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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?]

New plesiosaurs, lots of new plesiosaurs!

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There was a time when I’d leap into tippy-tappy action at the first sniff of a newly named plesiosaur. Unfortunately, I haven’t been keeping Plesiosaur Bites up to date and a few new taxa have passed me by. Of course, when I say “a few”, what I really mean is we are swamped by the things. Little wonder I haven’t been able to keep up.

A few years ago I plotted a graph in my PhD thesis (Smith, 2007, Figure 2.2.) to show the number of valid plesiosaur species and genera named in successive 20-year time intervals since 1821 (when the first plesiosaur was named [Plesiosaurus]). The data ended in 2007, the year I submitted my thesis, but showed that new taxa were being erected at a relatively steady rate throughout the 19th and 20th century (Figure 1). The rate started to pick up during the 1990s and I extrapolated the data into 2008-2020 based on the first seven years of the 21st century. I predicted 30 new genera in the period 2001-2020, which would represent a huge post-2001 leap in the number of new valid plesiosaurs. Well, so much for my crude calculations. It’s only 2012 and my ‘huge’ prediction has already been surpassed.

New plesiosaur taxa

Figure 1. Tally of the number of new plesiosaur taxa per 20-year interval (from Smith, 2007, Y-axis adjusted for direct comparison with Figure 2 below). 2001-2020 predicted based on 2001-2007 data.

An adjusted prediction for 2001-2020 based on the average rate of new taxa from 2001-2012 is actually pretty staggering (Figure 2).  62 new species and 51 new genera in a 20-year period? Can this be right, or are we about to reach a major drop off – were the last two years just out of the ordinary? Time will tell, but there are no signs yet of the bombardment slowing down, and if my previous prediction is anything to go by, the figure could even be an under-estimate.

New plesiosaur taxa
Figure 2. Adjusted plot, with the 2001-2020 prediction based on 2001-2012 data.

So, how many plesiosaurs have been actually been named since 2008? Here’s a summary of all the new additions so the group:

Borealonectes (2008)

Nichollssaura, Gallardosaurus (2009)

Meyerasaurus, Alexeyisaurus (2010)

Abyssosaurus, Westphaliosaurus, Hauffiosaurus tomistomimus, Marmornectes,  Zarafasaura (2011).

Albertonectes, Anningasaura, Avalonnectes, Cryonectes, Lusonectes, Djupedalia, Dolichorhynchops tropicensis, Eoplesiosaurus,  Pliosaurus funkei, Spitrasaurus wensaasi, Spitrasaurus larsoni, and Stratesaurus (2012). So far.

Presuming I haven’t missed any (and please let me know if I have), that’s 22 new binomial taxa in the space of five years: 18 new genera and 21 new species (I’ve only listed the new species names above where they belong to existing genera, or where two new species have been erected within a new genus). I think this significant increase is due to several factors.

Firstly, historic plesiosaur specimens are receiving a considerable amount of renewed research attention. Many of the new taxa are based on fossils excavated in Victorian times. Anningasaura, Avalonectes, Eoplesiosaurus, Lusonectes, Strateosaurus, all fall into this category. Plesiosaurus continues to be exposed as the waste basket taxon it is.

Secondly, there have been numerous new discoveries in recent years. Sometimes these are the result of chance. Sometimes they are the result of a positive relationships that have developed between collectors or mining/quarrying businesses and palaeontologists. But often they are due to dedicated efforts to explore new strata or geographical areas. Djupedalia, Pliosaurus funkei (‘Predator X’ and ‘The Monster’), Spitrasaurus, and Zarafasaura, come to mind here.

Finally, more palaeontologists are looking at plesiosaurs in general. With fresh eyes. We are seeing differences where we weren’t even looking before, we are examining specimens more closely and more critically, we are applying new techniques and technologies to gain a greater understanding of plesiosaur anatomy, biology and phylogeny. It is inevitable that as more of us look, and as we look in more detail, we begin to unravel the complexity and diversity within Plesiosauria. Similar things are also happening in ichthyosaur research and mosasaur research, and I fully expect this ‘Mesozoic Marine Reptile Renaissance’ to continue into the foreseeable future. I’m looking forward to what the future holds in the world of plesiosaurs, even if I am struggling to keep up. One of these days I might even get around to writing about some of these new taxa and adding them to The Plesiosaur Directory…

References

Smith, A. S. 2007. Anatomy and systematics of the Rhomaleosauridae (Sauropterygia: Plesiosauria). PhD thesis. University College Dublin, 278pp. (Unpublished) (download PDF – 12.5mb )

Written by Adam S. Smith

October 17th, 2012 at 12:00 pm

Mine’s bigger than yours! The Monster of Aramberri, Predator X, and other monster pliosaurs in the media

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During the past decade several dramatically named giant pliosaurs have hit the mainstream media, many claiming to be the biggest yet discovered. But only a trickle of peer-reviewed literature has been published to accompany these news stories. The lack of published data makes it really difficult to sift the facts from the fiction, and it’s easy to get the different stories muddled up, especially in the case of two identically sized congeneric pliosaur specimens from Svalbard: ‘The Monster’ and ‘Predator X’. So in an attempt to iron out the details and assess what we really know about all these specimens, here’s a short summary of the main players.

