Varanus sp.

Rage, Jean-Claude & Bailon, Salvador, 2005, Amphibians and squamate reptiles from the late early Miocene (MN 4) of Béon 1 (Montréal-du-Gers, southwestern France), Geodiversitas 27 (3), pp. 413-441 : 425-426

Varanus sp. ( Fig. 5 )

MATERIAL EXAMINED. — 1 axis (Béon 2004 LT 53), 2 trunk (Béon 2004 LT 54, 55) and 1 sacral (Béon 2004 LT 56) vertebrae.

COMMENTS

The referral of these vertebrae to the Varanidae is based on the following features: axis elongate and provided with a robust hypapophysis; extremity of the hypapophysis somewhat expanded and bearing two articular surfaces; trunk vertebrae with a well demarcated pars tectiformis on the anterior part of the neural arch; ventral surface of centrum widened anteriorly and convex ventrally in cross section; condyle strongly depressed, its articular surface facing mainly dorsally (Hoffstetter 1969; Hoffstetter & Gasc 1969; Estes 1983).

In Western Europe, two varanid genera have been reported from the Miocene: Iberovaranus Hoffstetter, 1969 , from the late early, and perh a p s e a r l y m i d d l e M i o c e n e o f t h e I b e r i a n Peninsula (Hoffstetter 1969; Antunes & Rage 1 9 7 4; R a g e & A u g é 1 9 9 3) a n d t h e e x t a n t Varanus known from the early Miocene (MN 4, see below) to the early/late Pliocene (Hoffstetter 1969; Estes 1983; Bailon 1991, 1992; Rage & Augé 1993). Iberovaranus differs from Varanus in having more elongate neural arches, narrower condyles, and less pronounced precondylar constriction (Hoffstetter 1969). The vertebrae from Béon 1 show the typical morphology of Varanus ; more specifically, the precondylar constriction is very characteristic.

Remains of Varanus found in the Miocene of Western Europe have been either allocated to Varanus hofmanni Roger, 1898 (MN 6, middle Miocene of Germany; Roger 1898; Hoffstetter 1969) or doubtfully referred to this species (early to late Miocene of Spain and France; Hoffstetter 1969; Alférez Delgado & Brea López 1981). But these varanids have not been really studied.

Specimens from Béon 1 are approximately similar to those from Artenay (early part of MN 4, France) that represent the oldest Varanus in Europe (see below). However, trunk vertebrae from Artenay are slightly larger than those from Béon 1 and anterior trunk vertebrae have slightly less concave subcentral ridges in ventral aspect.

The paucity of the material does not permit us to draw definite conclusions. Pending a revision of Varanus hofmanni , the specimens from Béon 1 are referred to as Varanus sp.

REMARKS ON THE OLDEST RECORDS OF VARANUS Varanus sp. from Béon 1 is one of the oldest representatives of the genus in Europe. Artenay (MN 4, France), that is slightly older than Béon 1, produced the earliest European Varanus . Hoffstetter (1969) reported that the latter appears to be morphologically close to the vertebrae from Vieux-Collonges (MN 4/5, France) and La Grive (MN 7+8, France) referred to as Varanus cf. V. hofmanni . Varanus was also reported (as V.? hofmanni ) from Córcoles, Spain, a locality that is approximately contemporaneous with Béon 1 ( Alférez Delgado & Brea López 1981); but it should be noted that the identification of the Spanish fossil rests on a single caudal vertebra. Since no other Varanus has been reported from the Orleanian of the Iberian Peninsula, while Iberovaranus is known from this stage and in this area, it may be entertained whether the specimen from Córcoles really belongs to Varanus .

In Africa also, Varanus is present in the early Miocene. According to Hoffstetter (1969) and Estes (1983), the genus is present in the early Miocene (without precision) of Kenya, but Clos (1995) and Rage (2003a) reported Varanus from levels that may be equated with the European Agenian or Orleanian (approximately the Aquitanian and Burdigalian in terms of international reference stages). The oldest African locality that yielded Varanus is Songhor ( Kenya). According to Clos (1995), the specimens from this locality are reminiscent of V. rusingensis Clos, 1995 , from Rusinga ( Kenya), a slightly younger locality. Songhor is located at about 19.5- 19.9 Ma; therefore, according to Pickford & Senut (1999) it would correlate to the upper part of the European zone MN 2, i.e. to the late Agenian (= late Aquitanian).

In Australia, a varanid (probably Varanus ) was present as early as the latest Oligocene in the Hiatus A locality (Scanlon pers. comm.). That Australian fossil, if really Varanus , is the earliest known representative of the genus. Since it seems doubtful that Varanus originated in Australia, this suggests that older Varanus are probably present in Asia.

But, in Asia, all pre-Miocene reports of Varanus are questionable. The genus was doubtfully reported from the middle Eocene (now regarded early Eocene; Averianov & Godinot 1998) of Kyrgyzstan by Reshetov et al. (1978). But, this genus only appears in a faunal list, without any description. Zerova & Ckhikvadze (1986) rightly questioned this report; they identified the fossil as a “vertebra of a large lizard, probably related to Varanidae ”. Alifanov (1993) reported Varanus sp. from the middle Eocene and early Oligocene of Mongolia. Figures of the dorsal and ventral faces of a vertebra from the middle Eocene are given but the specimens from the early Oligocene are not described. The figures do not demonstrate that the fossil from the Eocene belongs to Varanus . Therefore, the oldest confirmed remains of Varanus from Asia are vertebrae of V. pronini Zerova & Ckhikvadze, 1986 , from the middle Miocene (without more precision) of Kazakhstan ( Zerova & Ckhikvadze 1986).

Figures

FIG. 5. — Varanus sp., trunk vertebra (Béon 2004 LT 54), in anterior (a), dorsal (d), left lateral (l), posterior (p), and ventral (v) views. Scale bar: 5 mm.