Solitudo sicula, Valenti & Vlachos & Kehlmaier & Fritz & Georgalis & Luján & Miccichè & Sineo & Delfino, 2022

Valenti, Pietro, Vlachos, Evangelos, Kehlmaier, Christian, Fritz, Uwe, Georgalis, Georgios L., Luján, Àngel Hernández, Miccichè, Roberto, Sineo, Luca & Delfino, Massimo, 2022, The last of the large-sized tortoises of the Mediterranean islands, Zoological Journal of the Linnean Society 196 (4), pp. 1704-1717 : 1711-1714

SOLITUDO SICULA SP. NOV.

FIGS 4–5

Zoobank registration: urn: lsid: zoobank. org:act: F5011B57-E559-4F72-9131-D457D8B6B998.

Holotype: ZCSP US.0-Q2, an almost complete right femur, missing only part of the major trochanter ( Fig. 4 ) . Paratypes: ZCSP US.0-Q1, a fragment of a right ischium ( Fig. 5A, B ) ; ZCSP US.2-Q4, a left pubis ( Fig. 5C, D ); ZCSP US.0-Q3, an ungual phalanx ( Fig. 5 E-G). Due to the uncertainty of the attribution of the four skeletal remains to a single individual (see below), we do not group the ischium, the pubis and the phalanx along with the femur as a single holotype, but we keep them separated .

Type locality and age: Zubbio di Cozzo San Pietro Cave , Municipality of Bagheria , near Palermo , northwestern Sicily, Italy. Latest Late Pleistocene. For details about the locality, see Locality information above. The tortoise remains here described come from an archaeological funerary area ( Battaglia et al., 2020) placed at a depth of − 15.4 m from the entrance and characterized by disturbance caused by human and/or animal activity that determined a complex stratigraphy. The remains of the pubis, ZCSP US.2-Q4, was AMS-dated revealing an age of 12.5 ± 0.5 kya BP (Supporting Information, Fig. S3 ). All the tortoise material is referred to the latest Late Pleistocene assuming that it belongs to the same, extremely rare taxon (large-sized tortoises have never been reported in the several Sicilian Late Pleistocene-Holocene archaeological and paleontological sites so far studied), even if not necessarily to a single specimen (considering the alteration of the stratigraphy, a non-demonstrable but likely option because of non-anatomical overlap of the preserved skeletal elements, as well as their congruent size and common testudinid morphology) .

Etymology: Latin adjective in feminine gender, meaning ‘Sicilian’.

Diagnosis: Member of Solitudo based on the generic characters mentioned above. Differing from other species of Solitudo in having trochanters that are at the same height with the femoral head, and a femoral head that is clearly elliptical, whereas in other species trochanters extend beyond the femoral head and the latter is not elliptical.

Description

Femur: ZCSP US.0-Q2 ( Fig. 4 ; Supporting Information, Fig. S4 ) is a well-preserved right femur with a total length of 104 mm. The diaphysis is relatively slender and almost rectilinear, with a slight curvature on the distal part [more rectilinear than femora of Te. hermanni (adult and young individuals) and Te. marginata ]. The dimensions of the narrowest point of the diaphysis are 13.1 × 12.9 mm. It is not possible to measure the original width of the femur at the level of the trochanters, as the trochanter major is laterally incomplete. The width of its preserved portion is 32 mm. The maximum width of the distal epiphysis is 37 mm. The neck is well defined, relatively long and contracted with respect to the maximum width of the head (not as in the Menorcan species which has a femoral head detached even more clearly from the neck). The minimum width of the neck is 22 mm; its minimum thickness is 16 mm. The intertrochanteric fossa is wide and occupies the entire surface between the trochanters; it is approximately 10 mm deep. The trochanters do not extend more proximally compared to the femoral head (see Supporting Information, Appendix S1 for comments on the orientation of the femur). The lateral surface of the head neck is nearly vertical, the head does not overhang the shaft as in Te. hermanni and Te. marginata . The two trochanters are joined ventrally (so that the intertrochanteric fossa does not open ventrally), but the muscular insertion surfaces are clearly separated, and in medial view, the space between these two surfaces becomes thinner until it forms a relatively thin crest. In ventral view, this crest is not rectilinear but forms a wide ‘U’ (above which much of the head of the femur is visible). These areas of muscular insertion are clear, as they are defined by a thin ridge. A similar ridge delimits the ventral margin of the muscular insertion surface of the head—the one that overlooks the intertrochanteric fossa; another similar crest delimits the insertion region of the distal condyles. The area of muscular insertion of the small trochanter is clearly triangular, and probably also that of the great trochanter, although the latter is partially incomplete. On the anterior surface of the diaphysis of the femur, at the small trochanter, there is a long ridge of muscular insertion of the femorotibialis (more than half of the diaphysis) evident but moderately developed (although not as much as in Te. marginata ); it remains close to the edge between the anterior and ventral surface. On the posterior surface of the diaphysis, in connection with the great trochanter, there is an elongated area (depression with an irregular base) of muscular insertion of the adductor femoris, which expands distally by curving in a dorsal direction until it reaches the dorsal edge of the posterior surface at about the half of the diaphysis. The femoral head is narrow, narrower than the combined width of the trochanters (even more if we account for the missing part) and oval, clearly elliptical in outline, being oriented at an angle of approximately 30° compared to the anteroposterior plane. Distally, the tibial and fibular condyles are connected by a ridge ventrally, which is gently curved but only weakly developed.

