Dinosaurs: What did their size really mean?

Dinosaur skeletons at Melbourne Museum :: Photo by: S. Barker

Is big always better? Is big normal? What can body size tell us about an animal?

These are some of the questions explored in a recent paper about the distribution of body size in dinosaurs. It also looked at whether the huge sizes some reached were common in nature. 

Why should you care whether dinosaurs were bigger more often than other animals? 

There are 3 key points:

1. It can demonstrate how big animals fit into their ecosystem, 
2. what might drive animals to get really big and 
3. what being big means at time of global change.

The researchers trawled through vast amounts of information to collect as many records of body size as possible. As well as dinosaurs, they collected body size information of:

• Birds
• Reptiles
• Amphibians
• Fish
• Terrestrial mammals
• Extinct Cenozoic (65Ma-now) terrestrial mammals
• Extinct pterosaurs

The first 5 were all extant (currently living) species. The two groups of extinct animals were included to make sure there was no bias in the fossil record, just in case we only dig up big bones!

As well as comparing all the various animals, they compared the 3 main types of dinosaurs: 

• Ornithiscian: For example plant eating duckbills, stegosaurs & Triceratops; 
• Sauropodomorphs: The long necked plant eating dinosaurs, for example brachiosaurs, apatosaurs, diplodicus; and 
• Therapoda: Meat eaters, which ultimately evolved into birds, for example T. rex and velociraptors.

Frequency distribution of species body 
size for eight different animal groups: 
(a) extinct dinosaurs; (b) extant birds; (c) extant reptiles; 
(d) extant amphibians; (e) extant fish; (f) extant mammals; 
(g) extinct pterosaurs; and (h) Cenozoic mammals.  O'Gorman & Hone

The scientists also compared dinosaurs found in 2 prolific dinosaur fossil formations, the Morrison formation and Dinosaur Park, and across time periods of the Age of Dinosaurs, the Mesozoic. These comparisons were to make absolutely sure that there were no biases in the results.

All the non-dinosaurian animals showed a higher, or normal, frequency of smaller body size, and so did the Theropods. The herbivorous Ornithischians and Sauropodomorphs however, showed a uniquely high frequency of large size.

The other interesting result was that the dinosaurs got larger more often towards the end of each time period. The Late Triassic, Late Jurassic and Late Cretaceous all see a higher frequency of these massive animals. From this we can speculate that:

1. Times of stability can allow animals to evolve into ginormous size.
2. Being big is not so good when things start to change in your environment. 

So why were the big plant eating dinosaurs so darn big? It appears to be a combination of factors. The first being escape from predators: once you get really big, not much can hurt you. The other factor has to do with processing food. These dinosaurs were eating very tough, nutrient poor, plant material that took a lot of breaking down. As they got bigger, their gastric tract also increased and allowed for more efficient processing of food.

This paper shows that when it comes to size, the dinosaurs were truly unrivaled. No other group of animals has such a high frequency of gigantic size. The large size of the herbivorous dinosaurs was a double edged sword. While it helped them avoid predation and made them fantastic plant processing machines, it left them vulnerable to changes in their environment so that they suffered greatly at each major extinction event they faced. 

It also raises the question: was it the preference for smaller size, that lead to the survival of Therapods in the form of birds?

What do you think? Could the smaller size of Therapods be part of the reason they continue to live successfully today?

Reference: 

O’Gorman EJ, Hone DWE (2012) Body Size Distribution of the Dinosaurs. PLoS ONE 7(12): e51925. doi:10.1371/journal.pone.0051925

Follow up: Did T. rex have feathers?

Sue the T. rex
The largest and one of the most complete T. rex skeletons ever found.
Image Source: Wikipedia

Dear readers, you will never guess what happened!

After I published the previous post 'Did T. rex have feathers?' and posted the link on Twitter I got a response that I hadn't expected.

