Skip to main content

Robotic salamander

I know this isn't about dinosaurs but it's more to do with scientific methods in palaeontology. Recently, in the journal Science, there was a paper about a robotic salamander where its gaits are controlled by a spinal cord model. The spinal cord model gives out signals that oscillates the trunk. The team confirmed that the more intense the signal, the higher the frequency of the oscillation gets. This higher frequency oscillation produces a swimming gait similar to that of real salamanders. On top of that, they found that limb oscillation saturates at a lower frequency and the robot switches from walking to swimming.

According to the authors, the main significance of this study is 'to show how a tetrapod locomotion controller can be built on top of a primitive swimming circuit and explain the mechanisms of gait transition, the switch between traveling and standing waves of body undulations, and the coordination between body and limbs'.

This work has been taken up pretty frequently as a possible scenario of evolution of walking gaits from swimming in early tetrapods. Though, I have heard criticisms that since salamanders are derived amphibians, modelling their locomotory switches from swimming to walking does not necessarily show how this might have happened in basal tetrapods. This is true from a certain perspective, like trying to figure out the biomechanics of basal birds (without all the adaptations of flight), using advanced birds (with highly specialised flight adaptations) as models. However, as the authors stated, the significance of this study is that the neural control of walking can be based on a primitive swimming neural control such as those seen in lampreys.

If this isn't convincing, then even from a purely biomechanical point of view, it is still significant in that they provided a good model to understand the locomotory switch from swimming to walking in a modern salamander. If we don't even understand how modern animals work, how are we to understand how extinct animals may have worked.

Originally posted on DinoBase

Comments

Popular posts from this blog

The difference between Lion and Tiger skulls

A quick divergence from my usual dinosaurs, and I shall talk about big cats today. This is because to my greatest delight, I had discovered today a wonderful book. It is called The Felidæ of Rancho La Brea (Merriam and Stock 1932, Carnegie Institution of Washington publication, no. 422). As the title suggests it goes into details of felids from the Rancho La Brea, in particular Smilodon californicus (probably synonymous with S. fatalis ), but also the American Cave Lion, Panthera atrox . The book is full of detailed descriptions, numerous measurements and beautiful figures. However, what really got me excited was, in their description and comparative anatomy of P. atrox , Merriam and Stock (1932) provide identification criteria for the Lion and Tiger, a translation of the one devised by the French palaeontologist Marcelin Boule in 1906. I have forever been looking for a set of rules for identifying lions and tigers and ultimately had to come up with a set of my own with a lot of help

R for beginners and intermediate users 3: plotting with colours

For my third post on my R tutorials for beginners and intermediate users, I shall finally touch on the subject matter that prompted me to start these tutorials - plotting with group structures in colour. If you are familiar with R, then you may have noticed that assigning group structure is not all that straightforward. You can have a dataset that may have a column specifically for group structure such as this: B0 B1 B2 Family Acrocanthosaurus 0.308 -0.00329 3.28E-05 Allosauroidea Allosaurus 0.302 -0.00285 2.04E-05 Allosauroidea Archaeopteryx 0.142 -0.000871 2.98E-06 Aves Bambiraptor 0.182 -0.00161 1.10E-05 Dromaeosauridae Baryonychid 0.189 -0.00238 2.20E-05 Basal_Tetanurae Carcharodontosaurus 0.369 -0.00502 5.82E-05 Allosauroidea Carnotaurus 0.312 -0.00324 2.94E-05 Neoceratosauria Ceratosaurus 0.377 -0.00522 6.07E-05 Neoceratosauria Citipati 0.278 -0.00119 5.08E-06 Ovir

Hind limb proportions do not support the validity of Nanotyrannus

While it was not the main focus of their paper, Persons and Currie (2016) , in a recent paper in Scientific Reports hinted at the possibility of Nanotyrannus lancensis being a valid taxon distinct from Tyrannosaurus rex , using deviations from a regression model of lower leg length on femur length. Similar to encephalisation quotients , Persons and Currie devised a score (cursorial-limb-proportion; CLP) based on the difference between the observed lower leg length and the predicted lower leg length (from a regression model) expressed as a percentage of the observed value. The idea behind this is pretty simple in that if the observed lower leg length value is higher than that predicted for its size (femur length), then that taxon gets a high CLP score. I don't particularly like this sort of data characterisation (a straightforward regression [albeit with phylogeny, e.g. pGLS] would do the job well), but nonetheless, Persons and Currie found that when applied to Nanotyrannus , it