcanic horizons from any- plagued by gaps in the paleontological record, where on the South American continent. As the most significant of these being an ap- such, these dates are particularly relevant to proximately 15-25 million year hiatus pre- current disagreement about the lower tem- ceding the Deseadan SALMA. The Tingui- poral boundary ofthe Deseadan SALMA (see ririca Fauna clearly falls within this gap. The above). Multiple dates from within and im- Tinguiririca Fauna represents the first Paleo- mediately beneath the fossiliferous horizon gene mammal fauna known from Chile, the indicate that the fauna is at least as young as only mammal fauna known from the central about 31.5 Ma, meaning that the beginning Andean Main Range (if not the entire Main ofthe Deseadan must be somewhat younger. Range), and the only well represented Eo- Dates from basalts and sediments underly- cene-Oligocene transitional fauna from the ing, but within the same stratigraphic unit as, continent. the fossiliferous horizon indicate that the fau- 2) The Tinguiririca Fauna contains the nal assemblage may be as old as late Eocene oldest rodent from South America. The source (circa 37.5 Ma), and might therefore span the area and age ofarrival ofthis immigrant group Eocene-Oligocene boundary. (as well as primates) have long been vigor- Recognition of a new interval of land ously debated. The new fauna significantly mammal evolution: The Tinguiririca Fauna extends the minimum age of the first ap- would appear to have several characteristics pearance of rodents (but not as yet primates) warranting its recognition as a distinct and on the continent. biochronologically informative land mam- 3) The span separating the Mustersan and mal age. First, in its mixture of first and last Deseadan SALMAs coincides with an im- appearances of several higher-level taxa, the portant mammalian faunal transition, a turn- Tinguiririca Fauna agrees almost exactly with over from communities dominated by vari- what would have been predicted for an in- ous "archaic" lineages, to communities of a terval of this age. Second, the Tinguiririca much more "modern" aspect. The Tingui- Fauna is known from many exceptionally ririca Fauna provides the first detailed view complete specimens and is taxonomically di- of this transition. verse, increasing its usefulness as a tool for 4) Many early Cenozoic SALMAs remain correlation. Third, there already appears to poorly sampled radioisotopically (if sampled be one known geographically distant locality at all). Dates (table 3) from volcanic horizons (Cainadon Blanco) characterized by a very associated with the Tinguiririca Fauna are similar suite of taxa. And fourth, the fauna the first reported from a 30 million year pre- occurs in sediments that have been radioiso- Deseadan span, and help to constrain the cur- topically dated. We delay formal recognition rently debated lower temporal bound of the of a new SALMA, however, pending com- Deseadan SALMA. pletion of a more detailed taxonomic char- 5) The age of the Tinguiririca Fauna and acterization of the Tinguiririca Fauna, and its stratigraphic context significantly perturb more complete publication ofthe fauna from currently accepted interpretations ofthe geo- Cainadon Blanco and LBLC by our colleagues tectonic history of the region. The Tinguirir- at the Museo de La Plata. ica mammals represent the first chronologi- cally significant paleontological find for a major sequence ofcentral Andean rock units, SUMMARY OF SIGNIFICANCE OF and demonstrate the utility of fossil verte- TINGUIRIRICA FAUNA brates for elucidating various geologic prob- The newly discovered Tinguiririca Fauna lems in this physiographic province. sheds light on an important phase of South American mammalian evolution and pro- vides an important new source ofgeochrono- ACKNOWLEDGMENTS logic information for this region ofthe Andes. We thank D. Frassinetti and Director Luis Following are the study's major conclusions: Capurro, Museo Nacional de Historia Nat- 1) Understanding of South American Ce- ural, Santiago for their sponsorship of our NO. 3098 26 AMERICAN MUSEUM NOVITATES

TABLE 3 Age of the Tinguiririca Fauna (from Wyss et al., 1993)

