Marsupial Radiations Downloaded

Zoological Journal of the Linnean Society, 2009, 155, 867-884. With 7 figures

Earliest South American paucituberculatans and their significance in the understanding of ‘pseudodiprotodont’ marsupial radiations Downloaded

FRANCISCO J. GOIN1*, ADRIANA M. CANDELA1, M. ALEJANDRA ABELLO1 and EDISON V. OLIVEIRA2

from ^División Paleontología Vertebrados, Museo de La Plata, Paseo del Bosque sin, 1900 La Piata,

Argentina https://academic.oup.eom/zoollnnean/article-abstract/155/J 2Pontificia Universidade Católica do Rio Grande do Sul, PUCRS, Campus II, CEP 97500-970, Uruguaiana, RS, Brazil

Received 14 March 2008; accepted for publication 15 April 2008

We describe the oldest Paucituberculata marsupials, from the La Barda and Las Flores localities (Argentina; Late Palaeocene, and Early-Middle Eocene), as well as from the Itaborai Basin (Brazil; Late Palaeocene). The new taxa are represented by very scarce, although well-preserved, dental remains. A parsimony analysis was performed in order to evaluate the phylogenetic affinities of these taxa. Representatives of both Riolestes capricomicus gen. et sp. nov. and Bardalestes hunco gen. et sp. nov. appear to be basal paucituberculatans, and their molar features give clues on the early evolution of the representatives of this order. Within the Paucituberculata we recognize two major clades: Caenolestoidea and Palaeothentoidea. We conclude that ‘pseudodiprotodont’marsupials of the traditional literature (i.e. Polydolopimorphia + Paucituberculata) do not form a natural group. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155, 867-884.

ADDITIONAL KEYWORDS: Argentina - Brazil - Caenolestidae - molar morphology - Paleogene.

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INTRODUCTION The antiquity of the Paucituberculata depends by

largely on the extent and content of this order as Living paucituberculatans (Mammalia, Marsupialia) guest proposed by different authors. According to their cri are restricted to the caenolestid genera, Caenolestes,

teria, no indisputable records of Palaeocene Paucitu on Lestoros, and Rhyncholestes. However, the rich evolu

berculata have existed until now. In this paper we 23 tionary history of the Paucituberculata includes a

describe the oldest Paucituberculata yet found, Sepiembe diverse array of extinct taxa, some of them remark coming from the Middle Chubut River Volcanic- ably derived (Marshall, 1980). The concept and rela Pyroclastic Complex (Argentina; Early-Middle tionships of the Paucituberculata are of particular Eocene), the Las Flores Formation (Argentina; Itabo-

interest as its living representatives have been 20 raian Age, Late Palaeocene), and the Itaborai Basin included in many phylogenetic analyses of marsupial

(Brazil; Itaboraian Age, Late Palaeocene). The new ■ relationships in recent years (see, e.g. Kirsch, taxa are represented by a few isolated remains, Lapointe & Springer, 1997; Jansa & Voss, 2000; mostly consisting of upper and lower molars; notwith Sanchez-Villagra, 2001; Horovitz & Sanchez-Villagra, standing, their good preservation sheds light on the 2003, 2007; Asher, Horovitz & Sanchez-Villagra, early evolution of the representatives of this order. 2004; Baker et al., 2004; Cardillo et al., 2004; Phillips Furthermore, the dental information derived from et al., 2006; Ladeveze & de Muizon, 2007). these new taxa provides new evidence on the very concept of Paucituberculata. We describe the new ’Corresponding author. taxa and assess their phylogenetic relationships E-mail: [email protected] in the context of South American marsupials.

MATERIAL AND METHODS Eocene to earliest Middle Eocene age (Ypresian- Provenance of the studied specimens Lutetian boundary) for the mammal-bearing sedi ments (Tejedor etal., 2005; in press). New specimens were recovered from the Late Palae- Originally correlated with Banco Negro Inferior ocene and Early-Middle Eocene sites of La Barda and levels (Marshallet al., 1981), the Las Flores Formation Las Flores (Argentina), and from Late Palaeocene (Legarreta & Uliana, 1994; Fig. 1) was later referred to levels of Itaborai (Brazil). the Rio Chico Group by Bond et al. (1995). Its type The La Barda locality is a recently discovered fos- locality is exposed at the ‘Yacimiento Las Flores’, an siliferous site located near the town of Paso del Sapo

oil-bearing field on the eastern slopes of the Southern Downloaded in north-western Chubut Province, Argentina (Fig. 1). Cliff of Lake Colhue Huapi (Sarmiento Department, The La Barda sediments consist of consolidated tuffs Chubut Province, Argentina). The extremely rich intercalated in the Volcanic-Pyroclastic Complex of diversity of marsupials recovered from these levels the Middle Rio Chubut. This Palaeocene-Eocene suc

(Bond etal., 1995) are presently being described (a from cession was reviewed by Aragón & Mazzoni (1997); preliminary note on this diversity was presented in

previous studies of the regional geology, stratigraphy, https//academic.oup.com/zoolinnean/article-abstract/155/4/867/2622985 Goin, Candela & Forasiepi, 1997). These marsupials geochemistry, petrogenesis, and palaeobotany were show substantial identity with those of Itaborai at the made by Petersen (1946), Archangelsky (1974), generic level, thus confirming their Itaboraian (Late Volkheimer & Lage (1981); Lage (1982); Aragón & Palaeocene) age (Oliveira & Goin, 2006). Romero (1984); Mazzoni & Aragón (1985); Aragón, The local fauna of Sao José de Itaborai (State of Mazzoni & Merodio (1987); Rapela et al. (1988); Niteroi, south-eastern Brazil; Fig. 1), conventionally Mazzoni, Aragón & Merodio (1989); and Wilf et al. assigned to the Late Palaeocene of South America (2003). This complex includes a variety of volcaniclas- (Marshall, 1985), shows a unique diversity of tic, intrusive, pyroclastic, and effusive rocks deposited metatherians and several ‘ungulates’, as well as the over several million years. Absolute datings of the oldest known Xenarthra (Bergqvist, 1996; Oliveira, over- and underlying rocks, stratigraphical relation 1998). Although the proposal of an Itaboraian Land ships, and faunal content suggest a latest Early mammal Age has been a subject of controversy (e.g. Bonaparte, Van Valen & Kramartz, 1993), more recent studies on the stratigraphy and faunal content of the contemporary Las Flores Formation (central Patagonia, Argentina) supports its validity and use as biochronological reference (Bond etal., 1995). The fossil marsupials of Sao José de Itaborai comprise a great variety of specimens, most of them of small size, which were successively described by Simpson (1947); de Paula Couto (1952a, b, 1961, 1962, 1970); Marshall (1982a, b, 1984, 1987); Marshall & de

Muizon (1984); Oliveira (1998); and Ladevéze (2004, by

2007). Their diversity includes most major lineages guest of South American marsupials, such as microbiothe-

rians, didelphimorphians, polydolopimorphians, and on

sparassodonts. 23

September

Cladistic analyses The dataset (Supporting Information Appendix SI)

included 43 characters (Supporting Information 2019 Appendix S2) and 24 taxa pertaining to different clades of marsupials (see Taxon sample). The multi state characters were treated as unordered. The data set was analysed by performing a heuristic search with parsimony under equal weights with TNT 1.1 (Goloboff, Farris & Nixon, 2003). The shortest trees were found by generating 500 Wagner trees, and then submitting them to the tree bisection-reconnection Figure 1. Map of South America indicating localities branch-swapping method, retaining ten trees per cited in the text. replication. State transformations were considered

© 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155, 867-884 NEW PAUCITUBERCULATANS MARSUPIALS 869 synapomorphies for a given node only if they were unambiguous. Unambiguous character state optimi zations and matrix and tree editions were obtained with the program WINCLADA (Nixon, 1999). Relative and absolute Bremer support (Goloboff & Farris, 2001) were calculated in order to assess clade support using TNT (Goloboff et al., 2003) and performing heuristic searches. Downloaded Taxon sample In order to establish the closer phylogenetic relation ships of the new taxa described herein, Bardalestes

hunco gen. et sp. nov. and Riolestes capricornicus gen. from et sp. nov. (see below and Figs 2, 3), genera of the main lineages of South American Metatheria were included https://academic.oup.eom/zoollnnean/article-abstract/155/4/867/2622985 in these analyses. Within Didelphimorphia the genus Pucadelphys (Fig. 4D) was selected (Marshall & de Muizon, 1995, but see Rougier, Wible & Novacek, 2004). Derorhynchus (Fig. 4E) is an ‘opossum-like’ marsupial whose affinities are still being discussed (see de Paula Couto, 1952a; Goin, Oliveira & Candela, 1998a; Goin, 2003). The extant Pacituberculata Rhyncholestes and Cae- nolestes, and the extinct Stilotherium (Fig. 5E), Plio- lestes, Plionocdromus (Fig. 5C, D), and Pichipilus (Fig. 5A, B) were selected as representatives of the ‘Caenolestidae’ (sensu Marshall, Case & Woodburne, 1990). Palaeothentes and Acdestis were selected as representatives of the Palaeothentidae, and Parab- derites and Abderites as Abderitidae. Within Microbiotheria Microbiotherium (Fig. 4G, H) was selected. Glasbius (Fig. 4F) was included as a basal polydolopimorphian (Goin, etal., 1998b; Goin & Candela, 2004). Prepidolops (Prepidolopidae; Fig. 6A), Bonapartherium (Fig. 6B, C, F) Epidolops (Bonapartheriidae), Polydolops (Polydolopidae),

