四川自贡大山铺成渝龟科—新属

描述了产自四川自贡大山铺恐龙化石坑中的三件龟甲标本，命名为一新属新种—周氏四川龟（Sichuanchelyschowigen．etsp．nov．）。该属以椎盾极横宽，中部缘盾极狭长为主要特征，它代表了成渝龟科中一类较特别的类型。

A NEW GENUS OF CHENGYUCHELYIDAE FROM DASHANPU, ZIGONG, SICHUAN

A new fossil ede, Sichuanchelys chowi, is described in ths paper Thespecimens were unearthd together with dinosaurs from lerer Shaximiao Formation ofhashanpu Town, Zigong City, Sichua Province, S0uthwe-stem China- The geol0gicalage ot the Formation is genendly considered as Middle hesic. The specimensinclude tae shells which represent resPechvely by itS caraPace united with itS plastron.The holotype ZDM30l4(speimen ntunber 0f bgong ixnosaur Museuin is arelatively complete specimen. In view of the structures of shell, it has typical featuresof Chengyuchelyidae, such as: carapace oval; extomal surface of shell lasldng obviousomamntation; neural plates hexagonal in form and with shortsides in front bonybridge broad; mesopastron present siased in abdominal scuto, and meehng it8 pairat nddde line; and the geological age is Middle hesic. Therefore, it is doubhessthat ZDM30l4 is included in Chengyuchelyidae. Detalled comparisons of ZDallOl4with Chengyuchelys and Wiangchelys see the chinese text (table 2). According tO theremarkable differences among them, a new genus and sPecies Sichuanchelys chowi isProposed. The diagnosis of the genus and species can be summallzed as below fIndividua small. Shell flat and oval in form. Extemal sdse lasking obviousomamentation. Anterior end of cmpe relatively concaved backward' Most netalshexagonal shaPed and with shortsides in front. Vedebra scutes extremely br0ad andthe ratios of the maxium width to the ndddle length of the vertebnd scutes 2,3 arelarger than 3.O. Costa sclltes slighty narrowed. Medial marginal scutes exbemelynarrwed. Plastron long and narrow, and much shorter than carapace in Postorior end.Bony bridge broad and with 3-4 inframarginal scutos- Gular scutes and intergularscutes Presenl Entoplastron small. Humermpectoral sulcus far behind endoplastron.MesoPlastron Present sihated in abdondnal scllte, and narrowed at its ndddie patFemerral sulcus convexed forward, bu not meeted hypoxiphiplastral suture.ZDW0l7 and ZDMi00l are two incoinpete specimens. The Presence ofmesopastron is not definito. But the general featurs of the shells are very similar tothose 0f ZDM30l4, and they are froin the sam fossil mp. Therefore, it seemsreasonable to include these two specimens to Sichuanchelys chowi fUP to n0w, the Jurassic turtles with a mesoplastron bon in China are includdChengyuchelyidae and reprsented by three genera: Chengyuchefys Wiangchelys andSichuanchelys. They are new groups 0f Cryptodira represenhng an eary forh inturtle evolution.