A New Species of Giant Oviraptorosaur – Beibeilong sinensis

The mystery of the world’s largest dinosaur eggs has been solved, and an infamous baby dinosaur fossil once the property of the Indianapolis Children’s Museum, now has a family.  In 1993, a fossilised clutch of giant dinosaur eggs and an associated embryo dinosaur skeleton was discovered east of the small village of Zhaoying, close to the township of Yangcheng, Xixia County, in western Henan Province.  Like many thousands of dinosaur egg fossils found in this part of central China, the specimen was illegally sold overseas to a buyer in America.

A Baby Dinosaur Fossil

The fossil was then sold to the Indianapolis Children’s Museum in 2001.  Subsequently, the partial nest with the small, articulated dinosaur skeleton, nick-named “Baby Louie”, was repatriated to China and it is currently housed in the Henan Geological Museum.

In a paper this week in “Nature Communications”, researchers which include Darla Zelenitsky (University of Calgary) and Professor Phil Currie (University of Alberta), have identified a new species of giant Oviraptorosaur – “Baby Louie” represents potentially one of the largest feathered creatures known to science.

The dinosaur has been named Beibeilong sinensis, the name means “baby dragon from China”.

Photographs of the Holotype Fossil Material (Beibeilong sinensis)

Right image shows schematic overlay of approximate locations of individual eggs. Eggs 1 through 4 are in an upper layer just beneath the skeleton, whereas egg 5 is in a lower layer of the block. Scale bar is in centimetres.

Picture credit: Nature Communications/Darla Zelenitsky

The picture above shows two images of the holotype nest fossil from which the new species of dinosaur, B. sinensis was described.  The picture on the left shows the fossil material with the embryo fossil located just below the scale bar.  On the second photograph, the location of five of the eggs making up the clutch have been superimposed on the fossil to give an indication of their position.

Giant Dinosaur Eggs

The eggs were given their own oogenus, Macroelongatoolithus (the name means “large elongate stone eggs”).  These are the largest-known type of dinosaur eggs with some fossils measuring around sixty centimetres in length.  The eggs associated with the Beibeilong embryo measure about forty-five centimetres long.   That’s about three times as long as a typical Ostrich egg (Struthio camelus), although Ostrich eggs are more ovoid in shape.  The research team suggest that the dinosaurs which laid these eggs, giant caenagnathid Oviraptorosaurs, created nests that may have been around three metres in diameter.

An Artist’s Illustration of the Giant Oviraptorosaur Beibeilong sinensis

A breeding pair of Beibeilong dinosaurs and their nest of giant dinosaur eggs.

 Picture credit: Zhao Chuang

The Gigantoraptor Effect

The discovery of the giant fragmentary fossils of a strange theropod (Gigantoraptor erlianensis) in 2005 changed views on the Oviraptorosauria clade forever.  When formally described in 2007, Gigantoraptor was at least five times bigger than any other known oviraptorid.  Palaeontologists had proof that giant, beaked dinosaurs existed.

To read about the discovery of Gigantoraptor: New Giant Member of the Oviraptorosauria – Gigantoraptor.

Beibeilong becomes the second genus of giant members of the Oviraptorosauria.  If “Baby Louie” had lived, then this dinosaur might have reached a length of eight metres or more and it would have easily weighed more than a tonne.  Beibeilong has been assigned to the Caenagnathidae, an enigmatic group of beaked theropods closely related to the Oviraptoridae and nested with them into the Oviraptorosauria clade.

A Scale Drawing of a Giant Caenagnathid Oviraptorosaur (G. erlianensis)

The largest feathered animal known to science (Gigantoraptor).  Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Originally, the Caenagnathidae family was erected to describe, what was thought at the time, a lineage of extinct birds.  Over the last thirty years or so, more fossil discoveries have been made in North America and Asia.  When first described Gigantoraptor was thought to be a member of the Oviraptoridae, however, Gigantoraptor is now joined in the Caenagnathidae by perhaps, the equally large Beibeilong.

