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Zoogeographic implications of early Miocene rodentsfrom the Bugti beds, Baluchistan, Pakistan
ZOOGEOGRAPHIC IMPLICATIONS OF EARLY MIOCENE RODENTS FROM THE BUGTI BEDS, BALUCHISTAN, PAKISTAN by Louis L. JACOBS*, IQBAL UMER CHEEMA** and S.M. IBRAHIM SHAH**
Abstract Fossils from the Bugti beds, Baluchistan, Pakistan, suggest that the rodent fauna of the Indo-Pakistan subcontinent evolved in relative isolation from Europe between the middle Eocene and middle Miocene. Cricetid rodents entered South Asia after the time of the Bugti beds but before the Muree rodent fauna, which is similar to the lower Siwaliks.
R~sum~ Les fossiles provenant des couches de Bugti dans le Baluchistan (Pakistan) sugg6rent que la faune de rongeurs du sous-continent indo-pakistanais a 6volu~ depuis l'Eoc~ne moyen jusqu'au Miocene moyen de fa¢on relativement ind6pendante de celle de l'Europe. Les rongeurs cric6tid6s ont p~n6tr~ en Asie du Sud apr~s le d6p6t des couches de Bugti mais avant l'apparition de la faune de rongeurs de Muree qui est semblable ~ celle des Siwaliks inf6rieurs.
KEY-WORDS : RODENT, MIOCENE, BUGTI, PAKISTAN. MOTS-CLI~.S : RONGEURS, MIOCI~NE, BUGTI, PAKISTAN.
The record of Neogene land mammals from the Indo-Pakistan subcontinent is based mainly on fossils from the middle Miocene through Pleistocene Siwalik Group of Pakistan and northern India, and the early Miocene Bugti beds of Balushistan, western Pakistan (see fig. 1 for major collecting areas in Pakistan). The Siwalik Group is most significant in yielding the remains of the hominoid primates Ramapithecus, Sivapithecus, and Gigantopithecus. The Bugti beds have yielded a diverse fauna, including probably the
earliest known south Asian record of proboscideans, but no fossil hominoids. Extensive collections made since 1974 by joint Yale University-Geological Survey of Pakistan expeditions (YGSP) have improved the record of numerous vertebrate groups in the Siwaliks, notably the primates and smaller mammals such as rodents (1-6). The YGSP expeditions have also recovered the first fossil rodents known from the Bugti beds. The implications of similarities and differences of the Bugti rodent fauna to those of the
* National Museumsof Kenya, P.O. Box 40658, Nairobi. ** Pakistan National Museum of Natural History, Islamabad. C_~obios, n ° 15, fasc. 1
p. 101-103, 1 fig.
Lyon, f6vrier, 1981
--
Siwaliks, Europe and Africa are the subject of this note. A review of the Bugti fauna is being prepared by Mahmood Raza of the Pakistan National Museum of Natural History and Grant Meyer of the Ray Alf Museum, California.
Pakistan
Fig. 1 -
M a j o r collecting areas in Pakistan. A - Baluchistan, near Dera Bugti, early Miocene Bugti beds. B - Kohat, near B a n d a D a u d Shah, early to middle Miocene Murree Formation. C - P u n j a b , Potwar Plateau, middle Miocene to Pleistocene Siwalik Group, and Eocene K u l d a n a F o r m a t i o n of the bordering Kala Chitta Range. Principales r~gions du Pakistan ayant 6t6 prospect6es. A - Baluchistan, pr6s de Dera Bugti, couches de Bugti, Mioc6ne inf6rieur. B - Kohat, pr6s de B a n d a D a u d Shah, formation de Muree, Mioc6ne inf6rieur ~t moyen. C - P u n j a b , Plateau du Potwar, groupe de Siwalik, Mioc6ne m o y e n ~ Pleistoc6ne, et formation 6oc6ne de Kuldana appartenant/~ la chaine de Kala Chitta.
