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Bollettino della Società Paleontologica Italiana Modena, Novembre 1999

Conodo n t Mass Extinction an d Recovery from - Boundary Beds in the Meishan Sections, Zhejiang, China

Cheng-yuan WANG Nanjing Institute of Geology and Palaeontology Academia Sini ca

KEYWORDS- , Mass extinction, Recovery, Permian/Triassic, Meishan, China.

ABSTRACT-A high-resolution and fine taxonomy are the basis for the study ofmass extinction and recovery. The Meishan sections provide a good example. Conodonts are commonly considered to be a leading fossi l group for the Permian and Triassic biostratigraphy. Conodonts of the Meishan sections have been studied extensively and ranges of alt species are clear. subcarinata (Sweet) disappears at the top ofthe Changhsing Limestone; Clarkina deflecta (\Vtlng & W'tzng) and C. xiangxiensis (Tian) disappear within boundary bed 2 (or bed 26); the range ofCiarkina meishanensis Kozur & W'tzng is confined to boundary bed l {or bed 25,26); Clarkina carinata (Clark) appears somewhat earlier than parvus (Kozur & Pjatakova); Clarkina changxingensis (\Vtlng & W'tzn.V extends up across the !ioundary and disappears in the u?Aer part of boundary bed 2; Hindeodus parvus, which evolved from Hindeodus fatidentatus praeparvus Kozur, appears first in the middle o boundary bed 2; Isarcicella staeschei Dai & Zhang appears in bed 28, 8 cm higher than Hindeodus parvus. The Meishan sections contain bot the pelagic facies conodont Clarkina and the neritic jacies conodont Hindeodus. After a detailed study of conodonts fr_om the Meishan sections, the present author that conodont mass extiction demonstrates a stepwise character, it was nota "sharp knife cut': Compared with other fossi! groups such as jusulinids and ammonoids, conodonts were the latest to become extinct in the P/T mass extinction. Duration of the conodont mass extinction is the shortest; and they were the earliest to recover as indicated by the FAD ofHindeodus parvus or the first appearence ofisarcicella staeschei. There were no conodont refogia or Lazarus taxa during the P/T mass extinction and recovery intervals. élarkina carinaça and Hindeodus latidentatus (Kozur, Mostler & Rahimi-Yazd) were crisis projenitor species; Hindeodus changxingensis C. Y.W'tzng and Clarkina meishanensis Kozur & W'tzng were disaster species or fai led crisis progenitor taxa.

RIASSUNTO- [Estinzione di massa e radiazione dei conodonti attorno al limite Permiano/Triassico nella sezione di Meishan, Zhejiang, Cina] - La possibilità di disporre di dati biostratigrafici e tassonomici molto accurati sta alla base dello studio di un'estinzione di massa e della successiva radiazione. La sezione di Meishan ne costituisce un ottimo esempio. I conodonti sono considerati il più importante gruppo di fossili per la biostratigrafia del Permiano e del Triassico. Nella sezione di Meishan la fauna a conodonti è stata studiata in dettaglio e fa distribuzione stratigrafica di tutte le specie è stata determinata accuratamente. Clarkina subcarinata (Sweet) scompare al tetto del Changhsing Limestone; Clarkina deflecta (\Vtlng & W'tzng) e C. xiangxiensis (Tian) scompaiono all'interno del "boundary bed 2" (o livello 26); la distribuzione di Clarkina meishanensis Kozur & W'tzng è limitata al "boundary bed l" (o livello 25, 26); Clarkina carinata (Clark) compare appena prima di Hindeodus parvus (Kozur & Pjatakova); Clarkina changxingensis (\Vtlng & W'tzng) oltrepassa il limite e scompare nella parte alta del "bounda7, bed 2"; Hindeodus parvus, che si è evoluto da Hindeodus latidentatus praeparvus Kozur, compare nella parte mediana del "boundary bed 2 :· Isarcicella staeschei Dai & Zhang compare