An Abundance of Giant Dinosaur Egg Fossils

The Beibeilong material was excavated from strata from the Gaogou Formation (Upper Cretaceous, Cenomanian to Turonian faunal stages).  The research team suggest that Beibeilong roamed central China some ninety million years ago, twenty million years earlier than Gigantoraptor.

An abundance of Macroelongatoolithus eggs reported from Asia and North America is in stark contrast to the very few bones found of giant caenagnathids.  Thanks to the association between “Baby Louie” and the giant eggs, the first known association between skeletal remains and eggs of caenagnathids, palaeontologists are confident that these giant, beaked dinosaurs may have been relatively common throughout the Northern Hemisphere during the Late Cretaceous.

A View of the Dinosaur Embryo Skeleton (Beibeilong sinensis) and Accompanying Line Drawing

“Baby Louie” fossil (Beibeilong sinensis) and line drawing – scale bar = 5 cm.

Picture credit: Nature Communications/Darla Zelenitsky

The picture above shows a close view of the embryo skeleton (left) and a simplified line drawing highlighting important bones.

Key

fr = frontal bone (skull), or = orbit (skull), lj = lower jaw, d = dentary, fi = fibula, ti – tibia, il= ilium, f = femur.

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The Origins of the Mandibulate Body Plan

Scientists at the University of Toronto in collaboration with colleagues at the Royal Ontario Museum, have published this week a scientific paper describing Tokummia katalepsis, a predator from the Cambrian, one that has provided palaeontologists with a better understanding of the evolution of one of the most numerous and diverse group of animals on Earth.

Tokummia katalepsis

The fossils, collected during extensive field work exploring 508-million-year-old sedimentary rocks near Marble Canyon in Kootenay National Park, (British Columbia), shed light on the origin of a group of arthropods collectively known as the Mandibulata.  The Mandibulata is a clade of the phylum Arthropoda that consists of millipedes, centipedes, the crustacea and insects.  Mandibulates are united by having a pair of specialised jaws “mandibles”, which can be used for a variety of purposes such as hunting, biting, cutting food into smaller pieces, digging, carrying items and constructing nests.

A Computer-Generated Image of Tokummia katalepsis

A three-dimensional computer generated image of Tokummia katalepsis showing serrated pincers and the pair of mandibles.

Picture credit: Royal Ontario Museum

Studying the Arthropoda

The mandibulates constitute the largest, most speciose and most varied clade within the Arthropoda, but their evolutionary origins are poorly understood.  The discovery of several well-preserved specimens of T. katalepsis documents, for the first time, the anatomy of an early member of the Mandibulata.

Commenting on the significance of this research, Cédric Aria (University of Toronto) and lead author of the paper published in the journal “Nature” stated:

“In spite of their colossal diversity today, the origin of mandibulates had largely remained a mystery.  Before now we’ve had only sparse hints at what the first arthropods with mandibles could have looked like and no idea of what could have been other key characteristics that triggered the unrivalled diversification of that group.”

One of the T. katalepsis Fossils Used in the Study

The flattened fossil of Tokummia showing numerous legs, the dorsal carapace and the specialised pincers.

Picture credit: Jean-Bernard Caron (Royal Ontario Museum)

The photograph above shows one of the beautifully preserved fossils found in 2014.  This specimen of Tokummia katalepsis shows a number of strong legs on the left partially protruding from the body, the shape of the bivalved carapace and dozens of small paddle-like limbs below the trunk at the lower right.

A Cross Between a Crab, a Centipede and a Can-opener

Described by some observers as looking like a cross between a crab, a centipede and a can-opener, Tokummia lived in a tropical sea that teemed with early marine life-forms including the ancestors of vertebrates.  At around ten centimetres in length, T. katalepsis was one of the largest predators in the ecosystem.  It had large pincers which the researchers thought would have been too delicate to tackle shelled animals like brachiopods and bivalves.

