Romer將(jiang)原來Wiman所命名(ming)(ming)的(de)(de)Helopus重新在1956年命名(ming)(ming)為(wei)盤(pan)(pan)足(zu)龍,同(tong)時提出一(yi)個(ge)盤(pan)(pan)族類(lei)(lei)的(de)(de)新亞科。到(dao)1934年,楊鐘健協同(tong)卞美年考察這個(ge)化(hua)石點,又采集一(yi)些破碎不全的(de)(de)骨(gu)骼,大多屬于盤(pan)(pan)足(zu)龍的(de)(de)一(yi)部(bu)分(fen),而少部(bu)分(fen)則(ze)經過監定(ding)屬于獸(shou)腳類(lei)(lei)恐(kong)龍以及劍龍類(lei)(lei)的(de)(de)背(bei)部(bu)突棘。盤(pan)(pan)足(zu)龍的(de)(de)頭(tou)骨(gu)一(yi)般與圓頂龍相比較,但較為(wei)低(di)平。它具(ju)有極為(wei)碩(shuo)長(chang)的(de)(de)脖子。總共有17個(ge)頸椎。頸椎體的(de)(de)神經棘很低(di),在肩部(bu)附近開叉很寬廣。據推估這具(ju)師氏盤(pan)(pan)足(zu)龍體長(chang)達到(dao)10到(dao)11公尺,是中國所正(zheng)式命名(ming)(ming)的(de)(de)第一(yi)只蜥腳類(lei)(lei)恐(kong)龍。
我(wo)國(guo)(guo)發(fa)現(xian)的(de)(de)早的(de)(de)巨龍(long)形類(lei)恐龍(long)是師(shi)氏盤足龍(long)(Euhelopus zdanskyi),同(tong)時(shi)這還(huan)是在(zai)我(wo)國(guo)(guo)發(fa)現(xian)的(de)(de)第(di)一只蜥腳類(lei)恐龍(long),早在(zai)1921年奧地利古生物(wu)(wu)學(xue)(xue)家師(shi)丹斯基(ji)(Otto Zdansky,1894—1988)在(zai)瑞典烏普(pu)薩(sa)拉(la)大(da)學(xue)(xue)(Uppsala University)的(de)(de)古生物(wu)(wu)學(xue)(xue)家維(wei)曼(Prof Carl Wiman,1867—1944)的(de)(de)建議下前(qian)往中國(guo)(guo),在(zai)中國(guo)(guo)他(ta)有許多重大(da)的(de)(de)發(fa)現(xian),比如:著名的(de)(de)古中華(hua)虎(Panthera palaeosinensis or "Felis (Panthera)" palaeosinensis),北京猿人(Homo erectus pekinensis or "Sinanthropus pekinensis")以及三(san)趾馬動物(wu)(wu)群等(deng)都是他(ta)發(fa)現(xian)的(de)(de);在(zai)1922年到(dao)1923年師(shi)丹斯基(ji)和我(wo)國(guo)(guo)地質(zhi)學(xue)(xue)家譚錫疇在(zai)山(shan)東省蒙陰縣寧家溝的(de)(de)上侏(zhu)羅(luo)統(tong)或(huo)下白堊(e)統(tong)的(de)(de)蒙陰組(Meng-Yin Formation)地層發(fa)現(xian)并(bing)挖掘了一些恐龍(long)化(hua)(hua)石,其(qi)中包(bao)括獸腳類(lei)牙(ya)齒和劍龍(long)類(lei)的(de)(de)骨板,同(tong)時(shi)還(huan)有兩(liang)具(ju)不完(wan)整的(de)(de)蜥腳類(lei)恐龍(long)骨骼(ge),師(shi)丹斯基(ji)把自己發(fa)現(xian)的(de)(de)大(da)部(bu)分(fen)化(hua)(hua)石都送到(dao)瑞典的(de)(de)烏普(pu)薩(sa)拉(la)大(da)學(xue)(xue)由維(wei)曼研(yan)究(jiu),這兩(liang)具(ju)蜥腳類(lei)恐龍(long)骨骼(ge)也是一樣。
