Episode 276 is all about Hesperonychus, the first microraptorine found outside of Asia.

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In this episode, we discuss:

News:

• A new abelisaurid was named Tralkasaurus meaning “thunder lizard” not to be confused with the other “thunder lizard” Brontosaurus source
• The mystery of unusual dinosaur tracks on the roof of an Australian mine has been solved source
• The Utahraptor State Park was approved by the House, but failed to pass the State Senate due to budget concerns source
• Abba Geebz plans to take his ventriloquist skills and dinosaur puppets to over 100 hospitals in the U.S. this year source
• The Carnegie Museum of Natural History will have camps this summer for kids gets 4 to 13 source
• Three Deinonychus were stolen from Eccles Dinosaur Park in Ogden, Utah, but they have been recovered source

The dinosaur of the day: Hesperonychus

• Dromaeosaurid that lived in the Late Cretaceous in what is now Alberta, Canada (Dinosaur Park Formation)
• Small bipedal carnivore
• Estimated to be under 3 ft (1 m) long and weigh about 4 lb (1.9 kg)
• Part of Microraptorinae, which was thought to be only in the Early Cretaceous in Asia until Hesperonychus
• Microraptor was the youngest known one, but Hesperonychus lived about 45 million years later
• Microraptorines are known to be small and potentially fly or glide, though Hesperonychus probably did not have four wings or glide like Microraptor, and may have been similar to Sinornithosaurus because they are similar in size
• Before Hesperonychus, small carnivorous dinosaurs hadn’t really been found in North America, which was strange because in modern ecosystems with endothermic mammals, there are more smaller species than larger ones
• Weighed about half as much as a pet cat (as the authors described it in the paper)
• Nick Longrich said it was about half the size of Velociraptor (looked like Velociraptor)
• Had sharp claws and teeth
• Had a large sickle shaped claw on its second toe
• Probably hunted and ate insects, mammals, amphibians, maybe baby dinosaurs (whatever was small enough for it to eat)
• May have spent lots of time searching for food close to the ground in marshes and forests
• Type and only species is Hesperonychus elizabethae
• Genus name means “western claw”
• Species name is in honor of Dr. Elizabeth (Betsy) Nicholls, who found the holotype
• Nicholls was curator of marine reptiles at the Royal Tyrrell Museum (died in 2004)
• Holotype is one partial pelvic girdle (part of the University of Alberta Laboratory for Vertebrate Palaeontology, Edmonton collections)
• Dr. Elizabeth Nicholls collected the holotype in 1982
• Longrich and Currie found the holotype in a drawer in 2007 (found the claws first and thought it was a juvenile, then found the pelvis with the fused hip bones and confirmed it was an adult)
• Described in 2009 by Nick Longrich and Phil Currie
• A few small toe bones, including “sickle claws” have been tentatively referred to Hesperonychus (part of the Royal Tyrrell’s collections)
• Many fragments and claws (at least 10 individuals) have been found that may be Hesperonychus, which may mean it was common in the area it was found
• Longrich and Currie said that the fact that it took 100 years after discovering Dinosaur Park Formation to describe and name the small Hesperonychus shows the preservational and collecting biases that shape how we see dinosaurs (as large and not as diverse, abundant, or ecologically important as they may have actually been, in terms of size)
• Longrich said he thinks there are lots more fossils of small carnivorous dinosaurs (especially since there are more small predators than large ones today). He said, “My gut says that when we take a good close look at the fossil record we’ll start to see this kind of animal in a lot of different places”
• Next smallest carnivore in the area was Eodelphis, a mammal that weighed 21 oz (600 g)
• Longrich and Currie think either competition from dinosaurs kept most mammals small or competition from mammals made most dinosaurs larger, or both
• Dinosaurs smaller than Hesperonychus then may have competed for food and resources with mammals. But dinosaurs Hesperonychus’ size would have been big enough to eat the largest mammals around
• Other dinosaurs that lived in the same time and place included tyrannosaurids Daspletosaurus and Gorgosaurus, also Dromaeosaurus and Saurornitholestes

Fun Fact: According to the paleobio database, the Five US states with the most (non-avian) Dinosaur fossils are Wyoming, Montana, New Mexico, Utah, and Colorado.

The full list of US dinosaur occurences listed in the paleobio database is:

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