Sciurid remains from the Late Cenozoic fi ssure- fi llings of Fanchang, Anhui, China

QIU Zhu-Ding JIN Chang-Zhu

(Institute of Vertebrate Paleontology and Paleoanthropology,Chinese Academy of SciencesBeijing 100044 qiuzhuding@ivpp.ac.cn)

Sciurid remains from the Late Cenozoic fi ssure- fi llings of Fanchang, Anhui, China

QIU Zhu-Ding JIN Chang-Zhu

(Institute of Vertebrate Paleontology and Paleoanthropology,Chinese Academy of SciencesBeijing 100044 qiuzhuding@ivpp.ac.cn)

Remains of sciurids from a late Cenozoic fi ssure in Anhui, China are described. Six texa, including one new genus and two new species, representing fi ve genera and four tribes in the subfamily Sciurinae are recognized. They areSciurussp.,Tamiassp.,Plesiosciurus zhengisp. nov.,Sciurotamias wangiQiu, 2002,S. teilhardiZheng, 1993, andPseudoratufa wanensisgen. et sp. nov. The material described was collected from four levels of the fi ssure fi llings. On the basis of the fossil content and coloration, the collection is considered to be a mixed sample with elements representing a rather long interval, probably ranging from the Early Miocene to the Pleistocene. The assemblage shows similar traits of the late Cenozoic sciurine faunas from central and southern China, and contains an intriguing genusPseudoratufa. Characters of the latter’s dentition clearly demonstrate that the new-comer of ratu fi n is a tree squirrel;Pseudoratufais probably coeval with the Fanchang hominoid, and withDiatomysand beavers found in this fi ssure. The joint occurrence of these taxa seems to be indicative of existence of forest biotopes once in this district during the earlier Miocene.

Fanchang, Anhui, China; late Cenozoic; fi ssure fi lling; Sciuridae

1 Introduction

Fanchang is a county in southeastern Anhui Province, and lies about 20 km to the south of the Chang Jiang (the Yangtse River). Fissure- fi llings are well developed in the Permian and Triassic limestones spread in this district (Yuan et al., 2009). Four mammal bearing fi ssures, Tangkou, Renzidong, Xidong, and Ludong in different ages were discovered by local people in the late 1980s and 1990s at Laili Hill, a limestone quarry 2 km northwest of the Sun village and 10 km southwest of the county seat (Fig. 1). A preliminary investigation of the mammalian remains from the four fi ssures reveals that the age of fossils contained in the deposits seems to be correlative with the topographical elevation of the fi ssures, i.e., the higher the fi ssure, the older the age. The Tangkou sample includes elements indicative of Early or Middle Miocene age, whereas the Ludong only of the Late Pleistocene, and the Renzidong and the Xidong inbetween. Remains of mammals from the Early Pleistocene Renzidong, including more than 70 species in 9 mammalian orders, have been studied in detail (Jin and Liu, 2009).

Fig. 1 Geographic location of the fossil site in Anhui (inset in upper left) and the Laili Hill limestone quarry at Fanchang showing fossiliferous fi ssures of different elevation and age A. Tangkou, Miocene-Pleistocene; B. Renzidong, Early Pleistocene; C. Xidong, Middle Pleistocene; D. Ludong, Late Pleistocene

The Tangkou site, discovered in the late 1980s, is at the top of the Laili Hill (31º5ʹ23"N, 118º5ʹ46"E), at an elevation about 143 m above sea level. The visible deposits in this fissure reach a thickness of more than 20 m, which can be divided into four levels (in ascending order) as follows (Fig. 2).

The fissure-fillings from this site can be divided into two units. Deposits from Layer 1-3 consist of alternating beds of fine-grained, coarse sandstones and conglomerates, while those from Layer 4 are made up of clays and brecciated limestones and shales fallen locally from the surrounding rocks. Remains from Layer 1-3 are usually worn by water transportation and colored gray or grayish brown and black, in contrast to those from Layer 4 that are colored reddish yellow and show no sign of abrasion.

