Ochotona valerotae, Erbajeva & Montuire & Chaline, 2001

Erbajeva, Margarita A., Montuire, Sophie & Chaline, Jean, 2001, New ochotonids (Lagomorpha) from the Pleistocene of France, Geodiversitas 23 (3), pp. 395-409 : 397-401

Ochotona valerotae n. sp. ( Figs 1 ; 2 ; Table 1)

HOLOTYPE. — Left mandibular ramus with p3-m3, without incisor, angular process and condyle, University of Burgundy (Val-8226) ( Figs 1 A-D; 2).

TYPE LOCALITY. — Les Valerots, level 2, Côte-d’Or, France.

A B

ETYMOLOGY. — valerotae : found in the Les Valerots karst filling, Côte-d’Or, France.

HYPODIGM. — In addition to holotype: 1 fragment of right mandibular ramus with m1-m3 (Val-8013); 1 fragment of right maxilla with P3 (Val-8014); isolated teeth dex: P4-1 and M1-1 (Val-8013a,b).

HORIZON, LOCALITY AND GEOLOGICAL AGE. — Les Valerots, breccia, level 2, lower Pleistocene, Bavelian age.

DIAGNOSIS. — A small ochotonid. The occlusal surface of p3 is triangular ( Fig. 1A ), pm3 is distinctly longer than it is wide (length 1.2, width 1.1), its anteroconid is relatively narrow and elongate with a rather sharp anterior margin; the posteroconid is wide, having a straightened lingual margin with a shallow, cement-free groove. The confluence between the anteroconid and posteroconid of this tooth is smaller ( Table 1). The alveolar length of the lower cheek teeth (p3-m3) is 7.2.

DIFFERENTIAL DIAGNOSIS. — A relatively small ochotonid similar to the pikas of the “ pusilla ” group. It differs from all fossil taxa of Ochotona pusilla in its p3

A structure: in its elongate anteroconid and narrower posteroconid than in all extinct pikas of the “ pusilla ” group. It differs from extant Ochotona pusilla in its distinctively small size, in its somewhat shorter and mandibular ramus and in its p3 structure being slightly longer and narrower than the p3 of Ochotona pusilla . Ochotona valerotae n. sp. differs from all European pikas: from Ochotona polonica Sych, 1980 (Zamkowa Dolna, Poland) and Ochotona sp. from Maritsa ( Greece) in the smaller p3 and in its narrower and elongate anteroconid which has a small confluence with the posteroconid in contrast to those of the above-mentioned pikas ( Table 1).

MORPHOLOGICAL DESCRIPTION

The studied specimens are housed in the collections of the University of Burgundy, UMR

CNRS BIOGEOSCIENCES 5561. The mandibular ramus is low and rather robust while the diastema is short ( Table 1). The lower incisor extends posteriorly along the ventral border approximately in a line below p4 with a rather well-developed tubercle on the lingual side of the mandibular ramus at the root end of the incisor ( Fig. 2A, B ). The outer surface of lower jaw is flattened. Almost all of the teeth are well-preserved in the specimens. The first lower premolar (p3) has a relatively large anteroconid with the anterointernal side being longer than the antero-external one; its postero-internal and postero-external sides are of the same length ( Fig. 1A ). It has two persistent external folds and one internal fold (flexids). The latter is directed towards the longitudinal axis of the tooth and turned backward (posteriorly). The lower molariform teeth are similar in shape to those of all Ochotona species. P4 is shorter than m1 and m2. Its trigonid is narrower than the talonid. However m1 and m2 have different proportions: their trigonids are distinctly wider than the talonids. m3 consists of a single narrow column. The enamel of p4-m3 is thicker on the outer and on the posterior walls of the trigonids and talonids.

The occlusal outline of P3 is trapezoidal. It is about two thirds narrower anteriorly than posteriorly ( Fig. 1B ; Table 1). Its deep, cement-filled, antero-labial fold begins and end at almost the same level of tooth width. The hypostria is short and filled with thin cement. P4 and M1 are similar in shape, the enamel is thicker on the anterior and outer walls of the teeth. Their hypostriae are deep but are not distinguishable on the outer margin of the tooth ( Fig. 1C, D ).

