Paleontology and Geochronology of the Deseadan (late

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Number 3668, 24 pp., 8 figures, 5 tables November 30, 2009

Paleontology and Geochronology of the Deseadan(late Oligocene) of Moquegua, Peru

BRUCE J. SHOCKEY,1 RODOLFO SALAS GISMONDI,2 PHILLIP GANS,3

ANNIE JEONG,4 AND JOHN J. FLYNN5

ABSTRACT

Subsequent to our initial reports of the discovery of Deseadan fossils in southern Peru, we haveobtained new data regarding the paleontology and geology of the upper member of the MoqueguaFormation. These data include newly recovered fossil specimens and further analyses of thosecollected in our earlier field seasons. We have also obtained an ash directly from within the fossil-bearing units near the summit of Cerro Pan de Azucar. Biotites from this Sugarloaf ash give an ageestimate of 26.25 6 0.10 Ma, thus supporting our previous suggestion that these fossil-bearinghorizons are of late Oligocene age (Deseadan South American Land Mammal ‘‘Age’’) andremoving our query regarding a possible early Miocene age. Most of the fossils are ofnotoungulates and most of these are trachytheriine mesotheriids. Remarkably, three distinctmesotheriid taxa appear to have been present in the Moquegua fauna, none of which are referableto the common Trachytherus alloxus of the nearby and at least partly contemporaneous Salla bedsof Bolivia. Other fossils documented here include postcranial elements of the notohippidnotoungulate, Moqueguahippus, a macraucheniid litoptern (cf. Coniopternium), an osteoderm of anunnamed species of armadillo (Dasypodidae, cf. Dasypodinae), and a claw of a phorusrhacid bird.We also describe a diminutive new hystricognath rodent, Sallamys quispea, sp. nov. It is similar to,but distinct from, S. pascuali of Salla. Indeed, despite the temporal and geographic proximity ofMoquegua to Salla, none of the taxa from Moquegua that can be identified to species are knownfrom Salla. Likewise, we have failed to find any dasypodids from Salla that have osteoderms likethat described in this work. Thus, it is appears that distinctive paleogeographic and

Copyright E American Museum of Natural History 2009 ISSN 0003-0082

1 Department of Biology, Manhattan College, New York, NY 10463. Research Associate, Division of Paleontology,American Museum of Natural History ([email protected]).

2 Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, Lima, Peru ([email protected]).3 Department of Geological Sciences, University of California at Santa Barbara ([email protected]).4 Biology Department, Barnard College, New York ([email protected]).5 Division of Paleontology and Richard Gilder Graduate School, American Museum of Natural History (jflynn@

amnh.org).

paleoenvironmental conditions in the late Oligocene led to a regional biotic differentiation for theMoquegua area of coastal Peru.

INTRODUCTION

Upper regions of peaks west of the RıoMoquegua, near the city of Moquegua (fig. 1),have yielded the first known fossils of theDeseadan South American Land Mammal‘‘Age’’ in Peru (Shockey et al., 2006). Sincepreparation of the initial report of thisdiscovery, additional data have been gathered

regarding the paleontology and geology ofthese localities in the upper member of theMoquegua Formation. The new data includeadditional specimens collected in subsequentfieldwork, further analyses of previouslycollected material, and 40Ar-39Ar geochrono-logical analyses of an ash collected fromdirectly within the fossil-bearing horizons nearthe summit of Cerro Pan de Azucar (fig. 2).

Fig. 1. Geologic map of the fossil localities of the upper Moquegua Formation. Based on: Bellido, E.and C. Guevara. 1961 (Mapa Geologico del Cuadrangulo de Clemensı, Carta Geologica Nacional yInstituto Geografico Militar); Shockey et al., 2006: fig 1; and satellite images from Google Earth.Trachytheriine localities of Bolivia are indicated in insert map at upper right: Salla (Trachytherus alloxus); A,Lacayani (T. spegazzinianus); and B, Rıo Iru Pluma (T. subandinus).

2 AMERICAN MUSEUM NOVITATES NO. 3668

Most of the fossils recovered are of no-toungulates. The present work describes post-cranial remains from three species of me-sotheriid notoungulates, including the nearlycomplete pes of the largest of the three (cf., T.spegazzinianus). This represents the first suchdescription of any mesotheriid pes. Also, wedescribe additional material of the notohip-pid notoungulate, Moqueguahippus glycismaShockey et al., 2006, and we expand the faunallist by reporting the remains of the onlyxenarthran (Dasypodidae, cf. Dasypodinae),and a diminutive new species of rodent,Sallamys quispea, closely related to but dis-tinct from the Deseadan species S. pascualifrom Salla, Bolivia.

As detailed below, the geochronologicalanalysis provides a date of 26.25 6 0.10 Mafor the ash that lies in the lower part of thefossil-bearing sequence. This date stronglysupports the initial conclusion that the faunacollected is late Oligocene in age, thus

removing prior uncertainty regarding a possi-ble early Miocene age for the fossil-bearingunits (Shockey et al., 2006).

BACKGROUND

The Tertiary sediments in the Moquegua/Tacna Basin traditionally have been referredto as the Moquegua Formation (Bellido andGuerra, 1963) or Moquegua Group (Tosdalet al., 1981; Acosta et al., 2002), composed ofthe ‘‘formacion Moquegua inferior’’ andthe ‘‘formacion Moquegua superior’’ (seeSempere et al., 2004, for discussion ofnomenclature problems). These are separatedby an angular unconformity (Acosta et al.,2002; Sempere et al., 2004); in addition, the‘‘lower Moquegua Formation’’ consists offiner sediments than the upper.

Work in progress (see Sempere et al., 2004)may clarify the complex depositional historyof the Tertiary deposits of southern Peru and

Fig. 2. Photo of the north face of the summit of Cerro Pan de Azucar illustrating the lower region of theupper Moquegua Formation, including the Sugarloaf ash. (The boundary between the lower and upperMoquegua Formation is covered at this locale.) Note crew members hiking up the slopes for an impressionof scale.

2009 SHOCKEY ET AL.: THE DESEADAN OF MOQUEGUA, PERU 3

the resulting unstable geological nomencla-ture. The strata of interest for our studyinvolve the upper unit of the MoqueguaFormation (sensu Bellido and Guevara,1963; Bellido and Landa, 1965; Tosdal et al.,1981; equivalent to: ‘‘Formacion MoqueguaSuperior’’ of the Moquegua Group [Acosta etal., 2002]; ‘‘Formacion Moquegua superior’’[Flores et al., 2004] or ‘‘Upper MoqueguaFormation’’ [Shockey et al., 2006]; ‘‘Mo-quegua C’’ [Sempere et al., 2004]; MoqueguaFormation [Sanchez Fernandez et al., 2000]),underlain by the lower unit of the MoqueguaFormation (equivalent to: ‘‘Formacion Mo-quegua Inferior’’ of the Moquegua Group[Acosta et al., 2002]; ‘‘Formacion Moqueguainferior’’ [Flores et al., 2004]; ‘‘Moquegua B’’[Sempere et al., 2004]; Sotillo Formation[Sanchez Fernandez et al., 2000]). For conve-nience, given this conflict among variousstratigraphic assignments, we will refer tothe upper part of the Moquegua Formationas the ‘‘upper Moquegua Formation’’ andthe lower part as the ‘‘lower MoqueguaFormation.’’

Bellido and colleagues (Bellido and Landa,1965; Bellido and Guevara, 1963) character-ized the Moquegua Formation as continentalsiltstones, sandstones, and conglomerates.Conglomerates form the base of the upperMoquegua Formation (fig. 2) with overlyingfiner-grained lagoonal facies (Tosdal et al.,1981; Acosta et al., 2002). These are composedof clayey and fine-grained sandstones andmudstones, with pink ignimbrite intercalations(Acosta et al., 2002). The regionally extensivelower Moquegua Formation locally uncon-formably overlies the late Cretaceous to earlyTertiary Toquepala Group (Tosdal et al.,1981; Marocco and Noblet, 1990; Acosta etal., 2002; and fig. 1).

