No 3-4 Series B 1994 GEOLOGICAL SURVEY OF VIET NAM HA NOI Journal of GEO LOG Y Series B, N 3-4/1994 (Thirty fourth y e a r ) E D IT O R IA L O F F IC E Phạ m Ngũ Lão Str.,H Nộ i T el.84.4.253 110, 84.4.246 461 Fax:84.4.254 734 E D IT O R IA L BO A R D K d ilo r-in -ch ief: TRAN VAN TRỊ Members: LÊ » K : AN, PHẠ M VAN A N.N C.ITK N XI ÂN B A O , \ r l T Ễ \ C.IAO, VĨỈ \ < ; o r IIÁI (D eputy K (ỉ itor-in-chief), v ũ KHl ' C (D eputy E d itor-in-chief), N G I Y K N NGHI ÊM V1IMI TANC MI Ờ I, VÕ C Ô \C , NGIIIỆ P, NGUYỄ N T IỂ N T H À N H , T ố \ < ; D I T T IIA M I, TRÂN MINH THÍ:, 1*11 AN TRƯ Ờ NG T H Ị ,PHAN c ự TIẾ N, LÍ; VAN TRẢ O, \ c l Y Ễ \ KHÁC' VINH, \ r , l YEN TRỌ NC YKM Secretary B Ì I m vc THÁNG Subscriptions Series A in V ietnam ese w ith E nglish sum m ary ( bim cnsual issues) 48 USD l o r the Am erican continent, 42 USD for the rest o f the w orld, 30 USD for adresses in Việ t Nam Series B, in Hnglish (2 issues or double issue per annum ) : 22 USD for the* American continent, 20 USD for the rest o f the w orld, 16 USD for adresses in Việ t N am (A irm ailed on request at appropriate surcharge) Reduced rate available f o r p erson al subscribers Copyright © hy G eological Survey o f Việ t N am Phạ m Ngũ Iiío Str.Hà N ộ i, Việ t N am All ri^ h t r e s e r v e d N o p a r t o f th is p u b lic a tio n m a y b e r e p r o d u c e d o r tr a n s m itte d in a n y fo rm w ith o u t p e r m is s io n Journal of GEOLOGY (Geol Sursv Việ t Nam), SeriesB, No 3-4/1994, pp 1- 11 NEW VERTEBRATE REMAINS ASSOCIATED WITH EURYPTERIDS FROM THE DEVONIAN Đ SƠ N FORMATION, VIỆ T NAM(1) Tố N G DUY THANH*, P.JANVIER **, ĐOÀN NHẬ T TRƯ Ở NG*** and S.BRADDY**** A b s tr a c t Some eurypterid and fish remains were discovered, in the clay lens o f the sandstone Đồ Sơ n Formation near Ngọ c Sơ n Village (Đồ Sơ n) These Eurypterids have affinities to RhynoccircinOSom.% a rare eurypterid genus Fish remains belong to Placodermi and O stewhthye, their structures are quite different from, the known Devonian fishes,'the Placodermi remains may belong to new taxon am ongantm rchs The detail study of the "eurypterid lens" confirms a m arginal marine to brackish w ater environm ent for a pa rt o f Đo Sơ n Formation, while the m ost part of this form ation belongs to the indisputable fluvml-like facies None of these fish and eurypterid remains provides valuable stratigraphical information, except that the presence of the placoderm remains rule out a Carboniferous age for the fossil bearing rocks The presence of fish Bothriolepis sp and of plant fossils Lepidodendropsis sp accords with the Givetm n to Frasnmn (?) age o f this Formation (Janvier et al 1989, Long et al 1989, Tố ng Dùy Thanh 1993) The p resen ted here m aterials em phasize the unÙỊ ueness of the Đo Sơ n fish fauna A part from Bothriolepis sp which is widespread form, neither does V tnam aspis nor such forms, as those described here occur elsewhere in the Middle nor Upper Devonian of Bắ c Bộ and South China In addition, the facies of Đồ Sơ n Formation is quite different from all the M iddle-U pper Devonừ in form ations ofB ắ cB ộ The la tter consist m ainly o f lim estones, (1 -Journal of Geology (Geol Surv.VN), Ser A, N.224/1994 (in Vietnamese) * Department of Oenlfiffy, Hanoi University, 90 Nguyỗ n Trà i str., Đo ngDa, Hanoi, Vietnam ** URA 12 du ('NRS.Laboratoirc de Palé ontologie, rue Buffon, 7500 Paris, France *** Institute of (rt'cilogy and Mineral Resources, Đố ng Đa, Hanoi, Viet Nam **** Department of'Cieology, Manchester University, Manchester, Great Britain som etim es with siliceous limestone and siliceous interbeds, while the ĐÔ Sơ n Formation compounds from sandstones o f fluvial-like facies and some d a y lens o f marine to brackish w ater environment The p resen ted data in this article may mean that the Đô Sơ n Forma tion, whose tectonic relationships with the other