A Sulimski

AR Bleefeld

AR Wyss

B Patterson

Dian-Yong Guo

FS Szalay

J Meng

JI Bloch

Jonathan I. Bloch

KC Beard

M Schlosser

P Missiaen

PD Gingerich

PE Kondrashov

Philip D. Gingerich

Pieter Missiaen

R Tabuce

RJ Asher

RL Cifelli

S Ting

SP Zack

T Smith

Thierry Smith

WD Matthew

English

Missiaen, Pieter

SMITH, T

GUO, DY

BLOCH, JI

GINGERICH, PD

Ghent University Academic Bibliography

Naturwissenschaften (2006) 93: 407–411DOI 10.1007/s00114-006-0122-1SHORT COMMUNICATIONPieter Missiaen . Thierry Smith . Dian-Yong Guo .Jonathan I. Bloch . Philip D. GingerichAsian gliriform origin for arctostylopid mammalsReceived: 13 September 2005 / Accepted: 9 April 2006 / Published online: 23 May 2006# Springer-Verlag 2006Abstract Arctostylopids are common in Late Palaeoceneand Early Eocene mammal faunas of Asia, but they are rarein North America. From the time of their first discovery,arctostylopids were grouped with the strictly endemicSouth American Notoungulata based on their strikinglysimilar dental morphology. This relationship was chal-lenged based on dental morphology of more recentlydiscovered arctostylopids and on supposed tarsal mor-phology (based on unassociated material) of the Asianarctostylopid Palaeostylops. Therefore, Arctostylopidaewere placed in a separate order, Arctostylopida, of enig-matic affinities. Many authors, however, continue to uniteArctostylopidae and Notoungulata based on dental simi-larities. In the Late Palaeocene Subeng site in InnerMongolia, we identified the Palaeostylops tarsals based ontheir size and abundance. This identification is supportedby comparison to unpublished Arctostylops tarsals from theNorth American Clarkforkian, derived from a semi-artic-ulated skeleton also including dental material. Tarsalmorphology shows moderate similarity to the gliriformPseudictops, and strong resemblance to the tarsally con-servative gliroid Rhombomylus. Hence, Arctostylopidaemay best be grouped with Asian non-gliroid Gliriformes,which we interpret as having dispersed into North Americain the Late Palaeocene.IntroductionArctostylopidae are common and diverse elements ofAsian Late Palaeocene and Early Eocene mammal faunas(Cifelli et al. 1989; Ting 1998) but are exceedingly rare inNorth America where they were first discovered. Based onstriking dental resemblances, arctostylopids were immedi-ately grouped with the strictly endemic South AmericanNotoungulata, and they were considered the first compel-ling evidence for Early Tertiary mammal dispersal betweenNorth and South America (Matthew 1915). Since then,Arctostylopidae have figured prominently in variousintercontinental dispersal scenarios (Patterson and Pascual1972; Cifelli 1983a; Gingerich 1985; Beard 1998).Cifelli et al. (1989) published a revision of Arctostylo-pidae including the first arctostylopid tarsals, attributed tothe Asian Late Palaeocene Palaeostylops iturus. Theseauthors argued that dental similarities to Notoungulatawere caused by convergence. Their discussion of thearctostylopid ankle morphology noted the lack of certainnotoungulate tarsal synapomorphies and a limited similar-ity to the Asian endemic Pseudictops. In conclusion, Cifelliet al. (1989) placed Arctostylopidae in a new, separateorder Arctostylopida. Preliminary observations on a semi-articulated partial skeleton of North American Arctostylopsby Bloch (1999) renewed the discussion on arctostylopidphylogeny, and Kondrashov and Lucas (2004) restoredPieter Missiaen is an aspirant of the Research Foundation-Flanders(RF-Flanders)P. Missiaen (*)Research Unit Paleontology, Ghent University,Krijgslaan 281-S8,9000 Ghent, Belgiume-mail: Pieter.Missiaen@ugent.beT. SmithDepartment of Paleontology,Royal Belgian Institute of Natural Sciences (RBINS),rue Vautier 29,1000 Brussels, BelgiumD.