A tweet from the BBC Earth's Walking With Dinosaurs @walkwithdinos:

"@barkersaur It's *quite* the talking point amongst our Facebook fans... Here's our take though, by Steve Brusatte: http://ow.ly/i3rv7"

If you follow the link you will notice immediately that both our articles begin with... the same picture! Which is amusing, and also a pleasant discovery.

A quick background on Steve Brusatte:

Steve is a vertebrate palaeontologist from Columbia University and the American Museum of Natural History. He is particularly interested in theropod dinosaurs. He has authored many papers and three books. One of which I own, Dinosaur Palaeobiology, edited by the eminent Professor Michael J. Benton. It is the text book on Dinosaurs if you want to get into the nitty gritty details.

Steve's article 'Did T. rex have feathers?' (yes, we chose the same titles too) is well worth reading as it discusses:

• Why fossils with feathers are precious and unique
• Another fossil relative of T. rex that had feathers (Dilong)
• Other dinosaurs that had feathers
• Where T. rex may have had its feathers

I enjoy the way he finishes his article with a hopeful thought:

"Maybe someday we can test this hypothesis by finding a rare fossil of T. rex that was fossilised in that set of perfect conditions for preserving feathers."

Wouldn't that be wonderful? I am not certain if the rock we normally find T. rex fossils in is likely to preserve feathers, but we can dream.

If you put  'feathered t rex' into google images you will enjoy the varied and amazing artistic interpretations!

One of the many interpretations of how T. rex might have looked
Image Source: Deviant Art

How do you picture T. rex? Are feathers too hard to imagine? What colours should T. rex be?

Did T. rex have feathers?

Can you imagine Tyrannosaurus rex with feathers? Because that’s what research suggests may be the case.

(Image Source IFLS )

In my last post ’Why Palaeontology?’ I stated one of the most significant findings of Palaeontology in the last 50 years was confirmation that birds are descended from therapod (meat eating, three toed) dinosaurs.

There are many similarities between therapod dinosaurs and birds.  Most of these similarities are anatomical, including:

• a wishbone (fused collar bones)
• three toed foot
• three fingered hand
• a half moon shaped wrist bone
• hollow bones
• and feathers.

Feathers are the most spectacular similarity that dinosaurs share with birds. The first time they were seen together was with the discovery of Archaeopteryx. It wasn't until the 1990's that more feathered fossils were found, in China. Hundreds more.

The Tyrannosaur family tree - Yutyrannus huali is the
largest of these found with feathers
(Image source Xing Xu et al.)

Some of the Chinese feathered dinosaurs knocked Archaeopteryx off its perch as the oldest feathered dinosaur. A study in 2012 looked closely at dating some of China’s earliest feathered dinosaur fossils. It concluded that many were present 161 million years ago, which is around 10-20 million years older than Archaeopteryx.

Feathered dinosaurs are usually small. Archaeopteryx was about the size of a crow. In 2012, however, a paper was published by Nature that described a huge feathered dinosaur, a distant ancestor of the iconic Tyrannosaurus rex, Yutyrannus huali.

Yutyrannus huali was over 9m long and roughly the same weight as a medium sized car. Yutyrannus huali had feathers when it was an adult. This is strong evidence that the infamous Tyrannosaurus rex may have also sported feathers as an adult. Over 6000kg of feathered killing machine. 

Despite this evidence artistic depictions and toys of T. rex seem slow to adopt the new feathery covering. I quite enjoy the idea of the giant meat-eater being covered in feathers, how about you?



Science Ruined Dinosaurs cartoon pictured can also be purchased as a T-shirt.

For further reading and images try the Wired Science article Giant Feathered Tyrannosaur From China.

Why Palaeontology?

What if you understood all the changes in the natural world, just because you looked at rocks and unlocked their secrets?

Last year I decided to change careers and become a Palaeontologist. My father has a PhD in Geology, and was an avid fossil collector in his youth, so some of his passion for rocks may have rubbed off!

