- Email: [email protected]
A new fish fauna from the Jurassic of Vietnam
Journal of Asian Earth Sciences 19 (2001) 641±647
www.elsevier.com/locate/jseaes
A new ®sh fauna from the Jurassic of Vietnam A. Filleul a,*, D. Vu Khuc b a
Laboratoire de PaleÂontologie, MuseÂum National d'Histoire Naturelle, UMR 9569 du CNRS, 8, rue Buffon, 75005 Paris, France DeÂpartement de GeÂologie et de MineÂraux, MuseÂe GeÂologique (Bao Tang Dia Chat), 6, Pham Ngu Lao Street, Hanoi, Viet Nam
b
Received 29 March 2000; revised 28 September 2000; accepted 24 October 2000
Abstract A ®sh fauna is recorded here for the ®rst time from the Upper Jurassic Long Binh Formation of Vietnam. The material consists mainly of small, rarely articulated specimens of actinopterygian ®sh. Although poorly preserved, this material provides evidence for three different taxa: a head of an indeterminate basal actinopterygian, some nearly complete specimens of indeterminate neopterygians and a tail of a chondrostean, which is certainly the most interesting fossil in this fauna. The absence of teleosts (except for possible ªPholidophoriformesº) in this fauna suggests that the Long Binh Formation is older than the Cretaceous and better agrees with a Jurassic age. q 2001 Elsevier Science Ltd. All rights reserved. Keywords: Jurassic; Fish fauna; Vietnam
1. Introduction Mesozoic ®shes are extremely rare in Southeast Asia and are mainly represented by isolated remains (scales, teeth, dermal bones) from the Upper Triassic Huai Hin Lat Formation of Thailand (Martin and Ingavat, 1982), the Lower Jurassic Yefbie Formation of Misool Island, Indonesia (Janvier and Hasibuan, 1985), the Upper Jurassic to Cretaceous Phu Kradung, Phra Wihan, Sao Khua and Khoh Kruat Formations of ThaõÈland (Buffetaut and Ingavat, 1985), and the Lower Cretaceous of Laos (M. VeÂran, personal communication). With the exception of the Lepidotes-like scales from Misool Island, all these ®sh remains are assumed to occur in fresh water deposits. In this paper, we report on the ®rst occurrence of a ®sh fauna, represended by partly articulated specimens belonging to at least three major actinopterygian taxa, from Mesozoic deposits of southern Vietnam. This ®sh fauna is potentially the most remarkable one ever found in southeast Asia, and it is probable that further discovery of unweathered material in this locality would provide important palaeobiogeographical data. The material described herein was discovered by Dr Le Thi Dinh of Hi Chi Minh City National University, who donated it to the Geological Museum (Bao Tang Dia Chat), 6 Pham Ngu Lao,
Hanoi, where it is collectively registered with the number BT 201. 1.1. Geographical and geological setting The Long Binh hills are situated about 17 km east of Ho Chi Minh City, east of the highway N81 running to the northern provinces of Vietnam (Fig. 1). The ®sh material has been collected in the Member 3 of the Long Binh Formation, exposed on the northern side Ho Chi Minh City. The Long Binh hills are formed by Mesozoic volcano±sedimentary rocks, which were referred to the Deo Bao Loc Formation and regarded as Late Jurassic to Early Cretaceous in age by NguyeÃn Kinh Quoc (1989). Typically, the Deo Bao Loc Formation mainly consists of andesite, with minor tuff interbeds, and its basal part includes continental red beds. Bui Phu My and Duong Van Cau (1991) revisited the Long Binh exposures and referred them to a new formation, the Long Binh Formation, which they regarded as Late Jurassic in age. The exposures of this formation in the Long Binh hills are very poor and their description is, therefore, based essentially on the borehole core N8918, drilled in the same area. They described the Long Binh Formation as about 420 m thick and composed of the four following members (in ascending order):
* Corresponding author. Tel.: 133-1407-93004; fax: 133-1407-93580. E-mail address: ®[email protected] (A. Filleul). 1367-9120/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved. PII: S 1367-912 0(00)00060-2
Member 1 (117 m): Andesite, andesitobasalt, interbedded with some marls and thin-bedded clayey cherts in the upper part.
