Trying to Trace the Dinosaur Family Tree

Assessing Taxonomic Relationships Amongst the Dinosauria

Trying to organise Dinosauria into clades or family groups has kept many palaeontologists burning the midnight oil. Unfortunately, unlike extant animals; when it comes to organising the family tree of extinct animals such as dinosaurs, a new fossil find, or some new research into existing specimens can throw everything into confusion.

What were once accepted relationships are often questioned and new fossils provide tantalising glimpses into the true nature of the relationship between different types of prehistoric animal.

Two Great Groups Classified

The two great groups of dinosaurs are the Saurischians (Lizard-hipped Dinosaurs) such as the Sauropods and the Theropods and the Ornithischians (Bird-hipped) examples being the Ornithopods such as Iguanodon and the Ceratopsians such as Triceratops.

Much of the general classification was carried out in the late 19th Century and this can lead to further problems. The Victorian scientists cannot be criticised for their enthusiasm and endeavour, they worked according to the principles and practices of the era and of course their technology was very limited. Often these extinct animals were grouped together and described using comparative anatomical measures, which is fine in itself, but we now have a lot more specimens to study. Even the names for the sub-orders can lead to false assumptions. For example, the Ornithopods were so named as it was thought that the feet and footprints of these type of animals resembled birds. In contrast, the word Theropod means "Beast Foot". However, the common consensus amongst scientists today is that it is some of the Theropods, specifically the Maniraptorans such as Microraptor and Velociraptor who are closely related to true birds (Aves).

A One Hundred and Sixty Million Year Old Puzzle

As our knowledge builds up of the 160 million year long fossil legacy left by these reptiles; a group so diverse that at one extreme tiny members of this family, such as Micropachycephalosaurus could perch in the palm of your hand whilst others such as Seismosaurus could exceed 50 metres in length, scientists are still trying to classify these animals.

With thousands of different genera (and new ones being discovered all the time), it is quite difficult to piece dinosaur evolution together. You can get a good idea from one of the poster exhibits put up by undergraduate students at a recent science seminar which attempted so show the inter-relationships between the main dinosauria family groups. The poster illustrates the complexity of the so-called family tree, as well as the huge amount of inter-relationships.

A New Way to Classify Prehistoric Animals

One interesting viewpoint put forward recently is to re-classify all dinosaurs using our understanding of their relationship to living creatures - the birds. Two main groups of dinosaurs would emerge but not "Lizard-hipped or Bird-hipped" as before but "Non-avian" and "Avian Dinosaurs". If this classification was adopted it would make the family tree look very different and the birds in your garden, penguins, pelicans, kiwis, in fact all birds would be basically classified as dinosaurs.

Article Source: Mike Walley

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