From the Lower Cretaceous of South Korea and Its Paleobiogeographic Implication

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A new ichthyodectiform (Pisces, Teleostei) from the Lower Cretaceous of South Korea and its paleobiogeographic implication

Article in Cretaceous Research · January 2014 DOI: 10.1016/j.cretres.2013.11.007

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Cretaceous Research

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A new ichthyodectiform (Pisces, Teleostei) from the Lower Cretaceous of South Korea and its paleobiogeographic implication

Haang-Mook Kim a, Mee-Mann Chang b,*, Feixiang Wu b, Yang-Hee Kim a a College of Sciences, Department of Geological Environments, Pusan National University, Busan 609-735, Republic of Korea b Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China article info abstract

Article history: Here we report the first ichthyodectiform in the Jinju Biota from the Lower Cretaceous Jinju Formation, Received 5 August 2013 Shindong Group, at Hyojagyo, Jinju City, South Korea. It shows the following ichthyodectiform charac- Accepted in revised form 12 November 2013 ters: 1) jaw teeth in single series; 2) coracoid expanded ventrally; 3) dorsal fin situated posteriorly, with Available online its origin opposite to that of long anal fin. Besides, its caudal skeleton also exhibits certain features often seen in basal ichthyodectiforms and some other primitive teleosts. The fish is noticeably similar to the Keywords: species referred to Chuhsiungichthys from the upper Lower Cretaceous Dobaru and Kumagai formations Jinjuichthys of the Wakino Subgroup of Kanmon Group in Kyushu, Japan, and Chuhsiungichthys tsanglingensis from Ichthyodectiformes Late Early Cretaceous the Jiangdihe Formation of similar age from Chuxiong, Yunnan Province, China. Chuhsiungichthys was, in South Korea turn, comparable with Mesoclupea showchangensis from the upper Lower Cretaceous Shouchang For- Cosmopolitan fishes indicating West Pacific mation in Shouchang and Linhai, and Guantou Formation in Zhuji, Zhejiang Province, China. The latter rising two genera also show the ichthyodectiform characters mentioned above. Nevertheless, the fish from Korea, those referred to Chuhsiungichthys from Japan and China, and Mesoclupea can easily be distinguished from other ichthyodectiforms in their higher body depth and shorter length; proportionally longer head; longer dorsal and anal fins; lower number of vertebrae, with abdominal less than caudal; vertebrae deeper than long. Among them the Jinju fish is distinct from the other two genera in even higher and shorter body, and presence of urodermal. In addition, the Jinju fish is different from Meso- clupea showchangensis in having a much longer dorsal fin and lower number of vertebrae, but different from Chuhsiungichthys tsanglingensis in having a much higher number of vertebrae and more ridges and grooves on the lateral face of vertebrae. Thus, the Jinju fish cannot be referred to either Chuhsiungichthys or Mesoclupea, and establishing a new genus and species for it is warranted. The Asian ichthyodectiforms, Mesoclupea, Chuhsiungichthys, and Jinjuichthys, may most probably form a monophyletic group e Chuhsiungichthyidae, known so far restricted to the upper Lower Cretaceous fresh and/or brackish waters of East Asia. The new ichthyodectiform materials from Korea are better preserved than those from Japan, thereby allowing a relatively complete description of the fish, providing more information for discussion of its phylogenetic position, enriching the diversity of the local fish fauna, and helping us better understand the paleobiogeographical distribution of the group and its geological background. Ó 2013 Elsevier Ltd. All rights reserved.

1. Introduction numerous fossils, including vertebrates, invertebrates, and plants, were collected from the Jinju Formation (see Fig. 2B for the A large-scale paleontological excavation was carried out by geological section of this part of the formation), and the name “Jinju Haang-Mook Kim and his team from the Pusan University in the Biota” was ﬁrst used for these fossils. The Jinju Biota was then period of 2005e2007, in the area close to Jinju city, during the correlated with the Early Cretaceous Jehol Biota from northwestern construction work for broadening the highway between Jibhyeon China, particularly with the fossils from the Yixian Formation. In and Saengbiryang (Kim, 2009; Figs. 1 and 2A). In the excavation, this paper we describe two teleost specimens collected from the Jinju Formation, Shindong Group, Gyeongsang Supergroup at Hyojagyo, Micheon-myeon, Jinju City, South Gyeongsang Province, * Corresponding author. South Korea. They show a close resemblance to the specimens E-mail addresses: [email protected] (H.-M. Kim), [email protected] described by Yabumoto (1994) from the Lower Cretaceous Dobaru (M.-M. Chang), [email protected] (F. Wu), [email protected] (Y.-H. Kim).