642
A. Filleul, D. Vu Khuc / Journal of Asian Earth Sciences 19 (2001) 641±647
morphs referred to Classipollis sp., Osmundacidites sp. and Leiotriletes sp. Member 4 (65±75 m): Red tuffaceous siltstone passing upward to dacite and rhyolite. Near the Binh An village, situated 2 km north of the Long Binh hills, the andesite of the lowermost member (Member 1) of the Long Binh Formation lies unconformably upon sandstone layers which have yielded the ammonites Coroniceras sp. and Asteroceras sp. and are thus dated as Lower Jurassic. The andesite of this locality is penetrated by the granitoids of the Dinh Quan complex, which are radiometrically dated of 140 Ma, that is, Lower Cretaceous. This indicates, at any rate, that the base of the Long Binh Formation is older that the Early Cretaceous.
2. Systematic study
Fig. 1. Locality map.
Three different taxa have been recognized among the specimens. However, their completeness and the poor preservation prevent us from giving a much precise taxonomic determination. 2.1. Form 1
Member 2 (120 m): Tuffaceous lava, tuffaceous agglomerate interbedded in the upper part with some coaly, cherty shale and siltstone containing Estheria sp. Member 3 (115 m): Clayey shale, banded coaly shale with interbeds of marl. The clayey shale of this member has yielded the fossil ®shes decribed herein. The coaly shale have yielded some plant remains referred to Zamites sp., Pagiophyllum sp. and Dicksonia sp., as well as sporo-
Actinopterygii gen. and sp. indet. This taxon is represented by a unique and badly preserved specimen (Fig. 2). The specimen consists of a head with the mouth wide open and part of the trunk. It is not possible to observe any wellpreserved bone. The orbit is, however, visible and placed anteriorly as in lower actinopterygians and it recalls the head shape of a ªpaleonisciformº. The mouth opening seems very large as in ªpaleonisciformsº that exhibit a
Fig. 2. Head and part of the trunk of an undetermined actinopterygian (form 1).
A. Filleul, D. Vu Khuc / Journal of Asian Earth Sciences 19 (2001) 641±647
643
Fig. 3. Neopterygian gen. and sp. indet. One of the most complete specimens.
very posterior quadrate±lower jaw articulation. The body is covered with small scales, whose shape remains unclear. 2.2. Form 2 Neopterygii gen. and sp. indet. (Figs. 3±5). This taxon is widely represented in the fauna (12 specimens). Some of the specimens are complete but none of them exhibits a wellpreserved head. The tail, however, provides some information. Measurements for this form are summarized in Table 1. The body is entirely covered by rhomboid scales. The ®sh has a unique and unspinous dorsal ®n. The pelvic ®ns are in abdominal position. Although no bones of the head are preserved enough to show neopterygians synapomorphies, the overall proportion and the position of the orbit (not anteriorly placed) better ®t neopterygians than lower acti-
nopterygians. The caudal ®n presents fewer rays than in lower actinopterygians. Patterson (1973) proposed the following character as a synapomorphy of neopterygians: caudal ®n rays equal in number to their supports. Although the hypurals are not preserved in our material, the number of rays is consistent with the hypothesis that the specimens are Neopterygii. The caudal ®n is weakly heterocercal. The inner rays are more spaced out than the outer rays. The rhomboid scales form rows that extend posteriorly in both caudal lobes but extent further in the superior lobe. Six basal fulcra are present in the upper lobe. The scale covering prevents us from seeing the caudal endoskeleton, which is of primary importance in actinopterygians systematics. It is dif®cult to know to which group form 2 could belong among neopterygians without information from this part of the body. One must notice, however, that the caudal exoskeleton is very similar in shape and displays
Fig. 4. Drawing of the tail (form 2). a.f: anal ®n; l.l: lower lobe; u.l: upper lobe.
