Dinosaurs (Remastered) Sleep Facts

Extinct for over 60 million years, yet somehow still managing to dominate children’s bedsheets and science museums. Tonight’s slow march through dinosaur taxonomy might not cure your curiosity, but it will probably outlast your insomnia.

Transcript

Welcome to the I Can't Sleep podcast,

Where I help you drift off one fact at a time.

I'm your host,

Benjamin Boster,

And today's episode is about dinosaurs.

Dinosaurs are a diverse group of reptiles of the clade Dinosauria.

They first appeared during the Triassic period,

Between 243 and 233.

23 million years ago,

Although the exact origin and timing of the evolution of dinosaurs is the subject of active research.

They became the dominant terrestrial vertebrates after the Triassic-Jurassic extinction event 201.

3 million years ago,

And their dominance continued throughout the Jurassic and Cretaceous periods.

The fossil record shows that birds are feathered dinosaurs,

Having evolved from earlier theropods during the late Jurassic epoch,

And are the only dinosaur lineage known to have survived the Cretaceous-Paleogene extinction event approximately 66 million years ago.

Dinosaurs can therefore be divided into avian dinosaurs,

Birds,

And the extinct non-avian dinosaurs,

Which are all dinosaurs other than birds.

Dinosaurs are varied from taxonomic,

Morphological,

And ecological standpoints.

Birds,

At over 11,

000 living species,

Are among the most diverse groups of vertebrates.

Using fossil evidence,

Paleontologists have identified over 900 distinct genera and more than 1,

000 different species of non-avian dinosaurs.

Dinosaurs are represented on every continent by both extant species,

Birds,

And fossil remains.

Through most of the 20th century,

Before birds were recognized as dinosaurs,

Most of the scientific community believed dinosaurs to have been sluggish and cold-blooded.

Most research conducted since the 1970s,

However,

Has indicated that dinosaurs were active animals with elevated metabolisms and numerous adaptations for social interaction.

Some were herbivorous,

Others carnivorous.

Evidence suggests that all dinosaurs were egg-laying,

And that nest-building was a trait shared by many dinosaurs.

Both avian and non-avian.

While dinosaurs were ancestrally bipedal,

Many extinct groups included quadrupedal species,

And some were able to shift between these stances.

Elaborate display structures,

Such as horns or crests,

Are common to all dinosaur groups,

And some extinct groups developed skeletal modifications,

Such as bony armor and spines.

While the dinosaurs' modern-day surviving avian lineage are generally small due to the constraints of flight,

Many prehistoric dinosaurs,

Non-avian and avian,

Were large-bodied.

The largest sauropod dinosaurs were estimated to have reached lengths of 39.

7 meters and heights of 18 meters,

And were the largest land animals of all time.

The misconception that non-avian dinosaurs were uniformly gigantic is based in part on preservation bias,

As large,

Sturdy bones are more likely to last until they're fossilized.

Many dinosaurs were quite small,

Some measuring about 50 centimeters in length.

The first dinosaur fossils were recognized in the early 19th century with the name dinosaur,

Meaning terrible lizard,

Being coined by Sir Richard Owen in 1842 to refer to these great fossil lizards.

Since then,

Mounted fossil dinosaur skeletons have been major attractions at museums worldwide,

And dinosaurs have become an enduring part of popular culture.

The large sizes of some dinosaurs,

As well as their seemingly monstrous and fantastic nature,

Have ensured their regular appearance in best-selling books and films.

Such as the Jurassic Park franchise.

Persistent public enthusiasm for the animals has resulted in significant funding for dinosaur science,

And new discoveries are regularly covered by the media.

Under the phylogenetic nomenclature,

Dinosaurs are usually defined as the group consisting of most recent common ancestor,

MRCA,

Of Triceratops and modern birds,

Neornithes,

And all its descendants.

It has also been suggested that Dinosauria be defined with respect to the MRCA of Megalosaurus and Iguanodon,

Because these were two of the genera cited by Richard Owen when he recognized the Dinosauria.

Both definitions cover the same known genera.

Dinosauria equals Ornithischia plus Cerischia.

This includes major groups such as Ankylosaurians,

Armed herbivorous quadrupeds,

Stegosaurians,

Plated herbivorous quadrupeds,

Ceratopsians,

Bipedal or quadrupedal herbivores with neck frills,

Pachycephalosaurians,

Bipedal herbivores with thick skulls,

Hornisipods,

Bipedal or quadrupedal herbivores including duckbills,

Theropods,

Mostly bipedal carnivores and birds,

And Sauropodomorphs,

Mostly large herbivorous quadrupeds with long necks and tails.