The age and correlation of the Bugti beds are based largely on the occurrence there of the proboscidean Gomphotherium, an African immigrant, plus some other large mammals, which suggest an early Miocene age. In 1978, one of us (I.U.C.) discovered a rich pocket of bone low in the section which has yielded a large sample of isolated rodent teeth. Preliminary inspection of these specimens suggests the presence of at least three distinct but related genera, none of which appear to be particularly closely related to rodents of the Siwalik fauna with the possible exception of the
1 0 2
--
lower Siwalik thryonomyid Paraulacodus. Some of the Bugti specimens are similar in dental pattern to rodents of the family Chappatimyidae described by S.T. Hussain et alii (7) from the Eocene of Pakistan and perhaps to phiomyids and thryonomyids. However, detailed comparaisons between Bugti rodents and chappatimyids and other families are incomplete. Even though the identifications of the Bugti rodents are preliminary, they are sufficient to justify the zoogeographic implications presented in this note. The rodent fauna from the lower Siwaliks near Chinji village (1) contains the cricetid rodent genera Copemys (Democricetodon) and Megacricetodon (but note that Siwalik cricetid samples are greatly improved and are undergoing revision), which are found in European Astaracian (middle Miocene) faunas such as Anwil. In addition, the lower Siwaliks contain the earliest known record of murid rodents (3), as well as rhizomyids, ctenodactylids, and a thryonomyid (8). Siwalik rodent samples in the type Nagri Formation (9) are dominated by murids. Endemic evolution is apparent in the succession of Siwalik murids, although some zoogeographic similarity with Europe is indicated by the presence of Progonomys and Parapodemus, and with Africa by the presence of Mus, Parapelomys, and Golunda (4). The rodent fauna of the Murree Formation (10) is intermediate in age and intermediate in composition between the Bugti and Siwalik faunas to the extent that it contains thryonomids, ctenodactylids, rhizomyids, cricetids including Spanocricetodon, and a representative of the enigmatic Bugti rodents. Early and middle Miocene rodent faunas of Europe contain many cricetids. Those from Africa also contain cricetids (although another sub-family), as well as thryonomyids. The distinctive nature of the Bugti rodent fauna, which lacks cricetids, confirms that south Asia was probably not the center of origin for cricetid rodents appearing suddenly in the middle Tertiary of Europe. The appearance of cricetids in southern Asia occurs after that of Gomphotherium between the time of deposition of the Bugti Beds and the Murree Formation, assuming that the fossil record of Pakistan accurately reflects these historical events.
The appearance of proboscideans in the Bugti sequence signals a major faunal intercourse with Africa. From the early Miocene onward, some amount of faunal exchange occurred intermittently between south Asia and Africa, and between south Asia and Europe. However, the faunal exchange with
--
103
neither Africa nor E u r o p e was ever very extensive as the Siwalik f a u n a remains more-or-less distinct and contains endemic elements. H o m i n o i d primates ente-
--
red south Asia after the deposition o f the Bugti beds, p r o b a b l y in the middle Miocene, at a b o u t the same time as cricetid rodents migrated into south Asia.
References
(1) PILBEAM D. et alii - N a t u r e , London, 270, 1977, p. 684-689.
(6) JACOBS L.L. - Cas. Miner. Geol. (Praha), 24, 1979, p. 301-304.
(2) PILBEAM D. et alii - N a t u r e , London, 270, 1977, p. 689-695.
(7) HUSSAIN S.T. et alii - K o n . N e d e r L A k a d . van W e t e n s c h a p p e n , Proc., B 81, 1978, p. 74-11Z
(3) JACOBS L.L. - Paleobios, Berkeley, 25, 1977, p. 1-11.
(8) BLACK C.C. - P a l a e o n t o l o g y , Oxford, 15, 1972, p. 238-266.
(4) JACOBS L.L. - M u s e u m o f N o r t h e r n A r i z o n a Bulletin, Flagstaff, 52, 1978, p. 1-03. (5) PILBEAM D.R. et alii (edit.) - Postilla, New Haven, 179, 1979, p. 1-45.
(9) FATMI A.N. (edit.) Quetta, 10, 1973, p. 1-80.