Fig. 2 Section of the Tangkou fi ssure- fi lling at Laili Hill, Fanchang

1. Grayish yellow sandstones. Lithologically this sandstone is well-cemented. It consists of fine-grained sandstones at the base, and grades upward into pebbly medium to coarse-grained sandstones, and lenticular bodies of sands and gravels occur locally in the upper part. Remains of mammals in this layer are rare. ＞9.6 m

2. Brownish gray coarse sandstones. It is a layer of well-indurated, pebbly rocks interbedded with siliceous bands locally. The gravels are better sorted and usually 1-3 cm in diameter. This layer contains a small number of mammalian remains. 0.8 m

3. Brownish gray sandstones and conglomerates. Sediments in this layer are cemented and rather hard. Gravels contained within are well-rounded, generally 1-5 cm in diameter. Contains remains of hominoids,Platybelodon,Hipparion,Kubanochoerus, and other mammals. 4.8 m

4. Reddish brown sandy clays with brecciated limestones and occasionally yellowish shales. The gravels, broken locally, are poorly rounded and sorted, and highly diverse in size (generally 8-30 cm and attaining a maximum size of 50 cm). Fossil remains are sparce. 5.6 m

Zheng (1993) fi rst reported fragmentary materials ofKubanochoerusandPlatybelodonat this site. Subsequently, during the fi eld seasons of 1999-2001 abundant remains of mammals, including 55 isolated teeth of hominoids, more than two dozen species in Insectivora, Chiroptera, Lagomorpha, Rodentia, Carnivora, Proboscidea, Perissodactyla, and Artiodactyla represented by hundreds of specimens, were collected by a team led by one of us (Jin Changzhu) funded by the project “the State Key Scienti fi c Research”, a program of “Research of the Early Hominid Ancestors of 2-4 Ma in China and Their Environmental Background” (Jin and Wei, 1999). The sample was assembled throughout the fi ssure- fi llings of the above section (Fig. 2). This assemblage of mammals is quite varied, and apparently consists of taxa of different time intervals. The occurrence ofDemocricetodon,Megacricetodon,Diatomys,PlatybelodonandKubanochoerusin this sample obviously indicates an Early or Middle Miocene age, whileLeopoldamys, a large-sized murine, suggests an age younger than the Early Pliocene. This clearly displays that the Tangkou assemblage as featured in literature citations, consists of different mammal associations of mixed ages, ranging from Early Miocene to Pleistocene.

In this paper, we describe sciurid material collected from the fi ssure- fi llings at the Tangkou site. Although the sciurids described are a mixed sample with elements representing different periods, they improve our knowledge of taxonomy of the sciurid family and contribute to a better understanding of their spatial distribution in the late Cenozoic of China. The other mammal material will be described elsewhere.

2 Systematic description

(Fig. 3A-E)

Material Five cheek teeth (1 DP4, 1 P4, 1 M1/2, 1 M3, 1 m3), IVPP V 20847.1-5.

Measurements (length × width, in mm) DP4, 2.00 × 2.05; P4, 2.15 × 2.65, M1/2, 2.35 × 2.95, M3, 2.90 × 3.00; m3, 3.05 × 2.95.

Fig. 3 Cheek teeth ofSciurussp. andTamiassp. from Tangkou, FanchangSciurussp.: A. r DP4 (IVPP V 20847.1), B. r P4 (V 20847.2), C. r M1/2 (V 20847.3), D. r M3 (V 20847.4), E. l m3 (V 20847.5);Tamiassp.: F. r M3 (V 20848); in occlusal view

Description These teeth are rather heavily built with low and blunt cusps and crests. The DP4 is subtriangular, due to the prominent and expanded parastyle. The protocone is relatively high and slightly constricted. The protoloph and the metaloph are complete, with the lingual portion being slightly convergent to join the protocone. A protoconule and a metaconule are absent, but the middle part of the metaloph bulges slightly. There is a low buccal connection between the paracone and the metacone. The posteroloph is complete and pronounced, and gradually elevated to join the apex of the protocone. The P4 is similar to the DP4, except for its subrectangular outline due to the less expanded parastyle, the larger size, and the stronger cusp and lophs. The M1/2 is subquadrate in occlusal outline. The protocone is prominent and expanded anteroposteriorly. The transverse protoloph and somewhat oblique metaloph are low, but complete, with the latter slightly constricted just buccal of the protocone. No protoconule or distinct metaconule are present. The mesostyle is indistinct. Both anteroloph and posteroloph are complete and strong, but lower than the protoloph and the metaloph. The M3 and m3 are moderately expanded posteriorly. Enamel of the basins is smooth.

Remarks These teeth show relatively light color and no sign of wear by transportation, and probably come from the upper level. They cannot be referred to any taxon described, and represent a generalized sciurid with relatively large size in this assemblage. Judging from the heavily built cheek teeth, the low and strong principle cusps and crests, the anteroposteriorly expanded protocone and the nearly parallel arrangement of protoloph and metaloph on M1/2, this sciurid demonstrates characters of a tree squirrel, comparable to the genusSciurusboth in size and morphology. Compared with the extantSciurus vulgaris, the Fanchang sciurid is slightly larger in size, with stronger cusps and crests, and less posteriorly expanded M3 and m3. It is close toS.liifrom Shanwang in size, but differs in having stronger cusps and crests, and less posteriorly expanded M3 and m3 (see Qiu and Yan, 2005). Thus, these specimens are assigned to an indeterminate species ofSciurus, because of the inadequate material.

