Fish nibbles on Pteranodon metacarpal

Figure 1. Fish teeth compared to grazed Pteranodon metacarpal

Figure 1. Fish teeth compared to grazed Pteranodon metacarpal

Ehret and Harrell 2018
bring us news from Alabama of two distinct sets of tooth marks on a Pteranodon (Fig. 2) metacarpal (Fig. 1). They report:

“The Pteranodon specimen exhibits serrated teeth marks on the surface of the bone and a second set of larger, unserrated teeth marks unlike those of any contemporary shark species. These feeding traces compare favorably with the tooth spacing and morphology of Squalicorax kaupi, and a small to moderate-sized saurodontid fish, such as Saurodon or Saurocephalus, respectively. In both instances, feeding traces appear to be scavenging events due to the lack of any healing or bone remodeling. The specimen represents a pterosaur that either fell into marine waters or was washed out from nearshore areas and then scavenged by both a chondrichthyan and osteichthyan.”

“Many fossils from late Cretaceous Alabama appear to have been nibbled by sharks, including sea turtles and dinosaurs, which are often ‘covered in predation marks,’ says Ehret.”

NatGeo publicized the find by talking to some pterosaur experts, “Pterosaurs actually had a lot of meat on their skeletons,” says Michael Habib, a pterosaur expert at the University of Southern California who was not involved with the latest find. “They were not the skinny animals often depicted in films and art. The flight muscles in particular would have made a great meal.”

Pterosaur metacarpals,
like all metacarpals, actually are sinewy and have little to no associated muscle.

Habib adds,
“Pteranodon also inhabited this coastal environment during the late Cretaceous, making a living snatching smaller fish from the shark-filled waters. Pterosaurs could float, but being less buoyant than birds, they probably didn’t sit on the surface for long. Some species, including Pteranodon, did likely plunge into the water for prey. “They could then quickly take back off from the surface. But these diving pterosaurs might have been vulnerable to sharks just after they entered the water,” he says.

M. Witton concluded,
“It’s nice to know what species were interacting in this way.”

Ehret corrected the pterosaur experts,
“It’s also possible that the animal died near the shore and was scavenged when it washed out to sea.”

Figure 3. Triebold Pteranodon in floating configuration. Center of balance marked by cross-hairs.

Figure 2 Triebold Pteranodon in floating configuration. Center of balance marked by cross-hairs.

Contra Habib’s statement
Pteranodon was at least as buoyant as a pelican. It has been widely known for over a century that pterosaur bones are thinner than bird bones and Pteranodon metacarpals, in particular, were hollow like pontoons (Fig. 2).

Ultimately
the bite marks represent curiosity, not predation, a point understood by Ehret and Harrell.

References
Ehret DJ and Harrell TL Jr. 2018. Feeding traces of a Pteranodon (Reptilia: Pterosauria) bone from the late Cretaceous (Campanian) Mooreville Chalk in Alabama, USA. Palaios 33(9):414–418.

www.natgeo.com/

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