An Insight on the Feeding Behaviour of Small Crocodyliforms – Watch out Hypsilophodonts You are on the Menu!

There have been a number of scientific papers published recently that provide information on the feeding habits of apex crocodyliform predators of the Late Cretaceous such as Deinosuchus.  Since modern day crocodiles and alligators attack and kill large mammalian vertebrates and are regarded as apex predators in their environments, it has long been thought that extinct crocodiles such as the twelve-metre-long Deinosuchus were also apex predators.  Instead of ambushing mammals when they came to a water source for a drink, (there are no large mammal species known from the Campanian/Maastrichtian fossil record), fearsome reptiles such as Deinosuchus are thought to have tackled dinosaurs.

Even a tyrannosaurid would have had to watch its step close to water with the possibility of being grabbed by a Deinosuchus, a type of crocodile getting on for twice the size of a Nile crocodile.

A Model of the Fearsome Late Cretaceous Predator Deinosuchus

The Carnegie Collectibles Deinosuchus crocodile model.

However, very little is known about interactions between predator and prey species when it comes to smaller types of Mesozoic crocodile and smaller types of potential prey.  Thanks to some new research by a team of American scientists evidence of a slightly smaller scale predator/prey relationship has been discovered.  It looks like small crocodyliform genera or indeed immature specimens of larger taxa may have fed on small types of dinosaur, or possible juveniles and babies of larger species.

Crocodyliforms Feeding on Small Dinosaurs

Writing in the Public Library of Science (Biology) publication Dr Clint Boyd (Department of Geology and Geological Engineering, South Dakota School of Mines and Technology, South Dakota, USA) and his colleagues have outlined research into a number of fragmentary dinosaur bones that show evidence of bite marks from crocodyliforms.  Moreover the jumbled and broken bones collected seem to represent a single ornithischian genus and an as yet, unknown genus to boot.  It looks like man-sized Cretaceous crocodiles fed on small dinosaurs and the remains of their dinner could well result in the erection of a new genus of hypsilophodontid dinosaur genus.

The Tiny and Fragmentary Dinosaur Bones – Ornithischian Dinosaur

Tiny dinosaur bones show evidence of crocodyliform bite marks.

Picture credit: South Dakota School of Mines and Technology

The fragmentary fossils were found in the Upper Cretaceous Kaiparowits Formation at four separate locations along the Grand Staircase Escalante-National Monument in southern Utah, an area famous for its dinosaur fossil finds.  The fossils are believed to date from the Campanian faunal stage of the Cretaceous and they are estimated to be around 75 million years old.

During this time in the Late Cretaceous, this region was a lowland plain, criss-crossed by many rivers.  The warm, humid climate created ideal conditions for lush plant growth and there was a rich and diverse dinosaur dominated ecosystem, with many types of crocodyliform also present.

Crocodyliforms Feeding

The broken dinosaur bones show bite marks and puncture wounds similar to those found on the bones of mammals that have been fed upon by extant American alligators.  The fossil are broken, many have been snapped off at the joints.  This could be characteristic of the damage to bones caused by the “crocodile roll” method of feeding, whereby extant crocodiles tear their victims to pieces by grabbing onto the corpse with their strong jaws and then rapidly rotating their bodies.

Studying the Fossil Material

The fossil material represents the bodies of several individual dinosaurs, all roughly 1.2 metres in length.  The fossils include elements of the limb bones and vertebrae, along with parts of the skull and the lower jaw.  As well as bite marks on the bones, the American research team discovered a broken Crocodyliform tooth embedded in a thigh bone (femur).

It can be speculated that baby ornithopod dinosaurs stayed together in groups when young to give themselves some protection, the nesting site may have been nearby and the two-metre-long crocodyliform predators lay in wait ready to ambush any unwary young herbivore that came too close.  The abundance and the close proximity of the fossil finds suggests that these relatively small crocodiles were actively targeting the hypsilophodonts, deliberately congregating close to areas where there were lots of dinosaur juveniles and actively selecting to feed upon these animals.

