1. Introduction
The nanhsiungchelyids were a group of land turtles during the Late Cretaceous in Asia and North America, including a dozen taxa. Although well diversified in central Asia and northern China (Mlynarski, Reference Mlynarski1972; Sukhanov & Narmandakh, Reference Sukhanov and Narmandakh1977; Brinkman & Peng, Reference Brinkman and Peng1996; Sukhanov, Reference Sukhanov, Benton, Shishkin, Unwin and Kurochkin2000; Joyce & Norell, Reference Joyce and Norell2005; Danilov & Syromyatnikova, Reference Danilov and Syromyatnikova2008; Sukhanov, Danilov & Syromyatnikova, Reference Sukhanov, Danilov and Syromyatnikova2008), only two forms have hitherto been reported from the southern part of China (Ye, Reference Ye1966; Hirayama et al. Reference Hirayama, Zhong, Di, Yonezawa, Hasegawa and Symposium2009). Here we report on a complete turtle shell from the Late Cretaceous of southern China which belongs to a new genus and new species of Nanhsiungchelyidae.
The specimen was collected from the latest Cretaceous Nanxiong Formation in Ganxian County, northeast of Ganzhou City, Jiangxi Province (Fig. 1), during the construction of a development zone. The Nanxiong Formation or its equivalents are found across several provinces in southeastern China and represented by an extensive sequence of red mudstones, sandstones and conglomerates. In the Ganzhou area, these red beds have yielded lizard bones, dinosaur bones and eggs, and possible turtle eggs (Young, Reference Young1965, Reference Young1973; Sato et al. Reference Sato, Cheng, Wu, Zelenitsky and Hsiao2005; Mo, Xu & Evans, Reference Mo, Xu and Evans2009). The specimen described herein is housed in the Natural History Museum of Guangxi Zhuang Autonomous Region (NHMG), Nanning, China.
Figure 1. Map showing the location of Ganxian, Jiangxi Province, China.
2. Systematic palaeontology
TESTUDINES Linnaeus, Reference Linnaeus1758
CRYPTODIRA Cope, Reference Cope1868
nanhsiungchelyidae Ye, Reference Ye1966
Jiangxichelys n. g
Etymology. From Jiangxi Province.
Type species. Jiangxichelys ganzhouensis n. sp.
Diagnosis. A genus of Nanhsiungchelyidae of moderate size; carapace length up to 450 mm, without midline keel; cervical notch well developed and wide, and first vertebral vase-shaped as in Hanbodgemys. Different from all other nanhsiungchelyids in having the first marginal scute short and wide, with a long free edge and long contact with the second marginal; the second marginal boot-shaped, with a medial process reaching the first vertebral, preventing the contact between the first marginal and the first costal scute. In addition, it is different from Hanbodgemys in having a larger and triangular first suprapygal, a large and triangular fifth vertebral extending onto the tenth peripheral, narrower lateral marginal scutes and a narrower posterior lobe of the plastron; different from Zangerlia in the narrower and longer posterior lobe of the plastron; different from Nanhsiungchelys and Anomalochelys in the smaller cervical notch and narrower vertebrals; different from Kharakhutulia in the narrower plastron and longer anterior plastral lobe, which extends beyond the anterior edge of the carapace; different from Basilemys in the larger cervical notch, narrower peripherals and smaller posterior lobe of the plastron.
Distribution. Late Cretaceous of Jiangxi Province, China.
Jiangxichelys ganzhouensis n. sp.
Figures 2, 3
Etymology. From Ganzhou, the area where the specimen has been collected.
Figure 2. Jiangxichelys ganzhouensis n. g. n. sp. (Holotype, NHMG 010415) from the Late Cretaceous of Ganzhou, Jiangxi Province, China. (a, b) carapace in dorsal view; (c, d) plastron in ventral view; (e, f) carapace in posterior view. Scale bar: 10 cm.