-Y. GuoDepartment of Natural Sciences,Inner Mongolian Museum (IMM),Xinhua Street 2,Hohhot, Inner Mongolia 010020, ChinaJ. I. BlochFlorida Museum of Natural History,University of Florida,Dickinson Hall 22,Gainesville, FL 32611-7800, USAP. D. GingerichDepartment of Geological Sciences and Museumof Paleontology,University of Michigan,Geddes Road 1109,Ann Arbor, MI 48109-1079, USAArctostylopidae as a family within Notoungulata. Ninetyyears after their first discovery, the affinities of arctostylo-pids remain controversial.The Late Palaeocene mammals from the Subeng site inInner Mongolia have only recently been studied in detail(Smith et al. 2004; Missiaen and Smith 2005). In thislocality, dental material from P. iturus is highly abundant,and we identified the isolated tarsals from P. iturus(Fig. 1) based on their size and abundance (Fig. 2). Thisidentification is supported by their similarities to thetarsals of Arctostylops (Fig. 3), the only arctostylopidtarsals known directly associated with dental material(Bloch 1999). In this study, we fully illustrate, describeand compare the Palaeostylops tarsals, and discuss theirfunctional interpretation and phylogenetic and biogeo-graphic implications.Systematic palaeontologyGliriformes Wyss and Meng, 1996Arctostylopidae Schlosser, 1923Palaeostylops Matthew and Granger, 1925Palaeostylops iturus Matthew and Granger, 1925Referred materialThree complete astragali and a proximal part of an as-tragalus (IMM 2004-SB-4 to 8); three complete calcaneaand a distal part of a calcaneum (IMM 2004-SB-9 to 12).Description (Fig. 1)The astragalar trochlea is marked and slightly asym-metrical, with the lateral crest somewhat longer than themedial crest. The body is semicylindrical without a dorsalforamen. The lateral side bears a semicircular fibular facetand a small lateral process, and the medial side has a smalltibial process. The neck is relatively long and somewhatconstricted. The small head bears a narrow cuboid facet, along, dorsoventrally oriented navicular facet and a medialfacet extending far on the medioplantar side. These threefacets are not sharply delimited, but neither one is confluentwith the sustentacular facet. This facet is slightly proxi-modistally elongated and weakly convex. The long ectalfacet faces lateroplantarly and is strongly concave.The calcaneum is robust in lateral outline, with a long,somewhat compressed tuber. The ectal and fibular facetsare large and conspicuous, strongly convex and roughlyparallel to the long axis. The ectal facet is rounded anddorsoventrally inclined, facing partially medially with anangle similar to that of the astragalar ectal facet. The fibularfacet is rectangular in dorsal view, somewhat shorteranteroposteriorly than the ectal facet and slightly dippingmedioventrally. The proximal border of the sustentaculumis situated midway of the ectofibular facet and is almostperpendicular to the long axis; the distal border is moreobliquely oriented and reaches the medialmost limit of thecuboid facet. The cuboid facet has an oblique distomedialorientation and a subrhomboid outline. The distal plantartubercle is small but clearly visible. A small but prominentperoneal process is present on the distalmost lateral end.There is no transverse calcaneal canal.Fig. 1 SEM micrographs of P. iturus tarsals from Subeng. Left calcaneum (IMM 2004-SB-9) and left astragalus (IMM 2004-SB-4) inmedial (a, g), dorsal (b, h), lateral (c, i), ventral (d, j), proximal (e, k) and distal (f, l) views408ComparisonThe new Palaeostylops tarsals show several differencesfrom those figured by Cifelli et al. (1989). Many of theobserved differences could be due to wear, breakage ordifferences in orientation, and at least some errors occurredduring the drawing process (note the inversion of the leftcalcaneum, which was depicted as a right calcaneum in theventral view). We have not seen these materials and sorefrain from judging the association made by Cifelli et al.