Romer將原來Wiman所(suo)(suo)命(ming)(ming)名(ming)(ming)的(de)(de)Helopus重(zhong)新在(zai)1956年命(ming)(ming)名(ming)(ming)為盤(pan)足(zu)(zu)龍(long),同(tong)時(shi)提(ti)出(chu)一(yi)個盤(pan)族(zu)類的(de)(de)新亞科。到(dao)(dao)(dao)1934年,楊(yang)鐘健(jian)協同(tong)卞美年考察(cha)這個化石點,又采集一(yi)些破碎不全的(de)(de)骨骼,大多(duo)屬于盤(pan)足(zu)(zu)龍(long)的(de)(de)一(yi)部分,而(er)少部分則經(jing)過監(jian)定屬于獸腳(jiao)類恐龍(long)以及劍龍(long)類的(de)(de)背部突棘(ji)。盤(pan)足(zu)(zu)龍(long)的(de)(de)頭骨一(yi)般與圓頂龍(long)相比較(jiao),但較(jiao)為低(di)(di)平。它具有(you)極(ji)為碩長(chang)的(de)(de)脖(bo)子。總共(gong)有(you)17個頸(jing)椎(zhui)。頸(jing)椎(zhui)體的(de)(de)神經(jing)棘(ji)很低(di)(di),在(zai)肩部附(fu)近(jin)開叉很寬廣。據(ju)推估這具師氏盤(pan)足(zu)(zu)龍(long)體長(chang)達到(dao)(dao)(dao)10到(dao)(dao)(dao)11公尺,是(shi)中(zhong)國所(suo)(suo)正式命(ming)(ming)名(ming)(ming)的(de)(de)第一(yi)只(zhi)蜥(xi)腳(jiao)類恐龍(long)。
我(wo)(wo)國(guo)(guo)發(fa)現的(de)早的(de)巨龍形類(lei)(lei)恐(kong)(kong)龍是(shi)師氏盤足龍(Euhelopus zdanskyi),同時這還(huan)是(shi)在(zai)我(wo)(wo)國(guo)(guo)發(fa)現的(de)第一只(zhi)蜥(xi)腳類(lei)(lei)恐(kong)(kong)龍,早在(zai)1921年(nian)奧(ao)地利古(gu)生物學家師丹(dan)斯基(Otto Zdansky,1894—1988)在(zai)瑞典(dian)烏普薩(sa)拉大學(Uppsala University)的(de)古(gu)生物學家維曼(Prof Carl Wiman,1867—1944)的(de)建(jian)議下前往(wang)中(zhong)國(guo)(guo),在(zai)中(zhong)國(guo)(guo)他有許多重大的(de)發(fa)現,比如:著名的(de)古(gu)中(zhong)華虎(Panthera palaeosinensis or "Felis (Panthera)" palaeosinensis),北京猿人(Homo erectus pekinensis or "Sinanthropus pekinensis")以及三趾馬動物群等都(dou)是(shi)他發(fa)現的(de);在(zai)1922年(nian)到1923年(nian)師丹(dan)斯基和我(wo)(wo)國(guo)(guo)地質學家譚錫疇(chou)在(zai)山東省蒙陰縣寧家溝的(de)上侏羅統或下白堊統的(de)蒙陰組(Meng-Yin Formation)地層發(fa)現并(bing)挖掘(jue)了一些恐(kong)(kong)龍化石,其中(zhong)包括獸腳類(lei)(lei)牙(ya)齒和劍龍類(lei)(lei)的(de)骨(gu)(gu)板(ban),同時還(huan)有兩具不完(wan)整的(de)蜥(xi)腳類(lei)(lei)恐(kong)(kong)龍骨(gu)(gu)骼(ge),師丹(dan)斯基把自己(ji)發(fa)現的(de)大部(bu)分化石都(dou)送(song)到瑞典(dian)的(de)烏普薩(sa)拉大學由維曼研究(jiu),這兩具蜥(xi)腳類(lei)(lei)恐(kong)(kong)龍骨(gu)(gu)骼(ge)也是(shi)一樣。
