Friday, April 1, 2016

What Did Mesozoic Maniraptors Eat? Results from My Senior Thesis

I don't neglect this blog just because I can. At last, it is time to unveil what has been eating up most of my time: my senior thesis research. Contrary to some of my previously-expressed concerns, there is no risk in releasing my findings in this fashion because everyone knows that blogs are entirely worthless for any form of scientific discourse. When I get around to submitting my thesis as a manuscript, those journals will have no idea that I've already publicized this information, because what proper academic (including editors of scientific journals) ever reads or writes blogs?

There has been much debate and speculation on the diets of Mesozoic maniraptors, in part due to their diverse skull morphology that frequently deviates from what is expected of "typical" theropods. In recent years, it has been popular to argue on morphological and biomechanical grounds that herbivory and omnivory were widespread in Mesozoic maniraptors.

A digital reconstruction of the skull of the therizinosaur Erlikosaurus in multiple views, from Lautenschlager et al., 2014.
A selection of oviraptorosaur snouts, drawn by Jaime Headden, licensed.
A selection of enantiornithine skulls, from O'Connor and Chiappe, 2011.

However, the existence of fruit-eating alligators and meat-eating ruminants demonstrate that morphological inference of animal diets is unreliable at best. Direct observations are what count. For my senior thesis, I looked at direct evidence of maniraptor diets (gut contents and feeding traces) throughout the Mesozoic. The results can be seen in the graph below.


The trend is clear: for most of the Mesozoic, most maniraptors were eating absolutely nothing! This is at great odds to the popular interpretation of widespread herbivory in these dinosaurs, but it makes a good amount of sense. After all, if these animals were not eating anything, their skull morphology would not be at all constrained by diet and would be free to take on other functions such as sexual display and species recognition. This revelation brilliantly explains the diversity of skull shapes in maniraptors.

Another finding of interest is the spike in hypercarnivorous maniraptor species during the Campanian. The most parsimonious explanation for this observation is that, considering the evolution of all organisms is driven by the aesthetic preferences of a single Holocene primate species (66 million years away from the last non-neornithine maniraptors), this was an attempt by the maniraptors to become more awesome, because feeding on fish or plants is lame. (And fish is not meat, what are you talking about?) Unfortunately for maniraptors, all carnivorous species died out prior to the Maastrichtian, likely because that ecospace was already dominated by other types of theropods.

What of the increase in rock-eating species during the Aptian? The great abundance of fossil species and specimens found dating to the Aptian is reflective of an increase in the generation of sedimentary rock during this time period. Evidently, a number of maniraptor species became adapted to take advantage of this resource.

References
Awesomebro, I. 2013. Y animulz musth b kewl enuff 4 me. Annals of Awesomebro 95: 26-910. doi: x8615/asum.2399

Blank, D.A. 2003. On the carnivorism and feces eating of Gazella dorcas Linnaeus, 1758 and other ungulates. Mammalia 674: 579-585.

Lautenschlager, S. 2013. Cranial myology and bite force performance of Erlikosaurus andrewsi: a novel approach for digital muscle reconstructions. Journal of Anatomy 222: 260-272. doi: 10.1111/joa.12000

Lautenschlager, S., L.M. Witmer, A. Perle, L.E. Zanno, and E.J. Rayfield. 2014. Cranial anatomy of Erlikosaurus andrewsi (Dinosauria, Therizinosauria): new insights based on digital reconstruction. Journal of Vertebrate Paleontology 34: 1263-1291. doi: 10.1080/02724634.2014.874529

O'Connor, J.K. and L.M. Chiappe. 2011. A revision of enantiornithine (Aves: Ornithothoraces) skull morphology. Journal of Systematic Palaeontology 9: 135-157. doi: 10.1080/14772019.2010.526639

Platt, S.G., R.M. Elsey, H. Liu, T.R. Rainwater, J.C. Nifong, A.E. Rosenblatt, M.R. Heithaus, and F.J. Mazzotti. 2013. Frugivory and seed dispersal by crocodilians: an overlooked form of saurochory? Journal of Zoology 291: 87-99. doi: 10.1111/jzo.12052

Zanno, L.E. and P.J. Makovicky. 2011. Herbivorous ecomorphology and specialization patterns in theropod dinosaur evolution. Proceedings of the National Academy of Sciences, USA 108: 232-237. doi: 10.1073/pnas.1011924108

Tuesday, January 5, 2016

Favorite Maniraptor of 2014 Results


Much as I predicted, Anzu took this one by a landslide. Changyuraptor came in second, to be expected for a well-preserved dromaeosaurid. I appear to have been the only one who voted for Eopengornis, but come on, check out that fossil. Not to mention the interesting implications for rectricial evolution in avialans (possibly confirmed by the publication of Chiappeavis last year).