COMPARISONS

The size and general structures of the teeth and mandibles allow us to compare Ochotona valerotae n. sp. with all small extant species of Ochotona and with extinct pikas from Europe and Asia. Ochotona valerotae n. sp. is slightly larger than extant Ochotona hyperborea Pallas, 1811 (all small subspecies), as well as Ochotona thomasi and different species of the “ thibetana ” group: alveolar and coronar lengths of p3-m3 of Ochotona

= valerotae n. sp. are respectively 7.2 and 6.5 compared with 7.0 and 6.0 (mean value) for Ochotona hyperborea hyperborea from Kolyma ( Russia), 6.4 and 5.6 for Ochotona thibetana Milne-Edwards, 1871 , and 6.3 and 5.6 for Ochotona thomasi Argyropoulo, 1948 . The new taxon described here differs from the species referred to above in its rather robust lower jaw and its slightly narrower p3 anteroconid, of which the average length and width are respectively 0.6 × 0.65 for O. hyperborea ; 0.6 × 0.57 for O. thomasi ; 0.65 × 0.6 for O. thibetana and 0.6 × 0.54 for Ochotona valerotae n. sp. Moreover, O. thibetana and O. thomasi are characterized by the anteroconid of p3 being completely separated from the posteroconid. As a rule O. hyperborea has a p3 with almost completely separated antero- and posteroconids, but some specimens from Kamchatka, the extreme East of Russia, have p3 teeth with wide confluences between these conids.

The mandibular rami of the extant species mentioned above are slighter than that of Ochotona from Les Valerots: average mandibular width and height at p4 are 3.2 and 4.4 for Ochotona valerotae n. sp.; 3.0 and 4.3 for O. hyperborea ; 2.1 and 3.6 for O. thomasi ; 2.3 and 3.9 for O. thibetana . The other recent species of Ochotona , known mainly from Asia, are much larger than the Les Valerots pika.

Ochotona valerotae n. sp. more closely resembles Ochotona pusilla in its small size and in having wide confluences between the anteroconid and posteroconid of p3. However it is distinguished from extant Ochotona pusilla in its smaller size, its mandibular ramus and its p3 structures ( Table 1; Fig. 1A ). p3 of Ochotona pusilla is characterized by a small anteroconid and wide posteroconid, the internal margin of the latter sloping backwards and outwards. The occlusal outline of this tooth is trapezoidal, its antero-internal and anteroexternal folds are not as deep as those of Ochotona valerotae n. sp ( Fig. 1E ).

All extinct taxa of Ochotona pusilla and of Ochotona near to Ochotona pusilla differ from Ochotona valerotae n. sp. in the structure of p3 having a wide confluence between anteroconid and posteroconid as well as in the wider posteroconid. Ochotona from Les Valerots is almost the same size as Ochotona sp. from Schernfeld in Germany ( Dehm 1962), which was defined as a pika near to Ochotona pusilla . The latter is poorly documented, no figures of teeth are given, and it is impossible to compare it with pika from France. Ochotona valerotae n. sp. differs from the small pika of Emirkaya ( Turkey) ( Montuire et al. 1994) in its large anteroconid and in the narrower posteroconid of p3. The pika from the Les Valerots site differs from Ochotona polonica known from the Zamkowa Dolna locality both in its smaller size and the persistent confluence of the anteroconid and posteroconid of p3. Moreover, the p3 anteroconid of Ochotona polonica is rhombus-shaped which is quite different from the p3 of Ochotona valerotae n. sp. The rhombus feature is characteristic of the p3 of the pika from the Maritsa 1 locality. These latter two localities are geologically older than the Les Valerots site. The p3 structure of Ochotona valerotae n. sp. resembles the p3 of Ochotona sp. from the Chembakchino locality in Western Siberia and is probably of the same geological age. According to Smirnov et al. (1986), the Chembakchino locality contains small mammalian fauna similar to the fauna from Les Valerots. However, pikas from these two localities differ slightly in having another type of p3. The West Siberian pika differs from the Les Valerots species in that its p3 has narrower confluences between its anteroconid and posteroconid, as well as in having a slightly smaller anteroconid on this tooth ( Fig. 1F ).

SYSTEMATICREMARKS

The small ochotonid from the Les Valerots karst filling at Nuits-Saint-Georges, Côte-d’Or, differs from all extant and extinct pikas of the world in the morphological peculiarities of its lower third premolar and in its mandible ramus structures and its size. The morphological features given above in the diagnosis and in the comparative sections allow us to represent the new taxon of small pika – Ochotona valerotae n. sp. It is characterized by apomorphic characters: small size; shorter confluences than Ochotona pusilla between the anteroconid and posteroconid of p3 ( Table 1); straight inner margin of the posteroconid of p3. The following features are plesiomorphic: elongate anteroconid and posteroconid; rather deep antero-external and antero-internal folds on p3; presence of enamel on the inner and posterior walls of trigonids and talonids of p4-m2.

The phylogeny and relationships of small Eurasian ochotonids are still unclearly known because of the paucity of data on fossil taxa. From analysis of the morphology of fossil taxa from Europe and Asia, the main evolutionary trend of ochotonids can be characterized as an increase in size, development of different types of p3 anteroconid and considerable variability in the p3 anteroconid and posteroconid confluence.

