EASC 103 Test 6

Thyreophora

Aka the shield bearing dinosaurs. Their key evolutionary novelty is the presence of one or more rows of osteoderms above or alongside the vertebral column

Osteoderms

Bones that are deeply embedded within deep layers of the skin and are typically not connected to the skeleton

Scutes

Thickened horny or bony plates

Primitive thyreophora characteristics

• have scutes

• Long tail to counterbalance the weight of osteoderms at the front

Extant animals with bony scutes

• crocodilians

• Turtles

• Some snakes and lizards and amphibians

Gharial

A crocodile from India whose snout looks like Scrat’s from Ice Age

Scutellosaurus

“Little-shield lizard”. Primitive Thyreophora that lived in Arizona during Early Jurassic 196Ma.

1.2m long (0.5 hip height) and weighed about 10 kilos (22lb)

Long tail

Scelidosaurus

“Limb lizard”. Primitive Thyreophora that lived in England Early Jurassic 191Ma.

4m long and weighed about 225kg (500lbs)

Long tail and more robust body

Discovered in 1850s and named by Richard Owen. Only found the limb bone then discovered the rest of the dinosaur. Found mostly complete

David Sole Specimen of Scelidosaurus

Found along England’s Jurassic Coast in 2000. The specimen preserved hundreds of scutes as rows in their life positions. It probably got washed out to sea, where there was no oxygen on the sea floor (means no bacteria either). Stirred up sediment when landing and then the sediment falls back down to cover it

Stegosaurs and their characteristics

“Plated lizard” are medium to large quadrupedal dinosaurs with the following novelties:

• vertical bony plates and spikes arranged in single r double rows along the neck, back, and tail

• Small head

• Short massive forelimbs (more robust)

• Small, ridged triangular-shaped teeth

Stegosaurids

Advanced stegosaurs with flatter (wider) skulls and much more longer hind limbs than forelimbs, which brings the tail up into a higher position

Sophie

An 85% complete stegosaurus located at the Natural History Museum in London

Kentrosaurus

“Sharp point lizard” is a close relative to the Stegosaurus and is found in the Late Jurassic Tendaguru Fm of Tanzania.

Has 2 paired rows of small plates covering the neck and back, merging into tall spikes above the hips and tail. They have robust shoulder girdle and huge shoulder spikes

Stegosaurus

“Roof lizard” from Late Jurassic western US. Has two rows of thin offset plates running midline from neck to tail, and two pairs of spikes at tail tip.

Its spikes had lots of grooves where blood vessels could have been. Theorized that they could blush the osteoderms

Dinosaurs that Stegosaurus lived alongside with

• Apatosaurus

• Diplodocus

• Camarasaurus

• Brachiosaurus

• Allosaurus

• Ceratosaurus

Stegosaurid defense

Use an erect limb posture for locomotion while using a sprawled forelimbs pose for defensive behaviour. This could allow them to swing their spiked tail as a clubbing device which could rotate 180° at 50km/hr.

Stegosaur extinction

Decline in diversity and abundance in Early Cretaceous and then went extinct at the start of the Late Cretaceous

Ankylosauria

Sister clade of stegosauria and has 2 types: nodosauridae and ankylosauridae

Ankylosauria characteristics

• rod of fused vertebrae along backside

• Broadly arched rib cages and hip girdle (super wide and low to the ground)

• Small triangular shaped heads with low skulls (width between eyes > height of the skull)

• Closed fenestra and added dermal bones on the skull (gives them armoured skulls and some also have armoured eyelids)

Ankylosauria diet

Ate low vegetation (especially ferns) and chewed with tiny leaf shaped teeth. Their teeth are smaller than Stegosauria

Nodosauridae characteristics

• numerous of spikes

• Simple nasal passages

• Narrow skulls

Ankylosauridae

• few or no spikes

• Complex nasal passages

• Wider skulls, more heavily armoured (including eyelids)

• Triangular bony horns

• Tail club

Ankylosaur defense

Act like tanks due to being armoured from head to tail and only its belly is unprotected. Would squat down as the main defense strategy. By lowering their centre of gravity it would’ve made them very hard to roll over

Edmontonia

Named after Edmonton, this nodosauridae is from the Late Cretaceous Dinosaur Park Formation 75Ma.

