All species of the genus Sinamia (Sinamiidae, Amiiformes) are reviewed on the basis of the examination of the holotypes, paratypes, other specimens, and original descriptions of each species. Diagnoses are provided for all species. Phylogenetic analysis supports the monophyly of the family Sinamiidae and demonstrates that the long dorsal fin base in Sinamia and Amia is a matter of convergence. It is considered that the species having a long dorsal fin base lived in still water with vegetation, like Amia calva, while the species having a short dorsal fin base probably lived in the open water.
Introduction
Fishes of the family Sinamiidae have been found from Cretaceous freshwater deposits in East and Southeast Asia. The family consists of three genera, Sinamia, Ikechaoamia and Siamamia. Sinamiids are distinguished from other amiiform fish by having a single parietal, three pairs of extrascapular, length of dermopterotic same as length of parietal, and monospondylous vertebrae (Grande and Bemis, 1998). There are two species of the genus Ikechaoamia, I. orientalis Liu, 1961 and I, meridionalis Zhang and Zhang, 1980. Siamamia is a monotypic genus established on Siamamia naga described from Thailand by Cavin et al. in 2007.
Stensiö (1935) established the genus Sinamia based on Sinamia zdanskyi described on the basis of 18 specimens from Shandong Province, China collected by Tan and Zdansky. Six additional species of the genus Sinamia have been described from China, namely S. huananensis Su, 1973 from Anhui Province; S. chinhuaensis Wei, 1976 from Zhejiang Province; S. luozigouensis Li, 1984 from Jilin Province; S. poyangica Su and Li, 1990 from Jianxi Province; S. liaoningensis Zhang, 2012 from Liaoning Province; and S. lanzhouensis Peng et al., 2015 from Gansu Province, and one species from Japan, S. kukurihime Yabumoto, 2014 from Ishikawa Prefecture (Figure 1). Furthermore, two fossil specimens belonging to the genus but without specific assignment have been found in the southern part of Korea (Yabumoto et al., 2006).
Liu et al. (1963) found many specimens of Sinamia zdanskyi from Kansu, Shensi, Ninghsia and Inner Mongolia Autonomous Region around the Ordos Plateau. Liu and Su (1983) reviewed S. zdanskyi, S. huananensis, S. chinhuaensis, Ikechaoamia orientalis and I. meridionalis and considered the age of those species to be Early Jurassic. However, Zhang (2012) considered that all sinamiids from China are of Cretaceous or Early Cretaceous age. Yabumoto (2014) also determined the age of S. kukurihime as the Early Cretaceous.
In the present study, all species of the genus Sinamia are reviewed and cladistic analysis of the family Sinamiidae is provided.
Paleontological description
Order Amiiiformes Hay, 1929
(sensu Grand and Bemis, 1998)
Family Sinamiidae Berg, 1940
Genus Sinamia Stensiö, 1935
Type species.—Sinamia zdanskyi Stensiö, 1935.
Diagnosis.—The genus Sinamia differs from other genera of the family Sinamiidae in having the following combination of characters: postinfraorbitals short, lateral edge of posttemporal about equal to or slightly longer than length of its anterior edge, ganoid scales covered entire body, and ganoid scales with strong keel or ridge on internal surface.
Figure 1.
Localities of the genus Sinamia based on Liu and Su (1983), Zhang (2012), Yabumoto (2014) and Peng et al. (2015).
Sinamia zdanskyi Stensiö, 1935
Figures 2, 3
Holotype.—PIU (Palaeontological Institute of Uppsala University, Sweden) 1, skull with pectoral fin and vertebrae.
Paratypes.—Seventeen specimens, PIU 2–18 (see Stensiö, 1935).
Additional materials.—IVPP (Institute of Vertebrate Paleontology and Paleoanthropology, Beijing) 1114.1 (393 mm), 1106 (est. 260 mm SL).
Horizon and locality.—Holotype and paratypes from Meng-Yin series, in Meng-Yin-Hsien, Shandong Province, China. Additional material IVPP 1114.1 from the Meng-Yin Group, Shandong Province, China, IVPP 1106 from the Paoan Group, Baiyushan Mountain, Wagi City, Shaanxi Province, China. Other specimens have been found from Kansu, Shensi, Ninghsia and Inner Mongolia Autonomous Region, China (Figure 1).
Emended diagnosis.—This species is distinguished from other species in the genus by the following combination of characters: dorsal fin rays 27, long caudal fin rays 11–13, bones of the head covered by an enamel layer with ridged fine rugose ornamentation, the posterior margin of the parietal shorter than the anterior portion, posterior margins of scales serrated, longitudinal scales 46–48, scales between ventral and dorsal margin just behind shoulder girdle 25, between pelvic fin and dorsal fin 22–23, at caudal peduncle 14, dorsal margin of hyomandibular straight (Figure 3), two subinfraorbitals.
