Episode 40 is all about Massospondylus, a sauropodomorph with thumb claws and forelimbs half the length of its hindlimbs.

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In this episode, we discuss:

• The dinosaur of the day: Massospondylus
• Lived in the early Jurassic
• Type species is Massospondylus carinatus (7 species named in 150 years, but 2 species are still valid)
• Fossils have been found in South Africa, Lesotho and Zimbabwe (other fossils originally thought to be Massospondylus but are now other species were found in Arizona, India and Argentina
• Richard Owen described it in 1854, based on fossils found in South Africa (one of the first dinosaurs named)
• Originally Owen did not think the Massospondylus bones were dinosaur bones; he thought they were “large, extinct, carnivorous reptiles” related to lizards, chameleons and iguanas
• Joseph Millard Orpen found 56 bones (including vertebrae from neck, back and tail, shoulder blade, humerus, partial pelvis, femur, tibia, and bones from hands and feet) in 1853 in South Africa and donated them to the Hunterian Museum at the Royal College of Surgeons in London. Bones were disarticulated, so it was hard to tell if they all came from the same species
• All those fossils were destroyed on May 10, 1941, when a German bomb hit the Hunterian Museum
• 80 partial skeletons and 4 skulls have been found in South Africa, Lesotho and Zimbabwe
• A skull in AZ was found in 1985, thought to be Massospondylus. It was 25% larger than other skulls found, but a recent study identified it as a new genus, Sarahsaurus
• Fossils also found in Argentina, but was named Adeopapposaurus in 2009
• Former species include M. browni (1895), M. harriesi (1911), M. hislopi (1890), M. hueni (1981), M. rawsei (1890) and M. schwarzi (1924)
• M. browni, M. harriesi and M. schwarzi found in South Africa, fragmentary material (regarded as indeterminate)
• M. hislopi and M. rawsei found in India, and M. hislopi is indeterminate but M. rawesi may be a theropod
• M. hueni was a combination of Lufengosaurus and Massospondylus (thought to be synonyms, but this is no longer accepted)
• M. kaalae (named 2009) based on a partial skull from South Africa, from same time and area as M. carinatus (but slightly different braincase)
• Other dubious, synonymous, or junior synonyms of Massospondylus include Leptospondylus, Pachyspondylus, Aristosaurus, Dromicosaurus, Gryponyx taylori, Hortalotarsus (named in 1894 but according to Broom in 1911, “Originally most of the skeleton was in the rock, and it was regarded by the farmers as the skeleton of a Bushman, but it is said to have been destroyed through fear that a Bushman skeleton in the rock might tend to weaken the religious belief of the rising generation.”
• Another synonym is Ignavusaurus
• Massospondylus was 13-20 feet (4-6 m) long, long neck and tail, small head, slender body, with sharp, long thumb claws (to help eat or used in defense), and tiny fourth and fifth digits so the forepaws looks lopsided
• Weighed around 2200 lb (1000 kg)
• 3 feet (1 m) tall and 13 feet (4 m) long
• Similar to Plateosaurus
• A 2005 study found that Plateosaurus (similar) had growth patterns based on environmental factors (when in favorable climate or around lots of food, grew fast; known as “developmental plasticity”), but this is not seen in other dinosaurs, including Massospondylus
• One study found Massospondylus grew steadily, another found it grew maximum 76 lb or 34.6 kg per year and grew until about age 15
• Forelimbs were half the length of hindlimbs, but still powerful
• Originally thought to be quadrupedal, but a 2007 study found it was bipedal
• A 2007 study found Massospondylus may have used short arms to swat at predators in defense, combat with each other, or help with feeding (arms were too short to reach mouth though)
• Had a limited range of motion, according to a 2007 study, so could not have been quadrupedal (hand could not rotate to face downwards, and forelimbs could not swing in a way similar to hindlimbs)
• Thumb claw used for digging, grooming, stripping plants, fighting
• 2007 papers support Massospondylus as a family, Massospondylidae (though knowledge of early sauropodomorphs keeps changing)
• Massospondylus was a sauropodomorph (quadrupedal herbivore) and plateosaurid (heavy thick limbed herbivores)
• Sauropodomorphs that links later sauropods to bipedal saurischians
• Massospondylus was probably an herbivore, though early sauropodomorphs may have been omnivores
• Until the 1980s, paleontologists sauropodomorphs like Massospondylus may have been carnivorous, but now they think it could only have been herbivorous or omnivorous, due to jaw articulation (according to a study in 2004 by Galton and Upchurch)
• In 2000 one paleontologist said they may have eaten small prey or carrion, and gastroliths have been found with three Massospondylus fossils in Zimbabwe
• Scientists thought gastroliths helped aid in digestion, since they couldn’t chew, but Wings and Sander in 2007 showed that the large amount of polished stones “precluded a use as an effect gastric mill in most non-theropod dinosaurs”
• 2007 Wings and Sander said sauropods did not use gastroliths, and scientists found the theropod Louinhanosaurus used gastroliths
• Had two types of teeth, small pointed teeth like theropods in the front of the mouth and spatulate teeth in the rear of the mouth (which is why debate over diet)
• Possibly had cheeks, possibly had an overbite (some scientists thought it had a beak, but this seems unlikely)
• Number of teeth varies depending on skull size; largest one has 26 teeth on each side of lower jaw
• Predators not clear, most theropods from the same time and place, such as Megapnosaurus, were smaller than Massosponylus (may have slashed quickly to wear down prey, but Massospondylus would have used its foot claws
• Another potential predator was the theropod Dracovenator (20 ft) 6 m long
• In 1976, 6-7 Massospondylus eggs (6 in or 15 cm long) was found in South Africa by James Kitching, but took 30 years to start the extraction. They are the oldest dinosaur embryos found yet
• Took five years to excavate the eggs found in 1976
• Kitching decided he didn’t have the resources to remove the fossil from the egg rock without hurting the bones, so he focused on the eggshells (until CT scanning) and found they were similar to crocodiles and birds
• In 1979, Kitching wrote a preliminary report, and found a skull well preserved, 10 mm from ear to ear
• Because the embryos couldn’t be well studied, people debated whether they were Massospondylus or even dinosaurs. A 2002 study found they were more crocodilian than dinosaurian
• 2004, Reisz and Scott from the University of Toronto studied the eggs with CAT scans, but scans were inconclusive because it was too hard to distinguish rock from bone. Scott spent a year preparing the eggs, using tiny air-driven jackhammers and thin needles to remove the rock and looking at the eggs under a high powered microscope (found two dinosaur embryos in the fetal position)
• Hard to analyze the eggs (femur is only 1.4 mm in diameter)
• This confirmed the eggs were Massospondylus
• Findings published in 2005 of two nearly complete embryonic skeletons
• Those eggs were flown to Grenoble to be examined with a CT scan at the European Synchrotron Radiation Facility
• Until CT scanning, but the x-ray resolution needed is high (six microns) so only a few places in the world could do it
• Will take a while to process all the information (1 TB) at the University of Witwatersrand’s Virtual Paleontology Lab in Johannesburg
• Additional findings published in 2012, found 10 more egg clutches, with up to 34 eggs in each
• By early 2012, 10 egg clutches from 4 fossil horizons have been found, with up to 34 eggs per clutch, so the nesting site may have been used multiple times; nesting area was near a lake and eggshells were thin (0.1 mm), so they were probably partially buried in the substrate; no hints that Massospondylus made the nests, but the eggs were arranged in tight rows (probably pushed there)
• Eggs were probably near ready to hatch; had large heads with short snouts and large eyes, short neck; forelimbs and hindlimbs were same length (quadrupedal as babies, bipedal as adults); no teeth and couldn’t move much, so had to be fed by parents until they doubled in size
• Hatchlings doubled in size before leaving the nest (based on footprint sizes)
• Mothers were too large to incubate the eggs, so they clustered them
• Nests do not have any bowl-shaped depressions or signs of nest construction
• Communal nesting site (strength in numbers to defend)
• Lake near the nest often flooded (seasonal cycle), and bad timing may have resulted in the eggs paleontologists found
• Oldest known dinosaur group nesting site (others known are 100 million years younger)
• Behavior shows complex reproductive behavior
• Sauropodomorphs (includes prosauropods, which means before the sauropods) were large, semi-quadrapeal, herbivores from the Triassic and early Jurassic
• Sauropodomorpha means “lizard feet forms” and is a suborder or unranked (established by Friedrich von Huene in 1932), broke it into two groups Prosauropoda and Sauropoda
• No gaps between prosauropod and sauropod lineages, and recent cladistic analyses suggest the clade Prosauropoda is a junior synonym of Plateosauridae
• Due to the fact that there’s no evidence it’s easier to reduce digits during evolution (prosauropods had a smaller outer toe on hindfeet compared to sauropods)
• Four families: Platesauridae, Anchisauridae, Massospindylidae, and Melanorosauridae
• Found on most continents, and some of the world’s oldest known dinosaur bones
• Most lived in Europe, probably (also found in Asia and Americas), and some found in Madagascar
• Probably herbivores, with uscular legs to stand on two feet and eat tall vegetation
• Probably traveled in groups
• They were both quadrupedal and bipedal
• Forelimbs about half the length of hindlimbs
• Mouths were like nutcrackers, but probably couldn’t chew. Instead had gastric mills in stomach walls (stones embedded that grind food), but they were inefficient, so that’s why they probably went extinct
• Had tiny skulls
• Thumb claws for defense
• Had large nostrils
• Possibly cathemeral
• Fun Fact: Elevated levels of carbon dioxide may have contributed to the initial developments and spread of angiosperm plants.