survey of the Ichthyodectiformes, and considered the order as a basal teleostean group, sister to Tharsis dubius plus all extant teleosts. A recent work by Cavin et al. (2012) has shed much new light on this group. Although Cavin et al. (2012) excluded Ascalabo- thrissops (Arratia, 2000) and Pachythrissops (Woodward, 1919) from the Ichthyodectiformes in their comprehensive phylogenetic analysis we still cite some characters of these two taxa for the purpose of comparison, wherever information is available. Fish belonging to the Chuhsiungichthyidae (incorrectly spelt as “chuingichthiid”) (Order Ichthyodectiformes) was mentioned by Lee et al. (2001,p. 363) from “the Jinju Formation exposed in Donggogri (Habin- myeon, Dalseong-gun, North Gyeongsang Province)” among other fossil fishes, and listed in Lee et al. (2001), table 1 (p. 358). The age of the Shindong Group, the Jinju Formation being its youngest unit, has been designated as the HauterivianeBarremian by palynolo- gists and ostracod workers, and as Aptian to Albian by mollusc workers (Yang, 1982; Yi et al., 1994; and Choi, 1985 in Lee et al., 2001; Sha et al., 2012). Recently a UePb dating based on detrital zircons of the group was given by Lee et al. (2010) as ranging from the Aptian to Albian. In this paper, we describe the two well- preserved fossil fish specimens from Hyojagyo, Micheon-myeon and compare them with other known ichthyodectiforms, especially Chuhsiungichthys and Mesoclupea. For comparison, a specimen of well-preserved impression of Mesoclupea showchangensis without head region (GMC V 1007-1) is also described in details. We conclude that the specimens from the Jinju Formation described here cannot be assigned to any of the known ichthyodectiforms. Therefore, we must treat them as a new genus and species of the order. However, we feel that a meaningful phylogenetic analysis has to wait for sufficient morphological information of the three Asian forms to emerge from future discoveries. The Jinju fish fauna (Ichthyodectiformes, Osteoglossiformes etc.) is Fig. 1. The geological map of Gyeongsang Basin, the black dot indicates the fish lo- similar in composition to the fish fauna from Kyushu, Japan and cality, the circles indicate cities. southeast China, and forms one and the same ichthyofauna with those from the latter two areas. This ichthyofauna has a slightly younger age and different geological background than the fish fauna from the Jehol Biota, and contained several cosmopolitan fish and Kumagai formations of the Wakino Subgroup of Kanmon forms. Group in Kyushu, Japan (Yabumoto et al., 2006). Yabumoto (1994) established two new species, namely, Chuhsiungichthys yanagidai (from Dobaru Formation) and C. japonicus (from Kumagai Forma- 2. Materials and methods tion), referred to the genus Chuhsiungichthys described by Lew (1974) from the Jiangdihe Formation of similar age from Chux- The material described in this paper consists of two specimens. iong (the Pinyin spelling adopted after 1979 in mainland China that One is a fish skeleton without the caudal portion (PSU V 1011), and has replaced the old spelling of Chuhsiung in Wade-Giles romani- the other is a posterior part of a fish with well-preserved caudal zation), Yunnan Province, China. Yabumoto (1994) was the first to skeleton, caudal fin and relatively large parts of dorsal and anal refer the genus to the early teleost order Ichthyodectiformes fins (PSU V 1012). The specimens are preserved in laminated black (bulldog fish), and he established a new family Chuhsiungichthyi- siltstone, and both the matrix and skeletons are of similar black dae to include Chuhsiungichthys and another genus Mesoclupea, color, which caused great difficulty in preparation. Nevertheless, described by Ping and Yen (1933) from the Lower Cretaceous our preparator, using just thin needles, managed to do a beautiful Shouchang Formation, now designated as the basal part of Aptian job to remove the matrix and expose the bones. A latex peel was (Jingeng Sha, pers. comm. 2013), from Shouchang, Zhejiang Prov- made from a specimen of Mesoclupea showchangensis, GMC V ince, China. Mesoclupea was later discovered also from a wider area 1007-1, to show the postcranial skeleton. The drawings of the and time range, i.e., the Shouchang Formation of Jiande, Zhuji, head and tail of the Jinju fish, and the tail of Mesoclupea were done Chun’an, Pujiang, Linhai, and the Guantou Formation, now desig- based on photos and observation under microscope Wild M7A. nated as early Albian (Jingeng Sha, pers. comm. 2013), of Zhuji, General osteological terminology mainly follows that of Cavin Zhejiang Province (Chang, 1963; Chang and Chou, 1977, 1986; et al. (2012). Chang and Miao, 2004). Mesoclupea and Chuhsiungichthys were Materials for comparison include Chuhsiungichthys tsan- formerly placed in the Chirocentridae (living wolf herring) by glingensis from the upper Lower Cretaceous Jiangdihe Formation, Chang (1963) and Lew (1974) respectively, and Mesoclupea was also Chuxiong, Yunnan Province (specimens IVPP V 4704.1, 2, 6, 13, 24); referred to the Chirocentridae by Bardack (1965). Bardack and Mesoclupea showchangensis from the Lower Cretaceous Shouchang Sprinkle (1969) established a new extinct group of teleosts, the Formation, Shouchang (IVPP V 2683.11, 32), Zhuji (IVPP V 2684.1, 2), Ichthyodectiformes, based on their detailed study on fishes of the Pujiang (GMC V 716-2, 3, V 1007-1, 3), and Linhai (IVPP V 2685.4, 11, two extinct families Ichthyodectidae and Saurocephalidae. 13, 29, 30), Zhejiang Province, China, and Chuhsiungichthys yana- Patterson and Rosen (1977) conducted a comprehensive anatomical gidai (KMNH VP 100,148) from Kyushu, Japan. H.-M. Kim et al. / Cretaceous Research 47 (2014) 117e130 119

Fig. 2. Photograph showing outcrop (A) and geological section (B) of Jinju Formation (modiﬁed from Kim, 2009).

1. Institutional abbreviations dentary; D.f, dorsal fin; ep 1e3, epurals 1e3; Ecpt, ectopterygoid; en, epineural; en.b, epineurals possibly articulating with braincase; PSU, Pusan National University, Busan, Republic of Korea; GMC, Enpt, entopterygoid; epi, epioccipital; eth.pal?, ethmopalatine?; The Geological Museum of China, Beijing, China; IVPP, Institute of Extsc?, extrascapular; fos.Pto, fossa on pterotic for articulation with Vertebrate Paleontology and Paleoanthropology, Chinese Academy hyomandibular; Fr, frontal; h1, hypural 1; h7, hypural 7; Hm, hyo- of Sciences, Beijing, China; KMNH, Kitakyushu Museum of Natural mandibular; Ic, intercalar crest; L.e, lateral ethmoid; Mpt, meta- History and Human History, Kitakyushu, Japan. pterygoid; msc, mandibular sensory canal; Mxr, Mxl, right and left maxilla; n.a, neural arch; n.s, neural spine; Op, opercle; P, para- 2. Anatomical abbreviations sphenoid; P.f, pectoral fin; Pa, parietal; pel.b., pelvic bone; Pcl, postcleithrum; ph, parhypural; Pmx?, premaxilla?; Pop, pre- A.f, anal fin; a.pt, anal pterygiophores; Ang, angular; art. Hm, opercle; pr. bpt?, basipterygoid process?; pr.cor, coronoid process; articular area on hyomandibular; Cl, cleithrum; cor, coracoid; Den, pr.r, procurrent rays; Pto, pterotic; Pttr, Pttl, right and left post- 120 H.-M. Kim et al. / Cretaceous Research 47 (2014) 117e130 temporal; pu1, preural centrum 1; qu, quadrate; Rode, ros- Paratype. PSU V 1012, the posterior part of a fish skeleton, with trodermethmoid; Scl, supracleithrum; Smx 1, supramaxilla 1; Smx well-preserved caudal skeleton and caudal fin(Fig. 6A, B). 1?, supramaxilla 1?, Smx 2, supramaxilla 2; sn, supraneural; Sop, Derivation of name. The species name is in honor of the famous subopercle; tbh, thickened laterally flared bases of upper hypurals; geologist Cheong Chang Hi, the former president of the u1, ural centrum 1; u2, ural centrum 2; Ud, urodermal; un 1e5, Geological Society of Korea, member of the Korean Academy of uroneurals 1e5; vert, vertebrae. Sciences, who made great contributions to the biogeography of Korea. 3. Systematic paleontology Diagnosis. See the generic diagnosis. Locality and horizon. Hyojagyo, Micheon-myeon, Jinju City, Subdivision Teleostei Müller, 1844 South Gyeongsang Province, South Korea (351905300N, Order Ichtyodectiformes Bardack and Sprinkle, 1969 1280500500E) (Fig. 1); Jinju Formation, Shindong Group, Family Chuhsiungichthyidae Yabumoto, 1994 Gyeongsang Supergroup, the Lower Cretaceous. Jinjuichthys gen. nov. Derivation of name. Jinju-, name of the city, to which the locality belongs; -ichthys, fish in Greek. 4. Description Diagnosis. Middle-sized ichthyodectiform with the following combination of characters: body comparatively deep, with 1. General appearance (Figs. 3 and 6A) standard length/body depth ratio as 2.7, deepest among ichthyodectiforms; tooth-bearing margin of dentary short, about Although the holotype PSU V 1011 lacks the posterior part one third of dentary length, and inclined forward; origins of behind the second preural centrum, the paratype PSU V 1012 has dorsal and anal fins opposite to each other, dorsal fin relatively the well-preserved posterior part of the body skeleton. It can be long, falcate, with ca. 20 branched rays, ca. 40 anal fin rays, seen from the paratype that the distance from the anterior border pelvic fin in the middle of the distance between pectoral and of the preural centrum 1 to the posterior margin of the hypurals anal; vertebral centra 50, with less abdominal (22) than caudal approximately equals to the length of the five vertebral centra in (28), their lateral side bearing 4e5 ridges and grooves; 7 front of the pu1. By adding the estimated length of the missing part hypurals, upper ones with thickened bases, exposed between to the holotype, its standard length is approximately 187 mm. The last uroneural and proximal part of first upper branched caudal body is rather deep, with a standard length/body depth ratio ray on dorsal side, and second upper branched caudal ray on roughly as 2.7. The maximum depth of the body is situated just ventral side; 5 uroneurals, most anterior one extending to dorsal anterior to the origin of the dorsal fin. The head is slightly longer side of border between pu 2 and pu 3 or slightly forward; 3 than deep, with its length/depth ratio as 1.1. The standard length is epurals, 1 urodermal, 12 upper procurrent rays, 8 lower ones. ca. 3.8 times of the head length and ca. 4.2 its head depth. The jaw Type and only species. Jinjuichthys cheongi, gen. et sp. nov. bones are disturbed, and hence it is difficult to determine whether Jinjuichthys cheongi, gen. et sp. nov. or not the gape is slightly upturned. Both dorsal and anal fins are Holotype. PSU V 1011, a fish skeleton with the caudal region posteriorly situated with their origins nearly opposed to each other. missing, with the upper jaw bones dislocated, and bones in the The anal fin is rather long, and the dorsal fin is much shorter than skull roof incompletely preserved (Figs. 3, 4A, B, 5). the anal as in other ichthyodectiforms. The few anterior rays of the

