Long-Necked Dinosaurs - Did Sauropods Hold Their Heads Up High?The Debate Continues
The debate over the posture of the Sauropodomorphs has been opened up again with a new research paper published by a team of scientists from the University of Portsmouth, England.
Sauropodomorpha is the correct taxonomic name for a Sub-Order of the Superorder Dinosauria.
It contains the long-necked herbivores with lizard-like feet such as the Diplodocids and Brachiosaurs.
It was one of two general clades from the Order Saurischia (lizard-hipped dinosaurs).
This particular group of dinosaurs includes some very well known genera such as Diplodocus, Apatosaurus, and Barosaurus.
Most young children will be familiar with these elephantine creatures, with their long necks and long tails.
These animals (also termed Sauropods) are believed by scientists to be the largest land animals in the fossil record.
Once again, most young children can tell you at least one or two items of information about these particular dinosaurs.
For example, when we visit schools the enormous dimensions of some of these animals are frequently recited to us by enthusiastic dinosaur fans.
It is true that many of these Mesozoic monsters could have reached lengths in excess of 30 metres and weighed upwards of fifty tonnes or more, but despite their fossilised bones dominating the vestibules and grand halls of many a museum, palaeontologists know surprisingly little about their posture.
In the late 1980s and 1990s many a large Sauropod exhibit was re-mounted in a different pose as scientists concluded that in most case the tails of these animals did not drag on the ground.
The accepted consensus at present is that most of the Sauropods held their tails straight out behind them, this explains why the Diplodocus (Diplodocus carnegiei) that dominates the entrance to the Natural History Museum in London had to be reassembled in 1994.
However, the debate over the posture and head position of the Sauropodomorphs has been opened up again with the new paper from the University of Portsmouth team.
Just when we thought the back ends were sorted so differing opinions as to the flexibility and natural position of Sauropod necks have risen up again (no pun intended).
The University of Portsmouth team, led by Dr.
Mike Taylor compared the cervical vertebrae (neck bones) of a number of Sauropods with mammals and birds that are alive today (extant species).
By examining the skeletons and muscle structure of living animals which share the dinosaur's upright stance (mammals and birds), the researchers have concluded that the long-necked dinosaurs may have held their heads higher than previously thought, for much of the time.
This study is in contrast to earlier work (published this year), from the University of Adelaide, led by evolutionary biologist Dr.
Roger Seymour.
In this research paper, the swan-like neck pose of Sauropods was refuted.
It was calculated that these reptiles were not capable of maintaining a high enough blood pressure to permit blood circulation from the heart to the brain.
The pressure required to drive blood fifteen of so metres vertically upwards to reach the heads of the largest Sauropods would, it was calculated, be nearly fatal.
The accepted doctrine is that Sauropods held their heads relatively in line with their shoulders and they were unable to maintain a head held in a more vertical position.
The range of movement in the neck of a dinosaur such as an Apatosaurus was believed to be quite constrained permitting the lifting of the neck only a few tens of degrees from the horizontal.
Dr.
Taylor and his team used X-rays and other sophisticated techniques to plot the movement range capabilities of the necks of several Sauropods.
Based on this study, the team concluded that Sauropods could have held their heads in a more vertically inclined position, similar to the way that mammals such as ourselves do.
The problem is, with the lack of preserved soft-tissue such as tendons and muscle in the Sauropod fossil record it is difficult to interpret the articulation and movement of the fossilised bones in isolation.
The public can be lulled into a sense of thinking that scientists know all there is to know about dinosaurs, this is far from the truth.
Even some of the best known dinosaurs, the ones generated by CGI for the movies, still refuse to yield their secrets and the debate over the posture of these huge dinosaurs is set to continue.
One of the drawbacks of using extant species to study dinosaurs, is that no animals today are really comparable with these leviathans from the Age of Reptiles.
Perhaps a more complete specimen will be found soon, one that has elements of soft tissue preservation that may shed more light on the mystery of how Sauropods held their heads.