Since the early 60’s, when Dad was studying, there have been some dramatic changes in Palaeontology, inlcuding:

• A name change to ‘Palaeobiology’
• 100's of  feathered fossils discovered in China in the 1990's
• The confirmation that Birds are descended from Dinosaurs (Willis)
• Proteins have been removed from fossils (Lester, 2007)
• A protein responsible for colour was found in fossil feathers (Zhang et al. 2010)
• The discovery that DNA will only last about 6.8 Million years (Barras, 2012)
• The sex of some fossils has been confirmed (Chinsamy et al. 2012)
• 65 Million years ago an asteroid wiped out the Dinosaurs, quickly. (Klotz, 2013)

It took over 100 years before scientists confirmed
that birds were dinosaur decendents (image source)

These changes and discoveries mean we are better equipped to reconstruct, and understand, ancient organisms and their environments. Although, I know some of you deplore the thought of a ‘fluffy’, feathered, T. rex!

If you study Palaeobiology you will be familiar with being asked, “Why are you studying that?” in a somewhat sceptical tone. Palaeobiology PhD student Sarah Werning recently explored this in her article ‘Why Palaeontology is Relevant’.

No doubt you recognise, several of what Sarah refers to as ‘public-friendly’ responses:

• “Paleontologists teach anatomy at many medical schools.”
• “Fossils play an important role in oil discovery.”
• “Paleontology is a good ‘gateway drug’ to the other sciences.”
• “Paleontology is a good way to teach critical thinking skills.”
• “Paleontology is inherently interesting; it doesn’t need further justification.”  (Werning, 2013)

Unfortunately, none of these reasons explain why Palaeontology is important. Reading Sarah’s article I realised my responses have changed over time. Instead of using one of the ‘public-friendly’ reasons, I now talk about Palaeobiology in terms of understanding ancient life so we can better understand life today. For example:

• “Knowing what happened to living things when it got hotter or colder in the past, we can understand the effects of climate change today.”
• “We can gain greater insights into how evolution works.”
• “The current rate of extinction can be calculated after studying past mass extinctions.”

The extinction of non-avian Dinosaurs had a big impact 
on the evolution of mammals, including humans. (image source)

Palaeobiology is not limited to a science that lists everything that came before us, it puts those organisms into context. It is the context that is important.

Palaeontology is becoming increasingly relevant. The key to the future of life and the earth is locked up in the rocks, all we need to do is decode it. Like most sciences, it is constantly evolving and being built upon. The changes and discoveries,  since the 1960’s, mean we can understand our past and present better than ever before.

What other ways do you think Palaeontology has changed, or is relevant?

You can read Sarah Werning's article at Plos Blogs http://blogs.plos.org/paleo/2013/02/19/why-paleontology-is-relevant/

Other references:

Willis, P. abc.net.au, Dinosaurs and Birds The Story

Chinsamy et al. 2012. Nature Communications 4: 1381

Lester, B. 2007. Cosmos Online, Protein extracted from T. rex fossil

Zhang et al. 2010. Nature 463: 1075-1078

Barras, C. 2012. New Scientist: Life, DNA's half-life identified using fossil bone

Klotz, I. 2013. Reuters, Asteroid may have klled dinosaurs quicker than scientists thought

Connective Tissue: keeping us together

Connective tissue is incredibly important to all of us. Not only does it form our solid inner structure, it pads us to protect us, it cushions our joints and forms our blood. The classification of blood as a connective tissue seems a bit counter-intuitive, however, all types of blood cells originate in the connective tissue of our bone marrow, some white blood cells move freely between blood and other connective tissues and the chemical composition of blood plasma (plasma is what you get when you remove all the cells from blood) is very similar to that of the fluid that occupies the space between our tissues and skin (known as the interstitial space). 