nel livello 28, 8 cm al di sopra di Hindeodus parvus. Nella sezione di Meishan sono presenti conodonti sia della facies pelagica a Clarkina, sia di quella neritica a Hindeodus. Lo studio dettagliato dei conodonti della sezione di Meishan dimostra come l'estinzione dei conodonti sia avvenuta a più riprese e non sia stata improvvisa. In con}ronto ad altri gruppi, come le fusuline e le ammoniti, i conodonti sono stati gli ultimi a scomparire e la durata della loro estinzione è stata la più breve: infatti, essi sono stati i primi a comparire, come testimoniano il FAD di Hindeodus parvus e la prima comparsa di Isarcicella staeschei. Durante l'estinzione di massa P/T non sono segnalate ne' aree di rifogio di conodonti, ne' taxa Lazzaro. Clarkina carinata andHindeodus latidentatus (Kozur et al.) possono essere considerate "crisis projenitor specie/; mentre Hindeodus changxingensis C. Y.W'tzng and Clarkina meishanensis Kozur & W'tzng potrebbero essere state "disaster species" o "jaifed crisis progenitor taxa':

INTRODUCTION of mass extinction and recovery: l. The study of biotic recovery lays particular The mass extinction that occurred in the latest emphasis on benthic fauna in shallow water facies, Permian was the most extensive of the "five big events" particularly on reefs, corals, gastropods, brachiopods, in the Phanerozoic (Raup & Sepkoski, 1982). Nearly only a few papers deal with the pelagic fauna. 85% of marine species and some 70% of the terrestrial 2. Most palentologists understand that a high- genera became extinct (Erwin 1994; resolution biostratigraphy and a fine taxonomy are Bowring et al., 1998). The Palaeozoic Evolutionary required for the study of mass extinction and recovery. Fauna of Sepkoski ( 1991) nearly vanished. Study of P l Bur these studies at present are mainly around the T mass extinction events was the focus of the study of generalized models of mass extinction and recovery Phanerozoic events in the eighties. Study of the biotic proposed by Kauffman & Erwin (1995) in which recovery from the P /T mass extinction is o ne of the recovery time intervals are qui te different. The shortest more important topics in the nineties. At present, the interval is 2-3 Ma (i. e., the recovery of pelagic following facts should be noted concerning the study graptolites in the early ); the longest is l O 490 C.Y WANG

(i. e., the biotic recovery of the Triassic). These time conduded definitely tbat the boundary day beds were intervals are too long to provide a high-resolution formed by volcanism an d contain very low iridum. This biostratigraphy. Extinction patterns of diffrent fossi! condusion was accepted by Rui et al. (1988) and Yin groups have been compiled from taxa ranges, often with et al. (1992) who added more evidences for the volcanic poor chronostratigraphic contro!. origin of the boundary day beds. Huge explosive volcanic eruptions in tbe eastern Tetbys and eruption The present author has selected conodonts of the of the Siberian Trap (Renne et al., 1995) lead to a drastic P/T boundary beds as a target for the study of the P/ drop in the biodiversity. The black day bed (the upper T mass extinction and recovery, primarily for the part of tbe boundary bed l or bed 26) represents a foliowing reasons: anoxia event. l. Conodonts are the leading fossi! group for Permian 3. The age of tbe boundary day beds (boundary bed l, and Triassic biostratigraphy, especialiy in recent years, or mixed bed l of Sheng et al., 1984) has been solved. and conodonts of the P/T boundary beds have been He (1981) first recognized rbat minerals of tbe intensively studied. these studies provide the basis for boundary day beds were similar to tbose of tbe day an excelient