All about dinosaurs, fossils and prehistoric animals by Everything Dinosaur team members.
Articles, features and information which have slightly more scientific content with an emphasis on palaeontology, such as updates on academic papers, published papers etc.
Eurypterids (Eurypterida) are often referred to as sea scorpions. Like scorpions these extinct invertebrates are members of the Arthropoda Phylum. They are distantly related to extant scorpions and spiders. It is thought that the first eurypterids evolved during the Ordovician. They thrived in the Silurian and Devonian. Giant forms evolved, animals like Jaekeklopterus, Acutiramus and Pterygotus. However, the number of taxa was severely depleted during the end-Devonian extinction event and although they survived for at least another 100 million years or so, during the Carboniferous and Permian they only made up a very small percentage of the taxa described from fossil deposits.
Examples of the Pterygotioidea eurypterid lineage. Note the flattened, blade-like telson that probably helped with propulsion or acted like a rudder helping to steer the animal through the water. The fossils represent Pterygotus anglicus. Picture credit: Everything Dinosaur.
Picture credit: Everything Dinosaur
The picture (above) shows two Pterygotus anglicus fossil specimens on display at the London Natural History Museum. These Early Devonian fossils come from Arbroath (Scotland).
The Shape of the Telson
Note the broad, flattened, blade-like final segment of the animal. This is the telson and in the Pterygotioidea lineage (as well as in some other Superfamilies), the telson evolved into an organ to help with propulsion and steering. In other eurypterids, the telson is shaped very differently. For example, in the sea scorpion fossil (below), the telson is long and pointed.
A fossil of a sea scorpion (eurypterid) on display at the Manchester Museum. Note the pointed end segment (telson). Probably an example of the Silurian eurypterid Eurypterus. Picture credit: Everything Dinosaur.
The Giant Claws (Chelicerae) Seen in Some Sea Scorpion Fossils
The segmented body of eurypterids consisted of the frontal prosoma (head) and the posterior opisthosoma (abdomen). The prosoma contained the mouth and six pairs of appendages which are usually referred to as appendage pairs I to VI using Roman numerals. The segments that make up the opisthosoma are usually numbered using Arabic numerals 1, 2, 3 etc. The opisthosoma comprised twelve segments in total plus the telson.
The first pair of appendages, the only pair located in front of the mouth opening, is called the chelicerae (pronounced kel-iss-ser-ray). This pair of appendages evolved into a myriad of forms in the Chelicerata (pronounced kel-iss-ser-rat-ah), the Subphylum containing the eurypterids, spiders, mites, scorpions and horseshoe crabs. This pair of appendages form the fangs seen in spiders and form the feeding limbs of horseshoe crabs.
An Atlantic horseshoe crab in ventral view with the six pairs of appendages and the telson labelled. The first pair of appendages (chelicerae) help to push food into the mouth opening. Picture credit: Everything Dinosaur.
Picture credit: Everything Dinosaur
Powerful Pincers Adapted for Grasping Prey
Some of these appendages, such as the chelicerae of giant pterygotids evolved into powerful pincers armed with strong claws analogous to those seen in crabs and lobsters. These chelicerae seem to be adapted for grasping and subduing prey. This suggests that many eurypterids were predatory.
A stunning fossil of a sea scorpion (eurypterid) claw housed at the National Museum Cardiff (Wales) photographed in 2019 when team members at Everything Dinosaur visited.The image shows a single chelicera ramus. Picture credit: Everything Dinosaur.
Note
A single appendage is referred to as a chelicera (pronounced kel-iss-ser-rah). Whereas a pair or more are referred to as chelicerae (kel-iss-ser-ray).
A spokesperson from Everything Dinosaur commented that these arthropods were remarkable animals.
“Some 250 different taxa have been described and some of these sea scorpions show adaptations that indicate they may have been partially terrestrial. Venturing out onto land is supported by trace fossils potentially preserving tracks of eurypterids walking across mud close to bodies of water.”
With the publication of the scientific paper announcing the discovery of Eoneophron infernalis, we at Everything Dinosaur thought we would take a closer look at the Caenagnathidae. The Caenagnathidae family (pronounced seen-nag-nay-thid-ay), are part of the Oviraptorosauria clade of maniraptoran theropod dinosaurs. They are closely related to the oviraptorids (Oviraptoridae family).
A scale drawing of a dinosaur (Anzu wyliei). This dinosaur is a member of the Caenagnathidae family, and its fossils come from the Hell Creek Formation (Maastrichtian faunal stage of the Late Cretaceous). Picture credit: Everything Dinosaur.
The Maniraptora clade consists of coelurosaurian dinosaurs and is defined as including the birds and the non-avian dinosaurs more closely related to them than to Ornithomimus velox. As well as containing the Oviraptorosauria, this clade also includes several other groups such as the dromaeosaurids, the Troodontidae family and the therizinosaurs.
The Oviraptorosauria clade* is comprised of the Caudipteridae family and two closely related dinosaur families the Caenagnathidae and the Oviraptoridae that together are classified as the Caenagnathoidea. The Oviraptorosauria are united by having very bird-like skeletons, with highly pneumatised bones. In addition, the rostrum is very short, and these dinosaurs have beaks. The beak is often, but not always edentulous (no teeth). These dinosaurs were all probably feathered.
An Oviraptor dinosaur model (CollectA Age of Dinosaurs).
The image (above) depicts an Oviraptor model from the CollectA Age of Dinosaurs range.
