Romer將(jiang)原來Wiman所(suo)命(ming)名(ming)(ming)的(de)(de)Helopus重新在1956年命(ming)名(ming)(ming)為盤足(zu)龍(long),同時提出一(yi)個盤族類(lei)的(de)(de)新亞科(ke)。到(dao)(dao)1934年,楊(yang)鐘健(jian)協同卞美年考察(cha)這個化(hua)石點,又(you)采(cai)集(ji)一(yi)些破碎不(bu)全(quan)的(de)(de)骨(gu)骼,大多(duo)屬(shu)(shu)于(yu)盤足(zu)龍(long)的(de)(de)一(yi)部分,而少部分則經過監定屬(shu)(shu)于(yu)獸腳類(lei)恐龍(long)以及劍龍(long)類(lei)的(de)(de)背部突棘。盤足(zu)龍(long)的(de)(de)頭骨(gu)一(yi)般與圓頂龍(long)相比較,但較為低平。它具(ju)(ju)有極(ji)為碩長(chang)的(de)(de)脖子。總(zong)共有17個頸(jing)椎。頸(jing)椎體的(de)(de)神經棘很(hen)低,在肩部附近(jin)開叉(cha)很(hen)寬廣。據推估(gu)這具(ju)(ju)師氏盤足(zu)龍(long)體長(chang)達到(dao)(dao)10到(dao)(dao)11公尺,是中國所(suo)正式命(ming)名(ming)(ming)的(de)(de)第一(yi)只蜥腳類(lei)恐龍(long)。
我國(guo)發現(xian)(xian)(xian)(xian)的(de)(de)早的(de)(de)巨(ju)龍(long)形類恐(kong)龍(long)是師(shi)氏盤足龍(long)(Euhelopus zdanskyi),同(tong)時這還(huan)(huan)是在(zai)(zai)(zai)我國(guo)發現(xian)(xian)(xian)(xian)的(de)(de)第一(yi)只蜥(xi)腳(jiao)類恐(kong)龍(long),早在(zai)(zai)(zai)1921年奧地利(li)古生物學家(jia)(jia)師(shi)丹斯(si)基(Otto Zdansky,1894—1988)在(zai)(zai)(zai)瑞典烏普(pu)薩拉大(da)學(Uppsala University)的(de)(de)古生物學家(jia)(jia)維曼(man)(Prof Carl Wiman,1867—1944)的(de)(de)建(jian)議下前往中國(guo),在(zai)(zai)(zai)中國(guo)他有許(xu)多重大(da)的(de)(de)發現(xian)(xian)(xian)(xian),比(bi)如:著名的(de)(de)古中華虎(Panthera palaeosinensis or "Felis (Panthera)" palaeosinensis),北(bei)京猿人(ren)(Homo erectus pekinensis or "Sinanthropus pekinensis")以及三趾(zhi)馬動物群等都(dou)(dou)是他發現(xian)(xian)(xian)(xian)的(de)(de);在(zai)(zai)(zai)1922年到1923年師(shi)丹斯(si)基和(he)我國(guo)地質學家(jia)(jia)譚(tan)錫(xi)疇在(zai)(zai)(zai)山(shan)東省蒙陰縣(xian)寧家(jia)(jia)溝的(de)(de)上侏羅(luo)統(tong)或(huo)下白(bai)堊統(tong)的(de)(de)蒙陰組(Meng-Yin Formation)地層發現(xian)(xian)(xian)(xian)并挖掘了(le)一(yi)些恐(kong)龍(long)化(hua)石,其中包括(kuo)獸腳(jiao)類牙齒和(he)劍龍(long)類的(de)(de)骨(gu)板,同(tong)時還(huan)(huan)有兩(liang)具不(bu)完整的(de)(de)蜥(xi)腳(jiao)類恐(kong)龍(long)骨(gu)骼,師(shi)丹斯(si)基把自己發現(xian)(xian)(xian)(xian)的(de)(de)大(da)部分(fen)化(hua)石都(dou)(dou)送到瑞典的(de)(de)烏普(pu)薩拉大(da)學由(you)維曼(man)研究,這兩(liang)具蜥(xi)腳(jiao)類恐(kong)龍(long)骨(gu)骼也是一(yi)樣。
維曼在仔細(xi)研究了師(shi)丹斯基送來化石后(hou)將它們命(ming)(ming)名(ming)(ming)為(wei)"Helopus" zdanskyi,屬名(ming)(ming)“Helopus”是希臘語“濕地(di)(di)的(de)(de)腳(jiao)”的(de)(de)意(yi)思(si)(si),而種名(ming)(ming)“zdanskyi”是紀念師(shi)丹斯基發現(xian)了這(zhe)種恐龍(long)(long)(long);不過在1956年羅默(mo)(Alfred Sherwood Romer,1894—1973)發現(xian)一屬鳥類已經先行占有了“Helopus”這(zhe)個屬名(ming)(ming),所后(hou)就被"Helopus" zdanskyi重新(xin)命(ming)(ming)名(ming)(ming)為(wei)師(shi)氏(shi)盤(pan)足(zu)(zu)(zu)龍(long)(long)(long)(Euhelopus zdanskyi),屬名(ming)(ming)盤(pan)足(zu)(zu)(zu)龍(long)(long)(long)(Euhelopus)的(de)(de)意(yi)思(si)(si)是“出色(se)的(de)(de)濕地(di)(di)的(de)(de)腳(jiao)”,我國(guo)的(de)(de)古(gu)生物學家因為(wei)過去認為(wei)蜥腳(jiao)類恐龍(long)(long)(long)的(de)(de)足(zu)(zu)(zu)部的(de)(de)只顧(gu)和趾(zhi)骨是散開(kai),像盤(pan)子一樣,所以(yi)翻譯為(wei)“盤(pan)足(zu)(zu)(zu)龍(long)(long)(long)”;同時羅默(mo)認為(wei)盤(pan)足(zu)(zu)(zu)龍(long)(long)(long)的(de)(de)特征(zheng)獨特,所以(yi)建立了一個新(xin)的(de)(de)亞(ya)(ya)科(ke)(ke)——盤(pan)足(zu)(zu)(zu)龍(long)(long)(long)亞(ya)(ya)科(ke)(ke)(Euhelopodinae),當時歸入腕龍(long)(long)(long)科(ke)(ke)(Brachiosauridae),后(hou)來也(ye)有人把盤(pan)足(zu)(zu)(zu)龍(long)(long)(long)亞(ya)(ya)科(ke)(ke)歸入圓頂(ding)龍(long)(long)(long)科(ke)(ke)(Camarasauridae)或者馬門溪龍(long)(long)(long)科(ke)(ke)(Mamenchisauridae)的(de)(de),我國(guo)一些老一輩(bei)的(de)(de)古(gu)生物學家目前多同意(yi)盤(pan)足(zu)(zu)(zu)龍(long)(long)(long)亞(ya)(ya)科(ke)(ke)歸入圓頂(ding)龍(long)(long)(long)科(ke)(ke);劍橋大學的(de)(de)阿(a)普徹奇(qi)(Paul Publication Upchurch)在1995年進一步提出了盤(pan)足(zu)(zu)(zu)龍(long)(long)(long)科(ke)(ke)(Euhelopodidae),并認為(wei)在中(zhong)國(guo)中(zhong)侏羅統到白(bai)堊系(xi)發現(xian)的(de)(de)大量的(de)(de)長(chang)頸椎蜥腳(jiao)類恐龍(long)(long)(long)都(dou)屬于(yu)這(zhe)一支系(xi)(Upchurch, 1995, 1998)。
但是威爾遜(Jeff Wilson)和(he)塞里諾(Paul Sereno)等人認為(wei)盤足(zu)龍的(de)頸(jing)椎神經(jing)弓和(he)肩帶結構十分進(jin)步,所以(yi)應該屬(shu)于(yu)巨(ju)龍形類;而峨嵋龍(Omeisaurus)的(de)頭骨(gu),掌骨(gu),腰帶和(he)距(ju)骨(gu)的(de)特征(zheng)過于(yu)原始,并不屬(shu)于(yu)新蜥腳類恐龍(Neosauropod),和(he)盤足(zu)龍關系很(hen)遠,目前很(hen)多學(xue)者都同意(yi)這種說法(Wilson et Sereno, 1998,1999,2000, Wilson, 2002,Ksepka et Norell, 2006),所以(yi)我們在這里也把盤足(zu)龍作為(wei)巨(ju)龍形類恐龍進(jin)行描述。
因為盤(pan)足龍(long)的(de)(de)化(hua)石只發現(xian)了頭(tou)骨(gu),大部(bu)分頸椎(zhui),肩(jian)帶,前(qian)肢(zhi)(zhi),背椎(zhui),腰帶和后肢(zhi)(zhi)等,所以(yi)我(wo)們對(dui)它的(de)(de)了解也主(zhu)要(yao)是這些(xie)(xie),至于尾巴的(de)(de)形態(tai)只能推(tui)測。盤(pan)足龍(long)的(de)(de)頭(tou)骨(gu)和圓頂龍(long)的(de)(de)比(bi)較(jiao)接近(jin),都屬于比(bi)較(jiao)粗壯(zhuang)而(er)(er)高的(de)(de)類(lei)型,而(er)(er)且鼻孔也很(hen)(hen)大,牙齒也都屬于粗壯(zhuang)的(de)(de)勺形齒;但是盤(pan)足龍(long)的(de)(de)頭(tou)骨(gu)比(bi)圓頂龍(long)的(de)(de)要(yao)長一(yi)些(xie)(xie)。盤(pan)足龍(long)的(de)(de)頸椎(zhui)很(hen)(hen)長,而(er)(er)且數量很(hen)(hen)多(duo),有(you)十七個,估計長度超(chao)過體長的(de)(de)一(yi)半;后部(bu)頸椎(zhui)的(de)(de)神經棘低,而(er)(er)且分叉(cha)。盤(pan)足龍(long)的(de)(de)肩(jian)帶很(hen)(hen)發達(da),肩(jian)臼窩很(hen)(hen)淺,中部(bu)形成一(yi)個斜面,后肢(zhi)(zhi)較(jiao)短(duan),所以(yi)古(gu)生物學家推(tui)測盤(pan)足龍(long)的(de)(de)前(qian)肢(zhi)(zhi)很(hen)(hen)可能很(hen)(hen)發達(da);因為前(qian)肢(zhi)(zhi)很(hen)(hen)長,所以(yi)盤(pan)足龍(long)不用(yong)把脖子抬得太高就可以(yi)吃(chi)到(dao)高處的(de)(de)樹葉。
巨龍(long)(long)形類(lei)(Titanosauriformes)恐龍(long)(long)屬于蜥(xi)(xi)腳(jiao)次(ci)亞目(Sauropoda)真蜥(xi)(xi)腳(jiao)類(lei)(Eusauropoda)新蜥(xi)(xi)腳(jiao)類(lei)(Neosauropoda)大(da)鼻龍(long)(long)類(lei)(Macronaria),和圓頂龍(long)(long)科(Camarasauridae)是(shi)姐(jie)妹群;巨龍(long)(long)形類(lei)主(zhu)要包括(kuo)腕(wan)龍(long)(long)科(Brachiosauridae),盤足(zu)龍(long)(long)科(Euhelopodidae)和巨龍(long)(long)類(lei)(Titanosauria)。