Lesson 3 Vocab: Sarcopterygians

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.

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.

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.

Placodontia (informally, placodonts)

A group of durophagous Triassic marine reptiles. There were two major grous: the Placodontoids and the Cyamodontoids.

Placodontoids

The clade of placodonts with a barrel-shaped morphology. Includes genera such as Placodus and Paraplacodus.

Cyamodontoids

The clade of placodonts with flattened, armored bodies. Includes genera such as Henodus, Cyamodus and Placochelys.

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, retracted nares, and webbed feet. 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. Includes genera such as Keichousaurus.

Pistosauroidea (informally, pistosauroids)

Thought to be the sister taxon to the Plesiosauria. They had a nothosaur-like body and a plesiosaur-like head.

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.

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 The outdated clade that contained all of the long necked sauropterygians.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

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The outdated clade that contained all of the large headed sauropterygians.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.

Pliosauromorph

The plesiosaur morphotype with large heads, short necks and big teeth.

Elasmosauromorph

The plesiosaur morphotype with long necks, small heads and delicate, pointed teeth.

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.

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. Included genera such as Liopleurodon, Pliosaurus, Kronosaurus, Peloneustes, and Brachauchenius.

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. Includes genera such as Borealonectes.

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

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. 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. 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. 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. 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. 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.

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.

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.

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.

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.

Endemism

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

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.

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.