644
A. Filleul, D. Vu Khuc / Journal of Asian Earth Sciences 19 (2001) 641±647
Fig. 5. Drawing of the tail showing the fulcra of the upper lobe (form 2). f: fulcra.
the same characteristics as that of some ªpholidophoriformsº. It is especially similar to Pholidophorus as ®gured by Patterson (1968). The body proportions and size are also consistent with the hypothesis that the form 2 is a pholidophorid. Despite this resemblance, it cannot be referred to the pholidophorids as long as the endoskeleton and the head are not available. These parts are widely used to determine relationships of the pholidiphorids (see Nybelin, 1966). Here, we can only propose that the form 2 is a neopterygian, and that, among this group, it looks extremely similar to ªpholidoforiformsº. We cannot go further without better-preserved material. 2.3. Form 3 Chondrostei (sensu Grande and Bemis, 1996) gen. and sp. indet. (Figs. 6 and 7). This taxon is represented by a unique and incomplete specimen but far better preserved than the others. The posterior part of the body is visible from the dorsal ®n to the end of the tail. The body lacks scales except in the upper caudal lobe, which is covered laterally with a sheet of small scales. This feature is a synapomorphy of the Chondrostei (Grande and Bemis, 1996) and has been discussed in Bemis et al. (1997). Dorsal and anal ®ns are situated posteriorly and very close to the tail. The dorsal ®n is, however, anterior to the level of the anal ®n. Two series of radials are visible in the anal ®n but they have been
40 mm 36.6 mm 10.8 mm 4.2 mm 20 mm 30 mm 20.3 mm 11.2 mm 10.8 mm
3. Discussion 3.1. Stratigraphic implications
Table 1 Morphometic characteristics of form 2 Total length Standard length Maximum height Peduncle height Predorsal length Preanal length Prepelvic length Prepectoral length Head length
dislodged and are not lying at the same angle. Thirteen proximal radials and six middle radials are preserved. The middle radials are much more elongated than the proximal ones. Haemal spines and supraneurals (see Grande and Bemis, 1991 for the use of the term supraneurals instead of neural spines) display an elongated shape and are backwardly inclined. The tail is heterocercal. The extremity of the upper lobe is displaced and lies below its normal location. There is one dorsal caudal scute followed by numerous elongated fulcra. Thirty-three fulcra are preserved but there were probably more. Six supraneurals lie below the dorsal scute and the ®rst fulcrum. The series of supraneurals must have extended more posteriorly but no supraneurals are preserved posterior to the level of the second fulcrum. The ®n rays of the lower lobe are better preserved than the upper ones. They are dichotomous and supported by haemal spines and hypurals. Nine of the supports are visible but it is not possible to differentiate the last haemal spines from the ®rst hypurals. In addition to these three forms, isolated elements have been collected such as a nearly complete pectoral ®n (supposedly a non-neopterygian actinopterygian) and isolated bones, which remain undetermined but, however, remind bones of a chondrostean head (Figs. 8 and 9).
100% 90% 27% 10.4% 50% 75% 50% 27.9% 27%
The Long Binh Hills ichthyofauna lacks teleost ®shes other than possible pholidophorids. During the Cretaceous, most of the higher teleosts taxa were present and widespread (see Patterson 1993). Teleosts are so widespread in the known Cretaceous fauna that their absence in the Long Binh formation suggests that the fauna is not Cretaceous but Jurassic as proposed by Bui Phu My and Duong Van Cau (1991). Nevertheless, such an absence does not constitute an evidence for dating the locality but just an indication.
A. Filleul, D. Vu Khuc / Journal of Asian Earth Sciences 19 (2001) 641±647
645
Fig. 6. Tail of a chondrostean (form 3).
There is no contradiction between the presence of chondrosteans and the assumption that the locality is Jurassic in age. Acipenseriformes have been found in many Late Jurassic localities of the northern hemisphere (Grande and Bemis, 1991). The presence of the form 1 is consistent with the Jurassic age since lower actinopterygians (i.e. non-neopterygians) are known up to the Cretaceous. Pholidophorids are also known up to the Cretaceous (Patterson, 1993).
Jurassic and the Early Cretaceous of China (Jin et al., 1995). The phylogeny of the Chondrostei is mainly supported by characters from the head since the caudal skeleton remains plesiomorphic for most of the ingroup taxa. Therefore, the form 3 could be related to any taxon from Birgeria to Polyodon (see Grande and Bemis, 1996) except Acipenseridae because it lacks the characteristic lateral row of scutes.