(Fig. 3F)

One M3 (IVPP V 20848) represents a small squirrel found in this assemblage. The tooth measured 1.70 mm long and 1.75 mm wide, is too small to match any described squirrels. It is moderately expanded posteriorly. The protocone and the paracone are pronounced and high. The protoloph is conspicuous but bearing no protoconule. A metaloph is absent. The anteroloph is marked and elevated. The posteroloph is distinct and connects the protocone to the paracone. Enemal of the basin is nearly smooth.

The M3 is similar to that ofTamiasorTamiopsin size and having a distinctly elevated anteroloph, but differs from the latter in being less expanded posteriorly and lacking rugged enamel on the basin. It resembles that ofTamiasmore closely than it does the corresponding tooth ofTamiops. Nevertheless, it is distinguishable from that ofTamiassibiricus, the living chipmunk widely distributed in the Palearctic Region of Asia, by somewhat smaller size, and from that ofT.ertemteensis, a common chipmunk in the Neogene faunas of central Nei Mongol, by its less posterior expansion (Qiu, 1991). Thus, it is assigned to an indeterminate species ofTamias.

(Figs. 4, 5; Table 1)

Plesiosciurusaff.P. sinensis: Qiu & Sun, 1988, p. 54.

Etymology Named in honor of Mr. Zheng Longting from the Anhui Museum, who fi rst reported the discoveries of the Tangkou fi ssure, and organized and helped in many aspects of the Fanchang fi eld works.

Holotype Left M1/2 (IVPP V 20849).

Paratypes Twenty eight cheek teeth (6 M1/2, 5 M3, 2 dp4, 1 p4, 8 m1/2, 6 m3), V 20850.1-28.

Table 1 Measurements of cheek teeth ofPlesiosciurus zhengifrom Tangkou, Fanchang (mm)

Measurements See Table 1.

Diagnosis Larger-sizedPlesiosciuruswith more heavily built cheek teeth. Metaconule absent, but the connection between paracone and metacone strengthened in M1 and M2; no sign of metaconule and metaloph in M3; and m1 and m2 less anteroposteriorly compressed with anterolingual-posterobuccally arranged ectolophid.

Description The outline of M1/2 is subquadrate and wider than long. The cusps are more striking and higher than the lophs. The protocone is large and slightly expanded anteroposteriorly. The complete protoloph and the metaloph are low, and nearly convergent to join the protocone, with the transverse protoloph bulging somewhat and the oblique metaloph distinctly constricted just buccal of the protocone. A protoconule and a metaconule are absent, but a bulge at the middle part of the metaloph is usually present. The anteroloph and the posteroloph are both complete and pronounced, but lower than the protoloph and the metaloph. A mesostyle is absent, and a steep connection between the paracone and the metacone is present. The M3 has the same pattern of the anterior portion of the M1/2, and has moderate expansion of the posterior part. It has no metaloph, and shows no notch between the posterior arm of the protocone and the posteroexternal lobe. Basin enamel is as smooth as in M1/2.

The p4 is distinctly narrower anteriorly than posteriorly, with the protoconid and the metaconid situated very close to one another, and the former located posteriorly to the latter. There is no anteroconid. The entoconid is completely incorporated in the posterolophid and the entoconid corner is curved. A mesoconid and a mesostylid are absent. The ectolophid is straight and orientated anterolingual-posterobuccally. The dp4 is similar to the p4, except for its smaller size, larger length relative to the width, weaker cusps and crests, and diverged roots. The m1/2 is subrhomboidal and slightly compressed anteroposteriorly. The entoconid is completely incorporated in the posterolingual crest. The entoconid corner is curved. A mesoconid and a mesostylid are lacking. The anterolophid is low and joins the base of the protoconid. The posterolophid is much more elevated than the anterolophid. The metalophid is complete, connecting the protoconid and metaconid to close the trigonid basin posteriorly. The buccal valley is moderately wide and the talonid basin is dammed by a straight and anterolingually arranged ectolophid. The m3 is moderately expanded posteriorly. The entoconid is incorporated in the posterolingual crest linking the metaconid and hypoconid. The ectolophid is distinct, without mesoconid. The metalophid fails to close the trigonid basin posteriorly. Enamel on the talonid basin of p4-m3 is smooth.

