Thursday, August 24, 2017

SVP 2017 - Day 2

And day two begins! Same as before: wrote down everything I could in blurbs based on section, left out embargo stuff, and if you have any questions feel free to ask. Let us commence!

Morning Session

  • Dunne: New biodiversity analysis of early tetrapods suggests that species richness and alpha diversity increased dramatically across the Late Carboniferous-Early Permian Boundary.
  • Dunne: Contrary to earlier studies which suggested that the fragmentation of Carboniferous rainforests during the Permian led to increased endemism in tetrapods, this analysis found that many species and families became more cosmopolitan as the rainforest fragmented.
  • Mann: New “specimen” of a microsaur from Mason Creek from a period of time with low microsaur diversity. It is the smallest microsaur known: only about a cm in body length. (I say “specimen” in quotes because they don't actually have the fossils of this animal: they only have latex casts of it from when it was first collected. The actual specimen is lost and probably being held by a private collector.)
  • Mann: Phylogenetic analysis suggests it to be a sister taxon of the Carrola +Batropetes clade in the family brachystelechidae.
  • Mann: Brachystelechids like this new taxon show wide-set rib morphologies and well-ossified forelimb bones, which is consistent with a terrestrial and possibly fossorial lifestyle (though see below), not an aquatic one. Their short, compact bodied suggest that they had a different overall lifestyle than other microsaurs.
  • Mann: Some brachystelechid features, such as a wide-set gut, foreshortened and ossified skull, and multi-cusp dentition (which resembles marine iguanas) resemble traits in herbivorous taxa. Might suggest they were herbivorous algae or moss-feeders.
  • Gee: New specimens of Llistrofus skulls, one 3D upper jaw and mandible, the other a crushed full skull with scale preservation.
  • Gee: The skull has an enlarged mandible and is much more robust than other related taxa, but teeth are otherwise typical for the group. This is not consistent with a tougher durophagous diet,a dn the authors suggest this enlargement of the skull bones is consistent with a streamlining of the skull and musculature for a head-digging fossorial lifestyle.
  • Jansen: Batropetes has been suggested to be fossorial (see above), but it possesses a narrow (not shovel-like hand), large forward-facing orbits, and other features not consistent with fossorial behavior in modern tetrapods and other thought to be burrowing microsaurs. Instead this anatomy might be more consistent with a leaf litter foraging lifestyle.
  • Jansen: The earliest known frogs like T. massinoti might have had a more leaf litter foraging lifestyle rather than a frog-like lifestyle based on comparison with modern salamanders and other microsaurs known to be foragers. Further analyses of limb proportions and morphologies could shed light on early amphibian and temnospondyl ecology.
  • Bishop: Orientation of cancellous bone architecture lines in animal femurs is an accurate way to determine leg posture in extinct animals. Lines always grow perpendicular to the ground, so the leg's neutral state is determinable by looking at their orientation.
  • Bishop: Daspletosaurus has a femur perpendicular to the ground, troodontids had a slightly angled leg to the ground, and modern birds tested positive for having a perpendicular leg to the ground, all of which are consistent with biomechanical studies.
  • Bishop: Further analyses of cancellous bone could be used to learn the neutral leg postures of other extinct animals, like therizinosaurs and ceratopsians.
  • Martin: Not all pterosaurs have thin-walled bones: many pterosaurs have thick-walled bones like non-avian theropods. Thickness of the wing bones has no phylogenetic consistency either to the family level or even to pterosaurs as a group. However,
  • Martin: Smaller pterosaurs tend to have a lower R/t (radius to thickness ratio) which is consistent with them having resistance to frequent landings and takeoffs like small-bodied flying taxa. Larger pterosaurs have very high R/t levels which is consistent with long periods in the air, which is consistent with large flying taxa.
  • Martin: The one outlier in this study was Hatzegopteryx, which has the thickest bones of any known pterosaur. This is consistent with the idea that it was spending long periods on the ground as a terrestrial macropredator. More bones from other giant pterosaurs should show if Hatzegopteryx is unique or if these thick bones is consistent across all taxa.
  • Larson: Varanus lizard tooth morphology is very similar in variation to what’s seen in ceolurosaurs dinosaurs, and can be used to figure out the dietary preferences of theropods.
  • Larson: This study also found 4 significant shifts in Vranus lizard diets throughout their recent evolutionary history to terrestrial vertebrates.
  • Larson: Yanornis possesses an insectivorous/aquatic tooth morphology (consistent with gut content), while Guanlong groups with Varanus taxa that hunt large vertebrates.
  • Larson: Microraptor groups consistently with piscivorous aquatic-feeding taxa, which is consistent with the fish found in its gut. Other dromaeosaurids group with predators of large terrestrial vertebrates, as does Sinosauropteryx and Incisovosaurus. The latter might be due to a lack of herbivorous taxa in the dataset, but the tooth morphology of Sinosauropteryx might suggest it tackled larger prey than might be expected.
  • Simoes: Some “early lepidosaurimorphs” actually fall as the early members of other classes, while other “early lepidosauromorph” taxa are true lepidosauromorphs..
  • Carrillo: Notoungulats are nested within laurasiatheres (stuff later this week contradicts this).
  • MacDougall: Tetrapod diversity of the Richard Spur quarry in Oklahoma shows a high small animal diversity/low large animal diversity ratio seen in modern ecosystems, and is distinct from other early Permian preservationists environments. Captorhinus is the most common taxa in this terrestrial environment.
  • Jung: The genus Captorhinikos is paraphyletic. All three species are related to completely different taxa. Only the holotype species C. valensis is Captorhinikos, “C. parvus” is sister to Saurorictus, and “C. chozaensis” is many nodes more basal than C. valensis.

