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Six years of new plesiosaur replicas (2012-2017)

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It is hard to believe that the last time I wrote about plesiosaur toys here was in March 2011, over six years ago (http://plesiosauria.com/news/index.php/new-plesiosaur-replicas-for-2011/). Since then, many more new plesiosaur figures have hit the shelves, well, online stores – you’ll do well to find any of these toys in actual brick and mortar stores. The least I can do at this stage is summarise some of the latest additions to my ever-growing collection of plesiosaur models over the past several years.

Safari Ltd

Safari Ltd have added two plesiosaurs to their Wild Safari line since they released their Liopleurodon in 2010: an Elasmosaurus (2013) and a Kronosaurus (2017). I was grateful for the opportunity to work closely again with the Safari Ltd sculptors as a consultant on these.

CollectA

In 2011 I praised CollectA as a “blossoming company” and the CollectA flower has continued to blossom in subsequent years. They have produced four plesiosaurs, including familiar and obscure taxa, Dolichorhynchops (2012), Pliosaurus (2015), Thalassomedon (2016), and Kronosaurus (2017). The company has a reputation for selecting species other than the usual suspects, and for that I’m glad, we have more than enough Elasmosaurus and Liopleurodon already.

Both Safari Ltd and CollectA released a large Kronosaurus in 2017. This presented picky collectors with a difficult choice since both models are very good. CollectA have also released miniature versions of the ‘Deluxe’ size Pliosaurus and their older standard size Liopleurodon as part of their growing series of tube collections.

Geoworld

2014/2015 saw the release of three plesiosaurians by Geoworld in their Sea Reptiles Collection: Kronosaurus, Liopleurodon and Elasmosaurus. They’re nothing special and pretty bad when it comes to accuracy but still irresistible to completists like me. I unboxed the entire Sea Reptiles Collection on the Dinotoyblog Youtube channel if anyone is interested.

Bullyland presented a single plesiosaurian offering in the last half decade: a Liopleurodon with an articulated jaw in 2016. Good to see the German company still in the picture, at least.

Lastly, to round up the group, De Agostini is a newcomer to the world of plesiosaur toys. The Italian company created some particularly cute plesiosaurians as part of their ‘Dinosaurs and Friends’ children’s book series. A family of Plesiosaurus (mummy, daddy and baby) and a father and son pair of Kronosaurus.

That’s not an exhaustive list but it is more than enough to keep collectors on their toes!

Written by Adam S. Smith

July 23rd, 2017 at 4:19 pm

Investigating plesiosaur swimming using computer simulations

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One of the many areas of controversy in plesiosaur palaeobiology is the topic of how they swam. The question goes back almost 200 years to the 1820s when the first complete plesiosaurs were described from the Jurassic cliffs of Lyme Regis, UK. Plesiosaur swimming is a particularly difficult topic to study for a number of reasons. Plesiosaurs are extinct so there are no modern descendants, they have a unique body plan with no modern analogues, and swimming animals tend not to leave a good trace fossil record. All of this leaves us in a sticky predicament, but there are avenues we can explore to come to a greater understanding of plesiosaur locomotion.

Previous researchers have tried to answer the question of how plesiosaurs swam by conducting detailed osteological analyses, while others have approached it experimentally using robotics, or humans with fabricated paddles. These studies have started to settle on some consensus but there is still some uncertainty. The topic can also be explored experimentally through computer simulation and I was fortunate enough to be involved in such a study in collaboration with colleagues at the Georgia Institute of Technology. Our findings were published today in the open access journal PLOS Computational Biology (Liu et al. 2015).

Meyerasaurus swimming

Rendering of the Meyerasaurus victor plesiosaur model used in the study by Liu et al 2015.

What did we do?

We built a full-size, 3D, virtual plesiosaur, placed it in a simulated fluid, and gave it articulated joints so that it could propel itself through the fluid. We ran thousands of simulations to find the optimal ranges of limb motion and gaits – those that moved the animal forward the furthest. We did so multiple times under different specified parameters to see how different available ranges of joint motion effected the results. To investigate the potential contribution of the different limbs, some of the simulations used all four limbs while others used the forelimbs or hind limbs only. You can check the open access paper for the technical details.

What did we find?

We generated a lot of results in the form of videos. The simulations with the most plausible ranges of motion have a flying stroke with a large up-down component. This is essentially a form of underwater flight similar to penguins and turtles. One of the key questions we wanted to explore was how the forelimbs and hindlimbs moved relative to each other. Our results were inconsistent in this regard, which is significant in itself. The ‘forelimb-only’ simulations are just as fast as simulations using all limbs, which implies that the forelimbs were the powerhouse in plesiosaur swimming while the hindlimbs were more passive, at least during steady cruising.  However, in ‘hindlimb-only’ simulations, where the hind-limbs were asked to do all of the work, the rear flippers flail around a lot but the motion isn’t transferred into thrust or forward motion. Instead, in these simulations the whole plesiosaur rocks around the centre of body mass – apparently a rear-drive plesiosaur is a no-goer. This physical constraint probably explains why no other animals have adopted this unusual body plan, and it also explains why the gait is so variable in our simulations – the hind limbs provide so little thrust during cruising that how they move relative to the forelimbs is irrelevant.

plesiosaur swimming with all four limbs in large range

An example of one of the simulations. This one shows optimal swimming in a simulation of all four limbs using the widest joint range parameters. The parameters in this particular simulation are probably beyond the biologically possible limits of the joints, but other simulations had more conservative ranges (see the paper for all the videos).