Fig. 4 Cheek teeth ofPlesiosciurus zhengifrom Tangkou, Fanchang A. l M1/2 (IVPP V 20850.1); B. l M1/2 (holotype, V 20849); C. r M1/2 (V 20850.3); D. r M1/2 (V 20850.4); E. l M3 (V 20850.7); F. r M3 (V 20850.8); G. l dp4 (V 20850.12); H. l p4 (V 20850.14); I. l m1/2 (V 20850.15); J. l m1/2 (V 20850.16); K. r m1/2 (V 20850.19); L. r m1/2 (V 20850.20); M. l m3 (V 20850.23); N. r m3 (V 20850.25); in occlusal view

Discussion The described specimens fi t the diagnosis ofPlesiosciurusby their small size; relatively heavily built cheek teeth; more striking cusps than crests; M1 and M2 having moderately expanded protocone, complete and converging protoloph and metaloph, but lacking protoconule and mesostyle; lower cheek teeth having entoconid completely incorporated in posterolophid, straight ectolophid, but lacking mesoconid and mesostylid; subrhomboidal m1 and m2 having long metalophid, and m3 moderately expanded posteriorly (see Qiu, 2015).

Fig. 5 Scatter diagrams showing length and width of M1/2 and m1/2 ofPlesiosciurus zhengiandP. sinensisfrom China

Plesiosciurus, considered to be a chipmunk or ground squirrel, was de fi ned by Qiu and Lin (1986) based on the material from the Early Miocene Xiacaowan Formation of Sihong. These teeth from Fanchang are similar to the type specimens ofP. sinensisin morphology, but differ in larger size (Fig. 5), having more heavily built dentition, absence of metaconule and presence of stronger connection between the paracone and metacone in M1/2, lack of metaconule and metaloph in M3, and in less anteroposteriorly compressed m1/2 with anterolingual-posterobuccally arranged ectolophid. These differences are indicative of different speci fi c status for the squirrel, which is here proposed asP. zhengisp. nov.

In addition to type specimens, a partial body imprint and fragmentary skeleton with three damaged teeth was collected from the Early/Middle Miocene Shanwang Formation, Linqu, Shandong Province, and published under the namePlesiosciurusaff.P. sinensisby Qiu and Sun (1988). The Linqu cheek teeth fall within the range exhibited by the new species both as to size and pattern, thus they are here referred to the new speciesP. zhengi.

The similarities ofPlesiosciurus zhengitoP. sinensisindicate that the two species were probably closely allied, but their af fi nities remain uncertain. However, the larger size with more heavily built cheek teeth, the absence of metaconule and the presence of stronger connection between paracone and metacone in M1 and M2, and the less anteroposteriorly compressed m1 and m2 are interpreted as derived states forP. zhengi.

(Fig. 6)

Referred specimens Nine cheek teeth (1 P4, 4 M1/2, 2 m1/2, 2 m3), IVPP V 20851.1-9.

Measurements (length × width, in mm) P4, 1.75 × 2.25; M1/2, 2.05 × 2.60, 2.15 × 2.65, 2.30 × 2.75, 2.15 × 2.75; m1/2, 2.40 × 2.45; m3, 2.70 × 2.60.

Fig. 6 Cheek teeth ofSciurotamias wangifrom Tangkou, Fanchang A. l P4 (IVPP V 20851.1); B. l M1/2 (V 20851.2); C. r M1/2 (reversed, V 20851.3); D. l m1/2 (V 20851.6); E. l m3 (V 20851.8); in occlusal view

Description The P4 is worn by water transportation. It is U-shaped in outline of the occlusal surface with undeveloped parastyle but long anteroloph. The protocone is prominent. The protoloph and the metaloph are strong and complete, with the metaloph slightly constricted at the contact with the protocone. A protoconule and a metaconule are absent. A pronounced connection between the paracone and the metacone is present. The anteroloph and posteroloph are complete, but lower and weaker than the protoloph and the metaloph. M1/2 is subquadrate in outline, with a conspicuous and slightly anteroposteriorly expanded protocone. The paracone and the metacone are also strong and more or less the same size. The protoloph and the metaloph are pronounced, with the latter being oblique and constricted buccal of the protocone. The anteroloph and posteroloph are complete, with the posteroloph buccally bulging to join the protocone. A protoconule and a metaconule are absent, but a bulge at the middle part of the metaloph can be observed. There is a tiny mesostyle connected to the paracone. The anterior valley is slightly larger than the posterior one.

