Mesozoic Shark Nurseries - Evidence from the Triassic of Kyrgyzstan

Very cool paper, especially since the Chinle Formation in Petrified Forest National Park also contains shark egg capsules (Palaeoxyris). The Petrified Forest specimens are the only ones known from North America.

Fischer, J., Voigt, S., Schneider, J. W., Buchwitz, M., and  & S. Voigt. 2011. A selachian

freshwater fauna from the Triassic of Kyrgyzstan and its implication for Mesozoic shark nurseries. Journal of Vertebrate Paleontology 31:937-953.

Abstract - Habitat partitioning and site fidelity of spawning grounds are well-documented phenomena in extant selachians, but little is known about the reproductive strategies of their fossil relatives. Here we describe the selachian fauna of the Middle to Late Triassic Madygen Formation in southwestern Kyrgyzstan, Central Asia, based on several dozen tooth crowns and egg capsules. The material is assigned to three new taxa: Lonchidion ferganensis, sp. nov., and Palaeoxyris alterna, sp. nov., being teeth and egg capsules of hybodontid sharks, and Fayolia sharovi, sp. nov., being egg capsules of probable xenacanthids. Teeth of L. ferganensis, sp. nov., were almost exclusively found in pelecypod-rich shallow lacustrine mudstones and belong to juvenile individuals. Oxygen and strontium isotope data of tooth enameloid indicate freshwater conditions of the ambient water at the time of tooth mineralization. The egg capsules are common findings in near-shore lake deposits as well. Considering the mass co-occurrence of juvenile teeth and egg capsules in the study area, we propose that hybodontid/ xenacanthid sharks recurrently occupied littoral zones of the Madygen lake for spawning. The small number of full-grown individuals points to habitat partitioning of juveniles and adults wherefore the study site is interpreted as a shark nursery. The oviposition strategies inferred from this fossil example are remarkably similar to those of modern sharks, suggesting that the reproductive patterns seen in extant sharks originated well before the Cenozoic.

http://dx.doi.org/10.1080/02724634.2011.601729

Looking at Aetosaurs in a Whole New Way

Jeff Martz's recent post at Paleo Errata reminded me of this recent article which came out two months ago. Check it out, you can tell that the writer had a lot of fun with this, and the photo (see courtesy photo from http://www.santafenewmexican.com/ below) is great.

Of course, one comment made in the article regarding the similarity to modern crocodiles led to a Google search which turned up what could best be described as um....., you got it, croc porn.

All of this aside, what a great specimen of Typothorax!