The Caenagnathidae Family and Eoneophron infernalis
The family Caenagnathidae, together with its closely related sister family the Oviraptoridae, comprises the superfamily Caenagnathoidea. Virtually all known members of this superfamily are confined to the Late Cretaceous. Taxonomically the Caenagnathidae is defined as Chirostenotes pergracilis and all other theropods more closely related to it than they are to Oviraptor philoceratops.
Most of these dinosaurs tend to be quite small. As a result, they are probably underrepresented in the fossil record. For example, Anzu wyliei was thought until recently to be the only caenagnathid from the Hell Creek Formation. However, there are probably at least three caenagnathids present in Hell Creek strata, including the recently named Eoneophron infernalis.
The femur (left) and right tibia (right) of Eoneophron. Picture credit: Kyle Atkins-Weldman.
Caenagnathids Not Closely Related to Ostriches
The Caenagnathidae family was originally erected by Raymond Martin Sternberg (1940), the son of the pioneering palaeontologist Charles Mortram Sternberg. Raymond Martin Sternberg thought that these dinosaurs were flightless birds. He erected the Caenagnathidae family which translates as “recent jaws”. It was mistakenly thought that these theropods were closely related to the Palaeognathae “old jaws” bird family. Extant palaeognath birds include the flightless Kiwi, the Ostrich and the Rhea as well as volant forms such as Tinamou birds. It is now known that the Caenagnathidae family of non-avian dinosaurs are not closely related to palaeognaths.
Caenagnathids are confined to the Late Cretaceous of Asia and North America. They tend to have small heads, long necks and short tails.
Time-calibrated Oviraptorosauria clade consensus tree showing the position of Eoneophron infernalis. Picture credit: Atkins-Weltman et al.
Challenging Phylogenetic Assessment
Whilst the fragmentary nature of most caenagnathid specimens makes phylogenetic assessment challenging, in the recent Eoneophron infernalis paper the researchers undertook a time-calibrated phylogenetic analysis of the Oviraptorosauria. Eoneophron was placed as a sister taxon to Citipes elegans and Elmisaurus rarus.
The difficulties involved in classifying oviraptorosaurs is exemplified by this placement. Although skeletal similarities between these three dinosaurs exist, there is a lack of comparable fossil material to study. Citipes elegans is geologically older. Its fossils come from the Dinosaur Provincial Park Formation of Alberta (Campanian faunal stage of the Late Cretaceous). In contrast, Elmisaurus rarus probably predates Eoneophron infernalis by a couple of million years. It too is from the Maastrichtian faunal stage of the Cretaceous. However, E. rarus fossils come from the Nemegt Formation of Mongolia.
A revision of already described specimens coupled with improved fossil sampling should help palaeontologists to gain a better understanding of the taxonomy of the Oviraptorosauria and specifically the enigmatic Caenagnathidae.
The Oviraptorosauria clade* also includes some other theropods regarded as basal members of this clade. For example, Incisivosaurus gauthieri from the Early Cretaceous of China.
Newly published research examining dinosaur locomotion and comparing it with other archosaurs suggests that the way in which dinosaurs moved could have given them a competitive advantage.
The research was undertaken by a team from the University of Bristol. It has been published today in Royal Society Open Science. The team’s findings indicate that the earliest dinosaurs were simply faster and more dynamic than their competitors. Perhaps the greater locomotor plasticity of dinosaurs gave them a distinctive advantage over other terrestrial animals. This may help to explain why the dinosaur/pterosaur/bird branch of the archosaurs, the Avemetatarsalia eventually outcompeted the archosaur crocodilian lineage (Pseudosuchia).
Studying Dinosaur Locomotion
The researchers compared the limb proportions of an extensive range of archosaurs that lived during the Triassic. In total, the limb proportions of 208 taxa were studied. The research team identified which of these tetrapods was quadrupedal (four-footed) or bipedal (two-footed). The cursoriality index of each animal was also examined. The cursoriality index is essentially a measure of running ability.
The results demonstrated that the earliest dinosaurs and their close relatives were bipedal and cursorial – they had limbs adapted for running. These animals, members of the Avemetatarsalia subgroup of the archosaurs had a much wider range of running styles compared to the other archosaur lineage, the Pseudosuchia.
Evolutionary tree showing how dinosaur limb adaptation expanded through the Triassic period until it was greater overall than the spread of locomotion types in their competitors, including pseudosuchians, other avemetatarsalians, and other archosaurs. These changes also included many early dinosaurs with strong adaptations to cursoriality (running). Mass extinctions are marked along the time scale: PTME, Permian-Triassic mass extinction; CPE, Carnian pluvial episode; ETME, end-Triassic mass extinction). Picture credit: Amy Shipley.
A Higher Range of Locomotory Modes by the Avemetatarsalia
The Pseudosuchia include the ancestors of extant crocodilians. Some were small, bipedal insectivores, but most were medium-to-large-sized carnivores and herbivores, and they were very successful throughout the Triassic. The research team calculated that the Dinosauria and other members of the Avemetatarsalia, maintained a higher range of locomotory modes throughout this period.
Lead author of the study Amy Shipley commented:
“When the crunch came, 233 million years ago, dinosaurs won out”.
The MSc Palaeobiology student at the University of Bristol added:
“At that time, climates went from wet to dry, and there was severe pressure for food. Somehow the dinosaurs, which had been around in low numbers already for twenty million years, took off and the pseudosuchians did not. It’s likely the early dinosaurs were good at water conservation, as many modern reptiles and birds are today. But our evidence shows that their greater adaptability in walking and running played a key part.”
Evolution of the thigh bone (femur) through the Triassic, starting with a very limited array of shapes, and ending with a broad array of shapes for the dinosaur femur (high disparity), indicating a wide range of locomotion modes. Picture credit: Amy Shipley.