The m1/2 is subrhomboidal. As in the upper cheek teeth, it has heavily built cusps and crests. The entoconid, separated from the metaconid by a wide and deep notch, is weakly developed and incorporated in the strong and elevated posterolingual crest. The entoconid corner is curved. There is no mesoconid, but a very tiny mesostylid connected with the entoconid can be seen. The metalophid is low and complete to close the small trigonid basin posteriorly. The anterolophid is prominent and joins the protoconid at the base. The buccal valley is narrow, and the talonid basin is dammed by a low and short ectolophid. The m3 is moderately expanded posteriorly. The entoconid is completely incorporated in the strong posterolingual crest. A low mesostylid, connected to the posterolingual crest and separatedfrom the metaconid by a notch, is distinguishable. There is no distinct mesoconid.

Discussion The described specimens are colored grayish black and with traces of water transportation. They are probably older, coming from a lower level.

Characters of the specimens correspond to the diagnosis ofSciurotamias. These are the prominent cusps and crests, the complete and converging protoloph and metaloph, the lingually constricted metaloph, and the absence of protoconule on M1/2, the merged entoconid with the posterolophid, the curved entoconid corner, the presence of a distinct notch between the metaconid and the posterolingual crest on m1 and m2.Sciurotamiasis a group of ground squirrels endemic to China. Two extant species,S.davidianusandS.forresti, and fi ve fossil species,S.pusillus,S.wangiandS.leilaoensisfrom the Late Miocene,S.praecoxandS.teilhardifrom the Pleistocene are included in the genus (Teilhard, 1940; Zheng, 1993; Qiu, 2002; Wang, 2003; Qiu and Ni, 2006; Qiu et al., 2008).

The FanchangSciurotamiascan be easily distinguished fromS.davidianusby its relatively wider cheek teeth with relatively weaker cusps and lophs, less lingually constricted metaloph, and absence of metaconule on M1 and M2, presence of a complete metalophid and a small mesoconid on m1/2. It shows some resemblance toS.forrestiin relatively wide cheek teeth with less strong cusps and lophs, less constricted metaloph bearing no metaconule on M1 and M2, but differs in larger size, having a tiny mesostyle on M1 and M2, a small mesostylid and a complete metalophid on m1/2. The taxon is larger thanS.pusillusandS. praecoxin size. In addition, it differs from the former in having less constricted metaloph bearing no metaconule on M1 and M2, having complete metalophid and lacking mesoconid on m1/2, and differs from the latter in having stronger cusps and lophs, distinct connection between the paracone and the metacone on M1/2, and lacking mesoconid on m1/2. The main differences between the Fanchang taxon andS. leilaoensisare the relatively wider cheek teeth with stronger cusps and lophs, the less constricted metaloph bearing no metaconule on M1 and M2, and the presence of a tiny mesostylid on m1/2 in the former. Compared withS. teilhardi, it is slightly larger in size with more heavy cusps and lophs, less lingually constricted metaloph on M1 and M2, and indistinct mesoconid on m1/2.

The described specimens are mostly similar to the type specimens ofS. wangiin size, in the absence of protoconule and metaconule, the presence of small mesostyle on M1 and M2, and in having more complete metalophid on m1/2. Minor differences are the stronger cusps and crests, the less lingually constricted metaloph on M1 and M2, and the presence of a tiny mesostylid on m1/2 in the Fanchang specimens. While unlikely that these specimens are completely identical to those ofS. wangi, it is considered inadvisable to create a new species based on the inadequate material and the minor differentiated morphology. Thus, they are referred toS.wangiknown from the Late Miocene of Yunnan (Qiu, 2002; Qiu and Ni, 2006).

(Fig. 7)

Referred specimens Ten cheek teeth (1 P4, 2 M1/2, 1 dp4, 2 p4, 3 m1/2, 1 m3), IVPP V 20852.1-10.

Measurements (length × width, in mm) P4, 1.90 × 2.30; M1/2, 2.10 × 2.50, 2.25 × 2.75; dp4, 1.65 × 1.45; p4, 1.70 × 1.65, 1.85 × 1.80; m1/2, 2.10 × 2.20, 2.25 × 2.55; m3, 2.75 × ―.

Description The P4 is subrectangular in outline of the occlusal surface with a slightly expanded parastyle and short anteroloph. The protocone is high and prominent. The protoloph and the metaloph are complete, and the metaloph is constricted at the contact with the protocone. A protoconule is absent, but a metaconule-like bulge is present. A distinct mesostyle is lacking, but a pronounced connection exists between the paracone and the metacone. The outline of M1/2 is subquadrate. The protocone is conspicuous, high and slightly expanded anteroposteriorly. The metacone is larger than the paracone. The protoloph and the metaloph are strong, with the latter being oblique and lingually constricted. The anteroloph and the posteroloph are complete, lower than the protoloph and the metaloph. A protoconule is absent, but a small metaconule is present. A tiny mesostyle connected to the paracone can be observed. The central valley is larger than the anterior and the posterior valleys.

