What colour were the dinosaurs?

The discovery that some dinosaurs were feathered rather than the initially-assumed scaly took palaeontology by storm. But the question didn’t end there. We still don’t know the extent to which feathers were found across the dinosaur kingdom. Skin-impressions of some sauropods show hexagonal scales or bony plates, suggesting they were unfeathered, whilst others such as the tyrannosaurus were definitely feathered. And what colour were these scales or feathers? For the most part, we don’t know.

Feathered velociraptor. Matt Martyniuk via Wikipedia Commons

 

Ten Things We Don’t Know about Tyrannosaurs

Tyrannosaurus rex and its closest relatives, the tyrannosaurs, are among the best known and most popular dinosaurs - and yet there is still plenty we don’t know about these fascinating creatures...

Despite its name, we don't know if the T-rex we know as "Sue" was male or female. Dinosaurs aren’t sexually dimorphic, including T. rex; their skeletons provide no clue as to their gender. The only evidence we have of a particular specimen's sex comes from either finding eggs inside of a skeleton, or finding medullary bone in long bones. Medullary bone has been found in only one T. rex so far. Image credit: Heather Paul (CC-BY-ND)

1. What age could T. rex live to?

It's possible to work out how old a tyrannosaur was when it died, by looking at growth rings inside its bones - just like counting the rings of a tree. The oldest T. rex yet examined in this way has been nicknamed Sue, and is on display at the Field Museum. It’s thought that Sue was 28 years old^[1] when it died. Only about a dozen skeletons have been cut up to determine their age, and there are other T. rex’s that look like they might be older than Sue, but haven't had their growth rings counted. This means that we really don’t exactly know the maximum age of T. rex; it's possible that it will turn out to be much more than 28 years once the sample of adults has increased.

2. How were tyrannosaurs related?

Evolutionary trees are diagrams that can be drawn to show how animals are related to each other. Researchers gather data and use this to try to reconstruct the evolutionary history of a group of species - but it isn’t always simple. At the moment there are two versions of the evolutionary tree of tyrannosaurs^[2][3] which differ in which species they include, and where they appear on the tree. As more data is collected, trees produced by different groups of researchers usually become more similar. It is likely that with more time and research we will, eventually, find a history that all of the available data supports. Until then though, how tyrannosaurs evolved remains something we don’t know.

3. What did their eggs, embryos, & hatchlings look like?

Despite the popularity of tyrannosaurs, we don’t know anything about the earliest growth stages of any tyrannosaur species. Currently, there are no skulls or skeletons of embryos or juveniles up to a year old. We don’t even know what a tyrannosaur eggshell looks like - very few embryos have been discovered inside fossilised eggs, which is the only way we could be certain of the species the egg belonged to, so the number of dinosaur species identified in this way is very low. It could be that tyrannosaur eggs have already been collected (among those that currently lack embryonic bones) but we just haven’t realised it yet! Hopefully this situation, at least for eggs and embryos, will change very soon as dinosaur eggs are being discovered all the time in places such as China.

Mass Extinction

Why do we study past biodiversity, and is it applicable to the current 'biodiversity crisis'?

It is no great secret that the Earth is on the brink of a large-scale extinction. The extinction of both species and populations is becoming a major concern in the scientific and policy domains for social, environmental and economic reasons. Although genuinely documented recent species or population extinctions are relatively limited (when compared to the Permian-Triassic mass extinction, in which an estimated 96% of species went kaput, around 252 million years ago), it is extremely likely that any figure is a vast under-estimate of actual extinction rates, as we simply do not have any rigorous estimate for how many species there are currently on this planet.

Marine biodiversity holds some of the most enigmatic
and beautiful forms we currently know. Image Credit: Richard Ling (Wikimedia commons)

Species don't just die out - new species are coming into being all the time, through evolutionary processes. If the rate at which species are becoming extinct is at least 75% higher than the rate at which new species are appearing (speciation), traditionally over a period of 2 million years or so, then palaeontologists call this a "mass extinction". Seeing as this is quite irrelevant to current processes happening in just tens to thousands of years, some would prefer to adapt this definition to something more relevant to modern biodiversity issues.

The IUCN (International Union for Conservation of Nature) have undertaken the most recent and thorough extinction status analysis, but this is limited to only 2.7% of the nearly two million named extant species (species we know to be alive today). This low figure calls into question any claims that we are entering a mass extinction, as the analysis simply doesn't cover enough species for us to be sure it gives a comprehensive picture of what is happening. 

Nevertheless, there are mounting concerns that environmental, ecological, and climatic factors are being perturbed in a way that will be substantially detrimental to global biodiversity, issuing the onset of a new, and 6th, 'biodiversity crisis' or mass extinction.