First record ofOphthalmosaurus(Reptilia: Ichthyosauria) from the Tithonian (Upper Jurassic) of Mexico

Abstract

From the Middle Jurassic on, the Tethys basin opened westward; the existence of a Carribean corridor linking the European and Pacific realms now appears well supported by comparison of marine reptile assemblages (e.g., Gasparini and Fernández, 1997, 2005; Gasparini et al., 2000; Fernández and Iturralde-Vinent, 2000; Gasparini and Iturralde-Vinent, 2001, 2006; Gasparini et al., 2002). Marine transgression in Mexico began during the Callovian, as evidenced by the evaporites of the Minas Viejas Fm. However, microfossils and invertebrate assemblages indicate that the Mexican Gulf remained isolated from both the European Archipelago and the Pacific, at least temporarily, until the middle Berriasian; the Florida uplift and southward movement of Yucatan were proposed as possibly forming a barrier (Salvador et al., 1993; Adatte et al., 1994, 1996; Goldhammer, 1999; Goldhammer and Johnston, 2001; Gasparini and Iturralde-Vinent, 2006). After almost a decade of field work and examination of collections, the Late Jurassic marine reptile assemblage of north-east Mexico confirms the conclusions drawn from microfossils and invertebrates. Poorly diagnostic ichthyosaur remains, with various thalattosuchians, numerically dominate the assemblage. Sauropterygians are rare, mainly represented by large pliosaurids of unclear affinities, a few vertebrae attributed to elasmosaurids, and a unique cryptoclidid. Turtles are yet to be reported (Frey et al., 2002; Buchy et al., 2003, 2005b, 2006a–d; Buchy, 2007, 2008a, b; material currently under study).

An Upper Jurassic ichthyosaur (Ichthyosauria: Ophthalmosauridae) from the Bowser Basin, British Columbia

“…The teeth are close to the size range of those found in Ophthalmosaurus cf. O. icenicus (Buchy 2010) and Sveltonectes insolitus (Fischer et al 2011). This is in contrast to the large teeth of Brachypterygius D r a f t 11 (McGowan 1976) or Platypterygius (Fischer et al 2011).…”

Cretaceous Ichthyosaurs: Dwindling Diversity, or the Empire Strikes Back?

“…This genus has been described as having small, conical teeth [55,62] with a pointed apex bearing fine longitudinal ridges [63]. The size of the teeth suggests inclusion within Massare's [59] 'smash' guild, while the crown morphology is consistent with the 'general' guild.…”

“…[11]; (B) modified from Druckenmiller and Maxwell [9]. Ichthyosaurus communis and Ophthalmosaurus icenicus now extend into the Pliensbachian [69] and Tithonian [62] So, what do the divergent phylogenetic hypotheses tell us about the origins and evolution of Cretaceous ichthyosaurs? The radiation of Platypterygius [9] or the emergence of the Platypterygiinae [11] during the Late Jurassic could coincide with the opening of the Atlantic Ocean [70], or new dispersal routes through the breakup of Gondwana [71].…”

The first definite record of a Valanginian ichthyosaur and its implications on the evolution of post-Liassic Ichthyosauria

“…The slenderness of the rostrum does not match the robust jaws of Brachypterygius (McGowan, 1976), Mollesaurus (Fernández, 1999), and Platypterygius hercynicus (Kuhn, 1946;Kolb and Sander, 2009). The retention of small, yet robust, and pointed teeth at adult stage also differs from most post-Liassic taxa, which exhibit either toothlessness or a reduced number of very small and delicate teeth (Mollesaurus, Ophthalmosaurus, Caypullisaurus, Chacaicosaurus;McGowan, 1976;Fernández, 1994Fernández, , 1999Fernández, , 2007Buchy, 2010), or are characterized by medium-sized, recurved, robust teeth with an acute but rounded apex (Undorosaurus, Brachypterygius, Platypterygius; McGowan, 1972McGowan, , 1976Massare, 1987;Bardet, 1989Bardet, , 1990McGowan and Motani, 2003;pers. obs.).…”

“…Total mandibular length (cm) reduced number of very small and delicate teeth (Mollesaurus, Ophthalmosaurus, Caypullisaurus, Chacaicosaurus;McGowan, 1976;Fernández, 1994;2007;Buchy, 2010), or are characterized by mediumsized, recurved, robust teeth with an acute but rounded apex (Undorosaurus, Brachypterygius, Platypterygius;McGowan, 1972McGowan, , 1976Massare, 1987;Bardet, 1989;McGowan and Motani, 2003;pers. obs.).…”