Birds are the sole surviving dinosaurs.

In traditional taxonomy,

Birds were considered a separate class that had evolved from dinosaurs,

A distinct superorder.

However,

Most contemporary paleontologists reject the traditional style of classification based on anatomical similarity in favor of phylogenetic taxonomy based on deduced ancestry in which each group is defined as all descendants of a given founding genus.

Birds belong to the dinosaur subgroup Maniraptora,

Which are Coelurosaurs,

Which are Theropods,

Which are Ceriscians.

Research by Matthew G.

Baron,

David B.

Norman,

And Paul M.

Barrett in 2017 suggested a radical revision of dinosaurian systematics.

Phylogenetic analysis by Baron et al.

Recovered the Ornithischia as being closer to the Theropoda than the Sauropodomorpha,

As opposed to the traditional union of Theropods with Sauropodomorphs.

This would cause Sauropods and Kin to fall outside traditional dinosaurs,

So they redefined Dinosauria as the last common ancestor of Triceratops horridus,

Passer domesticus,

And Diplodocus carnegii,

And all of its descendants,

To ensure that Sauropods and Kin remain included as dinosaurs.

They also resurrected the clade Ornithoscelida to refer to the group containing Ornithischia and Theropoda.

Using one of the above definitions,

Dinosaurs can be generally described as archosaurs with hind limbs held erect beneath the body.

Other prehistoric animals,

Including pterosaurs,

Mosasaurs,

Ichthyosaurs,

Plesiosaurs,

And dimetrodon,

While often popularly conceived of as dinosaurs,

Are not taxonomically classified as dinosaurs.

Pterosaurs are distantly related to dinosaurs,

Being members of the clade Ornithodira.

The other groups mentioned are,

Like dinosaurs and pterosaurs,

Members of Sauropsida,

The reptile and bird clade.

Except a metrodon,

Which is a synapsid.

None of them had the erectile limb posture characteristic of true dinosaurs.

Dinosaurs were the dominant terrestrial vertebrates of the Mesozoic era,

Especially the Jurassic and Cretaceous periods.

Other groups of animals were restricted in size and niches.

Mammals,

For example,

Rarely exceeded the size of a domestic cat and were generally rodent-sized carnivores of small prey.

Dinosaurs have always been recognized as an extremely varied group.

Over 900 non-avian dinosaur genera have been confidently identified 2018,

With 1,

124 species 2016.

Estimates put the total number of dinosaur genera preserved in the fossil record at 1,

850,

Nearly 75% still undiscovered,

And the number that ever existed in or out of the fossil record at 3,

400.

A 2016 estimate put the number of dinosaur species living in the Mesozoic at 1,

543 to 2,

468,

Compared to the number of modern-day birds,

Avian dinosaurs,

At 10,

806 species.

Extinct dinosaurs,

As well as modern birds,

Include genera that are herbivorous and others carnivorous,

Including seed-eaters,

Fish-eaters,

Insectivores,

And omnivores.

While dinosaurs were ancestrally bipedal,

As are all modern birds,

Some evolved into quadrupeds and others,

Such as Ankyosaurus and Iguanodon,

Could walk as easily on two or four legs.

Cranial modifications like horns and crests are common dinosaurian traits,

And some extinct species had bony armor.

Although the best-known genera are remarkable for their large size,

Many Mesozoic dinosaurs were human-sized or smaller,

And modern birds are generally small in size.

Dinosaurs today inhabit every continent,

And fossils show that they had achieved global distribution by the early Jurassic epoch at latest.

Modern birds inhabit most available habitats,

From terrestrial to marine,

And there is evidence that some non-avian dinosaurs,

Such as Microraptor,

Could fly or at least glide,

And others,

Such as Spinosaurids,

Had semi-aquatic habits.

While recent discoveries have made it more difficult to present a universally-agreed-upon list of their distinguishing features,

Nearly all dinosaurs discovered so far share certain modifications to the ancestral archosaur and skeleton,

Or are clearly descendants of older dinosaurs,

Showing these modifications.

Although some later groups of dinosaurs featured further-modified versions of these traits,

They are considered typical for Dinosauria.

The earliest dinosaurs had them,

And passed them on to their descendants.

Such modifications,

Originating in the most recent common ancestor of a certain taxonomic group,

Are called the synapomorphies of such a group.

A detailed assessment of archosaur interrelations by Sterling Nesbitt confirmed or found the following twelve unambiguous synapomorphies,

Some previously known.

