Episode 424: What the Titanic has to do with dinosaurs. Plus two new dinosaurs, a sauropod and a hadrosaur that both show unexpected diversity in their locales; Ornithopods had bigger brains than we thought; and more

News:

• There’s a new macronarian sauropod, Yuzhoulong, that shows more diversity in Sichuan, China than previously thought source
• A new basal hadrosaurid, Malefica, named “witch” or “sorceress” was found in Big Bend National Park source
• Ornithopods, and especially hadrosaurs, had bigger brains than we thought source
• Washington state is still working on getting a state dinosaur source
• South Australian Museum in Adelaide, Australia, has a new exhibit, Six Extinctions source

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The dinosaur of the day: Silesaurus

• Silesaurid dinosauriform that lived in the Late Triassic, in what is now Poland (Keuper Claystone)
• Looked fairly dinosaur-like, with a long tail, and long neck, and walked on all fours, and had an elongated skull
• Estimated to be about 7.5 ft (2.3 m) long
• About the size of a large dog
• Lightly built, and probably was fast and active
• Had a narrow snout, with nostrils that pointed forward
• Had large orbits in the skull so probably had good vision
• Had seven vertebrae in the neck
• Had a narrow pelvis
• Had slender ribs (“strongly crushed, which made their preparation difficult”)
• Had long, slender legs
• Had gracile front limbs
• In 2020, Piechowski and others looked at the posture and how the muscles of Silesaurus worked and found the forelimbs were fully straightened and had smaller muscles for extending the limbs, retracting, and bending (as seen in early sauropods)
• From the 2020 paper: “had pillar-erected hindlimbs like some pseudosuchians” and had “fully erect” forelimbs like early sauropods
• Had a very slender humerus and “slightly curved bone”
• Had “limited forelimb pronation”
• Authors wrote: “The forelimb can make only short steps, prohibiting fast locomotion”
• Found the “hindlimb seems to have been capable of greater speed”
• Had some adaptations to help improve speed and flexibility with the forelimbs
• Had a “pillar-erect hindlimb posture similar to that of some pseudosuchians” (before, the group of ornithodirans were thought to “have only buttress-erect limb posture”
• Had posture similar to early sauropods
• But Silesaurus also had a shorter humerus and more elongated antebrachium, so “could make longer steps and gain greater speed than early sauropods”
• Silesaurus also had a horny beak on the lower jaw
• Had a “relatively low tooth count”
• Had small, conical, serrated teeth
• Dzik, who named Silesaurus, wrote the teeth have “rather low conical shape and worn tips” and weak serration
• Not many teeth, like other early herbivorous dinosaurs
• Dzik wrote “In the shape of their crowns and pattern of serration, the teeth of Silesaurus are not similar to those of carnivorous dinosaurs” (probably herbivory)
• At first thought to be herbivorous but coprolites found later showed Silesaurus may have eaten insects, such as the beetle Triamyxa
• May have used its beak to peck on insects
• In 2019 Martin Qvarnström and others published a study on the beetle-bearing coprolites
• Relatively large size of the coprolites shows it was not from a small animal
• Coprolites ranged from 1.2 to 2.1 in (31 to 54.5 mm) long
• Coprolites had a “thin, smooth outer coating and are grey to brown in colour”
• Abundance of beetles and smaller invertebrates in the coprolites show that “the coprolite producer deliberately targeted beetles and similar small terrestrial invertebrates as prey”
• Found the “best candidate from the body fossil record of the locality is the dinosauriform Silesaurus”
• Anatomy of Silesaurus is similar to “bird-like neotheropod dinosaurs and modern birds”
• Hypothesized that Silesaurus used its beak “to efficiently peck small insects off the ground, a feeding behavior analogous to some extant birds”
• Found that the coprolites were made by “a medium-sized animal that targeted insects as prey”
• Also said it was likely that this animal also regurgitated pellets, like modern birds
• Possibly regurgitated soft prey and plant fragments
• Silesaurus had some characters similar to birds, with a shorter, more compact skull; keratinous beak
• To sum up: coprolites were found near Silesaurus fossils, and the size and shape of the coprolites, along with the beakiness of Silesaurus made it seem the coprolites came from Silesaurus