Remarks.—This is a large fish and the type species of the genus Sinamia described by Stensiö in 1935 based on the specimens collected by Tan and Zdansky from the Meng-Yin series, in Meng-Yin-Hsien, Shandong Province, China (Stensiö, 1935; Liu et al., 1963). Li et al. (1963) found many other specimens of this species from Kansu, Shensi, Ninghsia and Inner Mongolia Autonomous Region around the Ordos Plateau and provided a short description of characters that were not in the original description by Stensiö (1935). Grande and Bemis (1998) examined some other specimens deposited in the Institute of Vertebrate Paleontology and Paleoanthropology, IVPP 1114.1 and 1106 belonging to this species and demonstrated that autapomorphies of this species are crenulated posterior edge of extrascapular bone, shape of hyomandibula and 27 dorsal fin rays.
Figure 2.
Sinamia zdanskyi Stensiö, 1935. A, restoration of the body; B, restoration of the head in dorsal view; C, restoration of the head in lateral view; D, restoration of the head in ventral view; E, hyomandibular (A from Liu et al., 1963; B, C, D and E from Stensiö, 1935).
Sinamia huananensis Su, 1973
Figures 3–5
Holotype.—IVPP V 4087 with the counterpart, TL 127 mm, SL 103 mm, specimen without pelvic and anal fins.
Horizon and locality.—The Lower Cretaceous Yangtang Formation of Anhui Province, China (Figure 1).
Emended diagnosis.—This species is distinguished from other species in the genus by the following combination of characters: dorsal fin rays 22, long caudal fin rays about 12, bones of the head smooth without ornamentation, posterior margin of scales smooth, longitudinal scales 41, scales between pelvic insertion and dorsal fin base less than 25, the dorsal margin of the hyomandibular almost straight (Figure 3).
Remarks.—This species is a small fish described by Su on the basis of a single individual with part and counterpart from the Lower Cretaceous Yangtang Formation of Anhui Province, China in 1973. The original description is in Chinese without an English abstract. The fossil was dated as Late Jurassic in the original description, however Zhang (2012) thought its age is Early Cretaceous. Su (1973) described this species accompanied by a schematic drawing of the head, and by photos of the entire body and part of the head of the holotype. In the present study, I provide photos of the entire body of the part and counterpart of the holotype, scales, head, hyomandibula and caudal region, as well as drawings of the entire body and the head of the part of the holotype (Figures 4, 5). Autapomorphies of this species are the 22 dorsal fin rays, and the smooth surface of the bones of the head.
Figure 3.
Comparison of hyomandibulas of the genus Sinamia. A, Sinamia zdanskyi Stensiö, 1935; B, S. huananensis Su, 1973; C, S. chinhuaensis Wei, 1976; D, S. poyangica Su and Li, 1990; E, S. luozigouensis Li, 1984; F, S. kukurihime Yabumoto, 2014; G, S. lanzhoensis Peng, Murray, Brinkman, Zhang and You, 2015. Abbreviations: Dpt = dermopterotic; H = hyomandibula; Op =opercle; Pop = preopercle; Q = quadrate. Anterior facing left. Scale bars indicate 5 mm. All from Yabumoto (2014) except A, drawing based on plate X of Stensiö (1935). B and F are reversed drawings of the holotypes.
Sinamia chinhuaensis Wei, 1976
Figures 3, 6, 7
Holotype.— Zhejiang Museum of Natural History M. 20-1 with the counterpart. TL 107 mm.
Horizon and locality.—The Lower Cretaceous Guantou Formation of Jinhua, Zhejiang Province, China (Figure 1).
Emended diagnosis.—This species is distinguished from other species in the genus by the following combination of characters: dorsal fin rays 33, long caudal fin rays 13, bones of the head covered by enamel layer with strong rugose and ridged ornamentation, dorsal and ventral margin of the scales form ridges, posterior margin of scales serrated and forming four to six needlelike spines, longitudinal scales 54, scales between ventral and dorsal margins 25, the surface of the hyomandibula strongly ornamented with rugose ridges.
Remarks.—Sinamia chinhuaensis is a small fish described on the basis of a single individual associated with a semionotid, Sinolepidotus chekiangensis, from the same locality, Jinhua, Zhejiang Province, China by Wei in 1976. The original description is in Chinese with an English abstract. Autapomorphies of this species are the long dorsal fin base with the largest number of fin rays (33) among the genus, the strong ornamentation of bones of the head, and needlelike spines on the posterior margins of the scales. The bone between the dermopterotic and preopercle is identified as a hyomandibular because of the position of the bone and the directions of ridges of the dorsal and ventral arms (Figures 3, 7). This bone is located well behind the orbit and its dorsal margin contacts with the dermopterotic while its posterior margin contacts with the preopercle. The ornamentation is radiate fine ridges toward the dorsal margin on the dorsal arm, three stout ridges toward the ventral margin on the ventral arm. The middle part is almost smooth with few radiate weak ridges toward the upper part of the posterior margin. These ridge directions are seen in the hyomandibular of S. kukurihime (see Yabumoto, 2014, fig. 2).
On the label of the holotype, jinhuaensis is mentioned as the species name, M1351 as the specimen number and M.20-1 as the collecting number. However, the species name was changed to chinhuaensis and the specimen number was changed to M.20-1 in the original description.
