The world's biggest ever fish: time to put out the trash

The Bob Nicholls artwork I featured yesterday got some of you talking about a particularly famous denizen of the Jurassic seas. Namely, the gigantic, edentulous pachycormiform actinopterygian Leedsichthys problematicus from the Callovian Oxford Clay Formation. Hold on - - isn't that a... a... fish? How on earth can I justify this inexcusable off-topicness?


Well, quite easily actually. The gigantic size of Leedsichthys (more on that below) means that it can't be ignored whenever we discuss trophic interactions in the Middle Jurassic seas. Perhaps it was preyed on by the large, contemporaneous pliosaurs (see Martill 1988, Hudson et al. 1991, Martill et al. 1994), and it's even been suggested that smaller marine reptiles - like metriorhynchid crocs - swam up to it and took chunks out of it on occasion. That's not such an unreasonable idea, given that some living odontocetes have been reported to behave in a similar fashion (however, read on). Its carcass must have provided a phenomenal resource for scavenging marine reptiles and all manner of other organisms. In short, Leedsichthys is 'very relevant' if you're interested in marine reptiles [different versions of Leedsichthys, as portrayed in popular media, shown above. Image provided by Jeff Liston, used with permission].


I also have quite a soft spot for Leedsichthys, having assisted in the 2002 excavation of Ariston, one of the most complete specimens yet found (Liston 2006) (this dig featured in the 2003 TV series The Big Monster Dig, broadcast on the UK TV channel Channel 4). In the adjacent image, that's me lying on my belly in the middle. It's a good arse shot. Anyway, we all love gigantic fishes, even those of us devoted to tetrapods...

While Leedsichthys was named in 1889, it's only in the past three decades that it's become well known among palaeontologists and palaeontology enthusiasts, and only in the past ten or so years has it become represented in the popular media. However, things have gone horribly astray, and it's time to set the record straight.

The popularisation of Leedsichthys began with a semi-popular article published by Dave Martill in Geology Today (Martill 1986a). Because it featured a life restoration - the first ever published (so far as I know) - it has effectively become the first article that most people have gone to when seeking information on this fish. Dave also wrote a technical paper, reviewing knowledge of the fish's anatomy and palaeobiology (Martill 1988). By making extrapolations from the size of the tail and estimated size of the gill arch apparatus, Dave estimated a lower total length of 13.5 m for Leedsichthys, and a possible upper limit of 27.6 m. The latter measurement is larger than an average Blue whale Balaenoptera musculus (the record for which is 33.5 m). Unsurprisingly, the 27 m estimate is the one that's become repeated most often. Since Dave's work, Leedsichthys has been re-visited by Jeff Liston for his PhD project: see Liston (2004, 2006, 2008) and Liston & Noè (2004). Jeff's work has shown that various ideas that are now frequently promoted about Leedsichthys - namely, those regarding its size, its shape and proportions, and its alleged interaction with a metriorhynchid - are erroneous.

Out with the old, please

It's notable that quite a few recent artistic renditions of Leedsichthys are (essentially) carbon-copies of the incredibly ugly, armour-plated version produced for the BBC television series Sea Monsters [visible in the slide used at the top], broadcast in 2003 and featuring a time-travelling Nigel Marven. This series was produced by Impossible Pictures, and it may or may not mean anything that Marven (playing himself) was also featured in series 3 of Impossible's Primeval; this time round he met his end at the jaws of a giant theropod, a great scene. Sorry for the spoiler. Unfortunately, the Sea Monsters Leedsichthys - itself based mostly on a drawing produced by Paul Pollicott and published by Martill (1986a) - is substantially inaccurate. Its pectoral fins are too large in proportion to the body, the deep, dorsally convex head (creating a 'humped' appearance) is not accurate, and the body is not long enough. I base these assertions on Jeff's work: a more accurate Leedsichthys [produced by Bob Nicholls] is shown below. Note the absence of the 'hump', the far longer, slimmer body, and the different fin proportions. This should now become the standard template for this fish: the old version - you can see versions of it at wikipedia and elsewhere on the web - is utterly and unquestionably inaccurate.


