On Neogene Rodents of Eurasia: Distribution and Migrations
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Pierre Mein Université Lyon I On Neogene rodents of Eurasia: distribution and migrations Mein, P., 2003 - On Neogene rodents of Eurasia: distributions and migrations - in: Reumer, J.W.F. & Wessels, W. (eds.) - DISTRIBUTION AND MIGRATION OF TERTIARY MAMMALS IN EURASIA. A VOLU- ME IN HONOUR OF HANS DE BRUIJN - DEINSEA 10: 407-418 [ISSN 0923-9308] Published 1 December 2003 The most recently published papers dealing with Eurasian rodents were compiled. The importan- ce of dispersal migrations for our understanding of Eurasian faunal dynamics is stressed on the basis of selected rodent taxa. The rodent genera appeared in Asia generally earlier than their European relatives, evidences for the way of migrations. Many migrations may not have been pre- served in the fossil record; however, most of them seem to originate in Asia, even if two or three examples show the contrary. Four main dispersal centres (China, Kazakhstan, Pakistan and Anatolia) were important during Neogene times. Correspondence: Université Lyon I, Géode, 27-43 Boulevard du 11 Novembre, 69622 Villeurbanne Cedex France; e-mail: [email protected] Keywords: Neogene, Rodentia, migration, Eurasia INTRODUCTION Theridomyidae and Rhizospalacidae. Asian rodents are more diversified than Unfortunately, these two families are unk- European ones due to the smaller size of the nown in Asia, and only geomagnetic data in latter area and the smaller latitudinal varia- calibrated sections can mark the beginning of tion. Therefore, Asia acted as a faunal disper- the Neogene, except in Pakistan where the sal centre for Europe during the Neogene; the extinction of the Baluchimyinae seems con- great majority of the exchanges were migra- temporaneous with the Oligocene-Miocene tions from Asia into Europe (as in Paleogene boundary. times). Dispersal events from North America Western Europe can be seen as a trap for or Africa are rare and correlated with impor- the East-West immigrants, because of its tant tectonic or eustatic changes. Successful position at the Western end of the Eurasian immigration may result in the appearance of continent and its triangular shape. Sometimes new families on the new continent. On the the temporal and spatial distribution of some Eurasian continent however, important bar- invaders is very small. For example, the riers do not exist and small ecological varia- genus Celadensia is only known from a single tions initiate large changes in the distribution latest Miocene locality in Italy, and from of the faunas. Therefore, migrations were Teruel (Spain) during a short period at the numerous and led often to a change on genus Miocene-Pliocene transition. On the other level. hand, some immigrants settle and undergo The beginning of the Neogene in Asia is evolutionary radiation. This is illustrated by difficult to identify. In Europe, the Paleogene- the successful cricetid Democricetodon (with Neogene boundary is characterized in the its probable origin in Anatolia), which is rodents by the disappearance of the ancestral to several genera in Western 407 DISTRIBUTION AND MIGRATION OF TERTIARY MAMMALS IN EURASIA DEINSEA 10, 2003 Europe. So, Western Europe periodically Sardinian ctenodactylids. So Prosayimys received faunal invasions, but it is difficult to could be the ancestor of the Sardinian cteno- localize the sources areas, which could be dactylids. During the Miocene, ctenodactylids Eastern Europe, Central Asia, South-Western disappeared from Asia. The youngest form Asia, or the Far East. During the last decade, Sayimys chinjiensis Baskin, 1996, is known intensive field campaigns allowed to charac- from the Upper Vallesian of Pakistan. At the terize some independent dispersal centres in beginning of the Middle Miocene Sayimys Asia. Four such areas are now well known intermedius (SEN & THOMAS, 1979) migrated (corresponding to the main paleontological to Rotem (Israel), to Al Sarrar (Saudi Arabia) field activities): Mongolia, Kazakhstan, and Djebel Zelten (Lybia, Africa). Cteno- Anatolia, and Pakistan. dactyloidea were also represented during Rodents, which are the most numerous Paleogene times in Asia by the Chappa- mammals, expanded widely since the timyids. An offshoot of this last group, the Oligocene. Hartenberger (1998) gives a chart Baluchimyinae, survived until the earliest showing the major subdivisions and lineages. Miocene (Flynn et al. 1986, Flynn & Cheema During the Neogene epoch, a few new groups 1994). The recent discovery of a representati- diversified. Some of these new groups, espe- ve of Baluchimys from an Eocene level from cially the Muroidea, were very successful and Thailand (Marivaux et al. 2000) has demon- produced many species and genera. McKenna strated an Eocene origin for the & Bell (1997) have realized a remarkable Baluchimyidae. review of all mammals at the supragenic Diatomyidae (Mein & Ginsburg 1997) con- level, using a strict cladistic classification. In stitute an independent Asiatic group of the this case, the