Stunning fossils of Cambrian nectocaridids solves a half-a-billion-year-old evolutionary puzzle.  Fossil material excavated from the Sirius Passet site in North Greenland has enabled palaeontologists to identify these ancient marine invertebrates as early descendants of chaetognaths (arrow worms).  It had been proposed that these animals were a type of cephalopod.  Cephalopods are marine molluscs with tentacles and a prominent head.  Living cephalopods include cuttlefish, octopi and squid.  The extinct ammonites and belemnites were cephalopods.

This significant discovery rewrites part of the story of the Cambrian Explosion. It shows arrow worms descended from complex predators, not simple marine organisms.

Life reconstruction of Nektognathus, swimming in the Cambrian Sea. It is depicted as a nektonic predator. Picture credit: Bob Nicholls.

Picture credit: Bob Nicholls

The illustration of Cambrian life (above) was created by acclaimed palaeo-reconstruction artist Bob Nicholls.  Bob has recently been collaborating with Everything Dinosaur in the production of museum quality prehistoric animal models – Everything Dinosaur Evolution.

To learn more about these remarkable, scientifically accurate figures: Everything Dinosaur Evolution Figures.

Studying Cambrian Nectocaridids

The research team included palaeontologists from the University of Bristol, the University of Copenhagen, and the Korean Polar Research Institute. Their work builds on nine years of expeditions to Sirius Passet, a site famous for exceptional soft-tissue fossil preservation from 518 million years ago (Stage 3 of the Cambrian).

Co-author of the study, Dr Jakob Vinther, Associate Professor in Macroevolution at the University of Bristol commented:

“Sirius Passet is a treasure trove of fossils from the Cambrian Explosion. We not only find delicate soft-bodied fossils but also their digestive systems, musculature and sometimes even their nervous system.”

Research first published in 2009 examining fossils from the famous Burgess Shale deposits of British Columbia (Canada), linked nectocaridids to cephalopods.  However, some invertebrate palaeontologists remained sceptical.

Dr Vinther explained:

“Around 15 years ago a research paper, based on fossils from the famous Burgess Shale, claimed nectocaridids were cephalopods. It never really made sense to me, as the hypothesis would upend everything we otherwise know about cephalopods and their anatomy didn’t closely match cephalopods when you looked carefully.”

Field team members became excited as they found twenty-five new specimens of Cambrian nectocaridids in the Sirius Passet deposits. These are the first nectocaridids unearthed from the Sirius Passet locality. Evidence of nervous systems were preserved in some specimens.

A fossil specimen of Nektognathus discovered at Sirius Passet (northern Greenland). Picture credit: University of Bristol.

Picture credit: University of Bristol

Identifying the Ventral Ganglion

The team discovered nectocaridids with parts of their nervous system preserved as paired mineralised structures.  This new evidence helped to confirm the phylogeny of these ancient animals. Arrow worm fossils with preserved ventral ganglia – a unique nerve structure seen in modern chaetognaths (arrow worms) were also found.

Co-author of the paper, Dr Tae-Yoon Park from the Korean Polar Institute stated:

“These fossils all preserve a unique feature, distinct for arrow worms, called the ventral ganglion.”

The discovery of this structure confirms the evolutionary link between nectocaridids and arrow worms.

The holotype specimen of Nektognathus from Sirius Passet. Picture credit: Tae-Yoon Park.

Picture credit: Tae-Yoon Park

The authors of the study have erected a new nectocaridid taxon Nektognathus evasmithae. The species name honours Professor Eva Smith, the first female professor of law in Denmark and renowned human rights advocate. Dr Vinther commented that N. evasmithae was a smart and stealthy fighter, just like the Danish advocate.

Dr Park added:

“We now had a smoking gun to resolve the nectocaridid controversy. Nectocaridids share a number of features with some of the other fossils that also belong to the arrow worm stem lineage. Many of these features are superficially squid-like and reflect simple adaptations to an active swimming mode of life in invertebrates, just like whales and ancient marine reptiles end up looking like fish when they evolve such a mode of life.”