 

plesiosaur swimming with all four limbs in large range - tip traces

To help us understand the limb strokes we traced the tips of the limbs. This one shows the limb tip traces for the above simulation, viewed posterolaterally. The hind-limbs in this simulation used only a small proportion of the available range.

 

Out of curiosity (and not included in the paper), we also manually simulated some specific limb strokes as hypothesised by previous plesiosaur researchers: rowing,  figure-of-8 flying, and modified flying. However, none of these manual simulations were as efficient as the best simulations found in our study through optimisation.

Does the method work?

Can we be sure that the method works and how do we know? Without a time machine we can never be completely certain that simulations of extinct organisms are correct. However, we can test the methods by applying them to models of animals for which their swimming is already known. In this case, our method was applied to several modern day animals including a turtle, a fish, and a frog (Tan et al. 2011). In each modern day animal the simulations were consistent with the biological reality, which suggests that the virtual reality is mirroring actual reality. This gives us confidence in our method.

New questions raised

Our simulations may shed light onto some old questions, but they raise new ones. If the hind limbs weren’t used for steady swimming, why are they so similar in shape and size to the forelimbs? Our study focussed entirely on propulsion but not on steering or stability, so we suggest that the hindlimbs may have helped the animal change direction more efficiently. Another alternative is that the rear flippers may not have been used in steady cruising – the sort of swimming our method focussed on – but may have instead been used for sudden short-lived bursts of speed. This sort of behaviour would be unstable over long distances (and so our method would reject it), but the hind flippers may have helped the plesiosaur lunge at prey or avoid a larger predator.

Plesiosaur tip traces

Tip-traces of the most efficient limb strokes resulting from simulations with all four limbs. The top simulation explored a narrow range of available motion, the middle simulation explored a medium range of available motion, and the bottom simulation explored a wide range of available motion (probably exceeding the biological limits of joint motion).

The future

We hope to explore the above questions about the function of the hind limbs in the future. There’s plenty of scope for other related studies on different plesiosaurs or other extinct swimming animals. For example, we selected a plesiosaur with a generalised morphotype for this study, but plesiosaurs as a group are highly variable. We’d like to look at some of the more extreme morphotypes in the future, the long-necked elasmosaurids and short-necked pliosaurids, to see how the proportions of the body impact the simulations. We also focussed all of our attention (and computing power) on how the limbs move, because that was our main focus. However, we acknowledge that the tail and neck may also have been important in locomotion. This is something else we hope to explore in the future. In the meantime, every journey must start with a first step, or – in this case – a first flap.

Liu S, Smith AS, Gu Y, Tan J, Liu CK, Turk G. (2015) Computer Simulations Imply Forelimb-Dominated Underwater Flight in Plesiosaurs. PLoS Comput Biol 11(12): e1004605. doi:10.1371/journal.pcbi.1004605

Tan J., Gu Y., Turk G., and Liu C. K. 2011. Articulated swimming creatures. ACM Transactions on Graphics, 30(4), 58:1–58:12.

Written by Adam S. Smith

December 18th, 2015 at 7:42 pm

Why did elasmosaurids have such a long neck?

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It was once common knowledge that elasmosaurid plesiosaurs were bendy-necked beasts that swanned about near the surface, striking snake-like at slippery prey. It is now common knowledge that their necks were relatively rigid rod-like structures, the function of which remains something of a mystery. The truth, with regard to flexibility at least, is probably somewhere in between. The most recent study to provide estimates of flexibility in elasmosaurid necks gives ranges of motion in the region of 75–177° ventral, 87–155° dorsal, and 94–176° lateral, depending upon the thickness of cartilage present between adjacent vertebrae (Zammit et al. 2008). Visually, that looks something like this:

Elasmosaurid neck flexibility

Ranges of elasmosaurid neck motion as estimated by Zammit et al. 2008.

Elasmosaurids weren’t the completely stiff-necked creatures they’re sometimes made out to be — even a tiny amount of flexibility between vertebrae adds up when you have 70+ neck bones. But why did plesiosaurs have such a long neck in the first place? This is a difficult question to answer because 1. plesiosaurs are extinct and left behind no living descendants, and 2. there are no other extant aquatic long-necked organisms to provide analogues. To my knowledge (and correct me if I’m wrong) there are no long-necked fish, cetaceans, sea turtles, or any other long-necked organisms that spend their entire life underwater. At least not to the extent seen in plesiosaurs.