Figure 4.
Sinamia huananensis Su, 1973. A, holotype, IVPP V 4087; B, counterpart of A; C, head of A; D, hyomandibular and preopercle of A; E, scales of the abdominal part of B; F, caudal fin of A.
Figure 5.
Sinamia huananensis Su, 1973. A, drawing of Figure 4A; B, drawing of Figure 4C; C, restoration based on A and B. Cl = cleithrum; Dpt = dermosphenotic; Es = extrascapular; Fr = frontal; H = hyomandibular; Op = opercle; Pa = parietal; Pop = preopercle; Pt = posttemporal.
Sinamia luozigouensis Li, 1984
Figures 8, 9
Holotype.—IVPP V 6771a, b, TL 425 mm, SL 365 mm, part and counterpart, incomplete specimens.
Paratype.—IVPP V 2766-2a, b, part and counterpart, incomplete specimens.
Horizon and locality.—The Cretaceous Luozigou Formation of Wang Qung, Jilin Province, China (Figure 1).
Emended diagnosis.—This species is distinguished from other species in the genus by the following combination of characters: dorsal fin rays 28, long caudal fin rays about 13–14, posterior margin of scales smooth, longitudinal scales 54–56, scales between anal fin origin and dorsal fin base more than 25, scales between ventral and dorsal margins at the caudal peduncle 24.
Remarks.—This is a large fish described by Li on the basis of two individuals with parts and counterparts from the Cretaceous Luozigou Formation of Wang Qung, Jilin Province, China in 1984. The original description is in Chinese with English abstract. Bones of the head are not well preserved, which makes difficult the recognition of each ossification. However the scales of the trunk are well preserved. Zhang (2012) thought that the validity of this species is not reliable, because “the skull of the specimen is severely damaged, providing nothing valuable information and the postcranial skeleton is very similar to that of Sinamia zdanskyi.” However, the squamation of this species is very different from that of S. zdanskyi (Figures 2, 8, 9). The number of scales at the caudal peduncle is 24 in this species vs. 14 in S. zdanskyi and the posterior margins of scales are smooth in this species vs. serrated in S. zdanskyi.
Sinamia poyangica Su and Li, 1990
Figures 3, 10
Holotype.—East China College of Geology P001, almost complete specimen. A replica of the holotype is deposited in IVPP. TL 271 mm.
Other specimens.—East China College of Geology P002-021.
Horizon and locality.—The Lower Cretaceous Shixi Formation of Xinjian Basin, Northeast Jiangxi Province, China (Figure 1).
Emended diagnosis.—This species is distinguished from other species in the genus by the following combination of characters: dorsal fin rays 25, long caudal fin rays 11, bones of the head covered by an enamel layer with fine rugose ornamentation, posterior margin of scales slightly serrated, posterior margins of the opercular bones and the cleithrum serrated, two suborbitals, longitudinal scales 46–48, scales between pelvic insertion and dorsal fin base 23, 21, 19 posteriorly, the dorsal margin of the hyomandibular slightly convex (Figure 3).
Remarks.—The holotype of this species belongs to the East China College of Geology, the second author of the original description, Li Haochang, keeps the specimen. A replica of the holotype is deposited in the Institute of Vertebrate Paleontology and Paleoanthropology. The original description is in Chinese with an English abstract. The holotype is covered by a thick transparent layer, which is probably wood glue. This species was described on the basis of 21 specimens from the Lower Cretaceous Shixi Formation of Xinjian Basin, Jiangxi Province, China. The holotype and two specimens deposited in IVPP were examined for this study, but other specimens deposited in East China College of Geology were not examined. Autapomorphy of this species is serrated posterior margins of opercular bones and cleithrum.
Figure 6.
Sinamia chinhuaensis Wei, 1976. A, holotype, Zhejiang Museum of Natural History M. 20-1; B, counterpart of A; C, head of A; D, hyomandibular of A; E, scales of the abdominal part of A; F, caudal peduncle and fin of A.
Figure 7.
Sinamia chinhuaenis Wei, 1976. A, drawing of Figure 6A; B, drawing of Figure 6C; C, restoration based on A and B. Cl = cleithrum; D = dentary; Dpt = dermosphenotic; Es = extrascapular; Fr = frontal; H = hyomandibular; Iop = interopercle; Mx = maxilla; Op = opercle; Pa = parietal; Pmx = premaxilla; Pop = preopercle; Pt = posttemporal; Smx = supramaxilla; Sop = subopercle.
Sinamia liaoningensis Zhang, 2012
Figures 3, 11
Holotype.—IVPP V 1408, TL 425 mm, SL 365 mm, well preserved, almost complete specimen.
Other specimens.—IVPP V 12700.1-2, V 12700.4B, V 17973A-B, V 17974, V 18332.1-2.