What about the size? The 13-27 m length extrapolated by Dave used data from a smaller relative, Asthenocormus, and also assumed that things like the ratio of gill basket width to total size scaled isometrically across the group. Alas, both assumptions are unlikely to be correct. More recent investigation has shown that a total length of 9 m is more like it (Liston & Noè 2004). Read this research before producing yet more over-sized renditions of this stupendous animal (for more thoughts on this and other issues, see Big Dead Fish).

Swimming croc vs mega-fish

Finally, if you've seen illustrations that show a metriorhynchid crocodilian (an animal of about 3 m in total length) swimming up to a Leedsichthys and biting it, you'll be interested to know this is not mere artistic whimsy, but is in fact based directly on an interpretation in the literature [in the illustration by Colin Swift, shown below, the metriorhynchid is near the fish's dorsal fin. A Liopleurodon attacks the fish's pectoral fin at the same time]. While reviewing stomach contents reported for Oxford Clay metriorhynchids, Martill (1986b) noted that a Leedsichthys frontal bone, held in the collections of the Peterborough Museum, 'has a large tooth of Metriorhynchus embedded in it towards the margin' (p. 623) (despite viewing this specimen several times, I seem not to have any photos of it). New bone growth around the tooth showed that healing had occurred. It was therefore proposed that the metriorhynchid had attacked the fish, and that the fish had survived and started to heal its wound. Given that the 'frontal' (read on) was over a metre long, and given the discrepancy in size between a metriorhynchid and an adult Leedsichthys, this interaction might imply that metriorhynchids acted in a similar fashion to cookie-cutter sharks: that they swam up to giant animals and took chunks out of them. As mentioned earlier, interactions of this sort have been observed in cetaceans, as False killer whales Pseudorca crassidens have been filmed biting chunks out of Sperm whales Physeter macrocephalus (Paul 1998).


However, there are two problems with this otherwise appealing notion. Firstly, the bone identified by Dave as a frontal is not a frontal: frontals are absent in Leedsichthys (the skull is roofed by parietals and postparietals only, with a rostrodermethmoid, nasals and antorbitals located more anteriorly), and the bone is actually a hyomandibula (Liston 2008). Secondly, the bone around the embedded tooth does NOT display any sort of reaction, and hence there is no evidence for healing (Liston, PhD thesis). So, while a reptile did bite this Leedsichthys specimen, it was more likely scavenging on a dead one, not attacking a live one. Indeed, as Jeff notes in his thesis, it's difficult to imagine how a marine crocodilian might have bitten into a hyomandibula unless that bone was already partially disarticulated from the rest of the skull. Other evidence points towards the possibility that metriorhynchids sometimes scavenged from submerged vertebrate carcasses (Forrest 2003).


Incidentally, some Leedsichthys fin rays (perhaps representing the dorsal fin in one specimen, and a pectoral fin in another) do bear evidence of attack by large predators. What look like curving bite marks appear to have been made by plesiosaurs [another Bob Nicholls piece shown here. While more accurate in proportions and shape than most other versions, this reconstruction is now out of date and has been superceded by Bob's CG version shown above (the greenish one)].

As is well known, I, ordinarily, only blog about tetrapods. Today that rule has been broken, and I feel the shame. But I felt compelled to do it, given the amount of incorrect data that's out there about this fish. I hope this one little article starts to turn the tide and make a different.

Finally - if this has interested you, it is mandatory that you attend Sea Dragons of Avalon: the early radiations of the marine reptiles and recovery from the Triassic-Jurassic faunal crisis, with special reference to Street in Somerset and the wider British record (Street, Somerset, UK, July 30th-August 1st): follow the links here for more information.

Refs - -

Forrest, R. 2003. Evidence for scavenging by the marine crocodile Metriorhynchus on the carcass of a plesiosaur. Proceedings of the Geologists' Association 114, 363-366.

Hudson, J. D., Martill, D. M. & Page, K. N. 1991. Introduction. In Martill, D. M. & Hudson, J. D. (eds) Fossils of the Oxford Clay. The Palaeontological Association (London), pp. 11-34.

