Paleo 419 Midterm 2

When did placentals dominate terrestrial habitats?

Mesozoic

When did eutherians first appear?

Early Cretaceous (Yixian Formation)

Eutherian Synapomorphies

• canines with 2 roots

• 3 molars

• lack epipubic bones (except some basal forms)

• have malleolus on distal end of tibia

Eutherian skull characters

• squamosal expanded to form part of the braincase – contacts alisphenoid

• squamosal pierced by blood foramina

• two parts of Trigeminal nerve, CN V2 (maxillary) and

  CN V3 (mandibular), exit through the alisphenoid

Primitive placentals dental formula

3-1-4-3/3-1-4-3

Eutherian dental characters

• four premolars, three molars (some very primitive ones have a fifth premolar)

• last premolar tends toward molariform (not seen in marsupials)

• upper molars have much smaller stylar ridge (cingulum; on lingual side of protocone) with smaller cusps

Eomaia (Eutheria)

• “dawn mother”

• Early Cretaceous Eutheria

• Barremian part of the Yixian Fm., China ~125 Ma

• carbonaceous traces of hair

• last premolar shows tendency towards molarization

Asioryctida (Eutheria) characteristics

• Late Cretaceous

• Incompletely co-ossified atlas ring

• Absence of superposition of astragalus and calcaneum

• Epipubic bone

Leptictida (Eutheria) Characteristics

• Late Cretaceous - Eocene

• Unspecialized dentition; probably 5 premolars (primitive)

• Asia – Kennalestes

• North America – Gypsonictops

Zalambdalestidae (Eutheria)

• Asia (Uzbekistan, Mongolia)

• 3 incisors; first lower incisor procumbent

• enamel only on labial side (possibly related to modern Glires)

Palaeoryctida (Eutheria)

• Late Cretaceous

• Palaeocene

• Cimolestes and Paranyctoides in N. America and Asia in Late Cretaceous

• specialist carnivores

• tendency to develop transversely oriented shearing

  edges on molars

Zhelestidae (Eutheria)

• Late Cretaceous - Palaeocene

• Asia, Europe, North America

• basal members of single ungulate radiation

• small mammals with incipient ungulate molars (broad, subrectangular in shape)

• omnivory (plants & insects) or herbivory

Eutherian survivors of K/Pg extinction

• Leptictida – abundant in North America and also in Europe through Eocene and to Oligocene; China in Palaeocene

• Palaeoryctida – common North America through Eocene

• Zhelestidae – a few teeth still in early Eocene North America

New Palaeocene Placental Groups

• Anagalida

• Mixodonta

• Pantolestida

• Apatemyida

• Plesiadapiformes

• ‘Condylarthra’ = condylarths (carnivorous and herbivorous forms

• Taeniodonta

• Pantodonta

• Tillodonta

• Dinocerata

• ArctostylopidaMeridiungulata (5 groups)

Anagalida (Placentals)

• early Palaeocene, China

• herbivores and omnivores

• procumbent lower incisors

• relationships not clear; maybe with Asian Cretaceous zalambdalestids

Mixodonta (Placentals)

• Palaeocene

• Asia

• small, omnivorous

• gliriform incisors

• Mimotona – dental formula like lagomorphs

• Heomys – dentition like rodents

Pantolestidae (Placentals)

• Palaeocene - Oligocene

• otter-like

• North America and Europe

• well-developed canines

• Eocene Messel Buxolestes with fish in stomach

Apatemyida (Placentals)

• North America and Europe

• early Palaeocene to late Oligocene

• single large, procumbent lower incisor

• large first upper incisor

• bunodont

Plesiadapiformes (Placentals)

• Palaeocene

• North America, Europe

• most small but some up to 5 kg

• some at least arboreal

• related to Euarchontoglires, but maybe not Primates

Condylarths (Placentals)

• Palaeocene - Eocene

• North America

• variety of small primitive members

• larger herbivores and secondarily carnivorous forms

• ancestors of various modern ungulate groups

• paraphyletic; ‘archaic ungulates’

  • crushing molars rather than shearing

  • bunodont

  • incipiently ‘hoof-like’ terminal phalanges

Carnivorous condylarths (Placentals)

• Palaeocene

• North America, Asia; into Eocene

• tendency to evolve higher sharper molar cusps; shearing edges

• first radiation of relatively large, predaceous placentals

• Cete: Triisodontidae, Hapalodectidae, Mesonychidae

Phenacodontids (herbivorous condylarths)

• Palaeocene - Eocene

• premolars enlarged, more molar-like (molars broader)

• digitigrade

• well-developed hooves on each digit

• China & North America

Taeniodonta (Placentals)

• Palaeocene - Eocene

• North America

• omnivorous

• early forms - generalized, non- cursorial, good climber, opossum- like life style

• later forms - gliriform incisors, more powerful build, flattened claws, digger

Schowalteria clemensi (Taeniodonta)

• Scollard Formation Trochu, Alberta

• Late Cretaceous (Maastrichtian)

• Fox and Naylor

• largest Mesozoic mammals

• robust canine with restricted enamel on crown, enlarged incisor I2, structure of zygomatic arch

Pantodonta (Placentals)

• early Palaeocene China; mid-Palaeocene to mid- Eocene NA

• first large herbivorous placentals

• dentition complete (canines present, no diastema)

• V or W shaped lophs on postcanines

Tillodonta (Placentals)

• early Palaeocene – late Eocene China; late Palaeocene – middle Miocene North America; early Eocene Europe

