Cretaceous Research (1996) 17 , 505 – 508

Short communication

The ‘‘ornithurine’’ from the Lower Cretaceous of Changji , Xinjiang (China) : bird or pterosaur?

Eric Buf fetaut

URA 1 7 6 1 du CNRS , Laboratoire de Pale ́ ontologie des Verte ́ bre ́ s , Case 1 0 6 , Universite ́ Paris 6 , 4 place Jussieu , 7 5 2 5 2 Paris Cedex 0 5 , France

Revised manuscript accepted 1 7 January 1 9 9 6

A tibia with a fused fibula from the Lower Cretaceous of Changji (Xinjiang , China) , originally interpreted as possibly belonging to an ornithurine bird , is redescribed and interpreted as belonging to a dsungaripterid pterosaur . ÷ 1996 Academic Press Limited

K E Y W O R D S : Early Cretaceous ; Xinjiang ; China ; Pterosauria ; Aves ; reinterpretation .

1 . Introduction

In recent years , a number of bird remains have been reported from the Mesozoic of China , mostly from the Lower Cretaceous (Dong , 1993 ; Hou , 1994 ; Hou & Liu , 1984 ; Hou & Zhang , 1993 ; Sereno & Rao , 1992) , but also from the Upper Jurassic (Hou , 1995 ; Hou et al . , 1995) . These Chinese finds have greatly enlarged our knowledge of Mesozoic birds . However , as early as 1964 a fossil from the Lower Cretaceous of Changchi (now spelled Changji in the Pinyin system of transliteration) , in Xinjiang (northwestern China) , was considered as a possible bird bone by Young . This bone , a tibia with the fused fibula , was referred to as ‘‘? Ornithurae indet . ’’ by Young , who concluded his description of it as follows : ‘‘We refrain from doing further determination but like to point out that the present specimen may some day prove to be the first record of Mesozoic avian find in China’’ (Young , 1964 , p . 255) . It should be noted , however , that Young was even more cautious in the Chinese version of his paper , in which he wrote that the Changji bone , if it was not a pterosaur , might be the first record of a Mesozoic bird in China . The specimen was actually figured in Young’s paper (1964 , fig . 11) under the caption ‘‘Dsungaripteroidea indet . ’’ . Since Young’s original description , the tibia from Changji has attracted little attention . It is not mentioned , either as bird or as pterosaur , in the catalogue of Chinese fossil reptiles and birds by Sun et al . (1992) , and it does not appear in general catalogues of pterosaurs (Wellnhofer , 1978 , 1991) either . The purpose of the present paper is to re-examine this bone in order to determine whether it actually belongs to a bird , or should be referred to a pterosaur .

2 . Geological setting

The supposed bird bone from Xinjiang was collected by a field party of the Xinjiang Bureau of Petroleum Af fairs near Changji , a town north-west of the city of Urumqi , in the southern part of the Junggar Basin , north of the Tian Shan 0195 – 6671 / 96 / 040505 1 04 $18 . 00 / 0 ÷ 1996 Academic Press Limited

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mountains . The geological data made available to Young were relatively scanty : the specimen , a fairly well preserved limb bone on a block of greyish sandstone , apparently came from the Changji River (‘‘Changchiho’’) , and its age was determined as Early Cretaceous .

The Cretaceous geology of northern Xinjiang has recently been reviewed by Shen & Mateer (1992) . On the southern margin of the Junggar Basin , Cretaceous outcrops extend in a narrow zone along the northern edge of the Tian Shan fold belt . The Lower Cretaceous is represented there by the Tugulu Group , a thick succession of fluvio-lacustrine beds , which is divided into several formations (probably ranging in age from Neocomian to Albian ; see Shen & Mateer , 1992) . Although it is likely that the bone from Changji comes from the Tugulu Group , it is dif ficult to assign it to a particular formation on the basis of the available data . Farther to the northwest , at Urhe (also spelled Wuerho in some older publications) , the upper part of the Tugulu Group (Lianmuqing Formation) has yielded a diverse vertebrate fauna including turtles , crocodilians , dinosaurs and pterosaurs (see Dong , 1992 ; Shen & Mateer , 1992) .

The specimen from Changji is now kept at the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing , under no . V . 2779 .