Ischium: ZCSP US.0-Q1 ( Fig. 5A, B ; Supporting Information, Fig. S5 ) is an incomplete right ischium, missing the anteromedial area that contacts with the contralateral element and with the pubis. The anterior margin is laminar (it forms a sharp crest). On its ventral surface, at this anterior laminar margin there is a moderate depression medially bounded by an evident termination. The posterior margin is rounded and in dorsal view it forms a wide concavity. The dorsal surface near the medial margin is slightly concave. Posteromedially, the lateral ischial process forms a sort of low and broad tubercle with a rough surface (note that in Te. hermanni and Te. marginata , the morphology is completely different, taking the shape of a pointed process). Near the posteromedial margin, the ischium thickens ventrally as it is also indicated by the shape of the suture area with the left ischium. The posterior surface of this thickened area is characterized by an area of muscular insertion delimited by a small ridge similar to that of the trochanters of the femur.

Pubis: ZCSP US.2-Q4 ( Fig. 5C, D ) was an incomplete right pubis, preserving only its posterolateral portion. The three articular facets and the laminar region leading to the two other processes are preserved. This element has been destructively sampled for AMSdating and no longer exists.

U n g u a l p h a l a n x: Z C S P U S.0- Q 3 (F i g. 5E - G; Supporting Information, Fig. S6) is an ungual phalanx, with a length of 29 mm. The articular facet is divided into two concavities separated by a vertical convexity. The upper portion of the proximal epiphysis is clearly projecting. On its ventral surface, near the facet joint, there are two prominent foramina. The gross morphology of the phalanx is clearly different from that of Testudo spp. ; it is wide and flat instead of being rounded in section.

Size: The femur is much larger than that of Te. marginata , which is the largest extant tortoise species in Europe ( Ernst & Barbour, 1989; Bringsøe et al., 2001). For example, the Te. marginata femur MDHC 370 has a length of 51 mm, while the straight carapace length of the same specimen is 300 mm. On the basis of the length difference of the femora (ZCSP US.0-Q2 is 104 mm long), we estimate the straight carapace length of the extinct Sicilian tortoise as exceeding 50 cm and maybe up to 60 cm, i.e. significantly larger than that of extant Te. hermanni [up to 37.5 cm in the Balkans and up to 22 cm in the western Mediterranean ( Cheylan, 2001)], or any other Testudo species. The size record for Te. marginata , the largest species of the genus, is 40 cm, but most specimens are significantly smaller ( Bringsøe et al., 2001).

Figures

Figure 3. Consensus tree of the seven most parsimonious trees of 5469 steps, resulting from the cladistic analysis of extant and extinct tortoises (22 taxa scored for 177 morphological characters). The femora of the circum-Mediterranean tortoises represent three morphotypes that are independent from body size. They belong mostly to two different morphotypes (I, II) that show a phylogenetic signal within Testudininae, i.e. Testudinini vs. Geochelonini, whereas insular tortoises from the Mediterranean show a different morphotype (III). The simplified drawings are not to scale. Abbreviations: major tr.: major trochanter; minor tr.: minor trochanter.

Figure 4. Solitudo sicula sp. nov. from the latest Pleistocene of Zubbio di Cozzo San Pietro Cave, Sicily, Italy. Holotype ZCSP US.0-Q2, right femur, in dorsal (A), anterior (B), ventral (C), posterior (D), proximal (E) and distal (F) view. The right femur of the extant Te. marginata (the largest Mediterranean extant tortoise) is included for comparison at the same scale. Scale bar = 10 cm.

Figure 5. Solitudo sicula sp. nov. from the latest Pleistocene of Zubbio di Cozzo San Pietro Cave, Sicily, Italy. Right ischium ZCSP US.0-Q1 in dorsomedial (A) and ventrolateral (B) views. Left pubis ZCSP US.2-Q4 in ventromedial (C) and dorsolateral (D) views. Ungual phalanx ZCSP US.0-Q3 in dorsal (E), ventral (F) and lateral (G) views. Scale bar = 10 cm.