Liston, J. 2004. An overview of the pachycormiform Leedsichthys. In Arratia, G. & Tintori, A. (eds) Mesozoic Fishes 3 - Systematics, Paleoenvironments and Biodiversity. Verlag Dr. Friedrich Pfeil (München), pp. 379-390.

- . 2006. From Glasgow to the Star Pit and Stuttgart: a short journey around the world's longest fish. Glasgow Naturalist 24 (4), 59-71.

- . 2008. A review of the characters of the edentulous pachycormiforms Leedsichthys, Asthenocormus and Martillichthys nov. gen. In Arratia, G., Schultze, H.-P. & Wilson, M. V. H. (eds) Mesozoic Fishes 4 - Homology and Phylogeny. Verlag Dr. Friedrich Pfeil, München, pp. 181-198.

- . & Noè, L. F. 2004. The tail of the Jurassic fish Leedsichthys problematicus (Osteichthyes: Actinopterygii) collected by Alfred Nicholson Leeds - an example of the importance of historical records in palaeontology. Archives of Natural History 31, 237-253.

Martill, D. M. 1986a. The world's largest fish. Geology Today 2, 61-63.

- . 1986b. The diet of Metriorhynchus, a Mesozoic marine crocodile. Neues Jahrbuch fur Geologie und Paläontologie, Monatshefte 1986, 621-625.

- . 1988. Leedsichthys problematicus, a giant filter-feeding teleost from the Jurassic of England and France. Neues Jahrbuch fur Geologie und Paläontologie, Monatshefte 1988, 670-680.

- ., Taylor, M. A., Duff, K. L., Riding, J. B. & Bown, P. R. 1994. The trophic structure of the biota of the Peterborough Member, Oxford Clay Formation (Jurassic), UK. Journal of the Geological Society, London 151, 173-194.

Marven, N. & James, J. 2003. Sea Monsters: Prehistoric Predators of the Deep. BBC Books, London.

Paul, G. S. 1998. Terramegathermy and Cope's rule in the land of titans. Modern Geology 23, 179-217.

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Hi Darren,

Very interested in this. By weird cooincidence I was thinking about Leedsichthys after reading about Protosphraena gladius on Mike Everhart's Oceans of Kansas (also featuring a picture by Bob) which discusses a species very different to the Chalk Sea 'swordfish' I was familar with. Seems very in keeping with the whole whale/whale shark/ basking shark/Leedsichthys anologue group.

Small wordl. Big fish.

By Steve White (not verified) on 02 Jul 2009 #permalink

I think we're going to need a bigger bottle of Tarter Sauce...

But srsly, - excellent post - thanks! I had not run into any lierature about this monster prior to your post, but you have piqued my curiosity, so I will now keep an ey out for future info about it.

I find it particularly interesting how much the new correct reconstructions remind me of the big planktivorous sharks. Also the scene where Nigel gets devoured in primeval was hilarious and went a long way to erasing the awfulness of his earlier timetravelling naturalist show (exinct zoo or whatever it was called).

Just for the sake of stating the obvious, if Leedsichthys was 9 m long, that would mean it was distinctly smaller than both whale sharks and basking sharks, right?

With reference to comment 3: Prehistoric Park. Shudder.

I do a good Nigel Marven impression, by the way, but all I can say is "I've seen this before".

Pity it has such a crap name. Such a big, spectacular fish deserves something grander-sounding. "Leedsichthys" sounds about right for a 3 cm-long goby or a mud-grubbing catfish, but not for a whopper like this.

"Cetorhinus", "Carcharodon", "Regalecus" - now THOSE are names fit for big fish!

Sean Craven:

Even if we questionably call sharks "fish", Leedsichthys with its presumed 9 m average is much larger than basking sharks [6-7 m avg, 10 m max] and probably in the same rough size class as whale sharks [~14 m max]. The next biggest actinopterygian is probably the giant fossil moonfish Megalampris with a length of 4 m and a weight probably floating around 2 tonnes (warning! unofficial extrapolation!) Alright, back to work.

