Posts Tagged 'eggs'

How many eggs were laid?

Here is a nice pile of eggs on display at the IVPP. As is quite common in dinosaur nests, there are several layers here and while it is subtle, there is a curve to the arrangement of the eggs to give an indication that these eggs were originally laid in a broad circle.

Clearly this nest is rather incomplete and would have originally contained many more eggs. Taking an estimate of that total from this little is probably a bad idea but there are more complete nests out there and some are apparently absolutely complete and every egg can be identified and counted. Great news in general of course, but does this mean we know how many eggs were laid by the mother?

You might think ‘well, obviously’ but sadly the situation is far less clear than this. Looking to the birds a great many small passerines lay two or sometimes even more clutches a year. Just finding a nest of half a dozen eggs doesn’t mean that this was the some total of the eggs laid by a mother that summer. Other birds are communal nesters with lots of females all dumping their eggs together into a single nest. Or males can solicit females to lay in their nest and so accumulate eggs from multiple females, though perhaps only one or two from each.

In short, even finding a nest of a couple of dozen eggs being brooded by an animal is no great guarantee that those eggs were laid by one female, or that was all she laid. It’s not, I hasten to add, a poor assumption but equally it’s far from certain. Which is rather a shame as obviously and understanding of the reproductive output of an individual (and thus a conceptual one for a species) can really help our understanding on dinosaur biology and ecology. I wouldn’t argue against using this kind of data, but I’d be quite cautious about how it could be used.

Pterosaur embryo

Pterosaur eggs have featured on the Musings before, most recently with the quite amazing Darwinopterus egg, but also before with a cast of one of only three known pterosaur embryos. Here though is a picture of an original specimen on display at the IVPP. Admittedly there’s not too much to see here in terms of details, but certainly it should be pretty obvious that there are a lot more long thing bones here than you’d find in anything that’s not a pterosaur or bat and in the Early Cretaceous that rather narrows down the candidates to one…. This specimen was referred at the time of description to Haopterus as it shows a couple of ornithocheirid features, and while the subsequent discovery of the various boreopterids since then might mean that this should be expanded a little, it won’t be a huge stretch and the major inferences that you can make from an identifiable embryo about ontogeny will still hold up.

Dinosaur egg musings

Dinosaur eggs have featured on here once or twice, but I’ve never done much more than mention them in passing with the odd decent photo. This is at least in part because they don’t normally impinge much in my fields of work and as such, I’ve never learned that much about them in detail so don’t have too much to pass on. Nevertheless, they are worthy of a bit more attention than I have managed in the past and there has been a minor spate of egg based stuff coming out recently.

Most importantly of course, eggs can, on occasion, house fossilised embryos. These of course being exceptionally young animals tend to have some things poorly preserved (like skulls) or completely absent (like ribs), and can look quite different to the adults. Thus, even when you actually have an embryo in the egg, it’s not always entirely clear to which animal it truly belongs. Still, such finds do of course provide incredible information about the developmental biology of dinosaurs and when the species is known, you get the possibility of obtaining a growth series of everything from an unhatched juvenile right the way through to an adult. That’s quite amazing, and quite impossible without eggs.
In some cases we do know quite a lot about eggs and nests. Thanks to the presence of embryos we can tell which eggs were produced by which taxa. The nature of the nests can reveal something about behaviour and biology as well. Some nests seem to have the eggs produced in pairs, this fits with a troodontid known with a pair of eggs inside the body, suggesting that two eggs developed at a time in these dinosaurs and then were laid as a pair (presumably one from each ovary), and of course also suggests that these eggs were laid over a period of time like birds, and not spat out in one go like crocs or turtles.

Understanding such things (which taxa laid which eggs, how they grew and changed, how nests were created or looked after) can provide real information about dinosaur biology that cannot be gained or accurately inferred from other data. Ultimately more complex and interesting data such as the number of eggs produced by a given animal in a season or year, or how many animals nested in a locality at a time providing population data and significantly adding to our understanding of ecology and sociality in these animals. There is more to come, and I look forward to seeing it, even if it may be quite some time away.

Pterosaur embryo

This is a less than perfect photo, but then it is of a poorly painted cast, at an angle, under a spotlight, behind glass and of something rather small and delicate. Even so, it does at least, I hope, show that this is a very small animal surrounded by some kind of round wall and with long of long thing bones lining up inside.