Connective tissue is one of the four main body tissues. The others are nervous, muscular and epithelial (epithelial tissue lines surfaces, including the epidermal layer of our skin). Connective tissue is then broken down into different types:

Ordinary/Specialised

Loose/Dense

Regular/Irregular

I won’t go right into the details of each of these here, except to explain Ordinary and Specialised as they are the ones I am most focussed on. Ordinary connective tissue is your everyday garden variety connective tissue. It is comprised of extracellular fibres, extracellular fluid known as ground substance (I will explain more about this later), and cells, all in relative proportions.

Within the ordinary connective tissue classification there occurs some very different forms of specialised connective tissue. Examples include bone, cartilage and lymphoid tissue (lymph nodes, spleen, tonsils, bone marrow, etc.). I will probably write an article on the Lymphatic system and its tissues down the track, as it is also a pet subject of mine.

The term ‘connective tissue’ is often used to refer to just the ordinary type, and this is the connective tissue I have most experience with. Ordinary connective tissue includes: the superficial and deep fascial sheaths, nerve and muscle sheaths, the supporting framework of internal organs, aponeuroses (layers of broad flat tendons, we have aponeuroses over our skull, in our abdomen and also our lower back), ligaments, joint capsules, periosteum (a layer of tissue around our bones) and tendons. Unfortunately our knowledge of these has been gathered somewhat slower than our other more exciting body parts, as Anatomists had a habit of cutting connective tissue away to get to muscles, organs and blood vessels. During the time I worked as a Remedial Massage Therapist and Teacher there seemed to be a push forward with knowledge and research of connective tissue. One particular pioneer in soft tissue treatment was Biochemist Ida Rolf, who developed a treatment method now commonly referred to as ‘Rolfing’ but which was actually named ‘Structural Integration’. Many students of this treatment method have gone on to develop their own theories and treatment methods, notably Tom Meyers who has authored several books and developed the theory of Anatomy Trains. For more info on Tom click through to his website here. As an aside, one of the stranger moments of my career was when a patient rang the practice I was working at and asked if someone could ‘Rolf’ his groin. No one at the practice knew about Rolfing so it created a great deal of confusion and, I must admit, giggling.

The white sections in this image from Grey's Anatomy are all connective tissue - fascia. The fascia that envelops our 'six pack',  properly known as Rectus abdominus is called the Linea alba (white line)

What is fascia?

Fascia is a specialised type of connective tissue. It surrounds supports and protects all the visceral and bodily structures. Fascia provides insulation, padding and the pathway for nerves, blood and lymphatic vessels; it stores water and fat, and allows the skin and underlying structures to move independently of one another.

Fascia can be viewed as a large, complex, body-wide net, or web. (T. Myers), Grey’s anatomy refers this as the ‘extracellular matrix’ (ECM). The fascial web or ECM is composed of three types of fibre: collagen, elastin and reticulin, and ground substance.

• Collagen: is the most common and tensile/least elastic of the three fibres and is found in fascia, bones, tendons and ligaments.
• Elastin: as the name suggests is more elastic and is found mostly in the lining of arteries.
• Reticulin: is the most elastic of the three fibres and is found in the supporting structures surrounding the glands and lymph nodes.
• Ground substance: a viscous gel-like substance which acts like a mechanical barrier to foreign matter and is a medium for the diffusion of nutrients and waste products. It can change its state to meet local needs e.g. in a still area of the body it will become more gel-like to receive and store metabolites and toxins. Small amounts of ground substance are found throughout every tissue, but the synovial fluid in joints and the aqueous humour of the eye are examples of areas where it can be observed in large quantities.

Collagen fibrils from inside a knee sourced from here

Due to the fact that the fibres in fascia run in all directions it is able to move in all directions to allow for changes in muscle bulk and for stretching. Fascia shrinks when it is inflamed. It is also slow to heal because of poor blood supply and is a focus of pain because of its rich nerve supply.

A useful metaphor is viewing the body like a tent, our bones as tent poles which cannot support the structure of the body without guy ropes (the fascia), to keep just the right amount of tension to allow the tent (or body) to remain upright with proper equilibrium!