維曼在仔(zi)細(xi)研究了(le)(le)師(shi)丹(dan)(dan)斯(si)基送來化石(shi)后(hou)(hou)將它們命名(ming)(ming)(ming)為(wei)(wei)(wei)"Helopus" zdanskyi,屬(shu)(shu)名(ming)(ming)(ming)“Helopus”是希臘(la)語(yu)“濕(shi)地(di)的(de)(de)腳”的(de)(de)意思(si),而種名(ming)(ming)(ming)“zdanskyi”是紀念(nian)師(shi)丹(dan)(dan)斯(si)基發現(xian)了(le)(le)這(zhe)種恐龍(long)(long);不過(guo)在1956年(nian)羅默(Alfred Sherwood Romer,1894—1973)發現(xian)一屬(shu)(shu)鳥(niao)類已經先(xian)行(xing)占有(you)(you)了(le)(le)“Helopus”這(zhe)個屬(shu)(shu)名(ming)(ming)(ming),所后(hou)(hou)就被"Helopus" zdanskyi重新(xin)命名(ming)(ming)(ming)為(wei)(wei)(wei)師(shi)氏盤(pan)(pan)(pan)足(zu)龍(long)(long)(Euhelopus zdanskyi),屬(shu)(shu)名(ming)(ming)(ming)盤(pan)(pan)(pan)足(zu)龍(long)(long)(Euhelopus)的(de)(de)意思(si)是“出色的(de)(de)濕(shi)地(di)的(de)(de)腳”,我(wo)國的(de)(de)古生物學(xue)家因為(wei)(wei)(wei)過(guo)去(qu)認為(wei)(wei)(wei)蜥(xi)腳類恐龍(long)(long)的(de)(de)足(zu)部的(de)(de)只(zhi)顧和趾骨是散(san)開,像盤(pan)(pan)(pan)子一樣,所以翻譯(yi)為(wei)(wei)(wei)“盤(pan)(pan)(pan)足(zu)龍(long)(long)”;同時羅默認為(wei)(wei)(wei)盤(pan)(pan)(pan)足(zu)龍(long)(long)的(de)(de)特(te)征(zheng)獨特(te),所以建立了(le)(le)一個新(xin)的(de)(de)亞(ya)科(ke)(ke)(ke)——盤(pan)(pan)(pan)足(zu)龍(long)(long)亞(ya)科(ke)(ke)(ke)(Euhelopodinae),當(dang)時歸入(ru)(ru)腕龍(long)(long)科(ke)(ke)(ke)(Brachiosauridae),后(hou)(hou)來也有(you)(you)人把(ba)盤(pan)(pan)(pan)足(zu)龍(long)(long)亞(ya)科(ke)(ke)(ke)歸入(ru)(ru)圓頂龍(long)(long)科(ke)(ke)(ke)(Camarasauridae)或者馬門溪(xi)龍(long)(long)科(ke)(ke)(ke)(Mamenchisauridae)的(de)(de),我(wo)國一些老一輩的(de)(de)古生物學(xue)家目(mu)前多同意盤(pan)(pan)(pan)足(zu)龍(long)(long)亞(ya)科(ke)(ke)(ke)歸入(ru)(ru)圓頂龍(long)(long)科(ke)(ke)(ke);劍(jian)橋大(da)學(xue)的(de)(de)阿普徹奇(Paul Publication Upchurch)在1995年(nian)進一步提出了(le)(le)盤(pan)(pan)(pan)足(zu)龍(long)(long)科(ke)(ke)(ke)(Euhelopodidae),并認為(wei)(wei)(wei)在中(zhong)國中(zhong)侏(zhu)羅統(tong)到白堊系發現(xian)的(de)(de)大(da)量的(de)(de)長頸(jing)椎蜥(xi)腳類恐龍(long)(long)都屬(shu)(shu)于這(zhe)一支系(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(long)(long)(long)(long)的頸椎神經弓和(he)肩(jian)帶結(jie)構十(shi)分進步,所以應該屬于(yu)巨(ju)龍(long)(long)(long)(long)形類;而峨嵋龍(long)(long)(long)(long)(Omeisaurus)的頭骨,掌骨,腰(yao)帶和(he)距(ju)骨的特征過(guo)于(yu)原始,并(bing)不(bu)屬于(yu)新蜥腳(jiao)類恐(kong)龍(long)(long)(long)(long)(Neosauropod),和(he)盤足(zu)龍(long)(long)(long)(long)關系(xi)很(hen)遠,目前很(hen)多學者都同意這種說法(Wilson