Mem.
GeoL Surv. Pakistan,
(10) DE BRUIJN H. et alii - K o n . NederL A k a d . van W e t e n s c h a p p e n , Proe., B 84, 1981, p. 71-99.
Abstract Fossils from the Bugti beds, Baluchistan, Pakistan, suggest that the rodent fauna of the Indo-Pakistan subcontinent evolved in relative isolation from Europe between the middle Eocene and middle Miocene. Cricetid rodents entered South Asia after the time of the Bugti beds but before the Muree rodent fauna, which is similar to the lower Siwaliks.
R~sum~ Les fossiles provenant des couches de Bugti dans le Baluchistan (Pakistan) sugg6rent que la faune de rongeurs du sous-continent indo-pakistanais a 6volu~ depuis l'Eoc~ne moyen jusqu'au Miocene moyen de fa¢on relativement ind6pendante de celle de l'Europe. Les rongeurs cric6tid6s ont p~n6tr~ en Asie du Sud apr~s le d6p6t des couches de Bugti mais avant l'apparition de la faune de rongeurs de Muree qui est semblable ~ celle des Siwaliks inf6rieurs.
KEY-WORDS : RODENT, MIOCENE, BUGTI, PAKISTAN. MOTS-CLI~.S : RONGEURS, MIOCI~NE, BUGTI, PAKISTAN.
The record of Neogene land mammals from the Indo-Pakistan subcontinent is based mainly on fossils from the middle Miocene through Pleistocene Siwalik Group of Pakistan and northern India, and the early Miocene Bugti beds of Balushistan, western Pakistan (see fig. 1 for major collecting areas in Pakistan). The Siwalik Group is most significant in yielding the remains of the hominoid primates Ramapithecus, Sivapithecus, and Gigantopithecus. The Bugti beds have yielded a diverse fauna, including probably the
earliest known south Asian record of proboscideans, but no fossil hominoids. Extensive collections made since 1974 by joint Yale University-Geological Survey of Pakistan expeditions (YGSP) have improved the record of numerous vertebrate groups in the Siwaliks, notably the primates and smaller mammals such as rodents (1-6). The YGSP expeditions have also recovered the first fossil rodents known from the Bugti beds. The implications of similarities and differences of the Bugti rodent fauna to those of the
* National Museumsof Kenya, P.O. Box 40658, Nairobi. ** Pakistan National Museum of Natural History, Islamabad. C_~obios, n ° 15, fasc. 1
p. 101-103, 1 fig.
Lyon, f6vrier, 1981
--
Siwaliks, Europe and Africa are the subject of this note. A review of the Bugti fauna is being prepared by Mahmood Raza of the Pakistan National Museum of Natural History and Grant Meyer of the Ray Alf Museum, California.
Pakistan
Fig. 1 -
M a j o r collecting areas in Pakistan. A - Baluchistan, near Dera Bugti, early Miocene Bugti beds. B - Kohat, near B a n d a D a u d Shah, early to middle Miocene Murree Formation. C - P u n j a b , Potwar Plateau, middle Miocene to Pleistocene Siwalik Group, and Eocene K u l d a n a F o r m a t i o n of the bordering Kala Chitta Range. Principales r~gions du Pakistan ayant 6t6 prospect6es. A - Baluchistan, pr6s de Dera Bugti, couches de Bugti, Mioc6ne inf6rieur. B - Kohat, pr6s de B a n d a D a u d Shah, formation de Muree, Mioc6ne inf6rieur ~t moyen. C - P u n j a b , Plateau du Potwar, groupe de Siwalik, Mioc6ne m o y e n ~ Pleistoc6ne, et formation 6oc6ne de Kuldana appartenant/~ la chaine de Kala Chitta.
