Trait Pelycosaurs Therapsids Cynodonts Posture: sprawling intermediate upright Teeth: weakly heterodont increasingly heterodont strongly hetero Palate: no secondary palate partial complete “-apsidy” small temporal fenestra enlarged fenestra vastly expanded Postdentary bones: present, large present, reduced absent greatly reduced THIS IS WRONG! SEE LUO ET AL. 2001 SCIENCE PAPER. THE REDUCTION BEGAN IN CYNODONTS BUT WASN’T COMPLETE UNTIL HADROCODIUM.

Mammaliamorpha (transition to cynodonts Mammaliamorpha (transition to dentary-squamosal joint begins) Mammaliaformes (formation of dentary-squamosal “single jaw hinge” complete) Luo et al. 2001. Mammalia: All descendants from the MRCA of living mammals.

Mammalia Mammaliaformes Mammaliamorpha

Completion of dentary-squamosal jaw joint Mammalia (and some mammaliaforms) Completion of dentary-squamosal jaw joint Cheekteeth divided into premolars and molars Diphyodonty BUT TINY! For 170 million years! Paleozoic Mesozoic Morganucodon THESE ARE FOSSILIZABLE CHARACTERS USED TO DIAGNOSE FOSSIL TAXA.

Mammalia: All descendants from the MRCA of living mammals. cynodonts Mammaliamorpha Mammaliaformes Luo et al. 2001. Mammalia: All descendants from the MRCA of living mammals.

Multituberculates (extinct prototherians) Late Jurassic-Mid. Miocene (ca. 150 m.y.) Diverse, found on all continents Ever-growing lower incisors, plagialacoid (blade-like) molariform teeth Outcompeted to extinction? (rodents, early primates...)

Theria (SUBCLASS) Mammalia (CLASS) Mammaliaformes Mammaliamorpha (INFRACLASSES) Prototheria (SUBCLASS) Metatheria Eutheria Theria (SUBCLASS) Mammalia (CLASS) Mammaliaformes Mammaliamorpha

Warren et al. 2008

Extant mammalian diversity Class MAMMALIA Subclass Prototheria Subclass Theria Infraclass Metatheria 1 Order (Monotremata) 2 Families 3 5 species 7 Orders 19 21 Families 272 331 species xx x xxx Infraclass Eutheria xx 18 21 Orders 114 130 Families 4354 5078 species xxx xxxx

The radiation of placental mammals Since end of Mesozoic, placental (eutherian) mammals dominant terrestrial vertebrates on all continents except Australia and Antarctica. When and why did this diversification occur?

“Age of Mammals” K/T boundary “Age of Dinosaurs” Why “K”? For Kreide, the German translation for Cretaceous.

BUT, this has increasingly been challenged, mainly by molecular clock studies but also by some fossils that push the origins of many of these orders back. K/T boundary

Most/all eutherian orders originated & diversify AFTER K/T (traditionally, fossils supported this) Orders originate BEFORE K/T but don’t diversify until (more recently discovered fossils support) Most orders originate & diversify BEFORE K/T (older molecular studies support)

Springer et al. 2003ish. Majority of recent studies support the long fuse. Bininda-Emmonds supertree paper argues that all modern orders diverged by 75 Mya but

Bininda-Emmonds supertree paper argues that all modern orders diverged by 75 Mya butradiations of modern families not till after K/T.

Subclass Prototheria 1 Order (Monotremata) 2 Families Tachyglossidae (echidnas or “spiny anteaters”) 4 species. Ornithorhynchidae (platypus) 1 species

Subclass Prototheria Few fossils, never very diverse. BUT PERSISTED. Echidnas: fossils from 55-60 Mya, oldest in S. AMERICA Platypus: fossils from 120 Mya, oldest in AUSTRALIA (Paleocene fossils in S. AMERICA). Many plesiomorphic features, but some apomorphies.

Subclass Prototheria SKULL FEATURES: •No teeth in living adults BUT fossil platys & living neonates have, then lose. LOSS=apomorphy •No lacrimals (APOMORPHY) •Cranial sutures fused, indistinct (APOMORPHY) •Jugal reduced or absent (APOMORPHY)

Subclass Prototheria SKELETAL FEATURES: •Epipubic bones present, large (PLESIOMORPHY) •Cervical ribs (PLESIOMORPHY) •Horny, hollow spur on inside of ankle (APOMORPHY) •Pectoral girdle with large precoracoids, coracoids, interclavicle (PLESIOMORPHY) •Skeleton sprawling, “reptilian” (PLESIOMORPHY) BUT, good for swimming, digging.

The epipubic bone acts as a lever that is retracted (depressed) to stiffen the trunk between the diagonal limbs that support the body during each step. This cross-couplet kinetic linkage and the stiffening function of the epipubic bone appear to be the primitive conditions for mammals. THEY HELP STIFFEN/STRENGTHEN THE TRUNK THE TRUNK.

TWO ECHIDNAS (LEFT), PLATYPUS (RIGHT)

Platypus venom: coctail of at least 19 different substances Platypus venom: coctail of at least 19 different substances. Several of these mapped onto tree show that ‘local’ duplications of genes with very different functions have occurred convenrgently. whether or not venom unique to platypus or simply lost in echidnas still unknown. Echidnas have the spur in males. Original caption: The diagram illustrates separate gene duplications in different parts of the phylogeny for platypus venom defensin-like peptides (vDLPs), for lizard venom crotamine-like peptides (vCLPs) and for snake venom crotamines. These venom proteins have thus been co-opted from pre-existing non-toxin homologues independently in platypus and in lizards and snakes Warren et al. (2008). Nature 453, 175-183.

All but scapula and clavicle lost in all other mammals.

Subclass Prototheria OTHER FEATURES: •Pouch (echidnas only) •Testes permanently abdominal (no scrotum) •Uteri fused •Leathery egg with nutrient-rich yolk •Rostrum lacks vibrissae, elongate •cloaca (but...) •Endothermic, but low Tb and metabolic rates •Electroreception (snout), including echidnas