In the skull,

A supratemporal fossa excavation is present in front of the supratemporal fenestra,

The main opening of the rear skull roof.

Epipophyses,

Obliquely backward-pointing processes on the rear top corners of the anterior front neck vertebrae,

Behind the atlas and axes,

The first two neck vertebrae.

Apex of a deltopectoral crest,

A projection on which the deltopectoral muscles attach,

Located at or more than 30% down the length of the humerus upper arm bone.

Radius,

A lower arm bone,

Shorter than 80% of humerus length.

Forth trochanter,

Projection where the caudofemoralis muscle attaches on the inner rear shaft,

On the femur thigh bone is a sharp flange.

Fourth trochanter asymmetrical,

With distal lower margin forming a steeper angle to the shaft.

On the astragalus and calcaneum,

Upper ankle bones,

The proximal articular facet,

The top connecting surface,

For the fibula occupies less than 30% of the transverse width of the element.

Exocipitals,

Bones at the back of the skull,

Do not meet along the midline on the floor of the endocranial cavity,

The inner space of the brain case.

In the pelvis,

The proximal articular surfaces of the ischium,

With the ilium and the pubis,

Are separated by a large concave surface.

On the upper side of the ischium,

A part of the open hip joint is located between the contacts,

With the pubic bone and the ilium.

Nemeal crest on the tibia,

Protruding part of the top surface of the shinbone,

Arcs anterolaterally,

Curves to the front and the outer side.

Distinct proxima distally oriented vertical ridge,

Present on the posterior face of the distal end of the tibia,

The rear surface of the lower end of the shinbone.

Concave articular surface for the fibula of the calcaneum,

The top surface of the calcaneum where it touches the fibula,

Has a hollow profile.

Nesbitt found a number of further potential synapomorphies and discounted a number of synapomorphies previously suggested.

Some of these are also present in silosaurids,

Which Nesbitt recovered as a sister group to dinosauria,

Including a large anterior trochanter,

Metatarsals 2 and 4 of sub-equal length,

Reduced contact between ischium and pubis,

The presence of a nemeal crest on the tibia,

And of an ascending process on the astragalus and many others.

A variety of other skeletal features are shared by dinosaurs.

However,

Because they either are common to other groups of archosaurs,

Or were not present in all early dinosaurs,

These features are not considered to be synapomorphies.

For example,

As diopsids,

Dinosaurs ancestrally had two pairs of infratemporal fenestri,

Openings in the skull behind the eyes,

And as members of the diopsid group archosauria,

Had additional openings in the snout and lower jaw.

Additionally,

Several characteristics once thought to be synapomorphies are now known to have appeared before dinosaurs,

Or were absent in the earliest dinosaurs and independently evolved by different dinosaur groups.

These include an elongated scapula or shoulder blade,

A sacrum composed of three or more fused vertebrae,

Three are found in some other archosaurs,

But only two are found in heraurosaurus,

And a perforate acetabellum or hip socket,

With a hole at the center of its inside surface.

Another difficulty of determining distinctly dinosaurian features is that early dinosaurs and other archosaurs from the late Triassic epoch are often poorly known and were similar in many ways.

These animals have sometimes been misidentified in literature.

Dinosaurs stand with their hind limbs erect in a manner similar to most modern mammals,

But distinct from most other reptiles,

Whose limbs sprawl out to either side.

This posture is due to the development of a laterally facing recess in the pelvis,

Usually an open socket,

And a corresponding inwardly facing distinct head on the femur.

Their erect posture enabled early dinosaurs to breathe easily while moving,

Which likely permitted stamina and activity levels that surpassed those of sprawling reptiles.

Erect limbs probably also helped support the evolution of large size by reducing bending stresses on limbs.

Some non-dinosaurian archosaurs,

Including Rhoasuchians,

Also had erect limbs but achieved this by a pillar-erect configuration of the hip joint,

Where instead of having a projection from the femur insert on a socket on the hip,

The upper pelvic bone was rotated to form an overhanging shelf.

Dinosaur fossils have been known for millennia,

Although their true nature was not recognized.

The Chinese considered them to be dragon bones and documented them as such.

For example,

Huayang Guozhezhi,

A gazetteer compiled by Chengchu during the Western Jin Dynasty,

Reported the discovery of dragon bones at Wuchang in Sichuan Province.

Villagers in central China have long unearthed fossilized dragon bones for use in traditional medicines.

In Europe,

Dinosaur fossils were generally believed to be the remains of giants and other biblical creatures.

