Episode 376 is all about Tenontosaurus, the ornithopod which is mostly known for being eaten by Deinonychus.
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In this episode, we discuss:
News:
- A new raptor, Kuru kulla, was found in Mongolia with small hornlets above its eyes source
- Less than ten complete, articulated, sauropod necks have been described source
- The Cleveland Museum of Natural History is getting its own Dippy the Diplodocus source
- A tracksite on a sheer cliff was recreated in VR so visitors can see it source
- Dwayne “The Rock” Johnson revealed he’s a fan of Stan the T. rex, but bought a replica skull and not the original skeleton source
The dinosaur of the day: Tenontosaurus
- Ornithopod that lived in the Early Cretaceous in what is now the U.S. (Montana, Wyoming, Oklahoma, Texas, Idaho, Utah, Maryland)
- Looked kind of like Iguanodon, with a bulky body, walked on two legs or all fours, but had a longer tail
- Medium to large size
- Estimated to be 21 to 26 ft (6.5 to 8 m) long and weigh between 1 to 2 tonnes
- Had a long, broad, stiff tail
- Had a very long tail about two thirds the length of its body
- Had a relatively long forelimb
- Had a U-shaped beak
- Herbivorous
- Lots of plants around: ferns, cycads, and maybe some flowering plants
- Probably ate ferns and shrubs, maybe also wood and fruit
- Low browser; if on two legs, could have browsed food at a maximum height of 10 ft (3 m) from the ground
- Two species: Tenontosaurus tilletti and Tenontosaurus dossi
- Type species is Tenontosaurus tilletti
- Genus name means “sinew lizard”
- John Ostrom described Tenontosaurus tilletti in 1970
- Winkler, Murry, and Jacobs described Tenontosaurus dossi in 1997
- First specimen found in 1903 by a field party from the American Museum of Natural History, a fragmentary partial skeleton in Big Horn County, Montana
- More expeditions by Barnum Brown in 1931, 1932, 1933, 1938, found “partial remains of at least 18 individuals”
- Barnum Brown informally named it “Tenantosaurus” to refer to the stiff tendons in its back and tail
- A field crew from the University of Oklahoma collected at two sites in 1940, “one producing a large, virtually complete adult associated with at least four small juveniles”
- Al Silberling, a private collector, excavated two specimens for Princeton University in 1948 and 1949 (not been described, but Brown informally dubbed it Tenantosaurus)
- John Ostrom led an expedition of Yale University from 1962 to 1966 of the Cloverly Formation in Montana and Wyoming, and found 40 more specimens
- More specimens have been found since 1970 from the Cloverly Formation, Antlers Formation in Oklahoma, Paluxy Formation in Texas, Wayan Formation in Idaho, Cedar Mountain Formation in Utah, and Arundel Formation in Maryland
- Most common dinosaur in the Cloverly Formation
- “More than 80 specimens recovered from the Cloverly Formation since 1903 can be attributed to Tenontosaurus, one of the most abundant Early Cretaceous dinosaurs in North America”
- Antlers Formation of Oklahoma has 16 partial or nearly complete skeletons of T. tilletti
- Includes a nearly complete, articulated, subadult or possibly early adult
- Tenontosaurus dossi found in Parker County, Texas (Twin Mountains Formation)
- In 1970 D Andrew Thomas studied the skull of Tenontosaurus tilletti
- CT scanned the skull, which was found in the Antlers Formation of Oklahoma
- That specimen, the middle part of the tail was first found (partially eroded from the slope of a hillside within a drained pond)
- Found a sclerotic ring, though it was poorly preserved
- In 1990 Catherine Forster studied the skeleton of Tenontosaurus tilletti, found in the Cloverly Formation
- Tenontosaurus dossi first found in Texas (two articulated skeletons), and is considered to be more primitive than Tenontosaurus tilletti
- Specimens found were “unscavenged carcasses entombed in a brackish-water lagoonal or estuarine sands”
- Fossils found in Oklahoma and Doss Ranch Site in Texas as well as Wyoming and Montana
- In what is now Wyoming and Montana, the climate changed drastically during Tenontosaurus’s time, from dry to tropical, which seemed to coincide with an increase in the number of Tenontosaurus (so may have been an adaptable dinosaur)
- In 2008, Andrew Lee and Sarah Werning studied the 8 year old Tenontosaurus
- Medullary bone tissue found in the specimen (thigh and shin bone). Specimen was about 8 years old and not fully grown, based on histology
- Medullary bone has lots of calcium and forms when female birds and dinosaurs lay eggs
- Figuring out the age of reproductive maturity helps figure out dinosaur physiology, lifespan, and reproductive strategies
- Analyzed three dinosaurs known to be female, based on them having medullary bone
- Included Allosaurus that was 10 years old, T. rex that was 18, and Tenontosaurus that was 8, based on histology
