Brain Provides Clue to the Descendants of the Cambrian Anomalocaridid Lyrarapax unguispinus

An international team of scientists, including researchers from the University of Arizona have identified and mapped the brain in an anomalocaridid that swam in the ancient seas that existed in the Cambrian geological period.  Their study of the brain of this twelve centimetre long predator provides clues as to the taxonomic relationship that this extinct group has to extant members of the Animalia Kingdom.

The Brain of an Anomalocaridid

In addition, the remarkably well preserved fossil that is around 520 million years old, suggests that the brains of the anomalocaridids were relatively simple, the brains of their prey were, in many cases more complex.  This leads to the intriguing thought that the evolution of apex predators could have given a boost to the evolution of better senses and ultimately bigger and more sophisticated brains.

The scientific paper, published in the journal “Nature” describes for the first time, the brain of an anomalocaridid, a group of extinct, early members of the Arthropoda that evolved into the first group of animal super-predators known in the fossil record.  The largest specimens of Anomalocaris measure around a metre in length and it is now known that this group of nektonic predators survived into the Ordovician.

Anomalocaris

An Illustration of a Typical Anomalocaridid

Anomalocaris drawing. Picture credit: Everything Dinosaur.

Picture credit:  Everything Dinosaur

To view models and replicas of prehistoric invertebrates including Anomalocaris (whilst stocks last): CollectA Prehistoric Life Models.

Super Predator

An extensive analysis of the beautifully preserved fossils of a new to science, species of anomalocaridid predator discovered in Yunnan Province (China), suggests that these creatures have an affinity with the bizarre velvet worms (Onychophorans).  These strange little creatures are found in the southern hemisphere and they are classed in the taxon Panarthropoda.  Unlike true arthropods these creatures do not have an exoskeleton and they live in the undergrowth and leaf litter feeding on smaller animals such as insects and mites.

An Illustration of a Velvet Worm (Peripatus)

Peripatus – creatures like this may have been the first to walk on land.

Picture credit: BBC

The fossil material comes from the famous Chengjiang Formation (Yunnan Province), which rivals the Burgess Shale of British Columbia in terms of the variety of Cambrian fauna that is preserved.  First explored by Chinese palaeontologists in 1984, the members that make up this part of the Chengjiang Formation have preserved in exquisite detail ancient marine creatures.  The degree of fossil preservation is so good that even internal structures such as nervous systems can be studied.

One of the Fossils of the Newly Described L. unguispinus Showing Brain Morphology

This photograph and corresponding drawing show the flattened, fossilised trace of the brain of the world’s earliest known predator; the X-like structure in the head denotes the fossilised brain.

Picture credit: University of Arizona

The Fossilised Brain

The “X-shaped” structure seen clearly in the line drawing interpretation of the fossil denotes the fossilised brain.  Two dark round spots represent the optic ganglia with nerves that lead from the eye-stalks into the head.  The smaller, almond-shaped areas just in front would have supported the creature’s grasping appendage.  The main brain region is in front of the mouth, giving rise to two nerve cords leading down along the animal.

Commenting on the research, lead author of the scientific paper, Professor Nicholas Strausfeld (Director of Arizona University’s Centre for Insect Research) stated:

“It turns out the top predator of the Cambrian had a brain that was much less complex than that of some of its possible prey and that it looked surprisingly similar to a modern group of rather modest worm-like animals.”

Lyrarapax unguispinus

The new species has been named Lyrarapax unguispinus, this translates from the Latin to mean “spiny clawed lyre shaped predator”.  It is likely that this creature was an active predator hunting other invertebrates and perhaps preying on the recently evolved primitive, jawless vertebrates, the fore-runners of the first fish.

Lyrarapax Attacks a Shoal of Primitive Fish

Artist’s impression of Lyrarapax, one of the species of the world’s first predators, the anomalocaridids, chasing its possible prey, primitive fishes that also existed in the Cambrian.

Picture credit: Professor Nicholas Strausfeld/University of Arizona

Professor Strausfeld and his colleagues have made some remarkable discoveries amongst the Chengjiang biota, back in the autumn of 2013, Everything Dinosaur reported on the mapping of the brain and nervous system of a Cambrian arthropod, fossils of which had been recovered from the same location as the Lyrarapax fossil material.

To read more about this remarkable discovery: Mapping the Ancient Brains and Nervous Systems of Cambrian Arthropods.

By examining in minute detail the brain morphology of this long extinct species, the scientists were able to compare the neuroanatomy with extant velvet worms (Onychophorans).  The terrestrial velvet worm, such as Peripatus, has a simple brain located at the front of the mouth and a pair of ganglia, a group of nerve cells, located in the front part of the optic nerve and at the base of long, sensory feelers.

Similar Neuroanatomy to Extant Velvet Worms

The anomalocaridid fossil resembles the neuroanatomy of today’s Onychophorans (velvet worms) in several ways, according to Strausfeld and his collaborators. Onychophorans have a simple brain located in front of the mouth and a pair of ganglia – a collection of nerve cells – located in the front of the optic nerve and at the base of their long feelers.  Anomalocaridids do not have these feelers, but they do have a pair of grasping claws extending out from the front of their heads.

Professor Strausfeld explained:

“Surprise, surprise, that is what we also found in our fossil.  These top predators in the Cambrian are defined by just their single pair of appendages, these wicked-looking graspers, extending out from the front of their head.  These are totally different from the antennae of insects and crustaceans.  Such frontally disposed appendages are not found in any other living animals with the exception of the velvet worms.”

