Leedsichthys: A very private suspension feeder

Dr Jeff Liston (UK)

A couple of months ago, I had the pleasure of visiting a prodigious private collection (at a secret location) on the south coast of England. The material is secured by bequest to a national museum collection. Representative of diverse localities and faunas, with scrupulously recorded collection data, beautifully stored in row upon row of display cabinets, it forced me to reflect on the fact that vertebrate palaeontology has always been particularly reliant on private collectors. Museums rarely have the ability to send their own staff out to prospect for, or retrieve, such specimens, and so hope to have people effectively to act on their behalf as their eyes in the field. To that extent, institutions often foster relationships with collectors, partly in the hope that they will get ‘first refusal’ in case anything significant is found by that collector, but also to try to ensure, wherever possible, that any such collecting takes place within the law.

This reliance on private collectors is true around the world. Almost 20 years ago, two German collectors – Ralf Metzdorf and Matthias Metz – came to the Isle of Skye to look for ammonites, and inadvertently found Scotland’s first dinosaur. Their run of bad luck in ammonite hunting had started in northern Germany in the mid-eighties, when (as parts of two different school-age palaeontological groups) they had chanced upon the only German specimen of Leedsichthys, in a Middle Jurassic quarry in the Wiehen Mountains (Liston, 2010).

And Leedsichthys – that leviathan of osteichthyans (Fig. 2A) – has a long pedigree in private collections. It was even present in the private collection in the south coast of England that I looked at (Fig. 1).

It was also first discovered by the remarkable private collector, Alfred Nicholson Leeds, before 1887. He retrieved the first ten specimens of the animal, scattered across a single bed of the Callovian Oxford Clay (top of the Middle Jurassic, over 150Ma in age) and he spent a lifetime excavating in this layer of rock (although, in retrospect, it looks increasingly as though these ten separate specimens actually constitute parts of a single, very extensive individual animal). Arthur Smith Woodward went on to describe the animal and named the genus after Alfred – but also gave it the species name problematicus to indicate the difficulty he had in interpreting the massive, yet fragmentary, bony remains.

Specimens of this animal hold something of a record in fossil fish circles, as on three separate occasions, entirely different bones have been identified as belonging to different parts of a stegosaurian dinosaur. Indeed, it was only through the intervention of a personal visit to Alfred’s Eyebury home on 22 August 1888 by the legendary US ‘bone warrior’ Othniel Charles Marsh that one of these misidentifications was dispelled. This resulted in a gift from Leeds to Marsh of a representative suite of Oxford Clay bones, including Leedsichthys, which today resides in the hallowed stores of Yale University’s Peabody Museum.

This is historically significant, because it was actually the first set of material to leave Eyebury, predating any agreed sale to the British Museum (Natural History) by two years (Liston & Noé, 2008). In addition, there evidently remained a link between the two men after that first meeting, because Marsh dropped in to Eyebury when he was next passing through, ten years later on 17 August 1898, while the Leeds family were reconstructing the gigantic Leedsichthys tail specimen.

Alfred subsequently (Liston & Noé, 2004) went on to retrieve many further specimens of Leedsichthys. Some of these went to the NHM (London), many others were distributed around the world through the Bonn dealer Bernard Stürtz’s network of clients, and a series was dispersed on Alfred’s death in 1917 to a variety of museums in Britain, including Kendal, Cardiff and the Hunterian Museum (University of Glasgow).

Private collectors have continued to carry the torch for this fish, with fossil hunters like Nick Oliver retrieving specimens from the Oxford Clay of Kempston Quarry in 1998 (material now lodged at New Walk Museum), Gerard and Elizabeth Pennettier uncovering remains from under the beach sand of the Vaches Noire (also Callovian, contemporary with the Oxford Clay around Peterborough). Even more important is Dolf Gielen uncovering the first remains from the Cap de la Heve (Kimmeridgian) of Normandy (now accessioned at the Hunterian Museum) and, as with material from the Atacama Desert (Oxfordian), this showed remarkable preservation of delicate structures not usually visible in specimens from the Oxford Clay (Liston, 2008). Again, such enthusiasts have to be our eyes in the field, finding the animals in the localities that those in museums do not get the time to find themselves.

Indeed, it seems that no museum has ever collected a specimen of Leedsichthys. It may adorn collections as unassuming as Kendal Museum (Fig, 2B), as far-flung as Antofagasta, and as stolidly reliable as the NHM, but no museum has ever actually gone out and collected a specimen.

To be completely fair, the Natural History Museum did come close – photographs exist that attest to an expeditionary force led by the redoubtable Colin Patterson and including Alison Longbottom, Penny Waters, Frank Howie, Gareth Hughes and Ron Croucher, all under the careful liaison of John Horrell standing around a specimen of gill arch remains of Leedsichthys in Stewartby, an Oxford Clay pit (Figs. 3A and 3B).

However, the exercise was not an easy one in inclement weather. In addition, some erosion had occurred to the material since it had first been exposed and the attitude of the collectors to their quarry cooled in the process. I am reliably informed by one of the participants that day in June 1973 that, after driving to the top of the pit, Colin made the decision to abandon the specimen in disgust and it was chucked out of the Landrover, before they drove back to London empty-handed (pers. comm., Alison Longbottom). Colin famously “never liked” Leedsichthys (pers. comm., Peter Forey, August 2005).