Tosdal et al (1981) obtained 40K-40Ar dates(25.3 6 0.8, 23.3 6 0.8, and 22.7 6 0.8 Ma)from three widely separated ignimbrite expo-sures near the top of the upper MoqueguaFormation, all east of the Moquegua River.Our new dates (40Ar-39Ar) come from an ashwest of the Moquegua River, near the summitof Cerro Pan de Azucar. This Sugarloaf ashlies just above the basal conglomerates, thusrepresenting a stratigraphically older horizonthan those sampled by Tosdal et al., 1981, for

their 40K-40Ar geochronological analysis (see40Ar-39Ar Geochronology below).

The Moquegua Formation has generallybeen considered ‘‘nonfossiliferous’’ (Tosdal etal., 1981). However, in 2002, Rossana Quispeand her classmates and instructor (JorgeAcosta) from the Universidad Nacional‘‘Jorge Basadre Grohmann,’’ Tacna, Peru,found fossils in the upper MoqueguaFormation, at and just below the summit ofCerro Pan de Azucar (Shockey et al., 2003,2006). This initial discovery motivated ourmore intensive National Geographic–spon-sored fieldwork in the austral winters of 2002to 2004, with results detailed here.

MATERIALS, ABBREVIATIONS, METHODS

Specimens collected from the Deseadanaged localities of the upper Moquegua For-mation are curated in the MUSM (Depart-amento de Paleontologıa de Vertebrados,Museo de Historia Natural, UniversidadMayor de San Marcos, Lima, Peru). Otherinstitutional abbreviations used in the textinclude: UF (vertebrate paleontology collec-tions, Florida Museum of Natural History,University of Florida, Gainesville, FL,U.S.A.); AMNH (American Museum ofNatural History, New York, NY, U.S.A.).

Additional abbreviations used in this studyinclude SALMA, South American LandMammal ‘‘Age’’; I, C, P, and M for upperincisors, canines, premolars, and molars,respectively (lowercase notation for lowerteeth).

The 40Ar-39Ar ages were obtained at theargon geochronology laboratory in theDepartment of Earth Sciences at theUniversity of California, Santa Barbara.Conventional stepwise-heating and plateau-age analyses were conducted on biotite sepa-rates (Sugarloaf biotites) obtained from theash collected above the basal conglomeratesbelow the summit of Cerro Pan de Azucar.

GEOGRAPHIC AND GEOLOGICAL CONTEXT

The Tertiary Moquegua localities lie 50 kminland from the Pacific in the coastal plains ofsouthern Peru, east of the Cordillera de laCosta and west of the Cordillera Occidental of


the Andes (fig. 1). These fossil-bearing beds ofthe upper Moquegua Formation are encoun-tered only at the summits of a series of peaks(Cerros Pan de Azucar, Mono, and SantaAna) flanking the western banks of the RıoMoquegua, which regionally runs along the W71u longitudinal line in the Departamento deMoquegua, Peru. Cerro Pan de Azucar islocated 9 km WSW of the city of Moquegua,at S17u12.8719 and W71u0.6619 (elevation1663 m). Cerro Mono (elevation 1780 m)stretches from 2 to 6 km SW of Cerro Pande Azucar, and Cerro Santa Ana (elevation1790 m), S17u16.8669 and W71u2.7449, lies10 km SW of Cerro Pan de Azucar.

Intensive prospecting for fossils in the vast,but accessible, area of outcrop of the lowerMoquegua Formation was entirely unproduc-tive. All fossils found during our fieldworkcame solely from the summits of the moun-tains where the upper Moquegua Formation isexposed. For the most part, the fossils werebroken and scattered on the surface of theheavily weathered sediments.

40AR-39AR GEOCHRONOLOGY: A volcanicash (‘‘Sugarloaf ash,’’ in reference to its beingfrom Pan de Azucar [5 Sp. sugarloaf]) isexposed on the north face of Cerro Pan deAzucar, about 20 m below the summit and

20 m above the upper Moquegua Fm./ lowerMoquegua Fm. contact (figs. 1: a on map; 2).A sample of this ash was collected atS17u13.0169 and W71u0.7869 and a 2.3 mgseparate of biotites was subjected to astepwise-heating 40Ar-39Ar geochronologicalanalysis. Each dwell time lasted 12 min attemperatures that ranged from 650u C to1300u C. Plateau temperatures occurred at820u, 880u, 940u, 980u, 1020u, 1060u, 1100u,1140u, and 1190u C.

These data provided a total fusion age (TFA)of 25.90 6 0.05 Ma (including ‘‘J,’’ a summationterm for a series of variables, determined byplacing a ‘‘flux monitor’’ sample of known age inthe reactor with the sample whose age is beingdetermined, see table 1), a weighted-mean pla-teau age (WMPA) of 26.24 6 0.05 Ma (includ-ing J), and an inverse isochron age of 26.21 60.17 Ma (see table 1 and fig. 3). These yield a40Ar-39Ar age determination for the Sugarloafash of 26.25 6 0.10 Ma. This late Oligocene agefalls within the currently accepted time span ofthe Deseadan SALMA (Flynn and Swisher,1995; Kay et al., 1998), and is consistent with theoccurrence of Deseadan SALMA fossils thatwere all collected within about 20 m above thelevel of the ash or 10 m below, all within theupper Moquegua Formation.

TABLE 1

Analytical Data for 40Ar/39Ar for the Sugarloaf Biotites of Cerro Pan de AzucarSample: SB51-18, Sugarloaf Biotite, J50.0020807

T (uC) t 40(mol) 40/39 38/39 37/39 36/39 K/Ca S 39Ar 40Ar* Age (Ma)

650 12 1.6e214 13.4769 1.9e22 0.1618 0.0284 3.0 0.03529 0.377 19.0 6 0.3

750 12 3.0e214 9.1264 1.8e23 0.0399 0.0082 12 0.13503 0.736 25.0 6 0.1

820 12 2.0e214 8.7735 3.5e24 0.0351 0.0057 14 0.20587 0.807 26.4 6 0.1

880 12 2.1e214 8.6844 0.0e+0 0.0176 0.0053 28 0.28003 0.821 26.6 6 0.1

940 12 2.3e214 8.8685 0.0e+0 0.0136 0.0061 36 0.36067 0.798 26.4 6 0.1

980 12 2.7e214 9.6360 5.8e24 0.0152 0.0085 32 0.44637 0.738 26.5 6 0.1

1020 12 3.2e214 9.4337 0.0e+0 0.0135 0.0081 36 0.55122 0.745 26.2 6 0.1

1060 12 4.0e214 8.6092 2.3e24 0.0102 0.0055 48 0.69330 0.810 26.0 6 0.1

1100 12 4.1e214 7.9361 0.0e+0 0.0111 0.0030 44 0.85017 0.887 26.2 6 0.1

1140 12 2.5e214 7.6858 0.0e+0 0.0133 0.0022 37 0.95080 0.916 26.2 6 0.1

1190 12 1.1e214 7.6572 0.0e+0 0.0476 0.0018 10 0.99326 0.929 26.5 6 0.2

1250 12 1.5e215 9.2983 0.0e+0 0.2417 0.0062 2.0 0.99821 0.802 27.8 6 1.3

1320 12 7.6e216 13.0247 1.2e23 0.2417 0.0229 2.0 1.00000 0.482 23.4 6 4.0

Total fusion age, TFA5 25.90 6 0.05 Ma (including J); weighted mean plateau age, WMPA5 26.24 6 0.05 Ma

(including J); inverse isochron age 526.21 6 0.17 Ma.; (MSWD 54.52; 40Ar/36Ar5297.8 6 8.4); steps used: 820, 880, 940,

980, 1020, 1060, 1100, 1140, 1190uC, (3–11/13 or 86% S 39Ar); t 5 dwell time in minutes; 40 (mol) 5 moles corrected for

blank and reactor-produced 40; ratios are corrected for blanks, decay, and interference; S39Ar is cumulative, 40Ar* 5 rad

fraction.


This date of 26.25 6 0.10 Ma from 20 mabove the lower/upper Moquegua Formationboundary provides a radioisotopic age deter-mination within the lower part of the upperMoquegua Formation. This date for the baseof the upper Moquegua Formation is congru-ent with the younger 40K-40Ar age determina-tions of Tosdal et al. (1981) for the upper partof the upper Moquegua Formation, whichranged from 22.7–25.3 Ma.

