Leninia stellans
| Leninia stellans | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Temporal occurrence | ||||||||||||
| Lower Albium ( Lower Cretaceous ) | ||||||||||||
| 112.9 to 110.2 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Leninia stellans | ||||||||||||
| Fischer et al. 2013 | ||||||||||||
Leninia stellans is a type of ichthyosaur from the family of the Ophthalmosaurinae . So far, only one incomplete skull is known from the Lower Cretaceous (Lower Albium ) of the Russian Ulyanovsk Oblast .
Features and way of life
Like other ichthyosaurs, Leninia was probably characterized by a dolphin-like body, a long snout and proportionally large eyes. The rear section of the skull has been handed down; most of the snout is missing. The fossil has been preserved in three dimensions, the skull bones are still in their anatomical composite. Teeth have not survived in the preserved snout section; Leninia was presumably either toothless or had severely reduced teeth. A complete and unpressed scleral ring is preserved in the left eye socket . This bony reinforcement of the eye consists of 14 interlocking trapezoidal bones arranged in a ring. The scleral ring has a diameter of approx. 18 centimeters - so it is in the order of magnitude of the ophthalmosaurus and today's giant squids , the animals with the largest known eyes. The large eyes indicate that Leninia hunted in great depths of water with low light intensity.
Systematics and meaning
Ichthyosaurs occupied a wide range of different ecological niches. Only a few representatives show adaptations to hunting in great water depth - the best known is the genus Ophthalmosaurus . Ophthalmosaurus was often viewed as a highly specialized exception. Various close relatives of Ophthalmosaurus are known today to exhibit the same specialized adaptations; together with Ophthalmosaurus they are summarized as Ophthalmosaurinae . Leninia as one of the last representatives of this group shows that the Ophthalmosaurinae hardly changed during their long tribal history from the Middle Jurassic to the end of the Lower Cretaceous.
Find and naming
The fossil was discovered on the right bank of the Volga, southeast of the village of Kriuschi. It was found within a loosely found calcareous concretion , which, however, probably originates from a certain local rock layer that can be assigned to the Lower Albium on the basis of its ammonite fauna .
The fossil is exhibited in the Ulyanovsk Oblast Museum of Local History . Ulyanovsk is the birthplace of Lenin , after which the genus is named. The second part of the species name, stellans , refers to the bone seam between the frontal and parietal bones , which in Leninia appears star-shaped.
Individual evidence
- ↑ a b c d e f Valentin Fischer, Maxim S. Arkhangelsky, Gleb N. Uspensky, Ilya M. Stenshin, Pascal Godefroit: A new Lower Cretaceous ichthyosaur from Russia reveals skull shape conservatism within Ophthalmosaurinae. In: Geological Magazine. Vol. 151, No. 1, 2014, ISSN 0016-7568 , pp. 60-70, doi : 10.1017 / S0016756812000994 .
- ↑ Ульяновский областной краеведческий музей имени И. А. Гончарова: Ихтиозавр из коллекции Ульяновского областного краеведческого музея описавр из коллекции в жернале . Retrieved October 15, 2015