Episode 352 is all about Aerosteon, a Late Cretaceous megaraptoran named for its pneumatic bones.
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On this episode, we focus on:
Information:
- Two Daspletosaurus braincases have many variations, probably indicating a brand new species supply
- Two new sauropods, Hamititan & Silutitan, had been named amongst pterosaur fossils in China supply
- A key distinction in mind shapes might clarify why birds survived the Okay-Pg boundary, however non-avian dinosaurs went extinct supply
- College students from the College of Alberta are searching for somebody with a ship to assist with excavating a hadrosaur supply
- Should you stay in Victoria, Australia, you’ll be able to vote for a state fossil emblem supply
- Tokyo Dome in Japan has a Dinosaur Exhibition till September fifth supply
The dinosaur of the day: Aerosteon
- Megaraptoran that lived within the Late Cretaceous in what’s now Mendoza Province, Argentina (Plottier Formation)
- Bipedal, with an elongated cranium, robust legs and tail, and huge claws
- Preliminary estimates of about 33 ft (10 m) lengthy
- Estimated to be about 20 ft (6 m) lengthy and weigh 1,100 lb (500 kg), in response to Gregory Paul
- Molina-Pérez and Larramendi estimated Aerosteon to be 25 ft (7.5 m) lengthy and weigh 2,200 lb (1 metric ton)
- Kind species is Aerosteon riocoloradense
- Genus title means “air bone” (Greek)
- Species title refers to it being discovered 0.6 mi (1 km) north of the Río Colorado
- Species title was initially riocoloradensis, however then modified to riocoloradense to match (neuter gender)
- Fossils present in 1996
- Took years to scrub and CT scan the fossils
- First described in 2008 by Sereno and others, however on the time the ICZN didn’t acknowledge new species as legitimate if it was solely revealed on-line. In 2009, PLoS ONE labored with ICZN to make it a sound title
- Holotype contains cranium bones, neck and again vertebrae, some ribs, gastralia, furcula (want bone), shoulder bone, and extra
- Bones weren’t totally fused, so in all probability not an grownup specimen
- A part of Megaraptora, calmly constructed, superior allosauroids that had massive hand claws
- When it was named, didn’t fall into any of the three identified teams: abelisaurids, spinosaurids, carcharodontosaurids, discovered within the Cretaceous in South America
- Aerosteon “represents a particular basal tetanuran lineage that has survived into the Late Cretaceous on South America and is probably linked to the allosauroid radiation of the Jurassic”
- Fossils present a bird-like respiratory system
- Had some pneumatic bones, together with within the furcula (wishbone) and ilium and a few gastralia
- Sereno and others recommended Aerosteon’s respiratory system might have helped regulate physique temperature after which later helped with extra environment friendly respiratory
- The respiratory system might have helped with looking (operating lengthy distances) and helped it quiet down
- Based mostly on pneumaticity of among the gastralia, might imply it had air tubes underneath the pores and skin to assist with cooling
- Additionally might have helped it steadiness (higher physique weighed much less, so much less more likely to fall over when chasing prey)
- Might have had an identical air-sac system to fashionable birds, the place air sacs moved air out and in
- Talked about in episode 346, a few new Heterodontosaurus specimen helped present how ornithischians breathe
- Birds are environment friendly breathers, with unidirectional air movement
- Inhaling fills air sacs, and respiratory out empties air sacs
- Lungs all the time fill from the again (unidirectional)
- Lungs keep full the entire time, which is extra environment friendly (and with birds, helps with flying)
- Aerosteon might assist present how hen’s respiratory techniques developed
- From the 2008 paper:
- Fossil proof of the origin and evolution of air sacs is restricted, since lungs don’t fossilize and since the air sacs in fashionable birds not often pneumatize their bones and go away proof that they existed
- In Aerosteon, bones had been pneumatized by diverticulae of air sacs (so the air sac pouches led to hollowness within the bones)
- Steered a four-phase mannequin of the evolution of air sacs and respiratory system in birds
- Section I: Extra air sacs alongside the neck in basal theropods, no later than the earliest Late Triassic
- Section II: Air sacs differentiated within the Jurassic, to incorporate clavicle and belly air sacs. Air sacs could possibly be used as bellows, which can imply there have been inflexible lungs with flow-through air flow, like fashionable birds