The research team postulate that Tokummia was primarily benthic (living on the sea floor), where it scuttled about digging into the sediment to catch soft bodied creatures such as worms.  The claws reminded the scientists of a can-opener, once grasped, any unfortunate prey would have been cut up into more easily digestible pieces by those revolutionary, broad, serrated mandibles.

The genus name honours Tokumm Creek, a small river that runs through Marble Canyon, the location of the fossil finds.  The species or trivial name is derived from the ancient Greek for “grasping”.

A Computer-Generated Image from a Video that Demonstrates Tokummia Locomotion

A computer animated image showing the basic body plan of Tokummia katalepsis.

Picture credit: Royal Ontario Museum

Co-author of the scientific paper and an expert on the Burgess Shale biota, Jean-Bernard Caron (Royal Ontario Museum and an Associate Professor at the University of Toronto), stated:

“This spectacular new predator, one of the largest and best preserved soft-bodied arthropods from Marble Canyon, joins the ranks of the many unusual marine creatures that lived during the Cambrian Explosion, a period of rapid evolutionary charge starting about half a billion years ago when most major animal groups first emerged in the fossil record.”

Numerous Fossil Specimens Studied

Careful mechanical preparation of the numerous specimens coupled with photographic work carried out under differing wavelengths of light, revealed the details of the Tokummia body plan.  The segmented trunk of Tokummia consisted of fifty small segments covered by a wide, two-piece carapace.  The delicate fossils show evidence of the pair of broad, notched mandibles as well as the large but quite delicate-looking front claws (maxillipeds), which are typical features of extant mandibulates.

Importantly, the animal bears subdivided limb bases with tiny projections called endites, which can be found in the larvae of certain crustaceans alive today and are now thought to have been critical innovations for the evolution of the various legs of mandibulates, and even for the mandibles themselves.

Fossils Providing an Insight into the Evolution of the Mandibulata

Dorsal/ventral view of Tokummia katalepsis fossil material.

Picture credit: Royal Ontario Museum

Tokummia katalepsis Similar to Living Members of the Myriapoda

Graduate student Cédric Aria added that the many segments that make up the body are very reminiscent of living Myriapoda, the sub-phylum of Arthropoda that includes centipedes, millipedes and their relatives.

He went onto state:

“Tokummia also lacks the typical second antenna found in crustaceans, which illustrates a very surprising convergence with such terrestrial mandibulates.”

The study also resolves the affinities of other emblematic fossils excavated from Canada’s famous Burgess Shale deposits, more than a hundred years after their initial discovery.  Burgess Shale fossils such as Branchiocaris, Canadaspis and Odaraia form with Tokummia, a group of crustacean-like arthropods that can now be placed at the base of all mandibulates, they can be regarded as basal members of the Mandibulata.

The scientific paper: “Burgess Shale Fossils Illustrate the Origin of the Mandibulate Body Plan”: by Cédric Aria and Jean-Bernard Caron, published in the journal “Nature”.

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Corythosaurus Fossil Gets its Head Back

Scientists from the University of Alberta have been able to reunite the fossilised body of a Corythosaurus to its head, nearly one hundred years after the skull fossil was removed from the dig site.

Researchers have matched the headless skeleton to a Corythosaurus skull (C. excavatus) from the university’s Palaeontology Museum that had been collected in 1920 by the eminent George Sternberg during field work in what is now called the Dinosaur Provincial Park (southern Alberta).

Graduate Katherine Bramble, a co-author of the scientific paper that appears in the latest issue of “Cretaceous Research” commented:

“Based on our results, we believed there was potential that the skull and this specimen belonged together.”

The Corythosaurus (C. excavatus) Skull Collected by George Sternberg in 1920

The Corythosaurus skull collected by George Sternberg in 1920.