high-revolution biostratigraphy. beds witbin the Changhsing Limestone, but she stili 2. Conodont were nektonic, and the study of placed the P/T boundary at the base of tbe boundary their mass extinction and recovery should reveal a day beds. Zhang (1984) assigned the bed 26 (black concrete regular pattern in the pelagic facies. day) to the Yinkeng Formation and bed 25 (white 3. Idealiy, studies of mass extinction and recovery are day) to tbe Cbanghsing Formation. Clark et al. (1986) best made at the species leve!. Unfortunately most first put the boundary day beds to the Changbsingian current studies are limited to the generic or familial based on study of tbe conodonts from rbe day beds. levels. Thus the species-level record of conodonts in Sbeng et al. (1987) and Yin et al. (1996) also conduded the P/T boundary beds in the Meishan sections can tbat tbe age of the boundary day beds is provide a good example. Changbsingian. 4. As many as 13 definitions proposed for tbe P/T biostratigraphic boundary have been proposed. Tbese FOUNDAMENTAL DATA FOR THIS STUDY are summarized by Wang (1994). One of main proposals is to piace the base of the Triassic at the base Tbe stratigrapby and tbe conodonts of tbe P/T of the boundary day beds (Zbao, 1981; Sbeng et al., boundary beds of tbe Meisban sections bave been l984;Yangetal., 1987;Yin, 1994;Mei, 1996).Thus intensively studied in recent years (Wang, 1994, 1995, 1996; Wang et al., 1996; Wang &Wang, 1997; Kozur eta!, 1996;Mei, l996;Zhangetal., 1995).Although Be d there are stili some differences of opinion concerning Sample thickness number taxonomy,ranges, lineages and zonation of the (cm) conodonts (Wang, 1998), scientists are in generai "O Q) 884 D agreement, so the section provides a good basis for a 2:- Claraia wangi study of tbe P /T mass extinction an d recovery. ro _gJ Ophiceras è: Q) c Cl l. Tbe P /T boundary beds in the Meisban sections 2 ::J .!: o 883 (lJ c\'l are tbe continuous marine deposits. Tbe sedimentary è:' c: o (!) U5 environments was low slope facies. Wang (1994) 882-4 o C/) >o (.) "' <( stressed that tbe boundary day beds were the deposits (!) Biostratigraphic 882·3 LJ._ .:g 0:: below tbe storm wave base and the majority of tbe 0:: boundary H. parvus O> 0 l- C-- Q) numbers of the PTWG now accept tbis condusion ro 882-2 z (Wang et al., 1996; Kozur eta!., 1996; Yin eta!., 1996). è: :;:g> 0:: ro ·;;; UJ eta!. (1994); Jin et al. (1994); Zbu eta!. (1997) tbat > -§,O. the P/T boundary beds in the Meishan sections are 881 Hypophyceras :::J ?Otoceras sp. Event stratigraphic c3 discontinous deposits can not be accepted. Some rJ? c boundary 880 Cbinese authors bave also changed their points of view o and now support the condusion that tbe boundary uc 879 beds represent continuous deposition. 2. Zhang et al. (1984) considered tbat the boundary UJ 878 day beds in Soutb China were formed by extraterrestrial 877 causes an d tbis point of view is supported by Sun et al. (1984), Xu eta!. (1985); Gupta &Yin (1987) and Yin Texr-fìg.l - Permian-Triassic evenr srrarigraphic- an d biosrra- et al. (1996). After analysis of 45 cbemical elements rigraphic boundaries at rhe Meishan sections, Zhejiang, from the boundary day beds, Clark et al. (1986) China. CONODONT PERMO-TRIASSIC MASS EXTINCTION 491 placing the event stratigraphic- and biostratigraphic Changhsing Limestone and the boundary day beds. boundaries at the same level. Wang (1994) fìrst )· Both the pelagic conodont Clarkina and neritic subdivided the boundary bed 2 into four equal parts conodont Hindeodus (Kozur, 1994a) are repre- and drew the base of the Triassic at the middle of the sented in the Meishan sections. boundary bed 2 (the base ofAEL882-3 ofWang, 