Arthropterygius, “jointed fin”, was a genus of ichthyosaur which lived in the Arctic Ocean during the Jurassic/Cretaceous transition period about 150 to 140 million years ago. Fossils of it have been found in Canada, Scandinavia, and Russia, and bones which have been ascribed to this genus have also been found in Argentina. It therefore appears that this particular ichthyosaur preferred to live in rather extreme latitudes where the climate was substantially cooler than elsewhere. The genus is currently divided into five species, most of which are dated to the end of the Jurassic Period. Only one species, Arthropterygius chrisorum is known from both late Jurassic and early Cretaceous rock layers.

Arthropterygius belonged to a group of ichthyosaurs called the “ophthalmosaurids” or “eye lizards”, named in reference to the huge size of their eyes in proportion to the rest of their bodies, although interestingly Arthopterygius‘ eyes were only moderately-sized for an ichthyosaur. Other members include the eponymous Ophthalmosaurus of Europe (and possibly North America) and Baptanodon of North America. In contrast to other members of its kind, Arthropterygius had a comparatively short nose, which was also slightly upswept towards the tip, like some species of dolphins today.

Several specimens of Arthropterygius have been found, although each of them only has the skeleton partially preserved. Even so, examination of these bones and comparing them to other more complete ichthyosaur skeletons have led paleontologists to estimate that this animal likely grew to be 12 to 15 feet long. It was also likely colored very darkly, or was perhaps even black in color, in order to absorb as much heat as possible from the cool water.

Below is my illustration of the late Jurassic / early Cretaceous ichthyosaur Arthropterygius chrisorum. This drawing was a bit unusual as the majority of it was done on my computer in Microsoft Paint rather than as a pencil drawing on paper, as I nearly always do. The outline and the ventral shading were done on paper with a No.2 pencil, but the rest was just computer-based coloration, including the amber-colored eyeball. As to whether or not this animal actually had golden yellow eyes, or if it indeed had white tips on the ends of its fins, that was just artistic license.

Arthropterygius chrisorum. © Jason R. Abdale (February 22, 2022).

Sources (listed according to date)

Lindgren, Johan; Sjövall, Peter; Carney, Ryan M.; Uvdal, Per; Gren, Johan A.; Dyke, Gareth; Schultz, Bo Pagh; Shawkey, Matthew D.; Barnes, Kenneth R.; Polcyn, Michael J. (2014). “Skin pigmentation provides evidence of convergent melanism in extinct marine reptiles”. Nature, volume 506 (January 8, 2014). Pages 484-488.

Hryniewicz, Krzysztof; Nakrem, Hans Arne; Hammer, Oyvind; Little, Crispin T. S.; Kaim, Andrzej; Sandy, Michael R.; Hurum, Jorn H. (2015). “The palaeoecology of the latest Jurassic–earliest Cretaceous hydrocarbon seep carbonates from Spitsbergen, Svalbard”. Lethaia, volume 48, issue 3. Pages 353–374.

Zverkov, Nikolay G.; Prilepskaya, Natalya E. (2019). “A prevalence of Arthropterygius (Ichthyosauria: Ophthalmosauridae) in the Late Jurassic- earliest Cretaceous of the Boreal Realm”. PeerJ, volume 7 (April 29, 2019): e6799.

Categories: Paleontology, Uncategorized

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2 replies

  1. Very neat design! I like the stylized yet potentially realistic B&W body markings, and the amber eye.

    Incidentally (author or any commenters?) I’d be fascinated to know if the ring of overlapping sclerotic bones of ichthyosaurs (also found in various other extinct reptiles, plus some extant birds) correlated with any externally-visible aspect, in life, of these huge-eyed creatures.
    For example, I note that the Waterhouse Hawkins iconic sculptures at Crystal Palace show visible radii on their eyes, but realize this may be artistic license to reveal interesting internal structure, not necessarily meant by him as life appearance.

    I gather these bones may have helped to maintain shape of the outsize eyeball, yet why needed? Would a sub-spherical eyeball not naturally retain its shape? Also, were they fixed or at all moveable for adjustments?

    • Thanks for your comment. I’m glad that you like my artwork. As to your question concerning sclerotic rings, I know next to nothing about the subject. I’m sure that there’s somebody out there who specializes in this topic. I don’t think that the bony structure would have been outwardly visible, as is seen in 19th Century artworks. As to what their purpose may have been, obviously they were there to provide structural support to the eyeball, but why would some animals have it and not others? Furthermore, there doesn’t seem to be any recognizable pattern (at least not to me) as to why certain animals have them and others don’t.

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