Horizon and locality.—IVPP V 14608, V 12700.1-2, V 18332.1-2 from the Jiufotang Formation, Xierhuqiao, Yixian County, Liaoning Province (type locality); V 17973A-B from the Jiufotang Formation, Dijiagou, Yixian county, Liaoning Province; V 12700.4B from the Yixian Formation, Toudaohe, Yixian County, Liaoning Province; V 17974 from the Yixian Formation, Sihetun, Beipiao City, Liaoning Province, China (Zhang, 2012) (Figure 1).
Emended diagnosis.—This species is distinguished from other species in the genus by the following combination of characters: dorsal fin rays 18, long caudal fin rays 14, bones of the head relatively smooth, posterior margins of scales smooth, longitudinal scales 51, scales between the anal fin origin and the dorsal fin base 32, anterior margin of hyomandibular angularly concave (Figure 3), three subinfraorbitals, dorsal end of subopercle strongly curved anteriorly, anterior half of caudal fin rays with thin fibrous actinotrichia.
Remarks.—Sinamia liaoningensis was described by Zhang in 2012 on the basis of an almost complete specimen and some other specimens from two formations, the Jiufotang and Yixian formations in Yixian County, Liaoning Province, China. The original description is in English with a Chinese abstract. This is the first species of the genus Sinamia described from the Jehol Group. Autapomorphies of this species are the short dorsal fin base with 18 fin rays, which is one of the smallest numbers among the genus, and the strongly curved dorsal end of the preopercle. It is interesting that this species has thin fibrous actinotrichia in the caudal fin rays, which are observed in the early developmental stages of the Recent amiiform species Amia calva (see Zhang, 2012).
Figure 8.
Sinamia luozigouenis Li, 1984. A, holotype, IVPP V 6766-1a; B, head of A; C, caudal fin of IVPP V 6766-2a; D, scales above and before the anal fin of IVPP V 6766-2a.
Sinamia kukurihime Yabumoto, 2014
Figure 3
Holotype.—SBEI (Shiramine Board of Education, Hakusan, Ishikawa) 817, a right hyomandibula.
Paratypes.—SBEI 823, a right frontal; SBEI 1401, a left frontal; SBEI 1841, a left frontal; SBEI 1849, a left dermosphenotic; SBEI 193, a left dermosphenotic; SBEI 1257, a left infraorbital; SBEI 1207, a left infraorbital; SBEI 2028, a left infraorbital; SBEI 1860, a right maxilla; SBEI 2017, a left maxilla; SBEI 295, a left maxilla; SBEI 14, a left dentary; SBEI 2332, a right dentary; SBEI 1951, a right dentary; SBEI 2453, a right dentary; SBEI 1952, left coronoids; SBEI 1959, a right palatine; SBEI 1208, a gular; SBEI 300, a gular; SBEI 312, a right preopercle; SBEI 2030, a left preopercle; SBEI 2451, a right subopercle; SBEI 2272, an abdominal centrum; SBEI 1953, an abdominal centrum; SBEI 2450, a caudal centrum; SBEI 299, an abdominal centrum; SBEI 1954, a caudal centrum; SBEI 315, a right supracleithrum; SBEI 317, a right supracleithrum; SBEI 2449, a right supracleithrum; SBEI 301, a right supracleithrum; SBEI 1192, a left supracleithrum; SBEI 316, a right cleithrum; SBEI 1259, a right cleithrum; SBEI 1842, a right cleithrum; SBEI 1306, ganoin scales; SBEI 2452, a ganoin scale; SBEI 297, ganoin scales; SBEI 2341, a ganoin scale; SBEI 2342, a ganoin scale; SBEI 2346, a ganoin scale; SBEI 2327, a ganoin scale; SBEI 2330, a ganoin scale.
Horizon and locality.—Kaseki-Kabe, Kuwajima, Hakusan City, Ishikawa Prefecture, central Japan (Figure 1). Freshwater sediments, the Kuwajima Formation of the Itoshiro Subgroup, Tetori Group, Berriasian—Hauterivian, Lower Cretaceous.
Diagnosis.—The species is distinguished from other species in the genus by the following combination of characters: the lateral surface of the hyomandibula smooth without ridges (Figure 3), the dorsal arm longer and larger than the ventral arm, the smoothly concave anterior margin, the dorsal margin of the dorsal arm strongly convex, small posterior process for the articulation with the opercle, the posterior margin of the dorsal arm forming an acute angle with the dorsal margin of the posterior process for the articulation with the opercle; the dorsal surface of the frontal smooth and covered with a layer of enamel, a series of pores opening from the supraorbital sensory canal relatively large, the concavity for the orbit shallow; the suture between the right and left frontals slightly undulate; the dorsal surface of the dermopterotic smooth; the anterior articular process of the maxilla for the premaxilla long and stout; the gular plate pyriform in dorsal view; the preopercle narrow crescentor bow-shaped, the ventral three-fourths of the preopercle almost straight and slightly wider than the dorsal part; the supracleithrum shoehorn-shaped; the posterior margin of scales smooth (Yabumoto, 2014).
