North side of Janusfjellet (Jurassic of Norway)

Also known as Janusaurus lundi type

Where: Spitsbergen, Norway (78.3° N, 15.8° E: paleocoordinates 69.5° N, 15.5° E)

• coordinate stated in text

• small collection-level geographic resolution

When: Dorsoplanites ilovaiskyi–Dorsoplanites maximus ammonoid zone, Slottsmøya Member (Agardhfjellet Formation), Tithonian (152.1 - 145.0 Ma)

• Slottsmøya Member, Agardhfjellet Formation, early Middle Volgian, Upper Jurassic; 31 m below the Dorsoplanites Bed, 4 m below the echinoderm bed.

•The Slottsmøya Member has been dated biostratigraphically from the Upper Volgian to Upper Ryazanian, which corresponds to about 12 million years of deposition [4,6]. The member has been divided into three units following Collignon & Hammer [3]. The lowest unit extends from the base of the member (222 m) to a yellow echinoderm marker bed. The middle unit, for which a high degree of stratigraphic resolution has been established, extends from the yellow echinoderm bed (0) to the Dorsoplanites bed (27 m), and represents 5 Ma of deposition. The upper unit ranges from the Dorsoplanites bed (27 m) to the Myklegardfjellet Beds, which is a condensed section and represents approximately 7 Ma of deposition. Evidence of carbonate seeps have also been described from the upper unit [6,7]. The specimen described in this paper (PMO 222.654) is from the lower section and is estimated to be approximately 3 Ma older than Cryopterygius kristiansenae and 2 Ma older than Palvennia hoybergeti (Figure 2).

• bed-level stratigraphic resolution

Environment/lithology: offshore shelf; sideritic, gray, silty mudstone

• marine shelf to prodeltaic succession dominated by shale, with subordinate siltstone and sandstone
• The Slottsmøya Member consists of 55-70 meters of dark grey to black silty mudstone, often weathered into paper shale. There are discontinuous silty beds, with occurrences of siderite and dolomite interbeds and yellow-to-red sideritic concretions [24]. The Slottsmøya Member records a transgressive and subsequent regressive period, with varying degrees of dysaerobic sea bottom conditions [3,26]. There was a low sedimentation rate and relatively high organic productivity in the upper water column, leading to significant accumulations of organic matter in the bottom sediments, reaching 5% in some layers [4,27].

Size class: macrofossils

Collected by PMO, Paleontological Museum Oslo, University of Oslo, Oslo, Norway in 2010

Collection methods: surface (float), surface (in situ),

Primary reference: A. J. Robert, P. S. Druckenmiller, G. Saetre and J. H. Hurum. 2014. A new Upper Jurassic ophthalmosaurid ichthyosaur from the Slottsmøya Member, Agardhfjellet Formation of central Spitsbergen. PLoS One 9(8):1-24 [R. Benson/R. Benson/R. Benson]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 159583: authorized by Roger Benson, entered by Roger Benson on 04.08.2014

Creative Commons license: CC BY (attribution)

Taxonomic list

Show authors, comments, and common names
Reptilia
 Ichthyosauria - Ophthalmosauridae
"Janusaurus lundi n. gen. n. sp." = Arthropterygius lundi
"Janusaurus lundi n. gen. n. sp." = Arthropterygius lundi Robert et al. 2014 ichthyosaur
PMO 222.654, an incomplete skeleton consisting of a partial skull, representative cervical, dorsal and caudal vertebrae, a nearly complete pectoral girdle and left forefin, the right humerus, a partial pelvic girdle and both femora