The age and correlation of the Bugti beds are based largely on the occurrence there of the proboscidean Gomphotherium, an African immigrant, plus some other large mammals, which suggest an early Miocene age. In 1978, one of us (I.U.C.) discovered a rich pocket of bone low in the section which has yielded a large sample of isolated rodent teeth. Preliminary inspection of these specimens suggests the presence of at least three distinct but related genera, none of which appear to be particularly closely related to rodents of the Siwalik fauna with the possible exception of the
1 0 2
--
lower Siwalik thryonomyid Paraulacodus. Some of the Bugti specimens are similar in dental pattern to rodents of the family Chappatimyidae described by S.T. Hussain et alii (7) from the Eocene of Pakistan and perhaps to phiomyids and thryonomyids. However, detailed comparaisons between Bugti rodents and chappatimyids and other families are incomplete. Even though the identifications of the Bugti rodents are preliminary, they are sufficient to justify the zoogeographic implications presented in this note. The rodent fauna from the lower Siwaliks near Chinji village (1) contains the cricetid rodent genera Copemys (Democricetodon) and Megacricetodon (but note that Siwalik cricetid samples are greatly improved and are undergoing revision), which are found in European Astaracian (middle Miocene) faunas such as Anwil. In addition, the lower Siwaliks contain the earliest known record of murid rodents (3), as well as rhizomyids, ctenodactylids, and a thryonomyid (8). Siwalik rodent samples in the type Nagri Formation (9) are dominated by murids. Endemic evolution is apparent in the succession of Siwalik murids, although some zoogeographic similarity with Europe is indicated by the presence of Progonomys and Parapodemus, and with Africa by the presence of Mus, Parapelomys, and Golunda (4). The rodent fauna of the Murree Formation (10) is intermediate in age and intermediate in composition between the Bugti and Siwalik faunas to the extent that it contains thryonomids, ctenodactylids, rhizomyids, cricetids including Spanocricetodon, and a representative of the enigmatic Bugti rodents. Early and middle Miocene rodent faunas of Europe contain many cricetids. Those from Africa also contain cricetids (although another sub-family), as well as thryonomyids. The distinctive nature of the Bugti rodent fauna, which lacks cricetids, confirms that south Asia was probably not the center of origin for cricetid rodents appearing suddenly in the middle Tertiary of Europe. The appearance of cricetids in southern Asia occurs after that of Gomphotherium between the time of deposition of the Bugti Beds and the Murree Formation, assuming that the fossil record of Pakistan accurately reflects these historical events.
The appearance of proboscideans in the Bugti sequence signals a major faunal intercourse with Africa. From the early Miocene onward, some amount of faunal exchange occurred intermittently between south Asia and Africa, and between south Asia and Europe. However, the faunal exchange with
--
103
neither Africa nor E u r o p e was ever very extensive as the Siwalik f a u n a remains more-or-less distinct and contains endemic elements. H o m i n o i d primates ente-
--
red south Asia after the deposition o f the Bugti beds, p r o b a b l y in the middle Miocene, at a b o u t the same time as cricetid rodents migrated into south Asia.
References
(1) PILBEAM D. et alii - N a t u r e , London, 270, 1977, p. 684-689.
(6) JACOBS L.L. - Cas. Miner. Geol. (Praha), 24, 1979, p. 301-304.
(2) PILBEAM D. et alii - N a t u r e , London, 270, 1977, p. 689-695.
(7) HUSSAIN S.T. et alii - K o n . N e d e r L A k a d . van W e t e n s c h a p p e n , Proc., B 81, 1978, p. 74-11Z
(3) JACOBS L.L. - Paleobios, Berkeley, 25, 1977, p. 1-11.
(8) BLACK C.C. - P a l a e o n t o l o g y , Oxford, 15, 1972, p. 238-266.
(4) JACOBS L.L. - M u s e u m o f N o r t h e r n A r i z o n a Bulletin, Flagstaff, 52, 1978, p. 1-03. (5) PILBEAM D.R. et alii (edit.) - Postilla, New Haven, 179, 1979, p. 1-45.
(9) FATMI A.N. (edit.) Quetta, 10, 1973, p. 1-80.
Mem.
GeoL Surv. Pakistan,
(10) DE BRUIJN H. et alii - K o n . NederL A k a d . van W e t e n s c h a p p e n , Proe., B 84, 1981, p. 71-99.