4. Conclusion 3.2. Systematics implications The form 3 is the only one that is preserved enough to have a systematic interest. This is one of the earliest Chondrostei ever found if the locality is effectively Jurassic in age. Fossils of Acipenseriformes are known from the Late
The survey of the ichthyofauna agrees with the Jurassic age of the locality. Further ®eld investigation would be necessary to ®nd new complete specimens of the form 3, which would be of primary interest in the phylogenetic study of the Chondrostei.
Fig. 7. Drawing of the specimen representing the form 3. d.c.f.: dorsal caudal fulcra; d.s.: dorsal scute; h.s.: haemal spine; hyp: hypural; m.r.: middle radials; p.r.: proximal radials; r.sc: rhomboid scales of the upper lobe; Sn: supraneurals.
646
A. Filleul, D. Vu Khuc / Journal of Asian Earth Sciences 19 (2001) 641±647
Fig. 8. Pectoral ®n of an indeterminate actinopterygian.
Fig. 9. Possible chondrostean unidenti®ed isolated bones.
A. Filleul, D. Vu Khuc / Journal of Asian Earth Sciences 19 (2001) 641±647
Acknowledgements We would like to thank Dr Philippe Janvier for reading and making useful comments on the manuscript. D. Serrette made the photographs, H. Lavina prepared the map and F. Pilard some of the drawings. References Bemis, W.E., Findeis, E.K., Grande, L., 1997. An overview of Acipenseriformes. Environmental Biolology of Fishes 48, 25±71. Buffetaut, E., Ingavat, R., 1985. The Mesozoic vertebrates of Thailand. Scienti®c American 253, 80±87. Bui Phu My, Duong Van Cau, 1991. He tang Long Binh [Long Binh Formation]. Dia ly, Dia Chat, Moi truong, HoChiMinh City 1, 58±61. Grande, L., Bemis, W.E., 1991. Osteology and phylogenetic relationships of fossil and recent paddle®shes (Polyodontidae) with comments on the interrelationships of Acipenseriformes. Journal of Vertebrate Paleontology 11 (1), 1±121. Grande, L., Bemis, W.E., 1996. Interrelationships of Acipenseriformes, with comments on ªChondrosteiº. In: Stiassny, M.L.J., Parenti, L.R., Johnson, G.D. (Eds.). Interrelationships of Fishes, Academic Press, San Diego, pp. 85±115.
647
Janvier, P., Hasibuan, F., 1985. Lepidotes remains from the Lower Jurassic Yefbie Formation of Misool Island, Indonesia, Bulletin of Geology Resources and Development Center, Bandoeng. Jin, Fan, Tian, Yanping, Yang, Youshi, Deng, Shaoying, 1995. An early fossil sturgeon (Acipenseriformes, Peipiaosteidae) from Fengning of Hebei, China. Vertebrata PalAsiatica 33, 1±85. Martin, M., Ingavat, R., 1982. First record of an Upper Triassic ceratodontid (Dipnoi, Ceratodontiformes) in Thailand and its paleogegraphic signi®cance. Geobios 15, 111±114. Quoc, N.K., 1989. Deo Bao Loc formation. In: Khuc, V., My, B.P. (Eds.). Dia Chat, VieÃt Nam, Tap 1: Dia Tang, (Geology of Vietnam, Part 1: Stratigraphy), Gen. Dept. Mines Geol, Ha Noi (378 pp.). Nybelin, O., 1966. On certain Triassic and Liassic representatives of the family Pholidophoridae s.str. Bulletin of the British Museum (Natural History), Geology 11 (8), 354±432. Patterson, C., 1968. The caudal skeleton in lower Liassic pholidophorid ®shes. Bulletin of the British Museum (Natural History), Geology 16 (5), 203±239. Patterson, C., 1973. Interrelationships of holosteans. In: Greenwood, P.H., Miles, R.S., Patterson, C. (Eds.). Interrelationships of Fishes, Academic Press, London, pp. 233±305. Patterson, C., 1993. Osteichthyes: Teleostei. In: Benton, M.J. (Ed.). The Fossil Record 2, Chapman and Hall, London, pp. 622±656.
