Lesson 2 Vocab: Ichthyopterygians

Ichthyopterygia (informally, ichthyopterygians)

A group of aquatic diapsids best known for their most derived members- the ichthyosaurs.

Euryapsid

A skull condition with one temporal opening, derived from the diapsid condition. Developed in ichthyopterygians when the lower temporal fenestra disappeared due to reduction of the back part of the skull.

Thalattosauria (informally, thalattosaurs)

A group of semi-aquatic marine reptiles that lived during the mid-late Triassic period. Thought to be closely related to the icthyopterygians. Includes genera such as Miodentosaurus.

Hupehsuchia (informally, hupehsuchians)

A group of small Triassic diapsids that may be closely related to ichthyopterygians. They have long, pointed snouts lacking teeth, and have a unique osteoderm pattern along the top of the vertebral column. Includes genera such as Hupehsuchus and Parahupehsuchus.

Osteoderm

Plate-like or scale-like bony deposits in the skin.

Gastralia

A series of long slender bones found in the ventral region of the body that provide support and protection to the abdomen and can serve as muscle attachment sites. Also known as "belly-ribs".

Diagnostic characters

Features, or sets of features, that are unique to a group and differentiate them from other lineages.

Articulate

When bones fit together and form a joint or suture.

Amphicoelous

A type of vertebral shape where both articulating surfaces are concave.

Plicidentine

A type of tooth tissue in ichthyopterygians where the inner tooth tissues have a distinct folded pattern.

Centrum

The solid central part of a vertebra, to which the processes and spines are attached.

Fluted

Grooved. With the appearance of having columns.

Process

On a vertebra, a bony projection that branches off of the centrum.

Neural spines

Arched vertebral processes that protect the spinal cord and provide sites for muscle attachment.

Parvinatator

Basal ichthyopterygian from Canada.

Utatsusaurus

Basal ichthyopterygian. Thought to be the oldest ichthyopterygian yet found.

Omphalosaurus

Basal ichthyopterygian more derived than Parvinatator and Utatsusaurus.

Grippiidae

A family of basal Early Triassic ichthyopterygians, with small tail flukes and an anguilliform swimming style. Includes genera such as Grippia, Chaohusaurus and Gulosaurus.

Ichthyosauria

All ichthyopterygians more derived than the Grippiidae family. United by nares that face sideways, and disc shaped vertebrae in the rear portion of their torso.

Cymbospondylus

A basal member of the Ichthyosauria. First large ichthyosaur at ten metres.

Mixosaurus

A basal member of the Ichthyosauria. One of the most common Triassic ichthyosaurs.

Thalattoarchon

An ichthyosaur basal to the Euichthyosauria. Thought to be the first ichthyosaur that occupied the apex predator niche.

Shastasauridae (informally, shastasaurids)

A family of ichthyosaurs. Some members of this clade were the largest ichthyosaurs to ever live. Adults had no teeth. Includes genera such as Shastasaurus and Shonisaurus.

Euichthyosauria

The clade of ichthyosaurs containing all members more derived than the shastasaurids. All members of this group had teeth in grooves, not sockets.

Parvipelvia (informally, parvipelvians)

A derived group comprising most of the ichthyosaurs within the Euichthyosauria. This group is characterized by a reduced pelvic girdle, hyperphalangy, and a fusiform body plan.

Leptonectidae (informally, leptonectids)

An ichthyosaurian family at the base of the parvipelvian lineage. The long narrow snouts in this group could become specialized into a swordfish-like morphology. Includes genera such as Excalibosaurus and Eurhinosaurus.

Occlude

The condition where teeth interlock with each other.

Temnodontosaurus

A member of the Parvipelvia. A very large ichthyosaur.

Reassign

Where the taxonomic placement of a clade is found to be false, and the clade is moved to a new position within the phylogeny.

Thunnosauria (informally, thunnosaurs)

All ichthyosaurs more derived than Temnodontosaurus. This group had front flippers at least two times longer than their back flippers. Includes genera such as Cetarthrosaurus, and families such as Ichthyosauridae and Ophthalmosauridae.

Ichthyosauridae

A family of thunnosaurs. Included genera such as Ichthyosaurus and Malawania.

Stenopterygius

A thunnosaur ichthyosaur. Thousands of specimens have been discovered.

Ophthalmosauridae

A thunnosaur family containing the Ophthalmosaurinae and the Platyterygiinae. The most derived ichthyosaur family.