Devonian form ation of Việ t N am are still obscure, does not belong to the South China Block but to some allochthonous terrane INTRODUCTION The Đồ Sơ n Peninsula extends south eastward into Bắ c Bộ Gulf, about 20 km South of Haiphong, Vietnam It is entirely made up of D evonian sandstone (Fig 1, quartzite The age.of the Đồ Sơ n Formation has long been uncertain, and has often been regarded as equivalent to the Early De vonian Sika Formation of Bac Bo (Northern Vietnam), hence the m istaken Early De hatched) which Lantenois (1907) referred to as the "Do Son Sandstone" (Grès de Do Son") vonian age suggested on the basis of the poorly preserved psilophyte and fish re Later, Patte (1927) rejected this name on the ground that Lantenois used it for a number of other sandstone formations in the same area, which were known to be Triassic in age However, we use the term Đồ Sơ n For mains (Janvierei al 1987) The more signifi cant fish and plant remains later described from the Đồ Sơ n Formation (in particular Bothriolepis, V ietnam aspis, Colpodexylon mation here exclusively for those sandstones Chong-Yang) suggest a Givetian to Late De which crop out on the Đồ Sơ n Peninsula vonian age (Tong-Dzuy 1993) Fish remains had been recorded long ago from the Old Red Sandstone of the Đồ Sơ n Peninsula (Tong Dzuy et al., 1986), but they remained undescribed until relatively com plete materia] was discovered in the mid1980'S in several blocks on the shore, downhill from the ruins of "Bả o Dai’s villa" (Blieck et aL, 1987, Janvier et al 1989, Long et at 1990; 1, Fig.l) Two bothriolepid antiarchs have been recorded from this local ity One is a large Bothriolepis, which resembles somewhat B.gigantea from the Late Devonian of Europe and the other in Vietnamaspis trii (Long et al 1990) Blieck ct at (1987) also described an isolated poste rior median ventral plate, possibly of a m e dium- sized arthrodire later referred to with doubt as a groenlandaspid All this material is preserved as impressions in very hard and Lepidodendropsis, identified by Dr.Cai NEW EURYPTERID MATERIAL In addition to fishes and plant remains (psilophytes, Colpodexylon sp.; Janvier et al 1987, 1989), the Đồ sơ n Formation has also yielded remarkably well preserved ar thropod remains which had been tentatively referred to the chasmataspids (Waterston in Janvier et al 1989) Examination of this m aterial has revealed its true affinity, nam ely the eurypterid Rhinocarcinosoma (Fig 3; Braddy et al in preparation) The eurypterid remains occur at two places (4 and 5, Fig 1), but the most complete and well preserved m aterial comes from a single green-grey clay lens in the southern part of the sm allest of the two quarries which were sociation with small lingulids, planorbidlike gastropods and plant remains The best, most complete eurypterid materia] was de rived from the base of one particular clay lens (Fig.2) that occurs in a sequence of in terbedded coarse sandstones and clay hori zons The upper part of this clay lens is pervaded by large, horizontal burrows, pos sibly of arthropod origin, which are filled with the relatively coarse sandstone of the overlying layer These burrow fillings con tain numerous lingulid fragments as well as some fish dermal plates, which deserve a short description, since they are different from all fish remains hitherto described from Đồ Sơ n (see below) Figure Locality map 1: outcrop with B othriolepis sp., V ietnam aspis trii The eurypterids not provide precise stratigrap h ical inform ation Rhinocarcinosoma is a very rare form, the only two and Lepidudendropsis sp ; 2: o u tcro p w ith Colpode.xylon sp and Lepldodendropsis sp.;3: psilophyte remains; 4: plant, bivalve and some eurypterid remains; 5: quarry yielding complete eurypterids species known are described from the Middle Silurian of New York State, USA The occur and the fish remains described