The dp4 is distinctly narrower anteriorly than posteriorly with the more posteriorly situated protoconid separated the metaconid by a narrow fi ssure. The entoconid is completely incorporated in the prominent and elevated posterolophid. A mesoconid and a mesostylid are absent. The p4 is similar to the dp4 in shape and structure, but larger in size with stronger cusps and crests. A small mesoconid is present in one specimen. The m1/2 is subrhomboidal with the entoconid incorporated in the posterolingual crest. The entoconid corner is curved. A mesoconid and a mesostylid are missing. The metalophid is long and closes the small trigonid basin posteriorly. The anterolophid is complete and joins the protoconid at the base. The posterolingual crest is elevated, joining the hypoconid at its apex and separated fromthe metaconid by a notch. The buccal valley is narrow and shallow. The smooth talonid basin is dammed by a low and anterolingual-posterobuccally arranged ectolophid. The m3 is moderately expanded posteriorly. The entoconid is incorporated in the strong posterolingual crest, which is connected to the hypoconid and separated from the metaconid by a notch. The metalophid fails to join the metaconid. Enamel on the talonid basin is not rugged.

Fig. 7 Cheek teeth ofSciurotamias teilhardifrom Tangkou, Fanchang A. r P4 (reversed, IVPP V 20852.1); B. l M1/2 (V 20852.2); C. l M1/2 (V 20852.3); D. r dp4 (reversed, V 20852.4); E. r p4 (reversed, V 20852.5); F. l m1/2 (V 20852.7); G. l m1/2 (V 20852.8); H. r m3 (reversed, V 20852.10); in occlusal view

Discussion The specimens described are colored yellowish red and show no sign of wear by water, differing from those ofSciurotamias wangi. They are probably from an upper level.

These specimens exhibit a suite of characters that are highly diagnostic for the genusSciurotamias. They cannot be referred toS. wangifrom the same fissure, not only because of their slightly smaller size with less heavy cusps and crests, and the distinctly lingually constricted metaloph on M1 and M2, but also due to the different color of the specimens. Rather, they fi t the diagnosis ofS.teilhardiZheng, 1993 in size, by the presence of distinctly lingually constricted metaloph and small mesostyle, the lack of protoconule and developed metaconule on M1 and M2, and the complete incorporation of the entoconid in an elevated posterolophid and the curved entoconid corner on m1 and m2. Minor differences of these teeth from the original specimens (see Zheng, 1993) are the more complete metalophid, the indistinct mesoconid and less deep notch between the metaconid and the posterolingual crest on m1 and m2. The differences mentioned, however, are of variable characters in the type material. Thus, these specimens are temporarily referred toS. teilhardi.

Type speciesPseudoratufa wanensissp. nov.

Etymology From Greekpseud, “false”, alluding to the difference of the new genus fromRatufa, a living ratu fi n genus.

Diagnosis Relatively large-sized squirrels with heavily built and unilaterally hyposodont cheek teeth. P4-M2 with perfectly rounded corners; P4 relatively small, without anterostyle; M1/2 with distinctly anteroposteriorly elongated protocone, strong, lingually constricted and approximately parallell arrangement of protoloph and metaloph bearing no protoconule and metaconule, pronounced protolophule, and anteroloph and posteroloph incorporated in the protocone lingually and joining the paracone and metacone buccally to circle the occlusal surface. The p4 small, without anteroconid, with entoconid incorporated in the posterolingual crest to circle the talonid basin together with the protoconid, hypoconid, metaconid and the ectolophid. Short and thick secondary crests from the protoloph and metaloph well developed on the central valley in M1 and M2.

Differential diagnosis The dental pattern ofPseudoratufais similar to that ofRatufain large size, in P4-M2 having relatively low cusps and crests, crest-like protocone, approximately parallel arrangement of protoloph and metaloph, in M1 and M2 having perfectly rounded corners, conspicuous protolophule, well developed secondary crests on the central valley, and strong crest formed by the anteroloph, posteroloph, protocone, paracone and metacone encircling the occlusal surface. The main differences betweenPseudoratufaandRatufaare: 1)the cheek teeth are distinctly unilaterally hyposodont inPseudoratufa; 2) the cusps and crests are relatively higher inPseudoratufathan inRatufa; 3) the P4 and p4 are markedly smaller relative to M1 inPseudoratufathan inRatufa; 4) the P4 lacks parastyle inPseudoratufa,but an anteriorly expanded parastyle exists inRatufa; 5) the protoloph and metaloph are complete inPseudoratufa, but strongly constricted lingually or unconnected with the protocone inRatufa; 6) the anteroloph and posteroloph in M1/2 are distinctly weaker and lower than the protoloph and metaloph inPseudoratufa, but they are almost equal to the protoloph and metaloph in both thickness and height inRatufa.

