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

Abstract

A complete ichthyosaur rostrum, with 124 associated teeth, was recently discovered in Laux-Montaux locality, department of Drôme, southeastern France. The associated belemnites and ammonites indicate a late Valanginian age (Neocomites peregrinus Zone, Olcostephanus nicklesi Subzone) for this fossil, which consequently represents the first diagnostic ichthyosaur ever reported from Valanginian strata. This spec- imen also represents the first occurrence of Aegirosaurus outside the Tithonian (Upper Jurassic) lithographic limestones of Bavaria (southern Germany). Tooth morphology and wear pattern suggest that Aegirosaurus belonged to the “Pierce II/ Generalist” feeding guild, which was hitherto not represented in post-Liassic ichthyosaurs. Most Late Jurassic ichthyosaurs actually crossed the Jurassic-Cretaceous boundary.

A new Barremian (Early Cretaceous) ichthyosaur from western Russia

“…Thirty-four teeth are preserved. They are very small: the largest tooth measures 19 mm in total height and the tooth length index (TLI, sensu McGowan, 1976) is 0.11, which is about half that of typical toothed post-Liassic ichthyosaurs such as Platypterygius or Brachypterygius, but slightly larger than those of Aegirosaurus (Maisch and Matzke, 2000b;Fischer et al, 2011). About half of the teeth are recurved.…”

“…However, most of the ichthyosaurs used in Massare's analysis were Early Jurassic in age, coming from the well-known Hettangian-Sinemurian and Toarcian anoxic shales from Europe. The incorporation of Late Jurassic to middle Cretaceous ichthyosaurs in that canvas proved to be problematic because of the appearance of intermediate or mosaic-like dental morphologies in taxa whose diet cannot be constrained by gastric contents or bromalites (Fischer et al, 2011). Furthermore, some ichthyosaurs, which were identified as belonging to the 'Grasp: smash' guild and supposedly fed on lightly armored cephalopods, were probably far more opportunistic than hypothesized by Massare: the preserved gut of a specimen of P. australis from the Albian of Australia contained the remains of birds, fishes, cephalopods, and small turtles (Kear et al, 2003).…”

Paleoenvironmental context and significance of a partial elasmosaurid skeleton from the Albian of Haute-Provence, France

“…The root is poorly preserved but is distinctly subquadrangular in cross section as is the case in ophthalmosaurids (Fischer et al, 2012). The crown surface shows fine pits in the apical area, a condition previously reported in other ophthalmosaurids such as 'Platypterygius' hercynicus (Fischer, 2012), Aegirosaurus (Fischer et al, 2011) and in 'Platypterygius' sp. (Fischer et al, 2014).…”

Taxonomy ofPlatypterygius campylodonand the diversity of the last ichthyosaurs

“…Pervushovisaurus campylodon is also characterized by the following unique combination of features: crown with rugose texture (shared with Aegirosaurus sp., ‘ Platypterygius ’ hercynicus and ‘ Platypterygius ’ sp. specimens from France and UK Fischer et al, 2011b ; Fischer et al, 2014b ; Fischer, 2012 ); acellular cementum ring of mid-snout teeth can possess shallow apicobasal ridges and furrows (shared with ‘ Platypterygius ’ australis ) ( Maxwell, Caldwell & Lamoureux, 2011 ).…”

“…Maxilla (CAMSM B20659; CAMSM B20671a; CAMSM TN282; Figs. 2 and 3 ) —The anterior process of the maxilla is elongated and its external extent reaches the level of emergence of the nasal, as in many platypterygiines, except Aegirosaurus, Sveltonectes , and Muiscasaurus ( Romer, 1968 ; Kirton, 1983 ; Bardet & Fernández, 2000 ; Sirotti & Papazzoni, 2002 ; Fischer et al, 2011a ; Fischer et al, 2011b ; Maxwell et al, 2015 ) (note that Sirotti & Papazzoni (2002) interpreted the rostrum upside-down).…”