Episode 328 is all about Lessemsaurus, a Triassic sauropod that was large for its time in what is now Argentina.

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In this episode, we discuss:

News:

• A new raptor, Shri devi, was about the size of a Velociraptor, but had longer claws source
• Jinyunpelta had a fancy biphasal bite which switched direction mid-chew source
• The Utahraptor block is about 15% revealed and they are raising money to complete the rest source
• Dippy the Diplodocus is finishing up its tour before being bronzed and permanently housed in a garden near its original home source
• RuneScape has three new dinosaur-like bosses to battle source
• A motivational dinosaur named “cucumber” on social media is reminding people to finish everyday tasks source

The dinosaur of the day: Lessemsaurus

• Sauropod with a long neck and long tail that walked on four legs, but it’s legs were more bent than other sauropods
• Sauropod that lived in the Triassic in what is now Argentina (Los Colorados Formation in La Rioja Province)
• Estimated to be about 30 ft (9 m) long
• Weighed up to 10 tonnes
• Had tall neural spines
• Had bent legs (not columnar)
• Pretty large dinosaur, especially for the Triassic
• Grew larger in a different way from other sauropods (Diplodocus, Brontosaurus, Giraffatitan, etc.). They grew quickly and it’s thought their body structure helped, like the column like legs (to help with weight)
• Lessemsaurus bones grew in short, quick bursts
• Type and only species: Lessemsaurus sauropoides
• Described by José Bonaparte in 1999
• Genus name is in honor of Don Lessem
• Genus name means Lessem’s lizard
• “Dino” Don Lessem is a pop science writer, founder of the Dinosaur Society and the Jurassic Foundation, and the CEO of Dino Don, Inc., which makes animatronic dinosaurs and other creatures
• Bonaparte described as an unnamed advanced prosauropod in 1986, later named it in 1999
• When Bonaparte named and described Lessemsaurus, described the eight presacral neural arches, and said there were other fossils probably associated with it
• Holotype is only the eight presacral neural arches
• In 2006, Diego Pol and Jaime Powell described more Lessemsaurus fossils, including parts of the vertebral column, pectoral girdle, forelimb, pelvis, and hindlimb
• Fossils were from multiple, probably three, individuals (some duplicate bones)
• All were found in an assemblage
• Said the assemblage was probably Lessemsaurus because all the duplicate bones looked alike, all the fossils in the assemblage were distinct from other sauropodomorphs found in the area (Riojasaurus and Coloradisaurus)
• Could not determine relative length of forelimb and hindlimb elements, because of diversity in sizes and disarticulation
• Found a lot of similarities with Antetonitrus ingenipes (sauropod from the Early Jurassic in what is now South Africa)
• Because of similarities with Antetonitrus, may have been a close relationship between tetrapods in what is now South Africa and South America in the Late Triassic (needs more analysis)
• Also found derived characters shared with eusauropods, including having proportionally short and high dorsal centra (back vertebrae), pubic plate being more than 40% of the total length of the pubis, and relatively long metatarsal I (belonging to the first digit on the foot)
• Cecilia Apaldetti and others in 2018 discovered Ingentia and Lessemsaurus fossils
• Before the discovery of Ingentia and Lessemsaurus fossils, scientists thought sauropods got so large during the Jurassic and that it was linked to eusauropod modifications (column like legs, etc.)
• According to Cecilia Apaldetti and others in 2018, shows these dinosaurs started getting bigger, more than 30 million years before the first known eusauropods
• Part of the clade Lessemsauridae, which also includes Antetonitrus, Ingentia, and Ledumahadi
• Dinosaurs that lived around the same time and place include the sauropodomorph Riojasaurus, the massospondylid Coloradisaurus, the theropod Zupaysaurus

Fun Fact: Membrane-winged theropods like Yi & Ambopteryx were probably only capable of limited gliding, not flapping powered flight.

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