The End Triassic Mass Extinction Event (ETME)
Co-author of the paper, Professor Mike Benton explained that at the end of the Triassic there was a mass extinction event. Most of the pseudosuchians died out, except for the ancestors of today’s crocodilians. The surviving dinosaurs expanded their range of locomotion again, taking over many of the empty niches in food webs.
Co-author Dr Armin Elsler added:
“When we looked at evolutionary rates, we found that in fact dinosaurs were not evolving particularly fast. This was a surprise because we expected to see fast evolution in avemetatarsalians and slower evolution in pseudosuchians. What this means is that the locomotion style of dinosaurs was advantageous to them, but it was not an engine of intense evolutionary selection. In other words, when crises happened, they were well placed to take advantage of opportunities after the crisis.”
An illustration of the early dinosaur Eoraptor lunensis from the Upper Triassic Ischigualasto Formation of Argentina. Picture credit: Nobu Tamura.
Could Dinosaur Locomotion be Key to Their Evolutionary Success?
Fellow collaborator Dr Tom Stubbs stated that the word “dinosaur” conjures up in the public’s imagination a slow-moving, large and lumbering animal. The first dinosaurs, animals such as Eoraptor lunensis were very different. The first members of the Dinosauria were small and agile.
Dr Stubbs said:
“The first dinosaurs were only a metre long, up high on their legs, and bipedal. Their leg posture meant they could move fast and catch their prey while escaping larger predators.”
Co-author Dr Suresh Singh concluded:
“And of course, their diversity of posture and focus on fast running meant that dinosaurs could diversify when they had the chance. After the end-Triassic mass extinction, we get truly huge dinosaurs, over ten metres long, some with armour, many quadrupedal, but many still bipedal like their ancestors. The diversity of their posture and gait meant they were immensely adaptable, and this ensured strong success on Earth for so long.”
Everything Dinosaur acknowledges the assistance of a media release from Bristol University in the compilation of this article.
The scientific paper: “Locomotion and the early Mesozoic success of Archosauromorpha” by Amy E. Shipley, Armin Elsler, Suresh A. Singh, Thomas L. Stubbs and Michael J. Benton published in Royal Society Open Science.
A new species of Jurassic pterosaur has been described based on fossils found on the Isle of Skye. The new flying reptile has been named Ceoptera evansae (Ki-yo-op-ter-rah evans-say). It lived around 168-166 million years ago (Bathonian faunal stage of the Middle Jurassic). It has been classified as part of the controversial Darwinoptera clade. The discovery of Ceoptera demonstrates that this clade was considerably more diverse than previously thought. The Darwinoptera are now thought to have persisted for more than twenty-five million years and probably had a worldwide distribution.
The Isle of Skye around 168 million years ago. A flock of Ceoptera take to the skies as turtles look on and a group of sauropods wander towards the treeline. A large pterosaur is seen overhead, we suspect that this is a solitary Dearc sgiathanach. Picture credit: NHM and Mark Witton.
The artist has depicted a single, slender-winged pterosaur soaring high above the Ceoptera flock. We suspect that this is a representation of the recently described rhamphorhynchid Dearc sgiathanach.
The fossil remains were found partially exposed on a large boulder situated a few metres from the cliffs on the north side of Glen Scaladal at Cladach a’Ghlinne, a small beach that forms part of the coastline of Loch Scavaig, on the Strathaird Peninsula, Isle of Skye. The fossil bearing rocks are associated with the Kilmaluag Formation. The density and hardness of the matrix, coupled with the fragile nature of the fossil bones made the specimen unsuitable for mechanical preparation.
A complex process of acid bath immersion was undertaken to weaken the matrix and to expose the bones. The acid immersion, stabilising via rinsing and oven drying was repeated twenty-nine times in order to get the bones suitably prepared for analysis and CT scanning.
The fossilised remains of Ceoptera evansae. The slab (top left) contains the shoulder region, parts of the wing and vertebrae. Picture credit: Trustees of the Natural History Museum London.
Ceoptera evansae
The discovery of Ceoptera underpins a new and more complex model for the early evolution of pterosaurs. Flying reptile fossils from the Middle Jurassic are extremely rare. Those that have been found are relatively incomplete and fragmentary. Whilst no cranial material is associated with Ceoptera evansae, this discovery demonstrates that the major Jurassic pterosaur clades were present before the end of the Early Jurassic.
The fossils also provide important new information concerning the geographic and stratigraphic range of the controversial clade Darwinoptera. It had been thought that this species-poor group were largely restricted to the Upper Jurassic of eastern Asia. With the discovery of Ceoptera it suggests that these pterosaurs were both temporally and geographically widespread.
Many of the bones remain completely embedded in rock and can only be studied using CT-scanning. This pterosaur is one of the first flying reptiles to be digitally assessed using scans and computer modelling.
Senior author of the paper, Professor Paul Barrett (London Natural History Museum), stated:
“Ceoptera helps to narrow down the timing of several major events in the evolution of flying reptiles. Its appearance in the Middle Jurassic of the UK was a complete surprise, as most of its close relatives are from China. It shows that the advanced group of flying reptiles to which it belongs appeared earlier than we thought and quickly gained an almost worldwide distribution.”
A three-dimensional model showing the layout and configuration of the fossil material. Picture credit: Liz Martin-Silverstone.
Ceoptera evansae – What’s in a Name?
