四川广元侏罗纪甘氏四川龙(兽脚类:巨齿龙科)肱骨骨干的骨组织特点及其生物指示意义

The humeral diaphyseal histology and its biometric significance ofJurassic Szechuanosaurus campi(Theropoda,Megalosauridae)in Guangyuan City,Sichuan Province

甘氏四川龙是四川盆地重要的兽脚类,其层位为侏罗系沙溪庙组上段。本文甘氏四川龙产自四川广元河西化石点,中等个体,体长5 m,选取了左侧肱骨骨干,制取横切面的化石薄片,在偏光显微镜下观察其骨组织显微结构特征,表现为:(1)甘氏四川龙的肱骨横截面上,由外到内可依次观察骨外膜骨、纤维板层骨(纤层骨)、骨骼重建区、骨内膜骨和髓腔。(2)薄片最外侧具有灰黑色絮状结构,可能为骨外膜骨的纤维层,其内不发育脉管,骨外膜骨的内层较薄,脉管和骨陷窝均较少,且排列不规则;纤层骨的厚度较大,其上发育大量的脉管,脉管以线状、丛状为主,有少量圆形和椭圆形;纤层骨被生长停滞线(LAGs)分为若干骨板,每层骨板厚度较大;在三角脊下方的纤层骨外侧区域有一处骨骼重建区,哈佛斯系统密集,最大代数可达3代。(3)具有三条LAGs(两条在纤层骨,一条在骨骼重建区),均较为浅淡;骨骼重建区厚度较薄,最大哈佛斯系统代数为3;骨内膜骨的胶原纤维整齐而平行,分层,外侧有脉管;髓腔无骨小梁,完全被方解石充填。上述骨组织特征表明:此甘氏四川龙个体的肱骨生长速度快,骨组织对运动和三角脊生长敏感,以骨组织重建来作适应和调整,年龄约为3~5岁,处于第二生长阶段初期。

Szechuanosaurus campi is a theropod from the Guangyuan City,Sichuan Province,and its horizon is the upper member of the Jurassic Shaximiao Formation.We have observed and analyzed the bone microstructure of bone tissue in the left humerus shaft of Szechuanosaurus campi,the results shows as follows:(1)Szechuanosaurus campi has typical skeleton structure of theropod,with inner circumferential lamellae(Endosteum),plexiform vascular canals in laminar fibrolamellar bone tissue,marrow cavity without interstitial lamellae(the trabecular bone),germinal layer of periosteum was dormant.(2)In the laminar fibrolamellar bone tissue,every bone plate was thick,and the growth rate of bone was fast;there was a bone reconstruction area in the laminar fibrolamellar bone tissue under the deltopectoral crest,Haversian system was dense,the maximum generation was up to three,and the bone tissue was sensitive to movement and the growth of the deltopectoral crest.(3)There were three LAGs,all of which were shallow,and the individual was 3~5 years old,it was inferred to be in the early phase of stage 2,not reaching its maximum size.