The Monster of Aramberri
Hit the mainstream media: 2002.
Estimated length in media: 18 m.
Conservative estimated length 15 m.
Material: Partial vertebral column, proximal end of a femur, part of the pelvic girdle, and cranial fragments. The fragment of rostrum collected in 1985 is now lost.
Where: Aramberri, Mexico.
Excavation: The original excavation in 1985 yielded a partial rostrum and vertebral column. The excavation site was reidentified in 2001 and additional material was collected during 2001 and 2002.
Peer-reviewed scientific references: Buchy et al. (2003).
Notes: The material was collected over a period of several years, but the discovery only hit the mainstream media in 2002 when more substantial pieces of the skeleton were discovered. An excellent account of the ‘Monster of Aramberri’ is given here by Richard Forrest. Buchy et al. (2003) described UANL-FCT-R2, the partial vertebral column discovered in 1985 [pictured below], but the majority of the skeleton has not been described and is in the process of being prepared. I’ve confirmed with Marie-Celine that the vertebrae described in 2003 are part of the ‘Monster of Aramberri’, but it is worth noting that the 2003 paper doesn’t explicitly mention ‘The Monster of Aramberri’ by name. Originally referred to Liopleurodon, it isn’t considered so any more (Buchy & Frey, 2003).

Monster of Aramberri vertebrae

Part of a figure from Buchy et al. (2003) showing some of the vertebrae and girdle elements of 'The Monster of Aramberri' of the

The Monster
Hit the mainstream media: October 2006
Estimated length in media: 15 metres
Conservative estimated length: 13-15 m
Material: anterior part of rostrum, two cervical and numerous dorsal vertebrae, a nearly complete coracoid and right forelimb, and several dorsal ribs and gastralia.
Where: Svalbard, Norway.
Excavation: Discovered in 2006 and excavated in 2007.
Peer-reviewed scientific literature: none.
Notes: ‘The Monster’, not to be confused with ‘The Monster of Aramberri’, was the first pliosaur from Svalbard to be excavated and the first to make the news. A second giant pliosaur (‘Predator X’, see below) was discovered at the same time, but was excavated the following season. Richard Forrest’s 2008 article on the plesiosaurs from svalbard provides a thorough discussion, including comments on ‘The Monster’, but it was written before the second pliosaur hit the mainstream media.

Paddle of 'the monster'

Partial forelimb of 'The Monster'

Predator X
Hit the mainstream media: March 2009
Estimated length in media:
15 m
Conservative estimated length: 13-15 m
Material: Partial skeleton including posterior skull region and anterior cervical vertebrae.
Where: Svalbard, Norway.
Excavation: Discovered in 2006 and excavated in 2008.
Peer-reviewed scientific literature: none.
Notes. The fossil material attributed to this pliosaur was first mentioned in stories covering “The Monster” in 2008, but the name ‘Predator X’ was coined after the specimen was excavated and it hit the media in 2009. According to an SVP poster by Knutsen et al. (2009) both ‘The Monster’ and ‘Predator X’ belong to the same taxon – they are congeneric and they are closest in their anatomy to Pliosaurus. They are both estimated to be the same size, and they are also both from the same geological formation, so with all these similarities it’s easy to confuse the two. ‘Predator X’ inspired the cover story for the 31 October 2009 issue of New Scientist, and was the main subject of a recent History Channel documentary of the same name, which also featured another giant pliosaur – the Weymouth Bay pliosaur. ‘Predator X’ will also appear in the BBC’s upcoming series Planet Dinosaur. Despite its widespread presence in the news and on TV, I was unable to find a suiatable photograph of the actual material.

The Weymouth Bay pliosaur
Hit the mainstream media: October 2009
Estimated length in the media: 16 m
Conservative estimated length: 12 m.
Material: skull and mandible (missing the tip of the manibular symphysis).
Where: Weymouth Bay, Dorset, UK.
Excavation: Discovered in pieces over a period of time – specific details unclear. The specimen was purchased by Dorset County Museum in Dorchester.
Peer-reviewed scientific literature: none.
Notes:
There is an excellent account of the Weymouth Bay pliosaur here by Richard Forrest. The skull as preserved is 2.1m long.

The Weymouth Bay pliosaur

The Weymouth Bay pliosaur and Richard Forrest

 

So there we have it, four mega-pliosaurs making big news in the space of a decade. All of them have conservative and realistic length estimates around the 15m mark, with the Weymouth Bay pliosaur possibly slightly smaller and ‘The Monster of Aramberri’ possibly slightly larger. But all the estimates are way too wooly to take seriously just yet. So all these monsters will remain jostling for top spot until the scientific papers are published, and until we have a better understanding of pliosaurid proportions.

There are or course plenty of other giant pliosaurs, which frequently pop up in discussions too, including additional real contenders for ‘biggest pliosaur ever!’. While I do plan to write more on giant pliosaurs in the future, I’ve stuck to the ones in the mainstream media for now. You might have noticed that Liopleurodon was conspicuously omitted from this post. Well, although it is entirely relevant to the present topic, it hasn’t been in the news recently so I decided to leave the magical Liopleurodon alone this time around. It will be nice to write about a pliosaur with an actual scientific name for a change, even if that’s opening a can of worms in itself!

References

Buchy, M.-C. & Frey, E. 2003. Was it really eating granite? We’re searching hard: history of the Monster
of Aramberri (and stories about it). First meeting of the EAVP – abstracts, 39.

Buchy M.-C., Frey E., Stinnesbeck, W. ; López-Oliva J.G. 2003. First occurrence of a gigantic pliosaurid plesiosaur in the Late Jurassic (Kimmeridgian) of Mexico. Bulletin de Societe géologique de France, 174, 271-278.

Knutsen, E., Druckenmiller, P., Hurum, J., Nakrem, H. 2009. Preliminary account of new Late Jurassic pliosaurid material from Svalbard, Norway. Journal of Vertebrate Paleontology, 128A.

Noè, L. F., Smith, D. T. J. & Walton, D. I. 2004. A new species of Kimmeridgian pliosaur (Reptilia; Sauropterygia) and its bearing on the nomenclature of Liopleurodon macromerus. Proceedings of the Geologists’ Association 115, 13-24.

Written by Adam S. Smith

April 5th, 2011 at 6:32 pm