Roberthoffstetteria (fam. indet.; see Goin, Candela & by

de Muizon, 2003), Proargyrolagus (Argyrolagidae; guest Sánchez-Villagra & Kay, 1997), and Klohnia (Argyro- Figure 2. A, B, Bardalestes hunco gen. et sp. nov.,

lagoidea, fam. indet.; Flynn & Wyss, 1999) were on specimen LIEB-PV 1135 (detail), left M2-3 (A, occlusal

selected as representatives of Polydolopimorphia 23 view; B, occlusal-lingual view). C-F, Bardalestes sp. C, D,

{sensu Goin & Candela, 2004). Specimens referable to September Klohnia studied in this work (Fig. 6D, E) include a set specimen MLP 90-II-5-336, an isolated upper molar (M?2) lacking the metastylar area (C, occlusal view; D, anterior of numerous, unpublished specimens exhumed at view). The dashed line indicates the inferred profile of the Early Oligocene levels in Gran Barranca, Chubut

paracone; E, F specimen MLP 90-II-5-300, an isolated Province. In short, with the only exception of 20

right molar lacking most of the trigonid (E, lingual, and i the carnivorous Sparassodonta, all major lineages 9 F, occlusal views). (orders) of South American metatherians were repre sented in this analysis. To assess the polarity of characters, Alphadon (Fig. 4A-C) was taken as the en Evolución y Biodiversidad, Sede Esquel, Univer root as this taxon is currently considered as a gen sidad Nacional de la Patagonia (Esquel); MCN-PV: eralized Metatheria (Marshall etal., 1990). Colendo de Paleovertebrados, Museu de Ciéncias Naturais, Fundacao Zoobotànica do Rio Grande do Abbreviations Sul (Porto Alegre); MLP, Departamento Paleontología CHU, Instituí des Sciences de 1'Evolution, USTL Vertebrados, Museo de Ciencias Naturales de La (Montpellier); LIEB, Laboratorio de Investigaciones Plata (La Plata); MMP: Museo Municipal de Ciencias

Fiscales de Bolivia, in Centro de Tecnologia Petrolera (Santa Cruz). SALMA, South American Land- Mammal Age. The generalized metatherian dental formula is assumed to be: I/i 5/4, C/c 1/1, P/p 3/3, M/m 4/4. Molar nomenclature follows Goin et al. (2003).

SYSTEMATIC PALAEONTOLOGY Supercohort Marsupialia Illiger, 1811

Order Paucituberculata Ameghino, 1894 Downloaded Plesion Bardalestes gen. NOV. Diagnosis: Differs from all other paucituberculatans

in that the upper molars lack an enlarged, ‘hypocone from like’, metaconule; the paracone is less reduced; the

Figure 3. Riolestes capricomicus gen. et sp. nov. paracone and the metacone are less twinned to StB https://academic.oup.eom/zoolinnean/article-abstract/155/4/867/2622985 Occlusal view of specimen MCN-PV 1790, an isolated ml. and StC + StD, respectively; StB much larger than StC + StD; distal end of entocristid in ml-3 relatively high. Naturales (Mar del Plata); MNRJ: Museu Nacional (Rio de Janeiro); PVL: Colección Paleozoologia Verte Etymology: Barda, from La Barda locality, where the brados, Instituto Miguel Lillo (Tucumán); YPFB Pal, type specimen of the type species of the genus was Colección de Paleontología, Yacimientos Petrolíferos collected; -lestes, Latin for ‘thief’, ‘pirate’ and, by

guest

Sepiembe

Figure 4. A-C, Alphadon sp. A, B, specimen MLP 87-1-4-31, right Mx in occlusal (A) and anterior (B) views. C, specimen AMNH 116632 (detail) showing the talonid of ml and complete m2-3, occlusal-labial view. D, Pucadelphys andinus; specimen YPFB Pal 6472 (detail, cast) showing right M2-4, occlusal view. E, Derorhynchus sp., specimen MNRJ 2506-V (cast), left M2-3 in occlusal view. F, Glasbius intricatus, specimen UM VP 1593 (cast), right P3-M3 in occlusal view. G, H, Microbiotherium tehuelchunv, G, specimen MLP 58-IX-3-4, left M2-3 in occlusal view; H, specimen MLP 11-35, left ml-3 in occlusal view.

extension, ‘carnivorous’ flestikos'), a term that charac terizes the generic name of several fossil and living Paucituberculata.

Type species: Bardalestes hunco sp. nov.

Distribution: Late Palaeocene and Early-Middle Eocene, South America. Downloaded

Bardalestes hunco sp. nov. (Fig. 2A, B)

from Type: LIEB-PV 1135 (Fig. 2A, B), a fragment of left

maxillary with M2-3, and roots and part of the crown https://academic.oup.eom/zoolinnean/article-abstract/155/0867/ of M4.

Hypodigm: The type only.

Locality, horizon and age: La Barda, Paso del Sapo (Chubut Province, Argentina). Andesitas Huancache Formation, Early-Middle Eocene.

Measurements: See Table 1.

Diagnosis: Differs from all other paucituberculatans in that the upper molars lack an enlarged, ‘hypocone like’, metaconule; the paracone is less reduced; the paracone and the metacone are less twinned to StB and StC + StD, respectively; StB much larger than StC + StD.

Description (Fig. 2A, B): The M2 and M3 of the type

specimen are very similar to each other, the M3 being '622985 E longer and wider than the M2. Although its crown is badly broken, it can be seen that the M4 (not shown

Figure 5. A, B, Pichipilus sp.; A, specimen MLP 77-VI- in Fig. 2) was very short and narrow, and two-rooted. by

13-15, right m2-3 in occlusal-labial view; B, specimen Its width is approximately half the width of M3. The guest MPEF-PV 4804, right M2 in occlusal view. C, D, protocone of M2 is comparatively wider than that of

Plionocdromus sp., specimen MPEF-PV 4810, right M3 (C, M3. In both molars the anterobasal cingulum is on anterior-labial; D, occlusal-lingual views). E, Stilotherium narrow and lingually connected with the prepara- 23

MACN 8464 (part), right ml-2 in occlusal view. Septembe dissimile', conular crest. The trigon is ample and transversely long; in the M2 the metacone is somewhat higher than the paracone, whereas in the M3 both cusps are

subequal in height. In both molars the protocone is 20:9

Table 1. Dental measurement of Bardalestes hunco gen. et sp. nov., Bardalestessp., and Riolestes capricomicus gen. et sp. nov. Measurements are in mm

Taxon Specimen LM2 WM2 LM3 WM3 Lml Wml Lmx

Bardalestes hunco LIEB-PV 1135 1.42 1.68 1.41 1.78 Bardalestes sp. MLP 90-II-5-336 1.51 1.89 Dracolestes sp. MLP 90-II-5-300 1.05 Riolestes capricomicus MCN-PV 1790 3.79 2.36

from

https://academic.oup.eom/zoolinnean/article-abstract/155/4/867/2622985

Figure 6. A, Prepidolops didelphoides; MLP 81-XI-15-1, right P3-M2 in occlusal view; B, C, F, Bonapartherium liinakusijunv, B, MMP 1408, detail of left Ml-4 in occlusal view; C, F, specimen PVL 4018; C, detail of left dentary showing p3-m2 in labial view; F, detail of right dentary showing the m3 in occlusal view. D, E, Klohnia sp.; D, MPEF-PV 4291, left mx in occlusal view; E, MPEF-PV 4292, right Mx in occlusal view.

slightly eccentric, as in the upper molar here referred even if it is slightly posteriorly shifted in comparison guest to Bardalestes sp. (see below), it is not in line with the with other South American marsupials. The cusp

tips of the StB and the paracone. StA is small and immediately posterior to StB is much smaller and on

very low, StB is comparatively enormous, suboval in occupies an intermediate position between the StC 23

section and connected by means of a crest to the and StD of other more generalized marsupials. Thus, Sepfember immediately posterior cusp (StC + STD; see below). it raises the question of the homology of this cusp in This latter cusp is much smaller and lower than the Bardalestes. Derorhynchid ‘didelphimorphians’ show StB and is even more reduced and close to StB in the some features that ‘anticipate’ the molar pattern of

M3 than it is in the M2. The postmetacrista is longer Paucituberculata: large (although not proportionally 0 2 1 than the preparacrista and is orientated parallel to huge) StB, a deeply V-shaped centrocrista, winged 9 the postparacrista. The apex of the centrocrista is metaconule that is larger than the paraconule, and deep and reaches externally the anterolingual slope molars with a salient hypoconid and, in some cases, of StC + StD. In both the M2 and M3 the metaconule a slightly labiolingually compressed entoconid. The is larger than the paraconule. morphology of the stylar area of the representatives of this family is worth analysing. In this respect, Comments: One of the most striking features of the some indeterminate Derorhynchidae from Itaborai upper molars of Bardalestes liunco is the morphol are suggestive: specimen MNRJ 2506-V exhibits, ogy, position, and relative size of StB. This cusp is especially in the Ml, some proximity of the paracone very large, high and is clearly facing the paracone, to the StB, no reduction of the latter cusp and the

