Episode 367 is all about Anchisaurus, a sauropodomorph whose bones were first thought to be human remains when they were found in 1818.
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In this episode, we discuss:
News:
- We discuss the Dinosaur Systematics & Colbert Prize sessions from the Society of Vertebrate Paleontology annual meeting source
- A new hadrosauriform, Brighstoneus, has been described from the Isle of Wight, UK source
- The Mary Anning Rocks campaign has submitted a planning application for a statue of Mary Anning and her dog source
- The Perot Museum of Nature and Science in Dallas, TX has a reconstructed Alamosaurus source
- The Royal Ontario Museum in Toronto, Canada has a new gallery of Earth history including dinosaurs source
The dinosaur of the day: Anchisaurus
- Basal sauropodomorph that lived in the Early Jurassic in what is now Connecticut and Massachusetts, US (Portland Formation)
- Until recently considered to be a prosauropod
- Looked like a typical sauropodomorph, walked on two legs and had a long neck and tail
- Bipedal but could go on all fours
- Estimated to be 6.6 ft (2 m) long and weighed around 60 lb (27 kg)
- Marsh’s Anchisaurus major (Ammosaurus, now considered to be Anchisaurus polyzelus) was between 8 to 13 ft ( 2.5 to 4 m) long and weighed up to 70 lb (32 kg)
- Gregory Paul estimated Anchisaurus to be 7.2 ft (2.2 m) long and weigh 44 lb (20 kg)
- Lived in an arid environment, with wet and dry seasons
- Had blunt teeth, probably ate plants
- But also had a large thumb claw, possibly for defense, or grabbing tree branches
- May have been an omnivore
- Thought to be a carnivore because of the claws. According to Richard Swan Lull in the 1950s, thought Anchisaurus was “an alert, active dinosaur preying upon the smaller vertebrates of his generation, as the powerful claws and well-developed teeth imply”
- Had hands that were proportionally short to its arms
- Fossils found very early, so has a long history
- In 1973, Peter Galton wrote about the prosauropods of North America (and the history of Anchisaurus)
- Fossils first found in 1818 “during blasting operations for a well in East Windsor, Connecticut”
- Thought to be human bones in 1820, then in 1821, tail bones were reported, and Porter said they weren’t human
- Wyman in 1855 said it was reptilian and Lull in 1912 referred the fossils to Anchisaurus colurus (will get to that name later)
- First fossils found in the Connecticut Valley were fragmentary and poorly preserved and now thought be indeterminate, though some of its features suggest it’s not the same species as the ones from Manchester (found in 1884)
- In 1855 Edward Hitchcock, an ichnologist, reported fossils found in Springfield, Massachusetts, found during “blasting operations at the water shops of the United States Armory”
- Wyman described the fossils in 1858 but didn’t name it
- Fossils now at Amherst College Museum of Natural History
- Damaged from the blast, and some bones may have been accidentally thrown away by workmen or some people took them home, so fossils are incomplete
- In 1863, Hitchcock’s son, Edward Hitchcock Jr. described the fossils in a supplement to his father’s work on fossil footprints
- Hitchcock Jr. contacted Richard Owen, who told him to name a new genus based on the fossils. Owen suggested Megadactylus, which means “large finger” because it had a large thumb
- Hitchcock Jr. gave it the species name polyzelus, which means “much sought for” in Greek. Refers to his father trying to figure out for years what animal made the tracks in his work
- In 1889, Marsh described part of a skeleton found near Springfield, Massachusetts, that Hitchcock described in 1865 as Megadactylus
- Wrote, “It is a typical member of the order Theropoda, and has apparently for its nearest allies in the old world, Thecodontosaurus, from the Trias of England, and Massospondylus, from the same formation in South Africa”
- Cope described the specimen more in 1870 and Marsh renamed it to Amphisaurus (means “near saurian”) in 1882, then again to Anchisaurus (means “near lizard”) in 1885 (both names were “preoccupied”)
- More fossils were found in 1884 near Manchester, Connecticut
- In 1884, while bridges were being built, amateur paleontologist Charles Owen saw a block with part of a skeleton in it. He told Marsh, who acquired the block from Charles Wolcott, who owned the quarry. The block had the back half of the specimen
- Marsh tried to get the front half, but the block with the front half was already part of a bridge
- Marsh named it Anchisaurus major in 1889 (“the larger one”)