(1989; criticised by Kondrashov and Lucas 2004).Comparison of the Palaeostylops tarsals to those ofNotoungulata is of primary interest. The oldest unambig-uous Notoungulata are Colbertia, Itaboraitherium andCamargomendesia from the Late Palaeocene Itaborai faunain Brazil, and the tarsals have been identified for all threegenera (Bergqvist 1996). These tarsals exemplify thenotoungulate morphotype that is characterised by thefollowing synapomorphies (Cifelli 1983b, 1993; Bergqvist1996). The astragalus has a long, constricted neck with anoblique dorsal crest, a large medial protuberance, a sulcusleading laterally from the dorsal astragalar foramen and awell-developed contact of sustentacular and navicularfacet. The calcaneum has a conspicuous beak on the dorsaldistomedial end and a deep groove between the susten-tacular and ectal facet. Out of all these characters, thePalaeostylops tarsals only match the long, constrictedastragalar neck, equally observed in other groups, rangingfrom Palaeocene leptictids to Recent elephant shrews andincluding Pseudictops, Rhombomylus and Palaeolagus(Fig. 4). The Palaeostylops tarsals do not exhibit any othernotoungulate synapomorphy and thus do not, by them-selves, provide support for placement of Arctostylopidaewithin the Notoungulata.We made extensive comparisons with tarsals of mostextinct and modern mammal orders, finding that thearctostylopid tarsals are characterised by the followingfeatures. The astragalus has a well-defined and fairlysymmetrical trochlea without dorsal foramen, a neck that ismoderately long and somewhat constricted and a navicularfacet that is not confluent with the astragalar sustentacularfacet. The calcaneum has a long, laterally compressedtuber, large ectal and fibular facets oriented roughly parallelto the long axis, a moderate peroneal process and anobliquely oriented cuboid facet.This combination of diagnostic characters is only met bythe Early Eocene eurymylid Rhombomylus, which alsoexhibits the best overall resemblances to the Palaeostylopstarsals. Meng et al. (2003) published a detailed descriptionof Rhombomylus, and their comprehensive analysis ofFig. 3 Associated left calcaneum and astragalus of Arctostylopsfrom the Clarks Fork Basin in dorsal (a, c) and ventral (b, d) views.These tarsals form part of University of Michigan Museum ofPaleontology specimen UM 82359, a semi-articulated partial skel-eton reported previously by Bloch (1999), and are thus found indirect association with dental material. Note the striking similaritiesto the Palaeostylops tarsals, confirming the association of thesematerials found in isolationFig. 2 Diagram illustrating association of tarsal and dental speci-mens based on their dimensions. X-axis shows dimensions andnumber of all tarsal morphs at Subeng, and Y-axis shows dimensionsof corresponding dental specimens. Dimensions taken in millimetersand log-transformed. N = number of specimens for the specificmorph409Glires and associated taxa is followed throughout this paper.The Asian endemic eurymylids are basal Glires, andarctostylopids and Glires share the following derivedcharacters: absence of the dorsal astragalar foramen andthe roughly parallel orientation of the ectal and sustentac-ular facet on the astragalus (Meng et al. 2003). ThePalaeostylops tarsals differ from Rhombomylus by themoredorsoventrally oriented navicular facet on the astragalus,and by the more longitudinal ectal facet and the broader andmore dorsally facing fibular facet on the calcaneum.However, these features are derived characters sharedwith Pseudictops, a contemporaneous Asian endemicgliriform which also exhibits considerable overall similar-ities to Palaeostylops and Arctostylops (Sulimski 1968).Functional interpretationAlmost all of the distinctive tarsal characters cited above togroup Palaeostylops and Rhombomylus enhance lateralstability and suggest a cursorial or saltatorial locomotion(Tabuce et al. 2006). The more dorsoventral astragalarnavicular facet and the more longitudinal calcanealectofibular facet, which differentiate Palaeostylops fromRhombomylus, are observed in Pseudictops as well as inLagomorpha, and may therefore suggest that Palaeostylopswas