© 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155, 867-884 NEW PAUCITUBERCULATANS MARSUPIALS 873 reduction of the StC and StD, especially the latter. Formation, Rio Chico Group; Late Palaeocene The same features can be seen in the indeterminate (Itaboraian Age). Derorhynchidae specimens MNRJ 2352-V and MNRJ-V 2894-V, DGM 813-M, and MNRJ 2894-V, all Measurements: See Table 1. from the Itaborai Basin. A morphological pattern similar to that occurring in the stylar region of Description (Fig. 2C, D): Even though broken and Bardalestes can be even more clearly appreciated in mostly missing the metastylar area, it is evident that the derorhynchid Pauladelphys, from the Middle MLP 90-II-5-336 is a wide molar (i.e. its labio-lingual

Eocene of Antarctica and Early Eocene of Paso del diameter is larger than the mesio-distal one). The Downloaded Sapo (Goin, Tejedor & Abello, 2000, 2001). In the trigon basin is labio-lingually wide because of the only known upper molar of Pauladelphys juanjoi deep centrocrista. The protocone is moderately devel (MLP 96-1-5-45), an isolated left Ml, a manifest oped; its tip is relatively centrally placed, that is, it is

closeness between the reduced StC and StD is not aligned in a transverse axis with StB and the from observed, so that the latter cusp is relatively distant paracone. The preprotocrista is not symmetrical to from the metastylar corner of the tooth. The same the postprotocrista as the metaconule, larger than the https://academic.oup.com/zoolinnean/article-abstract/155 condition is seen in upper molars referable to Paula paraconule, is posteriorly salient. Both the paracone delphys sp. from Eocene levels of Paso del Sapo and the metacone are worn down almost to their (Tejedor et al., in press). In some of these specimens bases; from their respective sections it can be inferred (e.g. LIEB-PV 1116, LIEB-PV 1114), StC and StD are that the paracone was only slightly smaller than the almost subequal and twinned, so that their bases are metacone. The preparacrista is subequal in length to fused. This pattern suggests that the cusp posterior the postparacrista and the premetacrista; it is almost to the StB of the Bardalestes specimens studied here transversally orientated with respect to the dental may have been the result of the fusion of the stylar axis. The postparacrista and the premetacrista are cusps StC and StD. The subsequent evolution of this subequal in length; they are not symmetrical to each cusp in the more derived Paucituberculata may have other but instead the premetacrista is slightly more involved an increase in size and its setting apart transverse to the dental axis. The postmetacrista has from the StD. Interestingly, in caenolestids such as preserved only its proximal end which is parallel to Stilotherium dissimile, the stylar cusp posterior to the postparacrista; its preserved portion suggests the StB (which we homologize here with StC + StD) that it was moderately developed. The paraconule is maintains its relative size in the upper molar series: half the size of the metaconule; both cusps are it is larger than the StB in the Ml, subequal to StB ‘winged’, i.e. they have pre- and postconular cristae. in the M2, and smaller and closer to the StB in the The preparaconular crest continues labially in the

M3. Even though no Mis are known among the anterobasal cingulum; the postparaconular crest is o867/2622985 Bardalestes specimens described here, it can be seen reduced or absent; in turn, and even though worn, the that in the M3 of this taxon the StC + StD is smaller premetaconular crest seems to have been longer and and closer to the StB than in the M2. more subhorizontal than the postmetaconular one,

In brief, from the assemblage of Paleogene South which descends abruptly downwards and posterolabi- by

American ‘opossum-like’ marsupials, the upper molar ally. The stylar shelf is moderately developed and is guest pattern that occurs in the derorhynchid Pauladelphys deeply penetrated by the centrocrista at its central

may be an indication of the process underwent by the portion. The ectoflexus is almost undistinguishable; on

earliest paucituberculatans. In the particular case of StB and StC + StD are very close together and have 23

the stylar area, the small cusp posterior to the StB no labial emargination. A tiny cuspule which is very Sep:embe seems not to be either the StC or the StD but rather low and subcircular in section can be observed behind the result of the fusion of both cusps. the labial apex of the centrocrista. This cuspule is not located near the labial face of the tooth, as are other

stylar cusps, but instead it is internally placed on the 20'9 Bardalestes sp. (Fig. 2C-F) stylar shelf. The most conspicuous feature of the Referred specimens: MLP 90-II-5-336, an isolated remaining stylar cusps is the very large size of StB, upper molar (M?2; Fig. 2C, D) lacking the metastylar which occupies most of the anterior half of the stylar area; MLP 90-II-5-335, an isolated left protocone; shelf. StB is not only large but also very high; it is MLP 90-II-5-337, an isolated right protocone; MLP suboval in section, as it is slightly labiolingually com 90-II-5-300 (Fig. 2E, F), an isolated right talonid. pressed. Its labial and lingual slopes are steep; ante riorly it has a rounded edge, whereas the posterior Locality, horizon and age: Easternmost part of the one is crest-shaped, trenchant in aspect. The meta Southern Cliff of Colhue Huapi lake, Sarmiento stylar area is broken behind StC + StD. At the lingual Department, Chubut Province, Argentina. Las Flores slope of StB a minute wrinkle can be observed, just

© 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155, 867-884 874 F. J. GOIN ET AL. posterior to the labial end of the preparacrista. Com 5-335 and MLP 90-II-5-337 are almost identical in pared to other ‘opossum-like’ marsupials, it is evident size and morphology. In turn, specimen MLP 90-II-5- that the lingual slope of StB and the labial slope of 300, an isolated lower molar fragment, matches in the paracone in Bardalestes are very close to each size and shape the expected pattern for an occlusal other relative to the total width of the upper molar antagonist to the type specimen. In short, their size, (see the reconstruction of the paracone in Fig. 2D). morphology, and inferred occlusal relationships The anterolabial corner of the tooth, poorly preserved, concur in assigning all specimens to the same taxon. is rather small; a moderately developed but very low The size and morphology of specimen LIEB-PV

StA can be inferred from it. The anterior cingulum is 1135, type of Bardalestes hunco, are very similar to Downloaded poorly developed. those of specimen MLP 90-II-5-336. The greatest dif Three additional specimens are also referred to ferences between the latter and LIEB-PV 1135 are Bardalestes sp. Two of them (MLP 90-II-5-335 and the following: StC + StD larger in the latter, which in

MLP 90-II-5-337) consist of isolated protocones, one addition lacks the cuspule posterior to the centroc from left and the other right; they are roughly similar, in rista apex, and, especially in M2, more posteriorly size and morphology, to the protocone of the already located with respect to the StB. Regarding their size, https://academic.oup.eom/zoolinnean/article-abstract/155/4'86 described upper molar. The third specimen (MLP specimen MLP 90-II-5-336 is slightly larger than 90-II-5-300; Fig. 2E, F) consists of a fragmentary right LIEB-PV 1135. In all other features, the M3 of molar preserving the talonid and part of the posterior LIEB-PV 1135 is indistinguishable from specimen wall of the trigonid. Judging from the preserved MLP 90-II-5-336, for which reason we assume the portion of the metacristid, the trigonid was much latter to be an M3 as well. The finding of new mate higher than the talonid. The latter has a salient rial could prove that the small differences between hypoconid, a small, laterally compressed entoconid, them fall within the variability range of a single and a reduced hypoconulid located posterior to the species, as the greatest difference is the increased size entoconid; the talonid basin is relatively deep; the of the cusp posterior to the StB (which we consider cristid obliqua ends anteriorly near the labial base of homologous to the fusion of cusps StC+ StD). the protoconid; the distal end of the entocristid in ml-3 is relatively high (Fig. 2F). There is a short Riolestes GEN. NOV. postcingulum at the posterior face of the talonid; the posthypocristid is almost transverse to the dental axis. Diagnosis: As for the type and only known species. One additional specimen can also be also referred to Bardalestes sp.: MLP 90-II-5-332. This specimen Etymology: Rio- for the state of Rio de Janeiro, Brazil, consists of an isolated talonid belonging to a mx. Its where are located the fossiliferous outcrops of the morphology resembles that of MLP 90-II-5-300. The Itaboraf Basin; -lestes, Latin for ‘thief’, ‘pirate’ and, by specimen was polished in order to examine its enamel extension, ‘carnivorous’ {lestikos'), a term that charac '2622 structure (specimen KOE 2991; Koenigswald & Goin, terizes the generic name of several fossil and living

Paucituberculata. 2000). As in the upper and lower molars of the Cae- 485

nolestidae, the enamel in Bardalestes shows prisms by

that are orientated more or less straight between the Type species: Riolestes capricornicus sp. nov. guest enamel-dentine joint and the outer enamel surface. A

Distribution: Late Palaeocene, South America.

thick interprismatic matrix orientated at an angle on

with the prisms could be observed. This pattern is 23

common among other generalized ‘opossum-like’ Sepiembe Riolestes capricornicus sp. nov. (Fig. 3) marsupials (Koenigswald & Goin, 2000: 149). Etymology: In reference to the geographic placement Comments: Among the ‘opposum-like’ marsupials of the fossil locality, near the Southern Tropic of

collected from the Las Flores Formation, represented Capricorn. 20 1 by more than 700 isolated teeth, there are a few taxa 9 of very small size. The specimens here assigned to Locality, horizon, and age: Sao José de Itaboraf, State Bardalestes sp. are among the smallest of them. of Rio de Janeiro, Brazil (22°44'51"S, 42°51'21"W); Specimen MLP 90-II-5-300 has the hypoconulid Itaboraf Basin, Late Palaeocene (Itaboraian Age). twinned to the entoconid, a synapomorphy of Late Cretaceous and younger marsupials (Kielan- Type: MCN-PV 1790 (Fig. 3), an isolated ml. Jaworowska, Cifelli & Luo, 2004). In addition, the laterally expanded hypoconid, and the labio-lingually Hypodigm: The type only. compressed entoconid are features diagnostic of the Paucituberculata (see below). Specimens MLP 90-11- Measurements: See Table 1.