Fig. 3. Jinjuichthys cheongi, gen. et sp. nov., photograph of holotype PSU V 1011, a ﬁsh skeleton without caudal region, in right lateral view. H.-M. Kim et al. / Cretaceous Research 47 (2014) 117e130 121

Fig. 4. Jinjuichthys cheongi, gen. et sp. nov. A, Photograph of the head of the holotype, in right lateral view. B, Box area in A.

Fig. 5. Jinjuichthys cheongi, gen. et sp. nov. Drawing of the head of the holotype, in right lateral view. 122 H.-M. Kim et al. / Cretaceous Research 47 (2014) 117e130

Fig. 6. Jinjuichthys cheongi, gen. et sp. nov. A, Photograph of the paratype PSU V 1012, the posterior part of a fish, in right lateral view. B, Drawing of caudal skeleton and bases of caudal fin rays, the arrows point to the outermost (unbranched) principal caudal fin rays. H.-M. Kim et al. / Cretaceous Research 47 (2014) 117e130 123 dorsal fin in the paratype are much longer than the posterior ones, be seen from the lateral side, and the retroarticular is probably not making the fin look somewhat falcate, but the shape of the anal fin preserved. A small elongated and slightly bent bone that is situated cannot be distinguished due to the incomplete preservation. The behind the upper end of the left maxilla in the holotype is probably pelvic fin is situated more or less in the middle of the distance a premaxilla, with its thicker end gradually tapering towards the between the pectoral and anal fins. Because the anal fin is quite other end. Both left and right maxilla are clearly shown, though long, the caudal peduncle is pretty short. The caudal fin is deeply displaced, with their lower ends pushed forward. A tiny part of the forked. ventral margin of the right maxilla shows three serrations, indicating that the mouth margin of the maxilla is serrated. The left 2. Skull roof (Figs. 3, 4A and 5) supramaxilla 2 and possibly even the supramaxilla 1 are still in situ, i.e., attached to the posterodorsal side of the left maxilla, with the The sutures between the skull roofing bones are not very clear, complex of the three bones pushed forward, and the outer surface yet most of the bones can still be recognized from their main fea- exposed. The right supramaxilla 2 is shifted upwards to the upper tures. The rostrodermethmoid is the most anterior bone in the skull part of the orbit, but it can still be recognized by its typical shape in roof, though no ethmoid commissure is detected on this bone. A basal teleosts, i.e., consisting of a posterior large oval-shaped part relatively broad process projects ventrolaterally from the bone. and an anterodorsal, narrow, rod-like part. A bone lying close to the From the anteroventral margin of this process a small, thin bone Smx 2 with a narrow, rod-like anterior part and a slightly expanded extends forward and downward. We are uncertain whether this posterior part may be regarded as the right Smx 1. small bone is an upwardly shifted ethmopalatine. The lateral ethmoid is a long rectangular bone, extending from the ante- 5. Bones of palate and hyoid arch (Figs. 4A and 5) roventral margin of the frontal downward and forming the anterodorsal border of the orbit. The frontal is tightly sutured with the The parasphenoid, visible across the orbit, is observed in the rostrodermethmoid. Behind the frontal is the parietal. Since the holotype. A small outgrowth, going upwards from the para- median margin of the parietal is rather smooth, the two parietals sphenoid close to the posterior margin of the orbit, most probably are apparently not fused. Lateral to the parietal is the pterotic, is the remnant of the basipterygoid process of the bone. The lower including its dermal and endochondral portion. The surface of its side of the parasphenoid has no teeth. In front of the quadrate and dermal portion shows that branching ridges possibly contain the behind the angular is an elongated bone, bent in the middle, which otic section of the infraorbital sensory line, whereas the ventral part is probably the ectopterygoid. Remains of bony substances under of its endochondral portion shows the articular area for the hyo- the parasphenoid, and posterodorsal to the quadrate, may possibly mandibular head. The supraoccipital crest is not seen, which must belong to the entopterygoid and metapterygoid. No teeth are seen be comparatively low, whereas the epioccipital crest is prominent. from these bones either. The quadrate, as is typical for teleosts, The intercalar shows a pronounced, thick lateral ridge. Behind the consists of a fan-shaped plate and a rod-like ventral process. The parietal and epioccipital is an elongated bone plate, which is anteroventral articular head of the bone fits into the socket at the probably the extrascapular. posterodorsal end of the angular. Most part of the hyomandibular is exposed in front of the preopercle. It has a thick, triangular dorsal 3. Opercular series (Figs. 4A and 5) part with the articular area, which fits into the hyomandibular fossa on the ventral side of the pterotic in the braincase. The base of the Although the top part of the opercle is covered by the first few articular process for the opercle can also be discerned. vertebral centra, the exposed part of the bone shows that it is somewhat oval, with straight anterior margin. The peripheral area 6. Paired fins and girdles (Figs. 3, 4A and 5) of its surface displays faint, radiating striations. The preopercle has its vertical branch longer than the horizontal one. Because of the The dermal pectoral girdle consists of a large, bent cleithrum, an incomplete preservation, it is difficult to tell the extension of its elongated, ovoid supracleithrum, and a post-temporal with rather posterior and ventral margins. The interopercle and subopercle are thin and long dorsal and ventral branches, much longer than in present, but their ventral margins are broken. Neither the bran- other ichthyodectiforms and most basal teleosts. A third branch or chiostegal rays nor the circumorbital bones are observed. process of the post-temporal runs forward from the middle of the bone, probably attached to the intercalar (see Bardack, 1965). The 4. Jaws (Figs. 4A, B and 5) main part of the post-temporal in other ichthyodectiforms is plate- like, e.g., in Xiphactinus (Bardack, 1965, fig. 12), Allothrissops The mouth gape is not very long. The articulation of the lower (Patterson and Rosen, 1977, fig. 10), Thrissops (Taverne, 1977, fig. 5) jaw with the quadrate is slightly posterior to the level under the etc. The cleithrum has more or less equally broad vertical and middle of the orbit. The lower jaw is deep. The tooth-bearing horizontal branches. The upper tip of the vertical branch is pointed. margin of the dentary is comparatively short, occupying approxi- The ventral end of the supracleithrum covers the upper tip of the mately one third of the length of the bone, inclined forward, similar cleithrum, and its dorsal end is connected with the ventral branch to Allothrissops (Patterson and Rosen, 1977, figs. 5, 9) and Occi- of the post-temporal. A disarticulated long bone lying across the thrissops (Schaeffer and Patterson, 1984, fig. 24; also see Alvarado- ventral branch of the cleithrum in the holotype, though most Ortega and Brito, 2010, figs. 7A, B), and carrying more than 20 more probably displaced, may be one of the postcleithra, with a narrow, or less uniform small teeth, which are pointing somewhat medially rod-like upper half and a slightly broadened lower half. Two similar (Fig. 4B). The relatively high coronoid process is situated approxi- bones with their lower halves exposed underneath the posterior mately at the mid-length of the mandible. The ventral margin of the margin of the cleithrum in the same specimen would also be the dentary is slightly convex. The mandibular sensory canal goes un- postcleithra from the same side. Thus, the postcleithra would, at der a shallow groove parallel to the lower margin of the dentary, least, be three from each side. They are all elongated, thin bones. In with about six or seven sensory pores opening at the bottom of the other ichthyodectiforms, where these bones are mentioned, their groove. From the lateral side of the lower jaw the angular bone can number ranges from two to three, e.g., two in Antarctithrissops clearly be seen, with the lateral part of the articular facet for the australis (Arratia et al., 2004), Vallecillichthys multivertebratum quadrate situated at its posterodorsal corner. The articular cannot (Blanco-Piñón and Alvarado-Ortega, 2007), Ogunichthys triangularis 124 H.-M. Kim et al. / Cretaceous Research 47 (2014) 117e130

