Sunday, August 27, 2017

SVP 2017 - Day 4

And now for the final day at SVP 2017.

Morning Session

  • Baron: Baron's not convinced by his own current classification of Ornithoscelida: actually thinks ornithischians are within Neotheropods or possibly Averostrans. (The world’s gone mad!)
  • Baron: New data on Pisanosaurus has it as a silesaurid in their analyses: actually supports his idea that they're averostrans as that would mean we shouldn't find Triassic ornithischians at all as they would have to originate in the early Jurassic. (The same time we start finding the earliest averostrans.)
  • Baron: Ceratosaurs show close similarities to ornithischians, such as the form of the illium, the shape of the femoral head, and their vertebrae. Some ceratosaurs even have ossified tendons in their back vertebrae, a feature typically associated with ornithischians.
  • Baron: Chilesaurus comes up as a ornithischian in their phylogeny. They got criticism as they didn't include any derived tetanurans in their analysis, but the original Chilesaurus paper lacked any ornithischians for it to group with either. They're going to add more derived taxa in future phylogenies to better test this, as well as fix and increase their character list to see how things change.
  • Baron: If Baron's right, this would mean that any "theropod" that isn't an Averostran (Coelophysis, Dilophosaurus, Tawa, etc) aren't theropods, as the definition of theropod is anything closer to Passer/Allosaurus than Triceratops and Diplodocus, and they'd be from before the Allosaurus-Triceratops split. Instead they'd be proto-Ornithoscelidans.
  • Regalado Fern├índez: "Prosauropods" are still paraphyletic, but different nodes form independent monophyletic families that are pending descriptions/naming. Suggests numerous monophyletic groups of sauropodomorphs rather than a single lineage leading to sauropods.
  • Regalado Fern├índez: Phylogeny suggests that quadrupedality arose twice within sauropodomorphs: within the riojasauridae (which is getting expanded) and Anchisauria.
  • Holwerda: New updated phylogeny on basal sauropods has Patagosaurus is sister to Cetiosaurus, an interesting discovery as the mid-Jurassic Gondwanan desert was often thought to be a barrier to north-south dinosaur taxa.
  • Moore: New phylogeny shows mamenchisaurids are a natural group, but Omeisaurus comes up as the basal-most diplodocoid. Weird.
  • Waskow: Mother’s Day Quarry diplodocid specimens come from extremely small adult diplodocids. Seems to represent a population of Morrison diplodocids trapped on an island in the middle of the Sundance Sea, though this is debatable given that no large islands are known from the Sundance. Shows that diplodocids also underwent dwarfism like some macronarians.
  • Waskow: Long bone histology suggests that they reached skeletal and sexual maturity at the same time as other much larger diplodocids, but that they grew at a much slower rate.
  • Bansal: Sauropod ossified tendons in the neck were flexible enough to allow for movement, but stiff enough to support the weight of the neck. Future analyses of how these ossified tendons work structurally in the neck could give new insight to their biomechanics.
  • Button: Morphospace analyses of the lower jaws of herbivorous dinosaurs reveals repeated trends in dinosaur skull shape evolution, suggesting specializations in different gut-processing herbivorous taxa. However, while (traditional) saurischians had a large disparity in skull shape, ornithischians all tended to cluster in the same area of the diagram. This suggests that while non-chewing saurischian taxa needed to modify the shape of the jaw to feed on specific types of plants, ornithischians could feed on their wide range of food types via chewing without the need to modify their jaws.
