We have returned from the Canadian Society of Vertebrate Palaeontology 2017 conference in Dinosaur Provincial Park, and it was a blast! It was great to catch up with our friends and colleagues, and also great to see all of the ground-breaking research being done by early career paleontologists.
There's a lot happening in the next month for me. Tomorrow I grade for my next level in karate - this will be the first exam I've had since my candidacy! On June 3 I'll be leading the annual birding hike to Bullmoose Marshes, hosted by the Wolverine Nordic and Mountain Society. June 9 - 11 I am involved with hosting the British Columbia Field Ornithologists meeting, and am giving the afternoon keynote presentation...on Cretaceous birding, of course! I am also working with colleagues to finalize plans for a track site visit - stay tuned!
One aspect of my upcoming summer that is not busy is my field work life. With this year's field budget of a whopping $0.00 (don't spend it all in one place!) we do not have any large field excursions scheduled. That doesn't mean that we don't have plans were funding to materialize. Here's a list of the palaeontology projects we could be working on this summer:
1. We still have at least four years of work to do on the Six Peaks Dinosaur Track Site near Hudson's Hope, British Columbia. Here's a video showcasing the site,
2. A hadrosaur bonebed (duck-billed dinosaurs), the first dinosaur bonebed for British Columbia. This site was featured in "Dino Hunt Canada," with an airlift of the articulated skeleton of one of the hadrosaurs. We've done as much digging as we can by hand. Watch the video!
4. A potential new dinosaur excavation site that needs several test pits dug to determine the extent of the bone-bearing section.
What this summer does is give me an opportunity to spend more time at my neoichnology (modern track) sites. My first step was to see what shorebirds have arrived in the area, so I went out yesterday to spot check my usual sites.
My first trip was to Bullmoose Marshes, about 30 km away from the Research Centre. This site is in important stop-over and summer breeding ground for a fantastic variety of birds. It was a gorgeous day to be outside.
Me, squinting into the sun, which gives me a pensive look. No one can look pensive at this marsh.
While I did hear and see a great variety of birds, including two Trumpeter Swans, I only saw one shorebird: a Solitary Sandpiper.
My submission for Worst Bird Pic. There's a Solitary Sandpiper in here!
Of course, visiting sites always provides reminders of Why We Can't Have Nice Things. These boardwalks were put in by volunteers who had to raise funds for the materials. But I guess that all pales in comparison to twue wuv.
Yes, we're all very impressed that your love for C.C. is so great that vandalism is your answer.
The water levels are very high at the marshes right now, so there was no exposed ground to check for shorebird footprints. In addition to the Solitary Sandpiper, Spotted Sandpiper and Greater Yellowlegs also frequent this marsh, but perhaps they have not yet set up their breeding territories.
My next stop was to the local dump. I often find myself going to to the dump for bird-related activities. The sewage treatment ponds are full of breeding Canada Goose, and several species of ducks and swallows can also be found. I discovered in 2016, while I was dropping off my recycling, that Killdeer also frequent one of the cleared off, rocky areas.
The dump did not disappoint! Here's a trackway of a Killdeer!
Killdeer trackway. 10 cm from outer dot to outer dot.
This made me a very happy ichnologist! These tracks were made that morning. If they were any more fresh, the Killdeer would still be standing in them.
I also saw some tracks that were made a day to a few days before, meaning that the Killdeer were not just making a one-time stop at the site. I'm hoping this means that they are getting ready to establish their breeding territory, and that I haven't missed all of the fun of them doing their nest scrape displays!
A not-so-fresh Killdeer trackway at the same site. Notice the edges are less clear than the above trackway.
Over the next few days I'll be paying this site early morning visits to see how active these Killdeer are, and where they feel is a good spot to build a nest.
It's the common image associated with theropod dinosaurs: they are either chasing something down to eat it, or they are eating it. Every lazy bit of sad science storytelling depicts theropods consumed with one objective: devouring poor innocent plant-eating prey. From Lex asking "Where's the goat?" in Jurassic Park to Littlefoot's mom being killed by Sharptooth, theropods (and all carnivores, really) get painted with the "evil" brush and brushed off as mindless killers.
It's still too soon for me to post Littlefoot's mom's death.
Logically we know that theropods were more than just heartless (our words and judgement) killing machines. Theropod dinosaurs were and still are animals with a complex suite of behaviors that we would anthropomorphize as "tender" and "gentle."
We know that theropods built nests and incubated their young: research by Tanaka et al. (2015) demonstrated the different nesting strategies that dinosaurs used based on egg shell porosity. Egg shell is not solid: it is full of tiny pores that allow for moisture and gas exchange to happen between the egg and its environment. Based on modern nesting crocodiles and birds, the more porous eggshell is, the more likely it was that the eggs would be completely buried in a nest mound. Less porous eggs would only be partially buried with the upper surfaces of the eggs exposed. Maniraptoran theropods (dromaeosaurs, oviraptors, troodons, and our modern birds) have low porosity eggs, which would be partially exposed in the nest.