(Alvarado-Ortega and Brito, 2010), Eubiodectes libanicus (Cavin rays were seen in Occithrissops willsoni (Schaeffer and Patterson, et al., 2012) etc., and three in Cladocyclus and Allothrissops 1984), and 8 upper and 10 lower procurrent rays in Eubiodectes (Patterson and Rosen, 1977). They are on the whole plate-like libanicus (Cavin et al., 2012). No caudal scutes are seen on the Jinju bones. In primitive teleosts, such as Varasichthys ariasi, the num- fish. ber of postcleithra reaches up to six (Arratia, 1984). Unfortunately, the number of postcleithra is unknown in Mesoclupea and Chuh- 9. Axial skeleton (Figs. 3, 4A, 5 and 6A, B) siungichthys. The endoskeletal girdle is not well-preserved. Judged from the broken bony pieces ventral to the cleithrum, the coracoid There are 50 vertebral centra in the axial skeleton, among which may be rather large. The pectoral fin is not completely preserved. 22 are abdominal and 28 are caudal. Similar to C. tsanglingensis (17 There are more than 11 rays, of which the first few are robust. abdominal and 23e25 caudal) and M. showchangensis (23e24 Segmentations can be detected in most of the rays some distance abdominal and 30 caudal) but different from most ichthyodecti- from their proximal end. Since their distal parts are not preserved, forms, the number of the abdominal vertebrae is obviously less we are not sure whether the rays are branched distally. The pelvic than that of the caudal. All centra are deeper than long, and the bone is relatively thick, with its anterior end thinner than the lateral side of each centrum bears four to five well-developed, posterior. The fin rays are too dislocated to show their exact horizontal ridges and grooves in between. The neural and hemal number. arches are on the whole autogenous except a few hemal ones that are fused to the vertebrae in the caudal region. Long rod-like 7. Unpaired fins (Figs. 3 and 6A) supraneurals are present in front of the dorsal fin pterygiophores. Their exact number is unknown because the supraneurals in the The dorsal fin rays are more or less completely preserved in the area behind the occipital region are either missing or dislocated. paratype. With the impressions of their anterior ones taken into There are numerous (more than 10) thin bones in the area behind account, there are about 20 branched rays in the dorsal fin. The the braincase and above the first few vertebrae. They might have anterior unbranched and unsegmented fin rays are not preserved, attached to the dorsal side of these vertebrae and/or to the back of and thus are not included in the count. The individual length of the the braincase. They may represent epineurals articulating with the anterior seven branched rays decreases rapidly backward, whereas braincase, as the case in Cladocyclus (Patterson and Rosen, 1977, the posterior ones are short and almost with equal length, thus p.105e106). Several disarticulated neural spines with neural arches making the fin look falcate. The anal fin is not complete in either and epineurals are found in the anterodorsal part of the body, be- specimen, but by counting the pterygiophores of the fininboth tween the head and the dorsal fin (Figs. 3 and 4A). Otherwise, no specimens we are able to estimate that there are approximately 40 epineurals are seen along the dorsal side of the vertebral column in rays in the fin, though the shape of the fin cannot be reconstructed. the holotype. This may be due to the poor preservation. No epi- Although not sufficiently well-preserved, we can still see from the pleurals are observed. Twenty-one or 22 pairs of ribs can be holotype that the first few anal pterygiophores are most possibly counted. arranged in cluster and extended into the interhemal spine space. 10. Scales 8. Caudal skeleton and fin (Figs. 6A and B) No complete scales are preserved in either of the specimens. The caudal skeleton and fin are very well shown in the paratype. From the small pieces of scales left on the body we can only tell that Five neural and four hemal spines (excluding the parhypural) are they are cycloid, rather thin, and with very fine, dense concentric prolonged and involved in supporting the procurrent caudal fin circuli. rays. As in other primitive teleosts, there are two ural centra. The first articulates with the two lower hypurals, whereas the second e 5. Discussion and conclusion with the five upper hypurals. All upper hypurals have thickened laterally flared bases, which are exposed between the first uro- 5.1. Phylogenetic position of the Jinju fish neural and the proximal part of the first upper branched caudal ray on their dorsal side, and the second branched caudal ray on their The fish described here shares the following characters with the ventral side. The hypurals 5e7 are almost entirely covered by the Ichthyodectiformes defined by Patterson and Rosen (1977):1)a bases of the caudal fin rays of the upper lobe. There are five uro- long anal fin and a falcate dorsal fin situated posteriorly, with its neurals (described as three in Chuhsiungichthys tsanglingensis, Lew, origin opposite to that of the anal; 2) teeth in a single series in the 1974). The anterior tip of the first uroneural is somewhat enlarged jaws; 3) coracoid large and expanded ventrally. Among the char- and, together with the second one, extends to the anterior border of acters of the Ichthyodectiformes mentioned by Patterson and Rosen the pu 2 or even slightly further forward, and covers the dorso- (1977), the presence of the ethmo-palatine ossification is uncertain lateral side of the pu 1 and pu 2, similar to the situation in Chuh- in the Jinju specimens, the uroneurals are one fewer than six, and siungichthys (Lew, 1974, fig. 2) and Occithrissops (Schaeffer and the anterior uroneurals do not cover the lateral but dorsolateral Patterson, 1984, fig. 29), though only extending to dorsolateral surface of the first few preural centra. Nevertheless, there is a side of the pu 1 in the former, and that of the pu 3 in the latter. The similar situation in some basal ichthyodectiforms, e.g., Occi- other three are shorter and taper towards both ends. There are thrissops, which resembles Allothrissops and Thrissops in many three rod-like epurals. No definite rudimentary neural arches on u 1 other ways (Nybelin, 1964; Schaeffer and Patterson, 1984). We thus and pu 1 are detected. A distinct urodermal is observed, as it often still suggest the Jinju fish be referred to the group on the basis of the occurs in Thrissops formosus (Patterson and Rosen, 1977, figs. 13, 14), characters enumerated above. lying over the proximal end of the upper unbranched principal ray. The Jinju fish is different from most ichthyodectiforms in the The caudal fin is deeply forked. The number of principal caudal fin following respects: rays is the same as that in most primitive teleosts, i.e., one unbranched and nine branched in the upper lobe, and eight branched 1) Its body is much deeper and shorter as compared to other ich- and one unbranched in the lower lobe (I, 9, 8, I). There are 12 upper thyodectiforms, and the standard length (SL) is only 2.7 times and 8 lower procurrent rays. Eight upper and 7 lower procurrent the maximum body depth. The body is usually elongate and H.-M. Kim et al. / Cretaceous Research 47 (2014) 117e130 125