SYSTEMATIC PALEONTOLOGY

CLASS AVES LINNAEUS, 1758

FAMILY PHORUSRHACIDAE AMEGHINO, 1889

Genus and species indeterminate

Figure 4A

MATERIAL: MUSM 351, ungual phalanx,collected in the upper Moquegua Formation,near the eastern summit of Cerro Mono (fig.1: e on map).

COMMENTS: Despite many hours of pros-pecting in the area where this avian ungualphalanx of was found, no further material of

this large bird has been recovered. Its presenceat Moquegua was previously noted (Shockeyet al., 2006) and we here provide a photo(fig. 4) of the single element from what musthave been a moderately large bird.

In terms of its size, curvature, and pres-ence of lateral nutrient grooves, the avianclaw from Cerro Mono is similar to that ofthe Santacrucian (middle Miocene) Pho-rorhacos (see Sinclair and Farr, 1932). It isnot referred to Phororhacos, however, as it is alittle smaller and has a lower degree ofcurvature. The material is inadequate to referto any of the known Deseadan genera ofphorusrhacid (e.g., Physornis, Andrewsornis,or Psitopterus; see Alvarenga and Hofling,2003).

CLASS MAMMALIA LINNAEUS, 1758

MAGNORDER XENARTHRA COPE, 1889

ORDER CINGULATA ILLIGER, 1811

FAMILY DASYPODIDAE GRAY, 1821

CF. DASYPODINAE GRAY, 1821

Fig. 3. Ar age spectra for the Sugarloaf biotite of Cerro Pan de Azucar. TFA 5 total fusion age; WMPA5 weighted mean plateau age.


Genus and Species Indeterminate

Figure 4B

MATERIAL: MUSM 1604, an isolated os-teoderm, the anterior portion of which is

poorly defined. It was found in the upperMoquegua Formation, about 20 m below andsoutheast of the summit of Cerro Pan deAzucar, in the area where the holotype ofSallamys quispea was found (fig. 1: d on map).

Fig. 4. Miscellaneous postcranial elements. A, phorusrhacoid claw (MUSM 351), in lateral and plantarviews; B, dasypodid osteoderm (MUSM 1604) from the articulating region of the carapace; C,macraucheniid metapodial (MUSM 349) in dorsal, lateral, and plantar views; and D, right cuboid(MUSM 669) in dorsal and medial views.


COMMENTS: MUSM 1604 is a movable-band osteoderm. It is rectangular, small, andslender, measuring 16.0 mm long and 4.7 mmwide. The lateral margins are smooth andfairly straight. The posterior border is slightlyrounded; it is partly damaged, but five pits,likely sites for hair follicles, are recognizable.The central figure is delimited by two parallelsulci connected anteriorly and reaching theposterior margin. Each sulcus presents twolarge nonaligned foramina and a number ofdispersed smaller ones. The articulation zoneis well defined by a transverse bevel. As insome movable osteoderms of Dasypus novem-cinctus, some foramina are identified justbehind the bevel.

MUSM 1604 almost certainly represents anew taxon of a small Deseadan dasypodid,similar in size to Dasypus hybridus. Unfor-tunately, the scarcity of well-documentedmaterial of coeval taxa and the fragmentarycondition of the present record discourages usfrom erecting a new species. It is probably aDasypodinae based on the surface design ofthe osteoderm. The longitudinal and parallelsulci imply the existence of overlapping scalescovering lateral areas of two adjacent scutes(secondary horny scales), an apomorphy forthe Dasypodinae (Vizcaıno, 1994; but seeCiancio and Carlini, 2008). Its systematicposition within the group is uncertain, though.

The Dasypodinae consist of the followingtribes: Astegotheriini (including Stegotheriini;sensu McKenna and Bell, 1997) from thePaleocene to the Miocene (see Vizcaıno, 1994),and Dasypodini from the Miocene to thepresent (Vizcaıno, 1990; Carlini et al., 1997).Despite the vast expanse of time, generalshape, and outline of movable osteodermsshow little difference between both tribes. Asin the Deseadan armadillo from Moquegua,they are thin and slender in Astegotheriini andDasypodini (see Vizcaıno, 1994; Carlini et al.,1997). This conservative character was onceused to diagnose the tribe Astegotheriini(Vizcaıno, 1994), but has since been regardedas representing a primitive state in the Dasy-podinae evolution (Oliveira and Bergvist,1998). The phylogenetic significance of thesutures of the margins is ambiguous, althoughthey have implications regarding structuraldemands of the carapace. In MUSM 1604 the

margins are smooth, similar to what is seen inthe Astegotheriini. Vizcaıno (1994) suggestedthat in these animals the carapace was moreflexible than in modern Dasypodini wherethe scutes are fixed by spicules along theirlateral margins. The osteoderms of archaicAstegotheriini and the Dasypodinae fromMoquegua may have been bounded togetherby soft tissue.

In most Astegotheriini from the Casamayorian-Mustersan of Patagonia (e.g., Astegotherium)the main figure is lageniform and the sulci donot reach the posterior margin (see Vizcaıno,1994). In Anadasypus hondanus from theMiddle Miocene of La Venta (Colombia),parallel sulci diverge laterally to reach the sidesjust before getting to the posterior margin. It isconsidered the oldest member of theDasypodini because this pattern suggests thederived state seen in extant species of Dasypus,in which the secondary keratin scutes aretriangular (Carlini et al., 1997). In the osteo-derms, the synapomorphy is revealed by thedivergent sulci that reach each posterolateralcorner (Vizcaıno, 1990). In the dasypodinefrom Moquegua, surface design of the osteo-derm implies (1) secondary horny scales wererectangular—not triangular and (2) each sec-ondary scale took up the total length of thevisible surface of the osteoderm. This combi-nation of characters is not seen in the earlymembers of the Astegotheriini, but it may havebeen attained and by a cluster of a pre-Dasypodini during the Oligocene.

ORDER RODENTIA BOWDICH, 1821

SUBORDER HYSTRICOGNATHA TULLBERG, 1899

SUPERFAMILY OCTODONTOIDEA SIMPSON, 1945

GENUS SALLAMYS HOFFSTETTER AND LAVOCAT,1970

Sallamys quispea, sp. nov.

Figures 5 and 6; table 2

HOLOTYPE: MUSM 1404, jaw fragmentwith lower right dp4-m1.

REFERRED SPECIMENS: Known only fromthe holotype.

TYPE LOCALITY: The upper MoqueguaFormation, about 20 m below and southeast


of the summit of Cerro Pan de Azucar (fig. 1:d on the map).

ETYMOLOGY: The specific name, quispea, isgiven to honor Rossana Quispe of the city ofMoquegua, who discovered the first fossilsknown from the Moquegua Formation. Shealso participated in all our field projects in theMoquegua Formation, during one of whichshe found the holotype of this diminutiverodent.

DIAGNOSIS: Smaller than all knownDeseadan and Santa Rosa local fauna (Peru)rodents, slightly smaller than the smallestknown specimens of Sallamys pascuali;

brachydont; trilophate m1 with occlusal con-nection of the posterolophid to the hypololo-phid, mesolophid extending from the ectolo-phid; metalophid intersecting midpoint ofanterolophid. The m1 anterolophid has a spurthat with more wear would subdivide thefossetid into two. The m1 is subquadrangular,whereas dp4 is more ovoid. Molariform dp4;hypolophid with a small, posteriorly extendingspur; anterolophid extends from protoconidaround the anterior end of tooth to themetaconid, so that the anterolophid spur andmetalophid tip join to form a figure eight–shaped fossetid.

Fig. 5. Holotype of Sallamys quispea, MUSM 1404. Micrographs provide views from four perspectives(occlusal [A], lateral [B], medial [C], and medial oblique [D]) as well as close ups of the occlusal surfaces ofm1 (E) and dp4 (F).