Analysis Age number 37Ar/39Ar 36M/39 4OAr*/39Ar %4Ar* Ma + SD Sample 90CS-TDF20 (plagioclase) 5259-01 5.6536 0.01943 53.0933 90.9 32.065 1.331 5259-02 5.6216 0.02251 52.8218 89.4 31.902 0.704 5259-03 3.3264 0.01558 50.2486 93.3 30.361 1.828 5259-04 4.7746 0.00786 52.9391 96.4 31.972 0.504 5259-05 5.1316 0.02409 51.3102 88.4 30.997 0.662 5259-06 4.8035 0.08048 51.9572 68.9 31.384 1.220 Weighted mean = 31.646 0.320 altered grain? 5259-07 23.0828 1.04709 91.2434 22.6 54.757 11.634 Sample 90CS-TDFl9 (plagioclase) 5258-01 5.4000 0.00788 51.9069 96.4 31.354 0.468 5258-02 6.8320 0.21235 51.9136 45.4 31.358 1.514 5258-03 5.0410 0.03627 52.1694 83.4 31.511 0.539 5258-04 5.7482 0.04452 51.6674 80.2 31.211 0.580 5258-05 5.1570 0.01104 51.9845 94.7 31.401 0.365 5258-06 5.0637 0.01760 52.6603 91.6 31.805 0.665 5258-07 5.0960 0.00474 51.5102 98.1 31.117 0.446 5258-08 4.5901 0.01085 51.7061 94.7 31.234 0.358 Weighted mean = 31.335 0.171 Combined weighted mean of TDF19 and 20 = 31.404 0.151 Sample 90CS-TWHO (plagioclase) 5241-02 1.9288 0.12751 61.2378 62.0 37.307 1.154 5241-05 0.3615 0.05299 60.9994 79.6 37.163 0.776 5241-06 0.4021 0.15814 61.8658 57.0 37.685 1.078 5241-07 0.4862 0.02445 62.0831 89.6 37.816 0.521 5241-08 0.3676 0.00909 62.0903 95.9 37.820 0.512 Weighted mean = 37.671 0.305 contaminant grains? 5241-01 0.4813 0.16370 64.9995 57.3 39.573 1.911 5241-03 0.3814 0.03255 62.6420 86.7 38.153 0.896 Sample 90CS-TWHO (biotite) 5242-01 0.0276 0.50394 61.3023 29.2 37.345 3.252 5242-03 0.0617 0.44815 60.8075 31.5 37.047 2.572 5242-04 0.0078 0.51079 61.2037 28.8 37.286 3.233 5242-05 0.0433 0.38783 61.6036 35.0 37.527 2.357 5242-06 0.0219 0.30230 60.9613 40.6 37.140 1.205 5242-07 0.1022 0.39658 61.1127 34.3 37.231 2.372 Weighted mean = 37.216 0.849 altered grain? 5242-02 0.0232 0.49516 51.5898 26.1 31.480 3.973 * = radiogenic. le + le, = 0.581 x 10-10 yr-1; lb = 4.962 x 10-10 yr-1; 40K/40Ktotal = 1.167 x 10-4. The age of the Tinguiririca Fauna was ascertained through 40Ar/39Ar laser total-fusion techniques applied to plagioclase and biotite separated from volcaniclastic horizons ofthe Abanico Formation. Mineral grains were treated 1994 WYSS ET AL.: PALEOGENE MAMMALS FROM CENTRAL CHILE 27

TABLE 3_-(Continued) in an ultrasonic cleaner with dilute (- 0.7%) hydrofluoric acid for 5 min to remove any altered glass and adhering clays, then rinsed for 5 min in distilled water. They were irradiated together with a centrally located monitor mineral (Fish Canyon Tuff sanidine), for 30 min in the hydraulic rabbit core facility of the Omega West research reactor at Los Alamos National Laboratory following previously described procedures (Swisher et al., 1992). After irradiation, single crystals of the monitor mineral and Abanico samples were loaded into individual 2 mm diameter wells of a copper sample disk, placed within the sample chamber of the extraction system, and baked out at 200'C for 8 hours. Total fusion ofthe samples and monitor mineral was accomplished with a 6W Coherent Ar ion laser. Released gases were purified by two Zr-Fe-V getters operated at approximately 150°C, and condensable gases were collected on a -45°C cold-trap. Argon was measured in an on-line Mass Analyzer Product 215 noble-gas mass spectrometer operated in static mode. Laser heating, gas purification, and mass spectrometry were completely automated following computer programmed schedules (Swisher et al., 1992). The 40Ar/39Ar ages were calculated using a J value determined from replicate analyses of individual grains of the coirradiated monitor mineral Fish Canyon Tuff sanidine (FC) with a reference age of 27.84 Ma intercalibrated in-house with Minnesota hornblende MMhb-I with a published age of 520.4 Ma (Cebula et al., 1986; Samson and Alexander, 1987). The 40Ar/39Ar dating of single crystals of plagioclase and biotite separated from sample 90CS-TWHO, the stratigraphically lowest sample dated from the Abanico For- mation, yielded weighted mean ages of 37.67 ± 0.31 Ma (SE) and 37.22 ± 0.85 Ma (SE), respectively. Samples 90CS-TDF20 and 90CS-TDFl9 yielded concordant ages of 31.65 ± 0.32 Ma (SE) and 31.34 ± 0.17 Ma (SE). A combined weighted mean ofboth of these samples indicates an age of 31.40 ± 0.15 Ma (SE). The maximum output of the laser during this study was approximately 8 watts. Ca and K corrections were determined from laboratory salts: (36Ar/37Ar)Ca = 2.6 x 10-4 + 5.0 x 10-6, (39Ar/37Ar)Ca = 6.7 x 10-4 + 3.0 x 10-5 and (40Ar/39Ar)K = 2.03 x 10-2 ± 4.0 x 10-4. J, the irradiation parameter, is based on replicate single-crystal analyses of the monitor mineral Fish Canyon Sanidine and is 0.0003412 ± 0.0000005 for sample 90CS-TWHO and 0.000338 ± 0.0000005. Mass discrimination during this study, as determined by replicate air aliquots delivered from an on-line pipette system, was 1.006 ± 0.0002. Decay constants are those recommended by Steiger and Jager (1977) and Dalrymple (1979). work in Chile. Financial support was provid- script we thank Mariano Bond, Alfredo Car- ed by the National Geographic Society (3932- lini, Francisco Goin, Guillermo L6pez, Ro- 88), the National Science Foundation (DEB sendo Pascual, Marcelo Reguero, and 9020213), the Eppley Foundation, the Frick Guiomar Vucetich. For access to collections Laboratory Endowment Fund, DTI (U. and the extension ofnumerous courtesies fa- Chile), and a UCSB Junior Faculty Improve- cilitating our work we are indebted to R. Pas- ment Grant. Fossils were skillfully prepared cual. Numerous people have helped with col- by A. Davidson, R. Masek, S. McCarroll, and lecting in the field including J. D. Bryant, J. W. Simpson. The figures were prepared by Christinet, G. Gould, R. Hitz, J. Meng, C. E. Heck. J. Davis assisted in the editing. For Veloso, and F. Zapatta; in this regard we generous assistance with identification ofthe would like to single out especially the talents fauna and/or helpful comments on the manu- and efforts of Gabriel Carrasco. REFERENCES