Study Suggests Velvet Worms are Descended from Anomalocaridids

A side-by-side comparison reveals the similarity between the brain of a living Onychophoran (green) and that of the anomalocaridid fossil Lyrarapax unguispinus (grey).

Picture credit: Professor Nicholas Strausfeld

The relatively simple brain structure of these large, apex predators may have driven the evolution of more sophisticated senses and brains in their intended prey.

Professor Strausfeld concluded:

“With the evolution of dedicated and highly efficient predators, the pressure was on other animals to be able to detect and recognize potential danger and rapidly coordinate escape movements.  These requirements may have driven the evolution of more complex brain circuitry.”

A Close up of the Head of Lyrarapax Showing a Powerful Grasping Claw

The grasping claw on this specimen can clearly be seen.

Picture credit: Peiyun Cong

Everything Dinosaur acknowledges the help of a University of Arizona press release in the compilation of this article.

Changyuraptor yangi – Let’s Not Get into Too Much of a Flap

And so on the 15th July, the paper on a new type of airborne dinosaur was published in the journal “Nature Communications”.  The world was officially introduced to Changyuraptor yangi or to interpret the genus name, “long feathered raptor”.  At about the size of a European Herring Gull (Larus argentatus), this newest member of the microraptorines, is the largest theropod dinosaur discovered to date with long pennaceous feathers attached to the hind limbs.  At an estimated weight of around three to four kilogrammes, it is three times heavier than the largest species of Microraptor – M. zhaoianus (if indeed the fossils discovered to date do indeed represent three different species and not a single species but with extensive intra-specific variation), and four times heavier than that extant gull we mentioned earlier.

Changyuraptor yangi

Changyuraptor has other claims to fame.  For example, its tail feathers are extremely long, measuring nearly thirty centimetres in length.  The longest tail feather is around 30% the length of the entire skeleton.

However, for us at Everything Dinosaur, the announcement of this fossil find comes as no real surprise.  The fossil material is from north-eastern China and it forms part of the amazing Jehol Biota which represents an Early Cretaceous ecosystem which has been preserved in strata that date from around 133 million years ago to 121 million years ago or thereabouts.  All the microraptorine fossil material comes from this part of the world and the fossilised fauna and flora portray a habitat that had distinct seasons with a temperate forest habitat interspersed with large bodies of freshwater and swamps.

The Jehol Biota

The area teemed with life and with the finding of one predatory dromaeosaurid dinosaur with aerodynamic abilities (Microraptor), finding other examples of dinosaurs filling this ecological niche was always likely.

These hunters may not have caught their prey on the wing, but they probably spent a great deal of their lives high up in the tree canopy living an arboreal existence and stomach content analysis from Microraptor specimens indicate that these dinosaurs, closely related to the likes of Velociraptor, ate small mammals, lizards and even primitive birds.  One poor unfortunate perching bird seems to have been swallowed whole.

An Illustration of Changyuraptor yangi (Silhouette of Person shows Scale)

“Four winged” terror.

Picture credit: S. Abramowicz

The international team of scientists behind the scientific paper, such as Luis M. Chiappe (Natural History Museum of Los Angeles County), Michael Habib (University of Southern California), Gang Han, Shu-An Ji, Xueling Liu and Lizhuo Han (Bohai University, Liaoning Province), in collaboration with colleagues based in New York and South Africa have described the beautifully preserved fossil material and then analysed this animal’s flight characteristics. Why, for example, did this “four-winged terror” have such long feathers on its tail?

The Holotype Fossil Material (C. yangi)

The slab (a) and the counter slab (b) of the holotype.

Picture credit: Nature Communications

Weighing Four Kilogrammes

At 1.32 metres in length and weighing close to four kilogrammes, taking to the air may not have been too much of a problem for our feathered friend here.  Especially if this dinosaur launched itself from the branches of trees and glided around.  However, controlling itself in flight and coming into land may have been somewhat more difficult for such a heavy, large-bodied animal.

The international research team examined the aerial competency of Changyuraptor and concluded that the tail may have acted as a pitch control structure, reducing air speed and helping to ensure a safe landing.  Those hind limbs with their feathers too, would have assisted with gliding and with the legs rotated down and underneath the body as it descended, then the feathers could have made effective air brakes, in a similar way to the “trousers” on Archaeopteryx.

To read an article on the feathered legs of Archaeopteryx: Feathers Evolved Before Flight – Archaeopteryx Had Feathered Trousers.

Dr Michael Habib (University of Southern California) stated:

“It makes sense that the largest microraptorines had especially large tail feathers, they would have needed the additional control.”

Dr Alan Turner of Stony Brook University (New York), a co-author of the paper added:

“Numerous features that we have long associated with birds in fact evolved in dinosaurs long before the first birds arrived on the scene.  This includes things such as hollow bones, nesting behaviour, feathers…and possibly flight.” 

Liaoning Province Fossils

Bone structure analysis undertaken concluded that this was a fully grown, mature animal that rivalled the largest pterosaurs known from Liaoning Province in size as it glided in the sky above this ancient Chinese landscape.  The holotype material was found back in 2012 and since its discovery the notion that flight preceded the origin of Aves has been consolidated.  Birds inherited flight characteristics from their near relatives the Dinosauria.  For the time being we shall give the last word to Luis Chiappe:

“This new fossil documents that dinosaur flight was not limited to very small animals but to dinosaurs of a more substantial size.  Clearly far more evidence is needed to understand the nuances of dinosaur flight but Changyuraptor is a major leap in the right direction.”