Diagnosis: Differs from the remaining Paucitubercu- only in the ml but also in the dp3s of several dif lata in the following combination of characters: large ferent lineages, including some very generalized size, ml with reduced paraconid, mesially placed; forms such as Alpliadon. Cifelli (1994), referring to persistence of the paracristid notch, vestigial anter- several deciduous molars tentatively referred to obasal cingulum, trigonid basin absent; metaconid Alpliadon perexiguus, pointed out that ‘. . . the trigo well displaced posteriorly. nid is broadly open lingually, with the paraconid and metaconid more anteriorly and posteriorly Description: The most distinctive features of this placed, respectively, than on the permanent molars.

molar are its proportionally large size, reduced para The paraconid and metaconid are weakly developed Downloaded conid, high protoconid, backwardly placed metaconid, (. . .) As usual among marsupial dP3s, the cristid absent trigonid basin, labially salient hypoconid (i.e. obliqua extends anterolingually as a crest to the tip laterally expanded), and wide talonid basin. The of the metaconid, resembling the distal metacristid

paraconid is poorly developed, much less than the (...) seen in permanent molars of primitive Tri- from metaconid; its anterior face is flat. The anterobasal bosphenida’ (Cifelli, 1994: 124; Cifelli & de Muizon, cingulum, although vestigial, runs at a short dis 1998). The posterior placement of the metaconid https://academic.oup.com/zoolinnean/article-abstract/155 tance below and labial to the paraconid. The meta with respect to the protoconid is also verified in the conid is moderately developed and is set close to the permanent molars of some Early Palaeocene South protoconid but quite posterior to it. Thus, the metac- American taxa, such as the polydolopimorphian Rob- ristid (postprotocristid + postmetacristid) is short, erthofftetteria nationalgeographica. Among the most high, and in occlusal view is obliquely placed with primitive Sparassodonta, such as some Hathliacyn- respect to the dental axis. The paracristid (prepro- idae, the reduction of the metaconid in ml occurs tocristid + postparacristid) is sharp, trenchant, and together with its posterior placement in the trigo runs steeply downwards, almost subvertical, from nid. In some Microbiotheriidae, such as Pachybio- the protoconid to the paraconid. The paracristid therium acclinum, Eomicrobiotherium gaudry, notch is placed just posterior to the paraconid. The and Microbiotherium gallegosense, the posteriorly talonid is much wider than the trigonid; its basin is ‘shifted’ metaconid in ml occurs together with the well bound by the pre-entocristid, the cristid oblique, mesial ‘shift’ of the paraconid, as in Riolestes. Some and the posthypocristid. The hypoconid and the early Didelphimorphia, such as Itaboraidelphys entoconid are subequal in height, the latter being camposi, also show a slight posterior displacement laterally compressed; the hypoconulid is located of the metaconid. Finally, among the Paucitubercu posterolingually relative to the entoconid, and is lata Caenolestidae and, especially, Palaeothentidae, projected backwards. The cristid obliqua reaches the ml metaconid also shows a displacement similar

J anteriorly up to a point below the notch of the to that of Riolestes. In short, the posterior displace '867/2622985 metacristid; it is not parallel to the labial face of the ment of the metaconid is not exclusive to the mar tooth but instead narrows the talonid basin anteri supial dp3 but also occurs in several permanent orly. There is no postcingulum. Below the crown, the molars in various lineages, noticeably in the ml of

anterior root is smaller than the posterior one. The most Paucituberculata. Luckett & Hong (2000) dem by

cristid obliqua is worn on its anterodorsal edge, as onstrated that the dp3 is vestigial and extremely guest well as the posthypocristid near the hypoconulid reduced in paucituberculatans, which is obviously

and the entoconid at its labial face. not the case in MCN-PV 1790. Finally, the positions on

and relative sizes of the trigonid cusps in Riolestes 23

Comments: Riolestes capricornicus can be considered capricornicus match well those of the ml of September a marsupial on the basis of the pairing of the ento paucituberculatans. conid and the hypoconulid. Its most distinctive fea Riolestes capricornicus and Bardalestes sp. from tures agree well with those expected for a member of Las Flores are contemporary paucituberculatans. Dif the Paucituberculata: labially projected hypoconid ferences between them include the following features: 20

i and laterally compressed entoconid (see below). Riolestes capricornicus triples Bardalestes sp. in size; 9 An additional feature, the metaconid clearly posterior its type specimen differs from the lower molar to the protoconid, occurs in the first molar in referred to Bardalestes sp. in that there is a less most Paucituberculata - except in Stilotlierium, salient hypoconid, the entoconid is comparatively Phonocdromus, and Pichipilus. Finally, the paraconid smaller, the hypoconulid is less proximate to the of ml is reduced in all paucituberculatans, as in the entoconid (in Bardalestes it is almost immediately type of Riolestes capricornicus. posterior to the entoconid), it has a shallower talonid Although not frequent among more modern mar basin, and it lacks a posterobasal cingulum. All these supials, the location of the metaconid somewhat pos differences warrant a generic distinction between terior with respect to the protoconid appears not these taxa.

RESULTS OF THE include the families Caenolestidae, Palaeothentidae, PHYLOGENETIC ANALYSIS and Abderitidae, different ‘pseudodiprotodont’ groups have been considered as phylogenetically related, Five most parsimonious trees of 116 steps in length and those hypotheses were formalized in various (CI = 0.55; RI = 0.79) were obtained. The strict con classifications (see Table 2). One of the most endur sensus tree, the unambiguous synapomorphies, and ing views was the proposal of Gregory (1910) and the values of relative Bremer support are shown in Simpson (1928) of closer relationships between Fig. 7. Two main clades are recognized in the strict Polydolopidae and Caenolestidae, which led to the consensus tree. One of them shows a basal trichotomy

long-lasting classification of both groups in the Downloaded formed by Pucadelphys, Derorliynchus, and the clade Superfamily Caenolestoidea (Simpson, 1930, 1945; that contains the new genera Riolestes and Bardal- de Paula Couto, 1952a, 1961; Reig, 1955). During estes plus the traditionally known Paucituberculata the 1960s a significant change in the classification (see Discussion). Within the latter clade two major

of marsupials occurred when Ride (1964) proposed from grouping emerge: the Palaeothentoidea clade (that a scheme that included orders. In this context,

includes Pichipilidae, Abderitidae, and Palaeothen- https://academic.oup.com/zoolinnean/article-abstract/155/ the name Paucituberculata was again adopted, but tidae) and the Caenolestoidea clade. It is the last that only to include Simpson’s Caenolestoidea (i.e. includes the extant paucituberculatan marsupials. Caenolestidae + Polydolopidae). Kirsch’s (1977) The other main group contains Microbioterium and scheme is among the classifications that followed Glasbius, along with a large grouping that includes this arrangement. During the decades since, dif a traditionally considered Polydolopimorphia plus ferent phylogenies of the Marsupialia have been Proargyrolagus and Klohnia. proposed on the basis of molecular characters, anatomical characters, or both. Deeply rooted in these discussions is the issue of whether or not the DISCUSSION ‘pseudodiprotodonts’ are regarded as a natural As a result of our analyses two important issues group. Three basic hypotheses have been advanced concerning the phylogeny of South American marsu to date: (1) ‘pseudodiprotodonts’ are a natural group pials can be addressed: the supposed monophyly of all [Simpson, 1945; Ride, 1964; Aplin & Archer, 1987; ‘pseudodiprotodont’ marsupials, and the extension Marshall, 1987; Marshall etal., 1990 (in part); and content of the Paucituberculata. Both of these Kirsch etal., 1997]; (2) Paucituberculata and Poly are discussed below. dolopimorphia do not constitute a natural group, and the Argyrolagoidea are included within the former [Marshall etal., 1990 (in part); Szalay, 1994]; ‘PSEUDODIPROTODONTS’ IS NOT A NATURAL GROUP

(3) Paucituberculata and Polydolopimorphia do not 86

The term ‘pseudodiprotodonts’ is usually employed form a natural group, and the Argyrolagoidea are '2622 either as a formal or as an informal designation for included within the latter (Goin & Candela, 2004;

several groups of (mostly extinct) South American Case, Goin & Woodburne, 2005). These proposals >85

marsupials possessing a hypertrophied and procum are expressed in the classification schemes shown by

bent first incisor: Caenolestidae, Palaeothentidae, in Table 2. guest Abderitidae, Prepidolopidae, Bonapartheriidae, Although they were originally restricted to repre