Lived alongside Euoplocehalus, Corythosaurus, and Parasaurolophus. There were other ceratopsians as well.

Euplocephalus

“Well-armed head” ankylosauridae that is also found in Alberta 75Ma in the Dinosaur Park Fm.

Lived alongside Edmontonia, Corythosaurus, and Parasaurolophus

Tail club

Consists of a handle in which the caudal vertebrae are fortified with massive ossified tendons and a knob of fused osteoderms.

Zuul crurivastator

Zuul comes from the Ghostbusters alien, and crurivastator means “destroyer of shins”. Discovered in 2017 in Montana 75Ma. It was found 99% complete. It is the only ankylosaur that’s head was found with its tail. They found skin tissue and osteoderms still in in life formation

6m

50cm skull

Ankylosaurus

“Fused lizard” that have rare fossils in Hell Creek Fm 66-68Ma Late Cretaceous. Lived alongside Trex, Triceratops, and Edmontosaurus. It is the largest ankylosaurid at 6-8m and weighing 6 tonnes or 13000lbs

Borealopelta discovery

Was found at Suncor oil sands Millennium mine in 2011 by Shawn Funk. In Alberta. It was found in the Early Cretaceous strata and revealed to be a Dino mummy

Borealopelta

“Northern shield” nodosauridae from 115Ma Early Cretaceous in Alberta. Has huge shoulder spikes and has a reddish brown colour.

Borealopelta death

It died mid-late summer during the wet season. This meant flooding and washing it out to sea. It then flipped over and drowned to the bottom.

Calli

Canada’s best preserved Triceratops. Found from deposits around 68Ma

Ceratopsia and key characteristics

name means “horn face” and first appeared in Late Jurassic of Asia and spreaded to North America during the Cretaceous. When they were in North America, they took off and started getting larger in size. They are only found in the northern hemisphere. They have these characteristics

• Frill

• Narrow beak with flaring jugals

• Rostral bone

Psittacosaurus

“Parrot lizard” is a primitive ceratopsian found in Mongolia, China, and Siberia Early Cretaceous 125Ma.

Has a small, rudimentary frill and large, pointy flaring jugals. Has a narrow beak and a large, wide head compared to its body. They also had quills/bristles on their tails that were protofeather-like.

Have highly pigmented cloaca and counter shading

Babies would walk own all fours and somewhere along the way became bipeds.

They lived in forested habitats.

Neoceratopsians

Abundant in Late Cretaceous of North America and include one of the best fossil records for dinosaurs

Neoceratopsian characteristics

• extremely large head

• Broad and prominent frill

• Pointed and sharply keeled rostral bone

• Limbs reflecting quadrupedalism (due to large heads)

• No horns

Protoceratops

“First horn face” found in Mongolia (75-70Ma) which is the same time as velociraptors. They are quadrupeds and records redial dimorphism.

Males have taller frills and a pronounced bump on their tails nasal bone

Females have shorter frills and no pronounced bump on their nasal

Hatchlings do not have a frill as big as their adult counterparts

Leptoceratops

“Little-horned face” primitive neoceratopsians found in North America 66.8 - 66Ma in Alberta and Wyoming.

They have a relatively smaller skull size than Protoceratops which is why they are facultative bipeds

Ceratopsids

Larger and more advanced neoceratopsians. Mainly found in Late Cretaceous North America

Ceratopsid characteristics

• very large skulls (1-2.8m skull length)

• Large nasal openings

• Prominent frills

• A variety of horns

• Dental battery

• Semi-sprawled posture with forelimbs bent slightly outwards at elbows to support head

Centrosaurinae

All about the nose. They either have large nasal horns or a thickened nasal bone “boss”. Also have ornamented frill with long spines

Chasmosaurine

All about the brows. Have prominent brow horns and frills lacking long spines

Centrosaurus

“Pointed lizard” that has a large nasal horn. Centrosaurinae

Styracosaurus

“Spiked lizard” with a large nasal horn and a large frill with enormous spikes. Centrosaurinae

Pachyrhinosaurus

“Thick-nosed lizard” has a boss. Centrosaurinae.

