Paleo 203 Final

Sauropterygia (informally, sauropterygians)

A group of aquatic diapsids best known for their most derived memebers- the plesiosaurs. Name means "winged lizard" in reference to their four large wing-like flippers. Fully aquatic by the end of the Triassic, extinct during end-Cretaceous

Lower temporal bar

a segment of bone that forms the bottom edge of the lower temporal fenestra.

Polytomy

A node in a phylogenetic tree that leads to more than two branches. Sauropterygians could be in lepidomorpha or related to archosauromorpha

Scapula

The technical term for the shoulder blade.

Dorsal

The back, or upper side, of an organism.

Clavicle

The technical term for the collar bone.

Ventral

The abdominal, or under side, of an organism.

Sauropterygian Skull

Defended from diapsids, modified euryapsids, lost temporal bar means a whole is still present but its not a fenestrae

The 5 Sauropterygian Clades

Placodontia, pachypleurosauria, nothosauria, pistosauria, pleasiosaurs

Sauropterygian Pectoral Girdle

All bones located on the ventral side of the body, plate like scapula overlaps the clavicle, increased muscle attachment

Placodontia (informally, placodonts)

A group of durophagous Triassic marine reptiles. There were two major grous: the Placodontoids and the Cyamodontoids. “Plate teeth” flat plate on mouth roof with protruding front teeth, paddled in shallow water, webbed feet or less developed paddles, appendicular loccomotion

Placodontoids

The clade of placodonts with a barrel-shaped morphology and compressed tails, dense gastrailia to add mass. Includes genera such as Placodus and Paraplacodus.

Placodus and Paraplacodus

Placodontoids, with rows of spines in the middle of the back

Cyamodontoids

The clade of placodonts with flattened, armored bodies (convergent to turtles). Includes genera such as Henodus, Cyamodus and Placochelys. Carapace covered in keratin, grew from bony tissue deposits in the skin (turtles grew from rib expansion)

Keratin

The structural protein that is the main component of horns, hooves, hair and fingernails.

Nothosauroidea (informally, nothosaurs)

A group of basal Triassic sauropterygians with elongate bodies and tails, retracted nares, and webbed feet. Crawled on shore like seals, curved humerus that is not good for supporting weight. Long teeth for squid and small fish. Includes genera such as Lariosaurus and Nothosaurus.

Pachypleurosauria (informally, pachypleurosaurs)

A group of basal Triassic sauropterygians with thickened, pachyostotic ribs and poorly ossified limb girdles. Non efficient paddles, ate small fish and squid in shallow water. Includes genera such as Keichousaurus (spent time on land). Unknown phylogeny - had derived and basil traits

Pistosauroidea (informally, pistosauroids)

Thought to be the sister taxon to the Plesiosauria, poorly known clade. They had a nothosaur-like body and a plesiosaur-like head. Larger limb girdles, hyperphalangy, stronger swimmers

Plesiosauria (informally, plesiosaurs)

1. The group of sauropterygians more derived than the Pistosauroidea. They are characterized by broad, plate-like limb girdles, gastralia and subcentral foramina. Evolved at end of Triassic, only group to survive Triassic sea level fluctuations
2. The outdated clade that contained all of the long necked sauropterygians. It is now understood that this is not a true phylogenetic relationship.

2 Plesiosauria morphotypes

1. Elasmosauromorphs - small head, long neck, delicate pointed teeth
2. Pliosauromorphs - large head, short neck, big teeth

Taxonomy

The system that is used to name and classify organisms.

Valid

A valid species names meets two criteria. First, it must identify a distinct species with diagnosable differences that distinguish it from all other species. And second, the combination of genus and species names must be unique to that species.

Pliosauria (informally, pliosaurs)

The outdated clade that contained all of the large headed sauropterygians. It is now understood that this is not a true phylogenetic relationship.

Morphotype

A grouping based on morphological similarity rather than phylogenetic relationships. Useful for talking about convergent lifestyles in similar looking animals.

Pistosauria (informally, pistosaurs)

The clade comprised of the Pistosauroidea and the Plesiosauria.

Diagnostic character

A physical feature which all members of a given phylogenetic group have, which differentiates them from species not in that group.

Subcentral foramina

A pair of holes in the ventral surface of plesiosaur cervical vertebrae that allowed the passage of nerves. A diagnostic character of the Plesiosauria.

Archaeonectrus rostratus

A primitive Triassic plesiosaur that does not belong to the Pliosauroidea or the Plesiosauroidea. Shows some hyperphalangy.