Polydolopidae, Argyrolagidae, Patagoniidae, and sentatives of the genus Polydolops and allied forms, on

Groeberidae. Arguments as to whether these taxa diverse findings during the second half of the 20th 23

represent a natural group are still under way (see century resulted in a notable increase in our knowl Sepiembe below). According to Ride (1962) the pseudodiprot- edge of the extent and diversity of the Polydolopimor odonty of South American forms evolved convergently phia (Goin & Candela, 1996, 2004; Case et al., 2005). with that of kangaroos and similar Australasian The current concept of Polydolopimorphia includes

forms that are grouped in the Order Diprotodontia. not only the Polydolopidae but also the prepidolopids, 20

The fact that the hypertrophied procumbent incisor bonapartherids (Bonapartheriinae + Epidolopiinae), 9 of the caenolestids and related forms derives from il gashterniids, and an assemblage of taxa whose or i2, whereas in Diprotodontia it derives from i3 intraordinal relationships are not yet clearly estab or i4, was central to his arguments (see Ride, 1962: lished: Hondonadia, Rosendolops, Wamradolops, 295-300). Klohnia, and Roberthoffstteteria (Goin & Candela, The history of the Paucituberculata concept is 1996, 2004; Goin etal., 2003; Case etal., 2005). All long and complex, as is the history of proposed phy these authors also argued in favour of the inclusion logenetic relationships of paucituberculatans with of the Argyrolagoidea within the Polydolopimorphia. other South American marsupial groups. Ever since The concept of Pseudiprotodontia was introduced Ameghino (1894) erected the Paucituberculata to by Kirsch et al. (1997) as a formal taxon including the

Alphadon I Microbiotherium

/ 23 ft-- Glasbius 1 32 36 38 35 40 41 — Roberthoffstetteria 1 1 Fo 'Polydolops I 1/33 Downloaded

,|o Prepidolops

II 10— pBonapartherium ... from

\ 6 11 42 43 ' 1 https//academic.oup.com/zoolinnean/article-abstract/155/4/867/2622985 XXM}-*------3 4 9 10 14 16 23 25 _ . . 2 111 o-oo-o— Epidolops 2 2 11 0 3 11 1/33 \ 32 \5 6 8 2o <2 Proargyrolagus ’ UF^Klohnia 33 • Pucadelphys zoc—Derorhynchus 1-7 Bardalestes Riolestes Stilotherium Pliolestes Rhyncholestes

Caenolestes by

guest 113 2 1

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Phonocdromus September Palaeothentes

15 16 22 24 Acdestis 2019 0 2 2 1 3/43 Abderites Parabderites

Figure 7. Strict consensus of five equally most parsimonious trees of ‘pseudodiprotodont’ marsupials. Numbers above each branch indicate character number, whereas those below are the character-states; absolute and relative Bremer support values are below each branch.

Table 3. A proposed classification of the Paucituberculata Riolestes and Bardalestes as Paucituberculata Order Paucituberculata Ameghino, 1894 Plesion Dracolestes gen. nov. Among the overwhelming diversity of South American Plesion Riolestes gen. nov. Palaeocene marsupials, known mainly from remains Superfamily Caenolestoidea Trouessart, 1898 found at Tiupampa (Bolivia; see Marshall & de Family Caenolestidae Trouessart, 1898 Muizon, 1988; de Muizon, 1991) and Itaborai (Brazil; Stilotherium Ameghino, 1887 see de Paula Couto, 1952a, b, 1962, 1970; Marshall, Pliolestes Reig, 1955

1987), most marsupial lineages that evolved during Downloaded Rhyncholestes Osgood, 1924 the Cenozoic in this continent were already present: Caenolestes Thomas, 1895 Didelphimorphia, Microbiotheria, Sparassodonta, Superfamily Palaeothentoidea, new rank Polydolopimorphia, and Paucituberculata. The new Family Pichipilidae (Marshall, 1980), new rank

taxa Riolestes capricornicus and Bardalestes bunco from Pichipilus Ameghino, 1890 constitute the oldest evidence of undoubted Paucitu

Phonocdromus Ameghino, 1894 https://academic.oup.eom/zoolinnean/article-abstract/155/4/867/2622985 Family Palaeothentidae Sinclair, 1906 berculata in South America. Note that the three syna Palaeothentes Ameghino, 1887 pomorphies (labially salient hypoconid, laterally Acdestis Ameghino, 1887 compressed entoconid, and StB or StB and StC + StD Abderites Ameghino, 1887 larger than the paracone and metacone, respectively) Parabderites Ameghino, 1902 that nested Bardalestes, Riolestes and the remaining Paucituberculata (i.e. Palaeothentoidea + Caenolestoidea), are coincident with those features previously considered as distinctive of this group Paucituberculata (Caenolestoidea + Argyrolagoidea) (Abello, 2007). This agrees with the definition of the and the Polydolopimorphia as a natural group. With Paucituberculata as the clade stemming from the some variations, a similar concept was supported by most recent common ancestor of Riolestes, Bardal Simpson (1945); Ride (1964) and other more modern estes, and the Palaeothentoidea + Caeonoestoidea authors. clade. Within Paucituberculata, Bardalestes and Rio The results of our analysis (see also Abello et al., lestes are the most basal and primitive members of 2004) argue against this grouping. On the one hand, the order, showing the plesiomorphic condition for Microbiotlierium, Glasbius plus the Polydolopimor each feature present in the remaining Paucitubercu phia (including the Argyrolagoidea within the latter) lata. Riolestes and Bardalestes are informative on the form a monophyletic group supported by three syna- early evolution of the molar pattern in the Paucitu pomorphies (Fig. 7): large, bulbous protocone (32'), berculata. Among them, five features support the nonwinged metaconule (361) and reduced stylar shelf Caenolestoidea + Palaeothentoidea clade: paracristid (381). Taking into account recent proposals favouring of ml lacking a notch (ll1); hypoconulid somewhat close relationships between microbiotheriids and the reduced and anteroposteriorly compressed (161); open

diprotodontian radiation (e.g. Kirsch etal., 1997; centrocrista, with the postparacrista and premetac- by

Horovitz & Sanchez-Villagra, 2003), the hypothesis of rista fused to the lingual slopes of the STB and STD, guest a grouping between Microbiotheria and Polydolopi respectively (333); metaconule much larger than the

morphia as part of a more comprehensive concept paraconule; and labiolingually compressed (391) stylar on

of Australidelphia deserves further research (not cusps which are lingually expanded, but not reaching 23

attempted here). On the other hand, Didelphimorphia the lingual face of the protocone (372). Taking into Sepiembe and Paucituberculata analysed here represent a account the plesiomorphic conditions of Riolestes and lineage supported by two features: deeply V-shaped Bardalestes, the inferred ancestral molar pattern of centrocrista (332) and metacone larger than the para the Paucituberculata is characterized by the presence

cone (351). Three synapomorphies support the Pauci of a paracristid notch in the ml, a well-developed 20 1 tuberculata clade including all the remaining taxa, hypoconulid, uncompressed stylar cusps, a closed and 9 with the exception of Pucadelphys and Derorliynchus: deeply ‘V-shaped centrocrista, and a metaconule labially salient hypoconid (151), laterally compressed larger than the paraconule but not enlarged or entoconid (181), and StB or StB and StC + StD larger ‘hypocone’-like. This latter feature gives to the upper than the paracone and metacone, respectively (342). molar a subtriangular occlusal design that differs Summing up, according to the results of our analysis, from the typical quadrangular pattern of the we will hereafter restrict the concept of order Pauci remaining Paucituberculata. tuberculata to that of the ‘Caenolestidae’ sensu Bardalestes and Riolestes not only shed light on the Marshall (1980) plus the new taxa described here phylogenetic relationships of the remaining Paucitu (Table 3). berculata (see below) but also give some hints on the

© 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155, 867-884 880 F. J. GOIN ET AL. very origin, and timing, of this marsupial clade. ristid in ml-3 (191), m4 single-rooted and greatly Meredith et al. (2008) have recently reviewed the reduced in relation to m3 (251). Stilotherium relationships and timeline of all major marsupial is the sister taxon to {Pliolestes {Caenolestes + clades. Their results, applying MULTIDIVTIME and Rhyncholestes). The latter group is supported by the BEAST analyses for the divergence estimates, con synapomorphy: entoconid posteriorly located (201). clude that the ‘All marsupials but Didelphimorphia’ Rhyncholestes plus Caenolestes share one synapomor clade (i.e. the Paucituberculata plus the Australidel- phy: very shallow metacristid in m2-3 (291). Pliolestes phia of their phylogeny in Meredith et al. 2008, fig. 2) shows one homoplasic character shared with the rep

split between 71.3 and 85.6 Mya (see their table 5). resentatives of the Palaeothentoidea (see bellow): Downloaded That is, the late (but not latest) Cretaceous. In sharp para- and metaconids of m3 very close or fused (231). contrast, their divergence estimates for the Paucitu Note that neither the living caenolestid Lestoros berculata are stated to be between 9.2 and 14.1 Mya. nor the extinct Pseudhalmarhiphus were considered