Remarks.—This is a large fish described by Yabumoto on the basis of 52 specimens from the Lower Cretaceous Kuwajima Formation of the Itoshiro Subgroup, the Tetori Group at Kuwajima, Hakusan City, Ishikawa Prefecture in central Japan in 2014. The holotype is an isolated hyomandibula (Figure 3) and the paratypes are isolated skull bones, centra and ganoin scales. Although there were two types of supracleithra and gular plates, these were tentatively assigned to the same species, Sinamia kukurihime. Associated specimens from the same locality will be necessary to resolve the problem that the two types are different species or infraspecific variation (Yabumoto, 2014). This is the largest species (about 70 cm in estimated total length based on the large maxilla) among the genus, and a unique species of the genus outside China.
Figure 10.
Sinamia poyangica Su and Li, 1990. A, holotype. East China College of Geology P001; B, head of A; C, hyomandibular and preopercle of A; D, scales between head and origin of dorsal fin of unnumbered specimen of IVPP; E, caudal fin of A.
Figure 12.
Restoration of Sinamia lanzhoensis Peng, Murray, Brinkman, Zhang and You, 2015 based on figs. 5 to 8 of Peng et al. (2015).
Sinamia lanzhoensis Peng, Murray, Brinkman, Zhang and You, 2015
Figures 3, 12
Holotype.—GSDM (Gansu Dinosaur Museum) 00022, an almost complete fish preserved in a block with 14 other partial fishes, about 130 to 210 mm SL.
Horizon and locality.—The Lower Cretaceous Hekou Group in Lanzhou Basin, near the town of Zhongpu, about 30 km south of Lanzhou, Gansu Province, China (Figure 1).
Diagnosis.—Differs from Sinamia zdanskyi, S huananensis, S. luozigouensis, and S. chinhuaensis by having fewer dorsal fin rays (15 to 18, compared to 26, 20, 20, and 33, respectively). Further differs from S. huananensis by lacking prominent canals associated with the lateral line scales, and from S. luozigouensis and S. chinhuaensis by having fewer lateral line scales (43–46 compared with 54–56 in S. luozigouensis and 54 in S. chinhuaensis). Differs from S. poyangica by lacking projections on the posterior surface of most scales and having a straight posterior edge of the dermopterotic compared with a concave edge with elongate posterolateral corner in S. poyangica. Differs from S. liaoningensis by having fewer scales in a transverse row (18 compared with 32) and fewer branched caudal fin rays (12 compared with 14) (Peng et al.2015).
Remarks.—Peng et al.(2015) did not compare their specimens to Sinamia kukurihime Yabumoto, 2014. The number of the dorsal fin rays of S. lanzhoensis is 15 to 18, probably 17 in the holotype (there is no mention of the number of dorsal fin rays of the holotype in the original description). This is one of the smallest numbers of dorsal fin rays among the genus. The number of dorsal fin rays of this species is almost the same as S. liaoningensis. However, this species differs from S. liaoningensis in having different proportions of the hyomandibular, which is similar to that of S. kukurihime from the Lower Cretaceous Kuwajima Formation in Japan in having a long groove for the hyomandibular trunk along its anterior margin, dorsal arm larger than ventral arm, and a smooth surface (Figure 3). The preopercle, frontal, and scales are also similar to those of S. kukurihime (figures 6 and 8 of Peng et al., 2015 vs. figures 3, 5 and 7 of Yabumoto, 2014).
Discussion
In the present study, all species of the genus Sinamia are reviewed and compared on the basis of the examination of the holotypes, paratypes and other specimens with reference to the original descriptions and previous studies of the genus. Restorations of all species were attempted except for S. kukurihime, because an articulated specimen of S. kukurihime has not been found. Among species of the genus Sinamia, differences are recognized in ornamentation of skull bones, hyomandibulas and posterior margins of scales; numbers of scales and dorsal fin rays; and the position of the anal fin.
In Sinamia poyangica, S. zdanskyi, S. luozigouensis and S. chinhuaensis, the anal fin origin is located anteriorly under the end of the dorsal fin base and the number of dorsal fin rays is more than 25. In S. huananensis and S. liaoningensis, the anal fin origin is located posteriorly or just under the end of the dorsal fin base, and the number of dorsal fin rays is less than 23. These two groups show a difference in the ratio of the head to the standard length. The former group has a smaller head than the latter (Figure 13). The end of the dorsal fin base is located at almost the same body position in the former group while its position in the latter group is comparatively more anterior. Sinamia lanzhouensis has a small number of dorsal fin rays (15-18); the anal fin origin is located anteriorly under the end of the dorsal fin base and the position of the end of the dorsal fin base is the same as in the former group (Figure 13).
Peng et al. (2015) provided the first phylogenetic analysis of the family Sinamiidae. However, they excluded Sinamia chinhuaensis in their second analysis, because most of the data were missing for this species in their study. In the present study, the holotype of S. chinhuaensis is examined and it is included in the analysis. The genus Ikechaoamia consists of two species, I. orientalis Liu, 1961 and I. meridionalis Zhang and Zhang, 1980. In the present study, I. meridionalis is only included in the analysis, because both species are on the whole in accordance with each other except for the number of vertebrae and dorsal fin rays (Zhang and Zhang, 1980) and I. meridionalis has been well illustrated (Grande and Bemis, 1998). Both species are coded with the same character state (0 in Character 15).