Attenborosaurus conybeari

A primitive Triassic plesiosaur that does not belong to the Pliosauroidea or the Plesiosauroidea. The genus is named after David Attenborough, the species after William Conybeare.

Diagnostic Plesiosauria Charcteristics

1. Scapula verticals to clavicle
2. Pectoral/pelvic griddle were broad plates in abdominal wall, support long narrow flippers
3. Gastrailia not attached to spinal column
4. Subcentral foramina

Pliosauroidea (informally, pliosauroids)

One of two major lineages within the Plesiosauria. Contains the Pliosauridae and the Rhomaleosauridae. Members typically showed the pliosauromorph body plan and were characterized by a lower jaw connected by a short joint.

Pliosauridae (informally, pliosaurids)

A Jurassic to Late Cretaceous sauropterygian family within the Pliosauroidea. They had massive heads and short necks with short snouts. Included genera such as Liopleurodon, Pliosaurus, Kronosaurus, Peloneustes, and Brachauchenius. 2 halves of lower jaw connected by a short joint between few massive front teeth

Rhomaleosauridae (informally, rhomaleosaurids)

An Early to Mid-Jurassic sauropterygian family within the Pliosauridae. Had large flippers, fairly long necks, short snouts and a long tail. Large limb girdles with long flippers. Includes genera such as Borealonectes.

Liopleurodon

Pliosauridae, one of the largest plesiosauromorph in the Jurassic , small teeth with sharp cutting edges to hunt large fish and marine reptiles

Kronosaurus

Pliosauridae, one of the largest plesiosauromorphs, very large smooth teeth without cutting edges, named after Kronos, only swallowed prey whole

Plesiosauroidea (informally, plesiosauroids)

One of two major lineages within the Plesiosauria. Contains the Cryptoclidia, Elasmosauridae and Plesiosauridae. Characterized by a lack of nasal bones.

Plesiosauridae (informally, plesiosaurids)

A sauropterygian family within the Plesiosauroidea. Typified by the first described plesiosaur: Plesiosaurus. Wastebasket taxon, first discovered by Mary Anning

Wastebasket taxon

A clade that contains many unrelated specimens that have been grouped together because they look vaguely similar and/or because researchers did not know where else to assign them.

Elasmosauridae (informally, elasmosaurids)

A sauropterygian family within the Plesiosauroidea. Characterized by long necks that have at least 40 cervical vertebrae and tiny heads that evolved convergently. Diversified in Cretaceous oceans. Needle like teeth for small fish and squid. Bay shaped indentation in pectoral girdles. Include genera such as Elasmosaurus, Albertonectes, Terminonatator and Cimoliasaurus.

Cryptoclidia (informally, cryptoclids)

A clade of sauropterygians within the Plesiosauroidea characterized by a small clavicle hidden in a depression on the inner surface of the shoulder girdle, arrangement of bones in roof of mouth. Evolved in Jurassic, includes all body types. This clade contains the Cryptoclididae, Leptoclididae and Polycotylidae.

Type genus

The genus that a family is named after. Usually, it is the first, and most important, genus in the family.

Type species

The species that a family is named for. Usually it is the first species discovered and described within that family.

Cryptoclididae (informally, cryptoclidids)

A Jurassic sauropterygian family within the Cryptoclidia. Small head and long neck. Triangular arrangement of bones in the mouth. Includes the genera Muraenosaurus, Tatenectes and Cryptoclidus, which is one of the most common plesiosaur fossils in the world.

Leptocleididae (informally, leptocleidids)

A Cretaceous sauropterygian family within the Cryptoclidia. They have fairly large heads, short necks, and a crest on the skull. Narrow teeth, jaws not expanded in front, longer joint between 2 hales of the jaw, small. Includes the genera Umoonasaurus and Nichollsauria.

Polycotylidae (informally, polycotylids)

A Cretaceous sauropterygian family within the Cryptoclidia. They have fairly large heads, short necks, and a crest on the skull. Narrow teeth, jaws not expanded in front, longer joint between 2 hales of the jaw, small. Includes the genus Polycotylus and Trinacromerum.

