Sunday, February 17, 2013

3 Reasons Why Byronosaurus is Awesome

Artist's depiction of Byronosaurus jaffei from Wikipedia,
Probably one of my favorite troodontids due to the incredible number of specializations it has.
Deep down, Byronosaurus has always held a special place within my heart. I first learned about this particular animal in 2008 (even though it was discovered in 1993), after looking through an art book titled Feathered Dinosaurs: The Origin of Birds, written and illustrated by John Long and Peter Schouten, with a forward by Luis M. Chiappe. This was probably one of my favorite books of my earlier junior-paleontologist years, and it still pleases me to simply thumb through the wonderfully fantastic illustrations. They are a feast for the eyes!

Looking through the book for the first time, I remember coming across this particular creature with its bizarre appearance and interesting anatomy looking back at me with its thin snout, numerous tiny teeth, and huge eyes. Over time, I became fascinated with the animal and I decided to examine it further. Three distinct traits of its anatomy and behavior stood out at me more so than most other dinosaurs. At this point, the only word to define what I think of this beast is simply awesome — and I will explain why.

Its Quirky Ears
An owl's skull showing the bizarre placement of its ears
Byronosaurus had similar ears, if not more bizarre....
Byronosaurus' most notable feature is one that is not obviously seen in any illustration of the animal, but you would probably notice it instantly if you were holding a skull of the creature. The ears of Byronosaurus are extremely large, but curiously, they're also asymmetrically aligned on the head, a trait once thought to be exclusive to only one other family of animals, that happen to also be Dinosaurs — owls.

Some species of owls have asymmetrical ears in order to enhance their hearing, as it allows a wider area of sounds to enter their ears, as well as allows them to pinpoint the exact location of prey (note that not all species of owls do, however, as some species have perfectly aligned ears). The famous facial disks of many owl species also help channel sound into their ears, as their shape acts like a large satellite dish. Some northern species are quite capable of locating a single lemming in more than a foot of snow simply by listening to its movements from perches, sometimes more than a half-mile away. All in all it's an extremely effective way of locating prey, and I'm surprised that it isn't an anatomical feature more commonly found in animals.

Byronosaurus was, I believe, the first troodont to show such a feature, as its skull is one of the most complete of any troodont (according to my research, but please correct me if I'm wrong). Other troodonts also have been shown to possess asymmetrical ears, which suggests that hearing was very important for these animals as a whole, and studies of the braincase show that indeed it was one of their primary senses, maybe even more so than sight. Unlike owls however, Byronosaurus' inner and middle ear has also been shown to be asymmetrical, while owls have it limited to the external surface. Does this mean that Byronosaurus was more sensitive to sounds than owls? Further study is needed before we can tell, but it certainly does suggest that hearing was extremely important for these animals.
Pinocchio Jaw
Photo of the holotype's snout
Along with being the first non-strigiforme animal to show an asymmetrical ear, Byronosaurus' well-preserved skull has also shown a very bizarre form of dentition and jaw morphology unlike that of most dinosaurs. Most troodontids are known for having a wide, U-shaped jaw, with blade-like teeth with coarse serrations and a large denticle size. This has lead troodontids, and famously Troodon itself, to be thought of as possible omnivores, as their jaws resemble herbivorous and omnivorous lizards like Iguanas.

Byronosaurus' jaw on the other hand, is anything but that of a typical troodont. The jaw is elongated, pointed, depressed, and very narrow, a far cry from the broad, rather deep, U-shaped mouth of other troodonts, and giving Byronosaurus a very-pointy face, making it basically the dinosaur version of Pinocchio. Along with that, Byronosaurus also has very different teeth; they are small, needle-like, lacking serrations, and there are far more of them than in other troodonts. This all points towards a very different method of feeding, but just what was that method?