The generic name is derived from the Scottish Gaelic word cheò or ceò (pronounced ‘ki-yo’), meaning mist. This is a reference to the common Gaelic name for the Isle of Skye Eilean a’ Cheò, or Isle of Mist), and the Latin ptera, meaning wing (feminine).
The species name honours Professor Susan E. Evans. It was Professor Evans who first became aware of the Glen Scaladal site’s potential for vertebrate fossils.
Lead author Dr Liz Martin-Silverstone, a palaeobiologist at the University of Bristol explained:
“The time period that Ceoptera is from is one of the most important periods of pterosaur evolution, and is also one in which we have some of the fewest specimens, indicating its significance. To find that there were more bones embedded within the rock, some of which were integral in identifying what kind of pterosaur Ceoptera is, made this an even better find than initially thought. It brings us one step closer to understanding where and when the more advanced pterosaurs evolved.”
Everything Dinosaur acknowledges the assistance of the press team at the University of Bristol and a media release from the London Natural History Museum in the compilation of this article.
The scientific paper: “A new pterosaur from the Middle Jurassic of Skye, Scotland and the early diversification of flying reptiles” by Elizabeth Martin-Silverstone, David M. Unwin, Andrew R. Cuff, Emily E. Brown, Lu Allington-Jones and Paul M. Barrett published in the Journal of Vertebrate Paleontology.
To discover a new dinosaur species might mark the high point of a long career in palaeontology for some scientists. However, for one Oklahoma State University (OSU) student they can already put a tick in the “named a new dinosaur box” on their curriculum vitae. Kyle Atkins-Weltman (PhD student in the School of Biomedical Sciences), was studying a selection of foot and leg bone fossils of what was thought to be a juvenile Anzu wyliei. Remarkably, analysis of the fossils indicated that these bones came from a mature animal and as such they represented a new dinosaur species. Based on these findings, Kyle was able to erect a new Hell Creek theropod – Eoneophron infernalis.
Limb bones of the newly described Hell Creek Formation caenagnathid Eoneophron infernalis. Picture credit: Kyle Atkins-Weldman.
The picture (above) shows limb bones from the newly described caenagnathid. Metatarsals (left) with the right tibia (centre) and a femur (right).
Pharaoh’s Dawn Chicken from Hell
Bone histology revealed the fossils to represent a dinosaur at least six years of age when it died. These were not the bones from a juvenile A. wyliei, but from a smaller but closely related theropod species. The student named the new dinosaur Eoneophron infernalis. It translates as “Pharaoh’s dawn chicken from Hell”. Team members at UK-based Everything Dinosaur pronounce this dinosaur as ee-on-oh-fron in-fur-nal-lis.
The name honours the description of the Anzu taxon as well as the student’s late beloved pet, a Nile monitor lizard named Pharaoh.
Oklahoma State University PhD student Kyle Atkins-Weltman. Picture credit: Matt Barnard/OSU Centre for Health Sciences.
Eoneophron infernalis and Implications for Caenagnathid Diversity
Previously, only one caenagnathid (Anzu wyliei) was known from the Hell Creek Formation. It was formally named and described in 2014 (Lamanna et al). Palaeontologists were aware of smaller, fragmentary fossil bones representing caenagnathids from the Hell Creek Formation. It was unclear whether these fossils represented distinct, undescribed taxa or juvenile A. wyliei specimens. Eoneophron infernalis is estimated to have stood around one metre high at the hips and weighed approximately seventy kilograms. In contrast, Anzu wyliei was much larger, with a hip height of about 1.5 metres and weighing three hundred kilograms.
This new taxon is also distinct from other small caenagnathid material previously described from the area. Scientists postulate that there are potentially three distinct caenagnathid genera in the Hell Creek Formation. These results show that caenagnathid diversity in the Hell Creek ecosystem has probably been underestimated.
A life reconstruction of Eoneophron infernalis (left), an as yet, undescribed caenagnathid MOR 752 (bottom), and Anzu wyliei (right). Picture credit: Zubin Erik Dutta.
A Feathered Dinosaur
When asked to describe Eoneophron infernalis, Kyle highlighted how closely related to birds these dinosaurs were. He stated:
“It was a very bird-like dinosaur. It had a toothless beak and a relatively short tail. It’s hard to tell its diet because of the toothless beak. It definitely had feathers. It was covered in feathers and had wings.”
Co-author of the scientific paper and Kyle’s faculty advisor Associate Professor Eric Snively commented:
“Kyle is the first student researcher at OSU-CHS to reveal, describe and name a new dinosaur.”
When it looked like the fossils may not belong to an Anzu, Atkins-Weltman turned to caenagnathid researchers Greg Funston, PhD, a palaeontologist with the Royal Ontario Museum in Ontario, Canada, and palaeontology PhD candidate Jade Simons with the University of Toronto for their assistance.
He was also able to involve Associate Professor of Anatomy Dr Holly Woodward Ballard, an expert in bone histology.
A view of the metatarsal bones of Eoneophron infernalis. Picture credit: Kyle Atkins-Weldman.
A Thrilling Discovery
Kyle Atkins-Weltman explained that his project and published findings would not have been possible without his co-authors and those who assisted him.
He added:
“It was really thrilling. Based on the work and research I do, I never thought I would be someone to discover a new dinosaur species.”
Eoneophron infernalis life reconstruction. Picture credit: Zubin Erik Dutta.
Everything Dinosaur acknowledges the assistance of a media release from Oklahoma State University in the compilation of this article.
The scientific paper: “A new oviraptorosaur (Dinosauria: Theropoda) from the end-Maastrichtian Hell Creek Formation of North America” by Kyle L. Atkins-Weltman, D. Jade Simon, Holly N. Woodward, Gregory F. Funston and Eric Snively published in PLOS One.
