Episode 352: Dinosaur Brains – The Massive Dinosaur Podcast

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Episode 352 is all about Aerosteon, a Late Cretaceous megaraptoran named for its pneumatic bones.

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On this episode, we talk about:

Information:

Two Daspletosaurus braincases have many variations, probably indicating a brand new species supply

Two new sauropods, Hamititan & Silutitan, have 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

When you stay in Victoria, Australia, you possibly can 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), based on Gregory Paul
Molina-Pérez and Larramendi estimated Aerosteon to be 25 ft (7.5 m) lengthy and weigh 2,200 lb (1 metric ton)

Sort 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 wash 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 legitimate title

Holotype contains cranium bones, neck and again vertebrae, some ribs, gastralia, furcula (want bone), shoulder bone, and extra
Bones weren’t absolutely fused, so most likely not an grownup specimen

A part of Megaraptora, flippantly constructed, superior allosauroids that had massive hand claws

When it was named, didn’t fall into any of the three recognized 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 steered 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 searching (operating lengthy distances) and helped it calm down

Primarily based on pneumaticity of among the gastralia, might imply it had air tubes below 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)

Could have had the same air-sac system to trendy birds, the place air sacs moved air out and in

Talked about in episode 346, a couple of new Heterodontosaurus specimen helped present how ornithischians breathe

Birds are environment friendly breathers, with unidirectional air circulate
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 chook’s respiratory programs advanced

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 trendy birds not often pneumatize their bones and depart proof that they existed

In Aerosteon, bones have been pneumatized by diverticulae of air sacs (so the air sac pouches led to hollowness within the bones)

Recommended 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 stomach air sacs. Air sacs may very well be used as bellows, which can imply there have been inflexible lungs with flow-through air flow, like trendy birds

Section III: Primitive air pump with the sternum and ribs advanced in maniraptoriforms earlier than the top of the Jurassic
Section IV: Superior air pump advanced in maniraptorans earlier than the top of the Jurassic
Not clear from Aerosteon when unidirectional lung air flow occurred (haven’t recognized by way of 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 isn’t a query that the fossil materials is fairly beautiful” however that there are components of the paper he disagreed with (had a 3 half weblog publish)

Wedel talked about how solely dwelling tetrapods with postcranial pneumaticity are birds

And stated 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 most likely have been from stomach air sacs

With dinosaurs, having pneumaticity all around the physique reveals that they had cervical and stomach air sacs, which implies that they had air sacs across the lungs, which implies they have been at the least considerably geared up 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 (stated that was primarily based on papers the place the authors didn’t truly say cervical air sacs went previous the thorax—pneumatization occurred from stomach air sacs, and that the Aerosteon paper was dismissive of O’Connor and Claessens)

Wedel additionally didn’t like the usage of the phrase “pleurocoel” as a result of it’s too broad of a time period (phrase for “large pneumatic cavities which are typically 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 inside 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 have been a results of a number of sources

Within the paper about Aerosteon, the authors stated saurischian adults and juveniles don’t present a pneumatic hiatus
Wedel stated neither do grownup birds, as a result of birds have as much as three units of diverticula within the cervical air sacs, lungs, and stomach 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 tough to defend the concept of getting three totally different pneumatic sources that resulted in a single pleurocoel (or pneumatic foramina) in Aerosteon

Or when the authors stated it was problematic to instantly examine birds to non-avian dinosaurs in the case of pneumaticity within the posterior axial column

Wedel stated the absence of the pneumatic hiatus isn’t proof that there was just one supply/path to the bone being pneumatized
Additionally stated 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 stated it was a “deceptive, longwinded, advert hominem critique of this paper”, which led to Wedel responding
A couple of 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 a dietary shift as they grew up identical to T. rex.

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