et Sereno, 1998,1999,2000, Wilson, 2002,Ksepka et Norell, 2006),所以我們在這里也(ye)把盤足(zu)龍(long)(long)(long)(long)作為(wei)巨(ju)龍(long)(long)(long)(long)形類恐(kong)龍(long)(long)(long)(long)進行描述。
因為(wei)盤(pan)(pan)足(zu)(zu)龍(long)(long)(long)的(de)(de)(de)(de)(de)化石只發現了(le)頭骨,大部(bu)分(fen)頸椎(zhui),肩帶(dai),前肢,背椎(zhui),腰帶(dai)和后肢等(deng),所(suo)以我(wo)們對它的(de)(de)(de)(de)(de)了(le)解也(ye)主要是這些,至于(yu)尾巴的(de)(de)(de)(de)(de)形(xing)態只能推測(ce)。盤(pan)(pan)足(zu)(zu)龍(long)(long)(long)的(de)(de)(de)(de)(de)頭骨和圓(yuan)頂龍(long)(long)(long)的(de)(de)(de)(de)(de)比較(jiao)接近,都屬于(yu)比較(jiao)粗壯而(er)高的(de)(de)(de)(de)(de)類型,而(er)且(qie)鼻孔也(ye)很(hen)(hen)(hen)大,牙齒也(ye)都屬于(yu)粗壯的(de)(de)(de)(de)(de)勺形(xing)齒;但是盤(pan)(pan)足(zu)(zu)龍(long)(long)(long)的(de)(de)(de)(de)(de)頭骨比圓(yuan)頂龍(long)(long)(long)的(de)(de)(de)(de)(de)要長(chang)(chang)一些。盤(pan)(pan)足(zu)(zu)龍(long)(long)(long)的(de)(de)(de)(de)(de)頸椎(zhui)很(hen)(hen)(hen)長(chang)(chang),而(er)且(qie)數量很(hen)(hen)(hen)多(duo),有十七個(ge)(ge),估計(ji)長(chang)(chang)度(du)超過(guo)體(ti)長(chang)(chang)的(de)(de)(de)(de)(de)一半;后部(bu)頸椎(zhui)的(de)(de)(de)(de)(de)神經(jing)棘低,而(er)且(qie)分(fen)叉。盤(pan)(pan)足(zu)(zu)龍(long)(long)(long)的(de)(de)(de)(de)(de)肩帶(dai)很(hen)(hen)(hen)發達,肩臼窩很(hen)(hen)(hen)淺,中部(bu)形(xing)成一個(ge)(ge)斜面,后肢較(jiao)短,所(suo)以古(gu)生(sheng)物學家推測(ce)盤(pan)(pan)足(zu)(zu)龍(long)(long)(long)的(de)(de)(de)(de)(de)前肢很(hen)(hen)(hen)可能很(hen)(hen)(hen)發達;因為(wei)前肢很(hen)(hen)(hen)長(chang)(chang),所(suo)以盤(pan)(pan)足(zu)(zu)龍(long)(long)(long)不用把脖子抬得太高就可以吃(chi)到高處的(de)(de)(de)(de)(de)樹葉。
