A Polar Dromaeosaurid – Boreonykus certekorum

Picking over the carcases of the remnants of a herd of pachyrhinosaurs some seventy-two and a half million years ago was a small, theropod dinosaur named Boreonykus (B. certekorum), the scene, taking place in the high latitudes of northern Canada has been pieced together after painstaking research by two famous palaeontologists who have collaborated on a number of projects helping to increase our understanding of the lives and behaviours of dinosaurs that lived in high latitudes, the so called “polar dinosaurs”.

Polar Dromaeosaur

Publishing in the open access on line journal “The Journal of Vertebrate Paleontology”, please excuse the American spelling of palaeontology, scientists Philip Currie and Phil Bell report on the new dromaeosaurid material described from an extensive horned dinosaur bonebed located at Pipestone Creek, near the city of Grande Prairie (Alberta, Canada).  This dog-sized little theropod has been tentatively assigned to the Velociraptorinae “wing” of the Dromaeosauridae (no pun intended), thus making Boreonykus potentially a close relative of the famous Velociraptor from Asia.

A Pair of Boreonykus Dinosaurs Feast on the Carcase of a Pachyrhinosaurus (P. lakustai)

A pair Boreonykus feeding on the corpse of a Pachyrhinosaurs lakustai.

Picture credit: Canadian Press

Polar Dinosaurs

Australian Phil Bell (School of Environment and Rural Science at the University of New England), has worked on a number of polar dinosaurs, including several known from Australia, which, for much of the Cretaceous would have been part of high latitude environments in the Southern Hemisphere, so it could be said that Dr Bell has researched dinosaurs at the opposite ends of the Earth.  Isolated teeth had been found in association with the fossilised bones of the horned dinosaur Pachyrhinosaurus lakustai back in 1988, but they were thought to have been shed by other feeding, small-bodied theropods that had already been scientifically described.

Previous studies had concluded that these small theropod fossils found in the extensive Pipestone Creek bonebed belonged to Saurornitholestes langstoni or possibly Dromaeosaurus albertensis.  However, when more fossil material was found in 2012 including a portion of the skull (the frontal), scientists began to realise that the teeth and isolated bone fragments caught up in the huge plaster jackets of the giant Pachyrhinosaurus excavations, might just be something entirely new.

Comparison of Three Frontal Bones of Members of the Dromaeosauridae

The angle of the frontal bone in relation to the supratemporal ridges led to a new dinosaur.

Picture credit: The Journal of Vertebrate Paleontology with additional annotation by Everything Dinosaur

Skull Bone Provides Vital Clue

It was when the frontal bone from the Pipestone Creek bonebed was compared to the frontal bones of Saurornitholestes and Dromaeosaurus that the researchers noticed a vital difference.  The angle between the frontal and the supratemporal ridges on the skull was much more acute.  This suggested that the theropod material found did represent a new genus of small, agile hunter.

The picture above shows a comparison of dromaeosaurid frontal bones (dorsal view).  The angles between the supratemporal ridges are given.  The fifty-five degree angle for the frontal assigned to B. certekorum is noticeably smaller.

Phil Bell and the Polar Dromaeosaur

Commenting on the study, Phil Bell explained that the frontal was the most important bone, that helped to clinch what type of animal it was and led to the erection of a new genus.

Dr Bell added:

“Its [Boreonykus] closest ancestors were from Mongolia, so this species probably crossed the land bridge from northern Asia to North America.  The first bones were discovered in 1988 and laid unstudied in a museum in Alberta for 25 years.  We then started to turn up a few more bones from the very same spot in 2012, so that reinvigorated interest.  Although we don’t have the whole skeleton, we know, based on parts of the skeleton, that it belonged to this type of dinosaur.  The raptors’ skin was probably feathered to keep them warm in the cold dark winters in north Canada.”

The Sickle-Claw from the Second Toe of the Left Hind Foot

The killing toe claw of the “raptor” Boreonykus. Scale bar = 1 centimetre.

Picture credit: The Journal of Vertebrate Paleontology

Boreonykus certekorum

The genus name Boreonykus is a reference to the modern day boreal forest where the type specimen was found and “onychos” is from the Greek meaning claw.  The species name honours Certek Heating Solutions and the Barendregt family of Wembley, Alberta, who have sponsored the field work and supported efforts to record and preserve the fossil fauna of this part of Alberta.

More than 99% of all the fossil material recovered from the Pipestone Creek bonebed has been assigned to the centrosaurine Pachyrhinosaurus (P.  lakustai), some fragmentary Edmontosaurus fossils may have also been found (we think) along with evidence of other theropods.  The bonebed is very dense and there are up to two hundred bones per square metre, the other theropod material found to date consists of shed teeth assigned to Troodon and indeterminate tyrannosaurids.

Two Shed Tooth Crowns from the Pipestone Creek Site Assigned to B. certekorum

Two shed teeth from the Pipestone Creek bonebed assigned to Boreonykus.