Picture credit: The University of Alberta

Trophy Hunting When it Came to Dinosaur Fossils

The Corythosaurus skull shown in lateral view (above) was collected in 1920 and designated the holotype fossil for a new hadrosaurid (Corythosaurus excavatus) by C. W. Gilmore in 1923.  The skull, (UALVP 13) became part of the University’s vertebrate fossil collection.  In 1992, a previously uncovered, weathered, Corythosaurus skeleton was found.  A field team from the University of Alberta collected the specimen in 2012 and research undertaken by Darren Tanke (a technician at the Royal Tyrrell Museum), a co-author of the paper indicated that the body remains could be associated with the already known skull material.

In the 19th and early 20th century, palaeontologists in North America were almost faced with an embarrassment of riches when it came to dinosaur fossils.  The extensive fossil deposits in Utah, Montana and southern Alberta led to many field teams simply “cherry picking” and only collecting the most spectacular of fossils, items such as claws, skulls, dermal armour, horns and teeth.  It is relatively common for a field team working in the Dinosaur Provincial Park to come across specimens missing skull material.

A Close-Up View of a Corythosaurus Dinosaur Model

A close up of the head of Corythosaurus.

Picture credit: Everything Dinosaur

To view the CollectA series of prehistoric animal models: CollectA Age of Dinosaurs Figures.

Corythosaurus Lower Jaw (Dentary) Found

In addition, an isolated hadrosaur dentary (lower jaw bone), found in 1992, close to the articulated, postcranial skeleton may be one of the missing jaw fossils from the holotype skull.  The idea that this postcranial material be the skeleton of the holotype of Corythosaurus excavatus was tested using anatomical information and statistical analyses.  Statistical comparisons suggest that it is possible that the skull and dentary belong to the same individual.  Furthermore, the researchers postulate that the postcranial material could belong to the UALVP 13 skull.

Katherine Bramble explained:

“Using anatomical measurements of the skull and the skeleton, we conducted a statistical analysis.  Based on these results, we believed there was potential that the skull and this specimen belonged together.”

Matching Disparate Fossils to Individual Dinosaurs

This discovery highlights a growing field of study in palaeontology, wherein, scientists try to develop new ways of determining whether various parts of a skeleton, often located in different museum collections, belong to the same individual.  For this paper, the team used anatomical measurements, but there are several other ways of matching up fossil bones, such as conducting a chemical analysis on the surrounding matrix to identify the rocks from which the fossils were found.

The scientific paper, “Reuniting the ‘head hunted’ Corythosaurus excavatus (Dinosauria: Hadrosauridae) holotype skull with its dentary and postcranium,” published in the journal of “Cretaceous Research.”

The Everything Dinosaur website: Everything Dinosaur.

Teleocrater rhadinus and Dr Alan Charig

There’s a book on our office shelves, its dust jacket is faded and torn and the pages are yellowed with age, not surprising really as it was printed in 1973.  Although many of the passages, diagrams and ideas contained within it, have long since been superseded, it is treated with great reverence as it is one of the first dinosaur books I ever owned.  Entitled “Before the Ark” it accompanied a ten-part television series on vertebrate palaeontology produced by the BBC.

Written by Alan Charig and Brenda Horsfield, (Dr Charig wrote and presented the television series too), it remains a treasured possession and today, with the publication of a scientific paper in the journal “Nature”, we remember Dr Charig, a man who is still having an influence on science, even though he passed away some twenty years ago.

“Before the Ark” and Teleocrater – Tribute to Dr Alan Charig

“Before the Ark” and Teleocrater (before the dinosaurs).

Picture credit: BBC with T. rhadinus artwork by Gabriel Lio (Museo Argentino de Ciencias Naturales)

Early Dinosaur Counsin with “Crocodile-like” Appearance

Writing in the journal “Nature”, the researchers which include Sterling Nesbitt, assistant professor of geosciences at Virginia Tech, Roger Smith (University of Witwatersrand) and Paul Barrett of the Natural History Museum (London), describe more complete fossil material relating to Teleocrater rhadinus and formally establish this genus which helps to fill a critical gap in the fossil record leading to the evolution of the dinosaurs.

