What is your first thought when someone mentions the word dinosaur ? Perhaps it is the image of the infamous Diplodocus skeleton which cannot fail to attract your attention on entering the Natural History Museum, London. Maybe thanks to Spielberg’ s Jurassic Park it’s the prospect of the dinosaur of your nightmares the Velociraptor terrorising anything unfortunate enough to cross its path. For me I suppose it’s a mixture of Spielberg’s master class, many trips to natural history museums, hours of being glued to text books and in my younger years playing with many, many toy dinosaurs, rarely a trip out went by without another being added to the collection. And it was recently reading text on some fascinating new discoveries in the world of palaeontology which have provided the inspiration for the core of this latest blog. Such is my passion for the subject that after this I have decided to include a section dedicated to this field in every publication following this. As always I hope you enjoy it.
Reign of the dinosaurs.
Dinosaurs first appeared in the form of Protodinosaurs some 252.3 million years ago after the Permian- Triassic extinction earlier than previously thought recent research has revealed. Tracks found in Poland and spreading across three ecosystems and four million years were discovered close to the village of Stryczowice. The evidence suggests however that these dinosaurs would of likely been smaller than a domestic cat with the largest tracks measuring 40 millimeters. Dinosaurs domination of the planet lasted until the late Cretaceous period 65 million years ago where a mass extinction event paved the way for mammals to assert themselves and begin a new reign of domination.
Characteristics of a dinosaur.
· Dinosaurs are divided into two predominant groups, Saurischian meaning lizard hipped or Ornithischian meaning bird hipped species.
· Erect leg posture as a result of cylindrical femoral head which fitted into a perforated hip socket and a hinge- jointed ankle.
· All species were hind limb dominant.
· Tail in most cases held off the ground.
· Scales present on body which formed a non overlapping mosaic pattern.
· Dinosaurs would often reach sexual maturity before growth had been completed.
Were dinosaurs warm blooded?
In recent years the preconception of dinosaurs being cold blooded like their modern day cousins has been thrown into doubt as a growing list of evidence to the contrary continues to build up.
Dinosaurs it was argued had to have been cold blooded as a result of belonging to the archosaur group the same group in which their close relative the crocodile also belongs . Professor Roger Seymour however in his study Dinosaurs, endothermy and blood pressure, stated that as a result of their long necks, high blood pressure would have been essential to get blood into their long necks. He also added that to successfully control the flow of blood a four chambered heart very much like those found in mammals and birds today would have been required. Seymour also believes that all archosaurs began as warm blooded creatures and crocodiles switched to a cold blooded life style as a result of their sit and wait behaviour.
Counter arguments to the suggestion have included the positioning of sauropod necks. It has been suggested that if their necks remained horizontal there would have been little need for high blood pressure to ensure blood reached the brain.
Inertial homeothermy a system where animals are able to slowly warm up and cool down it has been suggested could have been employed by dinosaurs. It has however been counter argued that not all dinosaurs were large and even large dinosaurs began life small.
Further research from Seymour adds more weight to the warm blooded argument. In 2011 he compared the nutrient foreman – holes in thigh bones where blood is supplied to the bone of mammals and modern day reptiles. His hypothesis was the more active the animal the more blood needed to be supplied. He was proven correct the holes were indeed larger in mammals. He then compared these to dinosaur bones and found surprising results. The nutrient foreman found in dinosaur bones was greater than those found in mammals. This meant dinosaurs must have had to of had a high metabolic rate. Velociraptor and T.rex add further weight to this argument with findings revealing they were capable of top speeds of 38km and 29 km per hour respectively.
A team from the Catalan Institute of Palaeontology have also revealed significant evidence pointing in the direction of dinosaurs being cold blooded when they discovered lag lines on the bones of mammals. Lag lines are caused when environmental conditions are not favourable for growth and energy is instead used for the pure survival of the animal. A similar principle also occurs in trees. As these marks had been found on both dinosaurs and modern day reptiles it had been assumed dinosaurs were cold blooded. The finding of these marks on mammal bones proves this piece of evidence at least cannot be used to support the cold blooded theory.