The holotype specimen of Nektognathus from Sirius Passet imaged with Electron Probe microanalysis for its carbon content. Picture credit: Mirinae Lee and Chankun Park.

Picture credit: Mirinae Lee and Chankun Park

Cambrian Nectocaridids – Dynamic, Nektonic, Agile Predators

This surprising discovery means the rather simple marine arrow worms had ancestors with much more complex anatomies and a predatory role higher up in the food chain. Cambrian nectocaridids had camera-type eyes, long antennae, and streamlined bodies for active hunting.  In contrast, extant arrow worms have eyes that are sensitive to light but are not thought to have effective vision.  The researchers conclude that the ancestors of today’s arrow worms were nektonic predators.  They filled an ecological niche similar to living squid.  Although, squids evolved much later.  Preserved gut contents indicate that Nektognathus evasmithae fed on the swimming arthropod Isoxys.

Dr Vinther commented:

“We can therefore show how arrow worms used to occupy a role much higher in the food chain. Our fossils can be much bigger than a typical living arrow worm and combined with their swimming apparatus, eyes and long antennae, they must have been formidable and stealthy predators.”

A photograph of a modern chaetognath (arrow worm) from Antarctica. Picture credit: Tae-Yoon Park.

Picture credit: Tae-Yoon Park

This study gives us a new view of Cambrian nectocaridids. Far from being early squids, they were fierce predators with an advanced anatomy.  This study helps palaeontologists to better understand Cambrian marine ecosystems.

Everything Dinosaur acknowledges the assistance of a media release from the University of Bristol in the compilation of this article.

The scientific paper: “A fossilised ventral ganglion reveals a chaetognath affinity for Cambrian nectocaridids” by Jakob Vinther et al published in Science Advances.

The award-winning Everything Dinosaur website: Prehistoric Animal Models and Figures.

Researchers have named a new genus and species of rhabdodontomorph ornithopod from fossil material found in southeastern France. The dinosaur has been named Obelignathus septimanicus. The genus name was inspired by the French cartoon strip character Obélix from the Asterix the Gaul series, and the Latin word for jaw. Obélix is known for his exceptional strength and robust appearance. This is a reference to the unusually robustly built holotype dentary.

The researchers conclude that rhabdodontomorphs were more diverse in Europe than previously recognised.

A silhouette of the recently described 2025 ornithopod Obelignathus septimanicus from the Grès à Reptiles Formation in southern France. Scale bar equals 50 cm. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Obelignathus septimanicus

The origins and early diversification of the Ornithopoda is poorly understood.  For instance, the phylogeny of the Rhabdodontidae, a family of medium-sized ornithischian dinosaurs known solely from the Upper Cretaceous of Europe remains unresolved.  Current studies suggest eight or nine species, all of which are known from the upper Campanian to lower Maastrichtian of Europe.

Writing in the journal “Scientific Reports”, the researchers compiled a novel dataset made up from a morphological assessment and measurements of rhabdodontomorph dentaries.  The robust dentary (specimen number MDE D30) when first described in 1991 (Buffetaut and Le Loeuff), was thought to represent the genus Rhabdodon. However, it was sufficiently different to warrant its own species – Rhabdodon septimanicus. This latest analysis places R. septimanicus well outside the genus Rhabdodon and hence, a new genus has been erected.

Obelignathus is found to be a clear morphological outlier among European rhabdodontomorphs.  The research team members conclude that further large-scale studies are required to clarify the taxonomy of European rhabdodontomorphs.  These results indicate that this group of ornithopods exhibit greater diversity than currently recognised.  Several taxa appear to be coeval.

In common with most other rhabdodonts Obelignathus was relatively small. It is thought to have measured under three metres in length.

A New Herbivore from Late Cretaceous France

The find underscores southern France’s importance as a hotspot for Late Cretaceous dinosaur diversity. As fieldwork continues, Obelignathus offers a glimpse into the complex web of life that once thrived on the European archipelago.

Everything Dinosaur acknowledges the assistance of the open access scientific paper in the compilation of this article.

The scientific paper: “Exploring the diversity and disparity of rhabdodontomorph ornithopods from the Late Cretaceous European archipelago” by Łukasz Czepiński and Daniel Madzia published in Scientific Reports.

