Ch.2 & Ch.3 Comparative Vertebrate Anatomy

Vocabulary practice flashcards covering vertebrate evolution, anatomical features, skeletal innovations, tissue types, embryonic coelom formation, and hominid fossil history.

Centrum

The solid cylindrical base of a vertebra that usually encloses the notochord.

Neural arch

The structure located on the dorsal side of a vertebra that encloses and protects the nerve cord or spinal cord.

Hemal arch

The structure located on the ventral side of a vertebra in fishes that encloses and protects blood vessels.

Intervertebral disks

Pads of cartilage or fibrous connective tissue situated between vertebrae that absorb mechanical shock.

Nucleus pulposus

A small, springy, gel-like core within each intervertebral disk in adult mammals, persisting as a remnant of the embryonic notochord.

Cephalization

The evolutionary clustering of specialized sensory organs and nervous tissue in the anterior part of the body.

Cranium

A skeletal structure composed of bone and/or cartilage that supports sensory organs in the head and encloses or partially encloses the brain.

Prevertebrate

The earliest step in vertebrate origin, characterized as a suspension feeder resembling amphioxus that relied on a cilia-mucus mechanism for feeding.

Agnathan

An early vertebrate that lacks jaws and rigid hinged mouth borders, relying on a muscular pump to produce water currents for feeding.

Gnathostome

A vertebrate equipped with opposable jaws adapted for grasping and capturing specific prey items.

Cyclostomes

The group of living jawless vertebrates (agnathans) with round mouths, consisting exclusively of hagfishes and lampreys.

Metamorphosis

An abrupt transformation from one anatomically distinct developmental stage to another.

Yunnanozoon

An early soft-bodied vertebrate fossil featuring protovertebrae and straight myomeres, but lacking a skull and ear capsule.

Ostracoderms

Extinct jawless vertebrates covered in bony dermal armor that were the first vertebrates to possess an extensive lateral line system and bone.

Lateral line system

A sensory system in aquatic vertebrates that detects water movements to assist with orientation and navigation.

Endoskeleton

The supportive or protective internal framework lying within the body beneath the integument (skin).

Exoskeleton

A supportive or protective framework that lies on the outside of the body.

Girdles

Bony or cartilaginous skeletal arches that connect paired appendages (fins or limbs) to the axial skeleton.

Chondrichthyans

Cartilaginous fishes (from chondr- = cartilage and -ichthyes = fishes), including elasmobranchs (sharks and rays) and holocephalans (chimaeras/ratfishes).

Teleostomi

The major gnathostome clade encompassing acanthodians, osteichthyans (bony fishes), and tetrapods.

Chiridium

A muscular limb possessing well-defined joints and terminating in digits, the key distinguishing feature of tetrapods.

Tetrapod

A four-footed vertebrate (from tetra- = four and -pod = foot), encompassing amphibians, reptiles, birds, mammals, and their secondarily limbless descendants.

Amnion

A saclike membrane that encloses the developing embryo in a compartment of protective amniotic fluid.

Amniotes

Vertebrates (mammals, reptiles, and birds) that produce embryos encased within an amnion.

Anamniotes

Vertebrates that lack an amnion during embryonic development, including fishes and amphibians.

Temporal fenestrae

Openings in the temporal region of the skull behind each orbit that define anapsid, synapsid, diapsid, and euryapsid skull conditions.

Extracellular matrix (ECM)

The material located between widely spaced cells in connective tissue, composed of protein fibers and ground substance.

Schizocoelom

A coelomic body cavity formed by the physical splitting of the mesoderm during development, typical of protostomes.

Enterocoelom

A coelomic body cavity formed by an out-pocketing of the primitive embryonic gut, characteristic of deuterostomes.

Clade

A natural evolutionary lineage that includes a common ancestor plus all and only its descendants.

Lineage

A group of individuals or taxa that trace continuous descent from a common ancestor.

Basal group

The earliest diverging lineage located nearest to the root within a clade.

Sister group

The genealogical taxon most closely related to a specific group under study.

Ambulacraria

The deuterostome clade comprising echinoderms and hemichordates.

Natural selection

A natural process that leads to the survival and reproductive success of individuals best adjusted to their environment, perpetuating favorable traits.

Binomial nomenclature

The standardized two-part Latin scientific naming system (genus and species) developed by Carl Linnaeus for classifying living organisms.

Hydrothermal vents

Chimney-like structures on the deep ocean floor that spew superheated, mineral- and nutrient-rich water, supporting ecosystems without sunlight.

Lucy

An early hominid fossil skeleton estimated at 3.2 million years old that provided evidence of upright, bipedal walking.

Laetoli footprints

Fossilized hominid footprints dating to 3.6 million years ago showing that early hominids walked bipedally and traveled in groups.

Toumai skull

The oldest known hominid fossil, dated at approximately 7 million years old, illuminating diversity among early hominids.