Episode 432: Microraptor’s hawk feet and Allosaurus scavenging. Some dinosaurs had spikes on the bottom of their feet, while others had extra strong toes, the details tell us about how they lived and hunted. Plus an update on the Allosaurus scavenger hypothesis.

News:

• A critique of the controversial Allosaurus as a scavenger paper source
• Response by the original authors on why they still think Allosaurus is a scavenger source
• Microraptor had feet like a modern hawk (and what bird feet can tell us about dinosaur behavior) source
• There’s a cool trailer for Talon, about a Dakotaraptor with magical powers source

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Image by Alexoatss

The dinosaur of the day: Duriavenator

• Basal megalosaurid theropod that lived in the Middle Jurassic in what is now England (Oolite Formation)
• Briefly mentioned in episode 47, Megalosaurus
• Megalosaurus was a wastebasket taxon (David Norman in 1985 said it was used as a “dustbin”)
• Considered to be medium-sized
• Estimated to be 16 to 23 ft (5 to 7 m) long and weigh 2,200 lb (1 tonne)
• Probably looked similar to Megalosaurus, with an elongated head, long tail, and walked on two legs
• As a megalosaurid, probably had muscular arms to help catch and kill prey
• Had unique features in the jaw, including deep grooves
• Vomer (part of the bone at the middle of the palate) was similar to Allosaurus
• Had curved, serrated teeth
• Teeth were different from Megalosaurus, including in the way the front teeth of the lower jaw slanted forward
• Had heterodont teeth (different teeth), including teeth at the front of the lower jaw being longer than teeth in the back
• May have helped pluck and grasp when eating
• Had replacement teeth visible in the tooth sockets
• Type species is Duriavenator hesperis
• Genus name means “Dorset hunter”
• Species name means “the West” or “western”
• Fossils found in 1882 in Dorset, near Sherborne
• Richard Owen described the front third of the skull, including part of the upper jaw, the right maxilla, part of the bone at the middle of the palate (vomer), both dentaries (lower jaw), and other parts of the lower jaw, and associated teeth, in 1883, as Megalosaurus bucklandii
• Fossils are at the Natural History Museum in London
• Fossils found by Edward Cleminshaw, when, according to Richard Owen, “blocks of this stone were in course of preparation for a building, when indications of imbedded fossils being detected by Mr. Cleminshaw on fractured surfaces of the quarry-stones, he withdrew all such from the building yard and transmitted them to the British Museum for identification”
• The exact spot where the fossils were found is unclear, though in 1916 Richardson wrote that “The site of the quarry in which the remains were found is very near the back of the houses on the north side of Cold Harbour Road”
• Richard Owen thought the fossils were Megalosaurus bucklandii
• Megalosaurus bucklandii skull was only known from fragments
• Owen wrote the differences between the fossils Cleminshaw found and Megalosaurus bucklandii were in the size of the jaw, but the teeth were similar in size, form, and structure, so “there was no ground for predicating distinction of species”
• Owen also thought the large opening behind the maxilla was an eye socket (now known to be the opening, or fenestra, in front of the eye socket)
• Owen estimated the diameter of the eyeball to be 2 inches
• In 1926, Friedrich von Huene based his skull reconstruction of Megalosaurus bucklandii on these fossils (the specimen from Dorset)
• He also said many of the fossils assigned to Megalosaurus probably weren’t Megalosaurus
• In 1964, Alick Walker found that the specimen from Dorset was older than Megalosaurus bucklandii and “at least specifically distinct from the latter”
• Also found small differences in the jaws, and differences in the tooth sockets
• In 1974 Michael Waldman redescribed the specimen and renamed it as Megalosaurus hesperis
• Found differences in the number of teeth, and said Megalosaurus hesperis had more teeth, but that he couldn’t compare any further because there were not enough fossils
• Also found that the premaxilla similar to Allosaurus, but found Megalosaurus hesperis and Allosaurus to be different due to the way the jaws curve and the positions of the tooth carina (relates to the cutting edge of the tooth)
• Multiple people questioned Megalosaurus hesperis. Gregory Paul listed it as Megalosaurus? hesperis, and Thomas Holtz in 2000 referred to it as “Megalosaurus” hesperis, for example
• Samuel Wells and Jaime Emilio Powell planned to rename Megalosaurus hesperis as Walkersaurus, but it was not published and the name is considered to be nomen nudum
• Holtz and others in 2004 also said there was no diagnostic feature of Megalosaurus hesperis, though it could still be its own species, and Darren Naish and David Martill in 2007 found it to be a valid species but probably wasn’t Megalosaurus
• In 2008, Roger Benson and others found that only the fragment of the jaw used to name Megalosaurus was definitely Megalosaurus bucklandii, though later also found a few more fossils also belonged to Megalosaurus bucklandii
• In 2008, Roger Benson redescribed Megalosaurus hesperis and found it to be different enough to rename as Duriavenator
• Other animals that lived around the same time and place include the megalosaurid Magnosaurus, sauropods, stegosaurs, ornithopods, and marine invertebrates

Fun Fact:

There aren’t any “living fossil” species that have survived since the Mesozoic.

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