Monday, April 24, 2017

Paleofest Report 2017

It’s time for my annual report of Paleofest in the Burpee Museum in Rockford. Last year I skipped the report considering the high amount of unreleased data as part of it, which is a shame since it was quite good. This year there are fewer spoilers, but I did wait a month after the event. For more on Paleofest itself, please check out my first report here:

The first talk on Saturday was from Thomas Clements from the University of Leicester. While McCoy et al’s proposal of Tullimonstrum’s vertebrate affiliations and Sallan et al’s counterargument are given a great deal of press, Clement and his team found an alternate line of evidence for Tullimonstrum as a vertebrate. The Tully Monster, as a marine taxa exclusively but well-sampled from the Mazon Creek formation, has been a mystery for 70 years, having been placed as a conodont, arthropod, mollusk, annelid, and nematode. 
What Clements et al did was use powerful electronic scans and microscopes to compare it to other well-preserved animals. Turns out melanosomes, organelles determining the pigment of a cell, are preserved, and are especially concentrated in the eyes of fossilized organisms. The first step was identifying the eyes of Tullimonstrum: the two long stalks coming perpendicularly from the animal are tipped with melanosome clusters, suggesting that they were the eyes of the animal. Finally, the melanosomes themselves were studied, revealing a mix of both shapes of organelle, a condition only found in vertebrates. While the lack of similar animals in the fossil record makes the classification uncertain, Clements’ study makes a convincing case for the animals being stem vertebrates or basal chordates instead of any invertebrate group.

The second talk was by Julia McHugh of the University of Western Colorado. Her study was on the anomalous survivors of the Permian-Triassic mass extinction, particularly on the large temnospondyls that were successful enough to survive to the middle of the Cretaceous period. The Permian extinction was made up 2 land dieoffs and 3 oceanic dieoffs over the period of a million years, killing off over 90% of species. At first it seems as if the big predatory amphibians and herbivorous dicynodonts came off without an impact, but McHugh discovered gaps and ghost lineages in the larger groups. 

Apparently two groups of temnospondyls, the Euskelids and Stereospondylids were extremely successful and diverse just before the extinction, and coasted on their inertia. Paleohistology revealed there was more variation in terms of growth cycles so that the animals could keep growing during dry seasons. The variation in growth rate and cycles increased over the Triassic. McHugh did not get to study therocephalians and dicynodonts to see if they had similar adaptations or if they were doing different survival strategies, but it’s interesting how it’s select few groups of terrestrial macrofaunal that did very well in the apocalyptic event. Likewise, there was no explanation why these adaptations failed them during the Triassic-Jurassic extinction, but hopefully these other questions will be answered by followup studies. It’s a fascinating answer that leads to further questions. 

The next talk was by Susan Drymala of the University of North Carolina on Triassic megapredators. These animals belong to the paracrocodylomorph clade along with true crocodilians and other archosaurs. One of these is the group called the Rauisuchians, containing the likes of Saurosuchus, Ticinosuchus, Postosuchus and Teratosaurus. The group she studied fit between the Rauisuchids and true crocodiles, containing the fish-eating Qianosuchus, herbivorous Phyllodontosaurus and Effigia, and the macropredators Carnufex and Renondavenator. Evidence of their predation on phytosaurus, dinosaurs, dicynodonts, aetosaurs, and other paracrocodylomorphs shows they were the top predators in their habitats. 

In addition to archosaur traits of unidirectional airflow and fast growth in warm climates, the rauisuchians and other paracrocodylomorphs had upright stances due to their hips that curved around the femurs without changing the shape of their femoral heads like dinosaurs. It’s also possible that they were bipeds; the animals Poposaurus and Postosuchus, due to their tiny forelimbs and powerful hindlimbs, have been reconstructed in some studies as bipedal runners.  It’s fascinating to see that other archosaurs beat dinosaurs to their niches early, and this is a good companion to 2015’s Paleofest on the Triassic. 