Team members photographed a sauropod skin impression whilst visiting the London Natural History Museum. The specimen is part of the Patagotitan exhibition entitled “Titanosaur – Life as the Biggest Dinosaur”. Although most visitors probably overlook this fossil it is perhaps one of the most important fossil specimens on display in this part of the museum.
A detailed analysis of the skin impression provided new information on the anatomy of sauropods. A study revealed features on the skin that might explain how these dinosaurs were able to grow so big.
A sauropod skin impression (NHMUK R1868) on display as part of the London Natural History Museum Patagotitan exhibition. Picture credit: Everything Dinosaur.
Picture credit: Everything Dinosaur
Studying a Sauropod Skin Impression
This is a fossilised imprint of sauropod skin. It is specimen number NHMUK R1868. It was the first skin impression to be described in any non-avian dinosaur. The fossil, discovered in 1852 provided the first evidence that sauropods had scaly skin. The impression was formed when the skin of a carcase was pressed into soft mud. This left an impression of the skin contours imprinted on the sediment. Over millions of years the ground hardened into rock.
The fossil was discovered in Hastings along with a large forelimb. The material comes from the Hasting Beds, which are part of the Wealden Group and represent Lower Cretaceous deposits. The sauropod, possibly a basal titanosaur, has been named Haestasaurus becklesii. The skin impression is thought to have come from the forearm, the presence of smaller scales at one end of the specimen suggests that the skin impression might have come from the elbow area. The smaller scales would have permitted greater flexibility in the joint.
Sue from Everything Dinosaur poses in front of the colossal Patagotitan skeleton which is being exhibited at the Natural History Museum (London). Picture credit: Everything Dinosaur.
Picture credit: Everything Dinosaur
A Patagotitan dinosaur model. The long neck and tail may have helped with thermoregulation, enabling this super-sized tetrapod to lose heat efficiently.
The image above shows the recently introduced Wild Safari Prehistoric World Patagotitan dinosaur model.
A paper published in February 2022 (Pittman et al) examined NHMUK R1868 in detail using laser-simulated fluorescence (LSF). This technique reveals much more detail at the microscopic level than exposure to normal light and UV light. The researchers discovered that the skin was covered in tiny bumps (papillae). These convex bumps increased the surface area of the skin, and it was thought that they played a role in thermoregulation.
Large animals, such as sauropods need to find ways to stop their bodies overheating. The extended surface area of their long necks and tails would have helped, but the researchers speculate that these small bumps greatly increased the skin surface area, thus permitting more efficient heat exchange between their bodies and the environment.
A review of other sauropod skin fossils demonstrated that intrascale papillae were unique to and widespread across the Neosauropoda. This suggests that this trait evolved early in the Sauropoda, and it might explain why these types of dinosaurs were able to grow so big and to become giants.
The scientific paper: “Newly detected data from Haestasaurus and review of sauropod skin morphology suggests Early Jurassic origin of skin papillae” by Michael Pittman, Nathan J. Enriquez, Phil R. Bell, Thomas G. Kaye and Paul Upchurch published in Communications Biology.
The evolution of a jaw and the transition from passive feeding to predatory behaviour is regarded as one of the most significant events in the evolution of vertebrates. It has been suggested that early vertebrates were passive, suspension feeders. They removed particles of food in the water column by some form of filtration. Over time, a more predatory, active lifestyle evolved. Living jawless vertebrates today such as the Hagfish (Myxinidae family) are scavengers as well as predators. Studying these animals can help to inform palaeontologists about the potential feeding strategies of extinct jawless fish. However, the feeding strategy of these animals and jawed stem-gnathostomes (the phylogenetic intermediates of living jawless and jawed vertebrates) remains unclear.
The diversity and relationships of jawless and jawed vertebrates, crosses indicate extinct clades. The red star indicates the location of the Heterostraci. Picture credit: Grohganz et al with additional annotation by Everything Dinosaur.
New and Innovative Research into Extinct Jawless Fishes
A new scientific paper, published in the Journal of Vertebrate Paleontology casts doubt on the idea that some jawless vertebrates were filter feeders. Scientists from the University of Bristol used innovative research techniques to examine the dentition of extinct jawless heterostracans. The Heterostraci are an extinct subclass of the Agnatha (jawless fishes).
The research discovered that the forward-facing denticles on the oral plates of heterostracans were not adaptations for filter feeding.
Madleen Grohganz, the lead author of the paper from Bristol University’s Palaeobiology Research Group commented:
“The origin of vertebrates, our very own evolutionary lineage, is widely regarded as one of the most important events in evolutionary history. Early vertebrate evolution is a much-debated topic among biologists and palaeontologists and there are still many unresolved questions.”
Articulated, V-shaped oral plate apparatus of Protopteraspis vogti; B, aboral; C, oral views. Rostral is to the top of the image in B and C. Note scale bar = 2 mm. Picture credit: Grohganz et al.
The Jawless Heterostracans
Heterostracans are among the oldest of all the vertebrates. Their mode of feeding remains controversial. To determine whether they were filter feeders or predators sophisticated modern computational palaeobiological techniques were employed in this study.
Heterostracans possessed a feeding apparatus of rod-like oral plates with rows of forward-facing denticles outside of the mouth. These traits had been thought to represent combs for filter feeding.
The team employed Computational Fluid Dynamics (CFD), a technique from engineering that simulates fluid flows and their interaction with solids to test this hypothesis. Water flow modelled around these structures would indicate whether these oral plates were effective at filtering out particles of food.
