A large skull of Ichthyosaurus (Reptilia: Ichthyosauria) from the Lower Sinemurian (Lower Jurassic) of Frick (NW Switzerland)

Abstract

An incomplete skull of an ichthyosaur attributed to Ichthyosaurus communis Conybeare 1822 is reported from the Lower sinemurian calcarenites (upper part of the "beggingen Member", previously "Arietenkalk", semicostatum zone) of Frick (canton Aargau, northern switzerland). It is the first record of this genus and species in switzerland, and the first definite record of the genus Ichthyosaurus from central Europe. this species was hitherto only known from Lower Hettangian to Lower sinemurian deposits of England and Upper sinemurian sediments of belgium. the specimen represents a particularly large individual that considerably exceeds all known English representatives of this species in skull length, and is closest in size to the single specimen from belgium. Unusual anatomical features include a strong coossification of the posterior skull-roof bones (probably a result of an old ontogenetic age) and a very elongate and deep excavatio internasalis. A short overview of substantial swiss Mesozoic ichthyosaur finds is provided. the Jurassic record appears very patchy so far, but has been considerably improved thanks to recent discoveries. ZUsAMMEnFAssUngDer unvollständige schädel eines Ichthyosauriers in sedimenten des Unteren sinemuriums (oberer schichtenkomplex des "beggingen-Members", bislang "Arietenkalk", semicostatum-Zone) von Frick, Kanton Aargau, schweiz wird Ichthyosaurus communis Conybeare, 1822 zugeordnet. Diese Art war bisher nur aus dem Hettangium und Unteren sinemurium von England und dem Oberen sinemurium von belgien bekannt. Es handelt sich um den ersten nachweis dieses taxons in der schweiz und um den ersten definitiven nachweis der gattung Ichthyosaurus in Mitteleuropa überhaupt. Das Exemplar besitzt eine enorme größe, die die aller englischen Exemplare weit übertrifft und dem einzigen Fund aus belgien nahe kommt. Ungewöhnliche anatomische Merkmale sind unter anderem die starke Koossifikation der posterioren schädeldachelemente, die vermutlich durch das hohe ontogenetische Alter des tieres bedingt ist, sowie eine sehr lange und tiefe Excavatio internasalis. Ein kurzer Überblick der mesozoischen Ichthyosaurierfunde der schweiz zeigt, dass insbesondere der jurassische Fossilbericht bislang sehr unvollständig ist, sich aber in den letzten Jahren durch neue Funde beträchtlich verbessert hat.

Ichthyosaurs from the Jurassic of Skye, Scotland

“…Quadrate ascending plate is robust, not a thin lamina as in Ichthyosaurus intermedius. (Modified from McGowan & Motani 2003;Maisch et al 2008;Bennett et al 2012. ) Skye material.…”

First record of the leptonectid ichthyosaur Eurhinosaurus longirostris from the Early Jurassic of Switzerland and its stratigraphic framework

“…Among Early Jurassic ichthyosaur localities, especially the claypits of Frick and Staffelegg stand out, as well as Betznau near Böttstein (Moesch, 1867;Maisch & Reisdorf, 2006a, b;Maisch et al, 2008). Further specimens have been described from Bütz/Sulz (Moesch, 1867;Peyer & Koechlin, 1934) and Schupfart (detailed informations on these fossil localities are given in Maisch & Reisdorf, 2006a, b).…”

The Staffelegg Formation: a new stratigraphic scheme for the Early Jurassic of northern Switzerland

“…Mudstone with these characteristics belongs to the Liasicus zone in the whole distribution area of the Schambelen Member, and, according to fossils found in Frick and the northern Klettgau area, possibly also to the Planorbis zone (= Untere, bituminöse Insektenmergel of Jordan 1983;Figs. 7, 10;Schlatter 1983a;Maisch et al 2008). This mudstone becomes continuously greenish grey and slightly sandy upwards.…”

“…7 Detailed section of the Early Jurassic strata at Frick (Gruhalde clay pit). a = position of the boundary between Late Hettangian and Early Sinemurian sensu Hoffmann (1934), Walliser (1956a,b) and Schlatter in Maisch et al (2008); b = position of the boundary between Late Pliensbachian and Early Toarcian sensu Schlatter (1982), Riegraf et al (1984) and Kuhn and Etter (1994: Basisschicht); c = Promicroceras cf. planicosta (SOW.…”

“…johnstoni (SOW. 1824)'' (see Maisch et al 2008: fig. 3); p = compare Etzold et al (1975); w = biostratigraphic range according to Jordan (1960) and Schlatter (1991) Fig.…”