Modern analogue

An extant animal with a similar morphology to an extinct animal, which is assumed to have similar physiology and/or behaviours. Used to determine plesiosaur locomotion

Plesiosaur locomotion

Appendicular - unique 4 large flippers to generate thrust, not axial because: short stubby tails, rigid body due to ribs and gastrailia, no

Underwater flying

A locomotion style seen in some appendicular swimmers such as sea turtles. It is the same figure-eight motion seen in a bird's wing as it flies. This style generates lift continuously through the motion. Modified version in plesiosaurs because of restricted upward shoulder movement

Rowing

A locomotion style seen in some appendicular swimmers such as seals. The broad edge of the limb pulls backward horizontally to generate thrust, and the narrow edge moves forward in the recovery stroke. Not seen in plesiosaurs because flippers could not move upward and behind back

Paddling

A locomotion style seen in some appendicular swimmers such as ducks. The limbs are pulled broad-side through the water in a vertical plane to generate thrust.

Aspect ratio

The length divided by the width. A measurement that influences energy efficiency and manoeuvrability in a wing or flipper.

Elasmosaur Flippers

Long and thin with a high aspect ratio, good for long distance cruising, ambush prey after swimming long distances. Increased lift, increased drag because of large surface area

Pliosaur Flippers

Big, broad and short flippers, low aspect ratio, fast manoeuvring, chased prey, turned quickly, decreased drag, more energy needed to stay afloat because of decreased lift, evolved convergently

Hydrofoil

A cross-sectional shape of a flattened oval, where the base is flat and the upper surface is curved. Seen in wings and flippers that generate lift in the water. The same shape in air is called an airfoil.

Lift

The force that pulls an object up.

Angle of attack

The direction in which an airfoil or hydrofoil points in order to change the direction in which the force of lift is generated.

Plesiosaur Body

Smooth skin, streamlined, almond shape (5 and 1/2 times long as it is wide) rigid bodies (stiff bc shoulders, ribs, gastrailia, appendicular flying swimmers, muscles pull limbs down and back, with limited forward movement.

Plesiosaur Flippers

Less degree of hyperphalangy (16) phalanges fixed with strong connective tissue and cartilage, elbows, wrists flippers were all stiff

Elasmosaurus Necks

Necks cause a lot of inertial drag, bad for speed and steering, thick rigid muscles at the bottom of the neck to correct steering issues, upward curve increases lift and help breathe, to heavy to lift above water, dorsally positioned nostrils

Hydrodynamic Head Position

Neck held out in front instead of upright, increase drag because of increased surface area, but the body has less drag because of this, needs smooth, consistent swimming motion like flying, acceleration and deceleration causes stiff neck to jerk around

Modified Flight Clues

1. Downward and backward motion of muscles
2. Range of motion in shoulder and arm sockets (best supports underwater flying but recovery stroke restricted, rowing prohibited)
3. Rigid body -rigid thorax and gastailia
4. Hydrofoil cross-section of a flipper
5. Long neck - benefits from underwater flying

Modified Flight

Done and power structure provide lift and thrust for flying, horizontal recovery like rowing, moved in synchronization, front limbs provide thrust, back limbs provide steering, glided between strokes with front flippers

Adaptations for Hunting Underwater

Bony rings in eyes to support eye pressure and adjust aperture, no eardrum, detects vibrations from inner ear to skulls, scoop shaped openings in roof of mouth to direct water into sense receptors, water flows out of nostrils (Like sharks)

Sauropterygian Reproduction

Originally thought to be oviparous, not true because necks to heavy and flippers could not drag body across land, Actually viviparous. Keichosaurus - pachypleurosaur found with embryo in body

Polycotylus- derived plesiosaur found with 1.5m long embryo inside body

Parental care for one big baby at a time, maybe lived in groups of extended families, lost of baby plesiosaurs found in Australia - probably a breeding ground

Sauropterygian Evolution

Longest lived in all 3 lineages of marine reptiles, originated and diversified in early Triassic, near-shore form extinct by end of Triassic, fully aquatic dominated Jurassic, reduced in Cretaceous seaways

Endemism

When a species is only found in one place, such as a nation, an island, a cave or a body of water.

Sauropterygian Early Triassic

Lived in shallow Tethys sea, evolution tied to rising sea levels, continental flooding during Triassic, marine basins favour endemism, unspecialized forms similar to pachypleurosaurs, got cut off when ocean basins became isolated due to sea level fluctuations, lead to diversity

Sauropterygian Early Triassic

Sauropterygian Middle Triassic

Collection bias compared to early Jurassic, placodonts, nothosaurs, pachypleurosaurs and pistosaurs inhabited same shallow seaways, all had similar morphologies except for placodonts, semi-aquatic with long distance swimming, survived through niche portioning

Sauropterygian Middle Triassic

Sauropterygian Late Triassic

Plesiosaurs evolved from pistosaur ancestors and lived in open oceans, fossils from southern England and Ghizou in China (thought they were dragons) shared seas with basal Sauropterygians till extinction events, shallow sea environments lost

Sauropterygian Late Triassic

Niche partitioning

When species use different spaces or resources within their ecosystems in order to avoid competition with each other.