Poster Session

  • Super: Baby Xiphactinus specimen! One of only two juvenile specimens of this species ever found. The rarity and isolated locations of the two Xiphactinus juveniles suggests like modern large predatory bony fish, juveniles were solitary and lived in warm waters close shore while adults switched to a schooling lifestyle when they matured and moved out into the open ocean.
  • Gage: Analyses of the forelimb humeri in theropods using morphometric data suggests that forelimb robustness scales with preferred prey size, not absolute size, in theropods. Taxa with very robust humeri like megaraptorans probably preferred hunting animals larger than themselves when compared to taxa with shorter forelimbs. Taxa with primarily head-based predation of course are exceptions/outliers.
  • Takasaki: Preliminary analyses of gastroliths in modern birds has shown that gastrolith shape correlates well with diet, with rounded gastroliths being consistent with herbivorous taxa and angular gastroliths being consistent with carnivorous taxa. When applied to Deinocheirus, despite the presence of fish bones in the gut, the gastrolith shape is consistent with a primarily herbivorous diet, suggesting Deinocheirus was primarily herbivorous with fish representing only a minority of its diet.
  • Trapman: Stable isotope analysis of four Spinosaurus teeth and four Carcharodontosaurus teeth was used to check earlier studies using oxygen isotopes of spinosaurid teeth to determine aquatic behavior. The study was able to successfully repeat the results of the first study with all eight teeth, further supporting spinosaurid aquatic foraging.
  • Rooney: Postcranial morphology can be used as a reliable indicator of semiaquatic vs terrestrial behavior in crocodylomorphs and lepidosaurs, even between closely related taxa. Reliable indicators of lifestyle include the length of the upper limb bones compared to the lower ones as well as the height of the caudal vertebrae. When extinct crocodylomorphs are added they fit in snugly with predicted morphospecies, which is good and could be used as a method to determine terrestrial vs aquatic behaviors in the group.
  • Rooney: One surprise was that when Hesperosuchus was placed into the morphology it popped up within the semi-aquatic group, but right on the edge of the terrestrial group. Might suggest hesperosuchids might have already been experimenting with a semi-aquatic lifestyle.
  • Lawver: New species of turtle from the Judith River Formation. Size of the scapula suggests an animal with a half-meter shell. Shape of the carapace is weird: dorsal side of the shell is similar to terrestrial taxa while the central side is similar to aquatic taxa. Overall, this taxa is a new and bizarre addition to the rich turtle fauna of the region.
  • Jasinski: New species of dromaeosaurid from the end of the Maastrichtian of New Mexico. Specimen preserves quill knobs on the forelimb consistent with secondary feathers. Phylogeny finds the taxa to be less derived than Deinonychus, suggesting a second lineage of dromaeosaurine theropods in the Maastrichtian of North America outside of Dakotaraptor.
  • ?????: CT scans of the internal structure of Bistahieversor’s endocast shows that it had a large sinuses and an endocast cavity convergent in morphology with Tyrannosaurus rex. It also has a large airsacs and an overall skull build much more similar to derived tyrannosaurines than basal members of the group.
Afternoon Session