1994; or the base of27c ofYin et al., 1996). This proposal has been accepted by the majority of numbers of the DISCUSSION AND CONCLUSION P/TWorking Group (Yin,l995; Yin eta!., 1994, 1996; Wang et al., 1996, 1997; Kozur, 1997; Kozur et al., Conodonts of the P /T boundary beds are very rare 1996). This proposal clearly separates che event in both abundance and diversity, so we can discuss the stratigraphic- and biostratigraphic boundaries and is conodont mass extinction and recovery at the srecies upmost importance no t only for defining the GSSP of level. After analysis of all the foundamenta data the basai Triassic boundary but also for a study of the mentioned above, we reach the following primary P/T mass extinction and recovery (Text-fig. 1). condusions: 5. A study of bioturbation in the Permian/Triassic boundary beds at the Meishan sections has revealed l. The mass extinction ofconodonts was the latest to occur that no vertical burrows effect the boundary beds during the P/T mass extinction. (Bottjer et al., 1988), all microfossils are present in-situ, Some major fossil groups disappeared totally at the and conodonts from the boundary beds do not end of the Permian, but most of these groups (e.g., represent a mixed fauna. This provides an objective trilobites, rugose corals, fusulinids) had a very low basis for a fine scale biostratigraphic study at the diversity and were restricted regionally to the Tethys. centimeter level. These fossile groups disappeared in the latest Permian, 6. Studi es of conodonts from the Meishan sections have but they never extended up to the P /T boundary. They achieved excellent results, all aspects of the fauna, became extinct in a stepwise fashion and some meters including the range of every species, are dear. Even if below the P/T boundary. The fusulinids vanished 5 m there are some differences of opinion among conodont below the top of the Changhsing Limestone in the workers, the following facts are recognized of nearly all Meishan sections. Trilobites, rugose corals and most workers (Wang, 1996; Wang et al., 1996; Kozur et al., ammonoids disappeared within the upper part of the 1996; Zhang et al., 1995; Text-fig.2): Changhsing Limestone. These fossil groups became a. Clarkina subcarinata (Sweet) disappears at the top extinct a few meters below the event stratigraphic of the Changhsing Limestone; boundary (che base of boundary day bed l). Cono- b. Clarkina deflecta (Wang & Wang) an d C xiangxiensis donts retained their abundance and diversity and (Tian) disappear within boundary bed l (or bed extended up to the topmost bed of the Changhsing 26); Limestone(AEL877-879, or bed 24). Conodont c. The range of Clarkina meishanensis Kozur & Wang abundance dropped drastically at the base of the is restricted to boundary bed l (bed 25 and 26); boundary day beds. The topmost Changhsing d. Clarkina carinata (Clark) appeared a little ealier than Limestone bed (AEL877 -879 or bed 24) contains 322 Hindeodus parvus (Kozur & Pjatakova); conodont elements/kg, whereas the boundary day beds e. Clarkina changxingensis (Wang & W an g) ranges up contain only 6 conodont elements/kg (Clark et al., to boundary bed 2, and disappears within its upper 1986). The present author got even fewer conodont part. Except for C carinata (Clark), it is the last elements from the boundary beds (Wang et al., 1995, species of Clarkina to disappear; 1996). Even so, conodont diversity is nearly unchanged f. The range of Hindeodus changxingensis C.Y. Wang is across the event stratigraphic boundary. Only Clarkina limited to boundary bed 2; subcarinata (Sweet) disappeared within the top of the g. The FAD of Hindeodus parvus (Kozur & Pjatakova) Changhsing Limestone. The