  • Nabahvizadeh: Jaw muscles in palatal-feeding ornithischians connected from underneath the jugal to the lateral dentary ridge. This brings the jaw musculature attachment further forwards on the dentar, and is a trait seen in some modern palatal-feeding lizards and extinct dicynodonts. Also implies that many palatal-feeding ornithischians might have had stronger bite forces than expected.
  • Godefroit: Kulindadromeus is a thing. Analysis of filaments show numerous similarities with those of Sinosauropteryx. Support a homology with feathers.
  • Godefroit: Kulindadromeus is the oldest dinosaur with feathers: the quarry is Aalenian-Bathonian rather than Oxfordian. Earliest known feathers occur on an ornithischian.
  • Bell: Numerous small ornithischians from Lighting Ridge. One tooth represents a large Muttaburrasaurus-like taxon: tooth ridges are very similar to that taxa. Another large iguanodontian skeleton from Lightning Ridge represents one of the most complete iguanodontians from the continent. Might be same taxa as the tooth, but the front-half and jawline of the skull from the new specimen is missing, so impossible to tell..
  • Bell: Two more small-bodied taxa represented by limb bones and jaw fragments.
  • Bell: New dating analyses find Lightning Ridge to be late Cretaceous (Cenomanian, 96 mya).
  • Wilson: “Rubeosaurus” is a junior synonym of Styracosaurus ovatus. Holotype bones are misidentified.
  • Fowler: “Dannyceratops” (not official name, name of quarry) represents the earliest known of chasmosaurine taxon. Shows a lot of synapomorphies not seen in later taxa.
  • Fowler: “Judiceratops tigris” has a lot of issues in terms of supposed phylogenetic relationships and form of the frill. Should be re-analyzed as the frill fragments don't fit well together like other ceratopsians, so they might be misidentified.
  • Zheng: New basal ankylosaurine dinosaur with an elongate nodosaur-like snout and a large tail club from Eastern China. Shows a strange mix of both basal and derived features.
  • Arbour: Zuul! Zuul’s tail club osteoderms are asymmetrical. Ankylosaur tail club knobs are actually quite taxonomically distinct and have good characters for phylogenies. Might suggest sexual selection was heavily at play in ankylosaurs tail club evolution.
  • Arbour: Zuul has lots of skin and keratinous sheath preservation over the osteoderms. Skin is similar to other ankylosaurs: keratin sheaths are so well preserved you can see growth rings like you might see on a cow's horns.
  • Arbour: Zuul #2! Second Zuul specimen from a smaller individual found in collections. Despite being only slightly smaller, it has an unfused postorbital horn, something typically seen in very young ankylosaurs. Rest of the specimen might be at the Zuul quarry.
  • Brown: Borealopelta has really thick keratinous sheets over its bony armor. Keratin reaches out way past the bony cores. Suggests we might be severely underestimating the size of nodosaur spikes (and keep reading).
  • Brown: Longest disparity of bony osteoderms size vs keratin length and width takes place on the cervicals. The keratin-to-osteoderm ratio is strictly allometric, the longer the induvidual bony spines of the osteoderms, the longer in proportion the keratinous sheet that covers it. Rough length of the keratinous sheets in Borealopelta can be determined via an equation. (Maybe could also be used for other ankylosaurs?)
  • Brown: There's one exception to the above rule: the parascapular spine is much, much larger than determined by the equation. The keratinous sheet is many degrees larger than those on any of the other osteoderms, and a cross-section through the spine shows the largest bony osteoderm on Borealopelta as a tiny little circle within the thick keratinous covering.
  • Brown: The allometric levels in the osteoderm-keratin length is consistent with a sociosexual display features (like horns and antlers) rather than defensive features like anti-predator spines. Supports the idea that nodosaur spines were involved in (and perhaps the evolution of which was primarily driven by) sexual selection.