Teleocrater (the name means “slender complete basin” in reference to the reptile’s light build and the fully closed hip socket), was first proposed by Alan Charig back in the 1950s.  He was a PhD student at Cambridge University writing a doctoral thesis on Triassic reptiles of Tanganyika (now Tanzania).  Alan was being supervised by Francis Rex Parrington, a vertebrate palaeontologist who had uncovered the very first fossils of what we now refer to as Teleocrater rhadinus, during fieldwork in Tanganyika in 1933.

Fieldwork undertaken in 2015, led to the discovery of more fossil material and crucially limb elements and ankle bones which have helped determine where amongst the Archosaurs Teleocrater should be placed.

Team Members Extracting Fossil Material

Excavating the remains of Teleocrater rhadinus and other animals in southern Tanzania in 2015.

Picture credit: Roger Smith

Published photographs show authors Christian Sidor (left), Sterling Nesbitt, Kenneth Angielczyk (in the purple top and white floppy hat), along with Michelle Stocker (right), looking for Triassic vertebrates in exposures of the Manda Beds (Anisian faunal stage of the Middle Triassic) of southern Tanzania.

All Fossil Material from the Manda Beds

Francis R. Parrington collected the first fossil specimens from the Manda Beds in the Ruhuhu Basin of southern Tanzania.  These fossils were studied by Alan Charig for his doctorate, but much of Alan’s work on Teleocrater was never published.  Dr Charig went to Tanzania to search for more fossils in 1963, but it was not until the expedition of 2015, that the crucially important limb and ankle bones were recovered that demonstrated where on the Archosauria family tree Teleocrater should sit.

The ankle bones and other skeletal elements demonstrate that Teleocrater is more closely related to dinosaurs and birds than it is to crocodiles. It sits on the family tree of the archosaurs at the base of the Avemetatarsalian branch, the “bird-line Archosaurs”, sometimes also referred to as the Ornithodira.  The researchers conclude that Teleocrater and its near relatives split off from other avemetatarsalians before the evolutionary split between the Pterosauria (flying reptiles) and the dinosaurs.

Establishing T. rhadinus on the Archosauria Family Tree

Teleocrater is more closely related to pterosaurs and dinosaurs (including birds) than to crocodilians.

Picture credit: Sterling Nesbitt of Virginia Tech with additional annotation by Everything Dinosaur

The Big Two Branches of the Archosauria

The Archosauria clade consists of birds and crocodiles plus an array of extinct creatures which include the dinosaurs, silesaurids and the flying reptiles (pterosaurs).  This huge group of reptiles can be generally divided up into two distinct branches, based on the anatomy of the ankle bones.  On one branch, we have the crocodiles and their relatives (Crurotarsi), which tend to have a sprawling gait, whilst on the other branch we have the Avemetatarsalia, otherwise referred to as the ornithodirans, which tend to have their limbs directly under their hips and have a more upright gait, similar to mammals.

Dr Charig never got the opportunity to study fossils of the ankle bone, he passed away in 1997, without being able to complete his assessment of this reptile.  The researchers have honoured the contribution made by Alan Charig by naming him as an author on the 2017 paper and formally recognising the name Teleocrater, that he was the first to use.

Excavating the Fossils of Teleocrater

Excavating the remains of Teleocrater rhadinus and other animals in southern Tanzania in 2015.

Picture credit: Roger Smith

Uniting the Aphanosauria Clade – Dinosaur Ancestors on All Fours

Teleocrater helps to cement the establishment of the Aphanosauria clade, a group of long-necked, slender-limbed, carnivores that lived in the Middle Triassic and were geographically widespread across Pangaea.  The Crurotarsi archosaurs, those crocodile-like creatures were thought to be highly diversified and geographically widespread across the super-continent Pangaea.  It now seems that the other branch of the Archosauria, the Avemetatarsalia, may have been equally as diverse and as widespread as their crocodile-like cousins.

