Eodortoka cf. morellana Perez-García, Gasulla and Ortega, 2014

Jacobs, Megan L., Pérez-García, Adán, Martín-Jiménez, Marcos, Mottram, Catherine M., Martill, David M., Gale, Andrew S., Mattsson, Oliver L. & Wood, Charles, 2023, A well preserved pan-pleurodiran (Dortokidae) turtle from the English Lower Cretaceous and the first radiometric date for the Wessex Formation (Hauterivian-Barremian) of the Isle of Wight, United Kingdom, Cretaceous Research 150 (9), pp. 428-429 : 8-12

publication ID	https://doi.org/ 10.1016/j.cretres.2023.105590
DOI	https://doi.org/10.5281/zenodo.8250336
persistent identifier	https://treatment.plazi.org/id/566E87D4-966A-FFA4-287B-FE020A6FF6AA
treatment provided by	Felipe
scientific name	Eodortoka cf. morellana Perez-García, Gasulla and Ortega, 2014
status

Treatment

( Figs. 3 - 9 View Fig View Fig View Fig View Fig View Fig View Fig View Fig )

Material. IWCMS 2018.44 is a partial skeleton of a probably juvenile individual ( Fig. 3 View Fig ), comprising a relatively complete shell (maximum preserved length 49.6 mm and maximum preserved width 47.6 mm; Figs 3 View Fig , 4 View Fig ), whose external surface has been partially eroded, obscuring most boundaries of the scutes; as well as several vertebrae (most cervicals, Fig. 5 View Fig ; some dorsals, Fig. 6 View Fig ; and scarce caudals, Fig. 7 View Fig ), partial pectoral and pelvic girdles ( Figs. 4 View Fig , 8 View Fig ), and several appendicular bones including both humeri, right femur, fibula and tibia ( Fig. 9 View Fig ). Locality. Brook Bay , Isle of Wight, United Kingdom, National Grid Reference SZ 385 836.

Horizon. Wessex Formation, Early Cretaceous, Barremian.

4.2. Description

4.2.1. Shell

Carapace. The shell of IWCMS.2018.44 has a high degree of erosion, the nuchal plate, most elements of the neural series, most peripherals and the pygal plate are missing, as are some costal plates of the right side in the central third of the carapace ( Figs. 3 View Fig , 4 View Fig ). It is relatively low, and oval. The maximum width is at the level of the mesoplastron. Seven of the left costal plates are identified (all of them except the posterior one). Only the left bridge peripherals (4 - 7) are preserved. No fontanelles are recognized.

Plastron. The plastron is slightly crushed, seemingly having been depressed into the body cavity. The left side of the plastron is better preserved than the right ( Figs. 3 View Fig , 4 View Fig ). No remains of the epiplastra or entoplastron are preserved. The hyoplastron is almost fully preserved, except for its anterior margin. The specimen displays a laterally located pair of mesoplastra, being slightly wider than long. The anterior end of the xiphiplastron is present. At its thickest point, the plastron is 2.3 mm thick.

4.2.2. Vertebral column

Cervical vertebrae. There are seven cervical vertebrae preserved inside the shell of IWCMS 2018.44. 6 with a fused neural arch and centrum and one isolated neural arch of the axis ( Fig.5 View Fig A-AP).These are not in articulation within the carapace. The centra are ventrally keeled with the keel becoming less prominent through the series, and almost non-existent in cervical 8 ( Fig. 5 View Fig ). Centra 3 - 5 are opisthocoelus, centra 6 - 7 are amphicoelous and centra 8 is procoelus ( Fig. 5 View Fig ). The anterior end of the centra have an oval cross section, becoming more triangular through the series. Posterior end of the centum have a square cross section to triangular through the series. All vertebrae have a large circular neural canal, increasing in diameter through the vertebral series. From vertebrae 5 - 8, the neural canal is larger in diameter than the diameter of the centrum ( Fig. 5 View Fig ). The diapophyses are anteriorly placed in vertebrae 2 - 4 and become more posteriorly placed through 5 to 8. Vertebrae 8 has a small, rounded neural spine.

Thoracic vertebrae. Five thoracic vertebrae are preserved, two with a fused neural arch (a neural plate being also preserved as a fused element to one of them), two isolated centra, and an isolated neural arch ( Fig. 6 View Fig A-AD). The centra are shallow and are laterally pinched. This is more evident mid series, with the centra becoming wider posteriorly. They possess a large neural canal, at least twice the depth of the centrum. The neural spines are tall and elongate, extending over the posterior and anterior portion of the centrum anteriorly in the series, and only posteriorly towards the posterior portion of the series.

Sacral vertebrae. A portion of sacrum is preserved, with two right lateral processes ( Fig. 7 View Fig A-D). A small portion of centrum is preserved posteriorly. The neural arch is wide, with a T -shaped cross section.

Caudal vertebrae. Three caudal vertebrae are preserved, with fused neural arches ( Fig. 7 View Fig E-P). The most anterior caudal has a complete centrum and neural arch preserved. It lacks a neural spine but possesses large pre- and postzygopophyses. The centrum is oval in cross section. Posterior caudals have a short centrum.

4.2.3. Appendicular skeleton

Shoulder girdle. Both scapulae are preserved ( Fig. 8 View Fig A-L). The right one is complete. The acromion process is slightly oval in cross section. Both coracoids are preserved ( Fig. 8 View Fig M-X). The left coracoid is complete, the right coracoid is only presented by the proximal end. The coracoid is dorsoventrally thin and considerably expanded distally.

Pelvic girdle. The pelvic girdle is almost complete, preserved in their natural anatomical position ( Fig. 9 View Fig ). The sutures between the ilium, ischium and pubis are visible, and the pubic scar is visible on the xiphiplastron. The ilium is fused to the carapace, and the ischium and pubis are fused to the plastron. The ilium is robust and mediolaterally narrow. The ischium is rod-like, with a distally expanded head where it contacts the ilium. The pubis has a large obturator foramen.

Forelimbs. Only the complete right humerus and part of the left are preserved ( Fig. 10 View Fig A-R). The diaphysis has a mediolateral curve, with an oval articular head. The distal end is wide, with a deep intertubercular fossa between a large medial process and a large lateral process.

Hindlimbs. The partial right femur, tibia and fibula are preserved. The right femur has its proximal end missing ( Fig. 10 View Fig M-R). The diaphysis is laterally curved and is distally expanded forming a large tibial condyle. Only distal portion of the right tibia is preserved ( Fig. 10 View Fig Y-AD). The shaft has an oval cross section. The distal end is expanded with a broad articular surface. Only the proximal end of the right fibula is preserved ( Fig. 10 View Fig S-X). It has a proximally expanded head with an oval cross section. The medial surface is straight, and the lateral surface is convex.