  A more problematic talk was by Joseph Peterson of the University of Wisconsin, who runs the Cleveland Lloyd Dinosaur quarry. It’s a poorly mapped formation of limestone-covered mudstone containing hundreds of dinosaurs. While Camarosaurus and Camptosaurus are the most common of the herbivores, the vast majority of fossils belong to subadult Allosaurus. It’s paradoxical how many more Allosaurus there are than other fauna. There are barite and calcite modules showing a dry habitat, but there is no abrasion from wind or water erosion. The bones are jumbled and disassociated, but individually in great shape. 

Two theories have been proposed to explain the quarry, but Peterson argues against both of them. The quarry has disarticulations like a drought assemblage, but there is no distortion from exposure or splintering from desiccation. There’s no hydraulic influence and predators are extremely abundant like a predator trap, but there is no articulation or traces of feeding on the bones. A chemical study revealed sulfies and pyrite in the site, with abundant charophyte algae but no freshwater plants. Geochemistry shows heavy metals present, but they could just as easily be from the decaying corpses than the cause of the death.  Peterson suggests the site was an ephemeral pond with multiple depositions, but the characteristics still don’t fit. Why so many animals? Why no marks of scavenging or desiccation? Why so many juvenile predators? To make matters worse, Peterson does not support his proposal with modern examples. The Cleveland Lloyd quarry is an enigma, and this study raises more questions than it answers.

The next talk is a bit better-there is no attempt to try to untangle the mess here. Karen Poole talks iguanodonts, and ornithopods in general. The classification is confusing and the cladistics here is very complex.  The most basal of these bipedal beaked herbivores were the Hypsilophodonts, a probably parphyletic group of small basal ornithopods from the early Cretaceous of the entire globe. A more derived group were the Thesecelosaurs from early Cretaceous Asia and late Cretaceous North America.  The next derived group were the Rhabdodonts, a surprisingly successful group that started in Europe and made it to North America and Australia for brief bits but survived in the European islands until the mass extinction. 

It’s difficult to tell if the Camptosaurs and Dryosaurs are more or less derived; the Camptosaurs seem to have started in the Middle Jurassic European islands and continued into the middle Cretaceous in North America. There seems to be a new clade of long-armed, robust boned, huge-spiked ankylopollexians; this unnamed clade contains Barilium and Hypselospinus from West Europe, Bolong and Jinszhousaurus from China, and Lurdosaurus from North Africa. Just outside the Iguanodontines is Lurdusaurus’ compatriot Ouranosaurus and the American Hippodraco. It seems that these families of ornithopods freely intermingled, species popping in and out replacing each other. Iguanodontinae itself, defined by high-crowned teeth that are especially narrow in the maxillia, contains Iguanodon itself with later species such as the Chinese counterpart Equijubus, the Japanese Fukuisaurus, and the Spanish Proa.  More derived species contain Mantellisaurus, Probactosaurus, Althirhinus, and Eolambia. The Bactrosaurs, including the European Telmatosaurus and Tethyhadros (the Europeans outlived the rest of the family) seem to be transition between the Iguanodonts and the spikeless, toothier hadrosaurs. 

Following land vertebrates comes marine invertebrates, albeit from the same period of time. In this case, Rex Hanger of the University of Wisconsin in Whitewater discussed reefs of the Niobara found in Texas. Said reefs were made by rudists, giant bivalves, instead of corals. The tropical fauna also included Echinoids, sharks, the fish Gyrodus, Snails, cephalopods, and oysters, all extremely well-preserved, abundant, and diagnostic. The index fossil is the ammoniate Oxytheropidopteryx. The silified preservation shows unique environmental conditions; the Karamichi member is a low-oxygen habitat that preserves micromorphs of the known species encased in pyrites. A fascinating place, despite it being invertebrate based

The next talk was far more conventional, with Eric Snively of the University of Wisconsin-La Crosse talking about Tyrannosaurus biomechanics. The specifics are still under wraps, but his conclusion is that Tyrannosaurs owe their amazing success due to their ability to exploit multiple niches over their lifetime while remaining the fastest and more agile dinosaurs of their size. 

Eugenia Gold of Stony Brook University gave a travelogue instead of an academic talk, but it was still educational. For all expeditions, I learned, I must remember to back a mechanic, a lighter, food, water, hammer, spare tires, and, in case Mark Norell is part of it, Gnocchi. You can see her website and twitter for more on her experiences.

