Wednesday, November 2, 2016

SVP2016 Presentation Highlights

I haven't been online for a while, so I'll keep this top part brief. I went to #SVP2016 in Salt Lake City, Utah, and was ecstatic to learn about all the great new research going on. There was tons of great stuff throughout the meeting and I met a lot of great people, but I've inevitably gotten a lot of information requests regarding new work being done at the meeting, and while the abstract is online for everyone to read, there's a lot of information from the presentations in particular that aren't in there. This is all the stuff I was able to sit in on and and write notes about. Keep in mind I purposely kept out presentation material if it was under embargo, or per request of the authors, as well as the fact that pretty much all of this is unpublished and should be taken with much skepticism until properly published. Nonetheless, I feel like this should be available somewhere for people to read if they want, so I'm putting it here and my DeviantArt page for reference. Remember though, none of this is final.
  • Derived microraptorines and Rahonavis can do launching flight from the ground, but they don't have much sustainability in the air.
  • Species of bohairornithid birds show owl and falcon-like foot proportions, suggesting they hunted prey in similar ways to those raptorial birds.
  • Some oviraptorosaurs (Elmisaurus in particular) have secretary bird-like foot proportions, leading to the possibility they might have hunted by kicking small animals to death in a similar fashion.
  • Calcium phosphate was found preserved in Psittacosaurus bristles, which suggests the structures were calcified in life.
  • Animals with large display structures also tend to show high amounts of variability in those structures. A study of ornithischians display structures found that they have similar variability in their structures, and up to three times more variability than the rest of the body.
  • Three new Stegoceras-grade pachycephalosaurids ("stegocerines") have been found which represent a southern radiation of pachycephalosaurs that were replaced in the Maastrichtian by pachycephalosaurines.
  • Hadrosaurs developed complex “wavy” tooth enamel to protect their teeth from fracturing, kind of like what horses have to protect themselves from problems like wave mouth.
  • Giant Mesozoic mammal footprints from the Catoca Diamond Mine in Africa that are ~107 million years old. Possibly represent Repenomamus-sized animal if not larger and was found alongside lots of dinosaur trackways. (This was only mentioned in-passing, but will hopefully be part of a study of trackways in the region.)
  • A study of tail weaponry in various terrestrial animal lineages shows that all animals that develop such tail weapons are large, armored, quadrupedal herbivores, and in all cases where tail clubs in particular evolve, they always evolve in stages where the tail stiffens first and gains the expanded club later on.
  • New lineage of cheloniod turtles from Angola which might represent K-T Extinction survivors.
  • New phylogenic work suggests protostegids may be outside the clade that contains living sea turtles, rather than the sister group of leatherbacks like some work has suggested. Even more bizarre is that some work has also suggested they might be completely outside of the clade that includes all modern turtles, which means they dramatically converged into a similar appearance, biology, and lifestyle independent of sea turtles.
  • There’s an unnamed new taxa of crocodylomorph with ossified uncinate processes along the ribs, something never before seen in a croc-line archosaur, and also makes it so that it has a bizarrely bird-like ribcage.
  • Study of the dorsotemporal fenestra (dtf) in early pseudosuchians & dinosaurs shows that it has a large role in blood transfer to the top of the skull in these groups. In theropods, the frontoparietal region (area right in-front of the dtf) is NOT a muscle attachment site as often claimed, as muscles would not funnel well into them & there's no muscle scar evidence. This brings up the question of what is going on in the expanded open area on the frontoparietal region in-front of the dtf. In birds, there are lots of blood of vessels in this region that help supply carunculate skin, display structures, and skull roof soft tissues that need the heavy blood flow. Crocodilians also use the area as a "thermal window" to cool the brain off in the heat of the day. They suggested that the dtf might function in similar ways, and the frontoparietal region was probably used by non-avian theropods and other early archosaurs for thermal components of shedding heat, and display components for providing blood to soft tissues on the face.
  • Taking the above a step further, some species of theropods like Allosaurus have vessel channels going from the frontoparietal region into display structures on the skull (in the case of Allosaurus, it's the hornlets), so this leads to the possibility that the blood was being provided to those areas through this region in order to engorge them in blood for display purposes, like what some birds do. This could be for color flushing, engorging waddles and other soft tissue structures on the face, providing blood flow for keratinous structures to grow, ect. Makes certain theropods seem a lot more colorful and flashy. Moreover, the expansion was also adapted in certain shield-headed croc lineages, suggesting the expanded shield in these crocodilians might have been visual display structures in life.
  • Over 223 specimens of Anchiornis are currently being examined for body outline preservation. The team working on them has already looked at 3 and already found some cool stuff, notably the extent of the foot muscles around the leg, color melanosomes in the eyes, a propatagium in the forelimb, a soft tissue fusion of digits 2 & 3, and evidence for the tail being decoupled from the legs, suggesting the caudofemoralis was less involved in locomotion for this taxa and possibly other paravians.
  • Studies of the aerobic levels of non-mammalian synapsids show that they group together with mammals in terms of activity levels to the point they’re indistinguishable from each other. This suggests that even pelycosaurs were already approaching mammal-like activity levels in the Carboniferous, and might suggest that increased activity levels are ancestral to amniotes.
  • Evidence for semi-aquatic behaviors in Cotylorhynchus, as well as a diaphragm-like structure in this taxa and other
  • More evidence for endothermy or at least increased aerobic behaviors being present in basal archosauriforms.
  • Models of giant ectothermic animals (giganotermic) show they would not be physiologically competitive and comparable with a true ectotherm in terms of aerobic abilities. This is evidence against gigantothermy in extinct animals.