And so with the list of evidence in favour of proving these creatures to be warm blooded, it would seem unless a finding of equal significance is found to contradict these new revelations, it would seem what we thought we knew about dinosaurs continues to be thrown into doubt.
A long trachea would have enabled long necked dinosaurs it is theorised to transmit low frequency noises over a large distance. It is also thought the nasal passages found in the crests of duck billed dinosaurs known as hadrosaurs would have resonated at low frequencies and as a result may have been able to create low frequency noises.
The preconception of forests reverberating to the sounds of dinosaur vocalisation however could well be proven to be inaccurate. Hadrosaurs for example may have been able to produce low frequency sounds, but scientists are looking to modern day reptiles for answers to how these sounds could have been produced without the need for vocal chords. King cobras are shown as an example for how this could work, they possess soft tissue resonating chambers, capable of amplifying frequencies and consequently making hisses sound like growls. It has been suggested hadrosaurs could have also been capable of this.
And further evidence increases the likelihood of the range of dinosaur vocalisation being limited. Dinosaurs originate from the bird linage of divergence and so it could have been presumed they would possess the same vocal characteristics as birds today. This has been proven to be incorrect however with no evidence of vocal chords in either the earliest birds in the Mesozoic era or in their dinosaur relatives. Dinosaurs may have developed vocal chords independently of birds however there is no clear cut evidence of this. Dr Senter concludes as a result of this evidence that dinosaurs like their modern day relatives would most likely of hissed when disturbed and would have been unable to properly vocalise.
Evidence of dinosaur battles.
Therapod dinosaurs due to the predatory lifestyle they led are likely to be found with evidence of battle wounds. Two Allosaurus skeletons reveal evidence of the hardships of living a predatory lifestyle. One was found with injuries too its ribs, tail, shoulder, feet, toes and serious infections to its foot, finger and a rib. The severity of some of the injuries observed mean it is possible they were a factor in the predators death. In another skeleton an Allosaur tail suffered an injury suspected to be caused by the spike of a stegosaur. A famous Tyrannosaur skeleton named “Sue” revealed serious injuries caused by conflict with another Tyrannosaur and were found to reveal evidence of successful healing.
The fossil record also shows evidence of battles where herbivores successful repelled their attacker. A Triceratops horn was found to have been bitten off by a tyrannosaur however there was evidence of healing which would imply a successful outcome for the herbivore. Sauropod and Hadrosaur remains have also show evidence of healing after encounters with predators. The spikes of Stegosaurs have been found broken and damaged again with evidence of healing confirming these would have been used to fight.
Dinosaur facts bullet points.
· 700 species of dinosaur have been found 100 of those in Britain.
· The largest dinosaur was Argentinosaurus, measuring in at 37 metres from head to tail, it was the length of a Boeing 737. It would have needed up to 100,000 calories per day.
· The infamously small arms of Tyrannosaurus Rex could have either been used for holding prey, or if they had feathers as a courtship display.
· The second toe of the Velociraptor was not used for slicing prey as first thought, instead it was used for gripping and pinning .
· It has been theorised the tail of the Diplodocus may have been used as a weapon.
· The head crest of Cryolophosaurus had the ability to flush blood as a result the colour of the crest would change and would have been used to either warn of danger or sexual availability.
· The longest carnivorous dinosaur is thought to be Spinosaurus it is estimated it could have reached lengths of up to 18 metres.
New species of dinosaurs are discovered with incredible frequency, which makes the thought of what is still out there unknown to us waiting to be found so exciting. Here a new species has within the last few days been discovered in Venezuela.
I really hope you found thisblog of interest, thank you for reading thank you for reading George :)
Science Uncovered - Dinosaurs rediscovered
Dinosaurs a Field Guide