Figure 3. Reconstruction of the carapace of Jiangxichelys ganzhouensis n. g. n. sp.
Holotype. A complete shell with articulated carapace and plastron (NHMG 010415, collection of the Natural History Museum of Guangxi Zhuang Autonomous Region, Nanning, Guangxi Province, China).
Type locality and horizon. Ganxian, northeast of Ganzhou City, Jiangxi Province, China; Nanxiong Formation, latest Cretaceous.
Diagnosis. Same as for genus.
Measurements. See Table 1.
Table 1. Measurements of Jiangxichelys ganzhouensis n. g. n. sp. (NHMG 010415) from the Late Cretaceous of Ganzhou, Jiangxi Province, China (in mm)
2.a. Description
Preservation. The shell is complete, with articulated carapace and plastron. Part of the right side of the carapace, from the second to the sixth neural, is crushed and slightly pushed towards the left.
Shell surface ornamentation. The surface of the shell is worn. However, a clear sculpture composed of large cells separated by ridges, similar to that of Nanhisungchelys wuchingensis (Ye, Reference Ye1966) and Zangerlia neimongolensis (Brinkman & Peng, Reference Brinkman and Peng1996), is visible on the carapace.
The carapace is oval in shape and broad; it is relatively high in comparison with Nanhsiungchelys. The cervical notch is wide and deep as in Hanbodgemys orientalis and H. jaganchoboli (Sukhanov, Reference Sukhanov, Benton, Shishkin, Unwin and Kurochkin2000; Sukhanov & Narmandakh, Reference Sukhanov, Narmandakh, Danilov and Parham2006). As in H. jaganchoboli, the peripherals have an obtuse cross-section in the bridge region. The posterior peripherals are subvertical and their ventral edge is turned inward, as in Zangerlia neimongolensis.
The nuchal is trapezoidal, and wider than that of H. jaganchobili. The first neural is nearly complete, with the posterior end damaged. It appears to be rectangular in shape. The second neural is long and hexagonal, with short posterolateral sides. The third neural is rectangular and shorter than the second one. The fourth neural is hexagonal with short anterolateral sides. The fifth neural seems to be similar to the fourth in shape. The outlines of the sixth and the seventh neurals are not discernible. The eight neural is slightly longer than wide and reaches the first suprapygal. The neural formula is thus 4<6<4>6>6–?–?–4. This neural formula is unusual among nanhsiungchelyids. There are two suprapygals. The first is triangular and relatively large, contacting the eighth neural and eighth costals anteriorly and the second suprapygal posteriorly. The second suprapygal is much larger and wider than the first one, contacting the first suprapygal and the eighth costals anteriorly, the pygal and the eleventh peripherals posteriorly and the tenth peripherals laterally. The pygal is wider than long; and convex posteriorly. Eleven peripherals are present. The peripherals are all wide, being twice or more the width of the marginal scute. The first peripheral has a strongly angled free margin as in Hanbodgemys and Nanhsiungchelyis.
The cervical scute is single and more than twice wider than long, with forwards convergent lateral margins. The first vertebral scute is vase-shaped, with rounded lateral margins as in Hanbodgemys; it is slightly wider than long. The second vertebral is narrow and longer than wide. The third and fourth vertebrals are incomplete; they appear to be similar to the second vertebral in shape. The fifth vertebral is roughly triangular in shape and extends onto the tenth peripheral plate. The pleural scutes are wide, with the width of the second and third pleurals being more than twice of that of the corresponding vertebrals. The first pleural contacts the second to fifth marginals; the second pleural contacts the fifth to seventh marginals; the third pleural contacts the seventh to ninth marginals and the fourth pleural contacts the ninth to eleventh marginals. The marginal scutes are all narrow and included in the peripherals except the first, the second, the eleventh and the twelfth. The first marginal is very short and wide, with a long free margin. The second marginal is boot-shaped, with a long medial process extending onto the nuchal plate and contacting the first vertebral scute. As a result, there is no contact between the first marginal scute and the first pleural scute. The eleventh and the twelfth marginals are mesiolaterally expanded, extending well onto the second suprapygal (Fig. 2e, f).