Although, only very small in size and hardly likely to feature in a major dinosaur exhibit in a museum, these fragments of bone are very significant as they are helping palaeontologists to piece together the complex food chain and diverse ecosystem in this Campanian faunal age environment.  It seems that life for a young hypsilophodontid in the Late Cretaceous was particularly hazardous, they would have had to look out for tyrannosaurs and dromaeosaurs as well as having to contend with predatory crocodiles.

A Drawing of What the Hypsilophodontid Dinosaur May Have Looked Like

Was this a meal for a Late Cretaceous crocodile?

Picture credit: Everything Dinosaur

The researchers have concluded that the chewed up bones are not the work of a much larger crocodile species.  If that had been the case, the bones would simply have been swallowed whole, leaving behind much fewer traces of the dinosaurs that it preyed upon.

Dr Boyd commented:

“It’s not often that you get events from the fossil record that are action-related. While you generally assume there was probably a lot more interaction going on, we didn’t have any of that preserved in the fossil record yet.  This is the first time that we have definitive evidence that you had this kind of partitioning, of your smaller crocodyliforms attacking the smaller herbivorous dinosaurs.”

Recently, Rebor have introduced a range of Deinosuchus figures.  To view this range of crocodyliforms (whilst stocks last): Rebor Models and Replicas.

Idaho State University Scientists Solve Spiral-Toothed Shark Puzzle

A team of researchers have got to the bottom of a fishy puzzle that had palaeontologists previously in a spin.  Fossils of an ancient cartilaginous fish known as Helicoprion show a whorl of spiral, saw-like teeth but up until now scientists were unsure where on this prehistoric fish the teeth whorl was located.  Was this strange toothed structure inside the jaw or outside, did it actually belong in the mouth at all, perhaps it formed part of a defensive structure located on the dorsal fin?  After all, the fossil record does contain some remarkable fossils of sharks, for example, Stethacanthus from the Late Devonian with a large projection known as the “ironing board” on its back.

Prehistoric Fish

Using their unrestricted access to the Helicoprion spiral-toothed fossils at the Idaho State Museum of  Natural History the research team were able to examine a number of beautifully preserved fossils.  This museum has the largest public collection of Helicoprion teeth fossils in the world and a number of these specimens have been collected from Early Permian strata exposed in Idaho.  The actual body shape of this large, prehistoric predator is open to speculation as since the skeleton of this animal was made of cartilage, very few fossils other than those of the strange teeth have been found.  It had been thought that Helicoprion was a nektonic and very active predator, patrolling the water column in a similar way to a lot of extant shark genera.

Previously, scientists had thought that this creature was a type of shark, however, this new research links this 270-million-year-old fish to another group of fish with cartilaginous skeletons.

A Scale Drawing of Heliocoprion

As Everything Dinosaur prepares for the arrival of Haylee the Helioprion model from PNSO a scale drawing of this Permian fish has been commissioned. Picture credit: Everything Dinosaur.

Picture credit Everything Dinosaur

Helicoprion

A large number of Helicoprion fossils were subjected to intense examination and analysis including computerised tomography – a process whereby high-powered X-rays bombard a fossil and provide non-destructive, three-dimensional images that reveal hidden aspects of anatomical structure.  One such fossil studied, measured over twenty-three centimetres in length and contained the remains of one hundred and seventeen individual, triangular teeth.  However, unlike most of the other known Helicoprion fossil material, this specimen had preserved impressions which showed the placement of parts of the cartilage skeleton.

Using the detailed computer images that the CT scans produced the team were able to deduce that the spiral teeth were located at the back of the jaw, the teeth did not project forwards from the lower part of the mouth, nor was this structure located on another part of the fish.  Dr Leif Tapanila of the department of Geosciences at Idaho State University and his colleagues have been able to clear up this mystery surrounding the whorl of teeth.

Tooth Whorl Analysis in Helicoprion

Helicoprion specimen IMNH 37899, preserving cartilages of the mandibular arch and tooth whorl. (a) Photograph and (b) surface scan of fossil. Picture credit: Tapanila et al in Biology Letters.