On the strength of the related morphological characters mentioned above, it may be suggested that Ochotona valerotae n. sp., Ochotona sp. from Chembakchino (western Siberia) and ancient fossil taxa of Ochotona pusilla could be derived from the ancestral form distributed in Asia at the end of the Pliocene, and it may be assumed that the ancestors of these species bore greater resemblance to pikas from Les Valerots and Chembakchino.

MIDDLE AND LATE PLEISTOCENE OCHOTONA PUSILLA

Fossil remains of Ochotona pusilla Pallas are quite well known in France ( Chaline 1969, 1972). The first information about this species arose in the last century when Desnoyers (1842) described a small mammalian fauna from Montmorency including Ochotona pusilla and Lemmus lemmus .

Excavations by archaeologists in the localities of La Fage (upper middle Pleistocene) and Baume de Gigny (Upper Pleistocene) in the last decades have yielded a large number of well-preserved, small mammal remains ( Chaline & Brochet 1989) including numerous fossil remnants of ochotonids.

THE LA FAGE KARST FILLING

The La Fage karst filling near Noailles (Corrèze) has yielded a very rich mammal fauna:

– rhinoceroses and proboscideans ( Guérin 1973; Beden & Guérin 1975): Coelodonta antiquitatis , Dicerorhinus hemitoechus , Dicerorhinus mercki , Mammuthus aff. Trogontherii;

– deer, cattle, goats, mountain goats, pigs and horses ( Bouchud 1972): Cervus cf. elaphus , Dama cf. clactoniana, Capreolus capreolus , Rangifer sp. , Megaceros giganteus , Equus cf. steinheimensis, Bison cf. shoetensacki, Sus scrofa, Capra ibex , Rupicapra rupicapra ;

– carnivores ( Ballésio 1975; Bonifay 1975; Hugueney 1975; Martin 1975): Canis lupus , Vulpes vulpes , Ursus deningeri , Mustela nivalis , Mustela erminea , Meles meles , Gulo gulo , Mustela (Putorius) eversmanni , Panthera (Leo) spelaea ;

– insectivores ( Jammot 1973): Erinaceus davidi , Talpa cf. europaea , Sorex kennardi , Sorex minutus , Neomys fodiens , Crocidura zorzii , Crocidura sp. , Macroneomys cf. brachygnathus;

- bats ( Mein 1975): Myotis bechsteini , Myotis myotis , Plecotus auritus ;

– rodents ( Chaline 1972b): Citellus major , Marmota marmota mesostyla , Eliomys quercinus , Glis glis , Allocricetus bursae correzensis , Microtus arvalis-agrestis , Microtus gregalis martelensis , Microtus malei noaillensis , Terricola subterraneus , Arvicola terrestris , Clethrionomys glareolus , Dicrostonyx torquatus , Lemmus lemmus , Pliomys lenki , Apodemus sylvaticus ;

– hares and rabbits ( Petter 1973; Chaline 1975a, b): Lepus capensis , Oryctolagus cuniculus , Ochotona pusilla .

To these must be added amphibians, reptiles ( Rage 1972) and 104 species of birds (Mourer- Chauviré 1975). The stratigraphy was resumed by Debard (1973).

GIGNY CAVE

The Gigny site is located on a limestone plateau on the western side of the Jura range ( France). The Würm glaciation halted some 10 km East of Gigny. Throughout the glacial cycle, the Gigny site was subjected to a highly disruptive periglacial environment ( Campy 1982; Campy et al. 1989; Campy & Chaline 1993).

THE GIGNY SEQUENCE

Excavation of the Gigny cave filling yielded a 28- level stratigraphic record, divided into five sedimentary units ( Campy et al. 1989, 1990; Campy & Chaline 1993).

The site has been the focus of much research into stratigraphy, chronology, palaeontology and archaeology. The sequence has yielded plentiful fossil remains: 69 species of birds (Mourer- Chauviré 1989); large mammals – 15 species of carnivores, 12 species of artiodactyls, two species of perissodactyls, one species of proboscidian – and micromammals – two species of lagomorphs, seven species of insectivores ( Jammot 1989) and 12 species of rodents ( Chaline & Brochet 1989; Brunet-Lecomte et al. 1994).

Figures

FIG. 1. — Ochotonid tooth structure (occlusal view); A-D, Ochotona valerotae n. sp.; A, p3-m3 sin. (Val-8226); B, P3 dex (Val-8014); C, P4 dex (Val-8013a); D, M1 dex (Val-8013b); E, Ochotona pusilla angustifrons Argyropulo, p3 dex; F, Ochotona sp., p3 dex (Chembakchino, western Siberia). Scale bar: 1 mm.

FIG. 2. — Ochotona valerotae n. sp., mandible dex (Val-8226), incomplete mandible views; A, labial view; B, lingual view; C, occlusal surface; D, under side. Scale bar: 5 mm.