Picture credit: The Journal of Vertebrate Paleontology

Examining Fossil Teeth

The picture above shows two shed teeth from the bonebed which have been assigned to the new Velociraptorinae genus.  The dating of the bonebed is not precise, however, a volcanic ash layer approximately one metre above the site has been dated to 73.27 million years ago +/- 250,000 years.

The researchers comment that all the material assigned to Boreonykus probably came from a single individual and the identification of a new dromaeosaurid, classified as a eudromaeosaur (a sub-group of the Dromaeosauridae family) and possibly a member of the Velociraptorinae, a sub-family of the Dromaeosauridae, if this is the case, it extends the known palaeofauna of the polar dinosaurs in northern latitudes to include Velociraptorinae and extends the known record of North American theropods which are closely related to the predominately Asian Velociraptors and their close relatives.

For articulated models of dromaeosaurids and other dinosaurs: Beasts of the Mesozoic Articulated Models.

Scientists Examine the Pathology Preserved on the Dilophosaurus wetherilli Holotype

Life was tough for the Dinosauria, the Mesozoic was no “walk in the Jurassic Park”, that’s for sure.  However, detailed analysis of injuries or disease preserved in the fossilised bones of dinosaurs does not take place that often.  Here we report on a paper published in the on line, academic journal PLOS One that provides a comprehensive account of the pathology on the holotype specimen of the theropod dinosaur Dilophosaurus (D. wetherilli).

The Pathology of a Dilophosaurus Specimen (UCMP 37302)

A total of eight damaged bones on the pectoral girdle and forelimbs.  Scale bar = 5 centimetres.

Picture credit: PLOS One (L. Walters)

Dilophosaurus – Lithe Early Jurassic Carnivore

At around six metres in length, Dilophosaurus was one of the largest carnivorous dinosaurs known from the Early Jurassic.  A number of species have been described, fossils of D. wetherilli are associated with the Kayenta Formation of Arizona.  Both jaws were relatively light and slender and the upper jaw had a distinctive kink.  Studies of the dentition (teeth) and analysis of skull stresses indicates that this dinosaur probably specialised in hunting relatively small prey.  It may also have scavenged the kills of other dinosaurs.

Dilophosaurus a Light and Agile Theropod

Wild Safari Prehistoric World Dilophosaurus.

Picture credit: Everything Dinosaur

Safari Ltd have introduced two Dilophosaurus models into their model range: Safari Ltd. Wild Safari Prehistoric World Models.

A Damaged Dilophosaurus

The holotype specimen shows eight substantial injuries, signs of healing indicate that this unfortunate meat-eater survived the traumas, but it probably spent a considerable portion of its adult life in quite a lot of pain.  On the left side of the dinosaur, the shoulder blade (scapula) is fractured (c in the pathology illustration above), the left radius shows a severe fracture that has healed (h).  The ulna shows signs of infection and the left thumb (digit I) had been dislocated, highlighted as (f) in the diagram at the top of the article.  On the right side of the holotype, more pathology can be found.

Abnormal torsion of the right humerus (b), three bony tumours on the radius (a), along with damage to metacarpal III (e). The right finger was so badly damaged (i), that it could not flex properly.  Some of the deformities, the researchers conclude, are the result of osteodysplasia, a condition that causes bone growth defects.  This is known in modern birds but has not been reported before in non-avian dinosaurs.

 The Badly Damaged Right Hand of the Holotype Specimen (UCMP 37302)

The damaged hand of the Dilophosaurus holotype.

Picture credit: PLOS One (L. Walters)

Damaged Digits

The damage to the digits would have meant that this dinosaur would have been severely hampered as it tried to grasp prey.  How the injuries were caused remains the subject of speculation.  The authors of the paper, Phil Senter (Department of Biological Sciences, Fayetteville State University, North Carolina) and Sara Juengst (Department of Anthropology, Appalachian State University, North Carolina) state that it is not possible to determine the number of traumatic events that all these pathological features preserved in the skeleton represent.

All the injuries and damage could have been sustained in one catastrophic event, perhaps in a fight with a rival or in an attempt to subdue prey.  The authors can at least be certain that this Dilophosaurus survived for some considerable time as the injuries show signs of extensive healing, although it would have been in a great deal of discomfort.  The fact that this dinosaur survived is a testament to how hardy these reptiles were.  It is also intriguing to speculate how this dinosaur fed whilst recovering from its various debilitating injuries.  It may have subsisted on very small prey, small enough to be subdued by the mouth and or feet.

Pathology in Dinosaurs

Injuries, trauma and general pathology in the Dinosauria is underreported.  When describing a new dinosaur species, researchers often fail to mention any pathological features that have been found.  For example, in the scientific description of the holotype specimen of Dilophosaurus wetherilli only one of the pathological features reported by the authors of this paper was described.  This Dilophosaurus specimen is a record breaker for broken bones reported in the Dinosauria portion of the fossil record, even beating the famous Allosaurus (A. fragilis) called “Big Al”.