Episode 46 is all about Alvarezsaurus, a cute, feathery dinosaur.

Thank you, thank you to our Patreon supporters! We are so lucky to have such amazing fans. If you enjoy our free weekly podcast and are interested in learning more about I Know Dino on Patreon, then please check out our Patreon page at:

https://www.patreon.com/iknowdino

You can listen to our free podcast, with all our episodes, on iTunes at:

https://itunes.apple.com/us/podcast/i-know-dino/id960976813?mt=2

In this episode, we discuss:

• The dinosaur of the day: Alvarezsaurus, whose name means “Alvarez’s lizard”
• Lived in the late Cretaceous
• Found in the Bajo de la Carpa Formation in Argentina, and named by José Bonaparte in 1991
• Named after the historian Don Gregorio Alvarez
• Not to be confused with Luis Alvarez, the physicist and amateur paleontologist who came up with the theory that an asteroid killed the dinosaurs
• Luis Alvarez and his son Walter Alvarez, a geologist, came up with the Alvarez Theory of Extinction, that a large asteroid hit earth and caused a mass extinction
• Type species is A. calvoi
• About 6.5 ft (2 m) long and weighed about 45 lbs (20 kg)
• Bipedal, with a long tail, and probably a fast runner
• Had long legs, long feet, short arms, long tail, long s-shaped neck
• Tail was over half the dinosaur’s length
• Probably had feathers or feather-like structures
• No skull found, but have found vertebrae, scapula, partial pelvis and partial hindlimbs and teeth
• Had small unserrated teeth
• May have eaten insects
• Possibly used arms for digging, though their arms were to short to dig burrows; may have clawed into rotting logs for termites
• Claw may have been used to dig out holes in termite mounds and then pick off termites (though modeling studies don’t really support this theory)
• Not completely clear what the claw was used for
• Can see Alvarezsaurus in the Discovery Channel show Dinosaur Planet, where it was shown as a predator of a juvenile Saltasaurus (though they did not live at the same time–Alvarezsaurus lived about 5 million years earlier than Saltasaurus)
• At one point Alvarezsaurus was thought to be a flightless bird, but now considered a dinosaur (actually at one point all members in the Alvarezsauridae were thought to be birds)
• Alvarezsaurus is one of the larger ones in its group
• The type genus is the least complete and least understood in the Alvarezsaur group
• Close relatives that are better known include Shuvuuia and Mononykus (Mononykus is considered more of a bird than a dinosaur)
• Different from other carnivorous dinosaurs at the same time
• Another alvarezsaurid from the same formation is Achillesaurus (one study from 2012, Makovicky, said it may be a synonym, though many people still consider it its own genus
• Alvarezsauridae is a family of small dinosaurs with long legs (could run fast)
• Alvarezsaurs are small, feathered dinosaurs with small, powerful arms with one digit (each digit had a large claw)
• Lived 88 to 66 million years ago
• Found in North and South America and Asia
• They vary in length, 20-80 in (0.5-2 m), though some may have been larger
• Ranged in size from the the size of pigeons to turkeys
• Very specialized–Have small birdlike hands, large arm muscles (good for tearing or digging), tubular snouts, long jaws, and small teeth
• They were fast and they probably used their claws to dig out ants and termites, but their arms were so short they would have had to lie on their chests against the nests to reach the insects (also possibly they did something else that has not yet been established)
• Mammals such as ant-eaters have stout, clawed arms and are toothless (similar to Alvarezsaurs)
• But the only way to know for sure what they ate would be to find a coprolite or some kind of evidence that shows what it ate
• Were thought to be the earliest known flightless birds, but now researchers think they were primitive members of Maniraptora
• In 1993 another alvarezsaur was discovereed, called Mononykus olecranus (means “one claw”), and the family Alvarezsauridae was thought to be flightless birds, based on the derived feathers unique to birds. Other members of the group later discovered were found to reinforce that idea, until Shuvuuia mongoliensis in 1998 was mistakenly described as being more derived, causing the group to be thought of as modern birds (a crown group)
• One species, Shuvuuia deserti, had preserved down-like feathery structures
• Features thought to be uniquely bird like include the elongated sternum, the palatine, cervical and caudal vertebrae
• But an analysis in 1999 found that alvarezsaurids were somewhat related to Ornithomimosauria (ostrich dinosaurs), and birdlike characteristics came from convergent evolution
• In 2007 they were places as the most basal group in Maniraptora
• Fun Fact: Cephalopods date back all the way to the Cambrian period, but the first known squid are from the Jurassic era. This means that dinosaurs were potentially eating calamari, squid were eating small dinosaurs, or both…