維曼(man)在(zai)仔細研究了(le)師(shi)丹斯基送(song)來化石后(hou)(hou)(hou)將它(ta)們命名(ming)為(wei)"Helopus" zdanskyi,屬(shu)(shu)名(ming)“Helopus”是希臘語“濕地的(de)(de)腳”的(de)(de)意(yi)思(si),而種名(ming)“zdanskyi”是紀念師(shi)丹斯基發現(xian)了(le)這(zhe)種恐龍(long)(long)(long)(long);不過在(zai)1956年(nian)(nian)羅默(mo)(Alfred Sherwood Romer,1894—1973)發現(xian)一(yi)屬(shu)(shu)鳥類已經先行(xing)占有(you)了(le)“Helopus”這(zhe)個屬(shu)(shu)名(ming),所(suo)后(hou)(hou)(hou)就被"Helopus" zdanskyi重新(xin)命名(ming)為(wei)師(shi)氏盤(pan)足(zu)(zu)龍(long)(long)(long)(long)(Euhelopus zdanskyi),屬(shu)(shu)名(ming)盤(pan)足(zu)(zu)龍(long)(long)(long)(long)(Euhelopus)的(de)(de)意(yi)思(si)是“出(chu)色的(de)(de)濕地的(de)(de)腳”,我國的(de)(de)古生物(wu)學(xue)(xue)家(jia)因為(wei)過去認(ren)為(wei)蜥(xi)腳類恐龍(long)(long)(long)(long)的(de)(de)足(zu)(zu)部的(de)(de)只顧和趾骨(gu)是散開(kai),像盤(pan)子一(yi)樣,所(suo)以翻(fan)譯為(wei)“盤(pan)足(zu)(zu)龍(long)(long)(long)(long)”;同(tong)時羅默(mo)認(ren)為(wei)盤(pan)足(zu)(zu)龍(long)(long)(long)(long)的(de)(de)特征獨特,所(suo)以建立(li)了(le)一(yi)個新(xin)的(de)(de)亞科(ke)(ke)——盤(pan)足(zu)(zu)龍(long)(long)(long)(long)亞科(ke)(ke)(Euhelopodinae),當時歸入腕(wan)龍(long)(long)(long)(long)科(ke)(ke)(Brachiosauridae),后(hou)(hou)(hou)來也有(you)人把盤(pan)足(zu)(zu)龍(long)(long)(long)(long)亞科(ke)(ke)歸入圓頂龍(long)(long)(long)(long)科(ke)(ke)(Camarasauridae)或者馬(ma)門溪龍(long)(long)(long)(long)科(ke)(ke)(Mamenchisauridae)的(de)(de),我國一(yi)些(xie)老一(yi)輩的(de)(de)古生物(wu)學(xue)(xue)家(jia)目前多同(tong)意(yi)盤(pan)足(zu)(zu)龍(long)(long)(long)(long)亞科(ke)(ke)歸入圓頂龍(long)(long)(long)(long)科(ke)(ke);劍(jian)橋大學(xue)(xue)的(de)(de)阿普徹奇(qi)(Paul Publication Upchurch)在(zai)1995年(nian)(nian)進(jin)一(yi)步提出(chu)了(le)盤(pan)足(zu)(zu)龍(long)(long)(long)(long)科(ke)(ke)(Euhelopodidae),并(bing)認(ren)為(wei)在(zai)中國中侏羅統到白堊系(xi)發現(xian)的(de)(de)大量的(de)(de)長頸椎蜥(xi)腳類恐龍(long)(long)(long)(long)都屬(shu)(shu)于(yu)這(zhe)一(yi)支系(xi)(Upchurch, 1995, 1998)。