Holotype of Eopengornis, from Wang et al., 2014.

As for this year's poll? We have two dromaeosaurids as strong contenders, the giant Dakotaraptor and the excellently-preserved Zhenyuanlong (both of which, coincidentally, preserve evidence that wings were retained in flightless dromaeosaurids), but I imagine the unexpectedly bizarre Yi will be tough to beat.

Friday, January 1, 2016

Review of 2015

It was a busy year and the Tumblr suffered for it, but, considering that I didn't end up blogging significantly less than I did last year, I'm reasonably satisfied with what I did on here. Jurassic World came out this year, causing much discussion in the paleontological community. I have nothing to add about the film that has not already been said, but its release did give me the prompt to finish up another story arc for the comic. My travel destinations this year included New York, Osaka, and Dallas, the last of which hosted the first SVP conference I've attended. Additionally, I indulged in some frivolous nonsense, including a Twitter meme and the obligatory April Fools' post.

Cover image for the "Triassic Park" storyline.

Though not directly related to the blog, the unexpected stardom of my Cartoon Guide to Vertebrate Evolution, which I drew this past summer, is worth a mention. It is by far my most popular work on DeviantArt (in terms of number of favorites and comments), has been made available on merchandise by popular request, earned me interviews with Terp Magazine and the National Center of Science Education, and has reportedly been used in presentations at academic conferences. Wow.

The Cartoon Guide to Vertebrate Evolution.

Onward to new maniraptor discoveries of the past year. In January, newborn chickens were found to mentally map numbers the same way humans do. New material of Caenagnathus and Elmisaurus was described. Linheraptor was argued to represent a separate taxon from Tsaagaan. New studies came out on emberizoid phylogeny and seed dispersal by emus. Newly-named maniraptors included the Eocene trogon-like avialan Foshanornis songi and the enantiornithine Houornis caudatus (formerly a species of Cathayornis).

Chicks trained to circumnavigate panels displaying a target number of identical elements (A), showing a preference for the left panel when navigating past numbers smaller than the target number (B) and for the right panel when navigating past numbers larger than the target number (C), from Rugani et al., 2015.

In February, altruistic behavior among northern bald ibises flying in V-formation was reported. The genomes of Darwin's finches were sequenced. Caenagnathasia was reported from the Iren Dabasu Formation for the first time. Male peafowl were discovered to use infrasonic signals during courtship. A trade-off was found between sexual attractiveness and parental effort among male grassquits. The postcranial anatomy of Gansus was described. New studies came out on the phylogeny of Todiramphus kingfishers and harriers, the body mass of Mesozoic avialans, the barb geometry of asymmetric feathers in Mesozoic paravians, the loss of taste in penguins, the mechanics of avian feet during perching and grasping, the craniocervical myology of Falcarius and Nothronychus, and the evolution of gastralia and sterna in paravians. Newly-named maniraptors included the Miocene heron Nyctisoma robusta.

Male Indian peafowl displaying, photographed by Nihal Jabin, licensed.

In March, purportedly distinct redpoll species were found to have largely undifferentiated genomes. The blue-bearded helmetcrest, once thought extinct, was rediscovered alive. Natural selection and sexual selection were discovered to operate on different axes of variation in avian plumage color. New studies came out on the origin of crown passerines and the phylogenetic position of the mandanga and the São Tomé shorttail. Newly-named maniraptors included the enantiornithines Dunhuangia cuii and Yuanjiawaornis viriosus, the Cretaceous euornithine Juehuaornis zhangi, the phorusrhacid Llallawavis scagliai, and the Perijá tapaculo (Scytalopus perijanus).

Phylogeny of motacillids showing the mandanga and the São Tomé shorttail as members of the clade, from Alström et al., 2015.

In April, new ecological information for the black tinamou was reported. A new specimen of Longipteryx was described. Transoceanic migration in blackpoll warblers was documented. New studies came out on the size of the gastral basket in Mesozoic paravians and the ontogeny of Deinonychus. Newly-named maniraptors included the scansoriopterygid Yi qi, which preserved evidence of membranous wings, a contender for the most unexpected dinosaur discovery of at least the past decade.