drastically reduced is within boundary bed 2 (the base of AEL882-3 or conodont abundances should be an importane marker the base ofbed 27c), this level marks the proposed for the conodont mass extinction. Most base of the Triassic (Wang, 1994, 1995; Wang et conodont species such as Clarkina dejlecta (Wang & a/.,1996, Kozur et al., 1996; Yin et al., 1996). Wang), Cxiangxienxix (Tian), Cmeishanensis (Kozur Hindeodus parvus (Kozur & Pjatakova) evolved from & Wang) became extinct in the boundary day beds or Hindeodus latidentatus praeparvus Kozur; in the interval between the event stratigraphic- and h. Isarcicella staeschei Dai & Zhang occurs fìrst in bed biostratigraphic boundaries. This dearly demonstrates 28 at Meishan section A, only 8 cm higher than that, by comparision with other fossil groups, the the FAD of Hindeodus parvus erectus Kozur; conodont mass extinction was the latest to happen. lt i. Conodont abundances decrease markedly from the is dear that the topmost of the Changhsing Limestome, top of the Changhsing Limestone to the boundary boundary bed l, an d the lower part of the boundary day beds, but conodont diversity does not change bed 2 should be assigned to the conodont mass immediately at the boundary between the extinction interval. 492 C. YWANG

"'Tl Changhsing Formation l Yinkeng Formation 3 Changhsingian Stage Griesbachian Stage (/)

l 1 1 r- r- l 11111111 Ili l 1 1 1 l 1111111111111111111111111 l l l l l l l l l l l l l l l (Jl() -- - r--- r- l e- 11111111 Ili l r--- 11111 l 1111111111111111111111111 CO Q. o r- r- l _ l (')c: l 11111111 Ili l l l l l l l l l l l l l l l l l !::!:3 C'l r--- r- - l r- 11111111 Ili l 1 1 111111111111111 1 1111111111 o ::l 3 l- 1 1 1 ::l !ll c- r- l - l 1 1 ...., l l 111111111 Ili l 1 1 1 l 1111111111111111111111111 O> O> 0>0>0>0>0> O> O> O> O> O> O> O> O> O> O> --l --l --l--l--l--lO> 0>0>0> O> O> O> O> O> O> O> .,. U1 Ol--l0>(00 NN W .,. U1 (j) --l W.P.. O. Clarkina carinata 1 . Clarkina cf. carinata 2. C. changxingensis () 3. C. deflecta o 4. C. subcarinata ::lo • • • • • Q.. 5. C. dicerocarinata • o 6. Hindeodus typicalis :::J 7. H. latidentatus (Jl- 8. Clarkina meishanensis ...... 9. Hindeodus parvus Morphotype 1 • • • • • 10. H. parvus Morphotype 2 • • • • 11 . H. changxingensis re 12. H. julfensis - • 13. H. turgidus 14. Clarkina xiangxiensis 15. Ophiceras sp . • 16. Ophiceratids • 17. Lytophiceras sp. • 18. Hypophiceras changxingensis • 19. H. cf. martini :t> • 3 20. Hypophiceras sp. • 3 21 . Metophiceras sp. • o 22. Gryptoceras sp. • ::lo 23. ?Otoceras sp. • a: 24. Tomophiceras sp • (Jl 25. Pseudogastrioceras sp. • 26 . Pachydiscoceras sp. • 27. Rotodiscoceras sp. • 28 . Nautiloidea Gen. et Sp. indet.. • 29. Paracrurithyris pigmaea • f-- 30. Paracrurithyris sp. ....,OJ • !ll 31 . Waagenites barusiensis • (') 32. Paryphylla su/catifera 6" 33. P triquetra • -c 34. P orbicularis o • Q.. 35. Fusichonetes pigmaea (Jl 36 . F. nayunensis !ll • ::l 37 . Neowellerella pseudoutah • Q.. 38. Araxathyris minuta • "'Tl 39. Araxathyris cf. araxensis • (ii" 40. C/araia wangi co 41 . Peribositra baoqingensis • (Jl 42. Fish teeth and scales OJ OJ OJ OJ crO crO crO O" o co c: co c: co c: co c: ::::l ::::l ::::l Q.. ::::l Changhsing Formation a.. Q.. a.. Q.. a.. Q.. -"!ll l\.) !l) VJ!ll (Jlg. -< -< -< -<

Text-fìg.2 - Distribution of major fossils in Permian-Triassic boundary beds at che Meishan sections, Zhejiang, China. CONODONT PERMO-TRIASSIC MASS EXTINCTION 493

