Plastral deossification in the Endangered Spiny Hill Turtle, Heosemys spinosa (Testudines: Geoemydidae) on Borneo

Siti Nor Baizurah, Abd Malik and Indraneil, Das (2023) Plastral deossification in the Endangered Spiny Hill Turtle, Heosemys spinosa (Testudines: Geoemydidae) on Borneo. Journal of Threatened Taxa, 15 (6). pp. 23307-23314. ISSN 0974-7907

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Abstract

Studies of the evolution of turtle shell morphology have raised numerous questions. In this study, five adult females and two adult males of the Endangered Spiny Hill Turtle Heosemys spinosa from two localities in western Sarawak in East Malaysia (Borneo) were examined for the presence of plastral deossification zones, reported as indicative of kinesis in earlier studies. A total of 52 (34 females, 18 males) radiographs demonstrated distinct poorly-ossified areas across the hyo-hypoplastral and the hypo-xiphiplastral junctures in females of straight carapace length (SCL) 143.4–211.4 mm. The feature is here interpreted as a permanent plastral hinge, which was not observed in either of the males examined. The smallest female with a weak but discernible line at the contact of these bones had a SCL of 125 mm, suggestive of minimum size of maturity in Heosemys spinosa in this population.

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