www.elsevier.com/locate/jseaes
A new ®sh fauna from the Jurassic of Vietnam A. Filleul a,*, D. Vu Khuc b a
Laboratoire de PaleÂontologie, MuseÂum National d'Histoire Naturelle, UMR 9569 du CNRS, 8, rue Buffon, 75005 Paris, France DeÂpartement de GeÂologie et de MineÂraux, MuseÂe GeÂologique (Bao Tang Dia Chat), 6, Pham Ngu Lao Street, Hanoi, Viet Nam
b
Received 29 March 2000; revised 28 September 2000; accepted 24 October 2000
Abstract A ®sh fauna is recorded here for the ®rst time from the Upper Jurassic Long Binh Formation of Vietnam. The material consists mainly of small, rarely articulated specimens of actinopterygian ®sh. Although poorly preserved, this material provides evidence for three different taxa: a head of an indeterminate basal actinopterygian, some nearly complete specimens of indeterminate neopterygians and a tail of a chondrostean, which is certainly the most interesting fossil in this fauna. The absence of teleosts (except for possible ªPholidophoriformesº) in this fauna suggests that the Long Binh Formation is older than the Cretaceous and better agrees with a Jurassic age. q 2001 Elsevier Science Ltd. All rights reserved. Keywords: Jurassic; Fish fauna; Vietnam
1. Introduction Mesozoic ®shes are extremely rare in Southeast Asia and are mainly represented by isolated remains (scales, teeth, dermal bones) from the Upper Triassic Huai Hin Lat Formation of Thailand (Martin and Ingavat, 1982), the Lower Jurassic Yefbie Formation of Misool Island, Indonesia (Janvier and Hasibuan, 1985), the Upper Jurassic to Cretaceous Phu Kradung, Phra Wihan, Sao Khua and Khoh Kruat Formations of ThaõÈland (Buffetaut and Ingavat, 1985), and the Lower Cretaceous of Laos (M. VeÂran, personal communication). With the exception of the Lepidotes-like scales from Misool Island, all these ®sh remains are assumed to occur in fresh water deposits. In this paper, we report on the ®rst occurrence of a ®sh fauna, represended by partly articulated specimens belonging to at least three major actinopterygian taxa, from Mesozoic deposits of southern Vietnam. This ®sh fauna is potentially the most remarkable one ever found in southeast Asia, and it is probable that further discovery of unweathered material in this locality would provide important palaeobiogeographical data. The material described herein was discovered by Dr Le Thi Dinh of Hi Chi Minh City National University, who donated it to the Geological Museum (Bao Tang Dia Chat), 6 Pham Ngu Lao,
Hanoi, where it is collectively registered with the number BT 201. 1.1. Geographical and geological setting The Long Binh hills are situated about 17 km east of Ho Chi Minh City, east of the highway N81 running to the northern provinces of Vietnam (Fig. 1). The ®sh material has been collected in the Member 3 of the Long Binh Formation, exposed on the northern side Ho Chi Minh City. The Long Binh hills are formed by Mesozoic volcano±sedimentary rocks, which were referred to the Deo Bao Loc Formation and regarded as Late Jurassic to Early Cretaceous in age by NguyeÃn Kinh Quoc (1989). Typically, the Deo Bao Loc Formation mainly consists of andesite, with minor tuff interbeds, and its basal part includes continental red beds. Bui Phu My and Duong Van Cau (1991) revisited the Long Binh exposures and referred them to a new formation, the Long Binh Formation, which they regarded as Late Jurassic in age. The exposures of this formation in the Long Binh hills are very poor and their description is, therefore, based essentially on the borehole core N8918, drilled in the same area. They described the Long Binh Formation as about 420 m thick and composed of the four following members (in ascending order):
* Corresponding author. Tel.: 133-1407-93004; fax: 133-1407-93580. E-mail address: ®[email protected] (A. Filleul). 1367-9120/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved. PII: S 1367-912 0(00)00060-2
Member 1 (117 m): Andesite, andesitobasalt, interbedded with some marls and thin-bedded clayey cherts in the upper part.