slender in almost all other ichthyodectiforms, whereas in Mes- and most of basal teleosts. In the latter forms the post-temporal oclupea showchangensis, Chuhsiungichthys tsanglingensis, and is more or less flat, plate-like. Lew (1974) mentioned the two the two species from Kyushu, Japan, referred to the genus long branches of the bone, which can also be seen in his Chuhsiungichthys, i.e., C. yanagidai and C. japonicas, the ratio is reconstruction of the fish (fig. 1). Though Yabumoto (1994) did closer to the Jinju fish. not comment on the branches in his description, we can still see 2) The head in the Jinju fish is proportionally longer (3.8 times in the three comparatively long branches of the post-temporal in SL) than that in other ichthyodectiforms. Again, in the few Asian his drawing of Chuhsiungichthys yanagidai (figs. 18, 19). fishes the ratio is closer to that of the Jinju fish. 3) The number of vertebrae (50) in the Jinju fish is less than that in Among ichthyodectiforms the Jinju fish is most similar to the most ichthyodectiforms, and, different from the latter, the species formerly referred to the genus Chuhsiungichthys from the abdominal vertebrae (22) are fewer than the caudal ones (28). Lower Cretaceous Kumagai Formation of the Kanmon Group in The number of vertebrae in other ichthyodectiforms are more or Kyushu, Japan (Yabumoto, 1994), and, to a lesser extent, to the type even numerous, and, quite the opposite, the abdominal verte- species of the genus, C. tsanglingensis, from the Jiangdihe Formation brae are more than the caudal ones. In the other few Asian of the similar age in Chuxiong, Yunnan Province, China (Lew, 1974). forms, the number of vertebrae is comparable to that in the Jinju Though a number of measurements and meristic characters could fish, and the abdominal vertebrae are fewer than caudal. not be precisely confirmed on the specimens referred to Chuh- 4) The dorsal fin in the Jinju fish is the longest compared with all siungichthys from Japan, owing mainly to their poor preservation, known ichthyodectiforms except Chuhsiungichthys. The fin the Jinju fish is still closest to them judged by the range of body contains more than 20 rays, with the unbranched anterior short proportion, position and shape of dorsal and anal fins, and the ones taken into account, which are not preserved in the avail- number of dorsal and anal fin rays (see above). able specimens but usually present in teleosts. The number of The Jinju fish has a higher body than that in Chuhsiungichthys dorsal fin rays is obviously lower in other ichthyodectiforms, tsanglingensis, with the ratio of SL/BD as 2.7 in the former and 3e3.7 including Mesoclupea showchangensis. In C. tsanglingensis the in the latter. Its post-temporal bears very long dorsal and ventral number of dorsal rays is III 18e20 according to Lew (1974), branches. The number of its vertebrae (50 or 51) is evidently higher whereas four short, unsegmented and unbranched, and 21 than that in the latter form (40e42), the lateral face of vertebrae branched rays are counted by us in specimen IVPP V4704.13 of bears more ridges and grooves (4e5) than in the latter (2e3, Lew, C. tsanglingensis, comparable to that in the Jinju fish, and in 1974), and the uroneurals are more in number (5) than in C. tsan- C. yanagidai and C. japonica the number is similar. glingensis (3, Lew, 1974) and extending further forward. There are 5) The anal fin in the Jinju fish is also amongst the longest one in three epurals and one urodermal in the Jinju fish, whereas in C. ichthyodectiforms except the Asian forms. tsanglingensis those were not observed. In Mesoclupea showchangensis the SL/BD ratio is 2.7e3.4, the number of its vertebrae is See Table 1 for detailed meristic information of the above five 53e54, the number of dorsal rays (III 11e14) is much less than that aspects. in Chuhsiungichthys and the Jinju fish, and there is no urodermal (pers. obs.). For all these reasons, we do not think the fish from Jinju 6) The post-temporal in the Jinju fish has rather long dorsal and can be referred to either Chuhsiungichthys or Mesoclupea, and ventral branches, much longer than in other ichthyodectiforms suggest a new genus and species name for the Jinju fish e

Table 1 Meristic characters of ichthyodectiform fishes. Abbreviations: SL ¼ standard length; BD ¼ maximal body depth; HL ¼ head length; VN ¼ number of vertebrae; AV ¼ number of abdominal vertebrae; CV ¼ number of caudal vertebrae; DF ¼ dorsal fin rays; AF ¼ anal fin rays; C. ¼ Chuhsiungichthys; M. ¼ Mesoclupea. This table was compiled based on both our own observations and those from Chang, 1963; Nybelin, 1964; Bardack, 1965; Bardack and Sprinkle, 1969; Lew, 1974; Patterson and Rosen, 1977; Schaeffer and Patterson, 1984; Taverne, 1986; Arratia, 2000; Arratia et al., 2004; Alvarado-Ortega, 2004; Blanco-Piñón and Alvarado-Ortega, 2007; Alvarado-Ortega and Brito, 2010; and Cavin et al., 2012. Different authors’ calculations vary slightly but on the whole they are comparable. The SL/BD and SL/HL in Unamichthys espinosai are estimated from Alvarado-Ortega, 2004, fig. 1A, B.

