Tuesday, 30 November 2010

Limusaurus, snow and GCSEs

Above; a rather awkward looking moa skeleton labelled as belonging to Dinornis robustus. It turns out to be a sexual variant of Dinornis giganteus, which is the name that takes priority.
Above; the skulls of varioous Moa species (the identity of which is a mystery to me).

Above; the skull of Limusaurus can be seen on the left, the small arm in the center and the pelvis to the right.

I have not been posting much recently due to other enagements such as revision for my GCSE exams. So rather than researching more on the natural wonders of the world I have been memorizing and reading through chemistry and physics text books.

But I have had a lucky break. Due to the snowy weather recently in good old Britannia I have had many days off school to revise for my exams and maybee do a little research (ok a lot of reading was not revision). This post is nothing to do with anything I have been reading about either. It is the unusual and coincidential similarity between the mid Jurassic Ceratosaur Limusaurus from China and the late Pleistocene Ratite birds of New Zeland: the Moas.

The best way to understand how extinct animals lived is to compare them with similar animals in a modern environment. Now of course Moas are not alive today, but they were around much more recently than Limusaurus and as a result we have much better knowledge of them.

The similarities begin in the head. The skull is small. There is a toothless beak on both the upper and lower jaws and the dentaries and upper jaws on both animals curve down towards their tips. The eye socket is large in proportion to the skull and numerous fenestrations are present to save weight.

Postcranial similarities between the two also exist. The neck is long, but longer in the Moa. Both have reduced forelimbs; Limusaurus has atrophied forelimbs with only 2 functional digits, the Moa does not even have a gelnoid socket in its shouler girdle. In contrast the hindlimbs are very well developed. The tibia is considerably longer than the femur.

The key differences between these two animals are the facts that Limusaurus has a tail, the Moa has an unsatisfactory caudal series to say the least and that the feet of the Moa are much larger relative to their size than those present in Limusaurus. This suggests that Limusaurus was a faster runner than the Moa.

One final point is that both are preserved with gastroliths, suggesting that most of the mastication and grinding of food took place in the gizzard.
More on Limusaurus and Moas later on.

1 comment:

  1. Hmm... I recently read about these in Wonderful Life by Gould, real interesting stuff!