Deuterostomes - Birds and Mammals Lecture Notes

Flashcards covering the origin, characteristics, and classification of birds and mammals as discussed in the Deuterostomes lecture.

K-Pg mass extinction event

A mass extinction event occurring approximately $66$ Ma ago, likely caused by an asteroid impact, which led to the extinction of non-avian Dinosaurs and provided opportunity for survivors.

Synapsida

The amniote lineage characterized by a skull with a single pair of lateral temporal openings; this group includes mammals.

Diapsida

The amniote lineage characterized by a skull with both dorsal and lateral temporal openings; this group includes birds and most reptiles.

Theropod dinosaurs

The bipedal, generally carnivorous lineage of dinosaurs that includes $T. rex$ and Velociraptor, from which birds are specialized descendants.

Archaeopteryx

Generally considered the first bird, living approximately $150$ Ma ago (late Jurassic), displaying both reptilian traits like teeth and a tail, and avian traits like feathers.

Keel

The enlarged sternum or breastbone in modern birds that serves as an attachment point for flight muscles.

Neornithes

The group containing all living birds.

Ramphotheca

The external sheath of keratin that covers the internal bony structure of a bird's beak.

Air sacs

Structures in the avian respiratory system that contain and exchange air but do not perform gas exchange; they help maintain a one-way flow of air through the lungs.

Palaeognathae

Also called ratites, this group includes ostrich, emu, tinamous, kiwi, cassowaries, and rheas; most are flightless except the tinamous.

Passeriformes

The order of birds that comprises more than half of all extant bird species.

Dentary

The single bone that constitutes the mandible (lower jaw) in mammals.

Ear ossicles (mammalian)

Three bones in the middle ear formed through skeleton modifications; specifically, the quadrate and articular bones became the incus and malleus.

Heterodont

A type of dentition involving specialized teeth of different shapes and sizes in the same mouth.

Diphyodont

A type of dentition where teeth are replaced only once during an organism's life.

Cynodonts

Stem-mammals characterized by a complete secondary palate, turbinate bones for body heat retention, and heterodont teeth.

Vibrissae

Specialized hairs (whiskers) used for the tactile sense of touch.

Placenta

A structure connecting the embryo and the uterus wall in mammals for nutrient exchange, gas exchange, and waste elimination.

Monotremes

Oviparous (egg-laying) mammals, such as the platypus and echidnas, which lack nipples and secrete milk onto the fur of the mother's belly.

Metatheria (Marsupials)

Mammals where newborns are highly underdeveloped at birth and must complete their development while attached to the teat of the mother.

Eutherians

Placental mammals that are more developed at birth than marsupials and represent roughly $5,300$ species across $20$ groups.