皖北地区寒武系芙蓉统炒米店组中上部的索克虫类三叶虫_雷倩萍.pdf

收稿日期:2021-12-11;改回日期:2022-06-17;录用日期:2022-08-22*国家自然科学基金(41802004)、中国地质调查局项目(DD20190009)和现代古生物学和地层学国家重点实验室项目(20191101)联合支持。*通讯作者:雷倩萍,副研究馆员,e-mail: 古生物学报,61(4):568589(2022年12月)Acta Palaeontologica Sinica,61(4):568589(December 2022)研究论文 DOI:10.19800/ki.aps.2021071 皖北地区寒武系芙蓉统炒米店组中上部的 索克虫类三叶虫*雷倩萍1*彭善池2,3 1 常州博物馆学术研究部,江苏常州 213022;2 中国科学院南京地质古生物研究所,南京 210008;3 现代古生物学和地层学国家重点实验室,南京 210008 提要 在安徽省萧县凤凰山剖面炒米店组中上部(江山阶上部到第十阶)岩层中采得丰富的索克虫科三叶虫标本。共计4属6种(含2新种),包括Eosaukia bella(Walcott,1906)、E.anhuiensis sp.nov.、Lophosaukia orientalis(Kobayashi,1933)、Prosaukia campe(Walcott,1905)和P.xiaoxianensis sp.nov.以及Lichengia onigawara Kobayashi,1942。在对属征进行修订与讨论的基础上,通过对比这些属的模式种及其他种,对4个旧种进行了再研究和种征厘定,最后对这6个种的谱系关系开展了简要讨论。关键词 索克虫科 三叶虫 芙蓉统 寒武系 皖北地区 中文引用 雷倩萍,彭善池,2022.皖北地区寒武系芙蓉统炒米店组中上部索克虫科三叶虫.古生物学报,61(4):568589.DOI:10.19800/ki.aps.2021071 英文引用 Lei Qian-ping,Peng Shan-chi,2022.Saukiid trilobites from the middleupper Chaumitien Formation(Fu-rongian,Cambrian)in northern Anhui.Acta Palaeontologica Sinica,61(4):568589.DOI:10.19800/ki.aps.2021071 Saukiid trilobites from the middleupper Chaumitien Formation(Furongian,Cambrian)in northern Anhui LEI Qian-ping1,PENG Shan-chi2,3 1 Academic Department of Changzhou Museum,Changzhou 213022,Jiangsu,China;2 Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing 210008,China;3 State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing 210008,China Abstract Hundreds of specimens of saukiid trilobites were collected from the middleupper Chaumitien Formation(upper Jiangshanian through Stage 10,Cambrian)at Fenghuangshan Hill in northern Anhui,China.Four genera and six species(including two new species)are described herein:Eosaukia bella(Walcott,1906),E.anhuiensis sp.nov.,Lo-phosaukia orientalis(Kobayashi,1933),Prosaukia campe(Walcott,1905)and P.xiaoxianensis sp.nov.,Lichengia onigawara Kobayashi,1942.After revising and discussing the generic diagnoses,we reexamine and revise the specific diagnoses of the four previously-published species by comparing their type species with others,and briefly discuss the evolutionary relationships among all six species.Key words Saukiidae,trilobite,Furongian,Cambrian,northern Anhui 4期 雷倩萍、彭善池:皖北寒武三叶虫;Lei and Peng:Saukiid trilobites from Cambrian in Anhui 569 SYSTEMATIC PALEONTOLOGY All specimens described in this paper are deposited at the Changzhou Museum(CZM)and Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences(NIGP).Order Asaphida Salter,1864 Superfamily Dikelocephaloidea Miller,1889 Family Saukiidae Ulrich et Resser,1930 Genus Eosaukia Lu,1954 Eosaukia anhuiensis sp.nov.urn:lsid:zoobank.org:act:EC4770D0-BC7C-418E-A4CF-6AB8328FF4C1(Figs.5,11)Etymology After Anhui Province,where the specimens are collected.Holotype Cranidium(CZMF000143;Fig.5-11)collected from the Chaumitien Formation at Fenghuangshan,Xiaoxian,Anhui Province.Materials Twenty-eight cranidia,12 libregenae,and seven pygedia collected from the interval of WXN-7h to WXN-3k.Diagnosis Cranidium trapezoid,slightly