The plastron is complete, but the surface is worn, so some sutures and most sulci are not discernible. The plastron is sutured to the carapace. The anterior lobe is long and triangular in shape, extending slightly beyond the anterior margin of the carapace. It is longer than the posterior lobe. The bridge is long, being clearly longer than the anterior lobe. The posterior lobe is short and narrow; and its end is far anterior to the posterior end of the carapace. The base of the posterior lobe is slightly narrower than the base of the anterior lobe. The epiplastron has a long midline suture. The hyoplastron is slightly longer than the hypoplastron in the bridge region. The contact suture of the hyoplastron with the fifth and sixth peripherals; and that of the hypoplastron with the seventh and eighth peripherals are visible on the left side. The xiphiplastron is long, with a straight xiphiplastron/ hypoplastron suture which is close to the inguinal notch. The only preserved sulcus, the abdomino-femoral sulcus, is mostly straight with the lateral end turning posteriorly, lying anterior to the inguinal notch as in other nanhsiungchelyids.
2.b. Comparisons and discussion
NHMG 010415 is assigned to the family Nanhsiungchelyidae on the basis of the following combination of characters: the large-celled sculpture on the shell surface, a complete series of neurals, the plastron sutured to the carapace, the long bridge and the well-developed anterior lobe of the plastron. The complete neural series reaching the suprapygal in our specimen is different from Adocidae. The family Nanhsiungchelyidae consists of five genera in Asia and one genus in North America. The Asian taxa include Nanhsiungchelys wuchingensis from the latest Cretaceous of Guangdong, China (Ye, Reference Ye1966), Zangerlia from the Late Cretaceous of Mongolia and Inner Mongolia, China (Mlynarski, Reference Mlynarski1972; Brinkman & Peng, Reference Brinkman and Peng1996; Sukhanov, Reference Sukhanov, Benton, Shishkin, Unwin and Kurochkin2000; Joyce & Norell, Reference Joyce and Norell2005; Sukhanov & Narmandakh, Reference Sukhanov, Narmandakh, Danilov and Parham2006), Hanbodgemys orientalis from the late Turonian–early Santonian of Eastern Gobi, Mongolia (Sukhanov & Narmandakh, Reference Sukhanov and Narmandakh1977; Sukhanov, Reference Sukhanov, Benton, Shishkin, Unwin and Kurochkin2000; Sukhanov & Narmandakh, Reference Sukhanov, Narmandakh, Danilov and Parham2006), Anomalochelys angulata from the Cenomanian of North Japan (Hirayama et al. Reference Hirayama, Sakurai, Chitoku, Kawakami and Kito2001), and Kharakhutulia kalandadzei from the Cenomanian–early Turonian of eastern Mongolia (Sukhanov, Danilov & Syromyatnikova, Reference Sukhanov, Danilov and Syromyatnikova2008). An additional taxon, Bulganemys jaganchoboli Sukhanov & Narmandakh, Reference Sukhanov, Narmandakh, Danilov and Parham2006, is considered as a species of Hanbodgemys in a recent review (Danilov & Syromyatnikova, Reference Danilov and Syromyatnikova2008), an opinion we follow here.
Anomalochelys and Nanhsiungchelys differ from NHMG 010415 in their larger size, in the very deep cervical notch and triangular first vertebral scute which is very narrow anteriorly. In addition, the cervical notch of Anomalochelys is formed only by the nuchal.