DIFFERENTIAL DIAGNOSIS: Sallamys quispeadiffers from rodents of the Deseadan assem-blage from Salla, Bolivia, in the followingways: It is most similar in overall morphologyto Sallamys pascuali, but with lower crownheight; dp4 not as molariform, but subequal insize to m1 (just 3% longer than m1 inmesiodistal dimension), whereas dp4s of S.pascuali are larger (14%–25% longer than m1);anterior lophid of dp4 continuous fromprotoconid to metaconid, lacking the flexidthat separates protoconid from anterior lo-phid of S. pascuali and lacking a secondmesiolabial flexid; mesolophid of dp4 withoutconnection to metaconid; less pronouncedrecurvature of lingual extreme of posterolo-phid of dp4 and m1; posterior spur athypolophid-ectolophid junction of m1 shorter.Dental dimensions smaller than those of S.pascuali (mesiodistal dimension of dp4 just82% that of smallest dp4 of S. pascuali and m1mesiodistal dimension similar to that of onlythe smallest of individual sampled of S.

pascuali, but with transverse dimension short-er than all). Differs from Branisamys luri-bayensis in its much smaller size (m1 mesio-distal dimension just a third of that of B.luribayensis); m1 having only three majorlophids, mesolophid not distinct or fullyformed. Differs from Incamys bolivianus insmaller size (linear dimensions 40%–65% ofthose of Incamys); labial hypolophid andposteriorlophid of m1 closer, forming a unitedcrest with little wear (persistently separated inIncamys); lingual spurs projecting from ante-rolophid of m1 with formation of an ante-rofossetid. Differs from Migraveramus beatusin having only three major lophids (mesolo-phid short, not reaching the metaconid), widermeta- and mesoflexids, and considerablysmaller size (m1 mesiodistal dimension lessthan 75% to those of M. beatus).

Sallamys quispea differs from rodents of theDeseadan of Patagonia: Differs from Platy-pittamys in more complex anterolophid, twoanterofossetids. Differs from Deseadomys aram-

Fig. 6. Comparative anatomy of dp4 and m1 of Sallamys spp. A, Right dp4 and m1 of S. quispea, sp.nov. (holotype, MUSM 1404 ), shown as a SEM micrograph (left) and a line drawing (right) to illustrate theterminology used in the text. (Terminology based on Patterson and Wood, 1982; and Candela, 1999:Abbreviations: hypf 5 hypoflexid; hyp-lophd 5 hypolophid; mesf 5 mesoflexid; post-lophid 5posterolophid; prtcnd 5 protoconid.) B, is the right dp4 and m1 of PU 20909, Sallamys pascuali, inwhich the dp4 reflects the morphology of that of the holotype (Hoffstetter and Lavocat, 1970). C is a left dp4and m1 (digitally reversed to appear as right) of Sallamys, cf. S. pascuali, UF 114458, in which themorphology of the dp4 is distinct from that of the holotype and referred specimen PU 20909 (see Pattersonand Wood, 1982: fig. 5d, and text for discussion). Photo of PU 20909 E Yale Peabody Museum of NaturalHistory, New Haven, Connecticut.


bourgi by hypolophid more parallel to bordersof occlusal surface and having additionalanterofossetid. Differs from Deseadomys loo-misi by presence of mesoslophid and semblanceof metalophid. Differs from Scotamys bycomplexity of lobes and lack of cementum.Differs from Cephalomys by short hypoflexid,longer metaflexid and mesoflexid, brachy-donty. Differs from Asteromys punctus by itsmuch lower crown height, shallower flexids,and its much smaller size.

Differs from all known Santa Rosa localfauna rodents (Eosallamys, Eoespina, Eodel-phomys, Eoincamys, Eobranisamys, Eopicure,Eopululo, Eosachacui) by m1 lacking a thirdfossetid of nearly equal length and depth, afeature characteristic of all members of the‘‘Santa Rosa local fauna’’ rodent assemblage(Frailey and Campbell, 2004).

DESCRIPTION: Among Deseadan rodents(and those from the uncertain age SantaRosa local fauna), Sallamys quispea is closestin size and morphology to Sallamys pascuali,falling just below the lowest part of the sizerange of dental measures of specimens of S.pascuali from Salla (see table 2 and differential

diagnosis above). Our study of a sample ofsmall rodents from Salla referred to S. pascualiillustrates that that species is quite variablemorphologically (assuming that all of theseteeth indeed pertain to a single species). Onedp4 (PU 20909; fig. 6B; see also Patterson andWood, 1982: fig. 5d) has a discontinuousanterolophid separated from the protoconidby a flexid and further divided by ananterolabial flexid near the mesial apex ofthe tooth. Unlike that of S. quispea, theanterolophid connects to the mesolophid inthe Bolivian specimens (PU 20909 and in UF14458). The UF specimen, however, lacks theanterolabial flexid near the mesial apex asoccurs on PU 20909. The wear pattern in bothmorphs is similar to that of the newMoquegua species of Sallamys in which thelabial side wears more quickly than the lingualin both m1 and dp4. The mesiolingual end ofthe m1 of the Salla and Moquegua specimenshave an ‘‘E’’ formation, made up of the tip ofthe anterolophid, a spur, and a short metalo-phid. In Sallamys quispea, however, the tip ofthe anterolophid joins with the metalophidrather than with the spur.

TABLE 2

Measures (mm) of the dp4 and m1 of Holotype (MUSM 1404) of Sallamys quispea sp.nov. of Moquegua, Peru, Compared to Those of Sallamys pascuali of Salla, Bolivia

Data of Yale Peabody (PU) specimens are from Patterson and Wood, 1982.

Taxon Tooth Mesiodistal (A/P) length Greatest width Height

Sallamys quispea dp4 1.80 1.25 1.0

m1 1.75 1.70 0.85

Sallamys pascuali

UF 114458 dp4 2.40 1.80 1.20

m1 2.10 2.20 1.30

UF 114756 m1 1.75 1.95 1.05

UF 114759 m1 2.00 2.05 1.45

UF 114837 m1 1.85 2.05 1.45

UF 92802 m1 2.10 1.90 1.45

UF 92805 m1 2.10 2.30 1.50

UF 114455 m1 1.80 1.80 1.10

UF 121163 m1 1.90 2.00 1.20

UF 114484 m1 1.90 1.90 1.25

PU 20907 m1 1.84 1.92 –

PU 20908 m1 1.92 2.01 –

PU 20909 dp4 2.32 1.47 –

m1 1.89 2.03 –

PU 20910 m1 1.98 2.06 –

PU 20912 m1 2.00 2.15 –

PU 21950 m1 2.10 1.97 –


The m1 of Sallamys quispea has a distinct,but short, mesostylid, as does UF114759(absent in PU 20909), but the m1 of the newtaxon still is more complex in the anterior endof the molar than in the comparative speci-mens of Salla. The posterior side of thehypolophid is undulating in the new species.It is unlikely that S. quispea, at the same wearstage, would resemble UF 114759 and main-tain a similar depth in its flexids (as in UF114759).

COMMENT: Patterson and Wood (1982)considered the flexids of the dp4 of diagnosticsignificance for the genus Sallamys; that is,species of Sallamys should be recognizable bythe presence of two labial, one mesiolabial,and two lingual flexids. The absence of themesiolabial flexid in at least one Salla speci-men of Sallamys (UF 114458) and in S.quispea (which also lacks the labial flexidbetween the protoconid and anterolophid)indicates that the flexid number of the dp4 isan unreliable means of recognizing the genusSallamys and apparently even the species S.pascuali.

ORDER LITOPTERNA AMEGHINO, 1889

FAMILY MACRAUCHENIIDAE GERVAIS, 1855

Genus and Species Indeterminate(cf. Coniopternium sp.)

Figure 4C, D

MATERIAL: MUSM 669, edentulous anddamaged left mandibular ramus and rightcuboid, found in slump below the conglomer-ates that form the base of the upperMoquegua Formation at the western flanksof Cerro Pan de Azucar; MUSM 349, distalmetapodial from the eastern summit of CerroMono.

COMMENTS: The metapodial (fig. 4C) isasymmetric and has a strong keel, thusrepresenting one of the supportive metapo-dials (Mc II or IV; or Mt II or IV). Its distalkeel is well developed, especially on theplantar surface where it is tall and bladelike.Unlike metapodal IIIs of macraucheniids(Loomis, 1914: fig. 10; Shockey, 1999) thekeel extends to the dorsal surface; however, itdoes not rise as high as that on the plantar

side. The distal width is 18.2 mm, which isabout the size of a similar element from Salla,cf. Coniopternium sp. (UF 173216), which hasa distal width of 19.4 mm.