The superficial and deep fascial sheaths:

Superficial fascia 

Superficial fascia is subcutaneous and blends with the bottom layer of the dermis. It is comprised of loose connective tissue and adipose tissue and is the layer that primarily determines the shape of our body. Superficial fascia is also found surrounding organs, glands, neurovascular bundles and stores fat and water. It also acts as a passageway for lymph, nerve and blood vessels and as a protective padding to cushion and insulate.

Deep fascia

Deep fascia is a dense fibrous connective tissue which interpenetrates and surrounds muscles, bones, nerves and blood vessels. It also functions as a connection and 

communication system in the form of aponeuroses, ligaments, tendons, retinacula, joint capsules and septa. The deep fascia envelops the bones (periosteum and endosteum); cartilage (perichondrium), and blood vessels (tunica externa) and becomes specialised in muscles (epimysium, perimysium and endomysium) and nerves (epineurium, perineurium and endoneurium). Its high concentration of collagen fibres gives the deep fascia great strength and integrity.

Scar tissue

Scar tissue is the most common form of connective tissue used by the body to help repair or replace damaged areas. Scar tissue is generally less flexible than the tissue it replaces. When scar tissue forms, often more tissue than necessary is created, and adhesions (fibrous bands) form. After the acute phase of an injury connective tissue massage can be beneficial. Indeed, this was something I did a lot in my practice. From around twelve weeks on a scar can be treated with Myofascial release - a gentle stretching technique designed to align the fibres and mobilise the fascia. It worked incredibly well with patients who had had a mastectomy and found the scar was pulling into their armpit or across where the breast had been.

Adhesions

When an area of the body is immobile (through injury, underuse or decreased use) lubrication between the collagen fibres is not maintained, the ground substance changes and adjacent collagen fibres move closer together, this is the beginning of microadhesions. Microadhesions are responsible for restricted joint movement, not only a loss in range of motion, but also a reduction in the quality of the movement of the joint. Immobility leads to stiffness, and stiffness leads to more stiffness! (So keep moving!)

Thixotropy

Connective tissue fascia is Thixotropic! It can be transformed from a more solid state (gel) to a more liquid state (sol) with the application of a gentle shearing force.

“Thixotropy Definition: The property of a material which enables it to stiffen or thicken on a relatively short time upon standing but upon agitation or manipulation to change to a very soft consistency or a high viscosity fluid; a reversible process. The materials are gel-like at rest but fluid when agitated and have high static shear strength and low dynamic shear strength, at the same time.”  (Dictionary of Composite Materials Technology,
Stuart M. Lee)

Examples of thixotropic materials are silly putty and a solution of cornstarch and water. (Seriously, try it! Just don’t whack it too hard or you might hurt your hand!)

This becomes important when you are having your fascia massaged. A lot of therapists work on the theory that getting in ‘hard and deep’ is the only way to correct areas of tension. However, if you apply a large amount of direct force at a thixotropic substance it will resist and behave like a solid. So in actual fact, if you are trying to improve mobility in an area that has tightened, applying gentle shearing force, or vibration, will allow you to manipulate and stretch the fascia, potentially reducing adhesions, and restoring a greater range of movement for that area. It also allows you to move past the fascia and contact the muscle underneath for further treatment.

Conditions which affect connective tissue

Ehlers Danlos Syndrome is a genetic condition that affects connective tissue. Usually it is an issue with Collagen producing genes, which can manifest as hypermobility of joints, thinly walled veins and arteries, super stretchy skin, and a whole other range of symptoms. There are many conditions that affect connective tissue, Lupus and Rheumatoid Arthritis are both immune system diseases where the body starts viewing connective tissue as ‘non-self’ and starts attacking it. There are other genetic conditions such as Marfan’s Syndrome, which famously the Pharaoh Tutankhamen had. Because connective tissue is so very important in how the body operates these conditions can be devastating and sometimes fatal. I consider myself lucky in that regard, I just have extra stretchy Ordinary connective tissue, and no obvious vascular/heart problems (although I bruise ridiculously easily).