Collection bias

When data (such as fossils) are collected in such a way that some are less likely to be collected than others.

Sauropterygian Early Jurassic

Plesiosaurs diversified, had unspecialized ancestors that looked like Attenborosaurus and Archaeonectus, Rhomaleosaurids first group to become widespread worldwide, Mary Anning found first plesiosaur fossils

Sauropterygian Early Jurassic

Sauropterygian Middle Jurassic

Pliosauridae replaces Rhomaleosaurids as top predators, cryptocleidia diversified (cryptoclidus and peloneustes found in oxford and Kimmerdige clays in UK in middle/upper Jurassic strata),found with dinos, thalattosuchians and plesiosaurs. Borealnectes russelli Rhomaleosaurids found in artic of Northwest Territories (best preserved skull)

Sauropterygian Middle Jurassic

Sauropterygian Late Jurassic

Global sea level rises, Sundance sea formed, Cryptoclidid Tatenectus laramiensis was well adapted to shallow water with a wide and flat body like a turtle. Cryptoclidids went extinct during marine Tithonus extinction at end of Jurassic, some pliosauria survived into the Cretaceous

Sauropterygian Late Jurassic

Sauropterygian Early Cretaceous

Marine deposits poorly known, leptocleidids plesiosaurs from Germany and UK, probably collection bias

Sauropterygian Early Cretaceous

Sauropterygian Mid Cretaceous

Elasmosaurids developed and diversified, evolved in southern hemisphere (Columbia and Australia), cryptocleidia survived until after half of the Cretaceous, leptocleidid Nichollsaura borealis replaces by polycotylids

Sauropterygian Mid Cretaceous

Sundance Sea

A waterway that bisected North America in the mid-Jurassic.

Western Interior Seaway

A transcontinental ocean that separated North America into two continents during the mid-late Cretaceous. It stretched from the Gulf of Mexico to the Arctic Ocean.

Trans-Saharan Seaway

An epicontinental waterway that bisected Northern Africa in the Late Cretaceous.

Aristonectidae

A possible family of elasmosauromorphs from the Southern Pacific.

Sauropterygian Late Cretaceous

Decreased diversity, ploycotylidae and elasmosauridea survived until end-Cretaceous, Brachauctenius - 1 of 2 last pliosaur mega predator and went extinct when mosasaurs appeared, western interiors sea formed, Trinacromerum polycotylids had longest flippers ever (equal to length of vertebral column, elasmosaurs widespread with fossils on every continent

Important Elasmosaurids during Late Cretaceous

Clade Aristonectidaw found in South America, New Zealand and Antarctica. Terminonator ponteixensis found in Saskatchewan as an immature adult, Albertonectes vanderweldi found in Alberta had the most cervical vertebrae. Cimoliosaurus was the longest plesiosaur fossil in the Northwest territory

Sauropterygian Late Cretaceous

Mosasauroids

A group of aquatic lepidosaurs from the Late Cretaceous. Best known for the most derived members, the mosasaurs.

Mosasaur Skull

Diapsid, lost bone that forms lower temporal fenestrae, open space remained, Kenetic skull like snakes

Mosasaur Lineage Hypotheses

1. Part of Varanoid lizards (monitor lizards like Komodo dragon)
2. Part of anguimorph lizards
3. Part of pythonomorpha (probably sister group to snakes)

Part of lepidosauromorphs and squmates

Baron Georges Cuvier

Known as the father of comparative anatomy and palaeontology.

Squamata (informally, squamates)

The group of lepidosaurs that includes all modern lizards and snakes.

Anguimorpha (informally, anguimorphs)

The group of lepidosaurs that includes extant animals such as alligator lizards, glass lizards and legless lizards.

6 ages of the Cretaceous

Cenomanian, Turonian, Conician, Santonian, Campanian (longest age), Maastrichtian

Intramandibular joint

A joint in the middle of each lower jaw of mosasauroids and snakes that helps expand the gape of the animal during feeding. Joint between 2 halves of jaws suppoted by back half of the teeth, allows lower jaw to bend in the middle to expand

Intermandibular joint

The connection point between the two halves of the lower jaw, found at the front of the mouth. 2 sides of lower jaw did not fuse, held together by soft ligaments, allows two sides of jaw to separate slightly