Both Kharakhutulia and Basilemys have a very shallow cervical notch which is different from the large and well-marked notch in NHMG 010415. Kharakhutulia differs from NHMG 010415 in its smaller size, and in the trapezoidal first vertebral scute that is wider anteriorly and extends onto the first peripheral plate. The plastron is wide and short, with a short anterior lobe which does not extend up to the anterior margin of the carapace and a very wide posterior lobe. Basilemys differs from NHMG 010415 in its small cervical scute, smaller first suprapygal plate, and the mesiolaterally expanded peripherals. The plastron is larger, with a longer bridge and wider posterior lobe in comparison with NHMG 010415 (Riggs, Reference Riggs1906; Hay, Reference Hay1908; Langston, Reference Langston1956; Mlynarski, Reference Mlynarski1976).
Zangerlia contains four species (Z. testudimorpha Mlynarski, Reference Mlynarski1972; Z. neimongolensis Brinkman & Peng, Reference Brinkman and Peng1996; Z. ukhaachelys Joyce & Norell, Reference Joyce and Norell2005 and Z. dzamynchondi Sukhanov & Narmandakh, Reference Sukhanov, Narmandakh, Danilov and Parham2006). In this genus, the posterior lobe of the plastron is wide and short (Z. ukhaachelys) to very short (Z. testudimorpha and Z. neimongolensis), different from the relatively long and narrow plastron of NHMG 010415. In addition, in Z. testudimorpha and Z. dzamynchondi, the hypoplastron is shortened and does not contribute to the posterior lobe. The anterior end of the carapace is known only in Z. dzamynchondi. It has a deep and narrow cervical notch, which is different from that of NHMG 010415. Zangerlia is likely a paraphyletic group, since the deep cervical notch on the carapace, as seen in Z. dzamynchondi, does not seem consistent with the relatively small skull which has a deep temporal emargination, as known in Z. neimongolensis. Hirayama et al. (Reference Hirayama, Sakurai, Chitoku, Kawakami and Kito2001) recognized two distinct types in the family Nanhsiungchelyidae: the first has a relatively large skull with a weak temporal emargination (Nanhsiungchelys (Ye, Reference Ye1966)), and the second shows a much smaller skull with a distinct temporal emargination (Zangerlia neimongolensis (Brinkman & Peng, Reference Brinkman and Peng1996), Basilemys (Langston, Reference Langston1956; Brinkman, Reference Brinkman1998)). It is worth noting also that the first type (large skull with weak temporal emargination) is associated with a carapace which has a deep cervical notch, while the second type (a much smaller skull with a distinct temporal emargination) is usually associated with a carapace which has a weak cervical notch. Thus the four species of Zangerlia probably belong to two distinct groups.
Among nanhsiungchelyids, NHMG 010415 most resembles Hanbodgemys orientalis in having a wide and well-marked cervical notch, a vase-shaped first vertebral, very narrow second to fourth vertebrals and a long triangular anterior lobe of the plastron. H. jaganchoboli is based on an incomplete carapace and bridge region of the plastron. Its general morphology is similar to that of H. orientalis, but the size is smaller (Sukhanov, Reference Sukhanov, Benton, Shishkin, Unwin and Kurochkin2000; Danilov & Syromyatnikova, Reference Danilov and Syromyatnikova2008). In addition, NHMG 010415 shares with the two species of Hanbodgemys the very wide and short first marginal scute, with a long free margin. However, the second marginal scute of NHMG 010415 is boot-shaped, with a long medial process reaching the first vertebral scute and preventing the contact between the first marginal and the first pleural scute. This morphology is unique among nanhsiungchelyids and considered here as an autapomorphic feature. In Hanbodgemys jaganchoboli, the boot-shaped second marginal is present only on the right side, while the left second marginal has a normal rectangular shape (Sukhanov, Reference Sukhanov, Benton, Shishkin, Unwin and Kurochkin2000, fig. 17.24); it is thus considered here as an anomaly. The similar first and second marginal scute pattern is