Episode 311 is all about Rapetosaurus, a titanosaur from Madagascar that is known from both juvenile and adult specimens.
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In this episode, we discuss:
News:
- SVP included talks on T. rex bite force, Archaeopteryx molting, the many types of dinosaur claws, and much more source
- The Royal Saskatchewan Museum is celebrating Dinovember with a number of virtual events this month source
- The Australian Age of Dinosaurs has 13 life-sized bronze dinosaurs source
- Victoria, the young adult T. rex, will be staying at the Arizona Science Center until January 3 source
- Robin Ruggiero has been working in the New Jersey woods since 2019 making dinosaurs from downed trees and other objects source
The dinosaur of the day: Rapetosaurus
- Titanosaur sauropod that lived in the Cretaceous in what is now Madagascar (Maevarano Formation, in Mahajanga basin)
- Quadrupedal, herbivorous
- Estimated to be 49 ft (15 m) long
- Juvenile was about 26 ft (8 m) long, adult probably about twice as long
- One specimen found is probably an adult, and based on its femur estimated to be 54 ft (16.5 m) long and weigh 10.3 tonnes
- Relatively gracile skeleton
- Skeleton has similarities to brachiosaurids and other titanosaurs
- Had a long neck and large body
- Forelimb is about 87% the length of the hind limb
- Had a slender tail
- Had long vertebrae
- Juveniles did not really have osteoderms but it had osteoderms as an adult
- Skull was like a diplodocid, long and narrow
- Adult skull is estimated to be 15.7 in (40 cm) long
- Had nostrils at the top of the skull
- Had pencil-like teeth, could strip leaves
- Type and only species: Rapetosaurus krausei
- Found by a field team from Stony Brook University and members from nearby Universite d’Antananarivo. Team leader David Krause had been digging at the site in Madagascar since 1993
- Described and named in 2001 by Kristina Curry Rogers and Catherine A. Forster
- Genus name comes from Rapeto, a mischievous giant of Malagasy folklore
- Species name is in honor of David Krause
- Holotype is an adult skull, and referred specimens include a juvenile skeleton and more skull elements
- Juvenile skeleton found directly associated with a well preserved partial skull
- One of the most complete known titanosaurs
- Helped show what a titanosaur skull looked like and helps show that Nemegtosaurus and Quaesitosaurus are titanosaurs (only known from skulls)
- Helped shed light on sauropod classification, and helped show what other titanosaurs probably looked like (ones were only partial skeletons were found)
- Kristina Curry Rogers found a juvenile in 2012 when looking through crocodile fossils at the State University of New York at Stony Brook. She recognized it as a miniature titanosaur, since she’d spent 15 years studying titanosaurs
- Juvenile fossils found in Madagascar in 1998 and 2003 but were misclassified
- Currie Rogers and others did histology and CT scans to figure out how Rapetosaurus grew (grew fast)
- Grew around the same rate as elephants
- At birth, estimated to weigh about 7.5 lb (3.4 kg); based on researchers finding a hatching line in the bones that shows subtle growth changes after hatching
- In only a few weeks it grew 10 times in weight
- Juvenile weighed about 88 lb (40 kg), and was probably between 39 and 77 days old when it died (possibly starvation due to drought)
- Probably didn’t need parental care
- Shape and proportion of its limbs appear to stay constant (isometry), so it looked like a mini adult when it was young (precocial). Also, its weight bearing bones had signs of bone remodeling, where the skeleton resorbs old bone tissue and replaces it, and that usually happens once animals can move around on their own
- And, had thin cartilage deposits in its growth plates, similar to modern birds that are precocial (animals that need parental care have thick, irregular cartilages). The preserved cartilages also had a “distinctive structure that signals starvation in living animals,” according to Curry Rogers
- Probably spent its time foraging, sleeping, and avoiding predators
- Juvenile was about 11 percent the body size of the largest known Rapetosaurus
- Lived on an island
- Lived in a semi-arid climate, in an area where sea levels were rising
- Other animals that lived around the same time and place included fish, frogs, lizards, snakes, crocodylomorphs, mammals, and birds
- Dinosaurs that lived around the same time and place included titanosaur Vahiny, dromaeosaurid Rahonavis, noasaurid Masiakasaurus, abelisaurid Majungasaurus
- Majungasaurus may have specialized in hunting sauropods (tooth marks found on Rapetosaurus bones, so definitely ate them, even if it didn’t hunt them)
Fun Fact: There is one (and maybe only one) clawed amphibian: The African clawed frog.