  • Sullivan: Jehelornis specimens have an odd bone present near the sternum which is oar-shaped and has a large round fenestra in its center. This bone is often identified to be lateral trabecula, which is bizarre because even more derived birds lack this trait until close to the enanthiornithine-neornothine split (though Linheraptor seems to possess a lateral trabecula-like structure as well).
  • Sullivan: This odd bone's “lateral trabecula” identity doesn't seem to be accurate, and new specimens show that it is actually part of the 3rd and 4th sternal ribs.
  • Sullivan: No living animal has a sternal rib morphology like this, but it is very similar to enlarged bony structures seen on the ribs of some pterosaurs. In pterosaurs it's been suggested that these traits evolved help with respiratory musculature, and if this is used for the same reason, would suggest that Jehelornis had an interesting way of breathing.
  • Rashid: Studies of caudal vertebrae fusion in chickens and mice of has suggested that vertebral fusion of the pygosytle is tied to a genetic mutation that also results in the loss of caudal nerves. This doesn't seem to be correct however as many bird groups, like paleognaths and Confuciuornis, have fused tail vertebrae but still possess caudal nerves.
  • Rashid: Pygostyles do not fuse until well into ontogeny in living birds. Suggests that some juvenile bird specimens named as new species due to the lack of a pygostyle are likely to just be juveniles of known taxa.
  • Rashid: Dinosaur tail in amber, being made up of unfused vertebrae, might not be non-avian with the information showing that bird pygostyles do not fuse until late in ontogeny.
  • Wang: New enanthiornithine bird with preserved feathers. The specimen is odd in that it possesses a plough-shaped, modern bird-like pygostyle, but lacks a tail fan, suggesting that the tail fan is not exclusively linked to modern-type pygostyles.
  • Wang: Has really weird feathers on the legs. Seem to be single sheets of keratin that are sausage-shaped, but have splayed tips. Melanosome evidence also suggest they were brightly colored.
  • McNamara: Kulindadromeus has melanosome preservation! (Color study!?)
  • Serrano: Mechanical and aerodynamic features of Protopteryx suggest it was a fast flap-glider. Given it is one of the basalmost enanthornithines, this might have been the ancestral flight state for the group.
  • O'Connor: Jehelornis seems to lack a crop and based on the lack of seeds in the neck region of any known specimen. Interestingly, many specimens of Jehelornis have seeds and gastroliths in the stomach, but none have both. Could imply a shift in diet over the course of a year, through ontogeny, or another unknown reason.
  • O'Connor: Confuciusornis does not seem to be a piscivore. The specimen with fish remains in its neck region seems to have been from an association. (Jehol Biota is full of fish, not surprising bits and pieces of them appear close to other fossil taxa.)
  • O'Connor: Sapeornis possesses a true crop and gizzard based on seed remains in both the neck and stomach region.
  • O'Connor: Enanthiornithines are very problematic in their diets, as inferred pellets from this group that contain fish seem to actually be coprolites from fish or aquatic reptiles.
  • O'Connor: “Seeds” in enanthiorithine guts are also highly problematic. They always appear on the left side of the body, where follicles and eggs should be, not the stomach, and overall resemble bird follicles in shape and morphology rather than seeds. (On the bright side, we can now tell if some enanthiornithine specimens are females!)
  • O'Connor: Half of all known specimens of Yanornis possess fish bones in the digestive tract, making the piscivorous lifestyle of this bird very certain. (Also leads to some doubt about Confuciusornis being a specialist piscivore based on just one specimen with a fish bone near its neck.)
  • O'Connor: One specimen of Yanornis has rocks blocking the intestine, which is an intestinal issue found 1% of all modern shorebirds. Not evidence for gastroliths.
  • O'Connor: Tooth morphological studies might be a better way to determine diet in early birds than stomach contents, as many groups actually have quite specialized and oddly shaped teeth. Even Archeopteryx which is often described as having “peg-like” simple teeth actually are quite weird when looked at from a morphological standpoint.
  • Field: New model proposes that the destruction of forest ecosystems during the K-T extinction is a large factor involved in the extinction of primarily arboreal enanthiornithines and the survival of ancestrally terrestrial neornithines.
  • Field: When forest ecosystems collapsed, enanthiornithines died out due to the loss of habitat, but primarily terrestrial neornithines were able to survive. Then when forest ecosystems recovered, niches opened up for higher landbirds to invade into arboreal niches, leading to the rapid evolution of literally hundreds of unrelated arboreal bird clades.
  • Felice: Bird clades with novel phenotypes, such as unique palatal morphology, head crests, and oddly-shaped beams have faster rates of evolution than bird clades without them. This is consistent with research on other animal groups, like mammals and non-avian dinosaurs.
  • Felice: Ancestral state reconstruction taking data from all bird group’s skull morphologies shows that the ancestral neornithine had a skull most similar to the passerine bird Vanga curvirostris, the hook-billed vanga. Postcranial morphology of this hypothetical neornithine ancestor would need to be determined with postcranial ancestral state analyses.

And now I leave you with a picture of the skull of the world-famous baby Chasmosaurus belli. Cheers!

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