但是威爾(er)遜(Jeff Wilson)和(he)塞里諾(Paul Sereno)等人(ren)認為盤足龍的(de)(de)頸椎神經弓和(he)肩帶(dai)結構十(shi)分進步,所以(yi)應(ying)該屬(shu)于(yu)巨龍形類;而峨嵋龍(Omeisaurus)的(de)(de)頭骨,掌骨,腰(yao)帶(dai)和(he)距骨的(de)(de)特征過于(yu)原(yuan)始,并不屬(shu)于(yu)新蜥(xi)腳類恐龍(Neosauropod),和(he)盤足龍關系很遠(yuan),目前(qian)很多學者都同意這(zhe)種說法(Wilson et Sereno, 1998,1999,2000, Wilson, 2002,Ksepka et Norell, 2006),所以(yi)我們在(zai)這(zhe)里也把(ba)盤足龍作為巨龍形類恐龍進行描(miao)述(shu)。
因為(wei)盤(pan)足(zu)龍(long)(long)(long)的(de)(de)(de)化石只發(fa)(fa)現了(le)頭骨(gu),大(da)部分(fen)頸椎,肩(jian)帶,前肢(zhi),背椎,腰帶和后肢(zhi)等,所(suo)(suo)以(yi)(yi)我們(men)對它(ta)的(de)(de)(de)了(le)解也(ye)主(zhu)要是這些,至于(yu)尾巴的(de)(de)(de)形(xing)態只能(neng)推測。盤(pan)足(zu)龍(long)(long)(long)的(de)(de)(de)頭骨(gu)和圓頂龍(long)(long)(long)的(de)(de)(de)比(bi)較(jiao)接近,都屬(shu)于(yu)比(bi)較(jiao)粗壯(zhuang)而(er)高的(de)(de)(de)類型(xing),而(er)且(qie)鼻孔(kong)也(ye)很(hen)(hen)大(da),牙(ya)齒(chi)也(ye)都屬(shu)于(yu)粗壯(zhuang)的(de)(de)(de)勺形(xing)齒(chi);但是盤(pan)足(zu)龍(long)(long)(long)的(de)(de)(de)頭骨(gu)比(bi)圓頂龍(long)(long)(long)的(de)(de)(de)要長(chang)一些。盤(pan)足(zu)龍(long)(long)(long)的(de)(de)(de)頸椎很(hen)(hen)長(chang),而(er)且(qie)數量(liang)很(hen)(hen)多,有十七(qi)個,估計長(chang)度超過體長(chang)的(de)(de)(de)一半;后部頸椎的(de)(de)(de)神經棘低,而(er)且(qie)分(fen)叉。盤(pan)足(zu)龍(long)(long)(long)的(de)(de)(de)肩(jian)帶很(hen)(hen)發(fa)(fa)達,肩(jian)臼(jiu)窩很(hen)(hen)淺,中部形(xing)成一個斜面,后肢(zhi)較(jiao)短,所(suo)(suo)以(yi)(yi)古生物學家推測盤(pan)足(zu)龍(long)(long)(long)的(de)(de)(de)前肢(zhi)很(hen)(hen)可能(neng)很(hen)(hen)發(fa)(fa)達;因為(wei)前肢(zhi)很(hen)(hen)長(chang),所(suo)(suo)以(yi)(yi)盤(pan)足(zu)龍(long)(long)(long)不用(yong)把脖(bo)子抬得太高就可以(yi)(yi)吃到高處的(de)(de)(de)樹葉。
巨(ju)龍(long)(long)(long)形(xing)類(lei)(lei)(Titanosauriformes)恐(kong)龍(long)(long)(long)屬于蜥(xi)腳(jiao)次(ci)亞(ya)目(Sauropoda)真蜥(xi)腳(jiao)類(lei)(lei)(Eusauropoda)新蜥(xi)腳(jiao)類(lei)(lei)(Neosauropoda)大鼻龍(long)(long)(long)類(lei)(lei)(Macronaria),和圓頂龍(long)(long)(long)科(ke)(Camarasauridae)是姐妹(mei)群;巨(ju)龍(long)(long)(long)形(xing)類(lei)(lei)主要包(bao)括腕龍(long)(long)(long)科(ke)(Brachiosauridae),盤足龍(long)(long)(long)科(ke)(Euhelopodidae)和巨(ju)龍(long)(long)(long)類(lei)(lei)(Titanosauria)。