In the present study, some coding of character states and polarity of the characters (14 and 15) of the data matrix of Peng et al. (2015) are modified as Appendix 1 on the basis of the examination of holotypes and paratypes and the original descriptions of each species. Furthermore, the character 24 about the position of the anal fin is added as shown in Appendix 2.
PAUP (v. 4.0 Beta, Swofford 2003) and MacClade (v. 4.0.5 Os X; Maddison and Maddison, 2002) analyses were performed using the modified data matrix (Appendix 3) mentioned above. PAUP analysis (using the branch-and-bound search) resulted in 19 equally parsimonious trees (length 44, CI= 0.636, RI= 0.628, RC=0.400). Character states were optimized to the tree using the ACCTRAN option. The strict consensus tree of the 19 trees resulted in all species of the genus Sinamia and Siamamia naga forming a polytomy and the sister group of Ikechaoamia meridionalis (Figure 14A).
The second analysis is performed using the modified data matrix excluding Sinamia kukurihime, because this species has many question marks (62%). PAUP analysis (using the branch-and-bound search) resulted in one parsimonious tree (length 43, CI=0.651, RI= 0.634, RC=0.413) (Figure 14B). The topology of both results is very different from the one produced by Peng et al. (2015), and more reliable, because Ikechaoamia meridionalis forms a sister taxon with all other sinamiid fishes, whereas in contrast, I. meridionalis + I. orientalis forms a clade with S. liaoningensis within other species of Sinamia and Siamamia naga in Peng et al. (2015). The result of the present study supports the monophyly of the family Sinamiidae based on five synapomorphies (characters 4, single parietal bone; 7, dermopterotic same length as parietal; 13, scapulocoracoid strongly ossified; 17, caudal fin rays 14 or fewer; and 21, scales with strong keel or ridge on internal surface) and I. meridionalis forms a sister taxon of all species of Sinamia and Siamamia naga, which clade is supported by the synapomorphy (character 18: ganoid scales covered entire body) (Figure 14). The autapomorphy for I. meridionalis is that the ganoid scales are present only along the centra.
In the result of the second analysis, all species of the genus Sinamia and Siamamia naga, are divided into two groups, S. liaoningensis + S. huananensis and the other species of Sinamia including Siamamia naga (Figure 14B). The former clade is supported by two synapomorphies (characters 14, three or more lateral fossae on each side of most centra; 24, anal fin origin posterior or just under the end of dorsal fin base) and the latter one is supported by the homoplastic character (22(1), serrations on the posterior margin of scales present) and the plesiomorphic character state (24(0), anal fin origin anterior under the end of dorsal fin). In the later clade, S. lanzhouensis has the shortest dorsal fin base with the smallest number of dorsal fin rays, 15 to18 (Figure 13). The short dorsal fin base with small number of dorsal fin rays is plesiomorphic, because the genus Ickechaoamia has a relatively short dorsal fin base and small number of dorsal fin rays, 20–23 (25 in I. meridionalis by Liu and Su, 1983) (Liu and Su, 1983, fig. 8; Zhang and Zhang, 1980), furthermore, within the family Amiidae, the closest family to the Sinamiidae, both Calamopleurus and Amiopsis have a short dorsal fin base and a small number of dorsal fin rays. Therefore, the polarities of the dorsal fin base and the number of dorsal fin rays are from short and small to long and large among the genus Sinamia. Consequently, Sinamia lanzhouensis is the most primitive and S. chinhuaensis is the most derived species in this clade (Figures 13, 14). In this clade, Siamamia naga and Sinamia luozigouensis form a clade, which is supported by two characters 19 (1) and 22 (0). Siamamia naga might be a member of the genus Sinamia, however, the character 19 (the number of scales in a transverse row at the level of the dorsal fin) is unknown in S. naga and the state of the character 22 (serrations on the posterior margin of scales absent) is plesiomorphic.
Figure 14.
A, Strict consensus cladogram resulting from 19 equally parsimonious cladograms under the branch-and-bound search option using the modified data matrix (Appendix 3); B, most parsimonious tree by the second analysis using the modified data matrix excluding Sinamia kukurihime.
The single Recent amiiform fish, Amia calva, undulates its long dorsal fin for swimming forward and backward or stopping and lives in still water with vegetation. It is thought that this swimming form is advantageous for living in still water with much vegetation and so the long dorsal fin base in some species of Sinamia and in Amia could be a matter of convergent adaptation for living under those conditions. On the other hand, Sinamia liaoningensis, S. huananensis and S. lanzhouensis probably could not undulate their dorsal fins for swimming and they probably lived in the open water. However, there is no decisive geological or sedimentological information about the paleoenvironments in which these species lived. Reproductive organs of many charophytes have been collected from the Jehol Group from which S. liaoningensis was found, but there is no evidence as to whether S. liaoningensis lived either in vegetation or in open water. Peng et al. (2015) considered that S. lanzouensis used to live in schools in an area of fluvial environment made habitable by seasonal flooding, because multiple fish specimens are densely preserved in the blocks and the body sizes of these fish specimens are almost the same. Schools of fishes usually live in open water.