The last talk of the day was the most entertaining, by Dr. Thomas Holtz of the University of Maryland. His topic was on dinosaur cursoriality; the adaptations required for extreme speed. In terms of speed, we’re pretty pathetic-scoring 10.45 meters per second with our best athletes-dogs, ostrich, horses, and pronghorn can hit more than 20 meters per second. An example of a cursorial adaptation is limb shape: the longer the fibula, tibia, and metacarpals and metatarsals are, the faster the animal can move. There’s also a big of differences in what aspect a cursorial adaptation is for: speed, acceleration, or home range.

Theropod dinosaurs, particularly coelurosaurs, have pinched-in feet where some of the metacarpals and tarsals are fused together for a single, strong structure: the acrometatarsus. In Holtz’s study, groups with cursorial adaptations include the odd gracile Elaphrosaurs from Jurassic Gondwana, the surpsingly nimble tyrannosaurs, the super-cursorial ornithomimids and alvarezsaurids, and to a lesser extent oviraptors and troodonts. There’s a trend of increased cursoriality as the Cretaceous goes on, with Troodon, Ornithomimus, and Tyrannosaurus being quite well adapted for running.  Therizinosaurs are the exception among coleurosaurs, being probably unable to run. It seems that most dinosaurs were growing faster and faster through the Cretaceous, even among more primitive groups such as the Abelisaurid ceratosaurs and the Megaraptoran carnosaurs.

Sunday’s talks began by not a scientific study, but Sarah Boessenecker’s accounts of her curatorial duties at Charleston College’s Museum. There’s a large amount of great specimens, but it’s heavily reliant on local volunteers and fundraisers. There’s not much else to say about this one, except that I strongly encourage everyone reading this to visit and support their local museums.

An environmental study of a fossil bed was next. Marie Lorente of Reservoir Labs examined a bed in the famous Hell Creek formation. This place was called the Ninja Turtle quarry as the first fossils were four turtles. Palynological studies revealed a great deal of pollen and spores, while the fossils are mostly freshwater turtles. That is, for the first place. The underlying layer has very few pollen, no turtles, and is almost entirely saltwater dinoflagellates. This dramatic turnover may be the result of a tsunami. The ideas of a warming event or volcanic event don’t fit into the date of the find; the late Cretaceous was cooling and the turnover happened in-between volcanic events. Likewise, the K-T comet was not responsible as this happened a million years before that. This narrows it down to a tsunami or similar oceanic flooding as seismic events pushed saltwater out of the ever-narrowing interior seaway.

One of my favorite talks was by Victoria Arbour of the Royal Ontario Museum. She noticed that for most tetrapods, weapons are mounted on the head, and very few on the tail. She decided to make a study of fossil groups with tail clubs and similar weapons. Today, tail weapons are the spiny tails of porcupines, sharp-scaled Pangolin tails, lizards with spiked whips or clubs as their tails, and muscular, armored tails of crocodiles.  The fossil groups examined are the glyptodont armadillos, meilonid turtles, and herbivorous dinosaurs.  Stegosaurs, for example, have very strong flexible tail, with the spikes (or thagomizer) being set into the skin of the animal. In contrast, Ankylosaurs have fused tail veretebrae. The clubtailed sauropods only have the last few tail vertebrae fused. Glyptodonts have unfused bones but their osteoderms are fused into interlocking rings and tubes with the muscle underlying them. Meilonia has a straightforward flail, with no fusion in the entire tail. Club durability has been mechanically tested-clubs of both ankylosaurs and glyptodonts were sturdy enough to crunch into bones. 

The main topic studied was how did the club evolve-handle first? Knob first? Or in tandem? Earlier ankylosaurs help flesh out the story: Gobisaurus had no tail club, but had fused tail vertebrae. Liaoningosaurus, an odd fish-eating ankylosaur, had long spinous processes. Dyoplosaurus, predecessor to Scolosaurus and Euoplocephalus, possessed a small club compared to its successors.  Glyptodons seem to have had the same situation, culiminating in the Pleistocene Doedicurus and Eleutherocercus with their mace tails.  There seems to be a correlation in evolutionary adaptations that produce tail maces:  body armor, head spikes, weight over 500 kg, quadrupeds, herbivores, stiff thoraxes, and wide pelvises.  The selection pressure for such weapons could be from Tyrannosaurs or for fights for mates  A study of tyrannosaur bones and ankylosaur armor needs to be done to identify if there are any fractures from tail impacts. On her request, I will use the hashtag #ankylosaurfightclub to identify depictions of ankylosaurs fighting anything.