There are a lot of reasons for specimens of this animal not being collected by such institutions. Firstly, they are very fragmentary. Secondly, the parts that do preserve (the skeleton is only partially ossified, apparently an adaptation connected with its large size) are exceptionally fragile, as Patterson et al. found to their cost, making it difficult to retrieve from what is usually a clay matrix. And, thirdly, those same delicate bones can often be large – the most famous specimen of this animal was a 2.74m-high tail (collected by Alfred Leeds in March 1898), which was displayed at the Natural History Museum (London) from 1899 to 1987. This combination of factors means that it takes an unusually large amount of resources in terms of staff-hours to collect material of this animal properly.

Let us try to put this in some perspective in terms of ‘how much time’ we are talking about here. A few years back, I led a group to retrieve the Star Pit (near Whittlesey, Peterborough) specimen of Leedsichthys, and it became a very long story (recorded elsewhere, Liston, 2006) involving taking a 20m cliff off a 25 x 6m area of bed (Fig. 4A) and hordes of volunteers contributing over 3,100 hours in excavation time, over more than 12 weeks, spread over two field seasons (Fig 4B).

In other words, Colin Patterson, in a NHM memo dated 29 June 1973, complained about having spent about 30 staff-days on their excavation – whereas we spent almost 443 (and that is without accounting for subsequent preparation time). The exercise was extraordinarily successful, yielding for the first time paired bones in a single specimen of this animal, as well as the widest range of identified elements for a single individual.

The resulting collection of over 2,300 separate bones, often encased in Paraloid B72 in the field to prevent their swift deterioration, looked as though they would be stored at the Peterborough Museum without the resources to prepare them for the foreseeable future. However, it is a tribute to the recently deceased Alan Dawn and his dogged determination that he started preparing the material in 2003 and kept going with his own team of volunteer preparators until he had finished preparation late last year. He will be sorely missed.

One of the last pictures that Alan sent me was of the 1.36m–long, prepared right pectoral fin (Fig. 5A) of the Star Pit Leedsichthys (which became known as ‘Ariston’, because the bone kept going on and on), which was one of the last of our excavated elements to be processed by him and his team (Fig. 5B).

It is with some regret that we also have to note that the specimen was not completely retrieved from the site, due to resource constraints, and the Star Pit is now sadly flooded (Fig. 6) – the last remains of the fish known as ‘Ariston’ have been returned to the water (albeit slightly fresher) from whence it originally came.

Leedsichthys is a member of the Pachycormidae – a family of bony fishes that were the first to occupy the role of large aquatic vertebrate suspension feeder, millions of years before whales or sharks started to exploit that niche. As these latter groups have come to dominate the niche in the Cainozoic, so the pachycormids dominated it in the Mesozoic. Suspension feeders extract food that they cannot individually detect from the water column by a variety of means. These can be by filter feeding or filtration (where the water containing the food particles passes through porous structures to separate the food particles from the fluid on the basis of their size and/or shape) or by passing water along surfaces capable of retaining particles that come into contact with them (for example, by secreting mucus).

There are six different mechanisms used in filtration, the most popularly known one is sieving, where the porous structure blocks all particles larger than the pore size, and lets everything smaller through. However, much of suspension feeding does not involve this process, but instead uses complex arrangements of water flow and mucus streams to gather and prepare the food for ingestion by the animal. Therefore, not all suspension feeders are filter feeders – but all filter feeders ARE suspension feeders.

How do we know that this was the feeding style of these animals, when we cannot observe their actual behaviour? This conclusion can be derived from multiple aspects of the animal’s anatomy – fin arrangement, long closely-spaced gill rakers, the absence of teeth on the jaws, an extensive gape, and exceptional size. In particular, the disproportionately enlarged pectoral fins (with a rather high aspect ratio of 9), for an elevated lifting force relative to Standard Length, indicate an unusually low minimum swimming speed – consistent with a slow suspension feeding mode of life. The nearly ubiquitous gill rakers of this animal (on average around 75mm long, looking like small slender dentaries – except, instead of teeth, there are slight bony protuberances) function not only as baffles to protect the delicate respiratory lamellae, as with other fish, but are attenuated, ornamented and densely packed to act additionally as a suspension feeding structure.

Although Leedsichthys may represent the acme of the group, several other pachycormids were also suspension feeders – a fact that has again come to light due to the efforts of private collectors.

The last stage of the Upper Jurassic, just above the Oxfordian and Kimmeridgian levels, that has yielded material attributed to Leedsichthys, is the Tithonian. The (mostly) Tithonian-aged Solnhofen limestone is renowned the world over for its preservation of detail in fossil material, due to the fine grain of its matrix. Yet, despite the many specimens of the pachycormid, Asthenocormus, that have been retrieved from those limestone slabs over the centuries of collecting, only one has ever been found that shows the attenuated and elaborate gill rakers that one would expect a large suspension-feeding fish to have (Fig. 7A).