Yes this is one of the only three pterosaur embryos known worldwide. Sadly as often happens with such things we got some Nature papers and then, well not much since. Nearly a decade on there’s no detailed commentary on any of these specimens and that is a real shame. OK, so they are far from the greatest vertebrate embryos going being rather flat and crushed and perhaps the less said about the skulls the better, but still there must be more information in there and it’s been quite a few years now. Here’s hoping anyway.

Dinosaur egg ID

Dinosaur eggs are, sadly, very often for sale as they don’t seem to attract the attention of the law in the way in which bones do (that and the fact that they are obviously easier to fake). But what fascinates me about them is the monotonous regularity with which they are identified as belonging to specific taxa. Quite a few people seem to be under the bizarre impression that you can diagnose the family or even genus of dinosaur that laid an egg based on, well, I’m not sure what, but I’d guess the size and shape.

The truth is of course that to look at, most dinosaur eggs are not really any more diagnostic than those of living birds. Some do have distinctive proportions or textures, but mostly they are much of a muchness, and there seems to be quite a lot of variation present, even within single species. Unless you find an embryo inside (or even the egg inside an adult), a brooding parent on top, or can get a sample under the microscope (and match it up to those for which embryos are known) it’s really quite hard, if not impossible, to tell what might have come out of any given egg. Thus, while we do have vast collections of dinosaur eggs, what actually laid them is, in most cases, a mystery for now at least.

These could be from anything really.

I had the fortune to spend some time with an expert on dinosaur eggs when out in Henan a few years back. After some scrabbling in a very productive egg locality I had fished out something like ten very different looking pieces with a variety of curvatures, thicknesses, and ornamentation on both the inner and outer surfaces. On asking I was told that none of them were diagnostic beyond one that ‘might belong to a theropod’.

More and more work is revealing which eggs likely below with which clades or more specific taxa, but the number of times I have seen a random egg or nest listed as belonging to a ‘sauropod’ or ‘hadrosaur’ or still more unrealistically ‘Tyrannosaurus’, is really quite unnecessary. In the case of people selling eggs it’s obvious that they want to increase the value of the material by putting a familiar name to the specimen, but the implied accuracy is nonsense. A little more depressing, I’ve seen a few museums try to pull off the same thing on eggs they can’t possibly have identified.

While it’s nice to poke fun and incompetent fossil dealers who are passing off illegally acquired material, there is a more general lesson here. For all that we do know about dinosaurs, there is, naturally, quite a bit we still don’t know. There are also areas that are often overlooked or neglected and personally I’d put dinosaur eggs into that category. There is a lot more information that can be gained from these once we can match more of them to their ‘owners’ and this and certainly will reveal more secrets in the future.

Big Mama – nesting dinosaurs

Many readers will probably be familiar with the fact that we do have good evidence for dinosaurs not only making, but also caring for nests, not least because in examples like this one, we actually have an adult dinosaur sitting on a nest of eggs. This is the famous ‘Big Mama’ specimen of an oviraptorosaur (this one is actually a Citipati, not an Oviraptor as is often said) sitting on a large nest of eggs. Actually, that’s not quite true, this is a really brilliantly made cast of the original, but you can barely tell that even from very close up, and regardless it’s still a famous specimen and not that often illustrated, so here it is. Well, after the page break, obviously.

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The egg tunnels of Henan

imgp2822One interesting aspect of the Xixia dinosaur park and museum is that the site actually covers what must have been a dinosaur nesting ground. As with the Zigong Dinosaur Museum which built a museum over the actual fossil layer (and something similar is being constructed in Shandong at the moment) the decision was made to display these in situ and allow visitors to see them as they appear in the rock. However whereas in the case of the former the obvious thing to do was to expose the bones and build a platform over them, here the eggs are deep underground. The solution? Tunnel into the hillside and expose them from below!
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Xixia Museum of Dinosaur Fossil Eggs of China

museumThe dinosaur park described recently acts as the entrance to two buildings, both dealing primarily with dinosaur eggs. I’ll cover this bit (the actual main museum with a horribly convoluted name) quite briefly as there is not much to say about it that has not been said about other museums on here before (oh, do check out the new ‘Museums etc.’ category where I have cobbled together my various museum and zoo reviews and sections on the workings on museums). However there were a few nice touches that are worth talking about and of course the huge collection of eggs.

Continue reading ‘Xixia Museum of Dinosaur Fossil Eggs of China’

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