Neogene innovations are limi- ctenodactyloids, they originated in Pakistan, ted to some subfamilies. This classification is and have two successive genera Fallomus not convenient, because about fifty per cent (FLYNN et al., 1986) and Diatomys LI, 1974. of the rodents are part of the huge murid Flynn (2000) shows several morphological family. In this paper, the groupings of rodents intermediate steps between these two diato- used are those that are usually employed, but myid genera. Their molars are convergent they are largely informal, because affiliations with those of Megapedetes. During the Early of many groups have not been solved satis- and Middle Miocene, this group is known factorily. I will focus on those groups whose from Laddak, Thailand, China and Japan. The migrations have been demonstrated; for exa- last occurrence is in the Pakistani site Y-797 mple, some old rodents like the aplodontids (Nagri formation; 10.6 Ma). living in China and in Central Europe during Pedetidae are typically an African rodent the early Miocene have no close relationship, family, but they are not documented during and will, therefore not be discussed. the Paleogene times. Three genera (Parapedetes, Megapedetes and a new unde- NON-MUROID RODENTS scribed genus) occurred simultaneously The Neogene European Ctenodactylidae have during the Early Miocene of East and South been recently reviewed by De Bruijn (1999), Africa. Among them, only Megapedetes can who pointed to the fact that the Sardinian cte- be occasionally found in the Middle Miocene nodactylids show a tooth structure too com- of the South Eastern Mediterranean region; plicated to be derived from a Sayimys pattern. they are known from: Rotem (Israel, MN4; But the genus Prosayimys from the Upper Wood & Goldsmith 1998), Chios (Greece, Chirtawarta formation of Zinda Pir Dome MN5; Tobien 1968) and Al Sarrar (Saudi Pakistan (estimated age 20 Ma; Baskin 1996) Arabia, MN5; Thomas et al. 1982). has preserved the metalophid II, which is Megapedetes aegaeus is the last known always present in the Early Miocene Asiatic form of the Pedetids, known from 408 MEIN: Neogene rodents of Eurasia Bayrak Tepe 1 (MN7-8; Sen 1977). European origin is clear, because it is known Another African group, the Thryonomyidae, from Europe since MP25 and perhaps earlier. which are hystricognath rodents, occurs occa- Probably by the way of Anatolia, Dryomys sionally during the Miocene in Asia. Two dif- went to Africa during the Middle Miocene, ferent migrations reached the Indian subcon- where it can be found until the Lower tinent (Flynn & Winkler 1994). The first Turolian. The recent genus Graphiurus could with the small Kochalia DE BRUIJN, 1986, is be a descendant of this African Dryomys. known from 11.3 to 12.5 Ma and the second Myomimus was present in Pakistan from 13.8 with the large Paraulacodus HINTON, 1933, Ma (HGSP 107, Banda Daud Shah) and which is present only during a brief episode occurs now in Iran and Turkmenistan. from 12.9 to 12.5 Ma. The myrmecophagous Glirid Plioselevinia There is nothing to add to the story of the is known from MN15 of Weze (Poland) and Castoridae, described in detail by Hugueney Ivanovce (Czech Republic) and from MN16 (1999), who shows that during the Neogene, of Hajnacka (Czech Republic) (Fejfar & the same genera of this group lived in Asia Heinrich 1985). Its recent relatives live now and Europe. However, Bendukidze (1997) in Kazakhstan. So, the migration of this mentions two genera (Capacikala and group has been from West to East. Capatanka) of American origin from the Sciuroidea were widely spread upon the Early Miocene of Kazakhstan (but now, the whole Eurasiatic continent at the end of the latter is included in the genus Palaeocastor). Oligocene. During the Neogene, their diversi- Gliridae belong to an old rodent radiation fication increased. Some ground squirrels present in Eurasia since the Eocene. Many invaded Africa in the Early Miocene just after genera are exclusively European forms and the collision between African and Eurasiatic the first idea supposed that Europe was the plates. We can observe two different routes only dispersal centre for Glirids. However, for the migrations between Europe and Asia. the Oligocene-Early Miocene Glirids from The first is shown by Atlantoxerus, which is Anatolia exhibit a great number of forms and present at the beginning of Neogene of are sometimes older than the European occur- China, in the Suosuoquan Formation (MN1, rences (Ünay, 1994). For example, Glis has Qiu et al. 1999). This genus appeared in been recorded from the Middle Oligocene of Europe only in MN4 (de Bruijn 1999) and Anatolia (MP25) but is only known since persisted until the Middle Pliocene (MN15). MN4 in Europe. Similarly, Glirulus is known In Asia, the taxon disappeared after MN14 from Harami-1 (MN2) in Anatolia, and arri- (Bilike, Qiu & Storch 2000). In the same ved in Europe in MN4. Myomimus existed in group, Sciurus is supposed to arrive from Keseköy (MN3) and Çandir (MN6), but arri- North America during the Lower Pliocene. ved in MN9 in Europe (Daams 1999).