The cuboid (fig. 4D) is similar to that ofConiopternium andinum described and figuredby Loomis (5 Notodiaphorus crassus ofLoomis, 1914: fig.12). The apex of ourspecimen is damaged, thus obscuring anyastragalar facet as noted by Loomis (1914)and Shockey (1999) for Coniopternium. TheMt IV facet is 17.0 mm wide and 21.1 mmdeep. In distal view it is pear shaped, with theapex directed to the plantar side and widestdimension near the dorsal surface.

As known so far, the macraucheniid ofMoquegua is not distinct from comparablematerial representing Coniopternium spp.from Salla, but it is too small to be referredto the Patagonian species, C. andinum. Un-fortunately, diagnostic elements for Coniop-ternium, such as dentitions or the calcaneum,are lacking, so we must remain uncertain as toeven the generic taxonomic reference of themacraucheniid of Moquegua.

ORDER NOTOUNGULATA ROTH, 1903

SUBORDER TOXODONTIA OWEN, 1853

FAMILY (PARAPHYLETIC) NOTOHIPPIDAE

AMEGHINO, 1894

Moqueguahipppus glycismaShockey et al., 2006

Figure 7 and table 3; Shockey et al.,2006: fig. 3

MATERIAL: Holotype, MUSM 348, leftmandible with p1–3 (p4 and m1 missing) andm2–3, discovered by Rossana Quispe andcolleagues at Cerro Pan de Azucar (fig. 1: bon map); and the following referred speci-mens: MUSM 676, left premaxilla withfragment of anterior maxilla with damagedand or badly worn anterior teeth: I2, I3, dCand C, dP1, and dP2 and P2, found at CerroSanta Ana by Eucebio Diez (fig. 1: h on map);and MUSM 964 associated postcranials,including left astragalus, distal humerus, leftproximal radius, unciform, left Mc III, andproximal end of Mc II (?) found by WalterAguirre atop the east-west ridge between the


two major summits of Cerro Mono atS17u13.8359 and W71u2.0209 (fig. 1: f on map).

DESCRIPTION: Moqueguahippus glycisma isdistinguished from other notohippids by itsunique character complex that includes itsrelatively large size, absence of entolophidfossettids of lower molars, presence of cemen-

tum over the teeth, and distinctive lowerpremolar morphology (Shockey et al., 2006).Moqueguahippus had previously been knownfrom the holotype only, but new materialprovides some information regarding theupper dentition and a few details of itspostcranial skeleton.

Fig. 7. Moqueguahippus glycisma. A, MUSM 676, (left) left rostrum with I2-3, dC, C, dP1 and P2; (right)close up of dentition; and MUSM 964: B, left astragalus in (clockwise) dorsal, lateral, distal, and plantarviews; C, right unciform in dorsal and distal views; and D, two manual ungual phalanges in dorsal view.


Based on its size and by the cementumpresent on the teeth (fig 7A), MUSM 676 isreferred to Moqueguahippus. It is a portion ofthe muzzle of a subadult in the process ofshedding its milk teeth just as the adult C andP2 are erupting. It apparently had no diastemaas there are no gaps between any of the teethbetween I1–P2. The general form of themuzzle indicates that it was rounded, similarto that of Rhynchippus equinus and Eury-genium pacegnum, but unlike that of Eo-morphippus obscurus and Pascualihippus boli-viensis, (see Simpson, 1967, and Shockey,1997, respectively) which have broad premax-illary regions with transversely linear incisivebatteries. Owing to wear and breakage, noneof the crowns of the teeth are preserved.

The I1 is missing and the crowns are brokenfrom I2–3. The premaxillary/maxillary suturebetween I3 and the canines (C and dC) isdistinct and (in palatal view) extends mediallyto the distal most point of the incisiveforamen. The incisive foramen is teardropshaped, almost entirely enclosed by thepremaxilla. The C is erupting just anteriorand lateral to the heavily worn dC. The crownof the C is broken and that of the dC brokenat the anteriolabial quadrant. The dP1 isreniform in occlusal view and is so heavilyworn that no crown topology is seen. As istypical, but not universal in notohippids, thedP1 does not seem to be replaced (we observean exception in FMNH P 13410 Rhynchippusequinus in which both the dP1 and P1 arepresent). The dP2 is unusual in that it issmaller than dP1. The erupting P2 is broken,leaving no hint of its form, other than that it,too, was relatively small.

MUSM 964 includes various postcranialelements found in close association. The mostinstructive elements are of the pes and manus.

The astragalus of Moqueguahippus (fig. 7B)has extremely asymmetric trochlear ridges,

similar to that of Trachytherus. It differs by itsshort neck, broad head, lack of a peronialprocess, and by its more parallel lateral andmedial sides whereas those sides are oblique inTrachytherus, giving a greater transversedimension to the plantar surface than thedorsal. The head of the astragalus ofMoqueguahippus is unusually broad. Thetransverse dimension of the head (20.2 mm)is greater than the width of the trochlea(17.2 mm). The sustentacular facet grades intothe broad articular region of the head. Theectal facet does not lie on the same plane asthe sustentacular facet, but is oblique to it,having more of a vertical component to it.

Only a portion of the tuber of calcaneumwas found among the remains of MUSM 964.However, the distal fibula has a flat distalarticular surface, nearly perpendicular to thevertical astragalar facet, indicating that therewas significant contact and articulation be-tween the fibula and calcaneum.

The unciform (fig 7C) is distinct from thatof Trachytherus in that the ulnar side is largeand articulated with the Mc V, whereas theulnar side of Trachytherus is tapered and thereis little to no unciform–Mc V contact (seefig. 8 A–C). The unciform of Moqueguahippusis similar to that of Eurygenium pacegnum(Shockey, 1997: fig 4b), but not as deep as thatof Rhynchippus equinus (Loomis, 1914: fig.59). The Mt V facet is not as verticallyoriented as that of Rhynchippus, which has avery reduced Mt V.

The only complete metapodial appears to beMt II. It is 56.3 mm long with a proximal endhaving a transverse dimension of 14.6 mm.This proximal region is fairly complex, havingarticular surfaces that presumably overlappedMt III and articulating with the meso- andectocuneiforms. A lateral articulation mayhave served as an articular joint for theendocuneiform or possibly a Mc I.

A couple of distal phalanges were amongthe remains of MUSM 964 (fig. 7D). They arelikely phalanges of the manus, as they aregrossly similar to those of several Tertiarynotoungulates, including the toxodontidAdinotherium, the notohippids Eurygeniumand Rhynchippus, and the mesotheriidTrachytherus. These, like those of Trachy-therus, have a longitudinal distal fissure.

TABLE 3

Measures (mm) of Astragalus of Moqueguahippusglycisma, MUSM 964, from Cerro Mono, Moquegua

Astragalus (proximodistal) 32.7

Astragalus (trochlear width) 17.8

Astragalus (width max) 20.0

Astragalar head (transverse) 20.5

Astragalar head (dorsoplantar) 13.5


Fig. 8. Trachytheriine autopodia. A, Nearly complete right manus of cf. Trachytherus spegazzinianus(MUSM 668); B, Carpal region of right manus of Trachytherus sp. (mid-sized species) (MUSM 963); C, rightmanus (missing digits and trapezoid) of trachytheriine, small indeterminate species, (MUSM 965); D, rightpes (missing digits) cf. Trachytherus spegazzinanus of Moquegua (MUSM 668); E, line drawing ofTrachytherus pes; and F, line drawing of Eutypotherium lehmannnitschei of Laguna Blanca, Chubut,Argentina (drawn from AMNH 14963, cast of a Museo de La Plata specimen).


However, the phalanges of Moqueguahippusdiffer from those mentioned in that the plantersurface is solidly ossified such that the rightand left distal ends are fused to one anotheron the planter side. These phalanges ofMoqueguahippus are also more robust thanthose of Trachytherus.

SUBORDER TYPOTHERIA ZITTEL, 1892

FAMILY MESOTHERIIDAE ALSTON, 1876

Mesotheriids are a distinctive clade ofnotoungulates that have a rodentlike incisivebattery and hypsodont to hypselodont cheekteeth. They were generally sheep-sized animalsand, where known, their postcranial skeletonswere modified for strength, such that theyhave been characterized as digging animals(Shockey et al., 2007).

The monophyletic Mesotheriidae tradition-ally has been divided into the generally oldertrachytheriines, of uncertain monophyly, andthe generally younger, more diverse, andmonophyletic mesotheriines (Cerdeno andMontalvo, 2001; Croft et al., 2004; Flynn etal., 2005).

