Solitudo
| Solitudo Temporal range:
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|---|---|
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| Material ofSolitudo robusta | |
Scientific classification
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Testudines |
| Suborder: | Cryptodira |
| Superfamily: | Testudinoidea |
| Family: | Testudinidae |
| Subfamily: | Testudininae |
| Genus: | †Solitudo Valentiet al.2022 |
| Type species | |
| †Solitudo robusta (Leith-Adams, 1877)[1]
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| Other species | |
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Solitudois an extinct genus oftortoisethat was found during thePlioceneandPleistoceneon theMediterraneanislands ofMenorca,MaltaandSicily.The genus includes three described species,Solitudo robusta,Solitudo gymnesicaandSolitudo siculaas well as a likely fourth, undescribed species fromMonte Pellegrinoin Sicily.Solitudo sicula,the youngest of the species, died out approximately 12.5 thousand yearsBP.The largest species,Solitudo gymnesica,has been estimated to have reached a carapace length of 1.1–1.3 m (3.6–4.3 ft).
History
[edit]The oldest discoveries of fossil turtles now included underSolitudowere made in the 19th century, with Leith-Adams describing remains fromZebbug Cave(Malta) asTestudo robusta.In 1914Testudo gymnesicawas described based on Pliocene material found onMenorca.[2]Younger material was later discovered in theZubbio di Cozzo San Pietrocave in northernSicily.These remains, which include afemur,phalanx,pubisand anischium,were found in what is thought to be a prehistoric funeral site, however repeated human or animal activity changed the stratigraphy of the site. Due to this the turtle remains, although suspected to have belonged to a single individual, were dispersed across the site. Additionally, these finds have been found to be unrelated to the human activity at the site, having been deposited there independently of the human remains. These remains were described in 2022 by Valenti and colleagues, who found sufficient anatomical evidence to establish a new genus they dubbedSolitudo,with"Testudo" robustaserving as the type species. The remains from Sicily were used to erect a new species,Solitudo siculaandSolitudo gymnesicabecame a new name for"Testudo" gymnesicafrom Menorca.[3]
The nameSolitudoderives from theLatinword for loneliness or solitude, which reflects the isolation of islands where members of this genus have been found. The name ending with "tudo" furthermore serves as an allusion to the genusTestudowith which the genus shares characteristics with. The species name of the youngest member,Solitudo sicula,is the female form of the Latin word for "Sicilian".[3]
Description
[edit]The different species ofSolitudodiffer from the tortoises of theTestudogenus mostly in the anatomy of thetrochanters.InTestudo,the trochanters are fused at the proximal end of the bone through the presence of a rounded ridge which is absent inSolitudo,leaving the trochanters only incompletely fused. The femur is generally slender and its head narrower than the width between the two trochanters. Additionally, the femoral head is oriented in a 25-45° angle when viewed from above, while other genera of tortoise have femoral heads with more anteroposterior orientation.[3]
Solitudo siculais distinguished by the other species of the genus by having trochanters that are at the same height as the femoral head, additionally, the femoral head is also more elliptical than in more derivedSolitudo species.The entire femur ofS. siculameasures 104 mm (4.1 in) long, which is notably larger than that of the biggest extant tortoise of Europe, theMarginated tortoise.Assuming similar proportions, this would mean thatSolitudo siculamay have reached a straight carapace length of 50–60 cm (20–24 in).[3]
Larger sizes have been estimated for the older species.Solitudo robustamay have reached a carapace length of up to 85 cm (33 in), while some estimates suggest thatSolitudo gymnesicacould have reached a carapace length of 1.1–1.3 m (3.6–4.3 ft).[4]