Holotype of Yi qi, from Xu et al., 2015.

In May, evidence of nest site fidelity in troodonts was described. Contagious yawning in budgerigars was reported. The trace fossil Wupus agilis was argued to represent a large avian footprint. New studies came out on the function of the alula in flight, the development of the avian snout and hallux, the phylogeny of hesperornithines, the evolution of sexual dimorphism in wood warblers, differences in exploration behavior of carrion crows and common ravens, and the safekeeping of tools by New Caledonian crows. Newly-named maniraptors included the dromaeosaurid Saurornitholestes sullivani, the Cretaceous euornithine Archaeornithura meemannae, and the Sichuan bush warbler (Locustella chengi).

Chicken experimentally induced to develop snout morphology similar to the ancestral amniote condition, compared to a typical chicken ("control") and an alligator, from Bhullar et al., 2015.

In June, the osteology of Nothronychus was described in detail. Rapid head rotation was found to help lovebirds maneuver quickly. Correlation was found between avian altriciality and toe orientation. The pelvic limb musculature of the ostrich was modeled. New specimens of Masillapodargus and Tonsala were described. Brown thornbills were discovered to mimic a chorus of alarm calls to dissuade nest predators. An egg once thought to belong to a ceratopsian was reevaluated as an enantiornithine egg. Several purported stem parrots were reconsidered and found to have been stem passerines. New studies came out on the phylogenetic position of Balaur, the bone histology of Aepyornis, convergence in feather crests of domestic doves, the evolution of sternal ossification in ornithothoracines, ontogenetic shape change in the chicken brain, and mimicry in female cuckoo finches. Newly-named maniraptors included the enantiornithines Cratoavis cearensis, Holbotia ponomarenkoi (a longtime nomen nudum), and Parapengornis eurycaudatus.

Brown thornbill, photographed by J.J. Harrison, licensed.

In July, roosters were found to crow in sequence based on their social rank. The genome of the North Island brown kiwi was sequenced. The helmeted woodpecker, once thought to belong to Dryocopus, was found to be a species of Celeus. Newly-named maniraptors included the oviraptorosaur Huanansaurus ganzhouensis, the dromaeosaurid Zhenyuanlong suni, and the Miocene condor Kuntur cardenasi.

Holotype of Zhenyuanlong suni, from Lü and Brusatte, 2015.

In August, hummingbird tongues were reported to function as micropumps. Canaries were discovered to be flexible in the timing of learning songs. Blue-footed boobies were found to use behaviorally-induced camouflage to hide their eggs. New studies came out on chemical defense in common cuckoo chicks, opisthotonic head displacement in chickens, the endocranial anatomy of Eocene stem penguins, the ultrastructure of Anchiornis feathers (supporting identification of preserved microbodies in the fossil feathers as melanosomes), the diversification of avians across the K-Pg boundary, and inference by exclusion in Goffin's cockatoos. Newly-named maniraptors included the enantiornithine Pterygornis dapingfangensis.

Amazilia hummingbird tongue filling with (dyed) nectar, from Rico-Guevara et al., 2015.

In September, king penguins were found to be able to distinguish odors of conspecifics. Zebra finches were discovered to pick mates based on behavioral compatibility. Black-chinned hummingbirds were reported to nest in association with Accipiter hawks to increase breeding success. Mated pairs of southern rockhopper penguins were found to winter in separate locations. Brown-headed cowbirds were shown to select hosts in response to reproductive success. American crows were discovered to gather around dead conspecifics as a means of learning about danger. New studies came out on bone histology of penguins, the emergence of social rank in monk parakeets, and the function of colored beak spots in king penguins. Newly-named maniraptors included the Pleistocene barn owl Tyto cravesae and the flightless Pleistocene duck Shiriyanetta hasegawai.

Southern rockhopper penguin, photographed by Stan Shebs, licensed.

In October, a well-preserved enantiornithine wing was described. Recent advances in research on bird origins was reviewed. Kleptoparasitism in gentoo penguins was reported. New studies came out on cooperation in common ravens, the evolution of body mass in pan-alcids and wing shape in avians, the phylogeny of neornithines, the morphology of penguin feathers, and the relationship between skeletal and total body mass in birds. Newly-named maniraptors included the Miocene shorebird Hakawai melvillei and the large dromaeosaurid Dakotaraptor steini.