Poster Session

  • Brougham: Two new theropods from Lightning Ridge. One is vertebral and pelvic material from a large carcharodontosaurian taxa, the other is vertebrae from a small-bodied ceolurosaurian taxa. Neither groups show synapomorphies shared with megaraptorans, suggesting a larger diversity of theropod groups were present in the late Cretaceous of Australia.
  • Lockley: Trackways from the Kayenta Sandtone near Moab, Utah show strict differentiation between ichnotaxa. One site area is associated with an exclusively Eubrontes-Kayentapus fauna representing exclusively large theropods. Site nearby but in the same layer shows Anomoepus-Otozoum ichnofauna representative of exclusively herbivorous dinosaur taxa. Suggests differences in habitat preferences between herbivorous and carnivorous dinosaur groups at these locations.
  • Simon: New species of small-bodied Fumicollis-like hesperornithine from the Hell Creek formation. It's from the Bone Butte region (same location as the Dakotaraptor holotype).

Afternoon Session

  • Berrett: Reanalysis of the Vulcanodon Quarry suggests the site is actually Hettagian or Sinemurian in age, making it much older than originally thought.
  • Berrett: First phytosaur from Gondwana found in some older Triassic sites nearby. These new sites are filled with wood and has giant lungfish teeth the size of a human hand. Seems like a densely wooded environment similar to the petrified forest in the Chinle.
  • Berrett: Interestingly, the new site preserves no evidence of sauropodomorph dinosaurs, despite being known from drier layers below and above it. This as well as the near-absence of early sauropodomorphs from Triassic sites representing well-watered forests might signify that they specifically avoided these kinds of habitats.
  • Smith: New material from the holotype specimen of Cryolophosaurus, as well as a second specimen that’s quite a bit larger. Sadly the larger specimen is very fragmentary.
  • Smith: Braincase allows for a good reconstruction of the neural anatomy. Dorsal vertebrae have little “bow tie” formations on the neural spines: very cute.
  • Smith: New phylogeny suggests Cryolophosaurus is the sister taxa to Dilophosaurus in (interestingly) a monophyletic coelophysoidea.
  • Fabbri: All the bones in the Ibrahim "neotype" specimen of Spinosaurus are incredibly dense. Also, all are of the same ontogenetic age: subadult 17 years old. Is against the idea of this specimen being a chimera.
  • Fabbri: Ibrahim's Spinosaurus has incredibly dense bones, and the density levels of Spinosaurus bones clusters strongly with semi-aquatic birds and alligators, not with terrestrial birds and other theropods.
  • Fabbri: Suchomimus shows up on the graph as having very dense bone, intermediate between “normal” theropods and subadult crocodilians. Still had an open medullary cavity, but the bone is densening. Suggests spinosaurids other than Spinosaurus might have already been experimenting with aquatic behaviors.
  • Fabbri: Juvenile animals have less dense bones than adult ones. A juvenile specimen of Suchomimus clusters with birds, theropods, and baby crocodilians while the adult/subadult Suchomimus clusters in its intermediate spot. Similarly, while the subadult specimen of Ibrahim’s Spinosaurus groups with subadult alligators, larger isolated neural spines from elsewhere in Africa are even denser and cluster further into the center of aquatic taxa.
  • Fabbri: Peramorphosis is involved in the evolution of spinosaurid skulls: shows numerous similarities in the changes to the skull bones to the evolution of bird beaks.
  • Samathi: Two new species of megaraptorans. Taxon A is shorter than a man and only known from a tibia. Taxon B is known from limb elements and vertebrae from both an adult and juvenile individual. Adult is about human-height, juvenile the height of coyote. When plugged into a number of existing phylogenies these new taxa come up as close relatives of Australovenator no matter which is used. The phylogenies also find Datanglong to be a megaraptoran and Siamotyrannus to nest within early coelurosaurs.
  • Bykowski: Homogenous global data set suggests that carnivorous dinosaurs were not responding to changes in prey body size. Instead, taxonomic turnover is driving morphological changes in different groups.
  • Fiorillo: Alaskan dinosaur trackways from along a forested shoreline. Lots of hadrosaur tracks, a few ankylosaur tracks, some theropod tracks, and a crane-sized avian track all from the same locality. No ceratopsids, despite being very common from fossil sites on the north slope.
  • Tanaka: We know that polar dinosaurs (like hadrosaurs) would often would breed in the high arctic given the presence of eggshells. In order to incubate their eggs, they probably utilized rotting vegitation in nest mounds.
  • Tanaka: Hadrosaurs and sauropods of the  megaloolithidae egg family preferred mound nests. Sauropods of the faveloolithidae egg family preferred buried or geothermal nests.

And now, SVP 2017 has come to an end. Really sad that I had to leave and return to the hectic life that is undergrad. Nonetheless, I'm happy I was able to meet back up with my friends from last year's meeting, as well as make a bunch of new ones, and I can't wait for the opportunity to go again next year. (Assuming money won't be a problem.)

Until next time, thanks for another great event everyone! Keep Vertebrate Paleontology cool! Go SVP!

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