The empirical evidence here provided on the fossil in this paper. The holotype (and only known remain) from record of the Paucituberculata supports none of these of the Deseadan species Pseudhalmarhiphus guara- estimates. The oldest known Paucituberculata is niticus Ameghino (1899) (only species of the genus) https://academic.oup.eom/zoolinnean/article-abstract/155/4'867/2622985 the Late Palaeocene Riolestes capricornicus. Dero- has disappeared from Argentinean collections, so rhynchids, which stand as a probable sister group of almost nothing can be said of its affinities. Marshall paucituberculatans, have their oldest record in the (1976, 1980), based on illustrations of the holotype latest early Palaeocene (the latest Danian Banco published by Ameghino (1894), said that ‘. . . Negro deposits; Bond et al., 1995). The much better Pseudhalmarhiphus is structurally similar to and known, earliest Palaeocene fauna of Tiupampa, lacks is probably ancestral to Stilotherium dissimile’ any record not only of paucituberculatans but also (Marshall, 1980: 35). Finally the generic validity of of derorhynchids. Lestoros inca (Thomas, 1917) - the only species of this genus geographically restrained to the Andean region south of Peru - has been discussed (e.g. Simpson, Cladistics of the Paucituberculata 1970). Marshall (1980) stated that Caenolestes and The present analysis yielded several unexpected Lestoros can hardly be distinguished. results regarding the traditional systematic concepts for Paucituberculata marsupials: (1) the exclusion of 2. Another result of this analysis is the exclusion of Pliolestes from the ‘Pichipilinae’ {sensu Marshall Pichipilus and Phonocdromus from the Caenoles etal., 1990) and their grouping together with the tidae and their grouping as sister taxa of Caenolestidae Stilotherium, Caenolestes, and Rhync- palaeothentids + abderitids. The features that, holestes; and (2) the grouping of Pichipilus and according to Marshall (1980), justify regarding the Phonocdromus as sister taxa to Palaeothentidae + ‘Caenolestinae’- including Stilotherium, Pseudhal Abderitidae clade. These conclusions are discussed marhiphus, Caenolestes, Lestoros, Rhyncholestes, separately. Pliolestes, Phonocdromus, and Pichipilus - as a

monophyletic group, are the following: (1) double 1. In his original description of Pliolestes tripotam by

rooted and functional p2; (2) p3 large, double-rooted icus, Reig (1955) pointed out the close affinities of guest and subequal or higher than the trigonid of ml; (3) this genus with Phonocdromus (see also Pascual

M/m 1-4 tuberculo-sectorial, without lophs in on & Herrera, 1973). Subsequently Marshall (1980),

unworn molars; (4) ml with prominent metaconid; 23 in his review of the South American Caenoles-

(5) nonmodified talonid and trigonid areas; (6) m2-3 Septembe toidea, included Pliolestes in the new tribe with differentiated trigonids and talonids; (7) Pichipilini, together with Phonocdromus and talonid much larger than trigonid in occlusal view; Pichipilus. Finally, Marshall etal. (1990) raised (8) Ml-3 with metacone (‘intermediate conule’ this taxon to a subfamiliar rank: Pichipilinae sensu Marshall, 1980) labially orientated; (9) Ml 20

(Caenolestidae). 1 quadritubercular; (10) neither P3 nor Ml, p2 or ml 9 The results of our analysis support the hypothesis are modified as sectorial teeth; (11) presence of an that Pliolestes does not form a monophyletic group antorbital vacuity between the nasal, maxillary, with Pichipilus and Phonocdromus, but instead with and frontal. However, none of these features are the ‘Caenolestini’ sensu Marshall (1980). Actually, the synapomorphies within the Paucituberculata, nor concept of Caenolestidae proposed in this paper is are present in all ‘Caenolestinae’ taxa: (1) a double restrained to the following genera: Caenolestes, Plio rooted and functional p2 is the generalized condi lestes, Rhyncholestes, and Stilotherium, and is char tion in all marsupials; (2) p3 is quite small acterized by the following synapomorphies (see compared with the development of this tooth in the Fig. 7): high entocristid in ml-3 (17'1, curved entoc- Palaeothentidae and Abderitidae - and, in any case,

its development is only moderate with respect to ACKNOWLEDGEMENTS other marsupial groups; (3) the molars of the We thank curators and colleagues from the Museo de Palaeothentidae are also tuberculo-sectorial and La Plata (Argentina), Laboratorio de Investigaciones lack lophs; (4) in the Palaeothentidae the metaconid en Evolución y Biodiversidad (Esquel, Argentina) and is also prominent; (5) the statement that that the the Museu de Ciencias Naturais of the Fundacao trigonid and talonid areas in the ml of ‘Caenoles- Zoobotánica de Rio Grande do Sul (Porto Alegre, tidae’ are ‘non-modified’ was not verified in our Brazil) for allowing us to study the specimens under study: in Caenolestes, as well as in Rhyncholestes, their care. We also thank Dr Michael Woodburne

Stilotlierium, and Pliolestes, the para- and meta Downloaded for his very useful suggestions and comments to conids are separated and the trigonid lacks a basin; the original manuscript. We also thank Sandrine (6) trigonids and talonids are differentiated in all Ladevéze, Cajus Diedrich, and an anonymous the Paucituberculata and, besides, both Pichipilus reviewer for their constructive comments. F. Goin

and Plionocdromus share the same differentiation from acknowledges support from the Alexander von between both regions as the Palaeothentidae; (7)

Humboldt Foundation and CONICET (PIP 5621). https://academic.oup.com/zoolinnean/article-abstract/155 talonid wider than trigonid is not an exclusive feature of ‘Caenolestidae’ sensu Marshall (1980); rather, as it has been pointed out, it is already present in a generalized form of Paucituberculata: REFERENCES Riolestes capricornicus; (8) the metacone, when present, is always labially orientated, adjacent to Abello MA. 2007. Sistemática y bioestratigrafía de los Pau the stylar cusp D; (9) Ml is quadritubercular in all cituberculata (Mammalia, Marsupialia) del Cenozoico de América del Sur. Unpublished dissertation, Universidad Paucituberculata - although with slight variants; Nacional de La Plata, La Plata, Argentina. see Character Analysis; (10) ‘P3, Ml, p2, and ml not Abello MA Candela AM, Goin FJ, Oliveira E. 2004. differentiated in sectorial teeth’ is the generalized Phylogeny of South American ‘Pseudodiprotodont’ marsupi condition in all marsupials; (11) finally, the pres als. Ameghiniana 41 (4 Suppl.): 32R. ence of the vacuities cannot be verified in Pichipilus Ameghino F. 1894. Synoptic enumeration of the fossil mam or Plionocdromus (see Character Analysis). This malian species from the Eocene formations of Patagonia. latter character is important because, as Marshall Boletín De La Academia De Ciencias De Córdoba 13: 259- (1980: 127) himself recognized, despite the other 452. features listed in his diagnosis, this one would be Ameghino F. 1899. Geologic-Palaeontologic summary. actually the only synapomorphy in common with Supplement, Additions and emendations. La Plata. his ‘Caenolestinae’ (‘Caenolestini’ + ‘Pichipilini’). As Aplin KP, Archer M. 1987. Recent advances in marsupial

mentioned above, the only specimen of ‘Pichipilini’ systematics with a new syncretic classification. In: Archer -o867/_'622985 in which a skull has been preserved, with the M, ed. Possums and opossums: studies in evolution. Sydney: rostrum area, is MLP 66-1-17-204, assignable to Surrey Beatty & Sons and the Royal Zoological Society of Pichipilus centinelus-, however, the presence or New South Wales, xv-Ixxii. Aragón E, Mazzoni MM. 1997. Geology and stratigraphy of

absence of antorbital vacuities cannot be deter the volcanic-pyroclastic complex of Middle Chubut River by mined because of the damage to the material guest {contra Marshall & Pascual, 1977). Thus, Pichipilus (Eocene), Chubut, Argentina. Revista de la Asociación Geológica Argentina 52: 243-256.