- In 1969 the bridge was demolished and John Ostrom got the block with the front half of the skeleton (probably the same one? hard to know). He’d been looking for the block for two years, and learned bridge builders had bought the block and used it in a local project. So he surveyed more than 60 bridges and figured out where the fossils were. Then when the bridge was scheduled to be demolished, he got permission for his team to examine it beforehand
- Three well-preserved skeletons found near Manchester, Connecticut, as well as two fragmentary specimens
- Marsh described the skeletons in multiple papers and based on them named Ammosaurus (“sand saurian”) in 1891, Anchisaurus colurus (“the mangled one”) in 1891, and Anchisaurus solus in 1892
- Anchisaurus solus is nearly complete
- In one of his papers, Marsh wrote, “one of the most slender and delicate dinosaurs yet discovered, being only surpassed in this respect by some of the smaller bird-like forms of the Jurassic”
- Also renamed Anchisaurus major as Ammosaurus in 1891
- The specimens from Manchester are now thought to be the same as Anchisaurus polyzelus
- They’re housed at the Peabody Museum of Natural History
- In 1906 Friedrich von Huene said Anchisaurus polyzelus resembled Anchisaurus colurus (both had elongate dorsal vertebrae) but still thought them to have enough differences to be different species
- Huene also referred Anchisaurus polyzelus to Thecodontosaurus based on similar radius, tibia, and fibula (Thecodontosaurus polyzelus)
- Lull in 1915 disagreed. Also said that if Huene were correct, all Anchisaurus would be a synonym for Thecodontosaurus, since Anchisaurus polyzelus is the type species
- In 1932, Huene corrected this by referring Anchisaurus solus to Ammosaurus and made Anchisaurus colurus the type species of Yaleosaurus
- He referred Anchisaurus solus to Ammosaurus because of the similarities in the ilium, tibia, and dorsal vertebrae
- In 1953 Lull accepted Yaleosaurus as valid but still recognized Anchisaurus polyzelus and Anchisaurus solus
- Holotype of Anchisaurus polyzelus does not include skull material
- In 1976 Peter Galton renamed Gryposaurus capensis bones found in South Africa (named in 1911) as Anchisaurus capensis
- But now it’s thought to be a juvenile Massospondylus carinatus
- Galton also recognized Anchisaurus polyzelus (found in Charles Wolcott’s quarry in Connecticut) and Ammosaurus major (found in Portland Beds)
- Galton referred Anchisaurus solus to Ammosaurus major
- Also found Anchisaurus colurus to be a junior synonym of Anchisaurus polyzelus and Yaleosaurus to be a synonym for Anchisaurus
- In 2008, Gauthier and Gall found Ammosaurus major to be a junior synonym of Anchisaurus polyzelus
- In 2010, Adam Yates wrote “A revision of the problematic sauropodomorph dinosaurs from Manchester, Connecticut and the status of Anchisaurus Marsh”
- Found that Anchisaurus polyzelus is the only valid one (other paleontologists had agreed, earlier)
- Found all the Wolcott Quarry specimens to be the same species
- Also found they could all be referred to Anchisaurus polyzelus
- Wolcott quarry was since been filled in
- Wolcott quarry specimens now at the Peabody Museum
- In 2007 Sereno said Anchisaurus was a nomen dubium, but Yates did not agree (not enough diagnostic characters “beyond those of basal Sauropodomorpha” found in the fragmentary holotype)
- Yates said Anchisaurus had seven distinguishing characters relating to the skull, vertebral column, and pelvis, including a slender sacral rib, and unusual proportions of the posterior dorsal centra
- Yates also supported Anchisaurus being a basal sauropodomorph
- To recap, the type species is Anchisaurus polyzelus
- Genus name means “near lizard”
- Anchisaurus was a replacement name for Amphisaurus, which was a replacement name for Megadactylus (already the names for other animals)
- Ammosaurus, Anchisaurus solus, Anchisaurus colurus (also known as Yaleosaurus) are now considered to be synonyms of Anchisaurus polyzelus
- All three dinosaur skeletons were from the same Early Jurassic-age Wolcott Quarry in Connecticut, but Marsh named them all different species: Anchisaurus major (1889), Anchisaurus colurus (1891) and Anchisaurus solus (1892)
- Hard to tell that Anchisaurus polyzelus and the Wolcott Quarry skeletons were the same dinosaur because they didn’t have too many overlapping parts of the skeleton to compare. But Yates found similarities in the hip blade and part of the fused vertebrae, which showed they were all related
- Anchisaurus was named first, so the name sticks
- In 2015, the type specimen of Anchisaurus colurus became the neotype of Anchisaurus and formally became the species Anchisaurus polyzelus
- Tracks that seem to match with Anchisaurus’s feet have been found in Nova Scotia, but hard to know for sure
Fun Fact: The Chicxulub crater that wiped out the dinosaurs created sinkholes (cenotes) that provided freshwater to the ancient Mayans.
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