I just recently read about Leedsichthys in BIG FISH by Richard Ellis, Abrams 2009.He discussed 4 species of the distant past. Dunkleosteus, Leedsichthys, Megalodon and Xiphactinus.He states that Leedsichthys problematticus reached a length of 40 ft, "but published estimates of specimens of twice the length" It`s feeding habits were similar to the modern Blue whale IE.a Plankton feeder.

By Bob Michaels (not verified) on 02 Jul 2009 #permalink

Well, I guess I sit here well and truly 'spanked' for my version! I am curious, though - what about the laminar ridges? They do seem to be a common feature of larger swimmers (I was watching the strongly ridged leatherback turtle on Attenborough's "Life in Cold Blood" last night, and also 'borrowed' them from a whale shark for my reconstruction - I've also seen them employed on newer 'non-Great-White' reconstructions of C. megalodon). the new more streamlined Bob Nicholls version has none - are they completely ruled out?

Also, Zach, unless there's a typo between Ellis's article (to which I don't have access) and Bob Michael's post (Comment #8), Ellis was talking about 40 FEET, with a speculative upper range of twice that - still a far cry from 40 METERs, so perhaps you can regain a modicum of your respect for him!

By Colin Swift (not verified) on 02 Jul 2009 #permalink

Ah--I misread it! 40 ft is much nicer! It did seem odd, as Ellis is usually pretty awesome. Yes, I can deal with 40 ft. Imagine dip-netting for THAT sucker!

Zach: I suddenly have less respect for Richard Ellis

IIRC he claimed in Aquagenesis that the sharks Edestus giganteus and Parahelicoprion reached 50 and 100 feet, respectively. Where he got this from, I have no idea...

In a TV documentary - which I've seen once, long ago - it was claimed that new evidence showed that edestids were eel-like and incredibly long, and I'm pretty sure a figure of 50 ft was mentioned. Some years ago, Steve White (see comment # 1) and I produced an article on fossil sharks, and produced some new-look edestids based on this 'data'. But we never learnt where the info came from. I asked everyone I knew in the fossil shark world, and none had ever heard of this 'new evidence'.

Has anyone done any work on the idea that fish size might be limited by dissolved oxygen versus atmospheric oxygen levels used by aquatic tetrapods? It seems especially pertinent for active predators.

Well, I've always regarded Leedsichthys as an honorary tetrapod, so no harm done. It's ironic that every large flat skull bone of Leedsichthys has, until recently, invariably been identified as a frontal.
BTW, that's me in the orange hi-vis vest.

By Mark Evans (not verified) on 02 Jul 2009 #permalink

Darby, a fishes size has to be limited by it`s Genome as well as environmental factors.

By Bob Michaels (not verified) on 02 Jul 2009 #permalink

I can't but hold a certain affection for the fish the first thing about which I learned was that it wasn't 30 m long.

Would Liston's pieces be available in electronic format?

By Andreas Johansson (not verified) on 02 Jul 2009 #permalink

Hi there,
the P. gladius mentioned in comment 1 has also been featuring on the Marine Reptiles Forum and one of the features of this species is spectacularly large eyes; there are sclerotic rings showing the eye exceeded 12.5cm diameter.
Are there any preserved sclerotic rings showing the eye size of L. problematicus?


Awesome! I'd heard of Leedsichthys, of course, but I never really heard much said about it other than "giant monster fish fom the Mesozoic the size of a blue whale!" Ugh. Thanks for this nifty (an accurate) info, Darren!

P.S. Unfortuanately, as much as I like Leedsichthys, I must do my job upholding the law - I will have to arrest you for blogging about non-tetrapods on Tetrapod Zoology. Drop the weapon, hands in air. You have the right to remain silent, anything you say can and will be used against you in a court of law. :-D

By Michael Erickson (not verified) on 02 Jul 2009 #permalink

I'm forgiving you for this side tangent... I've always thought that Impossible Pictures inflated this fish (given how much they inflated the Pliosaur attacking it). Which is sad as I still think of all the modern CG Dino documentaries theirs are the best (though Primeval jumped the future Predator as of Cutter dying!)