TAXA SL/BD SL/HL VN (AVþCV) DF AF

Allothrissops 4.1e6 4.5e6.25 58e63 (3135þ2629) 13e15 25e32 Chirocentrites 6.6 6 62 (33þ28) 15 >34 Proportheus 5.5 5.5 w60 e >30 Spathodactylus <5 >5 60? (w28þ32) Short w30 Thrissops 4e4.1 4e6.5 58e60 (3234þ2628) 13e14 30e32 Antarctithrissops australis Body elongate e 56e57 (>30þ22/23) 14 20 Ascalabothrissops Body elongate 3.6 41 (22þ19) >14 e Cladocyclus gardneri Body elongate Body elongate 64 (37þ27) ee Eubiodectes libanicus 5.2e4.7 5.5e7.1 62e68 (25e31 caudal) 13e15 36e40 Gillicus 6 6.5 69 (42þ27) ee Ichthyodectes 6 6.5e768e72 (4144þ2627) 10 ?10e11 Occithrissops willsoni Body elongate 5.5 58 (3334þ2223þ2 ural) III 10 or 11 IV or V 18e20 Ogunichthys triangularis 5 5.5e5.9 59 (33þ24) III 13 III 32e34 Pachythrissops 3e3.3 4 50e54 (24e25 caudal) 17e18 20e22 Saurodon Body elongate 6 99e100 ee Unamichthys espinosai >6 >678e80 (4546þ3234) w15 III >29 Vallecillichthys multivertebratum Body elongate e >90 (73þ>17) Short e Xiphactinus 5.5 5.5e685e89 (5257þ2933) 15 12e14 Asian taxa C. tsanglingensis 3e3.7 3e440e42 (17þ2325) III 18e20 39e40 C. yanagidai 3.6 4.0 40e42 (21þ24) 20 32 C. japonicus 2.4e2.5 4.2 e 21 39 M. showchangensis 2.7e3.4 3.4e4.1 53e54 (23/24þ30) III 11e14 III 43 Jinjuichthys cheongi 2.7 3.8 50 (22þ28) >20 ca. 40 126 H.-M. Kim et al. / Cretaceous Research 47 (2014) 117e130

Jinjuichthys cheongi. Whether the two species from Kyushu, Japan, somewhat falcate. The caudal skeleton (Fig. 8A, B) is similar to that initially referred to Chuhsiungichthys, would eventually be allocated of Occithrissops willsoni and Jinjuichthys cheongi. It has two lower to Jinjuichthys remains to be seen till better preserved materials and five upper hypurals, the latter with thick bases flared laterally, from Kyushu emerge. exposed between the uroneurals and the upper unbranched prin- ciple ray. Five uroneurals are observed, with the first one extending 5.2. Relationships of Mesoclupea forward to the dorsolateral side of pu 3, but no uroneurals cover the lateral side of any vertebra. Only one epural is detected. There are Mesoclupea was first described by Ping and Yen (1933) as a 12 upper and 8 lower procurrent rays. Four neural and four hemal member of the family Clupeidae. After studying newly collected spines are prolonged and involved in supporting the procurrent materials, Chang (1963) moved it to the family Chirocentridae of caudal fin rays. No urodermal and caudal scutes are observed. the order Clupeiformes. While working on the anatomy and evo- Chang (1963) mentioned the rear position of the dorsal fin and lution of the Chirocentridae, Bardack (1965) also included Meso- substantial length of the anal fin, a single series of conical teeth on clupea in this group. Later, based on their comprehensive work on jaws, and deeper than long scales in Mesoclupea showchangensis the Saurocephalidae and Ichthyodectidae, Bardack and Sprinkle (Chang, 1963, pl. II, figs 2, 3, 4), similar to the shape of scales in (1969) set up a new order Ichthyodectiformes for these fishes. many ichthyodectiforms, e.g., Xiphactinus, Gillicus, Ichthyodectes, Patterson and Rosen (1977) thoroughly reviewed the Ichthyo- Thrissops, Eubiodectes libanicus, and Garganoichthys decosmoi dectiformes and stated that the available information was insuffi- (Bardack, 1965, fig. 13; Arratia et al., 2004, fig. 9C; Cavin et al., 2012, cient for Mesoclupea to be assigned to any teleostean subgroup (p. p. 21; Taverne, 2009, fig. 6). She also described the impression of a 90). However, Yabumoto (1994), Blanco-Piñón and Alvarado-Ortega mesethmoid in specimen GMC V 716-2, but did not mention any (2007), and Cavin et al. (2012) all considered the possibility of in- other structures in the ethmoid region because of the inadequate clusion of Mesoclupea in the Ichthyodectiformes. Obviously, to preservation of the studied materials. When investigating fossil fish clarify the phylogenetic position of Mesoclupea means to wait for from Kitakyushu, Japan, Yabumoto (1994) established a new family better preserved specimens to emerge for further study. Chuhsiungichthyidae within the Ichthyodectiformes, which Before collecting new fossils, we examined all available speci- included Chuhsiungichthys tsanglingensis, the two species he mens again and made a latex peel of a specimen from the referred to Chuhsiungichthys, i.e., C. yanagidai and C. japonica, and Geological Museum of China, GMC V 1007-1 (Figs. 7 and 8A). It is an Mesoclupea showchangensis. Shen, in her doctoral dissertation impression of a posterior body portion of Mesoclupea show- (1997), named a new species of the genus Mesoclupea, M. shixiensis, changensis from Pujiang, Zhejiang Province, with well-preserved from the Lower Cretaceous Shixi Formation of Jiangxi Province, dorsal and anal fins and caudal skeleton. The specimen and the China. This species shows large coracoids (Shen, 1997, p. 28, fig. 2- peel show that the dorsal fin is rather small, with only III 14 rays, 11D). She considered Mesoclupea as an ichthyodectiform based on and its origin is situated behind the level of that of the anal. The single series jaw teeth, enlarged coracoid, and posteriorly posi- anal fin is long, with III 40 rays, comparable to those described by tioned dorsal fin, which are three of the five characters defining the Chang (1963). The first few anal pterygiophores are arranged in Ichthyodectiformes by Patterson and Rosen (1977). She also cluster and extended into the interhemal spine space. Both fins are accepted Yabumoto’s (1994) suggestion and included Mesoclupea in