This specimen was collected by Helmut Leich, the most significant living collector of fossil material from the Solnhofen limestone. Leich’s Asthenocormus (SHL.1309), displayed with the rest of the material at the Bochum Tierpark (www.tierpark-bochum.de), is remarkable because it does not preserve the animal in profile with a closed mouth (thus obscuring how toothless its jaws actually were), but with the skull disarticulated and revealing a cascade of gill rakers, positioned as though spewing forth from its mouth (Fig. 7B). This is the only known specimen to confirm both the presence and the nature of the gill rakers of this taxon (Fig. 7C).

Given that Leich had been a volunteer at Bochum Tierpark since 1948, the zoo took over the presentation of Helmut Leich’s collection in 1996, through 55 showcases of his rare fossils, which he first promoted in his 1967 book Brought to Light after Millions of Years. Now 91 years old, he is still making new discoveries in those same Upper Jurassic slabs. In February 2011, he was publicising the discovery of a cancer-ridden crustacean (for the full story, go to: http://www.derwesten.de/staedte/bochum/Fossiliensammler-aus-Bochum-entdeckt-seltenen-versteinerten-Krebs-id4271937.html). It is collectors like him that have a talent for still finding new treasures from well-known and extensively worked localities and horizons.

This pattern is repeated with the collection of Luc Ebbo. Luc has diligently been collecting material for more than 20 years, from Valanginian, Aptian and Albian aged outcrops around the vicinity of Sisteron, Alpes-de-Haute-Provence, in the south of France. Like Helmut Leich, Luc wishes his collection to be accessible to the public as well as the research community, through the establishment of a museum to contain, protect and prepare the specimens. This collection would be unique in scale and quality in the south of France, and a true cultural asset to the area. Last summer, I visited his home, which was crammed with remarkable Lower Cretaceous specimens from a bygone seabed. In amongst the basements and storerooms of dinosaurs, plesiosaurs and (in some cases, particularly remarkable) ichthyosaurs (Fig. 8B), there was a most beautiful pachycormid (Fig. 8A).

Excavated from the basal Albian near Bevons in 2001, it is remarkably complete (always remembering the larger the adult size of the pachycormid, the less of the skeleton that was likely to ossify and therefore preserve), with a long mouth bursting with gill rakers. Frankly, it looks a little as though it has been considerately prepared before burial, to act as key to the many isolated finds of its elder relative, Leedsichthys. Estimated at just over 4.5m Standard Length, it might seem a little diminutive next to Leedsichthys (the smallest-known adult specimen, from the Star Pit excavation, has been estimated at 8m SL), but the size of individual elements is still impressive – pectoral fin 58cm instead of 1.36m of Ariston (Fig 2c); 28cm visible of L maxilla, whereas the ‘Big Meg’ specimen of Leedsichthys has one 69cm long; 6.3cm width of neurocranium, with again ‘Big Meg’ having a width of 11.5cm; a 31.5cm long R hyomandibula, as compared to 66.3cm in Ariston.

The occurrence of large, suspension-feeding pachycormids anywhere in the Cretaceous was only publicised for the first time last year, in conjunction with a number of colleagues (Friedman et al. 2010). In this paper, we highlighted a number of suspension-feeding pachycormids, both newly-described, and newly-re-identified. This featured one taxon, Bonnerichthys – again, named after the private collectors who found it – from the Upper Cretaceous (Coniacian to Maastrichtian) deposits of the Western Interior Seaway and Coastal Plain of the USA. Another Upper Cretaceous suspension-feeding pachycormid – Rhinconichthys – is from the Cenomanian of Kent, and it will be interesting to see how taxonomically similar Ebbo’s stratigraphically ‘adjacent’ Albian specimen (currently under study) ultimately proves to be.

The reliance of museums – and, therefore, the public – on private collectors has always been great. With the advent of the current economic crisis and the concomitant cut in institutional funding, that dependency is only going to intensify.

Acknowledgements

Thanks for image procurement above and beyond the call of duty go to Regina Fechner, Andy Mortlock and son, Bob Nicholls, Alan Dawn, Alison Longbottom and Luc Ebbo.

References

Leich, H (1967) Nach millionen jahren ans licht: Versteinerungen der Jurazeit ein bildband. Ott Verlag Thun, 180 pages.

Liston JJ (2006) From Glasgow to the Star Pit and Stuttgart: A short journey around the world’s longest fish. The Glasgow Naturalist 24: 59-71.

Liston JJ (2008) Leedsichthys des Vaches Noires au peigne fin. L’Echo des Falaises 12: 41-49.

Liston JJ (2010) The occurrence of the Middle Jurassic pachycormid fish Leedsichthys. Oryctos 9: 1-36.

Liston JJ and Noè LF (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: 236-252.

Liston, J.J. and Noè, L.F. (2008) ‘Old Bones’: The dinosaurs of Alfred Leeds. In R. Moody, E. Buffetaut, D. Martill and D. Naish (eds), Dinosaurs (and other extinct saurians) a historical perspective, 13–14. Abstracts of Meeting held on the 6-7 May 2008, Geological Society London. London. Geological Society London.