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NOTE ADDED IN PROOF Despite recent suggestions to the contrary geochronologic control for the type Divisaderan [L. G. Marshall and T. Sempere, 1993, Evolution fauna from Argentina, this supposed temporal cor- of the neotropical Cenozoic land mammal fauna respondence is oflittle consequence. Accordingly, in its geochronologic, stratigraphic and tectonic several conclusions of a recent tectonic study of context, In P. Goldblatt (ed.), Biological relation- the central Andes (Sempere et al., 1994), are called ships between Africa and South America, pp. 329- into question. Among these is the proposed 35 392, New Haven, Yale Univ. Press; T. Sempere, million year maximum age of onset of foreland L. G. Marshall, S. Rivano, and E. Godoy, 1994, deposition in adjacent Argentina (based on the Late Oligocene-Early Miocene compressional tec- suspect biostratigraphic tie between the Divisa- tosedimentary episode and associated land-mam- dero Largo Formation and the Tinguiririca Fau- mal faunas in the Andes of central Chile and ad- na). Thus the supposed lower temporal bracket for jacent Argentina (32-37°S), Tectonophysics 229: an unconformity underlying Deseadan aged strata 251-264], we reiterate our earlier stated conclu- in neighboring Argentina is inadequate to rule out sion that the Tinguiririca Fauna is not assignable an early to middle Eocene age ofonset offoreland to the Divisaderan SALMA. Given the lack of basin formation and coeval Andean deformation. specific biostratigraphic evidence offered in its Timing of the termination of Cenozoic deforma- substantiation, these authors' proposed assign- tion in the central Andes is well understood; its ment ofthe new Chilean fauna to the Divisaderan commencement remains the problem. Critical is SALMA appears to have been influenced by the age of initiation of deposition of the Abanico "agreement" between radioisotopic dates associ- Formation, an issue still not adequately resolved. ated with the Tinguiririca Fauna (this report and It also merits note that the recently proposed elsewhere) and a proposed 30-36 million year age subdivision of the Deseadan SALMA into pre- for the Divisaderan (Marshall et al., 1986). In view, and post-arrival of caviomorph rodent portions however, of biostratigraphic evidence strongly (Marshall and Sempere, 1993), is now obviated contradicting such an assignment (this report, and by occurrence of a caviomorph in the pre-Desea- earlier publications), and the continuing lack of dan Tinguiririca Fauna (Wyss et al., 1993). Recent issues of the Novitates may be purchased from the Museum. Lists of back issues of the Novitates, Bulletin, and Anthropological Papers published during the last five years are available free of charge. Address orders to: American Museum of Natural History Library, Department D, Central Park West at 79th St., New York, N.Y. 10024.

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