SUBFAMILY TRACHYTHERIINAE AMEGHINO, 1894

We recognize three distinct taxa of Tra-chytheriinae mesotheriids from Moquegua.Curiously, none are referable to the commonTrachytherus alloxus from the nearby andcontemporaneous Salla beds of Bolivia.

The recognition of three mesotheriid taxa isbased primarily upon the size discontinuitiesamong the postcranial elements, which forconvenience we refer to as the large, midsize,and small trachytheriine. The midsize taxon isrepresented by a nearly complete skull (seeShockey et al., 2006: fig. 2), a detaileddescription of which will be provided with itsformal naming as a new species ofTrachytherus. For now it will suffice to notea few characteristics that exclude it from themonophyletic Mesotheriinae, such as having acomplete upper dentition and root formationof the premolars and M1. The other two taxaare known by postcranial elements, which arevery similar to those of other mesotheriids (seeShockey et al., 2007). Where known,Trachytheriinae postcranials are similar to

those of mesotheriine mesotheriids (Shockeyet al., 2007). However, the fusion of theischium to the sacrum may be a synapomor-phy for the Mesotheriinae, as such occurs inthe two taxa in which it is known(Plesiotypotherium and Mesotherium), but isabsent in Trachytherus alloxus. Such is alsoabsent in the large mesotheriid of Moquegua(see below).

Trachytherus cf. T. spegazzinianusAmeghino, 1889

Figure 8; tables 4 and 5

MATERIAL: MUSM 668, a partial skeletonpreserving much of the limbs, including bothhands and feet, and both radii. Other elementsare less well preserved and include fragmentsof the humerus, axial skeleton, pelvis, tibia,and fibula.

LOCALITY: Eusebio Dıaz and MarioUrbina discovered the partial skeletonMUSM 668 within the upper MoqueguaFormation, on a ridge a half a kilometersouth of the western summit of Cerro Mono(fig. 1: g on the map).

DESCRIPTION: The skeletal material of theCerro Mono mesotheriid is so similar to thatof Trachytherus alloxus from Salla that just abrief description of the new material is needed

TABLE 4

Measures of Postcranial Elements (mm) of cf.Trachytherus spegazzinianus, MUSM 668, from

Cerro Mono, Moquegua

Element Length

Calcaneum (length) 69.0

Tuber calci (midshaft width) 13.1

Calcaneum width (with sus) 26.9

Astragalus (proximodistal) 38.7

Astragalus (trochlear width) 18.8

Astragalus (width max) 31.0

Astragalar head (transverse) 16.3

Astragalar head (dorsoplant) 12.7

Length Width

Mt I 32.7 11.5

Mt II — 10.7

Mt III 62.8 13.0

Mt IV 61.5 11.7

Mt V 54.5 15.0


here. However, until now, no pes of anymesotheriid has ever been described, so weprovide some details of it below. In general,the animal of Cerro Mono differs from T.alloxus in its larger size and more gracilefeatures. Due to its slightly larger size weprovisionally refer it to T. spegazzinianus (seeBillet et al., 2008, for the subtle differencesbetween T. spegazzinianus and T. alloxus).Until the recent naming of T. alloxus Billet etal., 2008, the mesotheriid of Salla had beenreferred to T. spegazzinianus. Thus, referencesregarding our discussion of T. alloxus (e.g.,Sydow, 1988; Shockey et al., 2007) identify thetrachythere of Salla as T. spegazzinianus.

At 170 mm in length, the radius of theCerro Mono mesotheriid is a little longer thanthe largest radius known for T. alloxus fromSalla (Shockey et al., 2007). Aside from beingslightly more gracile than those referred to T.alloxus, it is similar to the Salla specimens ingeneral form, having a wide proximal regionwith a sigmoidal articular surface for thecapitulum of the humerus as well as later-oventral facets for articulation with the ulnaand probably an elbow sesamoid, as occurs inT. alloxus (Shockey et al., 2007), as well as thetoxodontid Nesodon (Scott, 1912: pl. 25.8).The distal radius of MUSM 668 clearly

illustrates four distinct groves for tendons ofthe wrist and digit extensor muscles (fig. 8A).

Both hands are preserved. Although theshaft of the pollex is broken on both right andleft sides, the manus is unambiguously penta-dactyl, as in T. alloxus of Salla (Shockey et al.,2007).

Based on the deep groove for the tendon ofthe flexor hallicis longus on the astragalus ofTrachytherus, Ameghino (1905) predicted thepresence of the great toe (hallux) in theanimal. The pes of MUSM 668 proves himcorrect (fig. 8D, E). Although Mt I is theshortest metatarsal, it is not an insignificantelement. It is over half the length of Mt III–Vand its proximal width is similar to those ofthe remaining metatarsals (table 4). The prox-imal articular surface of Mt I is rather robust,but the entire joint could not be observed sincethe entocuneiform was not preserved. Theother metatarsals (Mt II–V) are subequal inlength, but Mt V is thinner than Mt II–IV. Anarticular facet on the proximolateral surface ofMt II illustrates that there was some articula-tion between Mt I and Mt II. Mt II has alateral process that overlaps Mt III and thedistal portion of the ectocuneiform, giving it asecure joint with these elements. Mt III and IVarticulate with the ectocuneiform and cuboid,

TABLE 5

Comparative Measures (mm) of Astragalus and Metacarpals of Mesotheriids of Moquegua

Taxon Specimen Astragalar length Trochlear width Max width

cf. T. spegazzinianus

(large species) MUSM 668 37.0 16.4 31.5

Trachytherus (midsize) MUSM 961 30.8 14.0 (25.5)

Trachytherus (midsize) MUSM 962 — 13.4 24.5

Trachytherus (midsize) MUSM 966 29.0 13.5 24.3

T.? sp. indet. (small) MUSM 967 (23) 10.0 18.5

Mc lengths Specimen

Mc I

(length)

Mc II

(length)

Mc III

(length)

Mc IV

(length)

Mc V

(length)


(large species) MUSM 668

—

76 75.5 72.9 60.3

T.? sp. indet. (small) MUSM 965 — — 56.5 48.1 —

Mc proximal widths Specimen

Mc I

(width)

Mc II

(width)

Mc III

(width)

Mc IV

(width)

Mc V

(width)


(large species) MUSM 668 10.5 14.1 16.9 16.6 10

Trachytherus (midsize) MUSM 963 — — 13.0 13.6 8.0

T.? sp. indet. (small) MUSM 965 — 10 10.5 11.8 6.2


respectively, at the same level. The articulationbetween Mt III and IV was accomplished by adistinctive spheroid process on the dorsotibialside of Mt IV inserting into a concave facet ofMt III. An additional articulation occursbetween Mt III and Mt IV at the planterregion of the metatarsals. This articulation isflatter than the ball-and-socket articulation atthe dorsal region. An overlapping process onthe proximofibular side of Mt IV provides adorsoplantarly deep receptacle for the prox-imotibial surface of the Mt V. The mostnoteworthy feature of Mt V is a robust lateralprocess that appears to have provided asignificant lever arm for abduction.

All five proximal phalanges were in articu-lation with the metatarsals, however, theirdistal ends were not preserved. Enough ofthese elements are present to illustrate that allwere relatively long, even the first digit (seefig. 8 D, E). No medial or distal phalangeswere in articulation with either pes, but someof the ungual phalanges associated with theskeleton likely belonged to the pes as theywere unlike those associated with the manusand unlike those known for the hand of T.alloxus or Mesotherium (Shockey et al., 2007).Those suspected of being from the pes weremore clawlike (sharp with little dorsoplantarcompression) and lacked the longitudinalfissure observed in the ungual phalanges ofthe manus.

The proximal tarsals of Trachytherus havebeen described in detail elsewhere (Ameghino,1905; Sydow, 1988; Shockey et al, 2007), so wenote here only distinctive features of theastragalus, including asymmetric trochlearridges, a separate and well-developed groovefor the tendon of the digital flexor, themoderately long and constricted astragalarneck, and the subspherical head. The navicu-lar has a deeply concave facet for articulationof the spheroid head of the astragalus. It isbuttressed on the medial side by a proximalprocess, like that of the typotheresHegetotherium and Interatherium (Sinclair,1909) and Prohegetotherium (Shockey andAnaya, 2008).