Fig. 7. Mesoclupea shouchangensis Ping and Yen, 1933. Photograph of GMC V 1007-1, the impression of posterior part of a ﬁsh skeleton, in left lateral view. H.-M. Kim et al. / Cretaceous Research 47 (2014) 117e130 127

Fig. 8. Mesoclupea shouchangensis Ping and Yen, 1933. A, Photograph of a part of the caudal skeleton and bases of caudal fin rays of the latex peel made from GMC V 1007-1, in right lateral view. B, Drawing of the same part, the arrows point to the outermost (unbranched) principal caudal fin rays. 128 H.-M. Kim et al. / Cretaceous Research 47 (2014) 117e130 the family Chuhsiungichthyidae. In the recent work of Cavin et al. caudal, and vertebrae are deeper than long (see above for detailed (2012), Mesoclupea was regarded as a possible basal ichthyodecti- meristic information). They also share a few characters that also form. We agree with Shen on referring Mesoclupea to the Ich- occur in other primitive teleosts, e.g., jaw teeth more or less uni- thyodectiformes, for the same reasons as she explicitly stated. form, gape small, supraoccipital crest low, etc. Both Mesoclupea and Opinions are diverse on the age of the Shouchang Formation, in Jinjuichthys have 4e5 ridges on the lateral side of the vertebrae, which Mesoclupea was discovered. A Late Jurassic age was sug- whereas in Chuhsiungichthys tsanglingensis and other forms the gested by the mollusc workers (Gu, 1962), which had a strong in- ridges are fewer, though the exact number of the ridges in Chuh- fluence in the circle of workers who studied the late Mesozoic siungichthys still depends on the preservation of the materials. In biotas from East Asia. Chang (1963) supported this view, with a Mesoclupea and Jinjuichthys the first few anal pterygiophores are supplement of the relatively primitive teleost characters of Meso- arranged in cluster and extended into the interhemal spine space, clupea, which she, at the time, thought similar to Thrissops. In the and four to five neural and four hemal spines are prolonged and last two decades or so, when radiometric dating became available, involved in supporting the procurrent caudal fin rays. Based on the many works have been published on isotopic studies of the age of shared characters just mentioned, the three genera may most the deposits concerned (Hu et al., 1982; Li et al., 1989; Yu and Xu, probably form a monophyletic group, as it was already named as 1999; Yu et al., 2008). The Shouchang Formation was dated much the family Chuhsiungichthyidae within the Ichthyodectiformes by younger than we had assumed before, e.g., as 117e124 Ma by Yu Yabumoto (1994), though a strict phylogenetic analysis has not yet and Xu (1999). And the Early Cretaceous age has gained more been performed for lack of better preserved materials. All the three creditability, which was estimated by works on concostracans, os- genera are late Early Cretaceous in age, i.e., not the earliest mem- tracods, and other groups and on sedimentology (Jiang et al., 1993; bers of the Ichthyodectiformes, but with primitive features of the Chen, 2012; Wang et al., 2012). Though no consensus has been group, and so far known restricted to fresh and brackish waters of reached, the age of the Shouchang Formation is now widely East Asia. Jinjuichthys is associated with Wakinoichthys (an osteo- accepted as the Early Cretaceous instead of the Late Jurassic. Some glossomorph, Yabumoto and Yang, 2000) and “Lepidotes”, and the (Chen, 2000, 2012) proposed the age of the formation to be the fish-bearing deposits are purported to be correlated with the Nip- Barremian or HauterivianeBarremian, whereas others considered ponamia e Wakinoichthys (Dobaru Formation) and Diplomystus e it the Aptian (Jingeng Sha, pers. comm. 2013). Mesoclupea has also Wakinoichthys (Kumagai Formation) Zones of the Wakino Subgroup been found from the Guantou Formation from Zhejiang, the age of (Lower Cretaceous) in Japan (Lee et al., 2001). According to which has also been designated variously, as the Aptian (Sha, 2007; Yabumoto et al. (2006), some species of the Albuliformes and Elo- Chen, 2012) and Aptian to earliest Albian (Hu et al., 2012b; Luo and piformes were also found from the Jinju (Dongmyeong) Formation, Yu, 2004; Jingeng Sha, pers. comm. 2013). and the deposits were formed near the sea. Mesoclupea has been discovered only in the freshwater Shouchang and Guantou for- 5.3. An Asian freshwater or non-marine group of mations. The phylogenetic study on this East Asian non-marine Ichthyodectiformes e Chuhsiungichthyidae group and their exact age and environment would certainly shed light on understanding the evolution of the Ichthyodectiformes and The Ichthyodectiformes is a very widespread, extinct group of related paleobiogeographical issues. late Mesozoic fishes, having already been discovered from all continents of the world (Woodward, 1919; Ping and Yen, 1933; 5.4. Paleogeographical zonations and geological background of the Schaeffer, 1947; Bardack, 1965; Schaeffer and Patterson, 1984; Early Cretaceous fish faunas in East Asia Lees and Bartholomai, 1987; Maisey, 1991; Yabumoto, 1994; Taverne and Chanet, 2000; Arratia et al., 2004; Alvarado-Ortega, In their discussions of the Mesozoic fishes in Asia, Chang and Jin 2004; Forey and Cavin, 2007; Alvarado-Ortega and Brito, 2010; (1996) and Chang and Miao (2004) suggested to subdivide the Early Taverne, 2008, 2009, 2010; Mkhitaryan and Averianov, 2011, etc.). Cretaceous fish fauna from the mainland Asia, Korea and northern Most members of this group were marine and only a few were non- Kyushu, Japan into three assemblages, based on its composition. marine or freshwater (Maisey, 1996). So far reported from fresh and These three assemblages are distributed in three NE to SW brackish waters are only the following forms: cladocyclids from the stretched areas adjacent to each other. They are the upper Hauterivianelower Barremian and Aptianelower Albian of archaeomaenid-like “pholidophoriform” assemblage in the north- the rift basins of the Northeastern Brazilian Rift System and their western area, the LycopteraePeipiaosteus assemblage belonging to West African counterparts (Maisey, 2000; Taverne and Chanet, the Jehol Biota in the middle, and the MesoclupeaeParaclupea 2000; Cavin et al., 2012); Aidachar paludalis from the Upper assemblage in the southeastern area (see fig. 8 in Chang and Miao, Cretaceous of Uzbekistan (Mkhitaryan and Averianov, 2011); Mes- 2004), and they were thought to be approximately of the same age, oclupea from the Aptian - lower Albian of Southeast China; Chuh- the Early Cretaceous. The fish assemblage of the Jehol Biota con- siungichthys from the lower Albian (Jingeng Sha, pers. comm. 2013) tained forms endemic to the vast inland area of East Asia during the or even the Upper Cretaceous (Chen, 2012) of Southwest China; Early Cretaceous, e.g., Lycoptera, acipenseriforms and Sinamia, Chuhsiungichthys from the Dobaru Formation, corresponding to the whereas the fish assemblage close to the west coast of the Pacific, in Hauterivian to Barremian Sengoku Formation (Ota, 1981), and the addition to osteoglossomorphs and amiiforms, contained several younger Kumagai Formation of Kyushu, Japan (Yabumoto et al., cosmopolitan forms such as ichthyodectiforms (e.g., Mesoclupea 2006; Sha et al., 2012); and Jinjuichthys from the Hauteriviane from Zhejiang Province southeastern China, Chuhsiungichthys from Barremian or AptianeAlbian of Southeast Korea (Lee et al., 2001). In Yunnan Province, South China, and Kyushu, Japan) and ellim- addition to characters shared with ichthyodectiforms in general, michthyiforms (e.g., Paraclupea from Zhejiang and Fujian provinces, the three Asian freshwater genera share the following distinctive China, Chang and Grande, 1997; Diplomystus from Kyushu, Japan, features that distinguish them from all other ichthyodectiforms: 1) Yabumoto, 1994). Now Jinjuichthys adds one more cosmopolitan body deeper and shorter than in other ichthyodectiforms; 2) head member to this assemblage. As discussed in the Section 5.2, the age length, compared with standard length, longer than that in other of the Shouchang and Guantou formations, containing Mesoclupea, ichthyodectiforms; 3) anal fin with more rays and thus longer than may most probably be from the Aptian to Albian, whereas the age of that in other ichthyodectiforms; 4) number of vertebrae less than in the Yixian Formation, in which Lycoptera, acipenseriforms and most other ichthyodectiforms, abdominal vertebrae are less than Sinamia were discovered, is recently dated ranging from H.-M. Kim et al. / Cretaceous Research 47 (2014) 117e130 129

