Tooth id

[belemniten]

I found another tooth in Holzmaden.

It looks similar to this one:

http://www.thefossilforum.com/index.php?/gallery/image/42021-steneosaurus-tooth/

But i am not sure with Steneosaurus ...

Maybe someone can help me ?

The tooth is about 5 mm long

[izak_]

It looks to me like a pliosaurid. I am no expert, though

[Down under fossil hunter]

That or an ichthyosaur perhaps?

[belemniten]

It looks to me like a pliosaurid. I am no expert, though

That or an ichthyosaur perhaps?

Thanks both !

My own picture surprise me a bit

On the pictures its more looks like Ichtyosaurus ..... (like down under fossil hunter said)

Maybe more have an opinion ?

[abyssunder]

In the marine Jurassic deposits of Europe, a group of marine crocodilians, the Thalattosuchia, belongs to the frequently found reptiles. They were widely spread in Central Europe from the Jurassic to Lower Cretaceous with the most frequently known taxa Steneosaurus bollensis and Pelagosaurus typus and the rarely occurring taxon Platysuchus multiscrobiculatus. There are five valid thalattosuchian taxa in the Toarcian of Central Europe : Steneosaurus bollensis, Steneosaurus gracilirostris, Steneosaurus brevior, Platysuchus multiscrobiculatus, and Pelagosaurus typus (WESTPHAL 1961, 1962; VIGNAUD 1995).

Steneosaurus bollensis is the most common taxon in the Posidonia Shale.The holotype of Steneosaurus bollensis was found near Bad Boll in the Swabian Jura in the year 1712. CUVIER (1812) was the first to describe the specimen as “Gavial de Boll” and for the first time mentioned its crocodilian nature. JAEGER (1828) investigated the specimen in detail and named it Steneosaurus bollensis. During the next almost 200 years, hundreds of Steneosaurus specimens were found in the Posidonia Shales around Holzmaden, and as a result, numerous taxa were established.
The validity of these taxa was investigated by WESTPHAL (1962), in a paper about the systematic of the German and English Liassic crocodiles, and he reduced the number of taxa to five valid ones.
The dentition is weakly heterodont, because the size of the teeth is slightly variable. The teeth are slender, conical, pointed, and apically recurved. The tooth crown shows a fine vertical striation on their entire surface. In addition, it possesses one or two slightly developed faint carinae, one at the anterior and one at the posterior side. A fully erupted tooth is, in an adult specimen, about 20 mm high.

Steneosaurus gracilirostris originally come from the Toarcian deposits of the Yorkshire Coast, England and was erected by WESTPHAL (1961, 1962) based on four specimens from the Yorkshire Liassic, which had formerly been partly described by OWEN (1849/1884) and BUCKLAND (1836) as Teleosaurus chapmanni and by DESLONGCHAMPS (1877) as Pelagosaurus brongniarti.
In addition, GODEFROIT (1994) referred several specimens from the Toarcian of Luxembourg to Steneosaurus gracilirostris.
The tooth crowns are very slender, conical, pointed, and apically recurved. They bear fine vertical striations on their surface and sometimes a very faint anterior and posterior carina. Nothing distinguishes these teeth from those of Steneosaurus bollensis.

Steneosaurus brevior is known from the Liassic layers of Whitby, Great Britain and from the Liassic of Holzmaden, Germany. The UH7 specimen of Holzmaden was formerly labelled as Steneosaurus chapmanni, which is according to WESTPHAL (1962), synonym with Steneosaurus bollensis .
The tooth morphology of Steneosaurus brevior is similar to that of Steneosaurus bollensis, but the tooth crowns are slightly thicker and shorter.

Platysuchus multiscrobiculatus, exclusively known from the Holzmaden area, had been investigated by BERCKHEMER (1928, 1929) based on two specimens that he named Mystriosaurus multiscrobiculatus. WESTPHAL (1962) referred them to the new taxon Platysuchus, because the diagnostic features of the specimens, justified separation on genus level in his opinion.
The dentition is weakly heterodont, because the size of the teeth varies slightly. The teeth are slender, conical, pointed, and apically recurved. They are all covered with fine vertical striation. A particular carina is not recognized.