An exciting talk was by the Field Museum’s dinosaur paleontologist, Peter Mackovicky. Mackovicky, when he is not excavating the upper Cedar Mountain Formation or joining the rest of Tyrannosaur paleontologists in the Late Cretaceous, has spent many summers in Antarctica.  As early as the ill-fated Scott expedition and its plant fossils, paleontologists have found tantalizing glimpses of a tropical continent far from the icy wasteland of the past era. McMurdo Station, as well as anchoring zoological, meteorological, and climatological expeditions and studies, also acts as a base for paleontology. The central mountains, particularly Mt. Kirkpatrick, have rocks of the Triassic and Jurassic eras, complete with anmal fossils. The early Triassic layer contains Lystrosaurus and other animals similar to South Africa’s Karoo formation, showing the passage of Gondwanan fauna even after the breakup of Pangea. This is followed by a late Triassic fauna, again similar to South Africa’s lower Elliott formation’s; the cynodont Thrinaxodon is known from South Africa while the huge temnospondyl predators Kryostega and Antarctosuchus are unique. It is the Hanson formation, first discovered by David Elliot on the peaks of Mt. Kirkpatrick, that contains Jurassic dinosaurs
The Field Museum has been joined by the University of Wisconsin, the University of Alberta, Augusta College, and their guide Peter Braddock on their expeditions; they have uncovered the large predatory dinosaur Crylophosaurus and the sauropodomorph Glacialosaurus in the past. New finds complete Crylophosaurus’ anatomy with another individual, more Glacialosaurus, and add more fascinating animals: other sauropodomorphs “Jolly Roger” and an isolated Sacrum (both of which, like Glacialosaurus, have counterparts in the upper Elliot), a molar of a tritylodont (a small herbivorous cynodont), and the humerus of a basal pterosaur. I’m very excited to learn more about these animals, and especially about next year’s temporary exhibit at the Field Museum showcasing Mackovicky’s finds. 

Katie Tremaine followed this with a followup on previous studies. Last year featured no fewer than two talks on the same subject. You see, some Tyrannosaur specimens have been found with medullary bone, tissue buildup within the long bones (femurs and humeri). In modern birds, the buildup is only found in female birds that ovulate. This so far is the only way to sex a dinosaur; sexual dimorphism seems not to be significant among most dinosaur species at least in terms of bone size and structure. The calcium within the bone is produced to be used for the forming of eggshells, so only a dinosaur that is going to lay is going to have this buildup. This is the main flaw with this method: Jane and Sue, for example, could be either sex, as they could either be males or females that are not about to lay. What Tremaine accomplished is chemically staining the calcium, taking the bones into X-ray, and making sure that the bone buildup cannot be from a different physical state or reason. So far, only Petey, a teenager, has been found to be a female. 

The next talk was farcical: talking mostly about the ridiculous “Toroceratops” model in which all Torosaurus are identified as mature Triceratops. It is a pet theory of Horner and Scanella at the Museum of the Rockies, but their lumping agenda will be discussed elsewhere. Suffice to say, their methodology is flawed, their logic is convoluted, their evidence weak, and their bias obvious.
Thankfully, the next talk was by David Grossnickle, of the University of Chicago. What he did was a clever study on studying mammalian diversity in all permutations during the Mesozoic into the extinction. Morphometric parameters of mammalian teeth (which are not only significant given mammal tooth evolution, but inherently easier to find than body fossils) were plotted on various scales. While glimpses of mammalian diversity are shown by the rare full body fossil, such as the badgerlike Gobiconodont Repenomamus, one must take subtler approaches to determine diversity using all known data.