  • Endothermy leads to the evolution of high blood pressures, which allows large land animals to pump blood up to the high parts of their body. Tall animals like sauropods and even animals with tall blood-filled spines like Dimetrodon could not develop such heights without high endotherm-like blood pressures, suggesting they had to be endotherms.
  • New late Triassic plesiosaur, making it one of the earliest known plesiosaurs. Despite being so early, it's actually fairly derived, and suggests that plesiosaurs both appeared and diversified even earlier in the Triassic.
  • Evidence for high metabolic rates and growth in all known plesiosaurs that have been tested. Some plesiosaurs reached 70% full body size in less than a year. However, nothosaurs and other basal sauropterygians have much slower growth rates and metabolic levels, suggesting plesiosaurs developed endothermy independent of other lineages.
  • Eocursor and some prosauropods from the Elliott formation in South Africa seem to be early Jurassic in age, not late Triassic as originally stated.
  • The Triassic-Jurassic extinction event seems to have benefited sauropodomorph diversity in the early Jurassic of South Africa. They jump up in diversity and species numbers after the extinction event.
  • Multiple new taxa of Maastrichtian-aged titanosaurs from Egypt, Tanzania, and Malawi.
  • Plesiosaur biomechanical models were created and showed that the most efficient way they could move their fins is together in tandem at the same time. Doing so increases efficiency by 30% and the hindflipper is able to catch the foreflipper’s turbulence it produces under the fin, pushing the animal faster. This might also explain why some plesiosaurs have larger hindflippers than foreflippers; it would help catch the turbulence and increase their speed even more.
  • New theory on the usage of plesiosaur necks: used the long neck as aquatic camouflage by producing less water pressure while moving, making them less likely to alert fish when hunting.
  • Study of the biochemistry of oviraptorosaur eggs in the nest show they were definitely produced by multiple females, proving the idea the nests are communal and likely guarded by a single male.
  • No evidence of sexual dimorphism in Coelophysis. Instead the specimens show huge amounts of variation of body size and morphs throughout the population. This seems to be the basal trait for Dinosauria, but was lost in more derived groups, including advanced tetanurans.
  • Chindesaurus comes out as a true theropod in the most recent analysis of its remains, and the sister taxon to Tawa, meaning it’s not evidence for a North American herrerasaurid. Chindesaurus and Tawa might possibly be part of a previously unknown northern clade of neotheropods.
  • Elaphrosaurus is part of the middle dinosaur member of the Tendaguru formation.
  • Elaphrosaurus and Limusaurus together form the subfamily elaphrosaurines, which are noasaurids (work published earlier this year). New info shows the humerus of “Elaphrosaurus sp.” from the Morrison formation might be part of this clade as well, but the lower leg bone also assigned to the taxa might actually be abeliosauroid in origin. There is also a Chinese elaphrosaurine that is the sister taxa to Elaphrosaurus which is currently being described and should be published soon.
  • Elaphrosaurus’ close relation to Limusaurus, as well as the shape of its neck vertebrae, heavily supports the existence of a small head, beak, and herbivory in this species and other known elaphrosaurines, meaning they represent another clade of herbivorous theropods.
  • Limusaurus specimens of a number of growth stages are now known, including hatchlings only a few inches long. This shows that hatchlings have short faces and small beaks as opposed to the adult’s rather long faces and pointy beaks. Babies also have MURDEROUSLY LONG KNIFE-LIKE TEETH in their mouth, while adults are toothless, and along with stable isotope composition, suggests juveniles were omnivorous while adults were herbivorous. Limusaurus is the only known dinosaur that loses all its teeth through ontogeny.
  • Forelimb reduction has happened at least six times alone in non-avian theropods. In every case it happens the same way; by reducing the size of the hand while lengthening out the humerus relative to the other limb bones.
  • Two new alvarezsaurs from the early Cretaceous period which show intermediate forelimb anatomy between suggested basal alvarezsauroids like Haplocheirus and advanced late Cretaceous forms.
  • The theropods with the best cursorial adaptations in the leg are tyrannosaurids, elaphrosaurine noasaurids, derived ornithomimids, and parvicursorinae alvarezsaurids. Derived troodontids and caenagnathids also come close to these taxa, but don’t have quite as many adaptations for running and efficient movement as the former groups.
  • Cursorial adaptations are not just for running. They can be used for other behaviors besides running, such as increased stride length, more efficient movement, and higher body reach.
  • Keeping the above in mind, tyrannosaurid top speed in predicted mathematical models is not very much different than other theropods of similar sizes, like allosauroids, despite the speed adaptions in their feet. However, stamina models of tyrannosaurids compared to allosauroids show that while they’re both moving at the same speed, tyrannosaurids are burning far fewer calories and moving much further distances than other theropods by using these adaptations. The results are that big tyrannosaurids have better endurance than any other large theropod.
  • Using the same speed models as above, the same study also showed that basal dromaeosaurids, like microraptorines, are much faster runners for their body size than more derived dromaeosaurids.
  • A study of the changes in skull shape of tyrannosaurids through ontogeny shows that tyrannosaurids that live in ecosystems shared by other large theropods of equivalent size show fewer differences through ontogeny compared to species that are the only top predator in their region. For example, Gorgosaurus and Daspletosaurus show low amounts of skull changes through ontogeny as they were sympatric species, while Tyrannosaurus, which was the sole giant theropod in the region, have very different juveniles which were exploring other niches in the ecosystem.
And that's pretty much it for the live presentations. I might do a second post on some of the stuff I did for fun as well as the posters some time in the future, but I think this is good sum-up of the general stuff for now.