All the tested models, independent of denticle orientation, showed similar flow, velocity and vorticity patterns. Based on these analyses the team rejects the hypothesis that denticle orientation is a specific adaption to suspension feeding. The denticles only occur on the lateral sides of the very tip of the oral plates. They may have played a role in preventing oversized food particles, sediment or parasites from lodging between the plates.
Madleen Grohganz stated:
“Our study is one of the first, that actively tests feeding mode hypotheses of early jawless vertebrates instead of making poorly constrained inferences. This is an important step towards better understanding the feeding mode of early jawless vertebrates, testing evolutionary scenarios and ultimately shedding more light on early vertebrate evolution.”
More Research into Stem-gnathostomes Required
The feeding strategies of stem-gnathostomes remains largely unknown. The researchers conclude that other feeding theories such as whether heterostracans were capable of biting still require testing.
The exact nature of heterostracan feeding remains an open question. Other feeding hypotheses, which propose a mechanical function related to active biting or scavenging, still need to be tested. The creation of three-dimensional skull models based on non-destructive CT scans could yield more evidence to help inform palaeontologists. Madleen Grohganz and her colleagues agree that more research is required on these basal vertebrates.
Dr Grohganz explained:
“Previous feeding mode hypotheses of early jawless vertebrates have mainly been based on poorly constrained inferences. But using computational palaeobiological methods, we were able to actually test and reject one of these feeding mode hypotheses.”
Everything Dinosaur acknowledges the assistance of a media release from the University of Bristol in the compilation of this article.
The scientific paper: “Testing hypotheses of pteraspid heterostracan feeding using computational fluid dynamics” by Madleen Grohganz et al published in the Journal of Vertebrate Paleontology.
A student from the University of Bristol has confirmed the presence of Kuehneosaurs in the Late Triassic of southwestern England. These gliding reptiles were part of a rich reptile dominated fauna that lived on a series of sub-tropical islands, part of an ancient archipelago. The biggest island extended from Frome in the east to Weston-super-Mare in the west. It was around eighteen miles (thirty kilometres long). It is referred to as the Mendip Palaeo-island.
An artist’s impression of a gliding reptile Kuehneosaurus. Picture credit: Mike Cawthorne.
Picture credit: Mike Cawthorne
Kuehneosaurs on Sub-tropical Islands
Kuehneosaurs superficially resemble lizards. However, they were more closely related to the ancestors of crocodilians and dinosaurs. They were small animals, which could fit neatly on the palm of a hand, and there were two species present. One species had extensive wing flaps, the second species had much shorter wings. These wings consisted of skin stretched over elongated ribs. Powered flight was beyond them, but they probably were very competent gliders.
Kuehneosaurs probably occupied a niche in the ecosystem similar to the extant flying lizard Draco from southeast Asia. They most likely wandered about on the ground and climbed trees in search of insects and other small invertebrates. To escape from predators, or to make rapid progress through the trees, they could launch themselves into the air and glide for several metres.
The discovery of Kuehneosaurs in the Late Triassic ecosystem was made by University of Bristol Masters student Mike Cawthorne. He had been examining numerous reptile fossils collected from limestone quarries, which represent deposits associated with the Mendip Palaeo-island.
Image showing partial skeleton of gliding reptile Kuehneosaurus on rock from Emborough. Picture credit: David Whiteside.
Picture credit: David Whiteside
No Dinosaur Fossils Found but They Were Probably Present
The research, published in the “Proceedings of the Geologists’ Association”, also records the presence of reptiles with complex teeth, the trilophosaur Variodens and the aquatic Pachystropheus that probably lived a bit like a modern-day otter likely eating shrimps and small fish. However, no dinosaur bones were found. These animals either fell or their bones were washed into caves and cracks in the limestone. This led to their preservation and the development of a fossil assemblage.
A jawbone of unusual Triassic reptile Variodens first named from Emborough. B) Typical Emborough rock with many bones. C, D and E) bones from land-living relatives of crocodiles. Picture credit: David Whiteside.
Picture credit: David Whiteside
Masters student Mike Cawthorne commented:
“All the beasts were small. I had hoped to find some dinosaur bones, or even their isolated teeth, but in fact I found everything else but dinosaurs. The collections I studied had been made in the 1940s and 1950s when the quarries were still active, and palaeontologists were able to visit and see fresh rock faces and speak to the quarrymen.”
A Home for a Diverse Assemblage of Small Reptiles including Kuehneosaurs
Professor Mike Benton from Bristol University’s School of Earth Sciences added:
“It took a lot of work identifying the fossil bones, most of which were separate and not in a skeleton. However, we have a lot of comparative material, and Mike Cawthorne was able to compare the isolated jaws and other bones with more complete specimens from the other sites around Bristol. He has shown that the Mendip Palaeo-island, which extended from Frome in the east to Weston-super-Mare in the west, nearly 30 km long, was home to diverse small reptiles feeding on the plants and insects. He didn’t find any dinosaur bones, but it’s likely that they were there because we have found dinosaur bones in other locations of the same geological age around Bristol.”
Paying Tribute to the Fossil Collectors
Dr David Whiteside (University of Bristol) praised the work of the amateur fossil collectors and academics who found the fossils stating:
“The bones were collected by some great fossil finders in the 1940s and 1950s including Tom Fry, an amateur collector working for Bristol University and who generally cycled to the quarries and returned laden with heavy bags of rocks. The other collectors were the gifted researchers Walter Kühne, a German who was imprisoned in Great Britain in the second world war, and Pamela L. Robinson from University College London. They gave their specimens to the Natural History Museum in London and the Geological collections of the University of Bristol.”