Whereas the articulation between the as-tragalus and navicular is a ball-and-socketjoint (the astragalar head forming the ‘‘ball’’and the deep concavity of the navicular

forming the ‘‘socket’’), the calcaneal-cuboidjoint forms a sliding articulation. This permit-ted considerable rotation of the middle anklejoint, suggesting some capabilities for inver-sion of the foot.

Trachytherus sp. (medium size)

Figure 8B; table 5

MATERIAL: MUSM 350, skull (damagedbasicranium) and mandibles (Shockey et al.,2006: fig. 2); MUSM 963, left and right partialmanus; and astragali MUSM 961, 962, and966.

LOCALITY: All from the summit of CerroPan de Azucar, near the point where the skulland jaws (MUSM 350) was found (fig. 1: c onthe map).

DESCRIPTION: A variety of postcranial ele-ments referable to Trachytherus were foundalongside the skull (MUSM 350), as well as anm3 of a different individual of Trachytherusthat are referable to this midsize mesotheriid.Most of these elements likely do not representthe same individual as MUSM 350 since theyappear to be from ontogenetically youngerindividuals. We refer the partial manus ofMUSM 963 (fig. 8B), as well as some tarsalsfound nearby, to this unnamed taxon. Asmaller mesothere manus (MUSM 965;fig 8C) may also pertain to this taxon, butwe do not refer it to this taxon since it is sosmall that it likely represents a differentspecies (see below).

The manus of this midsize trachytheriine(fig. 8B) is similar to that of cf. T. spegazzi-nianus from Cerro Mono of Moquegua (seefig. 1: g on map for locality; fig. 8A for themanus) and the manus of T. alloxus from Salla(Shockey et al., 2007; identified there as T.spegazzinianus). We note the unfused distalradius and ulna of MUSM 963, whichindicates that even though it was found inclose proximity to the skull (MUSM 350), itrepresents a different, ontogenetically youngerindividual, whereas the complete eruption ofthe M3 and the significant dental wearindicates that the MUSM 350 is a matureindividual. The manus MUSM 963 is nearlyidentical to those of T. spegazzinianus and thesmall indeterminate species discussed below(fig. 8 A, C), save for its size intermediate


between the two. Also, since neither thetrapezoid nor Mc I were recovered, we cannotassert that the manus of this midsize taxonwas pentadactyl like T. alloxus, cf. T. spegaz-zinianus (fig. 8A), and the small indeterminatespecies, but we note that even the PleistoceneMesotherium had five digits on its manus(Serres, 1867; Ameghino, 1891; Shockey et al.,2007.)

CF. TRACHYTHERIINAE

Small indeterminate species

Figure 8C; table 5

MATERIAL: MUSM 965 right and leftmanus, the right being nearly complete, whilethe left is missing the trapezoid and trapeziumand the metacarpals are fragmentary (fig. 8C);MUSM 966 astragalus.

LOCALITY: Collected in the upper Mo-quegua Formation, at the summit of CerroPan de Azucar, near the skull of the midsizeTrachytherus sp. (MUSM 350) (fig. 1: c on themap).

DESCRIPTION: Fragments of postcranial el-ements of a very small trachytheriine werefound near and among broken remains ofspecimens of the midsize species of Trachy-therus. These may represent small individualsof that taxon or (more likely) may indicate thata third trachytheriinine species was present.These distinct elements do not represent anontogentic difference between the manus ofMUSM 965 and that of MUSM 963 from thesame spot, since both are at the same stage ofdevelopment (fused metacarpals and unfuseddistal radii and ulnae).

The sample size is too small to be conclu-sive, but we note several size discontinuitiesbetween these smallest indeterminate tra-chytheriines, the midsize Trachytherus sp.and cf. T. spegazzinianus (table 5). Post-cranial elements referred to the midsize taxonhave linear dimensions generally 15% tonearly 30% greater than the same regions ofthe small, indeterminate trachytheriine.Skeletal elements referred to T. spegazzinianusare much larger than both this diminutivetrachytheriine and the midsize taxon.

We figure the left manus of this smalltrachytheriine and note its close similarity to

the manus of both the large (cf. T. spegazzi-nianus) and the midsize taxon (fig. 8) as wellas that of T. alloxus (Shockey et al., 2007).These also are very similar to the manus ofthe Pleistocene mesotheriine Mesotherium(Ameghino, 1891; Shockey et al., 2007).

DISCUSSION

AGE OF THE MOQUEGUA LOCALITIES: TheSugarloaf ash provides a high-precision40Ar-39Ar age determination of 26.25 60.10 Ma for the lower part of the upperMoquegua Formation. This is consistent withthe 40K-40Ar ages reported by Tosdal et al.(1981) for stratigraphically higher levels of theupper Moquegua, exposed east of theMoquegua River. Since we recovered fossilswithin 20 m above and about 10 m below thisash at Cerro Pan de Azucar, in the lower partof the upper Moquegua Formation, we acceptthe new high-precision 40Ar-39Ar age as thebest available estimate of the age of theMoquegua Fauna. This places the MoqueguaFauna within the late Oligocene.

Although no paleomagnetic studies havebeen performed for the Moquegua sequences,the age of 26.25 6 0.10 Ma indicates thatthese beds are contemporaneous with fossil-bearing horizons of Salla, Bolivia, which arelocated just 365 km east of the Moquegualocalities, at essentially the same latitude(about S17u109 for Salla and S17u139 forMoquegua). Based on the best-fit composite40Ar-39Ar / paleomagnetic correlation of Kayet al., 1998, the fossil-bearing horizons at Sallarange from sediments believed to be as old aspaleomagnetic chron C10r (28.74–29.40 Ma)to an age less than 25.50 Ma. This interpreta-tion of the ages of the Salla strata suggeststhat the Moquegua fauna correlates with‘‘stratigraphic unit 3’’ in the Calaboza Pataregion of Salla, which have an estimated agerange of 25.66 to 26.55 Ma (Kay et al., 1998).Numerous rodent and notoungulate speci-mens (including Trachytherus alloxus) havebeen recovered from unit 3 of Salla. Unit 3antedates the ‘‘Branisella level’’ (part of unit 5)from which specimens of the oldest knownplatyrrhine primate Branisella have beenrecovered (MacFadden et al., 1985; Takaiand Anaya, 1996; Kay et al., 1998), the only


level from which primates have been recoveredat Salla. Given the ages of both sequences, thefossil-bearing portion of the upper MoqueguaFormation is probably older than the‘‘Branisella level,’’ however, and thus wouldbe older than the first record of primates inSouth America.

Nevertheless, it would be unwise to con-clude much from our failure to recoverprimate fossils at Moquegua, since manyreasonable explanations are possible (e.g.,they are there and we missed collecting them;they once lived there, but were not preservedas fossils, because the paleodepositional envi-ronments were not appropriate; they wereregionally present but locally absent in theMoquegua region, etc.). With the smallsample of fossils from Moquegua, the proba-bility of obtaining rare and small specimens isnot great. Our efforts at dry screening atopCerro Pan de Azucar (at the edge of one of theworld’s driest deserts) resulted in the recoveryof only fragmentary remains of Trachytherusspp., adding nothing new to our faunal list.(The new tiny rodent was recovered by surfaceprospecting.)

As with the mesotheriids of Moquegua andthe notohippid Moqueguahippus, the rodent ofMoquegua is similar to, but distinct from, aspecies known from Salla. Both species ofSallamys are rather small, but S. quispea issmaller and has a relatively (as well asabsolutely) smaller dp4. The dp4 of the twospecies differs also by S. quispea having itsanterolophid continuous on the labial side,whereas that of S. pascuali is continuous onthe lingual side (details in description and seealso fig. 6).

