Comparative osteology and osteometry of the coracoideum, humerus, and femur of the green turtle (Chelonia mydas) and the loggerhead turtle (Caretta caretta)

Abstract

Fragmented skeletal remains of marine turtles occur frequently in archaeological and natural deposits on tropical and subtropical coasts. Identifying these remains to species based on their differential osteomorphology is vital to address questions pertaining to the historical ecology, archaeology, and conservation of marine turtles globally. Although the species‐specific features of extant marine turtle skulls and carapax are relatively well known, the comparative osteomorphology and osteometry of postcranial endoskeletons in closely related species of marine turtles remains unstudied. In this paper, we provide verbal descriptions, line drawings, and photographs of diagnostic morphological criteria for the coracoideum, the humerus, and the femur of two closely related species of Cheloniidae: Chelonia mydas (green turtle) and Caretta caretta (loggerhead), based on observations on modern skeletons. We also present osteometric indices of the humerus and the femur that can be used to distinguish between both species. We comment on the applicability of these criteria on archaeological marine turtle assemblages from the Mediterranean.

Threatened North African seagrass meadows have supported green turtle populations for millennia

“…Osteological and osteometrical species identification of C. mydas and C. caretta is possible from the humerus, femur, and coracoideum ( 18 ) but infeasible for fragmented material. However, species can be identified using collagen peptide biomarkers, which are applicable to highly fragmented material ( 19 ).…”

Preserved collagen reveals species identity in archaeological marine turtle bones from Caribbean and Florida sites

“…At present, the morphological identification of bones is the most common method of specimen identification in zooarchaeology. Recent advancements in comparative marine turtle skeletal morphology have improved our ability to identify marine turtle carapace, plastron, cranial and limb elements recovered from archaeological assemblages [26]. However, in many archaeological contexts of deposition, adult and juvenile marine turtle remains are broken, highly fragmented, eroded and disassociated from the original location of capture or butchery.…”

Tracking turtles in the past: zooarchaeological evidence for human-turtle interactions in the ancient Eastern Mediterranean

“…At Early Bronze Age Fadous, turtle remains constitute approximately 3.5 per cent NISP and 10 per cent MNI. Morphological analysis suggests that these probably represent exclusively loggerheads (Koolstra et al 2019). A complete loggerhead carapace (0.60-0.65m SCL) was recovered from a rubble fill, with no associated evidence suggesting that it was a ritual context.…”

“…In Trionyx, the distinctively sculpted carapace is readily identifiable (Figure 3), and other elements also differ from fully marine turtles (Williston 1925). To distinguish Chelonia and Caretta bones, which are almost identical in shape and size, we used differences in the skull and the lower jaw (dentary) (Wyneken 2001), along with recently published criteria (Koolstra et al 2019), to identify fragmentary limb bones.…”