PALEO

DINO 101

Lesson 1: Appearance and Anatomy

Paleontology is the study of all pre-hisoric life

Fossils are preserved evidence left behind by prehistoric organisms

The word fossil literally means ‘dug up’ and they are usually found buried in ancient rock formations. 

Dinosaur fossils include:

• Footprints 

• Eggshells

• Coprolites (Fossil poop)

To remember coprolites, think about how the word sounds like ‘crop’ and the fact that poop is usually used as manure for crops. 

• Skin and feather impressions (Rare instances)

• Bones (most common because they are made of materials which do not easily decay)

Dinosaurs came in a wide variety of sizes. 

Adaptations are traits that have evolved because they serve a specific function. 

Bone adaptations:

• Passively resist gravity and maintain animals form

• Provide a rigid framework for muscle attachment

• Provide protection and can be major components of horns and other robust weapons

• Bones store mineral reserves 

Dinosaurs belong to a group called Vertebrates

Vertebrates are animals that have skulls and vertebrae (more numerous in species of large animals, especially on land)

Vertebrae are structures made of bone and/or cartilage that surround a portion of the spinal nerve cord 

The first vertebrates evolved over 500 million years ago

Vertebrae interlock and form the vertebral column (begins with first vertebra in the neck and ends with last vertebra in the tail)

Invertebrates are animals that lack vertebrae (more species overall)

Skulls and Jaws

Skull is made up of many bones that are tightly locked together. They give great insight into a dinosaurs life.

Jaws may include teeth or beak and are crucial in determining what a dinosaur was adapted to eat

The rear portion of the skull includes the brain case (hollow chamber formed by multiple skull bones that house the brain). There are many small openings in the brain case where nerves pass through and connect to the brain. The size and shape of a brain case tells us the size and shape of a brain which can indicates/give us clues about a dinosaurs mental capabilities. 

Dinosaur skull openings

• Nares- pair of openings for the nostrils

• Orbits- pair of openings for the eyes

Dinosaurs had additional skull openings called Fenestrae 

Behid each orbit, dinosaurs had two fenestrae 

Laterotemporal fenestrae- found on the lateral sides of the skull

Supratemporal fenestrae- found on the top of the skull

Third fenestra pair, antorbital fenestrae, found between each orbit and naris amd had an unclear function. 

The Axial Skeleton

Vertebra structure/form

Spool/disc-shaped body called centrum, with a neural arch above the centrum. The centrum and neural arch leave an opening called the neural canal, this is where the spinal nerves run. Vertebral processes extend from the centrum or neural arch and provide attachment surfaces or sometimes articulation surfaces for ribs. Includes:

• Transverse processes- extend from lateral sides

• Spinous processes- extend upward from neural arch

Vertebrae shapes may vary throughout the the vertebral column. In dinosaurs and mammals, its very different shapes in different regions.

Vertebrae in different regions:

• Cervical vertebrae (neck)

Have extra large openings for blood and nerve channels and supports the weight of an animals head

• Dorsal vertebrae (back) (largest ribs are those that connect to the dorsal vertebrae and form the rib cage, plus in dinosaurs, all dorsal vertebrae connect with ribs) 

Have tall spinous processes and large rib articulation surfaces

• Sacral vertebrae (hips)

Pelvic bones are fused to the sacral vertebrae to provide strength to anchor powerful leg muscles. Sacral vertebrae fused together to form single bone called sacrum, this further increases strength 

• Caudal vertebrae (tail)

Chevrons are bones found underneath the caudal vertebrae that protect a large blood and nerve channel and provide support for tail muscles. 

In dinosaurs, all these vertebraes may all support ribs!!! 

Some dinosaurs had Gastralia (belly-ribs) 

The Appendicular Skeleton 

Tetrapod- Animals that evolved from an ancient ancestor with four feet and four limbs.

Dinosaurs, mammals, reptiles and amphibians all belong to the tetrapod group. However, there are some exceptions, for example, humans have hands instead of front feet and snakes have ni limbs at all. 