642
A. Filleul, D. Vu Khuc / Journal of Asian Earth Sciences 19 (2001) 641±647
morphs referred to Classipollis sp., Osmundacidites sp. and Leiotriletes sp. Member 4 (65±75 m): Red tuffaceous siltstone passing upward to dacite and rhyolite. Near the Binh An village, situated 2 km north of the Long Binh hills, the andesite of the lowermost member (Member 1) of the Long Binh Formation lies unconformably upon sandstone layers which have yielded the ammonites Coroniceras sp. and Asteroceras sp. and are thus dated as Lower Jurassic. The andesite of this locality is penetrated by the granitoids of the Dinh Quan complex, which are radiometrically dated of 140 Ma, that is, Lower Cretaceous. This indicates, at any rate, that the base of the Long Binh Formation is older that the Early Cretaceous.
2. Systematic study
Fig. 1. Locality map.
Three different taxa have been recognized among the specimens. However, their completeness and the poor preservation prevent us from giving a much precise taxonomic determination. 2.1. Form 1
Member 2 (120 m): Tuffaceous lava, tuffaceous agglomerate interbedded in the upper part with some coaly, cherty shale and siltstone containing Estheria sp. Member 3 (115 m): Clayey shale, banded coaly shale with interbeds of marl. The clayey shale of this member has yielded the fossil ®shes decribed herein. The coaly shale have yielded some plant remains referred to Zamites sp., Pagiophyllum sp. and Dicksonia sp., as well as sporo-
Actinopterygii gen. and sp. indet. This taxon is represented by a unique and badly preserved specimen (Fig. 2). The specimen consists of a head with the mouth wide open and part of the trunk. It is not possible to observe any wellpreserved bone. The orbit is, however, visible and placed anteriorly as in lower actinopterygians and it recalls the head shape of a ªpaleonisciformº. The mouth opening seems very large as in ªpaleonisciformsº that exhibit a
Fig. 2. Head and part of the trunk of an undetermined actinopterygian (form 1).
A. Filleul, D. Vu Khuc / Journal of Asian Earth Sciences 19 (2001) 641±647
643
Fig. 3. Neopterygian gen. and sp. indet. One of the most complete specimens.
very posterior quadrate±lower jaw articulation. The body is covered with small scales, whose shape remains unclear. 2.2. Form 2 Neopterygii gen. and sp. indet. (Figs. 3±5). This taxon is widely represented in the fauna (12 specimens). Some of the specimens are complete but none of them exhibits a wellpreserved head. The tail, however, provides some information. Measurements for this form are summarized in Table 1. The body is entirely covered by rhomboid scales. The ®sh has a unique and unspinous dorsal ®n. The pelvic ®ns are in abdominal position. Although no bones of the head are preserved enough to show neopterygians synapomorphies, the overall proportion and the position of the orbit (not anteriorly placed) better ®t neopterygians than lower acti-
nopterygians. The caudal ®n presents fewer rays than in lower actinopterygians. Patterson (1973) proposed the following character as a synapomorphy of neopterygians: caudal ®n rays equal in number to their supports. Although the hypurals are not preserved in our material, the number of rays is consistent with the hypothesis that the specimens are Neopterygii. The caudal ®n is weakly heterocercal. The inner rays are more spaced out than the outer rays. The rhomboid scales form rows that extend posteriorly in both caudal lobes but extent further in the superior lobe. Six basal fulcra are present in the upper lobe. The scale covering prevents us from seeing the caudal endoskeleton, which is of primary importance in actinopterygians systematics. It is dif®cult to know to which group form 2 could belong among neopterygians without information from this part of the body. One must notice, however, that the caudal exoskeleton is very similar in shape and displays
Fig. 4. Drawing of the tail (form 2). a.f: anal ®n; l.l: lower lobe; u.l: upper lobe.