Ophthalmosaurinae

A sub-family of thunnosaurs. Members such as Ophthalmosaurus, Acamptonectes and Leninia had the largest relative eyes of any ichthyosaur.

Platyterygiinae

The latest surviving sub-family of ichthyosaurs. Showed extreme hyperphalangy and hyperdactyly. Included genera such as Platyterygius, Aegirosaurus, Sisteronia and Sveltonectes.

Sclerotic ring

A ring of bone inside the eyes that helped to support and focus the eyeball.

Ram feeding

A type of underwater feeding strategy where the predator moves through the water with its mouth open, engulfing the prey and the water surrounding it. Also known as filter feeding.

Lunge feeding

A type of ram feeding where a predator takes in a large mouthful of prey and water, and then pushes the water out through a filter such as baleen, leaving the prey in trapped in the mouth.

Baleen

A fibrous material that has replaced the teeth of some whales. Used a filter during lunge feeding.

Filter feeding

See ram feeding.

Manipulation

A feeding strategy where teeth are the instruments used to capture prey.

Feeding guilds

Groups of species, not necessarily closely related, that use similar resources in their environments.

Crush guild

An aquatic feeding guild whose members possess robust teeth for crushing hard-shelled prey such as molluscs. See feeding guild.

Smash guild

An aquatic feeding guild whose members possess small teeth with rounded points for eating soft-prey such as squid. See feeding guild.

Pierce guild

An aquatic feeding guild whose members possess long, pointed teeth for trapping and piercing small, slippery prey such as small fish. See feeding guild.

Cut guild

An aquatic feeding guild whose members possess pointed teeth with cutting edges for tearing apart large prey. See feeding guild.

Apex predator

A predator at the top of the food chain, which no other organism can predate on.

Heterocercal

A tail shape where one lobe is longer than the other.

Homocercal

A tail shape where both lobes are approximately the same length.

Hyperphalangy

The condition where the digits of an organism have more phalanges than seen in the ancestral state.

Hyperdactyly

The condition where an organism has more digits (fingers or toes) than seen in the ancestral state.

Avascular necrosis

The death of bone tissue caused by a lack of blood supply leading to tiny breaks in the bones, and areas of collapse. In diving animals, can be caused by a rapid ascent, when dissolved gases in the blood form bubbles that block blood vessels.

The Bends

A condition in diving animals where rapid ascent can lead to blood supply being cut off. Also known as decompression sickness. See avascular necrosis.

Photoreceptors

The structures or cells, such as those that line the back of the eyeball, that respond to light.

Aperture

The space through which light passes in an optical instrument such as the eye.

Endothermy

Generation ad regulation of body heat using the body's metabolism. This property is also known as being warm-blooded.

Ectothermy

Regulation of body heat using external sources such as the sun. This property is known as being cold-blooded.

Viviparous

Where an animal gives birth to live young that have developed inside the body of the parent.

Oviparous

Where an animal lays eggs that then hatch after they have been laid.

Dinoflagellate

A single-celled organism found frequently in marine environments. Some produce toxins that can poison fish and other sea creatures when found in high concentrations, such as a red tide. See red tide.

Red tide

A large abundance of toxic dinoflagellates. They bloom in such high concentrations that the water appears red.

Gregarious

Animals lives in groups or communities.

Niche

The role an organism plays in its ecosystem.

Evolutionary bottleneck

When extinction reduces the number of individuals within a group, the number of species that make up a group (the diversity), the variety of morphologies within the group (the disparity), or a combination thereof.

Laggerstatten

A deposit of extraordinary fossils with exceptional preservation, sometimes including soft tissues.

Mary Anning

A young woman from the early 1800s of England. She was a fossil collector, dealer and paleontologist, and was responsible for many discoveries including the first correctly identified ichthyosaur, the first two plesiosaurs, the first pterosaur found outside of Germany, and numerous other discoveries.

Holzmaden

A laggerstatten from Germany preserved in shale. It is most famous for the large number of exquisitely preserved ichthyosaurs showing skin, muscle fibres, body outlines, embryos, and stomach contents.

Solnhofen

A limestone laggerstatte from southern Germany. Most famous for producing ichthyosaurs and the original Archaeopteryx specimen.

Collagen

A connective tissue in animals that is the main structural protein of the body, providing strength and flexibility.