巨(ju)龍(long)(long)(long)形(xing)類(lei)(lei)包(bao)括很(hen)多(duo)著名的(de)恐(kong)龍(long)(long)(long),比(bi)如(ru)坦(tan)桑尼亞(ya)上(shang)侏(zhu)(zhu)羅統(tong)的(de)坦(tan)達古(gu)魯(lu)層(ceng)(Tendaguru Beds)地(di)(di)層(ceng)發現的(de)布氏(shi)(shi)腕龍(long)(long)(long)(Brachiosaurus (Giraffatitan) brancai or Giraffatitan brancai),我國山東(dong)省上(shang)侏(zhu)(zhu)羅統(tong)或下(xia)白堊(e)統(tong)的(de)蒙(meng)陰組(zu)(zu)(Meng-Yin Formation)地(di)(di)層(ceng)發現的(de)師氏(shi)(shi)盤足龍(long)(long)(long)(Euhelopus zdanskyi),阿(a)根(gen)廷下(xia)白堊(e)統(tong)的(de)里約利邁河組(zu)(zu)(Rio Limay Formation)地(di)(di)層(ceng)發現的(de)阿(a)根(gen)廷龍(long)(long)(long)(Argentinosaurus),我國河南省的(de)蟒川(chuan)組(zu)(zu)(Mangchuan Formation)地(di)(di)層(ceng)發現的(de)汝陽黃(huang)河巨(ju)龍(long)(long)(long)(Huanghetitan ruyangensis)等。
巨(ju)龍形(xing)類的(de)(de)特征包括沒有前(qian)眶前(qian)孔;上(shang)頜(he)骨(gu)(gu)(gu)(gu)與前(qian)上(shang)頜(he)骨(gu)(gu)(gu)(gu)的(de)(de)接觸(chu)面(mian)呈(cheng)棒狀;齒骨(gu)(gu)(gu)(gu)的(de)(de)多面(mian)陡(dou)峭。前(qian)棘(ji)突(tu)板(ban);頸椎(zhui)普遍被加長;背(bei)椎(zhui)氣腔(qiang)化;背(bei)椎(zhui)和前(qian)部(bu)(bu)尾椎(zhui)神經弓(gong)只比椎(zhui)體(ti)略窄(zhai);前(qian)段(duan)的(de)(de)背(bei)肋寬廣(guang),呈(cheng)板(ban)狀;中(zhong)后部(bu)(bu)尾椎(zhui)神經弓(gong)位于(yu)椎(zhui)體(ti)的(de)(de)前(qian)面(mian);脈弧不(bu)分叉;中(zhong)后部(bu)(bu)脈弧向后彎(wan)曲。肩臼窩向前(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)(de)百分之(zhi)四十五以上(shang);第一(yi)指爪縮小或消失。股骨(gu)(gu)(gu)(gu)骨(gu)(gu)(gu)(gu)干(gan)近(jin)端(duan)三(san)分之(zhi)一(yi)處側(ce)向突(tu)出翻(fan)轉;恥(chi)(chi)骨(gu)(gu)(gu)(gu)的(de)(de)坐骨(gu)(gu)(gu)(gu)關節(jie)面(mian)較為縱(zong)深;恥(chi)(chi)骨(gu)(gu)(gu)(gu)突(tu)前(qian)的(de)(de)腸骨(gu)(gu)(gu)(gu)板(ban)明顯高于(yu)其后的(de)(de)腸骨(gu)(gu)(gu)(gu)板(ban)等(deng)(Wilson, 2002,Upchurch et al., 2004,Wilson, 2005,Mo et al., 2006)。