Previously, palaeontologists have postulated that the earliest dinosaur relatives were chicken-sized and bipedal.  Thanks to the 2015 fossil discoveries and the work first undertaken by F. R. Parrington and Alan Charig, scientists have a different body plan to consider.  T. rhadinus which roamed the area that was to become Tanzania some 245 million-years-ago, was much larger at around three metres long and it was a quadruped.

An Illustration of the Early Avemetatarsalian Teleocrater rhadinus

A life reconstruction of Teleocrater rhadinus.

Picture credit:  Gabriel Lio (Museo Argentino de Ciencias Naturales)

Remembering Dr Alan Charig

Alan Charig studied the fossils of what we now know as Teleocrater rhadinus.  Twenty years after his death, scientists can place this enigmatic reptile and its relatives within the avemetatarsalian branch of the Archosauria, Teleocrater represents one of the earliest members of this sub-branch, a lineage that eventually led to the dinosaurs and the birds.

In addition, with a more complete picture of Teleocrater, palaeontologists have another puzzle to ponder.  If the early branch members of the Avemetatarsalia were more species-rich and more widely geographically distributed than previously thought, then several early dinosauromorphs used to help scientists to understand how the body plan of the Dinosauria evolved, may represent specialised forms rather than the typical ancestral avemetatarsalian body plan.

Today, we reflect on the work of Dr Alan Charig and his mentor Francis Rex Parrington.  The researchers writing in the journal “Nature” have helped to put flesh onto those bones first examined all those years ago.  For my part, my thanks to Alan Charig for helping to write such a beautiful book and for inspiring a generation of science writers and enthusiasts.

The scientific paper: “The Earliest Bird-line Archosaurs and he Assembly of the Dinosaur Body Plan” by Sterling J. Nesbitt, Richard J. Butler, Martín D. Ezcurra, Paul M. Barrett, Michelle R. Stocker, Kenneth D. Angielczyk, Roger M. H. Smith, Christian A. Sidor, Grzegorz Niedźwiedzki, Andrey G. Sennikov & Alan J. Charig published in the journal “Nature”.

Everything Dinosaur acknowledges the help of Virginia Tech in the compilation of this article.

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Mexican Tracksites Indicate Decline of Dinosaurs Prior to Impact Event

A team of scientists based in Germany and Mexico have published a paper that challenges the commonly held belief that the extraterrestrial impact event marked by the Chicxulub crater resulted in the extinction of the dinosaurs and their flying cousins the pterosaurs.  In addition, studies of marine sediments indicate that at least one species of ammonite Sphenodiscus pleurisepta may have survived into the Palaeogene.

Chicxulub Extraterrestrial Impact Not the Cause of Global Mass Extinctions

An artists’s impression of the impact event.

Exploring the Fossil Assemblage of the Cretaceous/Palaeogene Boundary

Writing in the journal of the “Geological Society of America Bulletin”, the researchers which include lead author Professor Wolfgang Stinnesbeck of Heidelberg University, Professor Eberhard Frey (State Museum of Natural History, Karlsruhe) and scientists from the Museo del Desierto, Coahuila, (Mexico), postulate that the dinosaurs and the flying reptiles were in long-term decline before the Chicxulub impact and the global mass extinction that marked the end of the Mesozoic.

The scientists also postulate that Aves (birds), had spread and diversified at the same time as the Dinosauria was in decline.  Furthermore, based on fossil evidence, the team contend that at least one type of ammonite, Sphenodiscus pleurisepta persisted into the Cenozoic.