We know that theropods (at least the maniraptorans) engage(d) in nest building and egg brooding behavior...but what about the pre-nesting activities, like courtship? Our modern theropods are famous for their courtship behaviors. Check out the mating dance of the Flame Bowerbird...
...and now imagine Oviraptor doing this dance.
"Hold up! There should be evidence of male theropods having some skeletal differences that can be used to support possible mating dances, right? Right!?!"
Using the skeleton alone, the best way to tell if a theropod skeleton was male or female is to look for a structure called medullary bone: it's a special deposit in the hollow portion of theropod bones that acts as a calcium reserve for adding shells to eggs. Medullary bone is only going to occur in egg-laying (female) theropods. However, medullary bone is an internal structure: you can't tell by looking at the exterior of a bone whether it contains medullary bone.
So, are there any fossils that possibly support courtship activities in theropods? We may have fossils in the form of trace fossils...ichnology to the rescue! In 2016 we published on these enigmatic traces from the Early Cretaceous of Colorado. They are paired scrape marks made by the feet of large theropods (likely an allosaur.) No tracks led up to any of the scrape marks, showing us that the theropods dug down through the layer they were walking on.
Figure 1 from Lockley et al. (2016) showing the scrape marks.
Figure 3 from Lockley et al. (2016).
These marks were a puzzle at first. We initially thought that the trackmakers were digging for water, but the geology of the area showed that water was active and abundant. Next we considered that they were digging for food, but the sandy layer the theropods were digging down to was devoid of traces of most burrowing animals. Next we considered nest bowls and/or dust bathing. Both activities, like rooting around for food, tend to wipe out the marks made by digging (based on what we've seen with dust bowls made by Spruce and Ruffed grouse in our area.)
Also see this video of a Killdeer nest scrape ceremony. I know where Killdeer were nesting locally last year, so I'm hoping to get some of my own footage this spring.
To start the nest scrape ceremony, the male will define and defend their territory. They vocalize to nearby females, and demonstrate to them how good they are at digging out nests. A male may perform and create several nest scrapes during the pre-mating ceremony. If the female is satisfied with his performance, she allows the male to mate. One of the nest scrapes becomes the nest bowl.
There is a good chance that our large theropods were engaging in a courtship ceremony that involved scraping at the ground. It is not uncommon to have multiple males displaying in one location: game birds are a great example with their display arenas or leks, like the Greater Prairie Chicken.
Of course, we had to come up with an Early Cretaceous version of a theropod lek...
Figure 6 of Lockley et al. (2016). Yes, those theropods in the background are doing exactly what you think they are doing.
Recently a paper by Carr et al. (2017) published on the facial scales of the tyrannosaurid Daspletosaurus horneri(a new species) that has skeletal evidence of not just scales on its face, but very sensitive facial scales. How sensitive? These scales were likely more sensitive to touch than human fingertips. Why would a tyrannosaur have such a sensitive snout? I'll let the authors speak to that:
"ISOs [integumentary sensory organs] would have aided adult tyrannosaurids in harmlessly picking up eggs and nestlings and, in courtship, tyrannosaurids might have rubbed their sensitive faces together as a vital part of pre-copulatory play." (Carr et al., 2017)
We now have more than enough evidence to abandon the tired cliche of the one-dimensional killing machine image of theropod dinosaurs. Extinct theropods were just as multifaceted and complex as any of our modern theropods or animals that we see today. A carnivorous animal is not simply a vicious slaughterhouse on legs and wings: they attract mates and care for the young that they produce. The fact that they eat meat to support these tender activities should be free of judgement on our part. We should learn to appreciate all aspects of a carnivore's life and pass that appreciation on to the next generations.
While you are here, I highly recommend peeking into the tender lives of our modern theropods by watching live nest cams! Here are links to the nest cam I frequent. Most are nest cams of birds of prey, so you will see prey either in the nest or being brought to the nest.
Carr TD, Varricchio DJ, Sedlmayer JC, Roberts EM, Moore JR (2017) A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system. Scientific Reports 7, Article number: 44942 (2017) doi:10.1038/srep44942
Lockley MG*, McCrea RT, Buckley LG, Lim JD, Matthews NA, Breithaupt BH, Houck KJ, Gierlinski GD, Surmik D, Kim KS, Xing L, Kong D-Y, Cart K, Martin J, Hadden G. 2016. Theropod courtship: large scale physical evidence of display arenas and avian-like scrape ceremony behavior by Cretaceous dinosaurs. Scientific Reports 6:1–10
Mallon JC. 2017. Recognizing sexual dimorphism in the fossil record: lessons from nonavian dinosaurs. Paleobiology, doi: 10.1017/pab.2016.51
Persons SW IV, Funston GF, Currie PJ, Norell MA (2015) A possible instance of sexual dimorphism in the tails of two oviraptorid dinosaurs. Scientific Reports 5, Article number: 9472 (2015) doi:10.1038/srep09472
Tanaka K, Zelenitsky DK, Therrien F (2015) Eggshell Porosity Provides Insight on Evolution of Nesting in Dinosaurs. PLoS ONE 10(11): e0142829. doi:10.1371/journal.pone.0142829