- Possible they all reached sexual maturity much earlier
- As a prey dinosaur, would be beneficial to Tenontosaurus to reproduce early
- In 2012 Sarah Werning wrote about ontogenetic osteohistology of Tenontosaurus tilletti
- Lots of specimens, to show growth series
- Found subadults often had “double LAGS”, “two very closely-spaced LAGs that likely did not represent an entire year of growth between them”
- Found signs of dramatically slowed growth in adult Tenontosaurus, which happened for a few years before it was done growing/stopped growing
- Early growth and into subadulthood, Tenontosaurus tilletti was a fast grower, until it became reproductively mature. Then growth slowed down
- Similar to Rhabdodon and Zalmoxes but different from other iguanodontians, which grew quickly until they were fully grown
- Could be why Edmontosaurus and other similar dinosaurs got so much bigger (they never slowed their growth until they were done growing)
- But Tenontosaurus was sexually mature before it was fully grown
- Deinonychus fossils and teeth have been found associated with Tenontosaurus tilletti (in over 50 Tenontosaurus sites, 14 also have Deinonychus fossils)
- About 20% of Tenontosaurus fossils have been found close to Deinonychus. May mean Deinonychus was one of the main predators of Tenontosaurus
- An adult Deinonychus is smaller than an adult Tenontosaurus, so unlikely to attack alone
- Most Tenontosaurus specimens found with Deinonychus are about half-grown
- Some scientists think this could mean Deinonychus was a pack hunter, but there’s not really evidence for coordinated hunting (possibly they had mobbing behavior), and there’s evidence Deinonychus was cannibalistic and went into feeding frenzies around Tenontosaurus
- Deinonychus probably preferred juvenile Tenontosaurus, though may have scavenged larger Tenontosaurus or gone after sick or injured adults
- Covered Deinonychus in episode 14
- One Tenontosaurus found with chew marks from Deinonychus
- In 1992 Desmond Maxwell and John Ostrom wrote about the taphonomy and implications of Tenontosaurus and Deinonychus being found together
- Supported the idea of Deinonychus being a pack hunter, and that Tenontosaurus “was the specific food preference of the Deinonychus predator population”
- When Ostrom first described Tenontosaurus, he wrote that the Deinonychus specimens associated with fragments of Tenontosaurus in a quarry might be evidence that “Deinonychus probably hunted in packs of six, eight, or more predators, a group capable of bring down much larger prey animals, such as Tenontosaurus. That view has generally been accepted ever since, but not without question”
- Discovery of Tenontosaurus remains preserved with shed Deinonychus teeth (found by MoR team)
- “New discovery appears to substantiate Ostrom’s conclusion that the repeated association of Deinonychus and Tenontosaurus remains indicates a clear food preference on the part of Deinonychus”
- In 2019, T. C. Hunt and others wrote about pathologies in Tenontosaurus tilletti
- Specimen found in 2001, nearly complete, from the Antlers Formation in Oklahoma
- Nearly complete specimen, not fully grown (nicknamed “The Good Tenontosaurus” because it was so complete)
- This specimen was about 16.5 ft (5 m) long
- Used CT scans and analyzed the fossils and found five pathologies, four which came from some sort of trauma
- Seems it fell and broke ribs, broke a toe, and had a bony outgrowth on the hand bone
- Injuries healed, but would have hurt its ability to get food or escape predators
- Susceptible to more infections after
- Had osteomyelitis in and around the ribs (inflammation/infection of the bone) and on the left toe bone
- Also found a Brodie abscess, a hole in the left hand that formed when bacteria that produced pus entered the bone
- Possible the Brodie abscess happened before the other injuries, or developed after the fall (unclear, since it’s not possible to assess the state of the soft tissue)
- Only the second time a Brodie abscess was found in a dinosaur, and the first time found in an herbivore
- Would have had lots of swelling, and been hard to walk, and would have been painful to use its left hand
- Possible it lived a few months after the injuries, based on the way it healed and its infections
- Other animals that lived around the same time and place include carchaodontosaurs like Acrocanthosaurus, nodosaurs, dromaeosaurs like Deinonychus, oviraptors, sauropods, crocodilians, turtles, fish, and mammals
- Can see a statue of Tenontosaurus being attacked by Deinonychus at the Goseong Dinosaur Museum in South Korea
Fun Fact: Kuru & Shri are the first velociraptorines named from the same location, and they were both named within the last year.
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