One hundred and three specimens of turtles from the site of Atxoste have been identified. They correspond to fragments of disjointed plates or fragments of plates, both from the carapace and the plastron. All these elements can be attributed to a single taxon (Discussion). They comprise adult or subadult specimens (Fig. 4).

The turtle remains from Atxoste have been found exclusively in the Mesolithic levels V (GrA–13447 8670–8510 cal BP to GrA–13448 9100–8700 cal BP) and VI (GrA–15700 9570–9450 cal BP to GrA–15699 9940–9500 cal BP) (Fig. 3). At both diachronic levels, the plates were present in the vicinity of the walls of the rock shelter. The greater abundance of remains is recorded in the level V (Fig. 3).

Only one specimen corresponding to some specific anatomical elements has been recognized (e.g., nuchal, pygal). Other elements have not been identified (e.g., suprapygals). However, the discovery of several remains of the same element (e.g., five right epiplastra and five left xiphiplastra), together with the difference in size between some individuals, and their presence in more than one level, demonstrate the presence of several individuals (NMI = 5). Evidence of human predation has not been hitherto recognized in these fossils of turtles.

The characters used to refute the attribution of the taxon from Atxoste to M. leprosa, and to confirm that it belongs to E. orbicularis, are based on personal observation of osteological specimens in museum collections, especially of the collections of the Muséum national d’Histoire naturelle (Paris, France), as well as in the data provided by Bailón (2010), Gmira (1995), Hervet, 2000 and Hervet, 2004, and Pérez-García et al. (2011b).

CHELONII Latreille, 1800

CRYPTODIRA Cope, 1868

TESTUDINOIDEA Batsch, 1788

EMYDIDAE Rafinesque, 1815

Emys Duméril, 1805

Emys orbicularis (Linnaeus, 1758)

Fig. 4

Material: One hundred and three disarticulated elements of the carapace and plastron. They are part of the collection of the Bibat Arabako Arkeologia Museoa/Bibat Museo de Arqueología de Álava (Álava, Spain).

Locality and horizon: Mesolithic levels V and VI of the site of Atxoste (Virgala, Alava, Basque-Cantabrian Basin) (Fig. 2 and Fig. 3).

Description: The external bone surface of all the plates identified is smooth. The nuchal plate demonstrates that the carapace of this taxon lacks nuchal notch (Fig. 4l). It also lacks medial keel. This is also the case with the neurals and in the pygal (Fig. 4m–p). The first neural is rectangular, longer than wide (Fig. 4m). The other neurals are hexagonals, with the latero-anterior margins shorter than the latero-posterior ones (Fig. 4n–o). The pygal plate is trapezoidal and is wider at its anterior margin than at the posterior one (Fig. 4p). It is slightly wider than long. This plate has a shallow posterior notch. The distal margins of the peripherals situated in the bridge region are slightly dorsally directed, but those of the remaining peripherals and of the pygal are not (Fig. 4a–g, t–y).

A single cervical scute is present (Fig. 4l). Dorsally, it is almost twice as long as wide. Its visceral length is shorter than its dorsal length. The fifth vertebral scute overlaps all the anterior half of the pygal (Fig. 4p). It overlaps the antero-medial region of the tenth pair of peripheral plates (Fig. 4x). This taxon lacks overlap or contact between the marginal scutes and the costal plates (Fig. 4a–g, t–y). A well-developed anterior curvature of the lateral end of the sulci between the marginals is present. Furthermore, it lacks supracaudal scute but possess two separated posterior marginal scutes (Fig. 4p).

The anterior lobe of the plastron is interpreted as shorter than the posterior one, and both lobes are longer than the plastral bridge (Fig. 4z–ai). Both the anterior and the posterior lobes are subrounded. The epiplastral lips are low in the medial region, but they are more developed laterally (Fig. 4z–aa). All the identified entoplastra are subhexagonals (Fig. 4ab). Their greatest widths are situated in the anterior half. The sutures between the epiplastron and the hyoplastra are latero-anteriorly directed. A hinge is present between the hyoplastra and the hypoplastra (Fig. 4ac–af). Therefore, this taxon lacks a sutured contact between the hyoplastra and the peripheral plates. The plastral buttresses are low. The hypoplastra are wider than long. A wide but shallow anal notch is present (Fig. 4ag, ai).

The gulars overlap the anterior half of the entoplastron (Fig. 4z–ab). Medially, the humero-pectoral sulci are situated on the most posterior region of the entoplastron, very close to the sutures between the entoplastron and the hyoplastra. The humeral scutes are markedly distant from the axillary notches (Fig. 4ac–ad). The pectoro-abdominal sulci are located on the most posterior region of the hyoplastra, very close to the plastral hinge. No intergular or inframarginal scutes have been recognized. Medially, the anal scutes are long, being located near the contact between the hypoplastra and the xiphiplastra (Fig. 4ag–ai). Therefore, the anal scutes are medially longer than the femorals.

All the specimens of chelonians found in Atxoste can be attributed to a single taxon. Characters such as the absence of intergular and inframarginal scutes, the posterior reduction of the epiplastra, and the latero-anteriorly directed epi-hyoplastral sutures allow their attribution to Testudinoidea. This taxon differs from the representatives of Testudininei, the clade that includes terrestrial forms (e.g., Chersine hermanni), in characters, such as: smooth external bone surface; absence of medially short and laterally long costals, alternated with medially long and laterally short costals; relatively shallow sulci between the scutes; absence of overlap between the pleuro-marginal sulci and the costo-peripheral sutures; presence of lateral margins of the humero-pectoral sulci markedly distant from the axillary notches; medially poorly-developed epiplastral lip; hexagonal second to, at least, sixth neurals, with short latero-anterior margins but long latero-posterior ones. However, all these characters are shared with both the members of Emydidae (e.g., E. orbicularis) and Geoemydidae (e.g., M. leprosa) (see Chesi et al., 2009, Gmira, 1995 and Hervet, 2000).