also known in Basilochelys macrobios, a basal trionychoid from the latest Jurassic–earliest Cretaceous Phu Kradung Formation of NE Thailand (Tong et al. Reference Tong, Claude, Naksri, Suteethorn, Buffetaut, Khansubha, Wongko, Yuangdetkla, Buffetaut, Cuny, Loeuff and Suteethorn2009). However, Basilochelys is much larger, with a carapace length up to 90 cm, and the general shape of its carapace, and particularly the plastron is very different. In addition, NHMG 010415 differs from Hanbodgemys in the larger first suprapygal relative to the second suprapygal. This is considered here as a primitive feature among nanhsiungchelyids, found also in Zangerlia testudinimorpha (Mlynarski, Reference Mlynarski1972). In both species of Hanbodgemys, Zangerlia neimongolensis (Brinkman & Peng, Reference Brinkman and Peng1996) and Basilemys variolosa (Langston, Reference Langston1956), the first suprapygal is much smaller than the second. NHMG 010415 also differs from Hanbodgemys in the narrower lateral marginals, which cover less than half the width of the peripheral plates. In Hanbodgemys orientalis, ‘the pleura-marginal sulcus probably coincides with the costo-peripheral suture’ (Sukhanov, Reference Sukhanov, Benton, Shishkin, Unwin and Kurochkin2000, p. 343). In H. jaganchoboli, the marginals cover more than two thirds of the width of the peripheral. NHMG 010415 has a large triangular fifth vertebral scute which extends onto the tenth peripheral. This is different from the small and rounded fifth vertebral of Hanbodgemys orientalis and H. jaganchoboli which is included in the second suprapygal posteriorly. The large and triangular fifth vertebral is present also in Zangerlia testudimorpha, Basilemys variolosa and B. sinusosa; but only in Basilemys this scute extends onto the tenth peripheral like in NHMG 010415. Although the plastron of NHMG 010415 did not deliver much detail on morphology of the scutes and some plates, its whole shape is quite different from that of Hanbodgemys orientalis, except for the shape of the anterior lobe. The base of the anterior lobe in NHMG 010415 is slightly wider than the base of the posterior lobe, in contrast to H. orientalis. In addition, the posterior lobe of NHMG 010415 is narrower and longer than that of H. orientalis. The comparison between NHMG 010415 and other nanhsiungchelyids is summarized in Table 2. The reconstruction of the carapace is shown in Figure 3.
Table 2. Comparison between Jiangxichelys ganzhouensis n. g. n. sp. and other nanhsiungchelyids
1Zangerlia dzamynchondi is not included.
3. Conclusions
In conclusion, a new genus and new species of Nanhsiungchelyidae is erected: Jiangxichelys ganzhouensis n. g. n. sp. It is characterized by a combination of primitive and apomorphic features and close to Hanbodgemys, thus nested in the clade composed of Hanbodgemys, Nanhsiungchelys and Anomalochelys (Hirayama et al. Reference Hirayama, Sakurai, Chitoku, Kawakami and Kito2001). The relatively high domed carapace and the long anterior lobe of the plastron extending beyond the anterior margin of the carapace which are reminiscent of some land tortoises, indicate that Jiangxichelys probably had a terrestrial lifestyle like other nanhsiungchelyids. The family Nanhsiungchelyidae was a successful group of land turtles during the Late Cretaceous in Asia; most of them are concentrated in Mongolia (Danilov & Syromyatnikova, Reference Danilov and Syromyatnikova2008; Sukhanov, Danilov & Syromyatnikova, Reference Sukhanov, Danilov and Syromyatnikova2008). In southern China, in addition to Nanhsiungchelys wuchingensis, a nanhsiungchelyid turtle close to Anomalochelys was reported recently from the Latest Cretaceous of Nanxiong Basin (Hirayama et al. Reference Hirayama, Zhong, Di, Yonezawa, Hasegawa and Symposium2009). The discovery of Jiangxichelys ganzhouensis adds a new element to the poor record of nanhsiungchelyids from southern China, and demonstrates the diversity of the family in that area.
Acknowledgements
The authors would like to thank Lidi Cen who prepared the specimen and Eric Buffetaut for improving the manuscript.