even slightly more specialised than was Rhombomylus.Palaeostylops was thus moderately specialised for fastrunning or jumping in terrestrial conditions and possiblydigitigrade.Phylogenetic and biogeographic implicationsTraditional views of relationships have united Arctostylo-pidae with Notoungulata based on their strikingly similarteeth. The close similarity of the Palaeostylops andRhombomylus tarsals may therefore seem surprising espe-cially because of their strongly divergent dentitions.True Glires such as Rhombomylus are uniquely char-acterised by their specialised gnawing dentition withenlarged incisors and reduced dental formula. Basalgliriforms such as Anagale and Pseudictops, however,retain a complete dental formula with the upper and lowerdentition forming an evenly graded series, as is also thecase in arctostylopids. Moreover, Cifelli et al. (1989)proposed an arctostylopid dental morphotype, differingfrom advanced arctostylopids by weaker molar lophs, nomolar hypocone and p3 without metaconid. These char-acters would separate arctostylopids from Notoungulata,but are also present in basal Gliriformes (Meng et al. 2003),and may bridge the morphological gap with Gliriformes.Therefore, the arctostylopid dentition immediately pre-vents their association with true Glires but not necessarilywith non-gliroid Gliriformes.Tarsal morphology of arctostylopids described in thisstudy does not support their notoungulate affinities. Instead,it compares moderately well to the Asian gliriformPseudictops. Similarity is even greater to the Asian gliroidRhombomylus, for which the conservative tarsal mor-phology does not differ significantly from the gliriformstage (Meng et al. 2003; Asher et al. 2005). We suggestFig. 4 Dorsal view of left tarsals illustrating basal morphotypes of notoungulates, ungulates and different gliriform groups. Scale bar equals2 mm. Illustrations based on Sulimski (1968), Szalay (1977, 1985), Bleefeld and McKenna (1985), Meng et al. (2003) and on personalobservations410Arctostylopidaemay be a family of non-gliroid Gliriformes,conserving the primitive dental formula and the gliriformtarsal characters cited in the “Comparison” section. As inother groups during the expansive radiation of Gliriformes,the dentition may have evolved more rapidly than postcra-nial morphology, and adaptation to a particular type ofherbivory led to the evolution of molar lophs, divergentfrom other gliriforms.We propose that Arctostylopidae is part of a Palaeoceneradiation of endemic Asian Gliriformes. During the LatePalaeocene, arctostylopids migrated from Asia into NorthAmerica, giving rise to the genus Arctostylops, but neverachieved the diversity and success of their Asian relatives(Cifelli et al. 1989; Zack 2004). A comprehensive analysisthat includes both postcranial and dental morphology isneeded to really test the affinities proposed here. Likewise,description of the skeleton of Arctostylops is underway(Bloch et al. in preparation) and will provide a robust test ofthe hypotheses presented here.Acknowledgements The authors thank Christian de Muizon(MNHN, France), Peter Kondrashov (NMSU, USA) and LilianBergqvist (UFRJ, Brazil) for the discussions and access to referencematerials. At the RBINS, Julien Cillis produced the SEMmicrographs,and Stephane Berton prepared the drawings. This work was financiallysupported by projects MO/36/011 and BL/36/C12 of the BelgianFederal Science Policy Office (TS) and by the RF-Flanders (PM).ReferencesAsher RJ, Meng J, Wible JR, McKenna MC, Rougier GW,Dashzeveg D, Novacek MJ (2005) Stem Lagomorpha and theantiquity of Glires. Nature 307:1091–1094Beard KC (1998) East of Eden: Asia as an important center oftaxonomic origination in mammalian evolution. Bull CarnegieMus Nat Hist 34:5–39Bergqvist LP (1996) Reassociação do pós-crânio às espécies deungulados da bacia de S. J. de Itaboraí (Paleoceno), Estado doRio de Janeiro, e filogenia dos “Condylarthra” e ungulados sul-americanos com base no