page_title: Ichthyosaur
section_title: Fins
hierarchical_section_title: Ichthyosaur / Anatomy / Fins
caption_attribution_description: Note: not a dinosaur but an ichthyosaur
context_page_description: Ichthyosaurs are an extinct order of marine reptiles from the Mesozoic era.
  By the Upper Triassic they are similar in shape to dolphins and to fast predatory fish like tuna. They are found in marine strata from the earliest Triassic to the Cretaceous, though the early proto-ichthyosaurs are sometimes put in the broader category of Ichthyopterygia. After transitional Triassic types like Mixosaurus and Cymbospondylus, they have essentially the same body shape. Californosaurus was one of the first to have the typical dolphin-like body shape.
  Although isolated ichthyosaur vertebrae are quite common, the first fossil which showed the ichthyosaur form was found by Mary Anning and her brother Joseph. Mary Anning was an early British fossil collector, dealer and paleontologist. Many of her finds may be seen today at the Natural History Museum, London.
context_section_description: At first, the downward-pointing tail bones were hard to interpret. Then, later in the 19th century, a remarkable find was made. Some specimens of Mixosaurus and Stenopterygius were well preserved in the black mudstones of Germany. These fossils were preserved in such fine sediment that the fossils were almost perfect, with only a few bones disturbed or missing. The outline of the body shape could be seen as a thin carbon film.ᵖ¹⁰ Even though the soft parts had rotted away long ago, they left their imprint behind. For the first time, scientists could see clearly that the tail of ichthyosaurus was shaped like the tail of a fish. And on its back, like a shark, there was a dorsal fin.
caption: Unidentified ichthyosaur: body outlined (in paint) shows the tail and dorsal fins
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