Intraspecific Variation in the Cranial Feeding Mechanism of Turtles of the Genus Trionyx (Reptilia, Testudines, Trionychidae)

New sea turtle from the Miocene of Peru and the iterative evolution of feeding ecomorphologies since the Cretaceous

“…Because all other species of durophagous stem-cheloniids are known only from cranial material, we cannot realistically expect cladistic analyses to tease apart convergent lineages. The fact that a durophagous feeding ecology and correlated skull characters can evolve independently within closely related turtle lineages (Claude, 2004) and can even be plastic within a single species (Dalrymple, 1977;Lindeman, 2000) further emphasizes the pattern of homoplasy recovered by our analysis. Because of this homoplasy, the monophyly of poorly known durophagous stem cheloniids cannot be accepted at face value, and that is why we recommend against lumping them all into the genus Euclastes.…”

Ontogenetic changes in jaw-muscle architecture facilitate durophagy in the turtleSternotherus minor

“…However, when processing durable prey, durophagous taxa rarely rupture their largest prey with a single load; instead, they typically exhibit several discrete crushing efforts, in which the prey item is loaded and repositioned several times until it is successfully ruptured or abandoned. This behavior for mollusk crushing is exhibited by S. minor (Pfaller, 2009), as well as durophagous fishes (Wainwright, 1987;Hernández and Motta, 1997;Grubich, 2005), lizards (Gans et al, 1985) and turtles (Dalrymple, 1977). Consequently, S. minor may rupture relatively small snails with a single load similar to our mechanical-loading trials, while rupture of larger snails is likely achieved with repeated, subcritical loads.…”

“…Alternatively, positive allometry may provide an energetic advantage in which larger individuals can increase their net rate of energy intake when foraging (optimal foraging) (MacArthur and Pianka, 1966). Presumably, as snail volume will increase as the cube of snail length (Hill, 1950;Schmidt-Nielson, 1984), by consuming larger snails adult S. minor would need to ingest fewer snails to meet its minimum energy requirements (Dalrymple, 1977). Moreover, larger turtles with higher bite forces may require less handling time to consume snails of certain sizes (Herrel et al, 2001;Verwaijen et al, 2002;Van der Meij and Bout, 2006).…”

The Herpetofauna of Lake Woodruff National Wildlife Refuge, Florida

“…An invertebrate species of particular note occurring in refuge freshwater marshes and impoundments is the freshwater snail known as the Florida apple snail (Pomacea paludosa). The Florida apple snail is an important component in the food web of Florida's freshwater marshes, serving as the primary food source for the endangered snail kite (Snyder and Snyder 1969, Hurdle 1973, Bennetts et al, 1994, as well as a food source for limpkins (Snyder and Snyder 1969), white ibis (Kushlan 1974), boat-tailed grackles (Snyder and Snyder 1969), a variety of fish (Darby et al, 1997), alligators (Delany 1986), and turtles (Dalrymple 1977). At least one Service report indicates that one of the reasons for building impoundments on the refuge was to create habitat for the Florida apple snail (U.S. Department of the Interior 1974).…”