The key text on the chelonophagi of the Red Sea and the Indian Ocean is by Agatharchides of Cnidus, whose editor provides valuable commentary on the geography and literary tradition concerning this population of the southern seas ,as well as ethnographic evidence for the use of turtle meat across the Arabian seaboards: Agatharchides of Cnidus, On the Erythraean Sea, translated and edited by Stanley Burnstein (London: Hakluyt Society, 1989).
The complex narrative transformations of the figures of the ketos, aspidocheloni, fish-island, and turtle island are most recently detailed by Ioannis M. Konstantakos, “The Island That Was a Fish: An Ancient Folktale from the Alexander Romance and Other Texts of Late Antiquity,” in Aspects of Orality and Greek Literature in the Roman Empire, edited by Consuelo Ruiz-Montero, pp. 281–301 (Newcastle: Cambridge Scholars Publishing, 2019). William F. Hansen also provides a very useful summary of folktales from different ancient and more recent cultures that include the motif of the giant sea-creature,“fish” or turtle; see his Ariadne’s Thread: A Guide to International Tales Found in Classical Literature (Ithaca, NY: Cornell University Press, 2002), especially pp. 180-181. For more on the didactic symbolism of the aspidochelone in the Physiologus, see Fausto Ianello, “Il motivo dell’aspidochelone nella tradizione letteraria del Physiologus: Considerazioni esegetiche e storico-religiose,” Nova Tellus 29 (2011), 151–200.
Of the medieval Arabic texts that describe the sea turtle, the comprehensive descriptions I relied the most come from works that contain rich information on aquatic creatures in general. One is the 11th-century anonymously authored Egyptian text entitled Kitāb ghara’ib al-funūn wa-mulaḥ al-‘uyūn (Book of Curiosities of the Sciences and Marvels for the Eyes) usually referred to as “The Book of Curiosities” and expertly presented in the original Arabic and in English translation with copious scholarly commentary by Yossef Rapoport and Emilie Savage-Smith, An Eleventh-Century Egyptian Guide to the Universe: The Book of Curiosities (Leiden: Brill 2014). The other is the 13th-century Syrian cosmographer Shamsaddin Abu Abdallah Muhammad b. Ibrahim b. Abi Talib al-Ansari al-Dimashqi’s Nukhbat al-dahr fi ‘aja’ib al-barr wa’l-bahr (the Choice of the Age on the Curiosities of Land and Sea), edited by M.A.F. Mehren (St Petersburg, 1866). A perfect mix of the myth and reality of sea turtles appears in the turtle-island tale included in Buzurg b. Shahriyar, The Book of Wonders of India, edited by G.S.P. Freeman-Grenville (London and the Hague: East-West Publications, 1982).
Jack M. Davis, The Gulf: The Making of an American Sea, a wonderful biography of what is officially called the Gulf of Mexico provides a rich synthesis of early and subsequent turtle hunting and the consumption and trade in turtle meat on the Gulf shores.
In her blog Looking Through Art, Rijksmuseum art historian Erma Hermens offers a series of wonderfully informative and richly illustrated posts about green turtles and their uses in European art and culture, including their importance in Renaissance and later medicine: https://lookingthroughartblog.wordpress.com/2020/08/05/healing-turtles-a-short-history
On the properties and plasticity of tortoiseshell, I consulted the insightful and very accessible account provided by Thomas Hainschwang and Lawrence Leggio, The Characterization of Tortoiseshell and Its Imitations, Gems and Gemology 42 (2006): 36–52.
There is a plethora of scientific information about the biology of sea turtles, the threats they face today, and conservation efforts and success stories. I relied heavily on NOAA (National Oceanic and Atmospheric Administration) Fisheries resources: https://www.fisheries.noaa.gov/search?oq=sea+turtles The many organizations devoted to the protection of sea turtles include, in Greece, ARCHELON – Τhe Sea Turtle Protection Society of Greece https://archelon.gr/enFor a fascinating article on tortoiseshell as a “deadly” commodity: https://wwf.org.au/blogs/in-photos-the-deadly-price-of-tortoiseshell/