For models of ornithopods and other dinosaurs: Dinosaur Models.

A remarkable fossilised ichthyosaur flipper has provided new insights into the hunting behaviour of ancient marine reptiles.  The study, published in the journal “Nature” reveals that the giant ichthyosaur Temnodontosaurus trigonodon relied on stealth whilst hunting in the darkness. The metre-long front flipper was equipped with flow control structures that probably served to suppress self-generated noise as this megapredator hunted in dimly lit pelagic environments.

Life reconstruction of the giant Jurassic ichthyosaur Temnodontosaurus trigonodon hunting in the depths. The artwork highlights the winglike flipper, and the unusual structures observed in the fin. Picture credit: Joschua Knüppe.

Picture credit: Joschua Knüppe

Temnodontosaurus trigonodon Flipper Study

Temnodontosaurus was a large ichthyosaur. Size estimates vary, however, some individuals may have exceeded ten metres in length. Researchers have named several species within the genus. While fragmentary remains of unusual “fish lizards” had previously been excavated along the Dorset coast, it was the discovery of a metre-long skull by Joseph Anning at Lyme Regis in the autumn of 1811—followed by vertebrae and ribs found by 13-year-old Mary Anning in 1812 that prompted the first formal scientific study and description of an ichthyosaur. More than two centuries later, these enigmatic marine reptiles continue to yield unexpected insights and discoveries.

The fossilised flipper (specimen number SSN8DOR11) was collected from a temporary exposure of dark, laminated limestone (Lower Toarcian Posidonia Shale) of southwestern Germany. The partial front flipper preserves soft tissue structures and has been studied by an international team of researchers led by Dr Johan Lindgren from Lund University in Sweden.  The research was undertaken in collaboration with Dr Dean Lomax, an 1851 Research Fellow at the University of Bristol, who has been working on the fossil for about six years. Dr Lomax is one of the world’s leading ichthyosaur experts.

Dr Dean Lomax and Dr Johan Lindgren, together with fellow researcher Sven Sachs, examining one part of the Temnodontosaurus trigonodon flipper at Lund University, Sweden. Picture credit: Katrin Sachs.

Picture credit: Katrin Sachs

Dr Lindgren, who has pioneered research into marine reptile soft tissues commented:

“The wing-like shape of the flipper, together with the lack of bones in the distal end and distinctly serrated trailing edge collectively indicate that this massive animal had evolved means to minimise sound production during swimming. Accordingly, this ichthyosaur must have moved almost silently through the water, in a manner similar to how living owls—whose wing feathers also form a zigzag pattern—fly quietly when hunting at night. We have never seen such elaborate evolutionary adaptations in a marine animal before.”

The remarkable fossil flipper specimen (SSN8DOR11) shown left, under UV light (centre) and in a line drawing (right). Picture credit: Randolph G. De La Garza, Martin Jarenmark and Johan Lindgren.

Picture credit: Randolph G. De La Garza, Martin Jarenmark and Johan Lindgren

“Silent Swimming”

Although there are many exceptional ichthyosaur specimens with soft-tissue preservation, most soft tissues are associated with the fossilised remains of much smaller dolphin-sized species.  This is a remarkable discovery, it represents the first-ever soft tissues associated with a large-bodied ichthyosaur. In addition, the research team have identified unique structures never observed before in an aquatic animal.  The crenulated trailing edge of the wing-shaped flipper being reinforced by novel, mineralised, rod-like structures.  The researchers have named these structures “chondroderms”.

Dr Dean Lomax, who is also a palaeontologist at the University of Manchester, said:

“The first time I saw the specimen, I knew it was unique. Having examined thousands of ichthyosaurs, I had never seen anything quite like it. This discovery will revolutionise the way we look at and reconstruct ichthyosaurs (and possibly also other ancient marine reptiles) but specifically soft-tissue structures in prehistoric animals.”

Novel cartilaginous integumentary structures. To the left, light micrograph of the crenulated trailing edge in SSN8DOR11. Note that each serration is supported by a centrally located chondroderm. To the right, magnified image of a distal chondroderm. Picture credit: Randolph G. De La Garza, Martin Jarenmark and Johan Lindgren.

