Episode 135 is all about Siats, a dinosaur named after a predatory, man-eating monster in Ute Native American mythology.

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In this episode, we discuss:

News:

The dinosaur of the day: Siats

Megaraptoran theropod that lived in the Late Cretaceous in what is now Utah, U.S.

Name comes from Siats, a predatory, man-eating monster in Ute Native American mythology

Only one species: Siats meekerorum

Species name is in honor of John Caldwell Meeker, a geologist who bequeathed a fund for paleontological research at the Field Museum in Chicago, as well as his wife Withrow Meeker, and his daughter, Lis Meeker

Described and named by Lindsay Zanno and Peter Makovicky in 2013

Lindsay Zanno found Siats in a 2008 expedition of the Field Museum, led by Peter Makovicky. They collected it between 2008 and 2010

Possibly the first neovenatorid found in North America and the youngest (geologically) allosauroid

Holotype consists of a partial postcranial skeleton (vertebrae, a chevron, partial right ilium, ischium and fibular, partial left tibia, some pedal phalanges).

Holotype is now at the Field Museum of Natural History in Chicago

Holotype is of a juvenile (neural arches of vertebrae were not fused, so it wasn’t fully grown)

No cranial materials found, except for some teeth, so how its skull looked is based on relatives

Possibly had a pointy-ish head

Had long, three-clawed arms

May have had large claws (not found, but based on close relatives such as Australovenator, Fukuiraptor, Aerosteon, and Megaraptor)

One of the largest known theropods in North America

Zanno and Mackovicky estimated its to be up to 39 ft (12 m) long and weighing about 4 tons

May have been similar in size to Saurophaganax and Acrocanthosaurus

If size estimates are correct, Siats would have been one of the largest predators found in North America

May have been an apex predator

If Siats is a neovenatorid, Siats shows that allosauroids still dominated North America (not tyrannosauroids) until the Late Cretaceous. But until last year, there was a lot of debate of how to classify megaraptors (they were either neovenatorids or tyrannosaroids). Studies of other megaraptorans have shown they are carnosaurs that had tyrannosaroid-like features, via convergent evolution

Early tyrannosaurs, that lived at the time of Siats, would have been small

When Siats lived, most herbivores were hadrosaroids and nodosaurs, but shortly after Siats, ceratopsians and ankylosaurs started thriving, and they would have been too hard for Siats to handle. This may be what allowed tyrannosaurs to grow and thrive (they were more suited to tackling these tougher prey animals)

Fun Fact:

Plant fossils are much more common than fossilized bones, but the two are very rarely found together.

Not because they didn’t get buried together

Bones are preserved best in alkaline (basic) soil

Plants are preserved best in acidic soil

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