Episode 345 is all about Hypacrosaurus, a crested hadrosaurid known from several nests, including embryos.

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In this episode, we discuss:

News:

• A new hadrosauroid from Spain, Magnamanus, was discovered with a unique hole in its jaw source
• The Carnegie Museum of Natural History in Pennsylvania extended their Dinosaur Armor exhibit until July 31 source
• In Saratoga Springs, New York, Universal Preservation Hall is getting Dinosaurs in Motion from July 25 to Oct 15 source
• The Mall of America has 50 animatronic dinosaurs in its parking lot until July 11 source
• In Louisville, Kentucky, Louisville Zoo has an exhibit called Dino Quest, from now until Sept 19 source
• The 9 year old who is fighting cancer and wanted to go to Dinosaur National Monument just finished her 14 day road trip source
• Bandai Spirits, is making models of dinosaur fossils with a limestone-based plastic which they claim is more sustainable source
• The woman who owns the Flintstone house settled the lawsuit with Hillsborough, CA to keep her statues & sculptures source
• Digital exhibits and collections have grown during the pandemic source
• A new mashup music video includes Walk the Dinosaur and scenes from the TV show Dinosaurs source
• Ark: Survival Evolved has inflatable T. rex costumes in its summer-themed event until July 14 source
• A new image from Jurassic World: Dominion shows some of the “practical models” used in the film source