The history of palaeontology shows that a number of contrasting theories regarding the posture of Sauropods have held sway in the past, it looks like that for the immediate future the debate over the position of the heads of long-necked dinosaurs is set to continue.
Sauropodomorpha is the correct taxonomic name for a Sub-Order of the Superorder Dinosauria.
It contains the long-necked herbivores with lizard-like feet such as the Diplodocids and Brachiosaurs.
It was one of two general clades from the Order Saurischia (lizard-hipped dinosaurs).
This particular group of dinosaurs includes some very well known genera such as Diplodocus, Apatosaurus, and Barosaurus.
Most young children will be familiar with these elephantine creatures, with their long necks and long tails.
These animals (also termed Sauropods) are believed by scientists to be the largest land animals in the fossil record.
Once again, most young children can tell you at least one or two items of information about these particular dinosaurs.
For example, when we visit schools the enormous dimensions of some of these animals are frequently recited to us by enthusiastic dinosaur fans.
It is true that many of these Mesozoic monsters could have reached lengths in excess of 30 metres and weighed upwards of fifty tonnes or more, but despite their fossilised bones dominating the vestibules and grand halls of many a museum, palaeontologists know surprisingly little about their posture.
In the late 1980s and 1990s many a large Sauropod exhibit was re-mounted in a different pose as scientists concluded that in most case the tails of these animals did not drag on the ground.
The accepted consensus at present is that most of the Sauropods held their tails straight out behind them, this explains why the Diplodocus (Diplodocus carnegiei) that dominates the entrance to the Natural History Museum in London had to be reassembled in 1994.
However, the debate over the posture and head position of the Sauropodomorphs has been opened up again with the new paper from the University of Portsmouth team.
Just when we thought the back ends were sorted so differing opinions as to the flexibility and natural position of Sauropod necks have risen up again (no pun intended).
The University of Portsmouth team, led by Dr.
Mike Taylor compared the cervical vertebrae (neck bones) of a number of Sauropods with mammals and birds that are alive today (extant species).
By examining the skeletons and muscle structure of living animals which share the dinosaur's upright stance (mammals and birds), the researchers have concluded that the long-necked dinosaurs may have held their heads higher than previously thought, for much of the time.
This study is in contrast to earlier work (published this year), from the University of Adelaide, led by evolutionary biologist Dr.
Roger Seymour.
In this research paper, the swan-like neck pose of Sauropods was refuted.
It was calculated that these reptiles were not capable of maintaining a high enough blood pressure to permit blood circulation from the heart to the brain.
The pressure required to drive blood fifteen of so metres vertically upwards to reach the heads of the largest Sauropods would, it was calculated, be nearly fatal.
The accepted doctrine is that Sauropods held their heads relatively in line with their shoulders and they were unable to maintain a head held in a more vertical position.
The range of movement in the neck of a dinosaur such as an Apatosaurus was believed to be quite constrained permitting the lifting of the neck only a few tens of degrees from the horizontal.
Dr.
Taylor and his team used X-rays and other sophisticated techniques to plot the movement range capabilities of the necks of several Sauropods.
Based on this study, the team concluded that Sauropods could have held their heads in a more vertically inclined position, similar to the way that mammals such as ourselves do.
The problem is, with the lack of preserved soft-tissue such as tendons and muscle in the Sauropod fossil record it is difficult to interpret the articulation and movement of the fossilised bones in isolation.
The public can be lulled into a sense of thinking that scientists know all there is to know about dinosaurs, this is far from the truth.
Even some of the best known dinosaurs, the ones generated by CGI for the movies, still refuse to yield their secrets and the debate over the posture of these huge dinosaurs is set to continue.
One of the drawbacks of using extant species to study dinosaurs, is that no animals today are really comparable with these leviathans from the Age of Reptiles.
Perhaps a more complete specimen will be found soon, one that has elements of soft tissue preservation that may shed more light on the mystery of how Sauropods held their heads.
The history of palaeontology shows that a number of contrasting theories regarding the posture of Sauropods have held sway in the past, it looks like that for the immediate future the debate over the position of the heads of long-necked dinosaurs is set to continue.
