SVP abstracts 27: Plesiosaur breathing

Wintrich and Vanoefer 2020
bring us a look at plesiosaur breathing, but do not consider the vertical feeding configuration (Fig. 1) and bubble-net blowing hypothesis.

Figure 3. Click to enlarge. Albertonectes reconstructed. This 11 m elasmosaur is the longest thusfar recorded. This may be the breathing pose, swallowing air, then submerging the neck. When horizontal the air could be passed back to the lungs, as hypothesized for Dinocephalosaurus.

Figure 3. Click to enlarge. Albertonectes reconstructed. This 11 m elasmosaur is the longest thusfar recorded. This may be the breathing pose, swallowing air, then submerging the neck. When horizontal the air could be passed back to the lungs, as hypothesized for Dinocephalosaurus.

From the Wintrich and Vanoefer 2020 abstract:
“Plesiosaurs are enigmatic marine reptiles known from the Late Triassic to the Late Cretaceous and represent the most derived group of sauropterygians.

Why ‘enigmatic’? Plesiosaurs are readily identified without argument.

“Among plesiosaurs, there are several lineages showing an extremely long neck, which raises different biomechanical questions dealing with use and function, up to the breathing mechanism. Furthermore, for aquatic tetrapods, buoyancy control is an important adaptation to support the body in the water column. The respiratory system and its influence on buoyancy control have been discussed only briefly, and no mathematical approach has been taken so far. However, the breathing mechanism and therefore the respiratory system of highly aquatic tetrapods has to be specialized in different ways to enable life in a pelagic environment.”

“Here, we follow different mathematical approaches based on the metabolism (work of breathing), the trachea, and the morphology of the skull and trunk, in order to reconstruct the breathing mechanism, respiratory system, and lung volume in plesiosaurs, and then discuss the most plausible respiratory anatomy.”

“Furthermore, we find support for the hypothesis of a functional secondary palate from the reconstructed respiratory system as well as for the use of gastroliths, especially in the Elasmosauridae.”

“In addition to this, we calculated the center of mass to reconstruct buoyancy control in plesiosaurs.”

“In general, we studied four different long-necked plesiosaurs (Cryptoclidus, Albertonectes, Rhaeticosaurus, Rhomaleosaurus) and included Augustasaurus as the most derived pistosaur for which the entire neck is known.”

“Our results demonstrate that the lung volume was larger than suspected for an aquatic tetrapod. However, plesiosaurs showed an adaption similar to that of marine turtles, which have shifted the lung to the dorsal side of the trunk. The influence of the long trachea on breathing is not as great as suggested before. However, especially in the elasmosaurid, the long neck influences the center of mass. This supports the hypothesis of gastroliths functioning in buoyancy control in elasmosaurs. Furthermore, based on an ancestral state reconstruction, we show that the specialized plesiosaurian respiratory systems probably evolved in early sauropterygians.”

‘Influences’. ‘Supports’. ‘Probably’. Conclusions?
I didn’t see any here. Did I miss something? Seems like this is all old news. Earlier we looked at the possibility that plesiosaurs were vertical hunters (Fig. 1), expressing bubble nets as they rose beneath fish schools, as in modern mysticetes. Let’s see that ‘specialized’ hypothesis tested in the 2021 abstracts.


References
Wintrich T and Vanhoefer J 2020. A specialized respiratory system in plesiosaurs (Sauropterygia): breathing with the long neck. SVP abstracts.

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