Defining Definition
Some would say it's all they want for Christmas - this type of tooth type (scientific term) is exaggerated and key for digging or gnawing through soil or plant material
What are incisors
Swing it at a baseball, or be the lone true flapping flyer in the lineage:
What is a bat
This is the lone extant taxonomic class of synapsid amniotes:
What is Mammalia
These paired ventral morphological structures are typically seasonally enlarged in mammal moms:
What are mammary glands
Mammals evolved from this ancient lineage, an alliterative sister taxon to sauropsids:
What are synapsids
Some may call them a police-dog unit, but these evolved in carnivorous mammals to slice meat and signal dominance:
What are canines
To our (fossil and phylogenetic) knowledge, all extinct mammals had this conserved locomotory style, grounded firmly in four feet:
What is quadrupedal
Armored, ancient, and an appropriately alliterative common name for this order:
What is Cingulata
These are believed to be the cellular structures from which mammary glands evolved:
What are hair follicles
The origin of mammals dates back to this era, as if they too could have been placed alongside T. rex on Isla Nublar in the movies:
What is the Jurassic
This synapsid lineage claims heterodonty as one of their prized Mesozoic innovations:
Who are the therapsids
As agile amblers, the earliest mammals were thought to have lived in this type of habitat and bestowed mobile quadrupedal locomotory abilities on their descendants:
What is arboreal (or tree-dwelling)
This mammal infraclass is the contemporary winner of the species-richness race:
What is Eutheria
On a hot summer day, your dog will pant, a kangaroo will lick its skin, but you can rely on these to avoid overheating:
What are apocrine or exocrine glands
Pre-mammal synapsids were the first to evolve hair and likely used it for this additional function beyond thermoregulation:
What is (tactile) sensation
Present even in the first mammals, this condition involving two sets of teeth permitted young and old animals to feed appropriately on milk and chewable food, respectively:
What is diphyodonty
Who needs arms when marine Carnivorans can swim with these alliterative pair of homologous locomotory structures:
What are forelimb flippers
Your 'dead uncle', this extinct mammal subclass is appropriately named for their complex. mult-cusped teeth:
What is Allotheria
Sebaceous glands 'cook' up this special substance to keep mammal hair and fur supple and waterproof:
What is oil (or sebum)
Skull bones and muscles underwent major change during synapsid evolution, including enlargement of this religious-sounding and alliterative lower-jaw structure:
What is masseter muscle
Herbivore ungulates have among the most bizarre dental specializations, including hypsodonty, cementum, and this additional tooth trait, though not directly pertinent to chemistry and physics like the term suggests:
What is molar fusion
This morphological modification accompanied synapsid evolution for upright locomotion; or, a short story:
What is a reduced tail
The "single-holed" mammals share this symplesiomorphic reproductive mode with non-squamate reptiles:
What is oviparity (or egg laying)
The three M words that break the rules, these are the two specific groups of mammals who lack mammary glands:
Monotremes and male marsupials
As if prepared for an adventure at sea, this nickname for an ancient synapid lineage probably better captures the ways they stayed warm or showed off:
What are sailbacks