Guide to Technical Terms

Science is often inaccessible because of the complex terminology we use to capture big ideas. Below are definitions of some common terms you’ll find on my page. If you think of any more I should add, contact me to let me know!

Dinosaur: Dinosaur is the term used to describe members of the group Dinosauria. They are characterized by an upright stance, with legs below their bodies (among many other things). Not all ancient reptiles are dinosaurs, and not all dinosaurs are ancient reptiles (modern birds are considered dinosaurs).

Theropod: A theropod is a member of the dinosaur group Theropoda. These include all of the meat eating dinosaurs, the common ancestor of them, and all of the descendants of that common ancestor (including some as-yet-undiscovered groups). Most, if not all, are bipedal (they walk on two legs). Theropods are the lineage of dinosaurs that are ancestors of modern birds.

Oviraptorosaur: This is a group of theropod dinosaurs that are the current focus of my research. They are feathered, have shortened faces, and most of them have lost their teeth and developed a bird-like beak. They are typically divided into four groups: Caudipterygids, Avimimids, Caenagnathids, and Oviraptorids. To understand these groups, you will need to understand a bit about how we describe groups.

Phylogenetics/phylogeny: the study of relationships of animals. We summarize these hypothesized relationships in a tree diagram called a phylogeny.

Taxon/Taxa: These are catch-all terms that we use to refer to a group of any size. Taxon is singular (i.e. one such group), and taxa is plural (i.e. multiple groups). For example, if I wanted to refer to a single species, a single family, or a single order, I could call it a taxon. If I wanted to refer to to multiple species, multiple families, or multiple orders, I would call them taxa.

Tree: A tree is an image that shows the relationship between a group of animals. These are the bread and butter of phylogenetics. Each taxon is represented by a branch, and where these branches unite (called a node), this indicates that two taxa share a common ancestor there. There are many names for trees depending on what information is shown, but I will try to refer to them simply as ‘trees’.

Basal/Derived: These are terms used to describe the position of a taxon on a tree. These terms are relative, which means that depending on what you’re looking at, a taxon could be either basal or derived. In general, a basal taxon is one that lies close to the base of the tree, whereas a derived taxon is one that is closer to the tip of the tree. This is a gross oversimplification, but should capture most situations.

Sister taxa: Sister taxa are two taxa that are more closely related to each other than to any other taxon in the tree. This means that they share a node with each other that they don’t share with any other taxa.

Caudipterygids: Caudipterygids are basal oviraptorosaurs (that is, close to the base of the tree and therefore the ancestry of all oviraptorosaurs). They were some of the first dinosaurs to be found with feathers, and most still retain small teeth.

Avimimids: Avimimids are a small group of oviraptorosaurs with currently only two species. We separate them into a separate group because they are distinctive and very bird-like.

Caenagnathids: caenagnathids are one of the two most derived groups of oviraptorosaurs. They are sister taxa with oviraptorids. They range in body size from very small (3 kg) to very large (2500 kg). They have completely lost their teeth, and instead they have beaks. They were probably omnivores (ate both plants and meat), and they had long legs, long arms, and short tails.

Oviraptorids: oviraptorids are one of the two most derived groups of oviraptorosaurs. They are sister taxa with caenagnathids. They often had crests made of bone on top of their heads, which have shortened faces and deep, parrot-like beaks. They had short arms and legs, and some had a tendency to develop an enlarged thumb.

Articulated: we use this term to describe a fossil where all of the parts are where they would have been in life. For a skeleton, this means that all of the bones are still connected and in the same position as when the animal was alive.

Disarticulated: this is when the parts of a fossil are jumbled up, and no longer in the same position as in life. For a skeleton, this means that some or all of the bones have become disconnected and moved.

Bonebed: an accumulation of fossils from multiple individuals. These can be either one species or many species. Where the fossils are small, we call the site a microsite. Usually, the bones are disarticulated, but sometimes we get lucky and find bonebeds of articulated skeletons.

Holotype: when scientists discover and name a new animal or plant, they have to designate a single individual or specimen to represent that species forever (no pressure…). That specimen is called the holotype. When we look to see if another specimen belongs to that species, we compare it to the holotype.

Histology: the study of tissues. For fossils, this usually means the study of the microstructure of fossilized bones or teeth. As skeletal tissues grow, they lay down incremental markings that create a record of time within the bones. Palaeohistologists use these to understand the way that the skeleton grew over time.