Picture credit: Tapanila et al

He stated:

“We were able to answer where the set of teeth fit in the animal.  They fit in the back of the mouth, right next to the back joint of the jaw.  We were able to refute that it might have been located at the front of the jaw.”

Studying the Wear Pattern

Analysis of the wear pattern on the teeth also provided the researchers with an insight into what this predator may have eaten as it swam in the Permian seas.  It is unlikely that these teeth were used to crush hard bodied creatures such as shellfish or marine snails.  It is more likely that Helicoprion tackled soft bodied members of the Phylum Mollusca such as cephalopods (squid and octopi).

A Scientific Paper

The paper, published in the prestigious academic journal “Biology Letters” provides further information on how the scientists think the jaws actually worked.  The jaw was able to produce a rolling-back and slicing action, ideally suited to tackling soft and slippery prey.  The research has also suggested that Helicoprion was not a type of shark, but that it is more likely closely related to the extant rat fish, making it a basal, but very specialised member of the Holocephalan group called the Euchondrocephali.

Dr Tapanila added:

“New CT scans of a unique specimen from Idaho show the spiral of teeth within the jaws of the animal, giving new information on what the animal looked like and how it ate.”

The teeth may be very shark-like with their triangular shape and serrated edges, but evidence from the CT scans indicates that Helicoprion should be classified as a Holocephalan.

The Idaho Fossil Specimen

The Idaho fossil specimen suggests an animal around 4.2 metres in length but other Helicoprion teeth fossils indicate fish that could have reached lengths in excess of 7 metres.  The work of the scientists will form the basis of a new Helicoprion exhibit that is to open shortly at the Idaho Museum of Natural History.

It seems that this creature was a specialised predator from the end of the Permian onwards the top predator niches in the world’s oceans were to be mainly occupied by sharks, before the evolution of the larger Teleost fish challenged the shark’s dominant position.

Helicoprion and Prehistoric Fish Models

Those clever people at Safari Ltd introduced a Toob (a tube containing models), called “Prehistoric Sharks” a couple of years ago now.  The models show different types of ancient cartilaginous fish including the likes of Stethacanthus and a model of Helicoprion.   This set of ten prehistoric fish has proved popular and it is fascinating to see how the interpretation of Helicoprion by the design team at Safari Ltd matches up against the latest scientific data.

The Helicoprion Model from the “Prehistoric Sharks” Toob

Model play set includes Helicoprion replica.

Picture credit: Everything Dinosaur

The snout may be somewhat elongated and the body perhaps a touch more streamlined, that of an active predator in the mid water column but the front jaw does resemble quite closely the latest scientific interpretation.

Helicoprion Up Close

A whorl of triangular teeth in this model’s lower jaw.

Picture credit: Everything Dinosaur

The morphology of this Early Permian predator may not be known but credit must be given to the design team at Safari Ltd for creating a replica that does have some similarities to the illustrations provided in the scientific paper.  It remains uncertain whether this shark was an active, fast swimming hunter or whether it lived close to the sea floor and had a more sedentary habit, but at least the mystery regarding its remarkable dentition (teeth) seems to have been solved.

PNSO Helicoprion Replica

PNSO Haylee the Helicoprion replica. The stunning emerald eye on the model is reminiscent of the eye of a Chimaera such as the deep water Rabbit Fish (Chimaera monstrosa) to which Helicorprion is distantly related.

PNSO have released a superb replica of this iconic prehistoric fish. To view the range of PNSO prehistoric animal models and figures available from Everything Dinosaur: PNSO Age of Dinosaurs Models.

Everything Dinosaur acknowledges the assistance of a press release from Idaho State University in the compilation of this article.

The scientific paper: “Jaws for a spiral-tooth whorl: CT images reveal novel adaptation and phylogeny in fossil Helicoprion” by Leif Tapanila, Jesse Pruitt, Alan Pradel, Cheryl D. Wilga, Jason B. Ramsay, Robert Schlader and Dominique A. Didier published in Biology Letters.