TRACHYTHERIINAE OF MOQUEGUA: In termsof their geologic age and their position asnearest outgroups to the derived NeogeneMesotheriinae, the various taxa of the possiblyparaphyletic assemblage ‘‘Trachytheriinae’’are of considerable interest for phylogeneticstudies. The excellent material of at least threetaxa from Moquegua increases knowledge ofboth the diversity and morphology of tra-chytheriines. The midsize Trachytherus sp. iscomplete enough to provide particularly sig-nificant data on its skull and hand anatomy,while postcranial remains of both a larger (cf.T. spegazzinianus) and very small, unnamed

trachytheriinine suggest that three trachyther-iinine species were present in the MoqueguaFauna. The distinction in size among thesethree taxa is evident in fig. 8 (see also table 5).None of the three Moquegua trachytheriinemesotheriids are referable to T. alloxus, acommon taxon from the nearby, contempora-neous (at least partly) Salla. Nor are theyreferable to T. subandinus, also known fromDeseadan strata from the Departamento deLa Paz, Bolivia. Therefore, a total of fivespecies of trachtheriine mesotheriids werepresent during the late Oligocene in the regionthat is now southern Peru and western Bolivia(fig. 1). Such species richness, within a limitedgeographic area, suggests that the region wasimportant in the radiation of these basalmesotheres, a pattern that has been observedfor mesotheriinine taxa from the Altiplano ofChile as well (Flynn et al., 2002; Croft et al.,2004).

Although the manus of the Pleistocenemesotheriine Mesotherium has been knownfor over 100 years (Serres, 1867; Ameghino,1891), no mesotheriid pes has been describedpreviously. We note, however, a Euty-potherium hind foot cast of a Museo de LaPlata specimen in the AMNH collection(AMNH 14963; fig. 8F). Notes associatedwith the cast indicate that the originalspecimen was collected with a partial denti-tion of Eutypotherium lehmannnitschei fromLaguna Blanca, Argentina (middle Miocene).The casts appear to be of the holotype (MLP12-1701) of E. lehmannnitschei Roth, 1901(personal commun. with D. Croft). The‘‘lemur-like’’ morphology of the foot causedan unnamed cataloger to doubt its referral tothe associated Eutypotherium teeth. Indeed,the primatelike condition of the manus ofMesotherium had inspired Ameghino (1891) tosuggest a close phylogenetic relationshipbetween typotheres and ‘‘prosimians.’’ Ourdiscovery of the pes of Trachytherus, and itssimilarity to that referred to Eutypotherium,removes any doubt about the association ofthat pes with the teeth of Eutypotherium.Inspection of figure 8D–F demonstrates onlytrivial differences between the pes of the lateOligocene trachytheriine Trachytherus andthat of the middle Miocene mesotheriineEutypotherium (AMNH 14963, cast). Likewise,


the manus digit formula of mesotheriids isconservative, with the Pleistocene Meso-therium also retaining the pentadactyl state(compare our fig. 8A with that of Ameghino,1891: fig. 10 or Shockey et al, 2007: fig. 5).

The pes of Trachytherus is remarkablysimilar to that of the extant aardvark(Orycteropus). Both taxa have asymmetrictrochlear ridges of the astragalus with distinc-tive ball-and-socket astragalar-navicular artic-ulation, and both are pentadactyl (althoughthis is clearly retention of a primitive state). Ina multivariate analysis of postcranial elementsof over 30 extant mammals of known loco-motor habits, mesotheriid notoungulatesoccupied a similar morphospace as aard-varks and other ‘‘scratch diggers’’ (sensuHildebrand, 1974, 1985). This indicated thatTrachytherus and Mesotherium shared a suiteof postcranial characteristics distinct fromextant runners, swimmers, and generalists,but like those of extant scratch diggers.Discrete qualitative characters (huge ridgesand tuberosities for muscle insertion, fissuredphalanges, and robust pelvis) also stronglysuggest that mesotheriids were fossorial(Shockey et al., 2007).

ENDEMIC FAUNA OF MOQUEGUA: TheMoquegua Fauna is significant for its endemicspecies. Although the taxonomic diversityrecorded from Moquegua is not vast, it issignificant that there are several new taxa,considering its proximity to the extensivelycollected Salla beds, which our study andprevious geochronological studies indicate arecontemporaneous. For example, hundreds oftrachytheriinine specimens have been collectedfrom Salla (see Billet et al., 2008: appendix 1for a partial list of specimens), with numerousskulls curated in several museums (MNHN-Bol, MNHN-Paris, PU, UF, and UATF).None that we know of, however, are conspe-cific to any of the mesotheriids of Moquegua.Likewise, none of the notohippid speci-mens from Salla are yet referable toMoqueguahippus. Nor are any Salla rodentsreferable to Sallamys quispea, although itappears to be relatively closely related to S.pascuali of Salla. Our inspection of dasypo-dids in the UF and PU collections do notreveal any osteoderms similar to that report-ed here.

Given the close temporal and geographicproximity of the two Deseadan faunas, wefind it a little surprising that none of the fourtaxa from the Moquegua Fauna, that can beidentified to species, are known from Salla (oranywhere else), suggesting that although thisfauna was geographically and temporallyproximate to the Deseadan Salla Fauna,distinctive paleogeographic and paleoenviron-mental conditions probably led to a distinctiveregional biotic differentiation for the Moqueguaarea of coastal Peru.

CONCLUSIONS

This more comprehensive study of thefossil-bearing horizons of the lower portionof the upper Moquegua Formation confirmsour initial assessment that the fossils are of alate Oligocene (Deseadan SALMA) age andremoves any support for the suggestion of apossible early Miocene age for these beds(Shockey et al., 2006). This late Oligocene ageis supported by a new 40Ar-39Ar age determi-nation for the Sugarloaf ash (26.25 60.10 Ma) and by the many taxonomic simi-larities of the Moquegua fossils to those ofother Deseadan localities. This similarity,however, is only superficial, as we found thatnone of the taxa that can be identified tospecies are referable to species described fromother Deseadan faunas, not even the nearbyand species-rich Salla beds. This differencecannot be attributed to age differences, sincethe Moquegua fauna is contemporaneous withat least part of the Salla fauna, with theextended depositional interval of Salla strataalso having preserved fossils that are bothyounger and older than those from Moquegua(the ages of various fossil-bearing levels atSalla range from approximately 29 to 25 Ma(Kay et al., 1998).

Trachytheriine mesotheriid notoungulateswere an important component duringDeseadan time at both Moquegua and incontemporaneous deposits in nearby parts ofBolivia, as indicated by the presence of threecoeval taxa at Moquegua and two othertrachytheriines in Bolivia (T. alloxus and T.subandinus; T. spegazzinianus is also known atLacayani, Bolivia [Billet et al., 2008]). We findthis extremely high species richness (at least


five contemporaneous species) to be remark-able for such a small area.

ACKNOWLEDGMENTS

We are grateful to the National GeographicSociety for their generous support for thisproject (Research and Exploration grant 7507-03 to BJS), to l’Institut Francais d’EtudesAndines (IFEA) for the use of their vehicleduring our initial exploration of Moquegua,and to the U.S. National Science Foundationfor support of A. Jeong and J. Flynn (DEBDEB-0513476). R. Quispe, her instructor (J.Acosta), and classmates (A. Flores, A. Pino,and N. Jarica) of the Universidad Nacional‘‘Jorge Basadre Grohmann,’’ Tacna, Peru,made the initial discovery of fossils in theUpper Moquegua Formation. Tireless andcheerful comrades in the field included R.Quispe, A. Flores, and A. Pino of theUniversidad Nacional ‘‘Jorge BasadreGrohmann,’’ as well as E. Dıaz, J. TejadaLara, M. Urbino, W. Aguirre, and our latefriend, G. Ramirez, of Museo de HistoriaNatural, Lima, as well as E. Sargis of Yale.F. Pujos, E. Bostelmann, and V. Pachecohelped our thoughts and discussion of thearmadillo specimen. W. Joyce and D.Brinkman, of the Yale Peabody Museum,and R. Hulbert and B. J. MacFadden, of theUniversity of Florida, provided access tocomparative specimens. A. Wyss, of UCSB,and D. Croft, of Case Western ReserveUniversity, provided thoughtful and detailedcritiques of our original manuscript. We alsothank M. Arnal of the Museo Argentino deCiencias Naturales, Buenos Aires, and M. E.Peres of the Museo Paleontologico ‘‘EgidioFeruglio,’’ Trelew, Argentina, for help withrodent dental terminology. E. Griffith and B.Rudolf of the AMNH provided much appre-ciated instruction to A.J. regarding the use ofthe SEM.

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Paleontology and Geochronology of the Deseadan (late