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Leninia, new ichthyosaur from Cretaceous of Russia + Swedish marine reptiles



From: Ben Creisler
bcreisler@gmail.com

Two new online papers about marine reptiles:

Valentin Fischer, Maxim S. Arkhangelsky, Gleb N. Uspensky, Ilya M.
Stenshin and Pascal Godefroit (2013)
A new Lower Cretaceous ichthyosaur from Russia reveals skull shape
conservatism within Ophthalmosaurinae.
Geological Magazine (advance online publication)
DOI: http://dx.doi.org/10.1017/S0016756812000994
http://128.232.233.5/action/displayAbstract?fromPage=online&aid=8851882&fulltextType=RA&fileId=S0016756812000994

Ophthalmosaurinae is a recently recognized clade of derived
ichthyosaurs (marine reptiles) ranging from the Bajocian (Middle
Jurassic) to the late Albian (late Early Cretaceous). Whereas the
Middle–Late Jurassic ophthalmosaurine Ophthalmosaurus is often
regarded as a hyperspecialized deep diver, very little is known about
the anatomy, evolutionary history and ecology of Cretaceous
ophthalmosaurines because of the scarcity of the fossils and the lack
of well-preserved skull material. Here, we describe the skull of a new
basal ophthalmosaurine ichthyosaur, Leninia stellans gen. et sp. nov.,
from the lower Aptian of western Russia, and compare the ocular
characteristics of ophthalmosaurids. Leninia is recovered as a basal
ophthalmosaurine; it possesses unique traits such as a star-shaped
frontal–parietal suture as well as features previously thought to be
unique to Ophthalmosaurus such as a supratemporal–stapes contact. A
large sclerotic aperture – significantly larger than in
platypterygiine ophthalmosaurids and similar to that of the
largest-eyed modern animals (giant and colossal squids) – and reduced
dentition appear widespread within ophthalmosaurines. This
conservatism suggests ophthalmosaurine ophthalmosaurids occupied
similar ecological niche(s) throughout their long evolutionary
history.


===


Anne Mehlin Sørensen, Finn Surlyk &  Johan Lindgren (2013)
Food resources and habitat selection of a diverse vertebrate fauna
from the upper lower Campanian of the Kristianstad Basin, southern
Sweden.
Cretaceous Research (advance online publication)
DOI: http://dx.doi.org/10.1016/j.cretres.2013.02.002
http://www.sciencedirect.com/science/article/pii/S0195667113000293



During the latest early Campanian, a diverse vertebrate assemblage
inhabited the shallow coastal waters of the Kristianstad Basin,
southernmost Sweden. The taxon-rich fauna includes numerous species of
sharks, rays, chimaeroids, bony fish, mosasaurs, plesiosaurs, aquatic
birds, crocodiles, and turtles. Vertebrate fossils have been found at
several localities within the basin, representing at least three
different environments: near-shore waters around a rocky island,
presumably murky, shallow waters adjacent to a river mouth, and more
open coastal waters. Many vertebrates in the marine faunal community
were high-level predators, others were piscivorous, bottom-dwellers
that fed primarily on benthic invertebrates and fish, or omnivores
that fed on algae and invertebrates. The fauna thus exploited a wide
range of food sources and habitats. Six trophic levels, ranging from
primary producers to fifth-level consumers, are recognised, indicating
a high loss of energy and reflecting a mixture of shallow coastal and
more open water ecosystems. The trophic structure suggests that the
basin was a rich palaeoenvironment with high faunal diversity and
productivity.


NOTE: The preview has a nice reconstructed scene of marine reptiles
and other critters.