There seems to have been a fair amount of therian radiation in the late Cretaceous based on tooth geometry. While there is an increase after the K-Pg extinction, it seems to have begun during the age of dinosaurs. Size, species, and diet diversity increase over time, but the differences also become subtler with a greater continuity within lineages. Interestingly enough, this also follows a path of angiosperm and insect radiation during the Cretaceous. As flowering plants become more successful (stimulating in turn dinosaur evolution), insects radiate to exploit it, and mammals diversify to exploit them. It’s a chain reaction begun by the evolution of flowers leading to an incredible diversity of life on every tropic level.  It’s a fascinating look into evolution.

Mark Loewen of the Natural History Museum of Utah talked about familiar territory for me considering my experience with the Field Museum: the Great Lakes of Utah. Back in the Eocene, four large freshwater bodies formed the heart of the tropical Green River Formation: Gosiute, Uinta, Claron, and Fossil. In this tropical land, the rhinolike Uintatheres and bearlike bird Gastornis ruled. The tiny horse Protorohippus ate fruits and leaves in the dense rainforest, stalked by the catlike Patriofelis. The first American bat Icaronycteris, lacking echolocation, would have to compete with the birds for insects and other small prey.  In the water, a flightless rail similar to those of the Ice Age pacific shared the habitat with the incredibly successful Presbyornis, boavid snakes, turtles, paddlefish, huge gar, the common fish Knightia, Diplomystus and Priscara, all being predated by the crocodile Borealsuchus. All of these were perfectly preserved, down to the feathers and scales.  
The reason for the preservation is the calcite deposits on the shore-the calcium dissolves in the lake, and when it blends with the organic material, it forms a hard, distinct fossil. The lake lived and died due to the Rocky Mountain orgeny-the uplift of the earth formed high bowls and streams ran from the young mountains to feed them, but the continued lifting cut the streams as well, and the Oligocene drying destroyed the entire habitat. I would strongly recommend Lance Grande’s book on Fossil Lake for more information.

The next talk has a special connection to me: in my human evolution class, my teacher proposed a new technique on determining fossil environments via the teeth of bovids present. Allison Bormet of the University of Illinois Bloomington chose a different approach: the limbs of ruminants. Her beginning using living ruminants ran into problems early: zoo ruminants show a lot of individual variation, and their limb bones are shaped by their current environments which have little to do with their wild habitats. Instead, she went to the IUCN and its species distribution map, which helped place bovid species in proper environmental contexts. 

The good news is that fossil ruminants all have present analogues. The bad news is that their limbs don’t preserve as often as their teeth.  Fortunately, ungals are tough little bones, especially for relatively large digitigrade cursorial animals. Bormet managed to even work out an equation: Body size X Vegetation cover=ungal size.  Of course, this is just the beginning of the study, and she has yet to correlate it to tooth studies and apply it to extinct taxa, but it shows a lot of promise and I can’t wait to hear what comes next.

Dr Robert Boessenecker of the University of Charleston finished Paleofest with his lecture of Mysticete, or baleen whale, evolution. Mysticete fossils fortunately have very unique and diagnostic ears. The transitional families between the Eocene Archaeocetes and Miocene Mysticetes, he explained, are the Aetiocetids and then the Eomysticetids in the Oligocene. The Aetiocetes retained the teeth of the Archaeocetes, but the Eomysticetids lost their teeth. Like other whale families, they are well-represented in North Carolina, Australia, Baja California, and especially Japan and New Zealand

New Zealand’s Oligocene and Miocene Otekaike and Kokoamu formations are rich in whale fossils, particularly basal Eomysticetes that still have trace teeth like Mataponui, Tokarahia, and Waharoa. They are at the point where the Mysticetes begin to evolve temporomandibular joints that sacrifice biting strength from the Archaeocetes for the ability to expand their jaws to a wider gape. The closest living relatives to them are the grey and right whales, the most basal baleen whales. The talk was a fascinating look into the amazing diversity of whale genera during the late Oligocene of New Zealand, making it the grand finale to this year’s Paleofest.

Once again, I recommend Paleofest-there’s something for everyone! It’s worth the drive out to Rockford and the hefty price tag for this annual celebration of paleontology. I encourage my readers from the Midwestern US to give it a visit. I know I’ll be there next year! See you then!

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