巨(ju)龍(long)(long)(long)形類(lei)(lei)(Titanosauriformes)恐龍(long)(long)(long)屬于(yu)蜥腳次亞目(Sauropoda)真蜥腳類(lei)(lei)(Eusauropoda)新蜥腳類(lei)(lei)(Neosauropoda)大鼻龍(long)(long)(long)類(lei)(lei)(Macronaria),和圓頂龍(long)(long)(long)科(Camarasauridae)是姐妹群;巨(ju)龍(long)(long)(long)形類(lei)(lei)主(zhu)要包括腕龍(long)(long)(long)科(Brachiosauridae),盤(pan)足(zu)龍(long)(long)(long)科(Euhelopodidae)和巨(ju)龍(long)(long)(long)類(lei)(lei)(Titanosauria)。巨(ju)龍(long)(long)(long)形類(lei)(lei)包括很多(duo)著(zhu)名的(de)恐龍(long)(long)(long),比(bi)如坦桑尼(ni)亞上侏羅統(tong)的(de)坦達(da)古魯層(ceng)(ceng)(Tendaguru Beds)地(di)層(ceng)(ceng)發現的(de)布氏腕龍(long)(long)(long)(Brachiosaurus (Giraffatitan) brancai or Giraffatitan brancai),我國山東省上侏羅統(tong)或下白堊(e)統(tong)的(de)蒙陰組(zu)(Meng-Yin Formation)地(di)層(ceng)(ceng)發現的(de)師氏盤(pan)足(zu)龍(long)(long)(long)(Euhelopus zdanskyi),阿根廷下白堊(e)統(tong)的(de)里約(yue)利邁河組(zu)(Rio Limay Formation)地(di)層(ceng)(ceng)發現的(de)阿根廷龍(long)(long)(long)(Argentinosaurus),我國河南省的(de)蟒川組(zu)(Mangchuan Formation)地(di)層(ceng)(ceng)發現的(de)汝陽黃河巨(ju)龍(long)(long)(long)(Huanghetitan ruyangensis)等。
巨(ju)龍形類的(de)(de)特征包(bao)括(kuo)沒有(you)前(qian)眶前(qian)孔;上(shang)頜(he)骨(gu)(gu)(gu)與前(qian)上(shang)頜(he)骨(gu)(gu)(gu)的(de)(de)接觸面(mian)(mian)呈棒狀;齒骨(gu)(gu)(gu)的(de)(de)多(duo)面(mian)(mian)陡(dou)峭(qiao)。前(qian)棘突(tu)(tu)板;頸椎(zhui)普遍被加長;背(bei)椎(zhui)氣(qi)腔(qiang)化;背(bei)椎(zhui)和(he)前(qian)部尾(wei)椎(zhui)神(shen)經弓只比椎(zhui)體(ti)略窄;前(qian)段的(de)(de)背(bei)肋寬廣,呈板狀;中后(hou)部尾(wei)椎(zhui)神(shen)經弓位于椎(zhui)體(ti)的(de)(de)前(qian)面(mian)(mian);脈弧不分叉;中后(hou)部脈弧向(xiang)后(hou)彎(wan)曲。肩臼窩向(xiang)前(qian)腹側和(he)內側傾斜;掌骨(gu)(gu)(gu)長超過脛骨(gu)(gu)(gu)的(de)(de)百分之四十五以上(shang);第一指爪縮小或消失(shi)。股骨(gu)(gu)(gu)骨(gu)(gu)(gu)干近端三分之一處側向(xiang)突(tu)(tu)出翻轉(zhuan);恥(chi)骨(gu)(gu)(gu)的(de)(de)坐(zuo)骨(gu)(gu)(gu)關節面(mian)(mian)較(jiao)為縱深;恥(chi)骨(gu)(gu)(gu)突(tu)(tu)前(qian)的(de)(de)腸(chang)骨(gu)(gu)(gu)板明(ming)顯(xian)高于其后(hou)的(de)(de)腸(chang)骨(gu)(gu)(gu)板等(Wilson, 2002,Upchurch et al., 2004,Wilson, 2005,Mo et al., 2006)。