- Section III: Primitive air pump with the sternum and ribs developed in maniraptoriforms earlier than the top of the Jurassic
- Section IV: Superior air pump developed in maniraptorans earlier than the top of the Jurassic
- Not clear from Aerosteon when unidirectional lung air flow occurred (haven’t recognized through bones uni- or bidirectional lung air flow)
- Some controversy between the authors and Matt Wedel, who posted on SV POW about findings
- Wedel wrote, “There is no such thing as a query that the fossil materials is fairly gorgeous” however that there are elements of the paper he disagreed with (had a 3 half weblog publish)
- Wedel talked about how solely residing tetrapods with postcranial pneumaticity are birds
- And mentioned in 2005, O’Connor and Claessens injected and dissected over 200 birds and located cervical diverticula by no means went additional down than the center of the thorax, so in dinosaurs pneumatic vertbrae additional down the physique in all probability had been from belly air sacs
- With dinosaurs, having pneumaticity all around the physique exhibits that they had cervical and belly air sacs, which implies that they had air sacs across the lungs, which implies they had been at the least considerably outfitted to have flow-through respiratory like birds
- Wedel disagreed with Sereno et. al saying that cervical air sacs have been discovered previous the thorax in birds (mentioned that was based mostly on papers the place the authors didn’t really say cervical air sacs went previous the thorax—pneumatization occurred from belly air sacs, and that the Aerosteon paper was dismissive of O’Connor and Claessens)
- Wedel additionally didn’t like using the phrase “pleurocoel” as a result of it’s too broad of a time period (phrase for “large pneumatic cavities which might be usually current within the vertebral centra of sauropods and theropods” that has been used to imply a number of issues) which might result in confusion
- Mentioned as a substitute of utilizing the phrase pleurocoel within the paper they need to have changed it with pneumatic foramina (means the pneumatic cavity results in inner chambers)
- Wedel additionally outlined pneumatic hiatus (a coin he termed in 2003). From a 2009 paper of Wedel’s: “Pneumatic hiatuses are gaps within the pneumatization of the vertebral column and point out pneumatization from a number of sources” (gaps the place there aren’t hole areas, which implies the hole areas had been a results of a number of sources
- Within the paper about Aerosteon, the authors mentioned saurischian adults and juveniles don’t present a pneumatic hiatus
- Wedel mentioned neither do grownup birds, as a result of birds have as much as three units of diverticula within the cervical air sacs, lungs, and belly air sacs, which meet up and provides a steady pneumatic foramina down the vertebral column (juveniles have gaps, or pneumatic hiatus, as a result of these units haven’t met up but)
- So, Wedel didn’t agree with the half about it being troublesome to defend the thought of getting three totally different pneumatic sources that resulted in a single pleurocoel (or pneumatic foramina) in Aerosteon
- Or when the authors mentioned it was problematic to immediately evaluate birds to non-avian dinosaurs in the case of pneumaticity within the posterior axial column
- Wedel mentioned the absence of the pneumatic hiatus isn’t proof that there was just one supply/path to the bone being pneumatized
- Additionally mentioned that not sufficient dinosaurs have been analyzed for pneumatic hiatus (not everybody works on pneumaticity, additionally Wedel solely coined the time period in 2003, so not a lot time had handed by the point Aerosteon was named to search for them)
- Sereno responded and mentioned it was a “deceptive, longwinded, advert hominem critique of this paper”, which led to Wedel responding
- Just a few months later, the third chapter of Wedel’s dissertation was revealed, about proof for bird-like air sacs in saurischian dinosaurs (and pneumatic hiatuses)
- An remoted tooth was referred to Aerosteon however later discovered to be the tooth of an abelisaurid
- Shut relative is Murusraptor, described in 2016, that had much less pneumatic bones (the authors who described Murusraptor discovered that the remoted tooth referred to Aerosteon was just like an abelisaurid tooth which will have been scavenging on the Aerosteen carcass)
- Very related cranium bones and vertebrae
Enjoyable Truth:
Albertosaurus & Gorgosaurus additionally went by way of a dietary shift as they grew up identical to T. rex.
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