• Type species is Silesaurus opolensis
• Named by Jerzy Dzik in 2003
• Fossils found in Silesia, Poland
• Genus name means “Silesia lizard”
• Found near the city of Opole, hence the species name
• Found in clay pit in Krasiejow near Opole, southern Poland
• Found several hundred well-preserved bones
• The paper describing Silesaurus said there was “an accumulation of skeletons”
• Had enough specimens so there was a “virtually complete restoration of the skeleton”
• Collected more than 400 bones, including four partially articulated skeletons
• Where the fossils were found had a lot of exposed claystone and mudstone that was soft and easily disintegrated in water, which made the fossils “prone to destruction by weathering”
• Type specimen is an incomplete skeleton
• Skull known from disarticulated bones
• Includes the jaw bones
• In 2014, Piechowski and others proposed sexual dimorphism for Silesaurus
• Analyzed hip bones of 20 Silesaurus specimens, and found differences in the muscle tendons, and interpreted that mature females had statistically larger ossified tendons than proposed males
• Original paper said Silesaurus was a dinosauriform, with the family uncertain
• Considered to be a dinosauriform (a larger group that includes dinosaurs), and until recently, not a dinosaur (lacking features such as an enlarged deltopectoral crest, the muscle attachment on the upper arm)
• But, did have some dinosaur characteristics, such as a brevis shelf, a bone surface on the pelvis that was where tail muscles could attach)
• Hip bones were arranged like a saurischian
• Though it had beak, did not have the predentary bone seen in ornithischians
• Had leaf-shaped teeth, also seen in early ornithischians
• Had similarities to ornithischians, like Lesothosaurus
• From Dzik: “Crompton and Attridge (1986) and Sereno (1997) proposed that prosauropods might also have had a narrow horny beak at the anterior end of the upper and lower jaws. He referred to a raised bony platform on the premaxillae in Riojasaurus from the Los Colorados Formation of Argentina, and in Plateosaurus from the Knollenmergel of Germany. This is hardly visible in the original illustrations, which means that these structures are not easy to discern. This is not the case with Silesaurus, in which the area for the beak is prominent, but restricted to the lower jaw”
• “These similarities to herbivorous dinosaurs may mean that 1) Silesaurus is an early member of the ornithischian lineage, 2) belongs to the lineage leading to both the Ornithischia and Prosauropoda after its emergence from the ancestral carnivorous stock but prior to splitting, or 3) form a lineage that developed herbivory independently of dinosaurs. The fossil record of the early Late Triassic evolution of dinosaurs is too incomplete to make a reasonable choice”
• From the original paper: “Silesaurus seems to be close to the point of origin of dinosaurs both in respect to its structure and geological age”
• Also from the original paper: ““It shows most of the characters listed by Novas as diagnostic apomorphies for members of the lineage leading to dinosaurs”
• And from the original paper: “Much less obvious is the relationship of Silesaurus to dinosaurs as its skeletal anatomy is a rather bizarre combination of primitive and advanced characters”
• Not enough of the skull and hands found, which makes it hard to determine
• As of 2022, seems silesaurs now considered to be dinosaurs
• In episode 415, we covered the latest on Ornithoscelida, the proposal from 2017 that ornithischians evolved from theropods and the combination should be called “Ornithoscelida”
• The authors Norman and Baron and others now think ornithischians evolved from silesaurs, after analyzing early dinosaurs and including silesaurs
• Other papers in the past have also proposed silesaurs are ornithischians, such as the paper that described the silesaurid Sacisaurus
• Silesauridae was named as a group in 2010 by Langer and others, and there are about a dozen silesaurs
• Still some debate over what’s included, such as Pisanosaurus (covered in episode 354)
• Silesaurus lived in a subtropical environment similar to the Mediterranean today, with monsoons in the summer and dry winters
• Other animals that lived around the same time and place include fish, phytosaurs, and early pterosaurs

Fun Fact:

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