Episode 358 is all about Sarahsaurus, a ground sloth like sauropodomorph from the Early Jurassic.

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In this episode, we discuss:

News:

• Two new spinosaurids, Riparovenator & Ceratosuchops, were found on the Isle of Wight in the UK source
• The new chasmosaurine ceratopsian, Sierraceratops, was found in New Mexico source
• Another new dinosaur, Nevadadromeus, was a bipedal herbivore from Nevada, but hasn’t been officially published yet source
• The Shandong Museum announced that they’re going to have a Cretaceous dinosaur exhibition by the end of the year source
• The Ubirajara paper has been officially withdrawn by the publisher citing “concerns regarding permissions for specimen export” source

The dinosaur of the day: Sarahsaurus

• Sauropodomorph that lived in the Early Jurassic in what is now Arizona, US (Kayenta Formation, from the Silty Facies)
• Looked kind of like a ground sloth
• Had powerful hands
• Hands were smaller than a human’s, but more powerfully built and had big claws
• Longest claw was on the first finger of the hand
• May have been an omnivore
• Had powerful shoulders
• Scapula was hourglass-shaped
• Mid-sized, estimated to be about 13 ft (4 m) long and weigh 440 lb (200 kg)
• Had a long neck and robust build
• Walked on two legs
• Had forelimbs shorter than hindlimbs
• Humerus was 61% the length of the femur
• Had long thigh bones
• Hind legs were column-like, was a bit larger, and neck vertebrae was lengthening
• Helped show that sauropod traits may have developed in smaller animals first (which helps show how sauropods grew so big)
• Didn’t have air sacs in the skeleton (postcranial skeletal pneumaticity)
• Had large eyes
• Didn’t have a good sense of smell
• No evidence it had a beak
• Lower jaw curved downwards toward the tip
• Had 20 teeth on each side of the upper jaw
• Lower jaw also had 20 teeth
• Had “moderately heterodont” teeth, that were serrated
• Type species is Sarahsaurus aurifontanalis
• Researchers found Sarahsaurus on a field trip in 1997
• Named in 2011 by Timothy Rowe, Hans-Dieter Sues, and Robert Reisz
• Took three 10-week field sessions over three years to excavate (also found a Dilophosaurus specimen)
• Holotype is a nearly complete, articulated skeleton and a fragmentary, disarticulated skull (TMM 43646-2)
• Also found, a partial skeleton (TMM 43646-3) and a nearly complete skull (MCZ 8893)
• Holotype is a mature individual, but maybe not a full adult
• Nearly complete skull (MCZ 8893) was originally thought to be Massospondylus sp.; skull was crushed and split, caused by swelling and shrinking of the clay around it after it was buried (more juvenile than holotype)
• Skull found in 1978, and later known as the “unnamed Kayenta prosauropod”
• Skull was informally known as the “Rock Head specimen” (found from the base of a geographic feature known as “Rock Head”)
• Genus name in honor of Sarah (Mrs. Ernest) Butler, a philanthropist who helped fund the “Dino Pit” exhibit at the Austin Nature and Science Center
• Timothy Rowe helped create the exhibit, and told Sarah “if she really raised a million dollars to build the Dino Pit, I’d name a dinosaur after her”
• Butler raised the money in a year
• Species name refers to Gold Spring, Arizona, where the holotype was found (means “gold of the spring” in Latin)
• Discovery of Sarahsaurus helped show that dinosaurs became more dominant after the end of the Triassic (extinction event), and not by being so fierce and outcompeting all other animals
• Timothy Rowe said in an article by the University of Texas at Austin College of Natural Sciences, dinosaurs “were humbler, more opportunistic creatures. They didn’t invade the neighborhood. They waited for the residents to leave and when no one was watching, they moved in.”
• In 2018, Adam Marsh and Timothy Rowe analyzed Sarahsaurus with additional prepared fossils and CT scans
• Found Sarahsaurus to be more closely related with sauropodomorphs from South Africa, South America, China, and Antarctica than sauropodomorphs from North America
• At the time Sarahsaurus was named, only three sauropodomorphs known from the Early Jurassic of North America (Anchisaurus and Seitaad); another one has not yet had a formal description (Fendusaurus)
• Those three are not closely related (not part of the same clade)
• Appears there were no ornithischians or sauropodomorphs in North America in the Triassic (no fossils found)
• If true, Sarahsaurus is one of the earliest North American sauropodomorphs
• Possibly came to North America after some physical barrier was removed at the end of the Triassic, or it’s possibly it took dinosaurs a long time to expand their territory
• Lived in an area with lots of streams, ponds, and lakes
• Other dinosaurs that lived around the same time and place included theropods, such as Dilophosaurus and Kayentavenator, Coelophysis, thyreophorans such as Scelidosaurus and Scutellosaurus

Fun Fact: Seagulls sometimes eat blubber out of living whales.

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This episode is brought to you by Prehistoric Pets, the new pop-up book by paleontologist Dr. Dean Lomax, illustrated by Mike Love. Prehistoric Pets takes a close look at 7 favorite pets and uses fossil clues to reveal who their prehistoric ancestors might have been. Pick up your copy at candlewick.com/r/prehistoricpets-dino