convex.Glabella long,trapezoid,narrowed forward.Four gla-bellar furrows:S1 traverse,curved rearward and deep-ened laterally;S2 short and deep;S3,S4 short and shal-low;occipital ring medium-sized,occipital spine occa-sionally present.Palpebral lobe medium-sized.Anterior area wide(sag.);lateral anterior border furrow of cra-nidium diagonal and shallow.Librigena convex.Lateral border narrow.Genal spines long,hook-like and strongly curved inward.Pygedium triangular,axis wide(tr.),with three axial rings and a terminal piece;pleural furrows and interpleural furrows indistinct.Exoskeleton with granules.Description Cranidium trapezoid,slightly con-vex,length about four-fifths of width.Glabella sub-trapezoid,slightly tapered forward,expanded rear-ward posterior to the mid-length,width about two-thirds of length(sag.).Four pairs of glabellar furrows,S1 traverse,curved rearward and deepened laterally;S2 short(tr.),about one-third of glabellar width,curved rearward;S3 short and shallow,not connected with axial furrows;S4 short and shallow,slightly directed forward.Occipital ring with uniform width,curved rearward;oc-cipital furrow deep and broad,curved rearward;occipi-tal spine occasionally present(Figs.5-8,5-11,5-12).Anterior area wide(sag.),narrowing laterally,and forming an obtuse angled anterior margin,about two-fifths as long as glabellar width;lateral anterior border furrow of cranidium diagonal,wide and shallow.Axial furrows deep and wide.Palpebral lobe moderately sized,extending between S2 and half-length of L1;pal-pebral furrow deep.Palpebral area about one-third as wide as glabella.Facial suture opithoparian:anterior branch of facial suture subparallel,curving axially close to cephalic anterior margin;posterior branch of facial suture gently extending outward,about 20 curved pos-terior margin of cranidium.Posterolateral projection short(exs.),with width about glabellar length.Cra-nidium with granules.Librigena gently convex.Librigenal field sharply sloping to the lateral border;eye socle furrow medium width and deep;lateral border narrow(Fig.5-18)and convex,extending rearward and outward,then gradually curving inward to form a hook-like genal spine;lateral border furrow wide and shallow,forming a depression at the genal angle.Librigena surface with granules.Pygidium convex,semi-oval,width two times of length.Axis strongly convex,two times as long as width,narrowing rearward to the posterior border with three axial rings and a terminal piece.Pleural furrow deep and gently extending rearward and outward;inter-pleural furrow shallow.Pygidial border narrow.Comparison and discussion The new species differs from the type species in having a larger and wid-er eye lobe,and a narrower(sag.)and longer pygidium;Eosaukia walcotti(Mansuy,1915)from Vietnam differs from the new species in having a narrower(sag.)anteri-or area,a librigena without strongly hooked spine;Eo-saukia bella(Walcott,1906)differs from the new spe-cies in having a narrower(sag.)and