in this paper nificant as it extends the temporal and geographic range of this poorly known form exploited on the eastern slope of Ngọ c Xuyên rence of Rhinocarcinosma in Vietnam is sig Hill (locality 5, Fig 1; Fig.2) During November 1993, a visit to Đồ Sơ n was organized to collect more eurypterid material Abundant remains of Rhinocarcinosoma w ere d isco v e r e d , in c lu d in g a prosoma, an anterior appendage, numerous posterior appendages (paddles) and tergites of the opisthosoma, some showing three di mensional preservation, a telson and an al m ost com p lete a r tic u la te d ju v e n ile specimen In addition, some eurypterid re mains oth er collected appear to come from an e u ry p terid g e n u s, p o ssib ly Hughmilleria, suggesting that the Đồ Sơ n eurypterid fauna is more diverse than pre viously thought The eurypterid remains are found in as EURY PTERID PALAEOECOLOGY The sedimentology and fauna, particu larly the lingulid brachiopods, indicate that this part of the Đồ Sơ n Formation was de posited in a m arginal m arine, brackish water environment, possibly as part of a deltaic orestuarine system The sandstones represent deposition within the alluvia] sys tem with the interbedded clay lenses possi bly indicating the presence of a pool, or stagnant water body, cut-off from the allu via] channel The very fine laminated nature of these clays suggests a possible evaporitic nature for this lithology Carcinosomatid eurypterids have been Massively bedded 3m„ F —1 Old Red Sandstone „\/ Ironstones occur ^ occasionally in clay '■ Л Paler, finer sand stones /2mand occasional clay horizons _ \ / Burrows contbininL, s fish remains -p- .T j j 5?' * ~-«=г- г ! ~~-^ bedded г1 е пт sandstones anc^ c*a^ lenses^ ury pterid fragments Debris ^247305° I > JJ Worm burrows Eurypterid horizon § ^ Green-grey clay R Light brown coarse sandstone Quarry floor Figure Sketch of the quarry at Ngọ c Xuyên, showing the position of the eurypterid and fish-bearing clay lens On the right side is a representative m section of the quarry recognized as representatives of the most m arine eurypterid biofacies (K jellesvigWaering 1961) The genera Carcinosoma, Eocarcinosoma and Paracarcinosoma are restricted to inner shelf and marginal envi ronments whereas the ecological range of Rhinocarcinosoma extends into non-marine, fluvial and lacustrine settings of the posterior appendages (paddles) rela tive to forms such as Carcinosoma These eurypterids were certainly top predators, or benthonic scavengers, within their environ ment, capable of feeding on the fish, lingulids, other arthropods and worms, either actively burrowing for prey or lying in wait, partially buried beneath the substrate sur Rhinocarcinosoma w a s a ttr ib u te d a "mud-grubbing" mode of life, due to the presence of the anterior process on the face to ambush their prey prosom a, which (Clarke and Ruedmann 1912) More evi preserved out of the axis of the abdomen, as seen in many paracarcinosomatid euryp dence for the benthonic mode of life of R hi nocarcinosoma comes from the reduced size terids, has led previous workers to conclude great flexib ility for th ese cylindrically w as u sed for digging The length of the postabdomen, and the fact that it is partially disarticulated and Figure Rhinocarcinosoma sp., reconstruction based on the m aterial from Đồ Sơ n A: dorsal view (approximate length: 30 cm); B: in attack/defence posture e shaped caudal segm ents According to the reconstruction of th is specim en (Fig.3A), the postabdom en appears very tublar and capable of defending the dorsal surface of th is anim al w ith its sp ik e -lik e telso n (Fig.3B) No duct or poison gland has ever been recorded in the telson of any eurypterid, so it is doubtful if th e te lso n had any role in prey capture In ste a d , prey would have been trap ped by th e a n te rior a p p en d a g es and in