Pentaceratops

“Five horn face”. Chasmosaurinae

Triceratops

“Three horned face” chasmosaurinae with round frills and postorbital (brow) horns. 66-68Ma North America

Hell Creek Formation

Records the last 2 million years of the Late Cretaceous (Maastrichtian Age)

Hell Creek Formation Dinosaurs

• Triceratops 40%

• Tyrannosaurus rex 24%

• Edmontosaurus 20%

• Thescelosaurus 8%

• Ornithomimus and Struthiomimus 5%

• Pachycephalosaurus 1%

• Ankylosaurus 1%

Thescelosauridae

A basal neornithischia that are medium sized bipeds.

Neornithischia

Sister clade to thyrephora

Triceratops frill growth

• baby: small frill, pointy, and not attached

• Younger juvenile: beginning to fuse

• Older juvenile: fully fused

• Subadult: large frill, begins to flatten out tips

• Adult: large rounded frill, very flattened

Epoccipitals

Osteoderms around the frill

Triceratops horn growth

• baby: small and stubby

• Younger juvenile and older juvenile: brow horns point upwards and curve towards posterior

• Subadult: anterior directed straight brow horns, defensive position

• Adult: curved forward brow horns and larger nasal horn

Pachycephalosauria

“Thick-headed lizards” is a clade of bipedal, Late Cretaceous North America Hell Creek Fm marginocephalians with greatly thickened bones on skull roof.

Thickened skull was commonly adorned with nodes and spikes around their margins. Has a large dome with smaller/no spikes

Stygimoloch

“Demon from the River Styx” was thought to be a type of pachycephalosaur, but later discovered it was the teen version of the Pachycephalosaurus. Has a small dome with large spikes

Dracorex hogwartsia

“Dragon king of Hogwarts” was thought to be a pachycephalosaur, but ended up being a baby/young version of a Pachycephalosaurus. Has no dome with large spikes

What is the new name for Cretaceous-Tertiary (K/T) Extinction?

Cretaceous-Paleogene (K/Pg) Extinction

Casualties from the asteroid

• 75% of animal and plant species met extinction

• Amongst terrestrial vertebrates, all non-avian dinosaurs and pterosaurs suffered extinction

• Marine realm also suffered large losses with loss of large marine reptiles (plesiosaurs and mosasaurs). Coiled ammonoids also met extinction

• Most birds and mammals went extinct

• Lost microbiota including plankton and foraminifera

Foraminifera

Aka fora, are protozoans (single-celled animals) that feed on plankton. They have internal shells.

Food chain impact

Once the asteroid hit, the atmosphere was covered in fine dust, leaving no room for sunlight. All plants and photosynthetic plankton died, making a huge loss in herbivores and foraminifera. This led to carnivores running out of prey to eat.

The Alvarez Hypothesis

Created by geologist Walter Alvarez and his father astrophysicist Luis Alvarez in 1980. They hypothesized that a 10km asteroid hit the Earth with impact energy of 100 million nuclear bombs. The impact created ejecta that was blasted into the atmosphere and hurtled back to Earth as molten droplets, igniting fires around the globe. The impact also created tsunamis. This all happened between 0-24hrs

any fine ejecta blocked the sun for months

Ejecta

Debris that is put into the atmosphere

Upon close examination, how does the strata directly above the Boundary Clay differ from the strata below?

There are different abundance of species between the two strata. The top layer (Pg) has few foraminifera shells, and aren‘t abundant. The bottom strata (K) has a diverse variety.

What is unique about the Boundary Clay layer?

Has a lot of iridium, which is found in space dust and asteroids and are rarely found on Earth.

The Boundary Clay layer is thicker and contains small grains called spherules. How did they form?

Formed by vaporized rock that rains back down onto Earth. They look rain/glass like.

Where did the asteroid hit?

The Gulf of Mexico. Chicxulub crater, which is the same age and size as the asteroid

The Boundary Clay also contains tiny grains of shocked quartz. How did these grains become deformed?

The amount of pressure from the velocity of the asteroid turned them into grain