and Plionocdromus do not show derived features in on Aragón E, Romero EJ. 1984. Geology, palaeoenvironments

common with the ‘Caenolestinae’ sensu Marshall 23 and palaeobotany of the Tertiary outcrops from Western Rio

et al. (1990), but with the Palaeothentidae and Septembe Abderitidae, with which they form a monophyletic Negro, Neuquén and Chubut. IX Congreso Geológico Argen group. Both genera, here included within the family tino, Actas IV: 475-507. Aragón E, Mazzoni MM, Merodio JC. 1987. Geochemical Pichipilidae (new rank) do not show affinities characterization of the Barda Colorada Ignimbrite at the with Pliolestes, a caenolestid related to the 20:9 Middle Chubut River. X Congreso Geológico Argentino, Rhyncholestes + Caenolestes clade. The Pichipilidae Actas 4: 171-174. are the sister group of palaeothentids + abderitids. Archangelsky S. 1974. On one age for the flora of Laguna In turn, pichipilids, palaeothentids, and abderitids, del Hunco, Chubut Province. Ameghiniana 11: 413-417. here included within the Superfamily Palaeothen- Asher RJ, Horovitz IA, Sánchez-Villagra M. 2004. First toidea nov., are the sister group of the Caenoles- combined cladistic analysis of marsupial mammal interre toidea. In our concept, this last taxon includes lationships. Molecular Phylogenetics and Evolution 33: 240- a single family: Caenolestidae, containing the 250. following genera: Stilotlierium, Pseudlialmarlii- Baker ML, Wares JP, Harrison GA, Miller RD. 2004. phus, Caenolestes, Lestoros, Rhyncholestes, and Relationships among the Families and Orders of Marsupials Pliolestes. and the major mammalian lineages based on recombination

activating gene-1. Journal of Mammalian Evolution 11: Asociación Paleontológica Argentina, Publicación Especial 1-16. N° 5, 71-78. Bergqvist LP. 1996. Reassociation of the postcranials belong Goin FJ, Candela AM, de Muizon C. 2003. The affinities of ing to the ungulate species of the S. J. de Itaboraf Basin Roberthoffstetteria nationalgeographica (Marsupialia) and (Palaeocene), State of Rio de Janeiro, and a phylogeny of the the origin of the polydolopine molar pattern. Journal of ‘Condylarthra’ and South American ungulates based on Vertebrate Paleontology 23: 869-876. the postcranial bones. Unpublished thesis, Universidade Goin FJ, Woodbume MO, Case JA, Vizcaíno SF, Federal do rio Grande do Sul, Porto Alegre, Brasil. Reguero M. 2000. New discoveries of ‘opossum-like’ mar Bonaparte JF, Van Valen LM, Kramartz A. 1993. The supials from Antarctica (Seymour Island, Middle Eocene). local fauna of Punta Peligro, Lower Palaeocene, Chubut Journal of Mammalian Evolution 6: 335-365. Downloaded Province, Patagonia, Argentina. Evolutionary Monographs Goin FJ, Tejedor MF, Abello MA. 2001. Preliminary con 14: 1 61. clusions on the Palaeogene marsupial assemblage from Bond M, Carlini AA, Goin FJ, Legarreta L, Ortiz Jau- Laguna Giordanella (Paso del Sapo, Chubut, Argentina;

reguizar E, Pascual R, Uliana MA. 1995. Episodes in ?Middle Eocene). Ameghiniana 38 (4 Suppl.): 9R. from

South American land mammal evolution and sedimenta Goloboff PA, Farris JS. 2001. Methods for quick consensus https://academic.oup.com/zoolinnean/article-abstract/155/-V86 tion: testing their apparent concomitance in a Palaeocene estimation. Cladistics 17: 26-34. succession from Central Patagonia. VI Congreso Argentino Goloboff P, Farris J, Nixon K. 2003. T.N.T.: tree analysis de Paleontología y Bioestratigrafía, Trelew, Actas 47-58. using new technology. Program and documentation avail Cardillo M, Bininda-Emonds ORP, Boakes E, Purvis A. able from the authors and at: http://www.zmuc.dk/public/ 2004. A species-level phylogenetic supertree of marsupials. phylogeny Journal of Zoology 264: 11-31. Gregory WK. 1910. The orders of mammals. Bulletin of the Case JA, Goin FJ, Woodbume MO. 2005. ‘South American’ American Museum of Natural History 27: 1-524. marsupials from the late cretaceous of North America and Horovitz I, Sánchez-Villagra MR. 2003. A morphological the origin of marsupial cohorts. Journal of Mammalian analysis of marsupial mammal higher-level phylogenetic Evolution 11: 223 255. relationships. Cladistics 19: 181 212. Cifelli RL. 1994. Therian mammals of the terlingua local liliger C. 1811. Prodrornus systematics mammalium et avium fauna (Judithian), Aguja formation, big bend of the Rio additis terminis zoographicis utrudque classis. Berlin: C. Grande, Texas. Contributions to Geology, University of Salfeld. Wyoming 30: 117-136. Jansa SA, Voss RS. 2000. Phylogenetic studies on didelphid Cifelli RL, de Muizon C. 1998. Marsupial mammals from marsupials I. Introduction and preliminary results from the upper Cretaceous North Horn Formation, Central Utah. nuclear IRBP gene sequences. Journal of Mammalian Journal of Paleontology 72: 532-537. Evolution 7: 43 77. Flynn JF, Wyss AR. 1999. New marsupials from the Eocene- Kielan-Jaworowska Z, Cifelli RL, Luo Z-X. 2004. Oligocene transition of the Andean Main Range, Chile. Mammals from the age of dinosaurs. Origins, evolution, and Journal of Vertebrate Paleontology 19: 533-549. structure. New York: Columbia University Press.

Goin FJ. 2003. Early Marsupial radiations in South America. Kirsch JAW. 1977. The classification of marsupials with '2622 In: Jones M, Dickman C, Archer M, eds. Predators with special reference to karyotypes and serum proteins. In:

pouches: the biology of carnivorous marsupials. Colingwood: Hunsaker D, ed. The biology of marsupials. New York: <85

CSIRO Publishing, 30 42. Academic Press, 1 50. by

Goin FJ, Candela AM. 1996. A new early Eocene Polydol- Kirsch JAW, Lapointe FJ, Springer MS. 1997. DNA- gues* opimorphian (Mammalia, Marsupialia) from Patagonia. hybridization studies of Marsupials and their implications

Journal of Vertebrate Paleontology 16: 292-229. for Metatherian classification. Australian Journal of on

Goin FJ, Candela AM. 2004. New Paleogene marsupials from Zoology 45: 211-180. 23

the Amazonian basin, Southeastern Perú. In: Campbell KE Koenigswald W von, Goin FJ. 2000. Enamel differentiation Sepiembe Jr, ed. The Paleogene mammalian fauna of Santa Rosa, in South American Marsupials and a comparison of placen Amazonian Perú, Vol. 40. Los Angeles: Natural History tal and Marsupial enamel. Palaeontographica Abteilung A Museum of Los Angeles County, Science Series. 15 60. 255: 1 40.

Goin FJ, Candela AM, Forasiepi A. 1997. New, middle Ladevéze S. 2004. Metatherian petrosals from the Late Pale- 20:9 Palaeocene marsupials from central Patagonia. Journal of ocene of Itaborai (Brazil), and their phylogenetic implica Vertebrate Paleontology 17 (3 Suppl.): 49A. tions. Journal of Vertebrate Paleontology 24: 202-213. Goin FJ, Oliveira EV, Candela AM. 1998a. Carolocoutoia Ladevéze S. 2007. Petrosal bones of metatherian mammals ferigoloi n. gen. et sp. (Protodidelphidae), a new Palaeocene from the Late Paleocene of Itaborai (Brazil), and a cladistic ‘opossum-like’ marsupial from Brazil. Palaeovertebrata 27: analysis of petrosal features in metatherians. Zoological 145 154. Journal of the Linnean Society 150: 85-115. Goin FJ, Candela AM, Bond M, Pascual R, Escribano V. Ladevéze S, de Muizon C. 2007. The auditory region of 1998b. A new oposum (Mammalia, Marsupialia) from the early Paleocene Pucadelphydae (Mammalia, Metatheria) Palaeocene of Patagonia. In: Casadlo S, ed. Paleógeno de from Tiupampa, Bolivia, with phylogenetic implications. América del sur y de la Península Antartica. Buenos Aires: Palaeontology 50: 1123 1154.

Lage J. 1982. Description of the geological chart 43c, Gual- Marshall LG, Pascual R. 1977. New Caenolestid marsupials jaina, Chubut Province. Boletín del Servicio Geológico from Ameghino’s ‘Piso Notohippidense’ (SW Santa Cruz, Nacional 189: 1-72. Patagonia). Their bearings to the chronology and evolution Legarreta L, Uliana MA. 1994. Fossils and hiatuses asso of South American mammalian communities. Publicaciones ciations in the Upper Cretaceous-Neogene of Patagonia: a del Museo Municipal de Ciencias Naturales ‘Lorenzo sequential-stratigraphic perspective. Ameghiniana 31: 257- Scaglia’ 2: 91-122. 281. Mazzoni MM, Aragón E. 1985. The volcanic-pyroclastic Luckett WP, Hong N. 2000. Ontogenetic evidence for dental complex of the Huitrera Formation (Palaeocene-Eocene) in homologies and premolar replacement in fossil and extant the Middle Chubut River area, Argentina. Segunda Reunión caenolestids (Marsupialia). Journal of Mammalian Evolu Argentina de Sedimentologta, Buenos Aires, Aetas 180-184. Downloaded tion 7: 109-127. Mazzoni MM, Aragón E, Merodio JC. 1989. The Barda Marshall LG. 1976. On the affinities of Pichipilus osborni Colorada ignimbrite from the volcanic-pyroclastic complex Ameghino 1890 (Marsupialia, Caenolestidae) from the of Middle Chubut River. Revista de la Asociación Geológica