(Fig. 8)

EtymologyWan, the abbreviation for Anhui Province in Chinese. Named after Anhui, where this new species was found.

Holotype Left M1/2 (IVPP V 20853).

Paratypes Five cheek teeth (1 P4, 3 M1/2s, 1 p4), V 20854.1-5.

Measurements (length × width, in mm) P4, 1.70 × 2.20; M1/2, 2.40 × 3.25, 2.45 × 3.15, 3.10 × 3.75, 2.45 ×―; p4, 2.05 × 1.80.

Diagnosis Same as for the genus.

Description The cheek teeth are heavily built and unilaterally hyposodont, with the lingual crown height distinctly higher than that of the buccal side on the P4 and M1/2. Their occlusal surfaces are subrounded in outline. The P4 is rather small relative to the molars. A parastyle is absent. The protocone is high and pronounced. The paracone is distinctly larger than the metacone. The protoloph and the metaloph are strong and high, nearly parallel in arrangement, but slightly converged toward the protocone lingually. The anteroloph and the posteroloph are complete, but distinctly lower and weaker than the protoloph and the metaloph. There is no sign of protoconule and metaconule. A distinct mesostyle is also absent. The secondary crests in the central valley are undeveloped, except for a spur from the middle part of the metaloph. The M1/2 has conspicuous cusps, relatively low crests, and perfectly rounded corners. The protocone is crest-like and anteroposteriorly elongated. The paracone is distinctly larger and higher than the metacone. The protoloph and metaloph are strong, but constricted just buccal of the protocone, and with the protoloph interrupted at the middle part. They are approximately parallel and connect with the protocone. There is no protoconule and metaconule. A distinct mesostyle is also absent. The protolophule is pronounced, extending buccally to one third of the central valley. There is a low connection between the paracone and the metacone. The anteroloph and the posteroloph are complete, but lower and weaker than the protoloph and metaloph. Both are incorporated in the elongated protocone lingually, and connected with the paracone and metacone buccally, to circle the occlusal surface. Enamel on the central valley is crenulated, several short and thick secondary crests from the protocone and metacone are developed as well as the protolophule and the mesostyle crest.

Fig. 8 Cheek teeth ofPseudoratufa wanensisfrom Tangkou, Fanchang A. r P4 (IVPP V 20854.1); B. l M1/2 (holotype, V 20853); C. l M1/2 (V 20854.3); D. r M1/2 (V 20854.2); E. r p4 (V 20854.5); in occlusal view

The p4 is subquadrate and narrower anteriorly than posteriorly. The protoconid and the metaconid are nearly equal in size. They are situated closely and separated by a very narrow and shallow valley. An anteroconid is absent. The hypoconid is prominent and extends posterobuccally. The entoconid is incorporated in the posterolingual crest connected with the metaconid and the hypoconid. The entoconid corner is curved. A mesoconid and a mesostylid are lacking. The ectolophid is thick, connecting the protoconid and the hypoconid. It joins the posterolingual crest via the protoconid and the hypoconid to circle the talonid basin. The buccal valley is wide and shallow.

Discussion The squirrel represented by the specimens is characterized by its large size with heavily built cheek teeth, relatively low cusps and crests, anteroposteriorly elongated protocone, and approximately parallel arrangement of the protoloph and the metaloph bearing no protoconule and metaconule on P4-M2. Characters of these teeth clearly demonstrate that it is a tree squirrel. By a combination of features, this squirrel is easily distinguished from known sciurines, such asSciurus,Oriensciurus,Tamiops,Shuanggouia,Atlantoxerus,Tamias,Plesiosciurus,Sinotamias,Prospermophilus, andPalaeosciurus, etc. These features are the unilaterally hyposodont cheek teeth, the distinctly smaller P4 and p4 relative to the molars, the perfectly rounded corners of P4-M2, the crest-like protocone, the complete and nearly parallel arrangement of protoloph and metaloph, the absence of protoconule and metaconule, the presence of pronounced protolophule, the anteroloph and posteroloph incorporated in the protocone lingually and joining the paracone and metacone buccally to circle the occlusal surface in M1 and M2, the entoconid incorporated in the posterolingual crest, the prominent posterolingual crest and the ectolophid enclosing the talonid basin with the protoconid, metaconid and hypoconid in p4, and the development of short and thick secondary crests fromthe protocone and the metacone on the central valley in M1 and M2. Therefore, the described specimens are designated to a new genus and species, in spite of the poor material available.