The ears may give us a clue. As I said, owls use their amazing hearing to pinpoint the exact location of hidden prey without even seeing it. Byronosaurus was likely able to do similar things with its ears, and the teeth could be used to grab onto small prey. However, other troodonts have asymmetrical ears and are currently thought to have fed on small prey items in this way, but they don't have Byronosaurus' unique dentition, which seems far more specialized in that regard.
A theory was put forth to explain its skull in the Feathered Dinosaurs book I mentioned. The authors noted that the snout and jaw are fairly reminiscent of the African Bat-Eared Fox, which is a very specialized species of canine that feeds on almost an entirely insectivorous diet. The fox's jaw is long and narrow in order to probe into cracks and holes to get at termites, which is its primary food source, and it uses its small, needle-like teeth to cut up the tough exoskeletons of these invertebrates. Interestingly enough, its huge ears are used in pinpointing the exact location of insects crawling among foliage or underground. Do these traits sound familiar? (Vid above showing some Bat-Eared Foxes in action)
So perhaps Byronosaurus is a Bat-Eared Fox analogue; but there is another possibility we should explore. The toothy dentition is also similar to that of fish-eating animals like the Indian Gharial and spinosaurid theropods, so perhaps Byronosaurus was a piscivorous troodont. It's notable that some species of owls, like the Balakiston's Fish Owl and Pel's Fishing Owl, as their names suggest, are dedicated piscivores. These owls use their ears to hunt fish at night by listening for disturbances on the surface of the water, so this is also an equally good fit for Byronosaurus' possible diet. As for which is more likely, I'll leave that for the scientists as well as all of you to decide. (Vid above showing some owls fishing in some artificial ponds)
Eggs, Young, and... absence in Parenting? (Gasp!)
As we all know from almost 100 years now of collecting dinosaur eggs, dinosaurs had incredibly varied ways of raising young and making nests. Sauropods abandoned their young, but gave them a good first chance by laying them near volcanic vents; many hadrosaurs constructed large nests and guarded their young in large colonies; and many ceolurosaurs may have been brought up mostly by dad. Given this incredible diversity of breeding habits in dinosaurs, should it be a surprise that we may have found one more?
In 1994, two very young, juvenile skulls of Byronosaurus were discovered by Mark Norell, which give us a good look at exactly how this weird dinosaur grew up. (Note, however, that they are only tentatively assigned to Byronosaurus. There is an alternative possibility that they belong to the recently discovered Zos Canyon troodontid, which has yet to be described.) The juveniles were extremely young, possibly even embryos, and show extremely large eyes and shortened faces, giving them the "cute" look characteristic of young animals. However, what is interesting is the location where these eggs were found: deep in the heart of a oviraptorid nest, with a ring of oviraptorid eggs surrounding the specimens.
Oviraptorid were primarilly herbivorous theropods common in the region at the time. Oviraptorid adults, juveniles, and nests have been well-documented for almost 20 years now, but this is certainly a conundrum. How do you get two juvenile troodontids in the nest of another dinosaur? Theories have gone back and forth for a while about this.
One explanation is that the adult oviraptorid was feeding on the juveniles and left their remains in the nest. A possibility, but modern birds often try to keep their nests clean of feeding debris, and indeed many species will often carry fecal matter and uneaten scraps off to make the nest less conspicuous to predators. Birds from ostriches to eagles do this regularly, so why the oviraptorid would leave its nest dirty and conspicuous like this would not make much sense. (The video above shows an adult female Robin removing its young's fecal pellets)
Another possibility is that the juveniles were preying on the unborn oviraptorids. Predators will often feed on eggs of other young, but still, how bold must these juveniles be to want to take on an oviraptorid nest when they are litterally just a few days out of the egg?
The last possibility, however, really caught my attention. Some have suggested that the juveniles were present in the nest because Byronosaurus was a brood parasite. Brood parasites are animals that benifit by laying their eggs in other animal's nests, and in return have their eggs and young cared for by the "host" parents. Brood parasitism is surprisingly common in birds, evolving independently at least seven times in birds, as well as in a number of reptile and even insect lineages. Most famous of these animals is the Common Cuckoo (Cuculus canorus), which lays its egg inside another bird's nest. To see this animal in action, David Attenborough has a great documentary on its particular behavior, which you can see here.
While it does seem like we're speculating quite a bit on this topic, there is some evidence to back up this theory. For example, the fact that there are two individuals is evidence in itself. Unlike modern birds, which can only lay one egg at a time, reptiles and dinosaurs lay two eggs at a time. If a female Byronosaurus really did lay its eggs in the oviraptorid nest, then we should expect two young to be present because that is what the female would end up producing. 
If these troodontids really did practice brood parasitism, it would certainly be a major scientific discovery that would tell us a lot about dinosaur breeding behaviors. But of course, would it really be that much of a surprise? After all, as noted above, dinosaurs exibited a number of extremely varied forms of reproduction, and since all dinosaurs were egg-layers, there are a huge number of options available for some species to cheat on their parental duties.

So there you have it: Byronosaurus jaffei, the assymetrical, pinocchio-nosed, insect-eating, fish-catching, parental cheating son-of-a-gun dinosaur. I hope this has been an informative post, and as you all probably know by now, I'm open to taking questions of all kinds.

Also, for those who are interested..the next edition of AncientPlanet Online Journal should be coming out very soon. I don't have a date, but my article will be appearing in it along with numerous other articles submitted by paleontologists, academicians, scientists, grad students and the like. You can also expect a blog post here covering everything I went over, as well as possibly some stuff that was scrapped at the last minute. ;)

Meanwhile, stay sharp, and I'll see you on the net!

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