Santa Cruz beds of southern Patagonia, Argentina. Argentina 43: 246-258. from

Ameghiniana 13: 56-64. Meredith RW, Westerman M, Case JA, Springer MS. https://academic.oup.com/zoolinnean/article-abstract/155/->'86 Marshall LG. 1980. Systematics of the South American mar 2008. A Phylogeny and timescale for marsupial evolution supial family Caenolestidae. Fieldiana: Geology, New Series based on sequences for five nuclear genes. Journal of Mam 5: 1-145. malian Evolution. doi:10.1007/sl0914-007-9062-6. Marshall LG. 1982a. Systematics of the extinct South de Muizon C. 1991. The mammalian fauna of Tiupampa America marsupial family Polydolopidae. Fieldiana: (Lower Palaeocene, Stanta Lucia Formation), Bolivia. In: Geology, New Series 12: 1 109. Suarez-Soruco R, ed. Fósiles y facies de Bolivia. 1 Vertebra Marshall LG. 1982b. Systematic of the South America Mar dos, Vol. 12. Santa Cruz: Revista Técnica de Yacimientos supial family Microbiotheriidae. Fieldiana: Geology, New Petroleros Fiscales de Bolivia, 575-624. Series 10: 1 75. Nixon KC. 1999. WINCLADA (Compute r program and docu Marshall LG. 1984. The lower jaw of Eobrasilia coûtai mentation). Available at: http://www.cladistics.com/ Simpson, 1947, a unique didelphoid (not borhyaenoid) mar Oliveira EV. 1998. Taxonomy, Phylogeny and Paleobiogeo supial from the Palaeocene of Brazil. Journal of Paleontol graphy of the ‘Polyprotodont’ marsupials of the Middle ogy 58: 173 177. Palaeocene of the Itaborai Basin, Rio de Janeiro, Brazil. Marshall LG. 1985. Geochronology and land-mammal Unpublished thesis, Universidade Federal do Rio Grande do biochronology of the transamerican faunal interchange. Sul, Porto Alegre. In: Stehli FG,Webb SD, eds. The Great American biotic Oliveira EV, Goin FJ. 2006. Fossil marsupials from the interchange. New York: Plenum Press, 49 85. Palaeocene of Itaboriai: origins, radiations and biogeo Marshall LG. 1987. Systematics of Itaboraian (Middle Palae graphic history. In: Caceres, NC, Monteiro Filho ELA, eds. ocene) age ‘opossum-like’ marsupials from the limestone Os Marsupials do Brasil: Biología, Ecología e Evoluqao. Ed. quarry at Sâo José de Itaborai, Brazil. In: Archer M, ed. Campo Grande: UFMS, 299-320.

Possums and opossums: studies in evolution. Sydney: Surrey Osgood WH. 1924. Review of living caenolestids with descrip '2622 Beatty & Sons and the Royal Zoological Society of New tion of a new genus from Chile. Field Museum of Natural

South Wales, 91 160 History, Zoological Series 14: 165-173. >85

.Marshall LG, Butler RF, Drake RE, Curtis GH. 1981. Pascual R, Herrera HE. 1973. Additions to the knowledge of by

Calibration of the beginning of the age of mammals in Pliolestes tripotamicus Reig 1955 (Mammalia, Marsupialia, guest Patagonia. Science 212: 43 45. Caenolestidae) from the Upper Pliocene of Argentina.

Marshall LG, Case JA, Woodbume MO. 1990. Phyloge Ameghiniana 10: 36-50. on

netic relationships of the families of marsupials. In: Geno- de Paula Couto C. 1952a. Fossil mammals from the begin 23

ways HH, ed. Current mammalogy, Vol. 2. New York: ning of the Cenozoic of Brazil. Marsupialia, Didelphidae. Sepiembe Plenum Press, 433 502. American Museum Novitates 1567: 1-26. Marshall LG, de Muizon C. 1984. A new didelphid marsu de Paula Couto C. 1952b. Fossil mammals from the begin pial (Itaboraidelphys camposi nov. gen., nov. sp.) from the ning of the Cenozoic of Brazil. Marsupialia, Polydolopidae

middle Palaeocene (Itaboraian) of Saô Jose de Itaborai and Borhyaenidae. American Museum Novitates 1559: 1 27. 20'

(Brazil). Compte Rendus Hebdomadaires des Séances de T de Paula Couto C. 1961. Fossil marsupials from the Palae ■ Académie des Sciences, Paris 299: 1297-1300. ocene of Brazil. Anais da Academia Brasileira de Ciencias Marshall LG, de Muizon C. 1988. The dawn of the age of 33: 321 333. mammals in South America. National Geographic Research de Paula Couto C. 1962. Fossil didelphids from the Palae 4: 23 55. ocene of Brazil. Revista del Museo Argentino de Ciencias Marshall LG, de Muizon C. 1995. Part II: The skull. In: Naturales ‘Bernardino Rivadavia', Ciencias Zoológicas 112: de Muizon C, ed. Pucadelphys andinus (Marsupialia, 135 166. Mammalia) from the early Palaeocene of Bolivia, Vol. 165. de Paula Couto C. 1970. News on the fossil marsupials from Paris: Mémoires du Muséum National d'Histoire the Riochican of Brazil. Anais da Academia Brasileira de Naturelle, 21 90. Ciéncias 42: 19-34.

Petersen CS. 1946. Geological studies at Middle Chubut Sánchez-Villagra MR, Ladevéze S, Horovitz I, Argot C, River. Boletín de la Dirección General de Minas y Geología Hooker JJ. Macrini TE, Martin T, Moore-Fay S, de 59: 1 137. Muizon C, Schmelzle T, Asher RJ. 2007. Exceptionally Phillips MJ, Mclenachan PA, Down C, Gibb GC, Penny preserved North American Paleogene metatherians: adap D. 2006. Combined mitochondrial and nuclear DNA tations and discovery of a major gap in the opossum fossil sequences resolve the interrelations of the major Australa record. Biology Letters 3: 318-322. sian marsupial radiations. Systematic Biology 55: 122 137. Sánchez-Villagra MR, Kay RF. 1997. A skull of Proargyro- Rapela CW, Spalletti LA, Merodio JC, Aragón E. 1988. lagus, the oldest argyrolagid (Late Oligocene Salla Beds, Temporal variation and spatial variation of early tertiary Bolivia), with brief comments concerning its paleobiology. volcanism in the Patagonian Andes (40°-42°30'S). Journal Journal of Vertebrate Paleontology 17: 717-724. Downloaded of South American Earth Sciences 1: 75 88. Tejedor MF, Czaplewski NJ, Goin FJ, Aragón E. 2005. Reig OA. 1955. A new genus and species of caenolestinae Oldest South American Bats. Journal of Vertebrate Paleon from the Pliocene of Buenos Aires Province (Argentinian tology 25: 990 993.

Republic). Revista de la Asociación Geológica Argentina 10: Tejedor MF, Goin FJ, Gelfo JN, López G, Bond M, from

60 71. Carlini AA, Scillato-Yané GJ, Woodbume MO, Chor- https://academic.oup.eom/zoollnnean/article-abstract/155/J Ride WDL. 1962. On the evolution of Australian marsupials. nogubsky L, Aragón E, Reguero M, Czaplewski N, In: Leeper GW, ed. The evolution of the living organisms. Vincon S, Martin G, Ciancio M. In press. New early Melbourne: Melbourne University Press, 281 306. Eocene Mammalian fauna from Western Patagonia, Argen Ride WDL. 1964. A review of Australian fossils marsupials. tina. American Museum Novitates. Journal of the Royal Society of Western Australia 47: Thomas O. 1917. Preliminary diagnosis of new mammals 97 131. obtained by the Yale-National Geographic Society Peruvian Rougier GW, Wible JR, Novacek MJ. 2004. New specimen Expedition. Smithsonian Miscellaneous Collections 68: 1-3. of Deltatheroides cretacicus (Metatheria, Deltatheroidea) Volkheimer W, Lage J. 1981. Description of the chart 42c, from the Late Cretaceous of Mongolia. In: Dawson M, Cerro Mirador, Chubut Province. Boletín del Servicio Lillgraven A, eds. Pittsburgh: Bulletin of Carnegie Museum Geológico Nacional 181: 1-71. of Natural History, 243-264. Wilf PM, Cúneo R, Johnson KR, Hicks JF, Wing SL, Simpson GG. 1928. Affinities of the Polydolopidae. American Obradovich JD. 2003. High plant diversity in Eocene Museum Novitates 323: 1 13. South America: evidence from Patagonia. Science 300: 122 Simpson GG. 1930. Post-Mesozoic Marsupialia. In: Junk W, 125. ed. Fossilium catalogue 1: Animalia. Berlin: Kluger, 1-87. Simpson GG. 1945. The principles of the classification and a classification of mammals. Bulletin of the American Museum SUPPORTING INFORMATION of Natural History 85: 1-350. Additional Supporting Information may be found in Simpson GG. 1947. A new Eocene marsupial from Brazil.

American Museum Novitates 1357: 1 7. the online version of this article: 86

Simpson GG. 1970. The Argyrolagidae, extinct South Ameri Appendix SI. Data matrix 2622 can marsupials. Bulletin of the Museum of Comparative Appendix S2. Morphological characters used for

Zoology 139: 1 86. phylogenetic analysis 85

Szalay FS. 1994. Evolutionary history of the marsupials and by

Please note: Wiley-Blackwell are not responsible for an analysis of osteological characters. New York: Cambridge guest University Press. the content or functionality of any supporting mate

Sánchez-Villagra MR. 2001. The phylogenetic relationships rials supplied by the authors. Any queries (other than on

of argyrolagid marsupials. Zoological Journal of the missing material) should be directed to the corre 23

Linneati Society 131: 481 496. sponding author for the article. Sep'embe: