Romer將原來Wiman所命名(ming)(ming)的(de)(de)Helopus重新(xin)在(zai)1956年(nian)命名(ming)(ming)為(wei)(wei)盤足龍(long),同時(shi)提出一(yi)(yi)個盤族類(lei)(lei)的(de)(de)新(xin)亞科。到1934年(nian),楊鐘健(jian)協(xie)同卞(bian)美年(nian)考察(cha)這(zhe)個化石點,又采(cai)集一(yi)(yi)些(xie)破碎不全的(de)(de)骨骼,大多屬于盤足龍(long)的(de)(de)一(yi)(yi)部(bu)(bu)分(fen),而少(shao)部(bu)(bu)分(fen)則經過監定屬于獸腳類(lei)(lei)恐龍(long)以及(ji)劍龍(long)類(lei)(lei)的(de)(de)背部(bu)(bu)突棘(ji)。盤足龍(long)的(de)(de)頭骨一(yi)(yi)般與圓頂龍(long)相(xiang)比較,但(dan)較為(wei)(wei)低平。它具有極為(wei)(wei)碩(shuo)長的(de)(de)脖子。總共有17個頸椎(zhui)。頸椎(zhui)體(ti)的(de)(de)神經棘(ji)很低,在(zai)肩部(bu)(bu)附近開叉很寬廣。據推估這(zhe)具師氏盤足龍(long)體(ti)長達到10到11公尺,是(shi)中國(guo)所正式命名(ming)(ming)的(de)(de)第一(yi)(yi)只蜥腳類(lei)(lei)恐龍(long)。
我國(guo)(guo)(guo)(guo)發現(xian)(xian)的(de)(de)(de)(de)早的(de)(de)(de)(de)巨(ju)龍(long)形類(lei)(lei)(lei)(lei)恐(kong)(kong)龍(long)是師(shi)(shi)氏盤足龍(long)(Euhelopus zdanskyi),同時(shi)這(zhe)還是在(zai)我國(guo)(guo)(guo)(guo)發現(xian)(xian)的(de)(de)(de)(de)第(di)一只(zhi)蜥腳類(lei)(lei)(lei)(lei)恐(kong)(kong)龍(long),早在(zai)1921年(nian)奧地利古(gu)(gu)(gu)生物學(xue)(xue)家(jia)師(shi)(shi)丹(dan)斯基(ji)(Otto Zdansky,1894—1988)在(zai)瑞典烏普薩拉(la)大學(xue)(xue)(Uppsala University)的(de)(de)(de)(de)古(gu)(gu)(gu)生物學(xue)(xue)家(jia)維(wei)曼(man)(man)(Prof Carl Wiman,1867—1944)的(de)(de)(de)(de)建議下前往中(zhong)(zhong)國(guo)(guo)(guo)(guo),在(zai)中(zhong)(zhong)國(guo)(guo)(guo)(guo)他有許多重(zhong)大的(de)(de)(de)(de)發現(xian)(xian),比如:著名的(de)(de)(de)(de)古(gu)(gu)(gu)中(zhong)(zhong)華(hua)虎(Panthera palaeosinensis or "Felis (Panthera)" palaeosinensis),北京猿人(Homo erectus pekinensis or "Sinanthropus pekinensis")以及三趾(zhi)馬動物群等(deng)都(dou)是他發現(xian)(xian)的(de)(de)(de)(de);在(zai)1922年(nian)到(dao)(dao)1923年(nian)師(shi)(shi)丹(dan)斯基(ji)和我國(guo)(guo)(guo)(guo)地質學(xue)(xue)家(jia)譚(tan)錫疇在(zai)山東省蒙(meng)陰縣寧家(jia)溝的(de)(de)(de)(de)上侏(zhu)羅統或(huo)下白堊統的(de)(de)(de)(de)蒙(meng)陰組(Meng-Yin Formation)地層(ceng)發現(xian)(xian)并挖掘了(le)一些恐(kong)(kong)龍(long)化石(shi)(shi),其中(zhong)(zhong)包括獸腳類(lei)(lei)(lei)(lei)牙齒和劍龍(long)類(lei)(lei)(lei)(lei)的(de)(de)(de)(de)骨(gu)板,同時(shi)還有兩具(ju)(ju)不完整的(de)(de)(de)(de)蜥腳類(lei)(lei)(lei)(lei)恐(kong)(kong)龍(long)骨(gu)骼,師(shi)(shi)丹(dan)斯基(ji)把自己發現(xian)(xian)的(de)(de)(de)(de)大部分化石(shi)(shi)都(dou)送到(dao)(dao)瑞典的(de)(de)(de)(de)烏普薩拉(la)大學(xue)(xue)由維(wei)曼(man)(man)研究,這(zhe)兩具(ju)(ju)蜥腳類(lei)(lei)(lei)(lei)恐(kong)(kong)龍(long)骨(gu)骼也是一樣。
維曼(man)在仔細研究(jiu)了(le)師(shi)(shi)丹斯(si)基(ji)送來化(hua)石后(hou)將它們命(ming)名(ming)為(wei)"Helopus" zdanskyi,屬(shu)名(ming)“Helopus”是(shi)(shi)希(xi)臘語(yu)“濕(shi)地的(de)(de)(de)腳(jiao)”的(de)(de)(de)意(yi)思,而種名(ming)“zdanskyi”是(shi)(shi)紀念師(shi)(shi)丹斯(si)基(ji)發現(xian)了(le)這(zhe)種恐龍(long)(long)(long)(long);不(bu)過在1956年(nian)羅(luo)默(Alfred Sherwood Romer,1894—1973)發現(xian)一(yi)屬(shu)鳥類已經(jing)先行占有了(le)“Helopus”這(zhe)個屬(shu)名(ming),所后(hou)就被"Helopus" zdanskyi重新命(ming)名(ming)為(wei)師(shi)(shi)氏(shi)盤(pan)(pan)足(zu)(zu)龍(long)(long)(long)(long)(Euhelopus zdanskyi),屬(shu)名(ming)盤(pan)(pan)足(zu)(zu)龍(long)(long)(long)(long)(Euhelopus)的(de)(de)(de)意(yi)思是(shi)(shi)“出色的(de)(de)(de)濕(shi)地的(de)(de)(de)腳(jiao)”,我(wo)國的(de)(de)(de)古生物(wu)學(xue)家因為(wei)過去認(ren)為(wei)蜥腳(jiao)類恐龍(long)(long)(long)(long)的(de)(de)(de)足(zu)(zu)部的(de)(de)(de)只顧和趾骨是(shi)(shi)散開,像盤(pan)(pan)子(zi)一(yi)樣,所以(yi)翻譯為(wei)“盤(pan)(pan)足(zu)(zu)龍(long)(long)(long)(long)”;同(tong)時羅(luo)默認(ren)為(wei)盤(pan)(pan)足(zu)(zu)龍(long)(long)(long)(long)的(de)(de)(de)特(te)征獨特(te),所以(yi)建立了(le)一(yi)個新的(de)(de)(de)亞(ya)(ya)科(ke)(ke)(ke)——盤(pan)(pan)足(zu)(zu)龍(long)(long)(long)(long)亞(ya)(ya)科(ke)(ke)(ke)(Euhelopodinae),當時歸入腕龍(long)(long)(long)(long)科(ke)(ke)(ke)(Brachiosauridae),后(hou)來也有人(ren)把盤(pan)(pan)足(zu)(zu)龍(long)(long)(long)(long)亞(ya)(ya)科(ke)(ke)(ke)歸入圓頂龍(long)(long)(long)(long)科(ke)(ke)(ke)(Camarasauridae)或者馬門溪龍(long)(long)(long)(long)科(ke)(ke)(ke)(Mamenchisauridae)的(de)(de)(de),我(wo)國一(yi)些老一(yi)輩的(de)(de)(de)古生物(wu)學(xue)家目前多(duo)同(tong)意(yi)盤(pan)(pan)足(zu)(zu)龍(long)(long)(long)(long)亞(ya)(ya)科(ke)(ke)(ke)歸入圓頂龍(long)(long)(long)(long)科(ke)(ke)(ke);劍橋大學(xue)的(de)(de)(de)阿普徹奇(Paul Publication Upchurch)在1995年(nian)進一(yi)步提出了(le)盤(pan)(pan)足(zu)(zu)龍(long)(long)(long)(long)科(ke)(ke)(ke)(Euhelopodidae),并認(ren)為(wei)在中國中侏羅(luo)統到白堊系(xi)發現(xian)的(de)(de)(de)大量的(de)(de)(de)長(chang)頸椎蜥腳(jiao)類恐龍(long)(long)(long)(long)都屬(shu)于這(zhe)一(yi)支(zhi)系(xi)(Upchurch, 1995, 1998)。
但是威爾遜(Jeff Wilson)和(he)塞里(li)(li)諾(Paul Sereno)等人認為盤(pan)(pan)足龍(long)(long)(long)的(de)頸椎(zhui)神(shen)經弓和(he)肩(jian)帶(dai)結構十(shi)分(fen)進步,所(suo)以應該屬于(yu)巨(ju)龍(long)(long)(long)形類;而峨嵋龍(long)(long)(long)(Omeisaurus)的(de)頭(tou)骨(gu),掌骨(gu),腰帶(dai)和(he)距(ju)骨(gu)的(de)特征過(guo)于(yu)原始,并(bing)不(bu)屬于(yu)新蜥(xi)腳類恐龍(long)(long)(long)(Neosauropod),和(he)盤(pan)(pan)足龍(long)(long)(long)關系(xi)很遠,目前(qian)很多學者都同意這種(zhong)說法(fa)(Wilson et Sereno, 1998,1999,2000, Wilson, 2002,Ksepka et Norell, 2006),所(suo)以我們在這里(li)(li)也(ye)把(ba)盤(pan)(pan)足龍(long)(long)(long)作為巨(ju)龍(long)(long)(long)形類恐龍(long)(long)(long)進行描述。
因(yin)為盤足(zu)龍的(de)(de)(de)(de)(de)化石只發現了頭(tou)骨,大部分頸椎,肩(jian)帶,前肢(zhi),背椎,腰帶和后肢(zhi)等,所以我(wo)們對它的(de)(de)(de)(de)(de)了解(jie)也(ye)主要(yao)(yao)是這些(xie),至于尾巴的(de)(de)(de)(de)(de)形(xing)(xing)態(tai)只能(neng)推測(ce)。盤足(zu)龍的(de)(de)(de)(de)(de)頭(tou)骨和圓(yuan)頂(ding)龍的(de)(de)(de)(de)(de)比較接近(jin),都屬于比較粗壯而(er)高的(de)(de)(de)(de)(de)類(lei)型(xing),而(er)且鼻孔(kong)也(ye)很(hen)大,牙齒也(ye)都屬于粗壯的(de)(de)(de)(de)(de)勺形(xing)(xing)齒;但(dan)是盤足(zu)龍的(de)(de)(de)(de)(de)頭(tou)骨比圓(yuan)頂(ding)龍的(de)(de)(de)(de)(de)要(yao)(yao)長(chang)一(yi)些(xie)。盤足(zu)龍的(de)(de)(de)(de)(de)頸椎很(hen)長(chang),而(er)且數量(liang)很(hen)多,有十(shi)七個(ge),估計長(chang)度(du)超(chao)過體長(chang)的(de)(de)(de)(de)(de)一(yi)半;后部頸椎的(de)(de)(de)(de)(de)神經棘低,而(er)且分叉。盤足(zu)龍的(de)(de)(de)(de)(de)肩(jian)帶很(hen)發達(da),肩(jian)臼窩很(hen)淺,中部形(xing)(xing)成一(yi)個(ge)斜面,后肢(zhi)較短,所以古生(sheng)物學(xue)家推測(ce)盤足(zu)龍的(de)(de)(de)(de)(de)前肢(zhi)很(hen)可(ke)能(neng)很(hen)發達(da);因(yin)為前肢(zhi)很(hen)長(chang),所以盤足(zu)龍不用把脖(bo)子抬得太高就可(ke)以吃(chi)到高處的(de)(de)(de)(de)(de)樹葉。
巨(ju)龍(long)(long)(long)形類(lei)(Titanosauriformes)恐龍(long)(long)(long)屬于蜥(xi)腳次(ci)亞目(Sauropoda)真蜥(xi)腳類(lei)(Eusauropoda)新(xin)蜥(xi)腳類(lei)(Neosauropoda)大鼻龍(long)(long)(long)類(lei)(Macronaria),和(he)圓頂龍(long)(long)(long)科(Camarasauridae)是姐妹群;巨(ju)龍(long)(long)(long)形類(lei)主(zhu)要包括腕龍(long)(long)(long)科(Brachiosauridae),盤足龍(long)(long)(long)科(Euhelopodidae)和(he)巨(ju)龍(long)(long)(long)類(lei)(Titanosauria)。巨(ju)龍(long)(long)(long)形類(lei)包括很多著名的(de)(de)(de)恐龍(long)(long)(long),比(bi)如坦(tan)桑(sang)尼(ni)亞上(shang)侏(zhu)羅統(tong)的(de)(de)(de)坦(tan)達古魯層(ceng)(Tendaguru Beds)地層(ceng)發現的(de)(de)(de)布(bu)氏腕龍(long)(long)(long)(Brachiosaurus (Giraffatitan) brancai or Giraffatitan brancai),我國山東省(sheng)上(shang)侏(zhu)羅統(tong)或(huo)下白堊(e)統(tong)的(de)(de)(de)蒙陰組(zu)(Meng-Yin Formation)地層(ceng)發現的(de)(de)(de)師氏盤足龍(long)(long)(long)(Euhelopus zdanskyi),阿(a)(a)根廷(ting)(ting)下白堊(e)統(tong)的(de)(de)(de)里(li)約利邁河組(zu)(Rio Limay Formation)地層(ceng)發現的(de)(de)(de)阿(a)(a)根廷(ting)(ting)龍(long)(long)(long)(Argentinosaurus),我國河南省(sheng)的(de)(de)(de)蟒(mang)川組(zu)(Mangchuan Formation)地層(ceng)發現的(de)(de)(de)汝陽(yang)黃河巨(ju)龍(long)(long)(long)(Huanghetitan ruyangensis)等。
巨龍形類(lei)的(de)特征包(bao)括沒有(you)前(qian)(qian)(qian)(qian)(qian)眶前(qian)(qian)(qian)(qian)(qian)孔;上頜(he)骨(gu)(gu)(gu)(gu)與前(qian)(qian)(qian)(qian)(qian)上頜(he)骨(gu)(gu)(gu)(gu)的(de)接(jie)觸面(mian)(mian)呈棒狀;齒骨(gu)(gu)(gu)(gu)的(de)多面(mian)(mian)陡峭。前(qian)(qian)(qian)(qian)(qian)棘突板(ban)(ban);頸椎(zhui)普遍被加長;背(bei)椎(zhui)氣腔化;背(bei)椎(zhui)和前(qian)(qian)(qian)(qian)(qian)部(bu)(bu)尾椎(zhui)神(shen)經弓(gong)只比椎(zhui)體(ti)略(lve)窄;前(qian)(qian)(qian)(qian)(qian)段(duan)的(de)背(bei)肋寬廣,呈板(ban)(ban)狀;中(zhong)后(hou)部(bu)(bu)尾椎(zhui)神(shen)經弓(gong)位于(yu)椎(zhui)體(ti)的(de)前(qian)(qian)(qian)(qian)(qian)面(mian)(mian);脈(mo)弧(hu)不分(fen)叉(cha);中(zhong)后(hou)部(bu)(bu)脈(mo)弧(hu)向后(hou)彎曲。肩臼窩(wo)向前(qian)(qian)(qian)(qian)(qian)腹側(ce)和內側(ce)傾斜;掌骨(gu)(gu)(gu)(gu)長超過脛骨(gu)(gu)(gu)(gu)的(de)百分(fen)之四十五以(yi)上;第一指爪(zhua)縮(suo)小或消失。股骨(gu)(gu)(gu)(gu)骨(gu)(gu)(gu)(gu)干近端三分(fen)之一處側(ce)向突出翻轉(zhuan);恥骨(gu)(gu)(gu)(gu)的(de)坐骨(gu)(gu)(gu)(gu)關節面(mian)(mian)較為(wei)縱深;恥骨(gu)(gu)(gu)(gu)突前(qian)(qian)(qian)(qian)(qian)的(de)腸骨(gu)(gu)(gu)(gu)板(ban)(ban)明(ming)顯(xian)高(gao)于(yu)其后(hou)的(de)腸骨(gu)(gu)(gu)(gu)板(ban)(ban)等(Wilson, 2002,Upchurch et al., 2004,Wilson, 2005,Mo et al., 2006)。
巨(ju)龍形(xing)類(lei)(lei)早出現在(zai)中侏羅(luo)世(shi)或(huo)晚侏羅(luo)世(shi),不過進(jin)入白(bai)堊紀(ji)(ji)后才變(bian)得十分(fen)繁盛,而(er)且(qie)是白(bai)堊紀(ji)(ji),特(te)別是晚白(bai)堊世(shi)主要的(de)蜥(xi)腳類(lei)(lei)恐龍。近(jin)來(lai)對南方岡(gang)瓦(wa)納大陸(lu)和我(wo)國發現的(de)巨(ju)龍形(xing)類(lei)(lei),特(te)別是一(yi)些(xie)巨(ju)龍類(lei)(lei)的(de)研究徹底掃除了比如“蜥(xi)腳類(lei)(lei)進(jin)入白(bai)堊紀(ji)(ji)后逐漸被鳥臀類(lei)(lei)取代并(bing)(bing)滅絕(jue)”等人們(men)過去對蜥(xi)腳類(lei)(lei)的(de)一(yi)系列錯誤(wu)認識,我(wo)們(men)現在(zai)知道不僅僅是巨(ju)龍形(xing)類(lei)(lei),在(zai)白(bai)堊紀(ji)(ji)還有雷巴齊(qi)斯(si)龍科(Rebbachisauridae)和叉背龍科(Dicraeosauridae)等很多其他的(de)蜥(xi)腳類(lei)(lei)恐龍,而(er)且(qie)它(ta)們(men)一(yi)直是南方岡(gang)瓦(wa)納大陸(lu)主要的(de)植食動物,并(bing)(bing)且(qie)其中一(yi)部分(fen)甚至可能侵入或(huo)者(zhe)起源于北方勞亞大陸(lu),和鳥臀類(lei)(lei)競(jing)爭。國外的(de)白(bai)堊紀(ji)(ji)的(de)巨(ju)龍形(xing)類(lei)(lei)主要分(fen)布在(zai)南方岡(gang)瓦(wa)納大陸(lu)的(de)南美(mei)洲,印(yin)度,非洲北部,馬(ma)達加斯(si)加,澳大利(li)亞和南歐,也有部分(fen)化石(shi)發現于北美(mei)洲和俄(e)羅(luo)斯(si)西伯利(li)亞地區南部。
我(wo)(wo)國(guo)系(xi)(xi)統(tong)的(de)(de)(de)進行巨(ju)龍形類(lei)研(yan)究起(qi)步(bu)較(jiao)晚,一方面(mian)是(shi)因為早(zao)期(qi)發現的(de)(de)(de)材(cai)(cai)料較(jiao)少(shao),另一方面(mian)是(shi)過去(qu)國(guo)內的(de)(de)(de)分類(lei)體(ti)系(xi)(xi)和材(cai)(cai)料更新受到新研(yan)究的(de)(de)(de)影響(xiang)比較(jiao)小,所以一些(xie)錯誤的(de)(de)(de)觀(guan)點和陳舊(jiu)的(de)(de)(de)認識沒(mei)有得到及時更新;但(dan)是(shi)最近在我(wo)(wo)國(guo)的(de)(de)(de)吉林省(sheng)(sheng),遼寧省(sheng)(sheng),山西省(sheng)(sheng),河南省(sheng)(sheng),甘(gan)肅省(sheng)(sheng),廣(guang)西省(sheng)(sheng)和浙江(jiang)省(sheng)(sheng)等地發現了一些(xie)巨(ju)龍形類(lei)的(de)(de)(de)材(cai)(cai)料,雖然(ran)這些(xie)材(cai)(cai)料也都大多并不完整,但(dan)是(shi)在一定程(cheng)度上是(shi)我(wo)(wo)們對了解巨(ju)龍形類(lei)的(de)(de)(de)起(qi)源(yuan)和早(zao)期(qi)演化以及白堊紀時期(qi)東(dong)亞的(de)(de)(de)生態環境(jing)的(de)(de)(de)重要的(de)(de)(de)材(cai)(cai)料。