Can you see the Dinosaurs?

Now I didn't take all these photos in my garden, but I wanted to illustrate some of the similarities between the extinct dinosaurs and their living avian descendants. The  first 4 photos were taken at Taronga Zoo in Sydney, The Raven at Kangaroo Island in South Australia and the last 2 on my farm.

Firstly lets have a look at the legs on these avian dinosaurs or birds as we commonly call them.

Our first example is probably the most dangerous pair of dinosaur-like legs to be strutting around these days. Although the Cassowary is not carnivorous, it does possess a huge claw on the inner toe of each foot. This toe is only half as long as the others (in a skeletal sense) but makes up the rest of its length with a strong sharp claw. Althought this is primarily a defence mechanism, it is powerful enough to punch through corrugated iron or squishy people who get too close. Several dinosaurs also had a claw adaption like this including the Velociraptor.

More important than the claw, is the position of the legs. All dinosaurs have their legs directly underneath their bodies, regardless of whether they are walking on two legs or four. Birds and mammals have the same style of leg structure. 

Another feature of the Cassowary is the striking colour usage - but I'll come back to that in another post.

This charming Emu was very obliging for his closeup shots (I was drumming to him as he drummed - vocalised - which attracted his attention, hopefully I can talk about sounds later too).

People often have the image in their minds that birds are covered in feathers - and for most of their bodies that is pretty accurate, although feathers can vary widely across species. The Emu is flightless and so does not need the stiff plumage of a bird such as the Raven below. Instead some of the feathers are mere filaments - almost wispy hairs with the skin visible beneath them. There have now been many dinosaur fossils found that include the impressions of feathers around the skeleton, much like those you can see here. The beak area and legs are usually without feathers and much more like those of their ancestors.

Apart from the tail being made up of long feathers attached to a stubby tail instead of a long bony tail, there is a lot about the silhouette of this Raven that makes me thing of small predatory dinosaurs. This is the real purpose behind all these ramblings. There is so much we cannot tell from simply looking at the fossils themselves, but when we look at analogues and descendants of those animals we can begin to fill in the gaps and bring the extinct dinosaurs to life. Watching this fellow strut across the carpark towards the trees, watching for threats and opportunities (like dropped food), it was very easy to imagine a small omnivorous dinosaur doing the same millions of years ago.

Dinosaurs and Birds both lay eggs with hard shells. These tiny beauties were found in the garden inside an old animal transport cage that had been forgotten in the grass. I don't yet know who they belonged to, but the eggs were not fertile or fresh. The nest composition is grass, horse hair and soft cashmere from our goats. Dinosaur nests have also been found fossilised, although often it is the hard eggs only, rather than the composition material of the nest. Again we can make observations of existing species that help up put dinosaur discoveries into perspective. In Montana, USA a discovery was made of many giant nests, each with multiple eggs and located about 12m away from each other. The distance was about the length of one of the adults of this species - Maiasaura, and the area may have looked like a colony of giant seagulls nesting together. Inside the nest was plant material, perhaps what the parents brought for their chicks to eat. How do we know that? Skeletons of newly hatched or almost hatched baby dinosaurs were also found and their skeletons were not developed enough to allow them to leave the nest immediately and fend for themselves - they needed parental care - like many modern birds. Eggshell was also found crushed into the bottoms of the nest - an indicator of chicks moving about within the confines of their safe brooding area.

Moving about in groups while foraging is a strategy we have seen mentioned often during our lectures, and there are many reasons for it. We have fossilised footprints and trackways that show some dinosaurs also did this too. Although these Cockatoos do spend some time wandering on the ground like their ancestors, their ability to fly off in a time of danger means we are less likely to find footprints of them. You can see where they have been though - if you look closely at the image you can see little brown dots - these are the tufts of grass that have been pulled up as the birds search for tasty roots to eat (or at least I think that's what they are eating).

I hope this ramble helps to illustrate some of the reasons for this blog and unusual focus for a study of animal behaviour.