Limb girdles- connects the limbs of a tetrapod to the rest of the skeleton

• Forelimbs connect to the pectoral girdle (also known as the shoulder girdle). The scapula is the largest bone in each side of the pectoral girdle. 

• Hindlimbs connect to the pelvic girdle (also known as the hip bones)

Each side of the pelvic girdle consists of three bones tightly connected to each other:

Ilium, the upper hip bone. Sacral vertebrae are fused here, pubis (front of the ischium, nearer to the belly) and ischium (behind the pubis, nearer to the tail) (both parts are below the illuim). 

The acetabulum, is the hole in the pelvic girdle where the hind limbs articulate. 

FORELIMBS

Humerus- Largest bone in the forelimb, found between shoulder and elbow

Between the elbow and wrist are two parallel bones, called the radius and ulna

Carpals- The bones of the wrist 

Metacarpals- Bones between the wrists and fingers

Phalanges- Finger bones 

HINDLIMBS

Femur- Largest bone in the hindlimbs, found between the hip and knee

Between the knee and the ankle are two parallel bones, called the fibula and tibia (tibia is the bone that form the shin)

Tarsals- Bones in the ankle

Metatarsals- Bones between the ankle and toes

Phalanges- Toes bones

Changes in limb posture can impact the way tetrapods move

FUN FACT: When dinosaurs stood and walked, only their toes touched the ground

Identifying the two major types of pelves in dinosaurs:

Skeletal differences and similarities are used to sort dinosaurs into groups. 

Groups of dinosaurs: 

• Saurischian- Those that share an evolutionary ancestor that had a pubis that extended downwards and forwards, towards the ribcage.

A way to remember this is “soar”, ie. soaring forward

• Ornithischian- Those that share an evolutionary ancestor that had both a special beak-forming bone in the upper jaw (called the predentary) and a pubis that extended downwards and backwards, towards the tail. 

SAURISCHIANS 

• Sauropodomorphs- Large hebivores, elongated necks and small heads

• Prosauropods- Early group of sauropodomorphs and were the first group of large-bodied herbivorous dinosaurs to evolve

• Sauropods- Later group of sauropodomorphs. They attained gigantic size and includes the largest animals to ever walk the earth. Characteristics: 

Stood on four robust and column like legs

Their vertebrae are filled with complex air sacks, which helped them to reduce weight

Their teeth are usually simple and peg- like

• Theropods- Bipedal saurischian dinosaurs that shared a carnivorous ancestor. Characteristics: 

Many theropods were carnivorous and had blade like teeth and sharp hooked claws. (Some were herbivous and lacked teeth all together)

FUN FACT: Birds are a kind of theropod making theropods the only type of dinosaur that are not completely extinct.

ORNITHISCHIANS 

The backwards extending pubis is an adaptation that created more space in the rib-cage, extra space was filled by extra-large organs, especially because plant-matter is much harder to digest than meat. 

All known ornithischians dinosaurs are thought to have been primarily herbivorous. 

The beak is also an adaptation that helped them chop off large mouthfuls of vegetation. 

Majour groups within ornithischains:

• Ornithopods: Dinosaurs that lack armour and that either walked bipedally all the time or assumed a bipedal stance when running. Many are small but could be big like the Iguanodonts 

• Hadrosaurs: Duckbilled dinosaurs. They evolved a bit later and some have elaborate bony chests but ALL have strikingly large beaks in the front of their mouths, dense, tightly packed rows of small teeth in the rear of their mouths. The teeth form large chewing surfaces, collectively referred to as dental batteries

• Pachycephalosaurs: Bipedal with short arms, stout with strong tails.  Some pachycephalosaurs have thick, domed skull roofs and backwardspointing horns (speculated adaptation of thick skull: rammed predators or butted heads). They have sharp conical teeth in the front of their mouths, behind their beaks, and leaf-shaped teeth in the rear.