pós-crânio. Ph.D. Thesis, Universi-dade Federal do Rio Grande do Sul, Brazil, p 407Bleefeld AR, McKenna MC (1985) Skeletal integrity of Mimolagusrodens (Lagomorpha, Mammalia). Am Mus Novit 2806:1–5Bloch JI (1999) Partial skeleton of Arctostylops from the Paleoceneof Wyoming: arctostylopid–notoungulate relationship revisited.J Vertebr Paleontol 19:32ACifelli RL (1983a) The origin and affinities of the South AmericanCondylarthra and Early Tertiary Litopterna (Mammalia). AmMus Novit 2772:1–49Cifelli RL (1983b) Eutherian tarsals from the late Paleocene ofBrazil. Am Mus Nov 2761:1–31Cifelli RL (1993) The phylogeny of the native South Americanungulates. In: Szalay FS, Novacek MJ, McKenna MC (eds)Mammal phylogeny placentals. Springer, Berlin HeidelbergNew York, pp 195–216Cifelli RL, Schaff CR, McKenna MC (1989) The relationships ofthe Arctostylopidae (Mammalia): new data and interpretation.Bull Mus Comp Zool 152:1–44Gingerich PD (1985) South American mammals in the Paleocene ofNorth America. In: Stehli FG, Webb SD (eds) The greatAmerican biotic interchange. Plenum, New York, pp 123–137Kondrashov PE, Lucas SG (2004) Palaeostylops iturus from theUpper Paleocene of Mongolia and the status of Arctostylopida(Mammalia, Eutheria). New Mex Mus Natl Hist Sci Bull26:195–203Matthew WD (1915) A revision of the lower Eocene Wasatch andWind River faunas. Part IV. Entelonychia, Primates, andInsectivora (part). Bull Am Mus Nat Hist 34:429–483Matthew WD, Granger W (1925) Fauna and correlation of theGashato Formation of Mongolia. Am Mus Nov 189:1–12Meng J, Hu Y, Li C (2003) The osteology of Rhombomylus(Mammalia, Glires): implications for phylogeny and evolutionof Glires. Bull Am Mus Nat Hist 275:1–247Missiaen P, Smith T (2005) A new nyctitheriid insectivore fromInner Mongolia (China) and its implications for the origin ofthe Asian nyctitheriids. Acta Palaeont Pol 50:513–522Patterson B, Pascual R (1972) The fossil mammal fauna of SouthAmerica. In: Keast A, Erk FC, Glass BP (eds) Evolution,mammals and southern continents. State University of NewYork Press, Albany, New York, pp 247–309Schlosser M (1923) Säugetiere. In: Broili F, Schlosser M (eds)Grundzüge der Paläontologie (Paläozoologie) II. Abt: Vertebrata,neubeart. MR Oldenbourg, Munich, pp 402–689Smith T, Van Itterbeeck J, Missiaen P (2004) Oldest Plesiadapiform(Mammalia, Proprimates) of Asia and its paleobiogeographicalimplication with North America. CR Palevol 3:43–52Sulimski A (1968) Paleocene genus Pseudictops Matthew, Grangerand Simpson 1929 (Mammalia) and its revision. Palaeontol Pol19:101–129Szalay FS (1977) Phylogenetic relationships and a classification ofthe eutherian Mammalia. In: Hecht MK, Goody PC, Hecht BM(eds) Major patterns in vertebrate evolution. Plenum, NewYork, pp 315–374Szalay FS (1985) Rodent and lagomorph morphotype adaptations,origins and relationships: some postcranial attributes analyzed.In: Luckett WP, Hartenberger JL (eds) Evolutionary relation-ships among rodents: a multidisciplinary analysis. Plenum,New York, pp 83–132Tabuce R, Telles Antunes M, Smith R, Smith T (2006) Dentalvariability and tarsal morphology of the European Paleocene/Eocene mammal Microhyus. Acta Palaeontol Pol 51:37–52Ting S (1998) Paleocene and early Eocene land mammal ages ofAsia. Bull Carnegie Mus Nat Hist 34:124–147Wyss AR, Meng J (1996) Application of phylogenetic taxonomy topoorly resolved crown clades: a stem-modified node-baseddefinition of Rodentia. Syst Biol 45:559–568Zack SP (2004) An early Eocene Arctostylopid (Mammalia:Arctostylopida) from the Green River Basin, Wyoming.J Vertebr Paleontol 24:498–501411

Asian gliriform origin for arctostylopid mammals

Crossref

Missiaen, PieterWE13001999268515801001801631F6F01FAA-F0ED-11E1-A9DE-61C894A0A6B4

Archivsystem Ask23

https://biblio.ugent.be/publication/353125/file/1135902.pdf

Asian gliriform origin for arctostylopid mammals

Abstract

Similar works

Full text

Available Versions

Ghent University Academic Bibliography

Crossref

Archivsystem Ask23