Despite it being manditory to attend the Sea Dragons of Avalon sadly you'll have to cover it for those of us stuck here down under (who knew flying to the other side of the planet was so much :P)

Cheers for the very informative post!

Glad to see we're not the only ones having problems scaling up large filter feeding pachychormids from Astenochormus. I've prepared or am preparing the only 3 specimens with skull discovered so far, and man it's a weird animal. Body length estimates are in the 4-18m range.... that's quite a difference.

I too would be very interested in any Leedsichthys sclerotics. If "P." gladius really is as short as 4m, it would seem to have a perpetually surprised look to it.

9m is still a HUGE fish. But, as the song goes:

Like the size of the fish that the man said broke his reel - it's growing!

By MadScientist (not verified) on 02 Jul 2009 #permalink

Dear Mr Erickson,

"I will have to arrest you for blogging about non-tetrapods on Tetrapod Zoology"

As self-appointed solicitor for Mr Naish let me point out that this post was clearly about zoology and Mr Naish is, to my knowledge and belief, a tetrapod, thus bringing the post within the meaning of "Tetrapod Zoology" in the sense of zoology by a tetrapod.

In light of the above explanation, continued allegations of criminal behaviour, to wit, posting an off-topic post in his own blog contrary to The Internet Nitpickery and Pecksniffery Act (2008) made against Mr Naish will result commencement of an action in libel.

Govern yourself accordingly,

M. T. Threat,
Bender, Badger, Wheedle and Cajole, Solicitors

By Mike from Ottawa (not verified) on 02 Jul 2009 #permalink

Isn't the story that a Leedsichthys fossil was once mistaken for a dinosaur (see the appropriate page at Toby White's "" site survey of chordates for details) enough of a Tetrapod connection?

By Allen Hazen (not verified) on 02 Jul 2009 #permalink


False killer whales Pseudorca crassidens have been filmed biting chunks out of Sperm whales Physeter macrocephalus

Amazing! I would have thought that sperm whales are able to defend themselves against such attacks (they catch giant squid on a regular basis, after all), but apparently that's not the case. Would any such footage happen to be available for watching somewhere on the web?

A more general point: Considering the immense diversity of 'bony fish', why is it that they don't seem to have fully exploited the Huge Plankton-eater niche? Among extant vertebrates, the largest specialist planktonivores are either mammals (baleen whales) or elasmobranchs (whale shark, basking shark, megamouth shark, manta ray). Where are all the giant* filter-feeding actinopterygians? Unless I'm forgetting something, the largest extant ones are the North American and Chinese paddlefish (Polyodon and Psephurus, respectively) but while they're big they hardly qualify as 'giant' (and, besides, they're freshwater, not marine, taxa). Is there something fundamental about actinopterygian morphology and/or life history that makes it harder for them to evolve into, if not blue whale-analogues, then at least into basking shark-analogues? And is Leedsichthys really unique, or are there other presumed giant filter-feeding actinopterygians known in the fossil record?

* There are, of course, plenty of small plankton-eating bony fish; as these often move and forage in immense schools, they might perhaps be considered 'superorganisms' in an ecological sense. But that's not quite the same thing.


"Cetorhinus", "Carcharodon", "Regalecus" - now THOSE are names fit for big fish!

How about 'Mola'?


RE: Edustus and Helicoprion: The eel-like bodyplan came from a documentary on the sharks of Bear Gulch, featturing artist Ray Troll. I don't remember the name of the palaeontologist involved but he alluded to new info that led to Troll actually doing a new art reconstruction of Helicoprion based on the supposed new work. He also mentioned that it was much longer than previously thought. However, soon after Richard Ellis did a more conventional reconsruction in (I think) Aquagensis. One of Ray Troll's books also mentions that he was reverting to usual shark body plan.

I still have the documentary somewhere.

By Steve White (not verified) on 02 Jul 2009 #permalink


"Cetorhinus", "Carcharodon", "Regalecus" - now THOSE are names fit for big fish!
How about 'Mola'?

OK, I'll grant you "Mola" isn't that great.... but the best one of all has to be "Megachasma"!