I hope this brief overview has given you a greater appreciation for our amazing connective tissue, and perhaps you will give more thought to your connective tissue, the guy ropes and bones and sheaths. We simply couldn’t exist without it.

NB. This blog post stems from part of the course notes I composed while teaching the Diploma of Remedial Massage in 2009. I decided to share them firstly as part of a promise to my friends and fellow connective tissue ‘zebras’ at EDSAUS - a site for Ehlers Danlos Support in Australia, secondly my original plan for this Blog was to include posts on anatomy, and this seemed like a useful topic. If you have any questions about this post, please leave a comment :)

The Start of a New Journey

Usually going to the letterbox is not the highlight of my day, today it was. If you have been following this blog from the beginning you may be aware that a short while ago I decided to apply for university. I had spoken to someone in the Distance Ed unit at Macquarie Uni not long after I sent in my application, and she told me I should find out before the end of November. I was starting to get a little nervous, it was almost the end of November and I had heard nothing more. I heard the posties bike stop, and then chug off and I meandered out to see what had come. There were two large envelopes stuffed into the top of the letterbox, the first one I pulled out was my Australasian Lymphology Association magazine, but the second one was from Macquarie University. I ripped through the envelope like a child opens a present, and there it was, an acceptance letter!

I don't mind admitting that I yelled out 'YES!' at the top of my lungs, and there may have been some fist pumping or other wild gesticulations (flailing). I rang my husband to tell him and then my parents. Everyone was pleased and congratulatory. I also posted some very excited exclamations to Twitter and Facebook and all my friends were so positive, it was very lovely to share my happiness in real time!  So there it is, I have some paperwork to fill out and return and then it begins. I will no doubt blog about my experiences, to create a journal I can look back on, and also to share with you what it is like to study science via distance, that way we can all learn something!

Hypermobile bits and pieces

Today I posted a number of pictures of my hypermobile hands on facebook and twitter. They aren't the only part of me that is hypermobile, but they are the easiest to get good photos of.

I mentioned in my first post on this blog that I have a genetic condition which affects the production of collagen in my body. I don't know which particular gene/s are affected, this would take a lot of tests and a huge amount of money. 

As a result of this condition I can do all sorts of weird 'party tricks', and it is one reason I was such a good bellydancer as a teenager. Hypermobility can be a blessing, and also a curse. Being hypermobile is not that uncommon, and many talented dancers and gymnasts find being very flexible can come in quite handy. There are, however, a number of genetic conditions which feature hypermobility as a symptom, these include Ehlers Danlos Syndrome and Sticklers Syndrome. Having one of these conditions means being at risk of more serious complications such as heart troubles, deafness, sight problems, easy bleeding/bruising, healing poorly from cuts, strange scar formation, dislocation of joints, subluxation of joints (not a full dislocation but the joint is out of its correct position), increased risk of injury, pain and muscle dysfunction. 

I am lucky, my aorta is fine, my hearing is good, and I don't have serious dislocations. Unfortunately my joints do move out of position at the flap of a butterflies wings, I heal poorly from cuts and have odd stretched out looking scars, pain and muscle dysfunction.

Most of these complaints can be managed, with splints/braces/strapping, exercises targeted to improve muscle function, pain medication, pacing of activity and avoiding things that put my joints into compromising positions, particularly repetitively. 

According to one geneticist I had a video conference with I do not fit into one particular category, but seem to have a mixture of signs and symptoms of a few collagen disorders.

I believe from my own research that I fall more closely into the category that includes Ehlers Danlos Syndrome Hypermobility Type. I am a member of the EDS australian forum where we bendy bods share information, support each other and have a good vent when things get too difficult.

If you know someone who is hypermobile, particularly a child that appears to be having trouble, read up on hypermobility syndrome and EDS. It is often not diagnosed properly, but diagnosis could save that person a lot of awkwardness and improve their quality of life.

Here are some crazy pictures of my bendy hands: