Episode 284 is all about Astrodon, an early cretaceous sauropod named for a star shape found after cutting open its tooth.
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In this episode, we discuss:
News:
- A nearly complete Spinosaurus tail shows It would have been a capable swimmer source
- The researchers also released a 3D model of their Spinosaurus reconstruction source
- The North Carolina bill to make Hypsibema the state dinosaur has been put on hold until 2021 source
- A charity sweepstakes and auction winner will get eaten by dinosaurs in Jurassic World: Dominion source
The dinosaur of the day: Astrodon
- Sauropod that lived in the Early Cretaceous in what is now the eastern U.S.
- Estimated to be 50 to 60 ft (15 to 18 m) long
- Had shorter, wider cervical vertebrae proportionally compared to Brachiosaurus and Sauroposeiden, so may have had a short neck compared to other titanosauriformes
- Had slender radii (part of forearm)
- Not much variability in limbs between juveniles and adults, so the limbs would look similar as it aged
- Fossils found in the Arundel Formation
- In 1858 John Latchford found two dinosaur teeth in his open iron ore pit in Maryland, in Prince George’s County (found by African American slaves). Latchford sent the teeth to chemist Philip Thomas Tyson, who had Christopher Johnston, a dentist and professor at the Baltimore Dental College, study them. Johnston cut one tooth in half and saw the star-shaped cross section
- In 1859 Johnston named Astrodon, but didn’t give it a species name
- In 1865, Joseph Leidy named the type species Astrodon johnstoni (and is often cited as the one who named Astrodon)
- Charles Marsh named some fossils found near Muirkirk, Maryland as Pleurocoelus nanus and Pleurocoelus altus in 1888. In 1903 John Bell Hatcher argued Pleurocoelus and Astrodon were synonymous because the teeth were the same, and Astrodon was named first so the name stayed
- Fossils found in Oklahoma in the Antlers Formation have been assigned to Astrodon, as well as teeth found in Portugal (Lower Cretaceous), and teeth and vertebral centra found in England (European fossils have been referred to Pleurocoelus valdensis, which was named in 1890 by Lydekker, but Michael D’Emic in 2013 found this species, and all but the type species, to be nomina dubia)
- In 1921 Charles W. Gilmore said Pleurocoeulus was a junior synonym but thought there were separate species (nanus and altus)
- Other Astrodon species over the years include Astrodon valdensis, Astrodon pussilus, and in 1962 R. F. Kingham said all Brachiosaurus species were a subgenus of Astrodon
- Kenneth Carpenter and Virginia Tidwell in 2005 wrote a reassessment of Astrodon
- In 2005, Carpenter and Tidwell agreed with Hatcher that there was only one species of sauropod from the Arundel Formation, Astrodon johnstoni
- Said it was probable that the two teeth (that comprise the syntype) were not found together
- Syntype are the two teeth (syntypes are specimens that put together are what a new species is based on)
- Carpenter and Tidwell concluded there was only one species of Astrodon in the Arundel Formation, Astrodon johnstoni
- Most Astrodon fossils are from juveniles
- Carpenter and Tidwell found that the two species Marsh named (nanus and altus) were different growth stages of Astrodon johnstoni
- Not everyone agress with synonymizing Astrodon and Pleurocoelus. Peter Rose in 2007 said the teeth were hard to distinguish, and that the type series for Pleurocoelus (nanus and altus) were vertebrae and hindlimb bones, which couldn’t be compared well to the two teeth in the Astrodon syntype, and comparisons had to be with the referred specimens, which were isolated bones in the Arundel Formation, referred because of proximity and size of the bones (he also found the type material for Pleurocoelus may not be diagnostic)
- Michael D’Emic in 2013 said he didn’t find any diagnostic features of Astrodon, or either Pleurocoelus species and considered them all nomina dubia, and that the diagnostic features Carpenter and Tidwell found were too similar to other sauropods
- Michael D’Emic found “a lack of associations and non-diagnostic type specimens means that species of Astrodon and Pleurocoeulus are nomina dubia” (so only type species is still valid)
- In 1991, a local family in Maryland found a 6 ft long Astrodon femur in Laurel (many fossils have been found at that site over the years). In 2009, 41 acres were turned into Dinosaur Park, and 7.5 acres are open to the public. On the first and third Saturdays (when we’re not physically distancing), people can help paleontologists find fossils, which are then sent to the Smithsonian
- Femur is now at the Maryland Science Center in Baltimore
- Astrodon johnstoni was named the state dinosaur of Maryland in 1998
- Astrodon is one of the characters in the novel Raptor Red by Bob Bakker (Utahraptor prey)
- Can see an Astrodon model with a wound on its leg at the North Carolina Museum of Natural Sciences (in the Terror of the South exhibit)
- Can also see Astrodon model at the Maryland Science Center in Baltimore
- Habitat was flat plains with streams
- Other dinosaurs that lived in the same time and place (in modern day Maryland) included coelurosaurians, ankylosaurian Priconodon, nodosaurid Propanoplosaurus, and possibly a basal ceratopsian and ornithopod Tenontosaurus
- Also theropods Dryptosaurus, Capitalsaurus, Coelurus, Acrocanthosaurus
- And other animals included sharks, lungfish, turtles, crocodilians, early mammals, pterosaurs. Plants included cycads and conifers
- Other dinosaurs that lived in the same time and place (in modern day Oklahoma) included Sauroposeidon, Deinonychus, Acrocanthosaurus, Tenontosaurus. Other animals included amphibians, reptiles, fish, crocodilians, turtles, birds, early mammals
Fun Fact: Spinosaurus wasn’t the “crocodile of its time” because there were already (huge) crocodyliforms. But their competition may have led to the massive size of Spinosaurus.