巨(ju)(ju)龍(long)(long)(long)形(xing)類(lei)早出現在中侏(zhu)羅世或晚侏(zhu)羅世,不過(guo)進(jin)入(ru)(ru)白(bai)堊(e)(e)紀(ji)(ji)后(hou)才變得十分(fen)繁盛(sheng),而且(qie)是(shi)(shi)白(bai)堊(e)(e)紀(ji)(ji),特(te)別是(shi)(shi)晚白(bai)堊(e)(e)世主要(yao)(yao)的(de)(de)蜥(xi)腳(jiao)類(lei)恐龍(long)(long)(long)。近來對南(nan)(nan)方岡(gang)瓦納大(da)(da)陸(lu)(lu)和(he)(he)我(wo)(wo)國(guo)發現的(de)(de)巨(ju)(ju)龍(long)(long)(long)形(xing)類(lei),特(te)別是(shi)(shi)一些巨(ju)(ju)龍(long)(long)(long)類(lei)的(de)(de)研究徹底掃除了比如“蜥(xi)腳(jiao)類(lei)進(jin)入(ru)(ru)白(bai)堊(e)(e)紀(ji)(ji)后(hou)逐(zhu)漸被鳥臀類(lei)取代并滅絕”等人們(men)過(guo)去(qu)對蜥(xi)腳(jiao)類(lei)的(de)(de)一系(xi)列錯誤認識,我(wo)(wo)們(men)現在知道不僅(jin)僅(jin)是(shi)(shi)巨(ju)(ju)龍(long)(long)(long)形(xing)類(lei),在白(bai)堊(e)(e)紀(ji)(ji)還有雷巴(ba)齊斯龍(long)(long)(long)科(Rebbachisauridae)和(he)(he)叉背(bei)龍(long)(long)(long)科(Dicraeosauridae)等很多其(qi)他的(de)(de)蜥(xi)腳(jiao)類(lei)恐龍(long)(long)(long),而且(qie)它們(men)一直(zhi)是(shi)(shi)南(nan)(nan)方岡(gang)瓦納大(da)(da)陸(lu)(lu)主要(yao)(yao)的(de)(de)植食(shi)動物(wu),并且(qie)其(qi)中一部分(fen)甚(shen)至可能侵入(ru)(ru)或者起(qi)源于(yu)北方勞(lao)亞(ya)(ya)大(da)(da)陸(lu)(lu),和(he)(he)鳥臀類(lei)競爭。國(guo)外的(de)(de)白(bai)堊(e)(e)紀(ji)(ji)的(de)(de)巨(ju)(ju)龍(long)(long)(long)形(xing)類(lei)主要(yao)(yao)分(fen)布在南(nan)(nan)方岡(gang)瓦納大(da)(da)陸(lu)(lu)的(de)(de)南(nan)(nan)美(mei)洲,印(yin)度(du),非洲北部,馬達(da)加斯加,澳大(da)(da)利亞(ya)(ya)和(he)(he)南(nan)(nan)歐(ou),也(ye)有部分(fen)化石發現于(yu)北美(mei)洲和(he)(he)俄羅斯西伯利亞(ya)(ya)地區(qu)南(nan)(nan)部。
我(wo)國系(xi)統的(de)進行(xing)巨(ju)(ju)龍形(xing)(xing)類研究起步(bu)較(jiao)晚,一(yi)方(fang)面是(shi)因為早(zao)期(qi)發現的(de)材(cai)料(liao)較(jiao)少,另(ling)一(yi)方(fang)面是(shi)過去國內的(de)分(fen)類體系(xi)和材(cai)料(liao)更(geng)新受到(dao)新研究的(de)影響(xiang)比較(jiao)小,所以一(yi)些(xie)(xie)錯誤的(de)觀點和陳舊(jiu)的(de)認識沒有得到(dao)及時更(geng)新;但是(shi)最近在(zai)我(wo)國的(de)吉林省(sheng)(sheng)(sheng),遼寧省(sheng)(sheng)(sheng),山西省(sheng)(sheng)(sheng),河(he)南省(sheng)(sheng)(sheng),甘肅(su)省(sheng)(sheng)(sheng),廣西省(sheng)(sheng)(sheng)和浙(zhe)江省(sheng)(sheng)(sheng)等地(di)發現了(le)一(yi)些(xie)(xie)巨(ju)(ju)龍形(xing)(xing)類的(de)材(cai)料(liao),雖然這些(xie)(xie)材(cai)料(liao)也都大多并(bing)不完整,但是(shi)在(zai)一(yi)定(ding)程度上是(shi)我(wo)們對了(le)解巨(ju)(ju)龍形(xing)(xing)類的(de)起源和早(zao)期(qi)演化以及白堊紀時期(qi)東亞的(de)生態環境的(de)重要的(de)材(cai)料(liao)。