644
A. Filleul, D. Vu Khuc / Journal of Asian Earth Sciences 19 (2001) 641±647
Fig. 5. Drawing of the tail showing the fulcra of the upper lobe (form 2). f: fulcra.
the same characteristics as that of some ªpholidophoriformsº. It is especially similar to Pholidophorus as ®gured by Patterson (1968). The body proportions and size are also consistent with the hypothesis that the form 2 is a pholidophorid. Despite this resemblance, it cannot be referred to the pholidophorids as long as the endoskeleton and the head are not available. These parts are widely used to determine relationships of the pholidiphorids (see Nybelin, 1966). Here, we can only propose that the form 2 is a neopterygian, and that, among this group, it looks extremely similar to ªpholidoforiformsº. We cannot go further without better-preserved material. 2.3. Form 3 Chondrostei (sensu Grande and Bemis, 1996) gen. and sp. indet. (Figs. 6 and 7). This taxon is represented by a unique and incomplete specimen but far better preserved than the others. The posterior part of the body is visible from the dorsal ®n to the end of the tail. The body lacks scales except in the upper caudal lobe, which is covered laterally with a sheet of small scales. This feature is a synapomorphy of the Chondrostei (Grande and Bemis, 1996) and has been discussed in Bemis et al. (1997). Dorsal and anal ®ns are situated posteriorly and very close to the tail. The dorsal ®n is, however, anterior to the level of the anal ®n. Two series of radials are visible in the anal ®n but they have been
40 mm 36.6 mm 10.8 mm 4.2 mm 20 mm 30 mm 20.3 mm 11.2 mm 10.8 mm
3. Discussion 3.1. Stratigraphic implications
Table 1 Morphometic characteristics of form 2 Total length Standard length Maximum height Peduncle height Predorsal length Preanal length Prepelvic length Prepectoral length Head length
dislodged and are not lying at the same angle. Thirteen proximal radials and six middle radials are preserved. The middle radials are much more elongated than the proximal ones. Haemal spines and supraneurals (see Grande and Bemis, 1991 for the use of the term supraneurals instead of neural spines) display an elongated shape and are backwardly inclined. The tail is heterocercal. The extremity of the upper lobe is displaced and lies below its normal location. There is one dorsal caudal scute followed by numerous elongated fulcra. Thirty-three fulcra are preserved but there were probably more. Six supraneurals lie below the dorsal scute and the ®rst fulcrum. The series of supraneurals must have extended more posteriorly but no supraneurals are preserved posterior to the level of the second fulcrum. The ®n rays of the lower lobe are better preserved than the upper ones. They are dichotomous and supported by haemal spines and hypurals. Nine of the supports are visible but it is not possible to differentiate the last haemal spines from the ®rst hypurals. In addition to these three forms, isolated elements have been collected such as a nearly complete pectoral ®n (supposedly a non-neopterygian actinopterygian) and isolated bones, which remain undetermined but, however, remind bones of a chondrostean head (Figs. 8 and 9).
100% 90% 27% 10.4% 50% 75% 50% 27.9% 27%
The Long Binh Hills ichthyofauna lacks teleost ®shes other than possible pholidophorids. During the Cretaceous, most of the higher teleosts taxa were present and widespread (see Patterson 1993). Teleosts are so widespread in the known Cretaceous fauna that their absence in the Long Binh formation suggests that the fauna is not Cretaceous but Jurassic as proposed by Bui Phu My and Duong Van Cau (1991). Nevertheless, such an absence does not constitute an evidence for dating the locality but just an indication.
A. Filleul, D. Vu Khuc / Journal of Asian Earth Sciences 19 (2001) 641±647
645
Fig. 6. Tail of a chondrostean (form 3).
There is no contradiction between the presence of chondrosteans and the assumption that the locality is Jurassic in age. Acipenseriformes have been found in many Late Jurassic localities of the northern hemisphere (Grande and Bemis, 1991). The presence of the form 1 is consistent with the Jurassic age since lower actinopterygians (i.e. non-neopterygians) are known up to the Cretaceous. Pholidophorids are also known up to the Cretaceous (Patterson, 1993).
Jurassic and the Early Cretaceous of China (Jin et al., 1995). The phylogeny of the Chondrostei is mainly supported by characters from the head since the caudal skeleton remains plesiomorphic for most of the ingroup taxa. Therefore, the form 3 could be related to any taxon from Birgeria to Polyodon (see Grande and Bemis, 1996) except Acipenseridae because it lacks the characteristic lateral row of scutes.