Everything Dinosaur acknowledges the assistance of a media release from the University of Bristol in the compilation of this article.
The scientific paper: “Latest Triassic terrestrial microvertebrate assemblages from caves on the Mendip palaeoisland, S.W. England, at Emborough, Batscombe and Highcroft Quarries” by M. Cawthorne, D. I. Whiteside, and M. J. Benton published in the Proceedings of the Geologists’ Association.
Scientists have identified a new species of tyrannosaur from fossils found in western New Mexico. The dinosaur has been named Tyrannosaurus mcraeensis. Although it lived many millions of years before T. rex, it was closely related to it and around the same size.
A life reconstruction of Tyrannosaurus mcraeensis with the contemporaneous chasmosaur Sierraceratops in the background. Picture credit: Sergey Krasovskiy.
Tyrannosaurus mcraeensis
The study, published in “Scientific Reports” postulates that the ancestors of T. rex originated in southern Laramidia. Where and when the tyrannosaur lineage that includes T. rex and its closest relatives evolved remains unclear. It had been thought that these theropods originated in Asia, or perhaps at more northerly latitudes of Laramidia. The identification of fossils representing a giant, 12-metre-plus tyrannosaur suggests that large-bodied, apex predators evolved alongside other exceptionally large dinosaurs at lower latitudes.
The researchers examined a partial skull (NMMNH P-3698), that had been excavated from a location in Sierra County, New Mexico. The fossil material consisted of a right postorbital and squamosal, along with a left palatine, a fragmentary maxilla and elements from the lower jaws including the left dentary. The fossils come from Hall Lake Formation (McRae Group). Uranium to lead (U/Pb) isotope analysis of a layer some thirty metres below the tyrannosaur fossil site is dated to 73.2 mya plus or minus 0.7 million years. This indicates that Tyrannosaurus mcraeensis predates T. rex by approximately 6-7 million years.
Cranial elements of Tyrannosaurus mcraeensis (NMMNH P-3698). Right postorbital in (A), lateral view; (B), medial view; (C), dorsal view. Right squamosal in (D), lateral view; (E), medial view; (F), ventral view. Note scale bars = 10 cm. Picture credit: Dalman et al.
The skull bones, previously assigned to T. rex are currently on display at the New Mexico Museum of Natural History & Science (NMMNHS).
The left dentary of Tyrannosaurus mcraeensis (NMMNH P-3698) in media view (A), lateral view (B) and dorsal view (C). The right spenial in medial view (D) and (E) the right angular in medial view. The right prearticular is shown in medial view (F). Note scale bar = 20 cm. Picture credit: Dalman et al.
Older and More Primitive than Tyrannosaurus rex
While the new discovery predates T. rex, the paper notes that subtle differences in the jaw bones make it unlikely that T. mcraeensis was a direct ancestor. However, it is assigned to the Tyrannosaurini tribe, which is defined by the authors as the last common ancestor of the Asian Tarbosaurus bataar and Tyrannosaurus rex and all its descendants.
Contributing authors on the study include researchers from the University of Bath (UK), NMMNHS, University of Utah, The George Washington University, Harrisburg University, Penn State Lehigh Valley, and the University of Alberta.
Ironically, it was the examination of horned dinosaur fossils from the same palaeoenvironment that led to the discovery of a new Tyrannosaurus species. In 2013, then-student Sebastian Dalman began to re-examine ceratopsian fossils, it led to a broader rethink about the dinosaur fauna associated with the McRae Group.
Dalman commented:
“I started working on this project in 2013 with co-author Steve Jasinski and soon we started to suspect we were on to something new.”
Careful Comparison with T. rex Skull Fossils
Analysis of the skull material revealed subtle, but unique traits relating to their morphology and articulation. Careful comparison with T. rex skull fossils led the research team to conclude that these bones did not represent Tyrannosaurus rex. This was something new.
Comparing skull bones of the newly described Tyrannosaurus mcraeensis and Tyrannosaurus rex. Variation in the postorbitals (A–F), dentaries (G–K) and splenials (M–Q) of Tyrannosaurus mcraeensis (A, G, M) and Tyrannosaurus rex (B–F, H–L, N–Q). Scale bars = 10 cm. Picture credit: Dalman et al.
As T. rex is known from multiple individuals, it is possible to show that T. mcraeensis lies outside of the range of individual variation seen in T. rex.
Co-author of the paper, Dr Anthony Fiorillo, Executive Director of NMMNHS explained:
“New Mexicans have always known our state is special, now we know that New Mexico has been a special place for tens of millions of years. This study delivers on the mission of this museum through the science-based investigation of the history of life on our planet.”
Size estimates for Tyrannosaurus mcraeensis put it in the same bracket as the famous and geologically younger T. rex. It is thought to have measured around twelve metres in length.
Fellow author of the paper, Dr Nick Longrich (Milner Centre for Evolution at the University of Bath) added:
“The differences are subtle, but that’s typically the case in closely related species. Evolution slowly causes mutations to build up over millions of years, causing species to look subtly different over time.”
Tyrannosaurus mcraeensis and the Origins of T. rex
The identification of a new Tyrannosaurus from New Mexico raises the intriguing possibility that there are several more new tyrannosaur discoveries yet to be made.
Co-author Dr Spencer Lucas (Palaeontology Curator at the NMMNHS) stated:
“Once again, the extent and scientific importance of New Mexico’s dinosaur fossils becomes clear. Many new dinosaurs remain to be discovered in the state, both in the rocks and in museum drawers!”