3 . Redescription and discussion

Young’s description of the tibia from Changji was accurate and little can be added to it . The bone , from the right side of the body , is long (length : 165 mm) , straight and slender (width of the proximal end , as preserved : 10 mm) . The proximal end is slightly expanded and appears roughly triangular in outline , but this shape is partly due to breakage , and the original outline was probably more rounded . The distal end is damaged , but still shows a well-defined lateral condyle for articulation with the tarsus (the medial condyle is destroyed) . The fibula is reduced to a thin splinter which is fused to the tibia along most of its length distally . It is separated from the tibial shaft for 40 mm in its proximal half , but the proximal end is fused to that of the tibia .

Young (1964 , p . 255) thought that ‘‘this bone looks quite similar to the tibia of Hesperornis ... ’’ . However , comparison with Marsh’s description and figures of the tibia of this flightless marine bird from the Upper Cretaceous of Kansas (Marsh , 1880) reveals more dif ferences than resemblances . Besides the fact , already noted by Young , that the tibia of Hesperornis is much larger than that from Changji , it is also much more robustly built , with stronger reliefs . The proximal articulation looks quite dif ferent , with a strong proximally prominent cnemial crest which is

Figure 1 . Right tibia of a pterosaur from the Lower Cretaceous of Changji (Xinjiang , China) . The reduced and largely fused fibula is visible as a splint of bone along the lateral edge of the tibia in its proximal half . Institute of Vertebrate Paleontology and Paleoanthropolgy , Beijing , no . V 2779 . Scale bar : 5 cm .

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lacking in the bone from Changji . The distal articular region is dif ferent , too , with condyles which are somewhat slanted medially , whereas in the Changji bone the condyles are in line with the axis of the shaft . Therefore , there is no reason to suppose any relationship with Hesperornis . More generally , the dif ferences listed above apparently apply to most birds , in which the tibia usually exhibits a strong proximally projecting cnemial crest , and slightly oblique distal condyles (see Milne-Edwards , 1867-1871 , for illustrations of the tibia in a large number of birds) . On the basis of these dif ferences , it appears that the Changji tibia cannot be referred to a bird .

Resemblances with pterosaurs are more numerous . As noted by Wellnhofer (1991) , in early pterosaurs the fibula is developed to full length , but in more advanced forms it no longer reaches the tarsus distally , and in Cretaceous pterosaurs it is markedly reduced or completely absent . In the Changji specimen , the fibula shows an advanced stage of reduction , since it is fused to the tibia at both ends and along most of its length . A very similar condition is known in Noripterus complicidens , a dsungaripterid pterosaur described by Young (1973) from the Lower Cretaceous (upper part of the Tugulu Group) of Urhe in northwestern Xinjiang . Direct comparison of the tibia from Changji with that of Noripterus (on the basis of specimens kept at the IVPP) reveals marked resemblances in the general shape of the bone , the degree of fusion of the fibula , and the shape of the articular ends (although in this latter respect comparisons are made slightly more dif ficult by the incomplete condition of the Changji specimen) . Comparisons with another well known dsungaripterid pterosaur from the Lower Cretaceous of Urhe , Dsungaripterus weii , are more dif ficult , because the tibia is incompletely known in this form (Young , 1964) .

On the basis of the great resemblances with the tibia of Noripterus complicidens , it therefore seems safe to refer the tibia from Changji to a dsungaripterid pterosaur .

4 . Conclusions

When Young (1964) tentatively referred the specimen from Changji to an ornithurine bird , he was cautious enough not to exclude the possibility that it might in fact belong to a pterosaur . Resemblances with a bird tibia are in fact superficial , and comparison with the tibia of Noripterus complicidens (which was not yet known when Young described the Changji specimen in 1964) clearly indicates that the tibia and fused fibula from Changji should in fact be referred to a pterosaur , in all likelihood a representative of the family Dsungaripteridae . The occurrence of a dsungaripterid in the Lower Cretaceous of the southern rim of the Junggar Basin is by no means surprising , considering that dsungaripterids were first described from the Lower Cretaceous Tugulu Group of another part of that basin , where they occur in some abundance . Although Cretaceous birds are now known from a number of localities in China , the Changji specimen is clearly not one of them .

Acknowledgements

I am grateful to Prof . Li Chuankuei and Prof . Dong Zhiming for their assistance during my visits to the IVPP ; to Mr Zhao Hong for access to the material in the IVPP collections ; to Prof . Wann Langston (Austin) and Dr Hou Lianhai (Beijing)

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for helpful comments ; and to my wife , Dr Tong Haiyan , for her translations of Chinese papers .

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