Phylogeny
[edit]Although repeated attempts at extracting genetic material were conducted, no methods yielded DNA which rendered molecular phylogenetic analysis impossible. Due to this restriction, the relationship betweenSolitudoand other circum-Mediterranean tortoises was established on the basis of femur morphology, which is well known in the relevant taxa. Morphological analysis concluded that among the tortoises found around the Mediterranean, three separate femur morphotypes could be found. The "Testudinini morphotype", which is generally slender with a more narrow and oblique head, the "‘Geochelonini morphotype" which was found to be more robust and with a less oblique head and the "Insular morphotype" which typically shows a non-oblique head, slender diaphysis and trochanters that unlike in the other groups are not fully joined at the proximal end of the bone. The clade that contains allSolitudospecies is based on a single synapomorphy, the incompletely fused trochanter, supported by the geographical proximity.[3]
TheSolitudo siculais recovered in a basal position within the genus, its femur still retaining some similarities to the "Testudinini morphotype". Besides the three named species ofSolitudo,a fourth, unnamed taxon fromMonte Pellegrinowas also found to fall within the "Insular morphotype", sharing the unfused trochanter that defines the clade. The idea that this specific morphotype is the result of the tortoise's insular habitat is dismissed on account of other insular species retaining their ancestral morphology, such as the Galápagos tortoise andGran Canaria giant tortoise.The exact relationship betweenSolitudoand the other tortoises surrounding the Mediterranean remains unknown until better material, in particular fossils of the head and shell, is found.[3]
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Paleobiology
[edit]Remains ofSolitudoare exclusively known from Mediterranean islands. The type species,Solitudo robusta,was found on the island of Malta and has been dated to the Middle Pleistocene.Solitudo gymnesicais known from Pliocene Menorca andSolitudo siculafrom Sicily. Dating the pubis ofSolitudo sicularevealed that the animal lived approximately 12.5 ± 0.5 thousand yearsBP.Solitudo siculawould have shared its home island with the extant Hermann's Tortoise, which has been continuously present on Sicily since at least the Middle Pleistocene. There are also remains of unnamed giant tortoises found on Sicily, they were however not contemporary withSolitudoand instead correlate with the Middle Pleistocene.[3]
References
[edit]- ^Leith-Adams, A. (1877)."On gigantic land-tortoises and a small freshwater species from the ossiferous caverns of Malta, together with a list of their fossil fauna; and a note on chelonian remains from the rock-cavities of Gibraltar".Quarterly Journal of the Geological Society.33(1–4): 177–191.doi:10.1144/GSL.JGS.1877.033.01-04.11.S2CID131329294.
- ^Cardona, J. Q.; Agusti, J. (2019). "First evidence of faunal succession in terrestrial vertebrates of the Plio-Pleistocene of the Balearic Islands, western Mediterranean".Comptes Rendus Palevol.18(3): 317–324.Bibcode:2019CRPal..18..317C.doi:10.1016/j.crpv.2019.02.001.S2CID150158569.
- ^abcdefgValenti, P.; Vlachos, E.; Kehlmaier, C.; Fritz, U.; Georgalis, G.L.; Hernández Luján, À.; Miccichè, R.; Sineo, L.; Delfino, M. (2022). "The last of the large-sized tortoises of the Mediterranean islands".Zoological Journal of the Linnean Society.196(4): 1704–1717.doi:10.1093/zoolinnean/zlac044.
- ^Rhodin, A.G.J.; Thomson, S.; Georgalis, G.L.; Karl, H.V.; Danilov, I.G.; Takahashi, A.; de la Fuente, M.S.; Bourque, J.; Delfino, M.; Bour, R.; Iverson, J.B.; Shaffer, B.H.; van Dijk, P.P. (2015)."Turtles and Tortoises of the World During the Rise and Global Spread of Humanity: First Checklist and Review of Extinct Pleistocene and Holocene Chelonians"(PDF).Chelonian Research Foundation; Chelonian Research Monographs.5(4): 1–66.doi:10.3854/crm.5.000e.fossil.checklist.v1.2015.Archived(PDF)from the original on 21 September 2022.