巨龍(long)(long)形類(lei)包括(kuo)很多著名的(de)(de)恐龍(long)(long),比如坦(tan)(tan)桑(sang)尼亞上侏羅統的(de)(de)坦(tan)(tan)達(da)古魯層(ceng)(Tendaguru Beds)地(di)層(ceng)發(fa)(fa)現(xian)的(de)(de)布氏(shi)腕(wan)龍(long)(long)(Brachiosaurus (Giraffatitan) brancai or Giraffatitan brancai),我國(guo)山東省(sheng)上侏羅統或下白堊統的(de)(de)蒙陰組(zu)(Meng-Yin Formation)地(di)層(ceng)發(fa)(fa)現(xian)的(de)(de)師氏(shi)盤足(zu)龍(long)(long)(Euhelopus zdanskyi),阿根廷下白堊統的(de)(de)里約(yue)利邁(mai)河組(zu)(Rio Limay Formation)地(di)層(ceng)發(fa)(fa)現(xian)的(de)(de)阿根廷龍(long)(long)(Argentinosaurus),我國(guo)河南省(sheng)的(de)(de)蟒川組(zu)(Mangchuan Formation)地(di)層(ceng)發(fa)(fa)現(xian)的(de)(de)汝陽黃河巨龍(long)(long)(Huanghetitan ruyangensis)等。
巨龍(long)形類的(de)(de)特征包括沒有前(qian)(qian)(qian)眶前(qian)(qian)(qian)孔;上(shang)頜骨(gu)(gu)(gu)(gu)(gu)與前(qian)(qian)(qian)上(shang)頜骨(gu)(gu)(gu)(gu)(gu)的(de)(de)接觸(chu)面呈(cheng)棒狀;齒骨(gu)(gu)(gu)(gu)(gu)的(de)(de)多(duo)面陡峭。前(qian)(qian)(qian)棘突(tu)板(ban)(ban);頸(jing)椎(zhui)普遍被加長;背椎(zhui)氣腔化;背椎(zhui)和前(qian)(qian)(qian)部尾椎(zhui)神(shen)經(jing)弓(gong)只比椎(zhui)體(ti)略窄;前(qian)(qian)(qian)段的(de)(de)背肋寬廣,呈(cheng)板(ban)(ban)狀;中(zhong)后(hou)部尾椎(zhui)神(shen)經(jing)弓(gong)位于(yu)椎(zhui)體(ti)的(de)(de)前(qian)(qian)(qian)面;脈(mo)弧不分(fen)(fen)(fen)叉(cha);中(zhong)后(hou)部脈(mo)弧向后(hou)彎曲(qu)。肩(jian)臼窩向前(qian)(qian)(qian)腹側和內側傾(qing)斜;掌骨(gu)(gu)(gu)(gu)(gu)長超過脛骨(gu)(gu)(gu)(gu)(gu)的(de)(de)百分(fen)(fen)(fen)之四十五以(yi)上(shang);第一(yi)指爪縮小或消失。股骨(gu)(gu)(gu)(gu)(gu)骨(gu)(gu)(gu)(gu)(gu)干近(jin)端三分(fen)(fen)(fen)之一(yi)處側向突(tu)出翻轉(zhuan);恥(chi)骨(gu)(gu)(gu)(gu)(gu)的(de)(de)坐骨(gu)(gu)(gu)(gu)(gu)關節面較為(wei)縱深;恥(chi)骨(gu)(gu)(gu)(gu)(gu)突(tu)前(qian)(qian)(qian)的(de)(de)腸骨(gu)(gu)(gu)(gu)(gu)板(ban)(ban)明顯高于(yu)其后(hou)的(de)(de)腸骨(gu)(gu)(gu)(gu)(gu)板(ban)(ban)等(Wilson, 2002,Upchurch et al., 2004,Wilson, 2005,Mo et al., 2006)。
巨(ju)龍(long)(long)形類(lei)(lei)早出現(xian)在(zai)中侏羅世或晚侏羅世,不過進入(ru)白堊(e)(e)紀(ji)(ji)(ji)后才變得十(shi)分繁盛,而且是白堊(e)(e)紀(ji)(ji)(ji),特(te)別是晚白堊(e)(e)世主要的(de)(de)(de)(de)(de)蜥腳類(lei)(lei)恐(kong)龍(long)(long)。近來(lai)對南方(fang)岡瓦(wa)納(na)大陸和(he)我國發現(xian)的(de)(de)(de)(de)(de)巨(ju)龍(long)(long)形類(lei)(lei),特(te)別是一些巨(ju)龍(long)(long)類(lei)(lei)的(de)(de)(de)(de)(de)研究徹底掃除了比如“蜥腳類(lei)(lei)進入(ru)白堊(e)(e)紀(ji)(ji)(ji)后逐(zhu)漸被鳥(niao)臀類(lei)(lei)取代并滅絕”等人們(men)過去對蜥腳類(lei)(lei)的(de)(de)(de)(de)(de)一系(xi)列錯誤認識,我們(men)現(xian)在(zai)知道不僅僅是巨(ju)龍(long)(long)形類(lei)(lei),在(zai)白堊(e)(e)紀(ji)(ji)(ji)還有雷巴齊(qi)斯(si)龍(long)(long)科(Rebbachisauridae)和(he)叉背(bei)龍(long)(long)科(Dicraeosauridae)等很多(duo)其(qi)他的(de)(de)(de)(de)(de)蜥腳類(lei)(lei)恐(kong)龍(long)(long),而且它們(men)一直是南方(fang)岡瓦(wa)納(na)大陸主要的(de)(de)(de)(de)(de)植食(shi)動物(wu),并且其(qi)中一部(bu)分甚至(zhi)可能(neng)侵入(ru)或者起源于北(bei)方(fang)勞亞(ya)(ya)大陸,和(he)鳥(niao)臀類(lei)(lei)競爭。國外的(de)(de)(de)(de)(de)白堊(e)(e)紀(ji)(ji)(ji)的(de)(de)(de)(de)(de)巨(ju)龍(long)(long)形類(lei)(lei)主要分布在(zai)南方(fang)岡瓦(wa)納(na)大陸的(de)(de)(de)(de)(de)南美(mei)洲(zhou),印度,非(fei)洲(zhou)北(bei)部(bu),馬(ma)達加斯(si)加,澳大利亞(ya)(ya)和(he)南歐(ou),也有部(bu)分化石發現(xian)于北(bei)美(mei)洲(zhou)和(he)俄羅斯(si)西伯利亞(ya)(ya)地區南部(bu)。
我(wo)(wo)國系統的(de)(de)(de)進行巨(ju)龍(long)形(xing)(xing)(xing)類研(yan)究(jiu)起步較晚,一(yi)(yi)方面(mian)是(shi)因(yin)為早(zao)(zao)期(qi)(qi)發現的(de)(de)(de)材料(liao)較少,另一(yi)(yi)方面(mian)是(shi)過去國內的(de)(de)(de)分類體系和(he)材料(liao)更(geng)新(xin)(xin)受到(dao)新(xin)(xin)研(yan)究(jiu)的(de)(de)(de)影響(xiang)比較小,所以(yi)一(yi)(yi)些(xie)錯誤的(de)(de)(de)觀點和(he)陳(chen)舊的(de)(de)(de)認識沒有得到(dao)及時(shi)更(geng)新(xin)(xin);但是(shi)最近在(zai)我(wo)(wo)國的(de)(de)(de)吉林(lin)省,遼(liao)寧省,山西省,河南省,甘(gan)肅省,廣西省和(he)浙江(jiang)省等(deng)地發現了一(yi)(yi)些(xie)巨(ju)龍(long)形(xing)(xing)(xing)類的(de)(de)(de)材料(liao),雖然這些(xie)材料(liao)也都大多(duo)并(bing)不完整,但是(shi)在(zai)一(yi)(yi)定程度上(shang)是(shi)我(wo)(wo)們對了解巨(ju)龍(long)形(xing)(xing)(xing)類的(de)(de)(de)起源和(he)早(zao)(zao)期(qi)(qi)演化以(yi)及白堊紀時(shi)期(qi)(qi)東(dong)亞(ya)的(de)(de)(de)生態環(huan)境的(de)(de)(de)重要的(de)(de)(de)材料(liao)。