Acknowledgments
The author wishes to express his sincere gratitude to Cai Chun Mo (Zhejiang Museum of Natural History, Hangzhou) for letting him examine the type specimens in the museum and Zhang Meemann and Jin Fan (Institute of Vertebrate Paleontology and Paleoanthropology, Beijing) for their help in examining the type specimens and others in their institute. The author is grateful to Lance Grande (Field Museum of Natural History, Chicago) for his critical reading of the manuscript and his valuable comments. The author would like to thank Lionel Cavin for reviewing this paper and providing valuable comments as a referee. This study was supported by JSPS KAKENHI Grant Number JP26400506.
References
Appendices
Appendix 1. Explanations of the states that are different from Peng et al. (2015).
Character 1.—Sinamia zdanskyi (0 in Peng et al., 2015 → 2 in the present study): there is the anterior frontal excavation in S. zdanskyi (Stensiö, 1935, text-figure 18, pl. 1). S. chinhuaensis (? → 2): there is the anterior frontal excavation in S. chinhuaensis (Figures 6C, 7B). S. huananensis (1 → ?): the anterior ends of the frontals are broken in the holotype of S. huananensis (Figures 4C, 5B). Character 2.— Sinamia chinhuaensis (? → 0): the frontal ornamentation is strong in S. chinhuaensis (Figures 6C, 7B). S. poyangica (1 → 0): the frontal ornamentation is strong in S. poyangica (Figure 13B). Siamamia naga (1 → 0): it is strong in S. naga, but the surface of the bone is worn down (see Cavin et al., 2007, figure 3). Character 3.—Ickechaoamia meridionalis (? → 1): the posterior margin is triangular in I. meridionalis (see Grande and Bemis, 1998, figure 397). Sinamia chinhuaensis (? → 1): the posterior margin is triangular in S. chinhuaensis (Figures 6C, 7B). Character 4.—The states are the same as Peng et al. (2015). Character 5.—Ickechaoamia meridionalis (1 → 0): the parietal length is long, width/length = 0.71 in I. meridionalis (from Grande and Bemis, 1998, figure 397). Sinamia chinhuaensis (? →0): 0.57 in S. chinhuaensis (Figures 6C, 7B). S. liaoningensis (1 → 0): 0.73 in S. liaoningensis. S. luozigouensis (0 → ?): no bones of the head are preserved in the holotype and paratype of S. luozigouensis (Figure 8A). Character 6.—Sinamia chinhuaensis (? → 0): the ornamentation of parietal is strong in S. chinhuaensis (Figures 6C, 7B). Siamamia naga (? → 0): the surface of the bone is worn down in Siamamia naga (Cavin 2007, figure 3). S. huananensis (? → 1): it is weak or absent in S. huananensis (Figures 4C, 5B). Ickechaoamia meridionalis (? → 1): it is weak in I. meridionalis (see Grande and Bemis, 1998, figure 397). Character 7.—Sinamia chinhuaensis (? → 1): the length of the dermopterotic is almost the same as that of the parietal in S. chinhuaensis (Figures 6C, 7B). Character 8.—Sinamia chinhuaensis (? → 1): the dermopterptic posterior process is present in S. chinhuaensis (Figures 6C, 7B). S. huananensis (0 → 1): it is present in S. huananensis (Figures 4C, 5B). Ickechaoamia meridionalis (1 → 0): it is absent in I. meridionalis (from Grande and Bemis, 1998, figure 397). Siamamia naga (0 → ?): it is not preserved in Siamamia naga (Cavin, et al., 2007, figures 2, 6). Character 9.—Sinamia chinhuaensis (? → 1): the extrascapular bones are three pairs in S. chinhuaensis (Figures 6C, 7B). Character 10.—The states are the same as Peng et al. (2015). Character 11.—Sinamia chinhuaensis (? → 0): the strong lines are present on the opercle in S. chinhuaensis (Figures 6C, 7B). S. huananensis (? → 1): there is no ornamentation on the bone in S. huananensis (Figures 4C, 5B). S. luozigouensis (1 → 1?): any bones of the head are not preserved in the holotype and paratype of S. luozigouensis (Figure 8B). Character 12.—Sinamia chinhuaensis (? → 0): the opercle width is narrow in S. chinhuaensis (Figures. 6C, 7B) width/length = 1.04. Character 13.—Sinamia liaoningensis (0 → ?): the scapulocoracoid is not visible in the holotype and additional materials of S. liaoningensis (see Zhang, 2012, p. 330). S. luozigouensis (0 → ?): it is not visible in the holotype and paratypes of S. luozigouensis. S. poyangica (1 → ?): it is not visible in the holotype of S. poyangica. There is no description about the scapulocoracoid in the original descriptions of these species. Ickechaoamia meridionalis (0 → 1): the scapulocoracoid is ossified in I. meridionalis (see Grande and Bemis, 1998, figure 397). Character 14.