Elasmosaurids were weirdos, but they maintained this long-necked bauplan for 135 million years, so they were successful weirdos. The long neck also evolved independently in different plesiosaur lineages, some cryptoclidids have extremely long necks too, for example. This all indicates a strong selection pressure (or pressures) driving the evolution of the long neck in plesiosaurs, despite the great risk involved in exposing such a delicate part of the anatomy in an ocean filled with super-predators. The long neck was therefore obviously doing something(s) useful. However, we can only really guess what.

Here are the top possible functions for the long neck in elasmosaurids (I’ve ruled out those possibilities that would require flexibility greater than the estimates given above). Some of these ideas are reasonable and have been suggested before, while others are, ahem, unreasonable and quite ridiculous.

1. Stealth device. Fish are stupid. The long neck provided distance between the bulky body of the plesiosaur and the unsuspecting prey.

Elasmosaurid neck function

2. Getting into tight spots. Helpful for hunting in reefs, crevices, and kelp forests.

Elasmosaurid neck function

3. Sexual selection. The equivalent of a peacock’s tail – the longer and more brightly coloured the better.

Elasmosaurid neck function

4. Food storage. Hamsters have cheeks, plesiosaurs had necks. This might not be as ridiculous as it sounds. Leatherback turtles do something similar (despite their incredibly short necks) by having an extended oesophagus that wraps around the stomach. Their prey (usually jellyfish) is held in place in the oesophagus by backwards-pointing projections (papillae) while excess water is expelled. After temporary storage in the oesophagus the morsels are transported to the stomach. Perhaps elasmosaurids were jelly fish specialists too?

Elasmosaurid neck function

5. Bottom feeding. Hunting in soft sediment. I’m not sure how the long neck really helps here – maybe something akin to number 1?

Elasmosaurid neck function

6. A snorkel. An air supply for staying submerged for prolonged periods of time.

Elasmosaurid neck function

7. Surprise, mother flapper!

Elasmosaurid neck function

8. Energy saver. Moving costs energy, so a long neck might allow the plesiosaur to feed, slumped on the sea bed, hardly moving its body in the process.

Elasmosaurid neck function

9. Electrogenic organ. Plesiosaur necks housed electrocytes and so longer necks create higher voltage electric fields. For electrolocation (sensing prey), elecrofishing (stunning prey to be consumed at leisure), and/or electric defence (to protect from pliosaurs and mosasaurs). This hypothesis comes from here, and was raised to my attention by Darren Naish.

Elasmosaurid neck function

10. Wrench of death. Grab and twist – for pulling ammonites out of their shells. Originally suggested here – thanks again to Darren Naish for reminding me. Twist feeding has also been suggested for short necked pliosaurs, for which it makes morse sense to me.

Elasmosaurid neck function

Other suggestions are welcome! Edit – I’ve updated the list with some new suggestions and will add more soon based on the comments posted below…

References

Zammit, M., Daniels, C. B. and Kear, B. 2008. Elasmosaur (Reptilia: Sauropterygia) neck flexibility: Implications for feeding strategies. Comparative Biochemistry and Physiology, Part A, 150, 124–130.

Written by Adam S. Smith

November 23rd, 2014 at 6:28 pm

A new Lyme Regis pliosaur

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Earlier this month I co-authored a poster at SVP 2012 describing a new pliosaur from the Sinemurian of Lyme Regis (Smith and Araújo, 2012). I was unable to attend the conference in person so my collaborator and friend Ricardo Araujo was on hand to present our preliminary findings.

Ricardo Araújo stands proudly next to our poster at SVP 2012. Ricardo is conducting a PhD on plesiosaurs at the Southern Methodist University, Texas.

The spectacular specimen was discovered at Black Ven, Lyme Regis, and was acquired by the Niedersächsisches Landesmuseum, Hanover, where it was expertly prepared in the 1990s by their preparator, Elija Widman. The fossil consists of an almost complete skull and vertebral column.

The Lyme Regis pliosaur as articulated

As explained in our poster, the fossil represents a new taxon that is both stratigraphically and morphologically intermediate between known Hettangian and Toarcian rhomaleosaurid pliosaurs. Which makes perfect sense. A legible (just about) jpg version of the poster is available here or by clicking the small version below, and a PDF of the abstract is available here. This is very much a work in progress though and more of a sneak preview than a final word. We have a paper in prep which will provide a more detailed description of the specimen.

Poster for SVP 2012

References
Smith, A.S. and Araújo, R. 2012. A new rhomaleosaurid pliosaur from the Sinemurian (Lower Jurassic) of Lyme Regis, UK. Program and abstracts, 72nd Annual Meeting of the Society of Vertebrate Paleontology, Supplement to the online Journal of Vertebrate Paleontology, 74. [PDF here]

[Incidentally, how does one cite an SVP abstract correctly these days?]