2. The conodont mass extinction shows a stepwise The Triassic recovery from the P /T mass extinction character in the short interval ofthe boundary beds. is commonly thought to have taken as long as l O Ma Detailed study of conodont distribution in the (Rong et al., 1996). If the Late Permian Claraioides Meishan sections reveals that conodont species became and the Claraia Bittner can be extinct in a stepwise fashion in the short interval of the distinguished (Fang, 1993), then Claraia Bittner is an boundary day beds. Clarkina cf cari nata (Clark) became excellent recovery taxon of the Early Triassic. Yang et extinct in bed 25 (AEL881); Clakina deflecta (Wang & al. (1987) estimated that it produced a new species Wang) disappeared in the lower part of boundary bed 2 every 0.1-0.2 Ma. But the first appearence of Claraia (AEL882-2); Clarkina xiangxienxis (Tian) also became Bittner is within the boundary bed 3 and thus much extinct in the lower part of boundary bed 2, but a little above the first occurence Hindeodus parvus Kozur & earlier than Clarkina dejlecta (Wang & Wang) (AEL882- Pjatakova and Isarcicella staeschei Dai & Zhang, both 1); Clarkina changxingemis (Wang & Wang) extended of which are new elements that indicate beginning of up and across the P/T boundary, and finally became the recovery. Clarkina planata (Clark) as a descendant extinct in the upper part of boundary bed 2. species of crisis progenitor Clarkina carinata (Clark) is C.changxingemis (Wang & Wang) has a relatively long also a good marker for the conodont recovery, range, which could be a species-richness effect. The P/T especieally in the pelagic facies. The conodont recovery biostratigraphic boundary is 15 cm higher than the event was very fast, Wang ( 1994, 1995) estimated that i t took stratigraphic boundary in the Meishan sections. Wang only about 15,000 years. Bowring et al. (1998) regard (1994, 1995) estimated that this interval could be the age of the basai Changhsingian is 253.4±0.2 Ma about only 15.000 years, but according to Bowring et and the youngest ash of the Changhsingian (bed 25, al. (1998) data, the duration could be 0.35 Ma. 26) is 251.4±0.3 Ma. The Changhsingian duration is Conodont extinction demonstrates a stepwise character 2 Ma, the thickness of the Changhsing Formation is in such a short interval. 42 m. The average accumulation rate is less than 500 years/ l cm, if so the the extinction-survival interval (15 3. No independent survival interval. cm in thick.) is about only 7500 years. But Bowring et Survival intervals proposed by Kauffman & Erwin al (1998, Fig.2) interpret the age ofbed 25, 26 being ( 1995) are characterized in their early and middle parts 251.4±0.3 Ma, and ofbed 28 being 250.7±0.3 Ma, if by the bloom of disaster and opportunistic taxa. In the so the duration of extinction-survival interval would late survival interval, the pre-adapted survivors and be 0.35 Ma. The boundary day beds are very progenitor taxa increas. Ranges of Clarkina meishanemis condensed. Kozur & Wang an d Hindeodus changxingensis C. Y. Wang are very short, limited to boundary bed l and 2 5. No conodont refùgia and Lazarus taxa. of the Meishan sections. These two species might be The nature o(re'rugia is debated, but their discovery regarded as disaster species, or "event species" ofWang and characterization may be essential to future research (1994, 1995). They seem to have the characters of the on survival. From the stand-point of refuge quality, early and middle survival intervals. Clarkina carinata two types of refugia can be distinguished, large and (Clark) is a typical crisis progenitor species in that its stable reservoirs (e. g. the deep ocean/stable refugia) and descendent species, Clarkina planata (Clark) has its first zona! and quickly changing boundaries of systems appearence in the Isarcicella staeschei Zone. Hence, it (stationary refugia) (Hladil & Cejchan, 1995). seems reasonably to assign it to the late survival interval. Most refugia taxa retain their ability to reoccupy But many Changhsingian conodont species became primary habitats from which theywere displaced during ectinct just in these intervals as mentioned above, so the mass extinction, as immigrant survivors. As those these intervals are also typical extinction intervals. We enviroments stabilize, refugia taxa may thus comprise can not distinguish an independent survival interval, Lazarus taxa. Two types of refugia have been recognized so maybe, we could term these intervals extinction- in the biostratigraphic record of mass extinctions: survival intervals (text-fig. 1). Short- and Long-term refugia species (Kauffman & Harries, 1996). 4. Conodonts were the first to recover from the P/T mass An important marker of the biotic recovery interval extinction event. is the presence of the Lazarus taxa. But so far we have As Kauffman & Erwin (1995, 1996) point out, no t found any refugia species or Lazarus species among different dades an d ecosystems recover at diffrent rates the conodonts. Ali conodont animals were nektonic after a mass extinction, commonly giving a stepped and conodont distribution is worldwide, especieally pattern of recovery. The average recovery time from in the pelagic facies. Erwin (1994) proposed that the mass extinction for temperate ecosystems is 1-2 Ma. Late Permian in South China could have been a deep The most specialized clades, especieally benthic ones, ocean/stable refugia. But we have not found concrete commonly disappear first and reappear last during the evidence that any conodont species was a refugia or extinction and recovery intervals. Reef corals provide Lazarus s_pecies. We do not think that ali conodont the best example. species from the boundary beds were refugia or 494 C.YWANG

CONO DON T volcanism (Clark et al., 1986; Kozur, 1994b). Some ZONATION Conodont Zones and ranges of important conodont species 250 Ma ago, huge explosive acidic-intermediate SHALLOW PELAGIC WATER across the Permian-Triassic boundary beds volcanism in the eastern Tethys caused a fall-out of volcanic dust over at least 2 million km 2 in the eastern Hindeodus postparvus !: Tethys an d adjacent areas (Kozur, 1997). Anoxia events "' c: ,m "' were also important contributors to the P/T mass .!!l lsarcicella "' ·;; -5 C1l Q. g c:: isarcica "'o :t i'l extinction. Cfarkina dejlecta (Wang & Wang) and C. .!!1 ."'., !: "' C<. " xiangxiensis (Tian) disappear within the black day bed .!!! "O"'" 0 (.) ,m o (bed 26), which is an excellent marker for the anoxia "O" Jsarcice/la events. ·E' !: :;E "':;E i staeschei .m - "' "' r- *..,"' AKNOWLEDGMENTS "'Q. .!!l .g"' C1l Hindeodus t o o This smdy was begun in China, supported by NSFC. The ·f§ patvus C1l paper is finally finished in the Forschungsinstitut Senckenberg in u i i c: Frankfurt am main, Germany while the author was studying the c: g 1l 0 "'Q) - c: Frasnian-Famennian conodont recovery from mass extinction; it "' o; "' was supported financially by the Max-Planck Sociery of Germany. - "' " "O"' r- "'"'o o" The author wishes ro thank the Max-Planck Society, which E " Q) .!!l .2 "O provided a fellowship during the period this research was carried u c: "O"'" Q) "' "' 2 'ti o r;::: O> :f out. H e also thanks the Forschungs-Institut Senckenberg, especially (/] .!;" "':;E .!!! "O"' .., _Q o" Prof. Dr. Willi Ziegler who kindly provided the library and working g :t i'l"' Q) Hindeodus o .!!1 "O facilities for this research. 0 /atidentatus c: 1ì"' :: Q) Q) i "O §"' ::;; "' 1l .!!! c:: . i'l ·;;; Q) Hindeodus .,"' "' "' ..,"' 'ti .g"' c: REFERENCES Ol praeparvus .!!! tl §"' c: (.) _., o tl "' "'o ;g" Ol -§ .!!! 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