—The polarity and character state of lateral fossae of centra follow Grand and Bemis (1998) in the present study: present, with two pits on each side of most centra (0); present, with three or more on each side of most centra (1); absent, centra smoothsided (2). The lateral side of centra is visible in the holotype or paratype in Sinamia liaoningensis, S. zdanskyi, S. lanzhouensis and Ickechaoamia meridionalis. The number of fossae is 3 in S. liaoningensis, 2 in S. zdanskyi, S. lanzhouensis and I. meridionalis. The lateral side of centra is not visible in specimens of other species. The number of fossae is 2 or 3 in Siamamia naga. Character 15.—The polarity and character state of dorsal fin are followed Grande and Bemis (1998) with modification of number of fin rays: less than 25 (0); 25 to 34 (1); 36 to 47 (2); 48 to 53 (3). Character 16.—Sinamia huananensis (? → 1): the number of anal fin rays is 6 in S. huananensis (see Su, 1973). S. poyangica (? → 1): it is 6 in S. poyangica (Su and Li, 1990). S. zdanskyi (1 → 0): it is 7 or more in S. zdanskyi (Stensiö, 1935, pl. XVI). Character 17.—Sinamia poyangica (? → 1): Sinamia poyangica has 11 caudal fin rays (Su and Li, 1990). Character 18.—The character state of scales are modified as follows: absence of ganoid scale (0); present only along the centra (1); present, covered entire body (2). Character 19.—The states are the same as Peng et al. (2015). Character 20.—Sinamia liaoningensis (1 → 0): the number of scales in lateral row is 51 in S. liaoningensis. S. poyangica (? → 1): it is 46–48 in S. poyangica. Ickechaoamia meridionalis (1 → ?): it is unknown in I. meridionalis. Character 21.—Sinamia chinhuaensis (0 → 1): there is a strong keel or ridge on internal surface of scale in S. chinhuaensis. S. luozigouensis (0 → ?) and S. poyangica (0 → ?): the internal surfaces of scales are not visible in both species. Character 22.—Sinamia chinhuaensis (? → 1): the serration of the posterior margin of at least some scales is present in S. chinhuaensis. S. liaoningensis (1 → 0), S. luozigouensis (1 → 0) and Ickechaoamia meridionalis (? → 0): is absent in these species. Character 23.—Total length and body depth are measured on the restoration of each species. Sinamia liaoningensis (2 → 1): it is 0.18 in S. liaoningensis. S. poyangica (0 → 1): 0.17 in S. poyangica.
Appendix 2. List of characters and character states modified from those of Peng et al. (2015).
Character 1.—Frontal anterior excavation: absent (0); slight excavation present (1); deep excavation present (2). Character 2.—Frontal ornamentation: strong (0); weak or absent (1). Character 3.—Frontal posterior margin: straight (0); triangular, the lateral edge angling medially more posteriorly (1). Character 4.—Parietal bone: paired (0); single (1). Character 5.—Parietal length: long, width/length = 0.90 or less (0); short, width/length well exceeding 0.90 (1). Character 6.—Parietal ornamentation: strong (0); weak or absent (1). Character 7.—Dermopterotic size compared with parietal: dermopterotic significantly longer than parietal (0); the two bones about the same length (1) . Character 8.—Dermopterotic posterior process: absent (0); present (1). Character 9.—Extrascapular bones: one pair (0); three pairs (1); four pairs (2). Character 10.—Extrascapular bones, posterior edge: smooth (0); ornamented with crenulations (1). Character 11.—Opercle ornamentation: strong lines (0); no ornament (1). Character 12.—Opercle width: narrow, width/height = 0.56–1.06 (0); wide, width/height = 1.07–1.39 (1). Character 13.—Scapulocoracoid ossification: not substantial in adult (0); strongly ossified (1). Character 14.—Centra, number of lateral fossae: present, with two pits on each side of most centra (0); present, with three or more on each side of most centra (1); absent, centra smoothsided (2). Character 15.—Dorsal fin ray number: less than 25 (0); 25 to 34(1); 36 to 47 (2); 48 to 53 (3). Character 16.—Anal fin ray number: seven or more (0); six or fewer (1). Character 17.—Caudal fin ray number: 15 or more (0); 14 or fewer (1). Character 18.—Ganoid scales: absence (0); present only along the centra (1); present, covered entire body (2). Character 19.—Scales in a transverse row at the level of the dorsal fin: 25 or less (0); 26 or more (1). Character 20.—Scales in lateral row: 52 or more (0); 50 or fewer (1). Character 21.—Scales with strong keel or ridge on internal surface: absent (0); present (1). Character 22.—Scales with serrations on the posterior margin of at least some: absent (0); present (1). Character 23.—Body shape: long and narrow, total length into body depth less than 0.153 (0); moderately deep bodied with total length into body depth between 0.162 and 0.193 (1); deep bodied, with total length into body depth more than 0.200 (2). Character 24.—Anal fin origin: anterior under the end of dorsal fin base (0); posterior or just under the end of dorsal fin base (1).
