TY - JOUR

T1 - A reassessment of some poorly known turtles from the Middle Jurassic of China, with comments on the antiquity of extant turtles

AU - Danilov, Igor G.

AU - Parham, James F.

N1 - Funding Information: We thank Professor J. Li, Dr. Y. Wang and Ms. F. Zheng (IVPP, Beijing, China) for access to the turtle collection of the IVPP and hospitality. Ted Papenfuss (University of California Museum of Vertebrate Zoology, Berkeley, USA) provided invaluable assistance to both of us; without him our collaborations on Chinese fossil turtles would be impossible. Haiyan Tong and Eric Buffetaut (Paris, France) are thanked for access to material of Siamochelys peninsularis. Randall Irmis (University of California Museum of Paleontology, Berkeley, USA) and Walter Joyce (Yale University, New Haven, USA) provided key references for Jurassic turtles of Europe while RI also helped with the age of Middle Jurassic epochs. Walter Joyce and an anonymous reviewer provided helpful comments. The support of Sarah Rieboldt (Santa Barbara, USA) facilitated the work of JFP. This study is done with the financial support of a grant of the President of the Russian Federation (NSh-4212.2006.4) and a grant of the Russian Foundation for Basic Research (04-05-65000-a) to IGD. This is University of California Museum of Paleontology contribution #1935.

PY - 2008/6/12

Y1 - 2008/6/12

N2 - Recent studies have shown that the Middle Jurassic is a key time for understanding the origin and early evolution of crown group turtles, but few turtle-bearing localities from this epoch are known. This study adds to our knowledge by providing a detailed description of two poorly characterized specimens (IVPP-V6507 and IV-PP-V8805) from the Middle Jurassic of China that previously were both assigned to the poorly known species Chengyuchelys baenoides. This reappraisal allows us to present new observations, images, and taxonomic conclusions about these specimens and others from the same locality (Dashanpu, Zigong Prefecture, Sichuan Province, China). With at least four species, Dashanpu is the most diverse locality from the Middle Jurassic; all other turtle localities from this time have only one species each. We place Chengyuchelys into a cladistic analysis of turtle relationships for the first time. Our analysis places Chengyuchelys as sister to Xinjiangchelys latimarginalis and solidly on the stem of Cryptodira. This result is surprising because Chengyuchelys retains mesoplastra. Nevertheless, derived osteological and scalation characters of this taxon drive its phylogenetic position as a relatively advanced stem cryptodire. This finding, combined with a reappraisal of other Middle Jurassic turtles from Asia, shows that the crown group Testudines had evolved by the Middle Jurassic. Unfortunately, many key specimens from Sichuan Province are still poorly characterized morphologically and stratigraphically. This lack of phylogenetic and temporal resolution hinders our understanding of the origins of extant turtle clades, but also highlights the importance of Jurassic Asian turtles for ultimately resolving these issues.

AB - Recent studies have shown that the Middle Jurassic is a key time for understanding the origin and early evolution of crown group turtles, but few turtle-bearing localities from this epoch are known. This study adds to our knowledge by providing a detailed description of two poorly characterized specimens (IVPP-V6507 and IV-PP-V8805) from the Middle Jurassic of China that previously were both assigned to the poorly known species Chengyuchelys baenoides. This reappraisal allows us to present new observations, images, and taxonomic conclusions about these specimens and others from the same locality (Dashanpu, Zigong Prefecture, Sichuan Province, China). With at least four species, Dashanpu is the most diverse locality from the Middle Jurassic; all other turtle localities from this time have only one species each. We place Chengyuchelys into a cladistic analysis of turtle relationships for the first time. Our analysis places Chengyuchelys as sister to Xinjiangchelys latimarginalis and solidly on the stem of Cryptodira. This result is surprising because Chengyuchelys retains mesoplastra. Nevertheless, derived osteological and scalation characters of this taxon drive its phylogenetic position as a relatively advanced stem cryptodire. This finding, combined with a reappraisal of other Middle Jurassic turtles from Asia, shows that the crown group Testudines had evolved by the Middle Jurassic. Unfortunately, many key specimens from Sichuan Province are still poorly characterized morphologically and stratigraphically. This lack of phylogenetic and temporal resolution hinders our understanding of the origins of extant turtle clades, but also highlights the importance of Jurassic Asian turtles for ultimately resolving these issues.

UR - http://www.scopus.com/inward/record.url?scp=47349110710&partnerID=8YFLogxK

U2 - 10.1671/0272-4634(2008)28[306:AROSPK]2.0.CO;2

DO - 10.1671/0272-4634(2008)28[306:AROSPK]2.0.CO;2

M3 - Article

AN - SCOPUS:47349110710

VL - 28

SP - 306

EP - 318

JO - Journal of Vertebrate Paleontology

JF - Journal of Vertebrate Paleontology

SN - 0272-4634

IS - 2

ER -