Pelagosaurus typus is one of the stratigrapically oldest known thalattosuchians and first occurs in the Lower Toarcian of the Schistes Carton in France. The taxon had originally been described from the Lower Toarcian, Posidonia Shale near Nabern in the Swabian Jura (BRONN 1841). French specimens from the Toarcian of Amaye–sur-Orne had formerly been described by EUDES-DESLONGCHAMPS (1864) as Teleosaurus temporalis. P. typus is the smallest of all Liassic crocodilian taxa.
The dentition is weakly heterodont, because the size of the teeth varies slightly. The tooth morphology of the teeth in the upper and lower jaw is identical. In addition, the alveoli are equally developed as circular pits in the upper and the lower jaw. The teeth are very slender, conical and apically recurved. The surface of the tooth crown is completely covered with very tiny vertical striation, but do not possess carinae like the teeth of Steneosaurus bollensis.
Because the carinae at the Steneosaurus bollensis teeth are only weakly developed and in some cases, even missing, this character does not have a great taxonomical importance . VIGNAUD (1997) already notes that the teeth of Pelagosaurus typus are similar to the teeth of Steneosaurus bollensis and Steneosaurus gracilirostris.

The teeth in the Liassic teleosaurids are generally slender, conical and apically recurved and the tooth crown is covered with a fine vertical striation. Usually but not always, the teeth of Steneosaurus bollensis and S. gracilirostris possess one or two weak carinae, one at the anterior, and one at the posterior side. The teeth of S. brevior, Platysuchus multiscrobiculatus, and Pelagosaurus typus lack a carina . The teeth of S. brevior are more robust at the base, while the teeth of Pelagosaurus typus are more slender. All teeth of the Liassic teleosaurids resemble each other with little variations in their lenght and thickness. In contrast, the teeth of some other Steneosaurus taxa e.g. from the Middle Jurassic are strongly different compared to the Liassic teleosaurid teeth. Here are examples for different tooth morphology in Steneosaurus taxa :

I think that the specimen in question shares the thalattosuchian teeth characters, but it is very hard if not impossible to narrow down to the species level judging by only one isolated tooth partially embedded in matrix, without any additional data such as the orientation and arrangement of the teeth or alveoli in the premaxilla, maxilla or dentary. On the other hand, could be an Ichthyosaurus tooth as well, like Stenopterygius from the ichthyosaur-bearing unit of Holzmaden or even a Plesiosaurus tooth. Hard to tell.

"S. quadriscissus is the only species currently known from the Lower Posidonia shale. In the Middle Posidonia shale it is joined by S. triscissus and H. n. gen. typicus. Whereas both S. quadriscissus and S. triscissus are known from the entire Middle Posidonia shale, H. n. gen. typicus is restricted to Lias ε II,2 to Lias ε II,5. S. uniter, however, is only found from Lias ε II,6 to Lias ε II,11, so H. n. gen. typicus and S. uniter exclude each other stratigraphically. Thus, there were never more than three coeval species of the Stenopterygiidae in the Posidonia shale sea of southwestern Germany. Currently, there is no evidence for sexual dimorphism in Stenopterygius."

Reference :

Anatomy, phylogeny, and palaeoecology of the basal thalattosuchians (Mesoeucrocodylia) from the Liassic of Central Europe http://ubm.opus.hbz-nrw.de/volltexte/2006/1187/pdf/diss.pdf

Revision of the genus Stenopterygius Jaekel, 1904 emend. von Huene, 1922 (Reptilia: Ichthyosauria) from the Lower Jurassic of Western Europe https://www.researchgate.net/publication/260272884_Revision_der_Gattung_Stenopterygius_JAEKEL_1904_emend_VON_HUENE_1922_Reptilia_Ichthyosauria_aus_dem_unteren_Jura_Westeuropas

High Diversity in Cretaceous Ichthyosaurs from Europe Prior to Their Extinction - Fisher et al. http://journals.plos.org/plosone/article/asset?id=10.1371%2Fjournal.pone.0084709.PDF

Edited April 18, 2016 by abyssunder

[belemniten]

I am sry for the late answer

Thanks abyssunder for this very informative and helpful anśwer !

I will sort it firstly as a thalattosuchian tooth ...

Thanks all for your help !