Tyrannosaurus mcraeensis expands our understanding of tyrannosaurs in several ways. Firstly, it suggests that the apex predators lived in what is now the southern United States at least 72 million years ago. Secondly, the Tyrannosaurus genus likely originated in southern North America then later expanded into much of the western portion of the continent.
Phylogenetic analysis supports this hypothesis. The analysis places T. mcraeensis as sister taxon to T. rex and suggests the Tyrannosaurini tribe originated in southern Laramidia.
Size, relationships and biogeography of Tyrannosaurus mcraeensis. (A), relative sizes of Tyrannosaurus mcraeensis (NMMNH P-3698) and Tyrannosaurus rex known as “Sue” (FMNH PR 2081) and the type specimen (CM 9380). An evolutionary tree based on Bayesian tip-dated phylogeny and biogeographic analysis. Picture credit: Dalman et al.
Tyrannosaurus mcraeensis Raises More Questions
The skull fossils assigned to T. mcraeensis suggest that larger, more robust and powerful tyrannosaurs evolved in the southern United States compared to the smaller and more primitive tyrannosaurs found further north.
For reasons as yet unknown, dinosaurs may have evolved to larger sizes in lower latitudes in North America. This body condition pattern is not seen in modern mammals. This newly described tyrannosaur was part of an ecosystem dominated by super-sized dinosaurs. For example, the giant chasmosaur Sierraceratops turneri was contemporaneous. In addition, the titanosaur Alamosaurus and an as yet, undescribed giant hadrosaur shared this palaeoenvironment.
Dinosaurs of the Campanian-Maastrichtian Hall Lake Formation. Tyrannosaurus mcraeensis (NMMNH P-3698), the horned dinosaur Sierraceratops turneri, a giant but as yet undescribed hadrosaurid and the titanosaur Alamosaurus. Picture credit: Dalman et al.
Giant tyrannosaurs were able to spread north during the Maastrichtian stage of the Late Cretaceous. The reasons for this migration remain unclear. Perhaps the northward spread of giant herbivores such as Triceratops and Torosaurus created a food source that could be exploited by the very biggest tyrannosaurs.
Everything Dinosaur acknowledges the assistance of a media release from the University of Bath in the compilation of this article.
The scientific paper: “A giant tyrannosaur from the Campanian–Maastrichtian of southern North America and the evolution of tyrannosaurid gigantism” by Sebastian G. Dalman, Mark A. Loewen, R. Alexander Pyron, Steven E. Jasinski, D. Edward Malinzak, Spencer G. Lucas, Anthony R. Fiorillo, Philip J. Currie and Nicholas R. Longrich published in Scientific Reports.
Yesterday, Everything Dinosaur published an article about the newly described Cambrian marine worm Timorebestia (T. koprii).
Thought to be a stem chaetognath (arrow worm), Timorebestia may have been an apex, pelagic (active swimming) marine predator during the Early Cambrian. The authors of the scientific paper proposed that these marine worms may have been top of the food chain for millions of years. The evolution of arthropods, specifically the Radiodonta and predators like Anomalocaris may have led to their decline.
Examination of what was thought to be the gut of one specimen, revealed the remains of an arthropod (Isoxys). Hence, the theory that Timorebestia was an active predator placed high in the marine food web.
Amazing Artwork Depicting a Scene from the Cambrian
As part of the media release, a fantastic and dramatic artwork showing Timorebestia attacking a shoal of Isoxys was included. This illustration was produced by the very talented palaeoartist Bob Nicholls. A variety of taxa were included in the superb painting. These animals are associated with the fossil site, located in Greenland. The location is known as the Sirius Passet Cambrian Lagerstätte.
A reconstruction of the pelagic ecosystem and the organisms fossilised in Sirius Passet, revealing how Timorebestia was one of the largest predators in the water column more than 518 million years ago. Picture credit: Bob Nicholls.
Picture credit: Bob Nicholls
A Key to the Other Marine Fauna in the Timorebestia Artwork
Such is the complexity of the artwork used to highlight a potential hunting strategy of Timorebestia, Everything Dinosaur team members decided to publish a helpful key. Readers and therefore identify the different animals feature in the painting.
The Sirius Passet marine environment. The waters over what was to become Greenland was full of life 518 million years ago. Picture credit: Bob Nicholls.
Identifying the Prehistoric Animals
We have highlighted several of the marine prehistoric animals featured in the Bob Nicholls artwork.
The Key
1 = Timorebestia koprii (a pair of these stem chaetognaths), possibly apex predators in the water column.
2 = Siriocaris a primitive arthropod.
3 = Kiisortoqia a primitive arthropod.
4 = Kerygmachela a gilled lobopodian, probably closely related to the Radiodonta. It was probably a predator, but its mouthparts were very small indicating it probably ate animals much smaller than it.
5 = Kleptothule – an elongated trilobite.
6 = Isoxys – a primitive arthropod with semi-circular, bivalved carapaces. A very common fossil in the Sirius Passet Lagerstätte.
7 = Pauloterminus – an arthropod that resembled a shrimp.
8 = An amplectobeluid – an as yet, undescribed radiodont known from the Sirius Passet Lagerstätte. It was probably a predator and distantly related to Anomalocaris.
9 = Tamisiocaris a large radiodont that was probably a filter feeder.
It has been suggested that the arrow worms such as Timorebestia were gradually replaced as apex predators by the radiodonts such as Anomalocaris. The CollectA Anomalocaris model. A fantastic replica of an early apex predator. The CollectA Anomalocaris (Other Prehistoric Animal Models).
