Like a Bird

Welp, I am finally published! Say hello to some new birds from the Paleogene!!!

Island Weirdness #08 – Balaur bondoc

When Balaur was described in 2010 it was initially thought to be a dromaesaurid closely related to Asian forms like Velociraptor. With its particularly stocky legs built for strength rather than speed, two-fingered hands, and two large sickle claws on each foot, it was interpreted as a weird highly specialized predator terrorizing the other Hațeg Island species at the end of the Cretaceous. Although only 1.8m long (5'10"), it was hypothesized to have taken down prey much larger than itself with powerful slashing kicks.

But later analyses cast doubt on this interpretation.

A lot of the anatomical features of Balaur’s skeleton were odd for a dromaeosaurid, but matched those of avialans – a group of close evolutionary “cousins” to the dromaeosaurids, containing Archaeopteryx and the common ancestors of all modern birds. And, by 2015, multiple studies had confirmed Balaur wasn’t really a “raptor” but instead a little further along on the bird lineage.

So now our picture of this dinosaur is very different: a chunky-bodied island bird, grown large and secondarily flightless sort of like a Cretaceous equivalent to the dodo. Its double sickle claws were probably adaptations for climbing and perching in trees, and based on similar avialans it was likely a herbivore rather than a hypercarnivore.

@daalseth replied to your photo “Island Weirdness #08 – Balaur bondoc When Balaur was described in 2010…”

Not that I know of. I think the skeletal features were always clearly paravian, even if it initially got put into the wrong branch of that group.

Paleontologists were smart enough to avoid that particular mistake (there’s a lot more to tyrannosaur hands than having two fingers), but I believe the partial forelimb of the referred specimen was originally thought to be a caenagnathid oviraptorosaur!

Because Caenagnathosauria does not exist as a name.

To elaborate on why Caenagnathoidea exists and Caenagnathosauria does not: Caenagnathidae, Caenagnathoidea, Oviraptoridae, and Oviraptoroidea are what are known as family-group names. There are officially five types of family-group names, distinguished by suffix added to a genus-based root:

According to the ICZN (the International Code of Zoological Nomenclature), when any family-group name is created, the other four are automatically created as well. So when Caenagnathidae was created in 1940, Caenagnathoidea was also automatically created. 36 years later, Oviraptoridae was created, and so was Oviraptoridae. 

Caenagnathosauria does not have one of those suffixes, so it does not follow the rules of family-group taxa that allow names to be created indirectly. This means that, for Caenagnathosauria to exist, somebody would have had to explicitly use that name in the paper. Nobody has done so, so the name Caenagnathosauria does not exist.

We don’t know; this is a major source of debate among sauropod researchers.

Some researchers, such as Kent Stevens, have argued that all sauropods held their necks close to horizontal. Yes, even Brachiosaurus.

Other researchers, such as Mike Taylor, have argued that all sauropods held their necks up most of the time. Even Diplodocus.

It’s generally agreed that diplodocoids held their neck more horizontally than other sauropods and that brachiosaurids held their necks the most upright of all, but beyond that, it’s hard to say. The debate is likely to go on for some time, as interpreting the neck posture of sauropods depends on a wide variety of poor information: it’s unclear whether any sauropod necks are well-preserved enough to provide useful information, neck cartilage would affect posture but isn’t preserved, and pretty much every living animal used for comparison isn’t very sauropod-like. 

Since 2016, there has been some debate over whether sauropods are actually more closely related to theropods than ornithischians, with one team of researchers arguing that ornithischians were more closely related to theropods than sauropods. This is known as the Ornithoscelida hypothesis. If the Ornithoscelida hypothesis is true, the Iguanodon+Megalosaurus definition of Dinosauria would not include sauropods.

However, the Ornithoscelida hypothesis is not considered correct by most scientists. Only the people who originally suggested the idea really seem to believe it, and their analysis has been met with substantial criticism and is generally considered to be flawed. The traditional Saurischia hypothesis (that sauropods are closer to theropods than ornithischians) is generally considered valid.

So you’re correct: the clade of the common ancestor of Iguanodon and Megalosaurus almost definitely includes sauropods, too. However, some people want to include Diplodocus in the definition just to be safe, in case the Ornithoscelida hypothesis is correct after all.

One therocephalian, Euchambersia, probably did have a venomous bite! 

It was not a contemporary of Lystrosaurus. Some of its relatives were, but I don’t think there’s any evidence of them having been venomous.

DINOSAURS OVER THE YEARS

This is a series of posters I made to show how our perception of Dinosaurs and other animals of the mesozoic changed over the years. These and few more are featured in a Youtube video you can watch HERE

this art is available for prints, t-shirts and other goods HERE

http://mariolanzas.tumblr.com/

This is really cool, but I just want to say that paleontologists didn’t think Apatosaurus had sprawling limbs in the 1870s—they did in the 1900s, or rather some of them did.

This is what Camarasaurus looked like in 1877. By the late 1870s, paleontologists had a pretty good idea of what sauropods looked like. Abundant fossils from the western US had revealed most of the anatomy of sauropods, and it was obvious that they had upright limbs.

Well, obvious to most people. In the early 1900s, the herpetologists Oliver P. Hay and Gustav Tornier argued that the field of paleontology had it all wrong and that sauropods had sprawling limbs like lizards. This led to a huge, international argument between the American paleontologists who had been studying the fossils for years and the German Tornier. Even the Kaiser got involved.

This also led to what is possibly the most sarcastic academic paper ever written, William J. Holland’s epic takedown of Hay and Tornier’s claims. “As a contribution to the literature of caricature the success achieved is remarkable,” Holland says of Tornier’s reconstruction, before explaining how the deep pelvis of sauropods would have forced a sprawling Diplodocus to live in deep trenches:

“This might perhaps account for its early extinction,” Holland concludes.

Please read that paper if you have the time, it is an experience.

Here’s the full paper for those interested: https://www.nature.com/articles/s41559-018-0728-7.epdf?shared_access_token=wsj4P5pKcG3NWkJW-AmpRtRgN0jAjWel9jnR3ZoTv0OhuDOmy4G-1OHvOkIfGGVa07EOVX4CcCn1ujEjIGdNkUvzBZug8tPjjaWNG4bQuVMptkL5xktsqRha5pWB32jiQniNwh5I29FN9QSZBgCnOnLfkJRv_sadxY_WtSQWxj4%3D

So now we have clear evidence that pterosaur fuzz looked an awful lot more like dinosaur feathers than previously thought, with several different types of branching filaments and even downy structures. Either this is some remarkable convergent evolution, or – probably more likely – fluff originated at least as far back as the common ancestor of dinosaurs and pterosaurs in the earliest Triassic.

Another piece to add to the growing pile of evidence that feathers had a single origin in early avemetatarsalians! All we really need now is something like a prosauropod with feathers to seal the deal.

Now where’s our Triassic dinosaur Lagerstätte?