These conclusions were drawn from a comprehensive study of upper Cretaceous sedimentary sandstone rocks, laid down at the very end of the “Age of Dinosaurs”.  The tracks and body fossils found at two localities in the Mexican state of Coahuila, depict life on the shore and the surrounding waters of a shrinking inland sea.  Both sites represent sandstones within the Las Encinas Formation of north-eastern Mexico.

Remote Fossil Site in North-eastern Mexico (Las Encinas Formation)

One of the remote and isolated sites where the fossils were found.

Picture credit: Professor Stinnesbeck/Heidelberg University

The trackway assemblages at Amargos and Rancho San Francisco respectively, were produced by at least six different types of birds, while trackways of azhdarchoid pterosaurs are rare.  Only a single footprint made by a dinosaur (Theropod) was recorded.

Professor Stinnesbeck commented:

“Dinosaur tracks, however, are rare.  Only a single footprint comes from a predatory dinosaur.”

Lack of Pterosaur Fossil Evidence

The scarcity of pterosaur fossils was also noted.  The scientists state that azhdarchoid pterosaur fossils are rare.  Azhdarchids include some of the most famous and largest pterosaurs of all – Quetzalcoatlus Hatzegopteryx and Arambourgiania.  Most of the Pterosauria had become extinct by the Maastrichtian faunal stage of the Late Cretaceous.  From their heyday in the Early Cretaceous when at least ten pterosaur families existed, by the very end of the Cretaceous only two families of pterosaur are known in the fossil record.

Pterosaur Fossils Such as These Tracks are Very Rare

Pterosaur fossil tracks (north-eastern Mexico).

Picture credit: Professor Stinnesbeck/Heidelberg University

The photograph above shows prints of Azhdharchidea pterosaurs in a sandstone of the Upper Cretaceous, location – Rancho San Francisco near Paredon, north-eastern Mexico.

Research into the two locations Amargos and Rancho San Francisco, indicate a gradual decline of the dinosaurs with a simultaneous increase in the diversity of birds even before the end of the Cretaceous.

Professor Stinnesbeck added:

“Until now, it was generally assumed that the dinosaurs died out first and bird species diversified afterwards.  Our data, however, substantiate the theory that birds ascended before dinosaurs became extinct.”

The team postulate that the extraterrestrial impact event was not the cause of the dinosaur and pterosaur extinction, these reptiles were already on their way out, long before that event took place.  This idea of only a few dinosaur species persisting until the very end of the Mesozoic has been proposed before.  A count of dinosaur fossils found in the famous Hell Creek Formation of Montana supported the theory that the Dinosauria were already in decline by the end of the Cretaceous, the fossil assemblage in the very youngest rocks was dominated by just a handful of species.

Ammonites Survived into the Cenozoic

In the scientific paper, the researchers comment that the ammonites were not wiped out by the asteroid/comet/meteor strike.  Professor Stinnesbeck and his colleagues suggest that the species Sphenodiscus pleurisepta, a type of ammonite known from the United States and Mexico, survived, albeit in a declining state into the Palaeogene.

The geology professor stated:

“The effects of the Chicxulub impact were therefore not the cause of a global mass extinction, which probably came about considerably less catastrophically than previously assumed.”

Studying the Chicxulub Impact Event

The power of the extraterrestrial impact is evidenced by the abundance of crystalline clay minerals that are rounded in shape (smectite spherules), within a two-and-a-half metre-thick layer of strata.

The Last Ammonite (Sphenodiscus pleurisepta)?

Sphenodiscus pleurisepta ammonite fossil.

Picture credit: Conrad

The picture above shows a typical fossil of S. pleurisepta (picture of the holotype fossil), scale bar equals 1 cm.

For models and replicas of ammonites and other prehistoric animals: CollectA Prehistoric Life Figures.

The fifty million year decline of the Dinosauria: Bayesian Analysis Sheds New Light on Dinosaur Decline.

To read about other ammonites that may have persisted into the Cenozoic: Unravelling an Ammonite Mystery.