Phylogeny of neornithines, from Prum et al., 2015.

In November, a supergene was found to be responsible for divergent male morphs in ruffs. Blue-capped cordon bleus were reported to use a tap-dancing courtship display. Pigeons were discovered to assume leadership based on speed. Zebra finches were observed negotiating vocally over parental care. Cerebavis was reevaluated and found to be a euornithine. New studies came out on the function of hindlimb feathers in Mesozoic paravians, the evolution of avian brain modularity, the hindlimb myology of moa, the social network dynamics of New Caledonian crows, and the foraging behavior of great tits. Newly-named maniraptors included the hesperornithine Fumicollis hoffmani, the plotopterid Stemec suntokum, and Paragallinula, a new genus for the lesser moorhen.

Male ruffs in breeding plumage, photographed by Arjan Haverkamp, licensed.

In December, spontaneous tool use in greater vasa parrots was reported. Asymmetric limb control during bipedal locomotion in guineafowl was described. New studies came out on heat dissipation in calliope hummingbirds, locomotion in large ground birds, hook tool use in New Caledonian crows, cervical pneumatization in ostriches, structural color in Eurasian jay feathers, and the diversification of neornithines. Newly-named maniraptors included the possible dromaeosaurid Boreonykus certekorum, the enantiornithines Feitianius paradisi and Chiappeavis magnapremaxillo, the Eocene possible suliform Mangystania humilicristata, and the extinct Holocene rails Rallus adolfocaesaris, Rallus carvaoensis, Rallus lowei, "Rallus minutus" (preoccupied), and Rallus montivagorum.

Greater vasa parrot, photographed by AEM, licensed.

Thursday, October 29, 2015

Redbubble shop!

After receiving some requests for merchandise of my Cartoon Guide to Vertebrate Evolution, I decided to open a Redbubble shop.

Suggestions for other designs to include are welcome. (However, I will not upload any of my fan art of copyrighted works as designs.)

Perot Museum of Nature and Science

In addition to the Dallas World Aquarium, I visited the Perot Museum of Nature and Science during the course of SVP. The museum had made admission free for SVP attendees while the conference was going on, which was a treat.

Being accustomed to the Smithsonian's National Museum of Natural History and the American Museum of Natural History, the Perot Museum's exhibit halls appeared much smaller in comparison. However, size does not translate to quality, and the Perot made good use of its space. On top of that, it is very architecturally interesting.

The museum takes visitors straight to the top floor and has them work their way down. As additional enticement, the top floor is where the dinosaurs are. The centerpiece of the fossil hall is a Tyrannosaurus pursuing an Alamosaurus. (There is also a mounted mountain lion and a deer as a modern example of a large-bodied predator-prey duo.)

The sign says Hypsilophodon, but this dinosaur will probably get its own genus.

Tenontosaurus, without a Deinonychus in sight!

They had a nice series of mosasaur mounts, including this Tylosaurus.

In museums, Archelon and other large turtles can fly.

To represent the North American-Asian biotic interchanges in the Cretaceous, we have the skull of Tarbosaurus...

... and the skull of Gorgosaurus.

The skull of Protohadros.

So that's the way they're swinging. Hmm.

The giant beaver Castoroides.

Adult Edmontosaurus and juvenile Ugrunaaluk.

Pachyrhinosaurus perotorum, whose trivial nomen shares the same namesake family as the museum.

Skulls of Torosaurus and Styracosaurus.

A flight of stairs leads to the museum's bird exhibits, which was nicely symbolic. They open with a display on avian evolution. There's Deinonychus!

Here's Archaeopteryx.

A life restoration of... Flexomornis? Interesting choice considering it is known only from fragmentary limb bones, but it all falls into place when one remembers that it was discovered in Texas. I don't buy the beak or the foldable tail fan.

Hesperornis, among few marine dinosaurs of the Mesozoic.

Representing modern birds is a pelican.

I like how the alternative phylogenetic positions for Archaeopteryx are shown here. It hasn't turned up as a non-avialan in a while, but it was presumably still a hot topic when these exhibits were made.

Though we didn't have time to explore the rest of the museum for long, getting to see the fossils was enough to satisfy me for the time being. On the whole, I had a great time in Dallas!