Prior to the (rather delayed) publication of Taylor et al.'s 1983 paper on Megachasma pelagios (recall that the first megamouth was discovered in 1976), Richard Ellis and John McCosker decided to 'prompt' their colleagues into hurrying up a bit by producing a spoof article that looked, at first sight, like blatant intellectual theft. This article - the text of which wasn't about megamouths, but about the cat in Japanese art and some other random stuff - is even mentioned in the acknowledgements of Taylor et al. (1983). Anyway, it included an alternative binomial for the shark - does anyone know what it was?

Ref - -

Taylor, L. R., Compagno, L. J. V. & Struhsaker, P. J. 1983. Megamouth - A new species, genus, and family of lamnoid shark (Megachasma pelagios, family Megachasmidae) from the Hawaiian Islands. Proceedings of the California Academy of Science 43, 87-110.

Any details about this spoof article?

Dartian (#26):

The Chinese paddlefish is a piscivore which occasionally takes benthic arthropods. Psephurus also seems to be capable of living in saltwater (East China and Yellow Seas) to some degree. It's really unfortunate that this species is in its death throes.


The Chinese paddlefish is a piscivore which occasionally takes benthic arthropods

Oops, so it is! Thanks for the correction. Hmm. Since Psephurus is the larger of the two paddlefish taxa, that actually emphasises the question why filter-feeding actinopterygians tend to be so much smaller than filter-feeding elasmobranchs.

You guys made me watch bits of Primeval, really.

Unusual British convention of action film. People running away always trip, car keys always get stuck... And the concept of having 20-foot tall dinosaur running around the airport and then "to cover up the whole incident" is a bit over the top... Many people would probably see this and "Doctor Who" as a kind of strange deadpan-like humor.

Really great series of article, tetrapod technically or not.
I notice that in comment #2, J-dog, after recommending a larger bottle of tartar sauce, inquires about the monsterous sized fish, but uses an unfamiliar word: "lierature". Either he's dropped the letter "t" from literature, or more fortuitous, he's invented a proper category for stories regarding the huge size of fish as told by fishermen of both the paleo and contemporary variety.

Finally! I don't care if it's not a tetrapod, the attention is well deserved in this instance. I've been waiting for somebody to review this genus for aaaages. Thank you, thank you, thank you, Darren!

I wonder, did they tack the armor plates on the Impossible Pictures version just to make it more "placoderm-y"?

By Metalraptor (not verified) on 05 Jul 2009 #permalink

Only marginally on-topic, but since the subject of this thread was giant fish and since the ocean sunfish Mola was mentioned earlier...

As Adam Yates recently mentioned over at Dracovenator, Gregorova et al. (2009) report the discovery of a gigantic new sunfish, Austromola, from the Miocene of Austria (not known today for being prime molid habitat). With an estimated distance of about four metres from dorsal to anal fin tip, Austromola is significantly larger than the extant Mola, and must surely be one of the largest actinopterygians that ever existed.

* That same JVP issue also reports the discovery of a giant piranha from the Miocene of Argentina (Cione et al., 2009).


Gregorova, R., Schultz, O., Harzhauser, M., Kroh, A. & ÄoriÄ, S. 2009. A giant early Miocene sunfish from the North Alpine Foreland Basin (Austria) and its implication for molid phylogeny. Journal of Vertebrate Paleontology 29, 359-371.

Cione, A.L., Dahdul, W.M., Lundberg, J.G. & Machado-Allison, A. 2009. Megapiranha paranensis, a new genus and species of Serrasalmidae (Characiformes, Teleostei) from the Upper Miocene of Argentina. Journal of Vertebrate Paleontology 29, 350-358.

News just in! New Jurassic and Cretaceous pachycormids described in Science! Extra, extra, Read all about it!

Friedman M, K Shimada, LD Martin, MJ Everhart, J Liston, A Maltese, M Triebold. 2010. 100-million-year dynasty of giant planktivorous bony fishes in the Mesozoic seas. Science 327: 990-993. doi: 10.1126/science.1184743

Cavin L. 2010. On giant filter feeders. Science 327: 968-969. doi: 10.1126/science.1186904

By John Scanlon, FCD (not verified) on 18 Feb 2010 #permalink