page_title: Timeline of ichthyosaur research
section_title: 1990s
hierarchical_section_title: Timeline of ichthyosaur research / 20th century / 1990s
caption_attribution_description: The derived ichthyopterygian Stenopterygius with one embryo in birth position and three in body cavity, reconstructed based on SMNS 6293 (Staatliches Museum für Naturkunde, Stüttgart, Germany). .
context_page_description: This timeline of ichthyosaur research is a chronological listing of events in the history of paleontology focused on the ichthyosauromorphs, a group of secondarily aquatic marine reptiles whose later members superficially resembled dolphins, sharks, or swordfish. Scientists have documented ichthyosaur fossils at least as far back as the late 17th century. At that time, a scholar named Edward Lhwyd published a book on British fossils that misattributed some ichthyosaur vertebrae to actual fishes; their true nature was not recognized until the 19th century. In 1811, a boy named Joseph Anning discovered the first ichthyosaur fossils that would come to be scientifically recognized as such. His sister Mary would later find the rest of its skeleton and would go on to become a respected fossil collector and paleontologist in her own right.
  Early researchers recognized ichthyosaurs as marine reptiles, but major aspects of their anatomy and behavior needed to be resolved. They were frequently portrayed as leaving the water to bask on rocks and with straight tails.
context_section_description: 1990
  Bradley Kosch of Berlin-Ichthyosaur State Park criticized Camp's 1980 reconstruction of the park's famous Shonisaurus popularis as having too short a backbone and overly deep ribs, responsible for its supposedly deep pot belly. He noted that the illustration differed from both the text of Camp's published description and his own private field notes.
  Stephen Jay Gould published an article about the tail bend in ichthyosaurs.
  De Buffrenil and Mazin found a woven texture in the bones of Ichthyosaurus, Omphalosaurus, and Stenopterygius. This texture is found only in the bones of quickly growing animals, suggesting that ichthyosaurs had high metabolic rates and may even have been warm blooded.
  Massare and Callaway observed that Triassic ichthyosaurs had more elongated body plans than their Jurassic successors.
  1991
  An archaeologist named Keary Walde discovered large fossil bones near the Sikanni Chief River. He reported his discovery to the Royal Tyrell Museum. The museum's curator, Elizabeth Nicholls, was also a respected marine reptile researcher, visited the site. She was astonished to realize that the bones discovered by Walde were the remains of an ichthyosaur roughly 75 feet long, one and a half times as big as the largest known ichthyosaur at the time.
  McGowan argued that ichthyosaur fossils with new-born remains protruding from the birth canal don't imply that the mother died giving birth. Instead, they could be expelled from an already dead mother by the pressure of gas-build up as her rotting carcass bloated. An example of this in modern marine life was documented where the carcasses of beached false killer whales were given a shallow burial. Several months later, the pregnant females' fetuses had been partly expelled. He also observed that roughly 35 ichthyosaur specimens a year were still being recovered from Holzmaden. He suggested that at least some ichthyosaurs may have been warm-blooded and swift swimming like modern tuna due to their similar body plans. He also noted that even if they weren't warm blooded their large body mass would help maintain stable body temperatures.
  Lingham-Soliar referred to the swimming style of advanced ichthyosaurs whose body remained stiff while large muscles powered the tail's swimming stroke as "axial oscillation".
  Mazin and others described the new genus and species Thaisaurus chonglakmanii.
  1992
  Field work on behalf of Alberta's Royal Tyrell Museum began in the Pink Mountains of British Columbia 60 miles north of where Christopher McGowan's field work was conducted. The Royal Tyrell researchers would discover Late Triassic ichthyosaur remains in the sediments of the Pardonet Formation.
  Judy Massare proposed an explanation for the high percentage of pregnant Stenopterygius at Holzmaden. She speculated that the area was used as a breeding ground, the way whales congregate to give birth in areas of shallow water today. The coordination of a large number of births at the same time and place would increase the young's chances of survival because there would be too many for the local predator population to eat. Massare suggested that another ichthyosaur genus, Leptopterygius (now known as Leptonectes), was one such local predator that may have fed on vulnerable young ichthyosaurs.
  Nathalie Bardet dismissed claims of ichthyosaur fossils from rocks of more recent age than the Cenomanian. She also discussed possible causes for the extinction of the ichthyosaurs. She expressed doubt that ichthyosaurs were replaced by mosasaurs because they would not be in direct competition with each other. Instead she posited a connection to an extinction event that affected cephalopods at the boundary between the Cenomanian and Turonian ages. She proposed that the disappearance of these many cephalopod species may have deprived ichthyosaurs of their food source and caused their extinction.
  1993
  Charles Deeming and others published a paper on the 1985 ichthyosaur embryo discovered in Somerset. They observed that many pregnant ichthyosaur specimens contain fetuses oriented head-first toward the birt
caption: Skeletal reconstruction of a Stenopterygius with young partially evacuated from the birth canal. These specimens may not reflect the preservation of mothers in the act of giving birth, but deceased feti being expelled from her by pressure resulting from gas build up in her bloating carcass.
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