Episode 312 is all about Sonorasaurus, a Late Cretaceous brachiosaurid and the state dinosaur of Arizona.
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In this episode, we discuss:
News:
- The first ever hadrosaurid material was found from Africa source
- A Buriolestes braincase shows that early sauropodomorphs had better vision but worse smell than later sauropods source
- A new early Psittacosaurus-like dinosaur named Beg tse was found in Mongolia source
- The South Dakota School of Mines is repairing a T. rex jawbone that was found about 40 years ago source
- The Cabazon dinosaurs in southern California got a Christmas makeover source
- Avatar: The Last Airbender’s intro was re-made with all the benders replaced with dinosaurs source
- A couple posed for their engagement photos in dinosaur costumes, specifically T. rex and Triceratops costumes source
The dinosaur of the day: Sonorasaurus
- Brachiosaurid that lived in the Cretaceous in what is now Arizona, US (Turney Ranch Formation)
- Estimated to be 49 ft (15 m) long and 27 ft (8.2 m) tall
- Weighed about 42 tons
- Herbivorous
- Had gracile limbs, like other brachiosaurids and some titanosaurs
- Specimen found was near adult sized
- Grew slowly and sporadically compared to other sauropods, based on bone histology (compared to Giraffatitan and if similar to Giraffatitan, the specimen was nearly grown)
- Slow, irregular growth may be because of its harsh environment
- Lived in a semi-arid environment with seasonal rain and lots of evergreens (harsh environment, limited its growth)
- Paleoenvironment thought to be coastal, but no marine fossils have been found in the area, and additional analysis found the area to be terrestrial and have fluvial deposits with freshwater invertebrate fossils. Turney Ranch Formation now interpreted to be a “well-drained, semi-arid alluvial plain subject to variable precipitation events” (mostly dry, and flat, formed by deposits of sediments over time via rivers)
- Dinosaurs that lived around the same time and place included ornithopods (possibly Tenontosaurus), and stegosaurs. Also found a claw referred to Deinonychus and a tooth referred to Acrocanthosaurus
- May have been eaten by Acrocanthosaurus, based on gouge marks on the bones plus the Acrocanthosaurus tooth found nearby
- Other animals that lived around the same time and place included fish, turtles, crocodilians
- Type species is Sonorasaurus thompsoni
- Genus name means “Sonora lizard” (because of the Sonoran Desert)
- Described in 1998 by Ronald Paul Ratkevich
- He considered naming it Chihuahuasaurus, but thought that wouldn’t make sense for such a large animal (Chihuahuan Desert nearby)
- Found in November 1994 by Richard Thompson, a geology student
- Found on Thanksgiving weekend while looking for petrified wood
- Nearly complete skeleton was exposed on a rock wall
- Richard Thompson told Ronald Ratkevich, from the Arizona-Sonora Desert Museum, about his discovery, and a team excavated from 1995 to 1999
- David Thayer, curator of geology at Arizona-Sonora Desert Museum, thought it might be a therizinosaur based on the tail chevron looking like a long hand claw
- Edwin Colbert was asked to identify the dinosaur, who said based on pictures only it might be a hadrosaur
- Ratkevich and Thayer went to the AMNH and found it didn’t look like the hadrosaurs there, and thought it was a new species.
- Name Sonorasaurus was used for a few years informally
- One of the geologically youngest known brachiosaurids from North America
- Holotype includes postcranial elements (about 1/3 of a skeleton), also referred a dorsal rib (maybe)
- Holotype found to have died in an inland environment, but more study needed to establish the full range of its habitats
- For a while thought to have found a skull, but it turns out to have been a crushed dorsal vertebra
- In 1995, gastroliths were thought to be in the holotype quarry, but the presence of gastroliths in general in sauropods has been challenged, the gastroliths found may have been too polished and they were scattered around the quarry, and in the quarry are some deposits with pebbles. More evidence needed to determine if what was found were gastroliths
- Became the state dinosaur of Arizona on April 10, 2018
- Named the state dinosaur because of a letter from 11-year-old Jax Weldon, who learned about California’s state dinosaur and thought Arizona should have one, so he wrote to Governor Doug Ducey
- Jax was invited to the State Capitol and presented for 10 minutes to the senate and house, and they passed the legislation soon after
Fun Fact: Although Ajnabia is the first ever hadrosaurid from Africa, there are a couple of hadrosauroid finds from Africa.
