ICHTHYOSAURS ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ Paleontological Society of Ausn ★ ★ ★ ★ ★ ★ ★ ★ ★ ★

Ichthyosaurs (Greek for "fish lizard") were large marine reples that thrived during much of the Mesozoic era; based on fossil Shastasaurus sikanniensis evidence, they first appeared approximately 250 million years ago (MYA) and at least one species survived unl about ninety MYA, into the Late Cretaceous.

There are more than 50 Ichthyosaur genera and they varied in size from 3 to over 55 feet in length. (Genera is a way biologists group Shastasaurus liangae similar species together. It is the first part of a species name. The picture to the le shows three different species, but they are all of the genus Shastasaurus.)

During the early Triassic Period, ichthyosaurs evolved from a group of unidenfied land reples that returned to the sea, in a 2 development parallel to that of the ancestors of modern-day dolphins and whales. They were parcularly abundant in the later Triassic and early Jurassic Period, unl they were replaced as the top aquac predators by Shastasaurus pacificus another marine replian group, the plesiosaurs in the later Jurassic and Cretaceous Period. In the Late Cretaceous Relave Body Size Relave Eye Size Huge Eyes ichthyosaurs became exnct for unknown . Human At up to 40 feet in length, reasons. 1 Porpoise Temnodontosaurus had Horse eyes 10 inches in Elephant diameter – the largest known eyes in the history Blue Whale of life. Their huge eyes Platypterigius allowed them to pursue kiprjanov 3 Opthalmosaurus prey in ocean’s dark depths 4

Giant Squid Platypterigius species have been found in Texas. Ichthyosaur parts including vertebrae and teeth have even been found in Travis County. Temnodontosaurus Ichthyosaur 5 They lived in Texas during the early Cretaceous Period, around 100-110 million years ago.

Convergence Flippers The ulmate resemblance Ichthyosaurs probably used their forefins (front flippers) to of ichthyosaurs to dolphins and maneuver during swimming, as in living fishes, dolphins and whales is a clear case of convergent whales. The limb skeletons went through a drasc modificaon evoluon, the independent as ichthyosaurs evolved. You can clearly see it by plong the evoluon of similar features in shape of the forefin skeleton along the family tree of species of different animals. White-sided ichthyosaurs, as in the figure below. Convergent evoluon creates Dolphin 6 structures with similar form or Petrolacosaurus Mixosaurus Macgowania Brachypterygius funcon, but that were not present Utatsusaurus Toretocnemus Stenopterygius in the last common ancestor of upper those groups. 1 Mary Anning (1799 – 1847) was an English arm fossil collector, dealer, and paleontologist. She is lower known for important finds along the English arm Channel at Lyme Regis in Southwest England. Her discoveries included the first ichthyosaur hand skeleton correctly idenfied and the first two plesiosaur skeletons found. Her family was poor. Even as a young girl she worked to help support 4 No Thumb them. Despite this, she became well known in Ichthyosaurs geological circles in Britain, Europe, and America. Nonetheless, as a woman, she was not eligible to We can make the following observaons about the evoluon of join the Geological Society of London and she did forefin skeletons in ichthyosaurs: (1) The lower arm bones not always receive full credit for her scienfic became shorter and shorter along the family tree, although contribuons. Finally, in 2010, one hundred and there are excepons; (2) The finger bones also became shorter sixty-three years aer her death, the Royal and shorter, and eventually became disk-shaped; (3) The Society included Anning in a list of the ten Brish number of finger bones increased early in the evoluon; (4) The women who have most influenced the history of thumb disappeared at one point, and then addional digits science. 1 (light blue) appeared on both sides of the remaining fingers. 4

Ichthyosaur Poster by the Paleontological Society of Ausn, licensed under Creave Commons Aribuon-ShareAlike 4.0 License. See individual restricons below. Created November 2015 by Michael K. Smith, msmith17@ausn.rr.com.

The text and images above comes primarily from Wikipedia. We cite the page, the date, and the license (if appropriate) with the original creator. Abbreviaons used - W = "hps://en.wikipedia.org/wiki". WC = "hps://commons.wikimedia.org/wiki/File:". 1. W/Ichthyosaur (Oct. 23, 2015) . CC BY-SA 3.0 Unported. 2. WC/Shastasaurus_chartDB15_2.jpg (23 Oct 2015). CC BY-SA 4.0, DiBdg. 3. WC/Platypterigius kiprjanov2.jpg (25 Oct 2015). CC BY 3.0, Dmitry Bogdanov. 4. Adapted from hp://www.ucmp.berkeley.edu/people/motani/ichthyo/, Ryosuke Motani. Used by permission. 5. From hps://openclipart.org/detail/227046/ichthyosaurus-skeleton. Public Domain, by Firkin. 6. WC/White-sided_dolphin.jpg (23 Oct 2015), CC 1.0, Skimsta.