巨龍(long)形類(lei)(lei)(lei)早出(chu)現(xian)(xian)(xian)在(zai)中侏羅(luo)世(shi)或晚侏羅(luo)世(shi),不(bu)過(guo)進(jin)(jin)入(ru)白(bai)(bai)堊(e)紀后(hou)(hou)才變得十分(fen)繁盛(sheng),而且(qie)是(shi)白(bai)(bai)堊(e)紀,特(te)別是(shi)晚白(bai)(bai)堊(e)世(shi)主要(yao)的(de)蜥(xi)腳(jiao)類(lei)(lei)(lei)恐龍(long)。近(jin)來對南(nan)方岡(gang)瓦納(na)(na)大陸(lu)和我(wo)(wo)國發現(xian)(xian)(xian)的(de)巨龍(long)形類(lei)(lei)(lei),特(te)別是(shi)一些巨龍(long)類(lei)(lei)(lei)的(de)研(yan)究徹底掃除了(le)比如“蜥(xi)腳(jiao)類(lei)(lei)(lei)進(jin)(jin)入(ru)白(bai)(bai)堊(e)紀后(hou)(hou)逐漸被鳥臀類(lei)(lei)(lei)取代(dai)并滅絕”等人(ren)們(men)(men)過(guo)去對蜥(xi)腳(jiao)類(lei)(lei)(lei)的(de)一系(xi)列錯誤認(ren)識,我(wo)(wo)們(men)(men)現(xian)(xian)(xian)在(zai)知道(dao)不(bu)僅(jin)僅(jin)是(shi)巨龍(long)形類(lei)(lei)(lei),在(zai)白(bai)(bai)堊(e)紀還(huan)有雷巴齊斯龍(long)科(Rebbachisauridae)和叉背龍(long)科(Dicraeosauridae)等很多其他的(de)蜥(xi)腳(jiao)類(lei)(lei)(lei)恐龍(long),而且(qie)它們(men)(men)一直是(shi)南(nan)方岡(gang)瓦納(na)(na)大陸(lu)主要(yao)的(de)植食動物,并且(qie)其中一部(bu)分(fen)甚至可能(neng)侵入(ru)或者起源于(yu)北(bei)方勞亞(ya)大陸(lu),和鳥臀類(lei)(lei)(lei)競爭。國外(wai)的(de)白(bai)(bai)堊(e)紀的(de)巨龍(long)形類(lei)(lei)(lei)主要(yao)分(fen)布(bu)在(zai)南(nan)方岡(gang)瓦納(na)(na)大陸(lu)的(de)南(nan)美(mei)洲(zhou),印度,非(fei)洲(zhou)北(bei)部(bu),馬(ma)達加斯加,澳(ao)大利亞(ya)和南(nan)歐,也有部(bu)分(fen)化(hua)石(shi)發現(xian)(xian)(xian)于(yu)北(bei)美(mei)洲(zhou)和俄(e)羅(luo)斯西伯(bo)利亞(ya)地區南(nan)部(bu)。
我國(guo)系(xi)統的(de)(de)(de)(de)進行巨龍形類(lei)研究起步較(jiao)晚,一方(fang)面是(shi)因為(wei)早(zao)期發現的(de)(de)(de)(de)材(cai)料較(jiao)少,另一方(fang)面是(shi)過去國(guo)內(nei)的(de)(de)(de)(de)分(fen)類(lei)體系(xi)和材(cai)料更新受到新研究的(de)(de)(de)(de)影響(xiang)比較(jiao)小,所以一些錯誤的(de)(de)(de)(de)觀點(dian)和陳舊的(de)(de)(de)(de)認(ren)識沒有得到及時更新;但是(shi)最近在我國(guo)的(de)(de)(de)(de)吉林省(sheng),遼寧省(sheng),山西省(sheng),河(he)南省(sheng),甘肅(su)省(sheng),廣西省(sheng)和浙(zhe)江省(sheng)等(deng)地發現了一些巨龍形類(lei)的(de)(de)(de)(de)材(cai)料,雖然(ran)這些材(cai)料也都大多并不完整,但是(shi)在一定程度上是(shi)我們(men)對了解巨龍形類(lei)的(de)(de)(de)(de)起源和早(zao)期演化(hua)以及白堊紀(ji)時期東亞的(de)(de)(de)(de)生態(tai)環境的(de)(de)(de)(de)重要的(de)(de)(de)(de)材(cai)料。