4. Conclusion 3.2. Systematics implications The form 3 is the only one that is preserved enough to have a systematic interest. This is one of the earliest Chondrostei ever found if the locality is effectively Jurassic in age. Fossils of Acipenseriformes are known from the Late
The survey of the ichthyofauna agrees with the Jurassic age of the locality. Further ®eld investigation would be necessary to ®nd new complete specimens of the form 3, which would be of primary interest in the phylogenetic study of the Chondrostei.
Fig. 7. Drawing of the specimen representing the form 3. d.c.f.: dorsal caudal fulcra; d.s.: dorsal scute; h.s.: haemal spine; hyp: hypural; m.r.: middle radials; p.r.: proximal radials; r.sc: rhomboid scales of the upper lobe; Sn: supraneurals.
646
A. Filleul, D. Vu Khuc / Journal of Asian Earth Sciences 19 (2001) 641±647
Fig. 8. Pectoral ®n of an indeterminate actinopterygian.
Fig. 9. Possible chondrostean unidenti®ed isolated bones.
A. Filleul, D. Vu Khuc / Journal of Asian Earth Sciences 19 (2001) 641±647
Acknowledgements We would like to thank Dr Philippe Janvier for reading and making useful comments on the manuscript. D. Serrette made the photographs, H. Lavina prepared the map and F. Pilard some of the drawings. References Bemis, W.E., Findeis, E.K., Grande, L., 1997. An overview of Acipenseriformes. Environmental Biolology of Fishes 48, 25±71. Buffetaut, E., Ingavat, R., 1985. The Mesozoic vertebrates of Thailand. Scienti®c American 253, 80±87. Bui Phu My, Duong Van Cau, 1991. He tang Long Binh [Long Binh Formation]. Dia ly, Dia Chat, Moi truong, HoChiMinh City 1, 58±61. Grande, L., Bemis, W.E., 1991. Osteology and phylogenetic relationships of fossil and recent paddle®shes (Polyodontidae) with comments on the interrelationships of Acipenseriformes. Journal of Vertebrate Paleontology 11 (1), 1±121. Grande, L., Bemis, W.E., 1996. Interrelationships of Acipenseriformes, with comments on ªChondrosteiº. In: Stiassny, M.L.J., Parenti, L.R., Johnson, G.D. (Eds.). Interrelationships of Fishes, Academic Press, San Diego, pp. 85±115.
647
Janvier, P., Hasibuan, F., 1985. Lepidotes remains from the Lower Jurassic Yefbie Formation of Misool Island, Indonesia, Bulletin of Geology Resources and Development Center, Bandoeng. Jin, Fan, Tian, Yanping, Yang, Youshi, Deng, Shaoying, 1995. An early fossil sturgeon (Acipenseriformes, Peipiaosteidae) from Fengning of Hebei, China. Vertebrata PalAsiatica 33, 1±85. Martin, M., Ingavat, R., 1982. First record of an Upper Triassic ceratodontid (Dipnoi, Ceratodontiformes) in Thailand and its paleogegraphic signi®cance. Geobios 15, 111±114. Quoc, N.K., 1989. Deo Bao Loc formation. In: Khuc, V., My, B.P. (Eds.). Dia Chat, VieÃt Nam, Tap 1: Dia Tang, (Geology of Vietnam, Part 1: Stratigraphy), Gen. Dept. Mines Geol, Ha Noi (378 pp.). Nybelin, O., 1966. On certain Triassic and Liassic representatives of the family Pholidophoridae s.str. Bulletin of the British Museum (Natural History), Geology 11 (8), 354±432. Patterson, C., 1968. The caudal skeleton in lower Liassic pholidophorid ®shes. Bulletin of the British Museum (Natural History), Geology 16 (5), 203±239. Patterson, C., 1973. Interrelationships of holosteans. In: Greenwood, P.H., Miles, R.S., Patterson, C. (Eds.). Interrelationships of Fishes, Academic Press, London, pp. 233±305. Patterson, C., 1993. Osteichthyes: Teleostei. In: Benton, M.J. (Ed.). The Fossil Record 2, Chapman and Hall, London, pp. 622±656.