tr o d u ce d in to the oral cavity for fu rth er m a stica tio n hy th e coxal ap p en d ages VERTEBRATE REM AINS Two types of fish plates have been found in the burrows of the Ngọ c Xuyên quarry One is represented by an undoubted placoderm anterior ventrolateral plate, and the other consists of two incomplete, very thirị plates, ornamented with thin, sinuous radi ating ridges The latter are referred with some doubt to an osteichthyan The speci mens are deposited in the Geological Mu seum (Bả o Tàng Đị a Chât, abbreviated here as BT) of the Geological Survey of Vietnam, Phạ m Ngũ Lão Street, Hanoi A 10 mm I iv -cita AN Ạ ' oaAVL IS '** - \ Figure Placoderm i gen et sp indet., Ngọ c Xuyên quarry, Đo Sơ n Loft anterior ventrolateral plate (BT 185) in ventral (A), dorsal (B) and anterior (C) views Cameralucida drawing, cita: anterior internal transverse crest; k: dorsolateral knob; n: notch in the posterior margin of the lateral lamina; pchb: perichondral (endoskeletal) bone; pf: pectoral fenestra or exillary foramen; oaAVL: overlap area for the opposite anterior ventrolateral plate of the posterior median ventral plate; oaPVL: overlap area for the posterior ventrolateral plate; sp: spina] process; SI: embayment for the sem ilunar or anterior median ventral plates The p la c o d e r m p la te (Fig.4, P1.1A) The best preserved specimen is a left anterior ventrolateral plate of the thoracic armour of a placoderm (BT 185), which has been prepared by the transfer method on tran sp arent resin The p late is alm ost tiarchs, in particular Yunnanolepis and Chuchinolepis (Zhang 1979, Tong-Dzuy & Janvier 1990) This feature in unknown in other placoderms However, no known an tiarch possesses such a well-developed and pointed spinal process Moreover, there is apparently neither a brachial process, nor a square-shaped, whith a large, falciform spi nal process (sp, Fig.4A) Its external orna m en tation c o n sists of large, scattered tubercles (Fig.4A), which become smaller on brachial recess comparable to that in an tiarchs However, the scapulocoracoid may be represented in part by the small patch of its lateral lamina and near the pectoral fenestra (pf, Fig.4) The latter is indicated perichondral bone which overlies the spinal process (pchb, Fig.4B) and fuses medially by a narrow notch, situated immediately be hind the spinal process Internally, the plate with the knob of the internal transverse crest In the case, the notch referred to here shows a prom inent anterior transverse crest (cita, Fig.4B, C), which is produced as a pectoral fenestra would rather be an axillary foramen dorsolaterally into a knob (k, Fig.4B,C) From the latter, two blades of apparently This specimen probably belongs to new taxon among the antiarchs, or placoderms in general, but its formal description must a perichondral bone (pchb, Fig.4B,C) descend toward the expanded dorsal surface of the spinal process There are two broad overlap areas for adjacent plates, medially and pos teriorly The posterior one (oaPVL, Fig.4B) is for the posterior ventrolateral plate, and the medial one (oaAVL, Fig.4B) is for either a median ventral plate or the contralateral anterior ventrolateral plate The anterior margin of the plate is almost straight, whith a medial embayment for either the semilunar plate or the anterior median ventral plate (SI, Fig.4B) This plate cannot be referred with cer tainty to any of the known placoderm taxa However, its overall shape, prominent inter nal transverse crest, high lateral lamina are rather suggestive of antiarchs Other strik ingly antiarch-like features are the clear- wait the discovery of complementary m ate rial The osteich th y an p la te s (Fig.5, PI IB) The two other fish remains are poorly preserved plate fragments (BT 186-7), which are ornamented with nodose ridges or vermiculations One of these plates has been prepared by transfer on both sides, and its internal side shows a prominent oblique lamina (la, Fig 5A2) In section, the ridges of th e o r n a m en ta tio n are m u sh ro o m shaped, sometimes asymetrical (Fig.5B2) , and rest on a spongy basal layer None of these plates look placoderm-like, although a somewhat similar ornamentation occurs in some petalichthyids and arthrodires (e.g; Holonema) The bone is very th in and cut, step-like, internal lim it of the overlap thereby more suggestive of osteichthyans than of placoderms Among osteichthyans, areas (Fig.4B), the parallel vascular grooves on these areas, and a peculiar notch (n, Fig.4A,B) in the posteroventral corner of the no known Devonian actinopterygian has such an ornamentation, but some sarcopterygians have a more or less similar orna plate, which occurs widely in primitive an >— 10 mm Figure ? O steichthyes gen et sp indet., Ngọ c Xuyên quarry, Đo Sơ n Undetermined dermal plates, camera-lucida drawings A: specimen BT 186, in external (Al) and interna] (A2) views, and vertical section through the internal ohlique lamina (A3); B: specimen BT 187 in externa] view (B 1), detail of the surface (B2) and vertical section (B3); la: internal oblique lamina mentation However, the oblique internal lamina does not match any of the Devonian Givetian to Late Devonian age suggested earlier (Janvier et al 1989, Long et al 1989, osteichthyan dermal bones known to date Tố ng Duy Thanh 1993) This material em phasizes the uniqueness of the Đồ Sơ n fish fauna Apart from Bothriolepis sp., which is w id esp rea d form , n e ith e r d oes Viet- REMARKS None of these fish and eurypterid re mains provides stratigTaphi cal information, except that the presence of a placoderm rules of large (decimetric), yet indeterminable, coalified plant remains in the underlying clay lens would rather accords with the namaspis nor the forms described here oc cur elsewhere, in particular in the Middle or Late Devonian of South China (in particular Guangdong and Hongkong) The detail study of the "eurypterid lens" of the Ngọ c Xuyên quarry confirms a mar- Plate Vertebrate remains, ĐÒ Sơ n Formation, Ngọ c Xuyên quarry, Đồ Sơ n A: Placodermi gen et sp indet Left anterior ventrolateral plate (BT 185) in ventral (A l) and dorsal (A2) views K Osteichthyes gen et sp indet., dermal plates in external aspect (B l, BT 186; B2, BT 187) Scale bar: 10mm ginal marine to brackish water environment for part of the Đồ Sơ n Formation, in spite its indisputable fluvial-like cross-bedding in the massive sandstone beds of the distal part of the peninsula The facies of the Đồ Sơ n Formation is quite different from all the Devonian forma tions of Bắ c Bộ (Tonkin) Region Th'e Mid dle- Upper Devonian formations of the Bac BỘ Region consist m ainly of lim estones, sometimes with siliceous lim estones and si liceous interbeds, while the Đồ Sơ n Forma tion is ch aracterized by sa n d sto n es of fluvial-like facies and some clay lens of ma rine to brackish water environment The fa REFERENCES BRADDY S.J., SELDEN P.A and ĐOÀN NHẬ T TRƯ Ở NG, (in prep) A new carcinosomatid eurypterid from the Upper Devonian (Givetian/Frasnian) of the Đồ Sơ n peninsula, Northern Vietnam CLARKE J.M and RUEDEMANN R 1912 The Eurypterida from N ew York Mem N ew York State Mus.Nat H ist., 14:1439 JANVIER P., BLIECK A., GERR IE N N E , P et TONG-DZUY THANH 1987 Faune et flore de la Formation de Sika (Dévonien inférieur) Đồ Sơ n (Hả i Phòng, cies of the Đồ Sơ n Formation is different from the Givetian- Frasnian Lỗ Sơ n (=Tràng Kênh) Formation, lim estones of which are Việ t Nam) Bull Mus natnH ist nat., Paris, 9, 291-301 widespread near the Đồ Sơ n Peninsula to the north-west of the latter JANVIER P., GERRIENNE p et TỐ NG DZUY THANH, 1989 Les placodermes, Arthropodes et Lycophytes des grès The above mentioned data may mean that the Đô Sơ n Formation, whose tectonic relationships with other Devonian forma tions of Việ t Nam are still obscure, does not belong to the South China Block but to some allochthonous terrane dévoniens de Đồ Sơ n (Hả i Phòng, Việ t Nam) Géobios, Lyon, 25 (5): 625-638 KJELLESVIG-WAERING E.N 1961 The Silurian Eurypterida of the Welsh Bor derland Journal of Palaeontology, 35, 789835 ACKNOWLEDGEM ENTS This article was effected in the frame of the Scientific Research Project KT 01.05 and Programme of Fundam ental research in Earth Sciences of Việ t Nam (KT 04) The field trip of French and English coauthors w as supported by a grant from DAGIC (France) and the Geological Society of Great Britain The author express their thanks to Prof A Boucot (Oregon University, USA) for his help in improving the manuscript of this paper LANTENOIS H 1907 Notes sur la géologie de 1’ Indochine Bull Soc géol, France, 4e sér., 1/4, 56p LONG J.f BURRETT c., PHẠ M KIM NGÂN and JANVIER p 1990 A new bothriolepid antiarch (Pisces, Placodermi) from the Devonian of Đồ Sơ n Peninsula, Northern Việ t Nam, Alcheringa, Sydney, 14: 181-194 PATTE, E 1927 Études géologiques dans l’Est du Tonkin Bull Serv géolf Indo chine, Hanoi, 26(1), 1-314 TỐ NG DZUY THANH, 1993 Major features of Devonian stratigraphy in Việ t Nam, with remarks on palaeobiogeography 10 11 TỐ NG DZUY THANH et JANVIER P 1990 Les Vertébrés du Dévonien in 10 TONGDZUY THANH, ĐẶ NGTRẠ Nférieur du Bắ c Bộ oriental (Provinces de Bac Thái et Lạ ng Sơ n, Việ t Nam) Bull Mus HUN, NGUYỄ N ĐÌNH HỊE, NGUYEN natn H ist, nat., Paris, 12(2), 143-223 ĐỨ C KHOA, NGUYỄ N HỮ U HỬ NG, TẠ 12 ZHANG G.R 1978 The antiarchs HÒA PHƯ Ơ NG, NGUYỄ N THE DÂN and from the Early Devonian of Yunnan V e rte PHẠ M KIM NGÂN, 1986 Hệ Devon Việ t J Geol (Geol Surv Vietnam), B 1993 (1-2), 3-18 Nam [The Devonian in Vietnam] Publ House Khoa họ c kỹ thuậ t Hà N ộ i 141 p brate PalAsiatica, Beijing, 16, 147-186 (in Chinese with English sum mary) (in Vietnamese) 11 Journal of GEOLOGY C.HOLOGICAL SURVEY OF VIET NAM Series B, N o.3-4, 1994 CONTENTS TỎ NC DIJY T H A N H , P JA N V IE R , Đ O À N N H Ậ T TR Ư Ở N G , S.B R A D D Y New vertebrate rem ains associated w ith E urypterids from Lite D evonian Đồ Sơ n urination, V iệ t Nam PHAN TRỌ NC, T R Ị N II C enozoic stress field in the N orthw estern region o f Việ t, N am Dỏ 12 HAI DŨNCỈ , Đ IN H HỮ IJ M IN H ( 'liaracteristics and potential o f the copper m ineralizatio n s in B a Vi area 19 D Ậ U H IỂ N l orm ing and developing stages o f b auxites in South V iệ t N ám 25 VÕ CÔ N G N G H IỆ P, Đ Ặ N G N G Ọ C T R Ả N c iroundw ater m anagem ent and protetion in V iệ t N am 30 VŨ V Ả N NCÌHI A ssessm ent o f g roundw ater resources in M ekong D elta TẠ 37 I I()À N (Ì PHƯ Ơ NG New data on D evonian deposits in H àm R ng area (T hanh H óa Province) a X N ( JYKN V Ả N ( ’ÍIỮ , NCrl IYEN V A N LA N , D ỗ 47 ọ uố c BÌN H New discovery o f sulfosalt m inerals in gold ores from N Pái deposit, Binli i l i a D istrict 48 y CIIRONICLK International sym posium on "G eology o f SE A sia and ad jacen t areas" a jo in t M eeting 1)1' ICiCP P rojects 306, 321 and 359, H Nộ i, N ovem ber 1995 52 10 54 IMm i ICATIONS OF GEOLOGICAL SURVEY OF VIỆ T NAM Permit № /B iF e b r u a r y 3-1994, Printed by C ong cioa n P rintting E nterprise ( ’oinplclcd at January, 1995 ... GEOLOGY (Geol Sursv Việ t Nam), SeriesB, No 3-4/1994, pp 1- 11 NEW VERTEBRATE REMAINS ASSOCIATED WITH EURYPTERIDS FROM THE DEVONIAN Đ SƠ N FORMATION, VIỆ T NAM(1) Tố N G DUY THANH*, P.JANVIER **, ĐOÀN... genus Fish remains belong to Placodermi and O stewhthye, their structures are quite different from, the known Devonian fishes, 'the Placodermi remains may belong to new taxon am ongantm rchs The detail... NG, (in prep) A new carcinosomatid eurypterid from the Upper Devonian (Givetian/Frasnian) of the Đồ Sơ n peninsula, Northern Vietnam CLARKE J.M and RUEDEMANN R 1912 The Eurypterida from N ew York