129.7 0.5 Ma at the bottom of the Formation to 122.1 0.3 Ma for their careful reading of our manuscript, criticism, and constructive the lowermost part of the overlying Jiufotang Formation, i.e., the suggestions. This work is supported by the Society of Natural His- Barremian to early Aptian (Chang et al., 2009). In other words, the tory and Future Environments, Republic of Korea and the National Mesoclupea-bearing strata and, perhaps, the Jinju formation as well Basic Research Program of China (Grant No. 2012CB821900). as the Wakino subgroup are slightly younger than the Yixian Formation. Moreover, the volcanic lava flows and tuff materials from the Yixian Formation are basaltic, whereas those from the Shouchang References and Guantou formations are rhyolitic, indicating distinctly different Alvarado-Ortega, J., 2004. Description and relationships of a new Ichthyodectiform tectonic events and geological backgrounds in the two areas. fish from the Tlayúa Formation (Early Cretaceous: Albian), Puebla, Mexico. Notably both intrusive and volcanic tuff materials from the Creta- Journal of Vertebrate Paleontology 24, 802e813. ceous Gyeongsang Supergroup are mainly granitic and rhyolitic, Alvarado-Ortega, J., Brito, P.M., 2010. A new ichthyodectiform (Actinopterygii, Tel- eostei) from the Lower Cretaceous Marizal Formation, North-east Brazil. which are similar to those from southeastern China. The different Palaeontology 53 (Part 2), 297e306. compositions of the two adjacent fish faunas may be attributed to a Arratia, G., 1984. Some osteological features of Varasichthys ariasi Arratia (Pisces, Tel- combination of factors, such as their different geographical distri- eostei) from the Late Jurassic of Chile. Paleontologische Zeitschrift 58, 149e163. Arratia, G., 2000. Remarkable teleostean fishes from the Late Jurassic of southern butions and different environments as a result of different Germany and their phylogenetic relationships. Mitteilungen aus dem Museum geological backgrounds, and, perhaps, their different ages. für Naturkunde in Berlin. Geowissenschaftliche Reihe 4, 137e179. On the basis of petrographic, paleontological, and geochemical Arratia, G., Scasso, R.A., Kiessling, W., 2004. Late Jurassic fishes from Longing Gap, Antarctic Peninsula. Journal of Vertebrate Paleontology 24, 41e51. studies, Hu et al. (2012a) suggested an Early Cretaceous trans- Bardack, D., 1965. Anatomy and evolution of chirocentrid fishes. University of gression in southeastern China, which extended to 29 N in the Kansas Paleontological Contribution. Vertebrata 10, pp. 1e88. north and approximately to the southeastern side of the Wuyi Bardack, D., Sprinkle, G., 1969. Morphology and relationships of saurocephalid fishes. Fieldiana. Geology 16, 297e340. Mountains, Fujian Province, in the west. And they attributed the Blanco-Piñón, A., Alvarado-Ortega, J., 2007. Review of Vallecillichthys multi- cause of the transgression to the intensive regional subsidence vertebratum (Teleostei: Ichthyodectiformes), a Late Cretaceous (early Turonian) related to the rapid westward subduction of the Paleo-Pacific Plate “Bulldog fish” from northeastern Mexico. Revista Mexicana de Ciencias Geo- e at the time. However, previous studies on fossil fish fauna from this lógicas 24, 450 466. Cavin, L., Forey, P., Giersch, S., 2012. Osteology of Eubiodectes libanicus (Pictet and area (Chang and Chou, 1977; Chang and Miao, 2004; Xu and Chang, Humbert, 1866) and some other ichthyodectiformes (Teleostei): phylogenetic 2009) showed that the fauna included both the forms similar to implications. Journal of Systematic Palaeontology iFirst, 1e63. those from the Jehol Biota, such as osteoglossomorphs (Paraly- Chang, M., 1963. New materials of Mesoclupea from Southeastern China and on the systematic position of the genus. Vertebrata PalAsiatica 7 (2), 105e122 [in coptera and Huashia) and amiiforms (Sinamia and Ikechaoamia), Chinese with English summary]. and the forms with most of their close relatives so far only found in Chang, M., Chou, C., 1977. On Late Mesozoic fossil fishes from Zhejiang Province, marine deposits, such as ichthyodectiforms (Mesoclupea), ellim- China. Memoirs of Institute of Vertebrate Paleontology and Paleoanthropology. Academia Sinica 12, 1e59. Beijing. [in Chinese with English summary]. michthyiforms (Paraclupea), and ginglymodians (Lepidotes). Ich- Chang, M., Chow, C., 1978. On the fossil fishes in Mesozoic and Cenozoic oil-bearing thyodectiforms and ginglymodians were occasionally found strata from East China and their sedimentary environment. Vertebrata PalA- associated with osteoglossomorphs and amiiforms in more inland siatica 16 (4), 229e237 [in Chinese]. 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