The taxon of Atxoste can be attributed to E. orbicularis and differs from M. leprosa by: absence of a medial keel on the pygal plate; pygal not remarkably wider than long; presence of a small postero-medial notch (being generally absent in M. leprosa); fifth vertebral scute overlapping onto the anterior half of the pygal and the last pair of peripherals; short posterior marginal scutes; first to third pleural scutes wider than the vertebrals; the sulcus between the second and third pleurals in contact with the central region of the medial margin of the seventh marginal; the sulcus between the pleural and the marginal scutes always distant from the suture between the costal and the peripheral plates; markedly anteriorly directed lateral end of the sulci which delimit the marginals; anterior lobe of the plastron shorter than the posterior lobe, with the bridge shorter than both lobes; subrounded anterior margin of the epiplastra; relatively low epiplastral lips; subhexagonal entoplastron, with the greatest width situated in the anterior half; presence of a hinge between the hyoplastra and the hypoplastra; lateral edges of the hyoplastra not sutured to the peripherals; low and short plastral buttresses; wider than long hypoplastra; rounded lateral margins of the posterior plastral lobe; wide and very shallow anal notch; gular scutes reaching about the middle part of the entoplastron; humero-pectoral sulci located on the posterior edge of the entoplastron, being almost superimposed on the sutures between the entoplastron and the hyoplastra; pectoro-abdominal sulci located in the most posterior region of the hyoplastra; short abdominal scutes; absence of axillary and inguinal scutes; medially long anal scutes.

Considering all the discussed characters, all the material of turtles from Atxoste so far recognized is attributed to the emydid E. orbicularis. As indicated, the only reference in an archaeological site of the Basque-Cantabrian Basin to this taxon is that from Castro de Berbeia (Álava) (dated as deposited between the years 490 BC and 400 BC) (Altuna, 1978). Therefore, that reference comes from more recent levels than those present in Atxoste. The reference to the possible presence of E. orbicularis in Castro de Berbeia was exclusively based on a bone cited as a humerus, the only element that Altuna (1978) attributed to a turtle. That element was not described or figured, and was not referred using an inventory number. In fact, no anatomical characters were used for its determination. Altuna (1978) indicated that the length of the bone was 33 mm. He justified that attribution based solely on the current presence of this species in the area, indicating that, however, the specific determination could be considered questionable. All the material found in that locality is deposited in the Bibat Arabako Arkeologia Museoa/Bibat Museo de Arqueología de Álava (Álava, Spain). The entire collection of this site, including the indeterminate elements, has been reviewed by us. However, no turtle remains have been found. Therefore, both the reference to the species E. orbicularis in Castro de Berbeia, and the report of turtles in this locality are considered doubtful.

The site of Atxoste is located very close to the Berrón River. This river is a tributary of the Ega, a river that flows into the Ebro River. The presence of E. orbicularis has been previously cited in several Mesolithic sites of the Ebro Basin, from several ages (see Bosch et al., 2000, Félix, 2002 and Millán and Blanch, 1989). Therefore, these rivers, which connect the regions where the emydids from the Ebro Basin and Basque-Cantabrian Basin lived, may have facilitated the spread of this species.

The record of post-Mesozoic fossil turtles of the Basque-Cantabrian Basin is extremely limited. In addition to the identification of an indeterminate aquatic turtle in the Late Eocene of Zambrana (Álava), a single report to a Quaternary turtle had been published: a putative humerus of the European Pond Terrapin E. orbicularis. This identification was not justified. The attribution of material from that locality (from the Iron Age) to turtles cannot be confirmed. This lack of information contrasts with the relatively abundant, but so far little known, record of three clades of Testudinidae in Quaternary sites of other regions of the Iberian Peninsula: the terrestrial Testudininei, and the aquatic Geoemydidae and Emydidae.

The presence of turtles at the Mesolithic levels of the site of Atxoste (Álava), in the Basque-Cantabrian Basin, is referred here for the first time. More than one hundred elements of turtles have been found there. These consist of disarticulated plates and fragments of these elements. Systematic study of this material allows us to attribute it to the emydid E. orbicularis.

The identification of remains of turtles is common in contemporaneous sites in other regions of Spain (Bosch et al., 2000 and Félix, 2002). However, this group of reptiles had not been recognized in this region. Atxoste is the site with the northernmost remains of Quaternary turtles identified in the Iberian Peninsula. The turtles that lived there probably came from the Ebro Basin, because Atxoste is located in the Ebro drainage basin. The Cantabrian drainage basin is situated very close to Atxoste, approximately 20 km to the north. Most of the Pleistocene and Holocene sites of the North of the Iberian Peninsula are situated in Cantabrian drainage basin. The boundary between the two basins probably represented a barrier to the dispersal of these reptiles. This may explain the absence of turtles in all these sites. Due to the existence of this potential natural barrier, and taking into account the absence of their record, the identification of the aquatic turtles E. orbicularis and M. leprosa as autochthonous taxa in this region (see Blanco and González, 1992) cannot be confirmed.