The find of fossil vertebrate remains in amber is rather rare, even in abundant and rich Cainozoic ambers. Four classes occur: Mammalia, Amphibia, Aves and Reptilia. However, only these two last classes are known in Mesozoic ambers, represented by isolated feathers of birds or dinosaurs or by fragments of skin.

Besides the putative feathered dinosaurs mentioned above, the fossilization of reptiles in amber is extremely rare. Few specimens preserved in complete or sub-complete form (skeleton and skin) were described from Tertiary ambers: some lizards of the genus Anolis in Oligocene/Miocene Mexican and Dominican ambers [4], [6] and [15], a gecko of the genus Sphaerodactylus in the Dominican amber [2], and a fossil lizard genus, Succinilacerta, in the Eocene Baltic amber [3]. Incomplete remains of reptiles were found more recently in Cretaceous ambers. Arnold et al. [1] described the skin and claws of a hind limb attributed to a fossil lizard genus Baabdasaurus in the Neocomian Lebanese amber, and fragments of an undetermined reptile skin are figured in the Albian/Cenomanian amber of Myanmar [5]. Thus the skin discovered in Charente-Maritime is the oldest occurrence of such a material in amber for Europe.

The amber containing the vertebrate remains described herein was excavated from the deposit of Archingeay–Les Nouillers, in the Charente-Maritime region (southwestern France), 30 km east from Rochefort-sur-Mer, and already provided numerous arthropods, mainly insects [10] and [11]. It is derived from Cretaceous estuarine and coastal sand, which is erosive on marine limestone of Tithonian age [7]. The basal part of the sand yields lignitic and clayey lenses with fossil plants and numerous amber pieces, and was dated as Uppermost Albian (100 Myr) by a palynological study [8].

The botanical source of this amber is thought to be araucarian (Agathoxylon) based on both the analysis of the fossil wood remains and an infrared spectroscopic analysis of the amber. However, other conifers of the fossil family Cheirolepidiaceae (Brachyoxylon, Protopodocarpoxylon) could also have contributed to the resin production [10].

Two fragments of skin were initially preserved in a single piece of amber together with 11 arthropods (five Strepsiptera, three Diptera, one Thysanoptera, and two Acari). The amber piece was fragmented in order to have a better view of all inclusions. Remains of skin are now referenced as MNHN ARC 237.1 and MNHN ARC 237.5 and deposited in the ‘Département Histoire de la Terre’ of the ‘Muséum national d’histoire naturelle’ in Paris.

Description. Fragment MNHN ARC 237.5 (Fig. 1) is 5.7 mm in its biggest length and 2.7 mm in its biggest width. Scales are present but translucent so that only their imprints are clearly visible, showing 29 regular lines disposed in diagonal. A 0.04-mm space separates each line, whereas imprints of a single line are joined. All imprints are of equal size, 0.25 × 0.15 mm, and are of rhomboid form, with opposite angles of about 70°. A weak bulge can be distinguished in some imprints by varying the light, which corresponds to the scales.

The second fragment (MNHN ARC 237.1) is smaller, 3.4 × 2.5 mm in size, and its structure is better visible. Scales are clearly distinct, three-dimensionally preserved, showing their overlapping disposition, and a tiny scale is visible between the larger ones (Fig. 2).

Discussion . Both fragments are fossilized in a same piece of amber and probably originate from a single individual. The fragmentary nature of the material limits putative conclusions about the systematic position of this fossil. However, the structures that can be observed suggest a reptile. The preservation in two fragments could be interpreted as sloughing remains.

The structure of this skin is clearly distinct from that described in the Lebanese amber and attributed to a lizard of the group Autarchoglossa [1]. Scales on the Lebanese specimen are of variable size, rectangular on tail and more rhomboid on the hind limb. The undetermined reptile skin figured by Grimaldi et al. [5 (fig. 14d)] in the Albian amber of Myanmar is much more similar: scales are not clearly visible, but their imprints are disposed in diagonal lines, the main difference with the skin of France being that imprints are more rectangular and are of variable size – reality or artefact due to the elongation of the skin by resin flow?

Nevertheless, according to the structure and the size of the scale imprints on the sloughing, the reptile that lost these skin pieces was probably a small-size lizard or snake. Beside this, in the fossil record of southwestern France, only few small squamates are known by skeleton remains in the contemporaneous Late Albian–Early Cenomanian series. No lizard or snake taxa occur in the Late Albian, but several Early Cenomanian outcrops yielding assemblages of vertebrate microremains have been discovered in the region of Charentes during the last twenty years, and most of them contain vertebrae of the aquatic coastal snake Simoliophis. That is the case for the quarry of Archingeay–Les Nouillers, which has provided the amber with the skin remains under study. In this quarry, the Upper Albian lignitic sand yielding the amber is located about 10 m below the Lowermost Cenomanian shelly sand yielding the vertebrae of Simoliophis [16]. Simoliophis is the single squamate known in the youngest Cenomanian strata from western France [9] and [17] and it extinguished in the Early Late Cenomanian, during which the aquatic coastal lizard Carentonosaurus mineaui appeared [13]. However, Rage and Néraudeau [13] also mentioned two vertebrae possibly attributed to Carentonosaurus in the Early Cenomanian of Charente-Maritime (Les Renardières quarry), although this material is too poorly preserved for a precise attribution.

Finally, the reptile skin remains from the Late Albian amber of France are clearly distinct from that described in the ambers from Lebanon and Myanmar. The only contemporaneous squamates known in the Charentes by skeleton remains are Simoliophis, a marine snake, and Carentonosaurus, a marine varanoid lizard. The association of the skin fragments with arthropods typical of a litter fauna and araucarian pieces of wood [10] shows that these vertebrate remains were trapped on a soil of a coniferal forest close to a fluviatile or an estuarine area. Thus, the reptile sloughing from the French amber could possibly belong to Simoliophis or Carentosaurus if these marine reptiles lived close to the araucarian forest, or to a non-aquatic squamate still unknown by this time. The find of inclusions of marine origin in amber is surprising, but not impossible, as already shown by Perrichot et al. [18], who described some marine bugs of the family Gerridae in the same amber deposit.

The presence of a reptile skin in amber implies peculiar conditions of trapping. In case of a sloughing, two mechanisms can explain the fossilization of this skin in the French amber. Either remains of the sloughing were embedded in a resin that fell directly on ground, or a reptile having still fragments of sloughing attached on body would have rub on a resin flow along a trunk. The poor state of preservation of the skin rather agrees with the first hypothesis, confirming the observation of Perrichot [11] on the exceptionally high proportion of ‘litter amber’ for the Albian deposit of Archingeay–Les Nouillers. Moreover, other inclusions preserved together with the skin in the amber piece are common inhabitants of the ground litter of forests (Acari, Thysanoptera, and Strepsiptera).

Although amber is a selective trap mainly embedding small size organisms, particularly insects and other small arthropods, delicate remains of larger organisms can exceptionally be preserved. Skins found for few years in ambers are unique insight into the past diversity, and particularly into the Cretaceous, which is a key-period in the evolution of dinosaurs, birds, and squamate reptiles [12] and [14]. The present discovery is the first evidence of an Albian reptile skin in Europe.