Fossils Provide Evidence of How Oviraptorids Grew Up

The bird-like oviraptorids which are known mainly from Upper Cretaceous strata from Mongolia and China are a very specialised group of dinosaurs that belong to the Suborder theropoda.  Despite a number of recent fossil discoveries, palaeontologists have still much to learn about these dinosaurs.  However, the discovery of a large number of oviraptorid specimens including five juveniles has helped scientists to erect a new genus and to learn a little about how these dinosaurs grew from babies into adults.

New Oviraptorid Dinosaur

The newest member of the Oviraptoridae is represented by the smallest specimens of Oviraptors discovered to date, the five individual specimens measure between 25 cm and 50 cm in length.  This newly discovered dinosaur has been named Yulong mini, the fossils were excavated from the Qiupa Formation of Upper Cretaceous strata from the Henan Province (eastern China).  The geological age of the Qiupa Formation is debated.  However, the presence of a number of dinosaur fossils including oviraptorids, dromaeosaurs and ornithomimids indicate that this strata was most probably laid down towards the very end of the Cretaceous period.

The name of this new dinosaur, is derived from the Chinese name for Henan Province coupled with the Chinese word for dragon and the specific name refers to the tiny size of these reptiles, so the name translates as “tiny dragon from Henan”.

Fossils of the New Oviraptorid Y. mini

New dinosaur genus – Yulong mini.

Picture credit: Junchang Lu (lead author)

Yulong mini

The baby dinosaurs are the subject of a scientific paper published in the journal “Naturwissenschaften”.  Chinese researchers from the Henan Geological Museum and the Chinese Academy of Sciences wrote this paper in conjunction with the Canadian palaeontologist Phil Currie, who has worked extensively on Late Cretaceous Theropod dinosaurs from this part of the world.

Writing about the discovery, lead author Junchang Lu commented that:

“These dinosaurs looked like chickens with a tail.  Their behaviour was probably very similar to that of a modern bird.  When compared to primitive Oviraptorids such as Caudipteryx, Yulong should be feathered, although no evidence of feathers were found due to the poor preservation condition of the fossil material and the coarse characteristics of the surrounding matrix.”

Several dinosaur specimens were found at this location, but these juvenile dinosaurs perhaps represent the most important vertebrate fossils found to date as they permit palaeontologists to piece together information about how these dinosaurs grew.  A number of ontogenetic characteristics have been identified helping scientists to understand how these creatures matured into adult animals.  The skulls are not yet fully fused and the babies do show different body proportions in comparison with adult oviraptorids.

Limb Proportions

Intriguingly, the hind limb proportions (ratio of upper leg bones to lower leg bones) femur: tibia/fibia remain constant in oviraptorids.  The younger dinosaurs have the same hind limb proportions as older animals.  This suggest that these dinosaurs were not particularly fast runners and may have a had a much more sedentary habit.  It is unlikely that these types of dinosaur pursued and fed upon animals roughly equal in size to themselves.

A number of adult specimens were also found at this site, although they were not found in close association with the chicken-sized juveniles.  It can be speculated that as the babies were found apart from the adults, the youngsters may have been very independent from birth – perhaps an indication of precocial behaviour.  Precocial offspring are born or hatched as relatively well-developed animals that show a high degree of independence from the adult animals.  Many types of modern bird show this type of behaviour.

To view models and replicas of oviraptorids and other feathered theropods: Wild Safari Wild Dinos Models and Figures.

The diet of these creatures remains uncertain.  Studies of the skull and jaws of Y. mini when related to the hind limb proportions which indicate a more sedentary lifestyle, suggest that these oviraptorids may have been herbivorous feeding on leaves, ferns and even flowers and fruit.  However, the bite force calculated from measurements of the jaw size and muscle area of the juveniles is still considerable and it is not possible to rule out that these dinosaurs may have also eaten small animals such as lizards, mammals and even younger members of their own species.

Perhaps this is another reason why the babies tended to keep out of the way of the adults.

The scientific paper: “Chicken-sized oviraptorid dinosaurs from central China and their ontogenetic implications” by Junchang Lü, Philip J. Currie, Li Xu, Xingliao Zhang, Hanyong Pu and Songhai Jia published in Naturwissenschaften.