The similarities of the new genus toRatufain dental morphology appear to imply that the two genera have close af fi nities. It is rather unlikely thatPseudoratufawas a close descendant ofRatufa, or vice versa. There is a strong possibility, however, that the two genera can be included in the same tribe Ratu fi ni.

Teeth of this taxon are colored grayish black or brown, and show wear by water. They are probably from a lower level. Among the materials from the fi ssure, those of hominoids,Diatomysand beavers also show a similar color and wear characterstics. Judging by the relatively dark color of the teeth and trace of rolling, these remains are probably from similar deposits of an older stratigraphic interval that contains the same faunal association. If this assumption is correct, it would be indicative of existence of forest biotopes in this district during the earlier Miocene, because the hominoids re fl ect a forest habitat, which may also be true also forDiatomysandPseudoratufa. In addition, beavers often require open water.

3 Conclusion

The sciurids from the Tangkou fissure deposits are included in five genera and six species, belonging to four tribes in the subfamily Sciurinae, i.e.Sciurussp. of Sciurini,Tamiassp. andPlesiosciurus zhengiof Tamiini,Sciurotamias wangiandS. teilhardiof Marmotini, andPseudoratufa wanensisof Ratu fi ni. The assemblage contains members commonly known in Chinese late Cenozoic faunas, but also includes an intriguing element,Pseudoratufa, which may represent a new comer of the tribe Ratu fi ni.

The presence of these sciurids indicates a late Cenozoic age for the fi ssure fi llings. Since the material described is from a sampling throughout the 4 levels of the deposits, the sample is a mixed assemblage with elements representing a rather long interval probably spanning Early Miocene to Pleistocene. For this small association of sciurids from this fissure it is at present impossible to recognize contemporaries, and the age of these taxa is difficult to precisely assess because of the difficult fissure stratigraphy, the poor control in sampling and the inadequate materials. Nevertheless, judging from the morphology, the traces of transportation, and the coloration of fossils, thePlesiosciurusandPseudoratufaare relatively old, probably from the Early Miocene or Middle Miocene; theSciurotamias teilhardiis younger than theS. wangi, which are roughly coeval with populations from Yunnan (Late Miocene) and Wushan (Early Pleistocene), respectively (Zheng, 1993; Qiu and Ni, 2006); theSciurusandTamiasmay be younger than Late Miocene.

The intriguing ratu fi nPseudoratufais probably in the same association as the hominoid,Diatomysand beavers, inferred by the fossil color and roll traces in the materials. Their cooccurrence seems to indicate existence of a forest biotope in the earlier Miocene.

Acknowledgements The authors would like to express their gratitude to Dr. X M Wang from the Natural History Museum of Los Angeles County, USA, Dr. L J Flynn from Harvard University, USA for commenting on the manuscript and English content. Many thanks are also due to Miss H W Si and Mr. W D Zhang from IVPP for the photographs.

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安徽繁昌晚新生代裂隙堆积中的松鼠类化石

邱铸鼎 金昌柱

(中国科学院古脊椎动物与古人类研究所 北京 100044)

描述了安徽繁昌癞痢山塘口晚新生代裂隙堆积物中发现的松鼠类材料。化石代表松鼠亚科的4个族，共有5属6种，其中包括一个新属和两个新种，即树松鼠族的Sciurussp., 花鼠族的Tamiassp.和Plesiosciurus zhengisp. nov., 旱獭族的Sciurotamias wangiQiu, 2002和S. teilhardiZheng, 1993, 以及巨松鼠族的Pseudoratufa wanensisgen. et sp. nov.。所研究的材料系混合地采自同一裂隙堆积的4个不同层位，化石的组分可能代表从早中新世至更新世的不同时段。繁昌的这一松鼠组合具有中国中南部晚新生代松鼠动物群的特色，并含有稀奇的Pseudoratufa属。该新属的牙齿形态显示了其树栖松鼠的特征，而且可以归入甚为稀有的巨松鼠族。其遗骸具有与该地点发现的古猿、硅藻鼠和河狸类化石相似的石化和堆积过程，似乎表明这些动物属于时代相同或较接近的群体，它们的共存也说明了繁昌地区在中新世时有过相对湿润的森林生境。

安徽繁昌，晚新生代，裂隙堆积，松鼠科

Q915.873

A 文章标号：1000-3118(2016)04-0286-16

2015-10-15

Qiu Z D, Jin C Z, 2016. Sciurid remains from the Late Cenozoic fissure-fillings of Fanchang, Anhui, China. Vertebrata PalAsiatica, 54(4): 286-301

国家自然科学基金(批准号：41430102)资助。