more traverse ante-rior area,a more convex exoskeleton,a relatively shorter genal spine which is not strongly hooked,and a wider pygidial pleural field;Eosaukia transita(Lu and Zhou,1990)differs from the new species in having a more traverse anterior area,a narrower(sag.)occipital ring,and no occipital spine;Eosaukia tangcunensis(Qian,1983)differs from the new species in having a wider(sag.)anterior area,a more rounded glabella at the front,and a narrower fixigena;Eosaukia combinata(Peng,1992)differs from the new species in having a paral-lel-sided glabella and a greater curved eye lobe.The occipital spine may be present or absent dur-ing the various stages of the ontogeny(Sherglod,1991).The occipital spine may also be caused by dimorphism or taphonomy,such as the case that some of our speci-mens have occipital spines(Figs.5.8,5.11,5.12),while some have not.Occurrence Middleupper Chaumitien Formation,Cambrian,Furongian,northern Anhui.Prosaukia xiaoxianensis sp.nov.urn:lsid:zoobank.org:act:1F502F4C-C9F2-4C88-A9C7-A20C9B1DA971(Figs.9,11)570 古 生 物 学 报 61 卷?1935 Tellerina chinhsiensis Sun,p.48,pl.6,fig.19,not figs.1518.?1965 Ptychaspis shansiensis Sun,Lu et al.,p.426,pl.82,fig.10,not figs.79,11,12.?1965 Tellerina chinhsiensis Sun,Lu et al.,p.455,pl.89,fig.11,not figs.910.?1965 Tellerina sulcatifera Endo,Lu et al.,p.456,pl.89,figs.1516,not figs.1314,17.Etymology After Xiaoxian,Anhui Province,where the specimens are collected.Holotype Cranidium(CZMF000180;Fig.9-5)collected from the Chaumitien Formation at Feng-huangshan,Xiaoxian,Anhui Province.Materials 15 cranidia,three librigenae,and 50 pygidia;collected from WXN7b to 8b.Diagnosis Cranidum sub-trapezoid.Glabella sub-rectangular,moderately convex,tapered forward,rounded anteriorly;three pairs of glabellar furrows,S1 and S2 long,S3 relatively short.Occipital furrow nar-row(sag.,exs.)and distinct,slightly curved centrally;occipital ring moderate width and slightly convex with occipital spine.Palpebral lobe large,arched and located opposite glabellar midlength.Anterior area divided by deep anterior border furrow into preglabellar field and anterior border,anterior area wide(sag.),preglabellar field slightly convex,longer than anterior border.Ante-rior branch of facial suture obviously divergent outward and forward,curving inward close to meet cephalic an-terior margin;posterior branch of facial suture extending outward and rearward.Axial furrow narrow and deep.Palpebral area narrow,slightly convex.Anterior area long,preglabella field convex,longer than anterior bor-der.Librigena wide and subrounded,genal spine short.Pygidium large,semicircle;axis short,with four axial rings and a terminal piece;pleural field smooth.Exo-skeleton smooth,occasionally with granules.Description Cranidium sub-trapezoid,length about three-fourths of width.Glabella sub-trapezoid,moderate convex,gently tapered forward,obtusely rounded anteriorly,length about two-thirds of width.Three pairs of glabellar furrows,S1 long,extending rearward and united sagittally;S2 curved rearward but isolated;S3 short and slightly extending forward.Occipital ring with uniform width and slightly convex with occipital spine;occipital furrow narrow(sag.,exs.)and deep,curving rearward.Palpebral lobe moderately sized and arched,lying opposite the middle of glabella,about one-third of glabellar length.Anterior area wide(sag.)and convex,preglabellar field slightly convex,longer than anterior border;anterior border furrow deep.Facial suture opithoparian with anterior branch strongly divergent forward and outward,curving close to and meet at cephalic anterior margin;posterior branch of facial suture gently extending outward and rearward.Axial furrow deep and narrow.Palpebral area narrow,convex.Glabella smooth,occasionally with granules.Librigena wide and subrounded.Librigenal field gently convex,with equal length and width;lateral bor-der narrow,lateral border furrow shallow.Genal spine short and sharp.Librigena surface smooth.Pygidium semi-circle,length twice of the width.Axis short and strongly convex,sub-cylindrical,nar-rowing rearward in great distance from posterior border;with four axial rings and a terminal piece which strongly convex.Pleural region gently convex with four pleural furrows,deeply extending to lateral border and four feeble inter-pleural furrows.Pygidial border wide and smooth,about two-thirds to four-fifths of axiss length.Axis ended from near(Figs.9-12,9-15)to far from posterior border during ontogenetic development.Comparison and discussion The shape of gla-bella,nature of glabellar furrows and differentiation of anterior area of the new species are consistent with the diagnosis of Prosaukia,but we are unable to assign these specimens to any known species of Prosaukia,because of the differences of other characters The char-acteristics of the anterior area and pygidium of the new species are different from those of P.campe.Some pygidia of Sun(1935,p.48,pl.6,fig.19),Lu et al.(1965,p.426,pl.82,fig.10;p.455,pl.89,fig.11;p.456,pl.89,figs.1516)are similar to those of the new species.They are possibly conspecific.Occurrence Middleupper Chaumitien For-mation,Cambrian,Furongian,northern Anhui and Bai-jiashan of Liaoning Province.1 前 言 华北地区寒武系芙蓉统炒米店组总的时限大致为排碧晚期至特马豆克初期,大多对应于“长山阶”和“凤山阶”,其中凤山阶常见的三叶虫包括索克虫科(Saukiidae),褶盾虫科(Ptychaspididae),济南虫科(Tsinaniidae),无肩虫科(Anomocaridae),宝 塔虫科(Pagodiidae)和嵩里山虫科(Kaolishaniidae)等,其 中 索 克 虫 科 三 叶 虫 主 要 有 Eosaukia、Lophosaukia和Prosaukia等属。索克虫科(Saukiidae)作为芙蓉世晚期最庞大的一类三叶虫,原来包括30个属,数百个种(主要分布于劳伦Laurentia和冈瓦纳Gondwana大陆)。有学者(Ludvigsen et al.,1989;Lee and Choi,2011)认 4期 雷倩萍、彭善池:皖北寒武三叶虫;Lei and Peng:Saukiid trilobites from Cambrian in Anhui 571 为因为索克虫科虽然具有不同于指纹头虫科(Dikelocephalidae)的窄而突出的头部腹边缘,但此特征与归入指纹头虫超科的褶盾虫科相同,因而应将其作为晚出异名与指纹头虫科合并。但笔者更为赞同Fortey(见Whittington and Kelly,1997)的观点,还是应将Saukiidae与Dikelocephalidae作为两个独立的科。Lochman-Balk(in Moore,1959)对于本科的定义为:亚等尾型,后颊类面线;头鞍方形至长方形,23对头鞍沟,S1一般横穿;前边缘沟可能不显;眼中等大小至较大,位于头鞍中部或偏后;活动颊宽,具颊刺;尾椭圆形至圆形,无边缘沟,边缘宽度不一;表面光滑或具疣点。本文基本沿用这个定义,头鞍沟数量可修订为24对。