The dinosaur of the day: Hypacrosaurus

• Lambeosaurine hadrosaurid that lived in the Late Cretaceous in what is now Alberta, Canada and Montana, US
• Looks like Corythosaurus, and had a tall, hollow rounded crest (not quite as tall)
• Closest relatives Corythosaurus and Olorotitan
• Estimated to be 30 ft (9.1 m) long and weigh 4.4 tons
• Had a rounded, hollow crest on top of its head (sometimes described as a helmet crest)
• Crest could be for display in identifying species, and could make sounds
• Had tall neural spines, which made it look like it had a tall back
• Bipedal and quadrupedal
• Had a broad beak
• Had dental batteries with hundreds of teeth, and constantly replaced its teeth
• Ground its food in a way that resembles chewing (held food in jaws with a cheek-like organ)
• Could eat food on the ground and up to 13 ft (4 m) above the ground
• Endothermic, based on a study by Reese Barrick and others in 1996 that found the oxygen-isotope ratio found in its bones (not much variation in the ratio in the bones, so had a similar body temperature in its whole body)
• John Ruben and others in 1996 found that Hypacrosaurus had lower metabolic rates compared to modern birds and mammals
• Type species is Hypacrosaurus altispinus
• Holotype found in 1910 by Barnum Brown, and includes vertebrae, neural spines, several ribs, ilia, partial right pubis, right ischium (Horseshoe Canyon Formation); no skull found at the time
• Brown described the fossils in 1913, and said they were a new genus, similar to Saurolophus
• Genus name means “near the highest lizard”
• Named because it was almost as large as T. rex (one of the earlier named dinosaurs, so was one of the largest ones known at the time)
• Barnum Brown wrote: “It is largest of all known Trachodonts, approaching in size the great carnivorous dinosaur Tyrannosaurus of the later Lance formation.”
• Species name altispinus means “high spines” (had some of the tallest spines of hadrosaurs)
• Other specimens described after, and named as new genera and species. Includes Cheneosaurus tolmanensis (named by Lawrence Lambe in 1917), based on a skull, limb bones, vertebrae, and pelvic bones (found in Horseshoe Canyon Formation), and Procheneosaurus (named by Richard Swann Lull and Nelda Wright, and found in the Two Medicine Formation)
• Peter Dodson in the 1970s suggested these genera were probably juveniles of other lambeosaurines, and thought Cheneosaurus was juvenile Hypacrosaurus altispinus
• Procheneosaurus looked different, and later found to be Hypacrosaurus stebingeri (which wasn’t named until 1994)
• Hypacrosaurus stebingeri named based on embryos and hatchlings found near nests in the Two Medicine Formation, “the largest collection of baby skeletal material of any single species of hadrosaur known”
• Jack Horner and Phil Currie wrote about the nesting ground found of Hypacrosaurus, and named them Hypacrosaurus stebingeri
• Talked about three nesting horizons, one in Alberta, two in Montana, had many eggs and babies ranging from embryos to large nestlings (juveniles and adults also common)
• Species name in honor of the late Eugene Stebinger, who first described the Two Medicine Formation and discovered the first remains of this species
• Unusual in that it has no autapomorphies, but phylogenetically in between; said it was an intermediate taxon between species of Lambeosaurus and Hypacrosaurus altispinus (but shares more characteristics with Hypacrosaurus than Lambeosaurus)
• Worn teeth of embryos show they ground their teeth in the eggs, and teeth were functional upon hatching
• Ontogenetic changes include increase in rows of teeth, development of the nasal crest, changes in proportion of the orbits to skull size, and other changes
• David Evans in 2010 compared skulls and looked at the systematics of Hypacrosaurus altispinus
• Looked at 15 skulls
• Found that the crest grew larger as it aged
• Nasal passage had an s-loop, with the lower half extending to the skull roof level
• Lots of Hypacrosaurus specimens ranging from embryos to adults
• Gregory Erickson and others decided to look at Hypacrosaurus and Protoceratops embryos in 2016
• Used CT scans and found Hypacrosaurus incubated in 171 days, much longer than expected
• Based on lines of growth in the embryo teeth
• Daily growth lines called von Ebner lines, which are formed when the enamel forms on embryo teeth. Liquid dentin (layer under the enamel) fills inside the tooth and mineralizes every night. Once the tooth is completely filled in, the lines stop forming
• von Ebner lines used to find tooth-formation and incubation times in alligators, humans, and other mammals before
• Long incubation times not good during extinction event
• Young and embryonic specimens had deep skulls and a slight expansion in the bones (that would turn into a crest)
• Hypacrosaurus egg was about 8.8 lb (4 kg) (Ostrich eggs are a little over 1 kg)
• Lisa Cooper and others studied a Hypacrosaurus specimen in 2008 and looked at LAGs (specimen thought to be about 13 years old)
• Reproductively mature by age 2 or 3 (so can reproduce quickly, a sign of being a prey animal)
• Grew faster than tyrannosaurids (which preyed upon it; tooth marks found in a fibula), so could get large enough quickly to defend itself
• May have reached full size at age 10 or 12, compared to tyrannosaurs that take 20 to 30 years (based on growth rings in leg bones)
• Alida Bailleul and others in 2020 found cartilage traces on a hatchling skull of Hypacrosaurus stebingeri
• Isolated some cells to test with DNA staining. Tested positive to possible chemical markers of DNA, in a way similar to emu cells (they dyed living emu cells and compared the two)
• Didn’t think it was fossil contamination, which may mean DNA lasts longer than previously thought
• Used two types of stains, one that attached to DNA fragments and dead cells, and one that attached to any DNA. They were binding to specific molecules and not the whole cell, which is why the team did not think there was bacterial contamination
• Cells came from cartilage in the skull of a baby Hypacrosaurus
• Found cells that looked to be frozen and in the process of dividing, cells with nuclei, and one cell that seems to contain something that resembles chromosomes
• Structures within certain tissues were consistent with cartilage cells, and they had internal structures that resembled nuclei and chromosomes
• Pieces too short to read to confirm if it is DNA
• Supports idea that some fragmentary DNA may remain in the cells
• Needs more research, but if upheld, it means biochemical traces of animals could stick around tens of millions of years longer than previously thought
• But, may be too difficult to tell when the traces of DNA come from a dinosaur, or they just look like they come from a dinosaur, but it’s DNA traces of something else, like bacteria and other microorganisms (as Renxing Liang and others found on a Centrosaurus)
• Still early days, need more research (lots of unknowns) and maybe more standardized processes (team tested Hypacrosaurus with DNA staining, and the Centrosaurus team used DNA sequencing); also the ability to replicate
• Other dinosaurs that lived in the same time and place as Hypacrosaurus altispinus (Horseshoe Canyon Formation) included hadrosaurids Edmontosaurus and Saurolophus, hypsilophodont Parksosaurus, ankylosaurid Anodontosaurus, nodosaurid Edmontonia, ceratopsians Montanoceratops, Anchiceratops, Arrhinoceratops, and Pachyrhinosaurus, pachycephalosaurid Stegoceras, ornithomimosaurs Ornithomimus and Struthiomimus, tyrannosaurs Albertosaurus and Daspletosaurus, and troodontids and dromaeosaurids
• Other dinosaurs that lived in the same time and place as Hypacrosaurus stebingeri (Two Medicine Formation) include the hadrosaurs Maiasaura and Prosaurolophus, troodontid Troodon, tyrannosaurid Daspletosaurus, caenagnathid Chirostenotes, dromaeosaurids Bambiraptor and Saurornitholestes, ankylosaurs Edmontonia, Oohkotokia, and Scolosaurus, hypsilophodont Orodromeus, and ceratopsians Achelousaurus, Brachyceratops, Einiosaurus, and Rubeosaurus. Area was further away from the Western Interior Seaway, so higher and drier than Horseshoe Canyon Formation

Fun Fact: The US has a national dinosaur (the bald eagle). Although they don’t eat people, they do sometimes eat raccoons & seal pups.

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