Episode 575: A Mega Megaraptora Episode. Every megaraptoran dinosaur that has been described. Plus some that aren’t officially named like the “Lightning Claw” from the opal fields of Australia. And many that have been given other classifications—like a potential giant compsognathid.

Megaraptorids could be closely related to Tyrannosaurs, but they had lighter skeletons and large impressive hand claws. source

The megaraptorans featured in this episode:

• Megaraptor: The original megaraptorid source
• “Lightning Claw” from the opal fields in Australia source
• Fukuiraptor: A slender megaraptorid with flat hand claws source
• Phuwiangvenator: One of the oldest genera (Early Cretaceous) source
• Vayuraptor: Another old genus from Thailand source
• Rapator: Opalized left hand bone found in 1905 source
• Aerosteon: The aptly named “air bone” from Argentina source
• Australovenator: Also known as “Banjo” the largest predatory dinosaur in Australia source
• Joaquinraptor: One of the last surviving megaraptorans (Latest Cretaceous) source
• Maip: Largest known megaraptorid (30ft/9m and under 1.5 tons) source
• Murusraptor: Proportionally long snout from Argentina source
• Orkoraptor: The “toothed river thief” with specialized teeth and other features similar to compsognathids despite its large size source
• Tratayenia: Known from a handful of thin and hollow bones source
• Possible megaraptorans:
• Bahariasaurus source
• Chilantaisaurus source
• Datanglong source
• Deltadromeus source
• Eotyrannus source
• Gualicho source
• Siats source
• Vectaerovenator source
• Walgettosuchus source

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The dinosaurs of the day: Aniksosaurus & Aoniraptor

• Aniksosaurus
  • Possible megaraptoran
  • Avetheropod dinosaur that lived in the Late Cretaceous in what is now Chubut Province, Argentina (Bajo Barreal Formation)
  • In some ways, looked like Allosaurus (didn’t have the crest on the head but walked on two legs, had long arms, a long head, and a long tail)
  • Small and robust
  • Estimated to be 7 ft (2 m) to 10 ft (3 m) long and weigh up between 77 lb (35 kg) to 99 lb (45 kg)
  • Five individuals found, juvenile to sub-adults
  • Tibia was longer than the femur (shin bone longer than the thigh bone), which likely means it was a fast runner
  • Described in 2006 by Rubén Dario Martínez and Fernando Emilio Novas
  • Holotype includes a right leg and foot
  • Type and only species is Aniksosaurus darwini
  • Genus name means “spring lizard”
  • Found in the spring in the Southern Hemisphere (Sept 21, 1995)
  • Species name in honor of Charles Darwin, who visited Patagonia in 1832 to 1833
  • Details in its vertebrae, feet, legs, and hips made it unique, such as deep neural arches on its neck bones
  • Lots of debate about how to classify it, but a 2022 study found it to be a megaraptoran
  • May have been gregarious (since 5 individuals were found in a bonebed together)
  • Found five right tibiae (how they knew there were at least five individuals)
  • Buried in a fluvial environment (river or stream). Skeletons were disarticulated from the currents, then buried
  • No evidence of cannibalism or intra-species competition (why it’s thought they were gregarious. They all died together)
  • One femur has small 3mm wide tooth marks, probably from a small scavenger
  • Possible they were just gathering at a water hole and happened to be there at the same time (see this with some rhinos)
  • Two individuals estimated to be about 3 years old, based on histology
  • The 3 year olds died around the same time, which makes it seem more likely they were gregarious
  • Other theropods have been interpreted as gregarious, when found in bonebeds (Coelophysis, Albertosaurus, Sinornithomimus)
  • Crocodylians, birds, and mammals are often gregarious, and sometimes gregarious at certain life stages
  • Maybe was gregarious/social as a sub-adult (and stuck together for protection, or finding food together, but maybe was more solitary as an adult)
  • Other dinosaurs that lived around the same time and place include the abelisaur Xenotarsosaurus, sauropods such as Andesaurus and Sarmientosaurus, and ornithopods such as Notohypsilophodon
• Aoniraptor
  • Megaraptoran that lived in the Early Cretaceous in what is now Argentina (Huincul Formation)
  • Likely looked like other megaraptors
  • Walked on two legs, had a long head and a long tail, and long arms
  • Estimated to be up to 20 ft (6 m) long
  • Type and only species is Aoniraptor libertatem
  • Named in 2016 by Matías Motta and others
  • Genus name means “south thief”
  • Anoi means south in Tehuelche
  • Species name means freedom, and refers to Aoniraptor being found on the bicentennial of Argentina’s independence from Spain in 1810
  • Holotype is a partial skeleton that includes tail bones and a sacral vertebra (around the hips)
  • Individual is not skeletally mature (based on neural arches not being fused to the centra of the vertebrae)
  • Lots of similarities with Deltadromeus and Bahariasaurus (which are both potentially megaraptorans)
  • Vertebrae were long and highly pneumatic
  • Lots of air spaces in the vertebrae
  • Even the haemal arches were pneumatic (bones that attached to the bottom of the tail bones)
  • Some scientists informally considered Aoniraptor to be synonymous with Gualicho, a theropod that was found in the same formation (because of similarities with their tail bones)
  • A study in 2020 found there were lots of differences between the two dinosaurs
  • Other dinosaurs that lived around the same time and place include the theropod Gualicho, the paravian Overoraptor, carcharodontosaurs like Taurovenator and Tralkasaurus, and titanosaurs like Chucarosaurus
  • Other animals that lived around the same time and place include lizard-like reptiles and turtles

Fun Fact:

Paleontologists originally considered Megaraptor’s hand claw to be a giant foot claw. The opposite happened with Velociraptor.

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