而指纹头虫科的不同特征在于头尾比例更趋于等尾型,前边缘宽大,前边缘沟通常不显。索克虫科三叶虫在芙蓉统江山阶上部至第十阶极为繁盛,在劳伦大陆该阶段的生物地层划分对比方面具有重要的作用(Bell et al.,1952;Berg,1953;Grant,1962,1965;Winston and Nicholls,1967;Longacre,1970;Stitt,1971,1977;Westrop,1986;Ludvigsen et al.,1989;Lee and Choi,2011),它们中的一些分子也对澳大利亚、中国、哈萨克斯坦的芙蓉世生物地层的划分与对比意义重大(见Geyer and Shergold,2000)。2 地质背景及材料 本文全部标本均采自安徽萧县西北方向凤凰山剖面(雷倩萍,2021,图1)的凤山阶炒米店组灰岩中。研究区地质背景概述见雷倩萍(2014,98页)。图 1 剖面岩性柱状图及索克虫科三叶虫的分布图 Fig.1 Stratigraphic column of the Fenghuangshan section and stratigraphic distribution of saukiid trilobites within the section572 古 生 物 学 报 61 卷 皖北地区寒武系芙蓉统上部即凤山期地层发育较好,化石也较为丰富。研究区地层分区属于华北地层区淮河地层分区淮北地层小区,区内寒武系出露齐全,尤以寒武系中上部出露较好,广布于萧县凤凰山、灵山、白土、庄里,宿县夹沟、韩家,淮北市相山等地(安徽省地质矿产局,1987)。该剖面地层情况见图1。本文全部标本均保存在常州博物馆(CZM)和中国科学院南京地质古生物研究所(NIGP)。3 系统古生物学 本文中所使用的三叶虫形态描述术语主要参考卢衍豪等(1963),Shergold(1975),Whittington和Kelly(1997)与彭善池(2020)所述。文中所有标本产地为萧县凤凰山(WXN)。栉虫目 Order Asaphida Salter,1864 指纹头虫超科 Superfamily Dikelocephaloidea Miller,1889 索克虫科 Family Saukiidae Ulrich et Resser,1930 始索克虫属 Genus Eosaukia Lu,1954 异名录见Lee和Choi(2011,p.284)。另补充:2011 Eosaukia Lu,Lee and Choi,p.284.模 式 种 Eosaukia latilimbata Lu,1954 (p.145,pl.1,figs.5,6;Lu and Zhou,1990,p.32,pl.10,figs.13;彭善池,2020,图版146,图1,2,5),产自中国贵州三都组;原始指定。其他种 Ptychaspis bella Walcott,1906(p.585;Walcott,1913,p.180,pl.17,fig.9),产自中国山西;Ptychaspis walcotti Mansuy,1915(p.22,pl.3,figs.1az;1916,p.32,pl.5,fig.10ae,gi),产自越南Haut-Tonkin;Tellerina paichiaensis Kobayashi,1933(p.130,pl.8,fig.9),产自中国辽宁五湖嘴;“Eosaukia”buravasi Kobayashi,1957(p.376378,pl.5,figs.110,1318?),产自泰国;Calvinella solitaria Shergold,1975(p.141,pl.23,figs.17),产自澳大利亚昆士兰西部;“Calvinella”elongata Xiang in Sun et Xiang,1979(孙云铸和项礼文,1011 页,图 版 4,图 1113),产 自 云 南 西 部;Calvinella acuata Guo et Duan in Guo et al.,1982(郭鸿俊等,19页,图版3,图3b,11,非12),产自河北抚宁;Pseudocalvinella spinosa Qiu,1984(仇洪安,337页,图版1,图1115),产自安徽泾县;Mic-tosaukia maculata Qian,1985(p.147148,pl.5,fig.8a,text-fig.2),产自安徽泾县;Mictosaukia(Mic-tosaukioidia)transita Lu et Zhou,1990(p.3435,pl.11,figs.510),产自贵州三都;Mictosaukia sp.(Shergold,1991,p.24,pl.5,figs.29),产自澳大利亚北部;Mictosaukia combinata Peng,1992(p.53,figs.24HJ,L,M),产自湖南沈家湾。属征 头盖强烈凸起,亚梯形。头鞍前部未分化,具一对清晰的头盖前侧边缘沟。一般可见34对鞍沟,S1横穿,S2、S3短,有时模糊不显。眼叶较大或中等大小,距头鞍较远。活动颊区强烈凸起,颊刺较长。尾部横宽,24个轴节,边缘窄。壳体表面一般具疣点或线纹。讨论 Eosaukia是卢衍豪(1954)根据一对较完整但稍有变形的背壳内外模标本建立的,以具有一对较为明显的对角前侧边缘沟为特征而与其他索克虫类相区别,然而该标本的头鞍前区已破损,影响了对其前边缘特征的判断和比较。Kobayashi(1957)详细讨论了Eosaukia属,认为该属与其他索克虫类不一样,不仅仅因为较早的地层分布,而且在胸节数目和尾部形状等方面也与众不同。他指出典型的索克虫类尾部更长,更圆,分节更多,肋沟、间肋沟清楚;而Eosaukia则完全不是这样,它的尾部更类似于褶盾虫和章氏虫的尾部。笔者观察后基本同意Kobayashi的观点,但有关地层时代较早的看法持保留意见,因为Sinosaukia、Prosaukia等的层位还早于本属。之后Shergold(1991)详细讨论了该属的模式标本并附以清晰翻拍的标本照片(pl.5,figs.2022)。Shergold(1975)建立Mictosaukia是根据其具有Saukia(头鞍窄)和Tellerina(相对较长的头鞍前部)的交叉特征而建立的,其模式标本为Tellerina ori-entalis Resser et Endo(见Endo,1937,p.293,pl.57,figs.17)。Shergold(1991)再次强调其不同特征是眼叶靠近头鞍、后侧翼较长(tr.)和尾部分节最多可达5节。但其头盖特征总体与Eosaukia较为相似,主要区别仅在于尾部。因此该属究竟为有效属,还是 4期 雷倩萍、彭善池:皖北寒武三叶虫;Lei and Peng:Saukiid trilobites from Cambrian in Anhui 573 Eosaukia的晚出异名还需更多的材料来佐证。孙红兵(1990,102页)新建了一属Scolosaukia,并将该属与Calvi