Scholarly descriptions of what would now be recognized as dinosaur bones first appeared in the late 17th century in England.

Part of a bone,

Not known to have been the femur of a Megalosaurus,

Was recovered from a limestone quarry at Cornwell near Chipping Norton,

Oxfordshire,

In 1676.

The fragment was sent to Robert Plott,

Professor of chemistry at the University of Oxford,

And first curator at the Ashmolean Museum,

Who published a description in his The Natural History of Oxfordshire,

1677.

He correctly identified the bone as the lower extremity of the femur of a large animal,

And recognized that it was too large to belong to any known species.

He therefore concluded it to be the femur of a huge human,

Perhaps a titan or another type of giant,

Featured in legends.

Edward Lloyd,

A friend of Sir Isaac Newton,

Published Lysiphilachiae Britannicae Ichnographiae,

1699,

The first scientific treatment of what would now be recognized as a dinosaur.

In it he described and named a sauropod tooth,

Rutellum impacticum,

That had been found in Caswell near Whitney,

Oxfordshire.

Between 1815 and 1824,

The Reverend William Buckland,

The first reader of geology at the University of Oxford,

Collected more fossilized bones of Megalosaurus,

And became the first person to describe a non-avian dinosaur in a scientific journal.

The second non-avian dinosaur genus to be identified,

Iguanodon,

Was purportedly discovered in 1822 by Mary Ann Mantle,

The wife of English geologist Gideon Mantle,

Though this is disputed and some historians say Gideon had acquired remains years earlier.

Gideon Mantle recognized similarities between his fossils and the bones of modern iguanas,

And published his findings in 1825.

The study of these great fossil lizards soon became of great interest to European and American scientists,

And in 1842 the English paleontologist Sir Richard Owen coined the term dinosaur,

Using it to refer to the distinct tribe of sub-order of saurian reptiles that were then being recognized in England and around the world.

The term is derived from ancient Greek dinos,

Terrible,

Potent,

Or fearfully great,

And sauros,

Lizard,

Or reptile.

Though the taxonomic name has often been interpreted as a reference to dinosaurs' teeth,

Claws,

And other fearsome characteristics,

Owen intended it also to evoke their size and majesty.

He recognized that the remains that had been found so far,

Iguanodon,

Megalosaurus,

And Hyliosaurus,

Shared distinctive features,

And so decided to present them as a distinct taxonomic group.

As clarified by British geologist and historian Hugh Torrens,

Owen had given a presentation about fossil reptiles to the British Association for the Advancement of Science in 1841,

But reports of the time show that Owen did not mention the word dinosaur,

Nor recognize dinosaurs as a distinct group of reptiles in his address.

He introduced the dinosauria only in the revised text version of his talk,

Published in April 1842.

With the backing of Prince Albert,

The husband of Queen Victoria,

Owen established the Natural History Museum,

London,

To display the National Collection of Dinosaur Fossils and other biological and geological exhibits.

In 1858,

William Parker Folk discovered the first known American dinosaur in marl pits in the small town of Haddonfield,

New Jersey.

Although fossils had been found before,

Their nature had not been correctly discerned.

The creature was named Hadrosaurus falcii.

It was an extremely important find.

Hadrosaurus was one of the first nearly complete dinosaur skeletons found.

The first was in 1834 in Maidstone,

England,

And it was clearly a bipedal creature.

This was a revolutionary discovery,

As until that point,

Most scientists had believed dinosaurs walked on four feet like other lizards.

Folk's discoveries sparked a wave of interest in dinosaurs in the United States,

Known as dinosaur mania.

Dinosaur mania was exemplified by the fierce rivalry between Edward Drinker Cope and Othniel Charles Marsh,

Both of whom raced to be the first to find new dinosaurs in what came to be known as the Bone Wars.

This fight between the two scientists lasted for over 30 years,

Ending in 1897,

When Cope died after spending his entire fortune on the dinosaur hunt.

Many valuable dinosaur specimens were damaged or destroyed due to the pair's rough methods.

For example,

Their diggers often used dynamite to unearth bones.

Modern paleontologists would find such methods crude and unacceptable,

Since blasting easily destroys fossil and stratigraphic evidence.

Despite their unrefined methods,

The contributions of Cope and Marsh to paleontology were vast.

Marsh unearthed 86 new species of dinosaur,

And Cope discovered 56,

A total of 142 new species.

Cope's collection is now at the American Museum of Natural History in New York City,

While Marsh's is at the Peabody Museum of Natural History at Yale University.

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I’m going for round two of listening tonight, hopefully your voice will bore me to sleep.😁