Picture credit: Randolph G. De La Garza, Martin Jarenmark and Johan Lindgren

The team postulate that this huge predator relied on underwater stealth, or “silent swimming” while hunting in the depths, in much the same way that owls as nocturnal predators have almost silent flight.

Eyes as Big as Footballs

Temnodontosaurus had the largest eyes of any vertebrate known.  The eye sockets of some specimens are more than twenty-five centimetres in diameter.  These huge eyes lend further support to the theory that Temnodontosaurus hunted under low-light conditions, either at night or in deep waters.

Spectacular, 183-million-year-old soft-tissue fossil (SSN8DOR11; Paläontologisches Museum Nierstein, Nierstein, Germany): an isolated wing-like front flipper of the giant predatory ichthyosaur Temnodontosaurus (T. trigonodon). Photograph (left) and shown under UV light (centre). Line drawing (right) providing a representation of the metre-long flipper. Picture credit: Randolph G. De La Garza, Martin Jarenmark and Johan Lindgren.

Picture credit: Randolph G. De La Garza, Martin Jarenmark and Johan Lindgren

The remarkable fossilised flipper was discovered by fossil collector Georg Göltz, a co-author on the new study. Amazingly, Georg made the find entirely by chance whilst looking for fossils at a temporary exposure at a road cutting in the municipality of Dotternhausen, Germany. The fossil consists of both the part and counterpart (opposing sides) of almost an entire front flipper.  Georg continued to look for more remains, but no other fossil material was found.

As the proximal part of the fin is absent, it has been speculated that the flipper could have been ripped off by an even larger ichthyosaur.  The specimen was shown to palaeontologist and study co-author Sven Sachs (Natural History Museum, Bielefeld).  Dr Sachs immediately recognised the rarity of the find.

A multidisciplinary research team employed a variety of sensitive imaging, elemental and molecular analyses to examine the unique preserved structures. This involved high-end techniques such as synchrotron radiation-based X-ray microtomography at the Swiss Light Source SLS at PSI and Diamond Light Source, time-of-flight secondary ion mass spectrometry and infrared microspectroscopy, along with the reconstruction of a virtual model using computational fluid dynamics.

To recreate the stealth hunting behaviours of a marine reptile that lived more than 180 million years ago is remarkable. Furthermore, by studying the fin morphology, scientists could find ways of reducing our impact on modern marine soundscapes.

Going Back to Mary Anning

For Dr Dean Lomax, this astonishing study harks all the way to back to the days of pioneering palaeontologist Mary Anning and her older brother Joseph.

He stated:

“In a weird way, I feel that there is a wonderful full-circle moment that goes back to Mary Anning showcasing that even after two hundred years, we are still uncovering exciting and surprising finds that link back to her initial discoveries.”

Dr Lomax added:

“The fossil provides new information on the flipper soft tissues of this enormous leviathan. It has structures never seen in any animal, and reveals a unique hunting strategy thus providing evidence of its behaviour, all combined with the fact that its noise-reducing features may even help us to reduce human-made noise pollution. Although I might be a little bias, in my opinion, this represents one of the greatest fossil discoveries ever made.”

Everything Dinosaur acknowledges the assistance of a media release from the University of Bristol in the compilation of this article.

The scientific paper: “Adaptations for stealth in the wing-like flippers of a large ichthyosaur” by Johan Lindgren, Dean R. Lomax, Robert-Zoltán Szász, Miguel Marx, Johan Revstedt, Georg Göltz, Sven Sachs, Randolph G. De La Garza, Miriam Heingård, Martin Jarenmark, Kristina Ydström, Peter Sjövall, Frank Osbæck, Stephen A. Hall, Michiel Op de Beeck, Mats E. Eriksson, Carl Alwmark, Federica Marone, Alexander Liptak, Robert Atwood, Genoveva Burca, Per Uvdal, Per Persson and Dan-Eric Nilsson published in the journal Nature.

Visit the website of the award-winning palaeontologist and author Dr Dean Lomax: Palaeontologist Dr Dean Lomax.