• powerful jaws

• enlarged chisel-like second incisors with enamel only anteriorly

• lost other incisors, canines

• Trogosus

Dinocerata (Placentals)

• Palaeocene - mid-Eocene

• China and North America

• Cope and Marsh

• mid-Eocene, China and North America

• bony protuberances on skull

• reduce or lose upper incisors, and enlarge and protrude upper canines

• browsers, possibly with mobile proboscis

• v-shaped crest on molars

• Digitigrade

Meridiungulata (Placentals)

• Palaeocene - Plio-Pleistocene

• South American native ungulates

• large grinding lophodont premolars and molars

• hoofed feet

• Darwin

Notoungulata (Meridiungulata)

• Palaeocene

• South American; Mixotoxodon made it to Central America in Pleistocene

• broad, flat skull; strongly lophodont and full hypsodonty

• 4 groups (notioprogonians, toxodonts, typotheres and hegetotheres)

Astrapotheria (Meridiungulata)

• Palaeocene

• no upper incisors; upper canines large tusks; last two molars huge

• nostrils on top of skull

• very large; Astrapotherium

Xenarthra (armadillos, sloths, anteaters) Synapomorphies

• South America

• unique accessory articulations between vertebrae (hence name which means “ancient joint”)

• absence of enamel on teeth

Glyptodonta (Cingulata, Xenarthra, armadillos)

• trilobed, unrooted cheek teeth for grinding

• middle Eocene to Pleistocene

• largest Glyptotherium (Pleistocene) which was more than 3m long

• Argentina

Phyllophaga (Pilosa, Xenarthra)

• sloths

• modern sloths = arboreal; most of Cenozoic ones were ground sloths

• late Eocene; abundant in Miocene S. America, extinct ~5000 ybp

• Megatherium

Plio-Pleistocene Great American Biotic Interchange

• North and South America were disconnected until about 3 mya, when volcanic Isthmus of Panama formed

• Sparassodont marsupials disappeared for unclear reasons

• didelphimorphs invaded Central America

• many northern forms came south

• Flow of water cut-off

• Rodents replaced small marsupials

Animals going North during the Plio-Pleistocene Great American Biotic Interchange

xenarthrans: ground sloths, armadillos, glyptodont (Glyptotherium), giant anteater (Myremcophaga); notoungulates (Mixotoxodon); hystricomorph rodents (porcupine Erethizon into Canada); didelphid marsupials (as far as Canada)

Animals going south during the Plio-Pleistocene Great American Biotic Interchange

mustelids (skunk); Tayassuid peccary; Horse (Hippidion and others); Carnivora (dogs and cats); bears; gomphothere elephants; tapirs; camels; deer; shrews; several rodents

Animal in Pre-Pliocene South America

• carnivores = borhyaenid (marsupials)

• meridiungulates = dominant herbivores

• xenarthrans with specialist rolls (anteaters and leaf browsers)

• marsupial carnivores declining prior to Pliocene

• meridiungulates in decline (some survive till late Pleistocene)

Afrosoricida (Afrotheria)

• Chrysochlorida – golden mole

• Tenrecida – tenrecs and otter shrews

• very poor fossil record, restricted to Africa (Chrysochlorida) and Madagascar (tenrecs), Miocene; possible Fayum specimen (late Eocene)

• zalambodont molars

Macroscelidea (Afrotheria)

• elephant shrews

• only fossils are in Africa

• middle Eocene teeth of Chambius from Tunisia

• late Eocene Herodotius from Fayum

• four-cusped bunodont molars lacking lophs

Tubulidentata (Afrotheria)

• Oligocene Europe and Miocene Africa

• dentine prisms

• aardvark

• single living species (Orycteropus afer)

• Preserved with elephant birds

Sirenia

• early Eocene in Europe; world-wide by late Eocene

• bilophodont molars like proboscideans

Prorastomus (primitive Sirenia)

• skull only

• from Jamaica

• lack ventral deflection of rostrum found in others

Pezosiren (Sirenia)

• uncompressed neck unlike more derived forms

• probably capable of terrestrial locomotion

• tall anterior neural spines

• strong connection between ilium and sacral vertebrae

• relatively short limbs

• aquatic: dorsal nostrils, dense ribs

Order Desmostylia

• early Oligocene to the late Miocene

• exclusively northern Pacific Rim

• marine mammals; semi-aquatic, hippo-sized

• 6 genera from

• ate seaweed, and probably related to Sirenia

• Diastema

• Broad hands and feet

Palaeoparadoxia (Order Desmostylia)

• well-developed limbs

• paddle-like hands and feet

• incisors and canines well developed

• cheek teeth resemble those of proboscideans

order Embrithopoda

• primarily African but first appear in Europe

• jaws and teeth

• late Palaeocene to late Eocene

• most basal Paenungulata

• Arsinoitherium

Hyracoidea (Afrotheria)

• earliest = late Eocene/early Oligocene of Fayum

• dispersed into much of Asia

• browsers (teeth bunodont, lophodont,

  selenodont)

• Titanohyrax bigger than modern hyrax

• Megalohyrax – skull 40 cm long

Proboscidea (Afrotheria)

• earliest Eocene, Morocco

• true lophodont molars

• transverse crests uninterupted by conules

• bilophodonty (primitive proboscidean condition)

• Phosphatherium, Palaeomastodon

Moeritherium (Proboscidea, Afrotheria)

• enlarged second incisors

• bilophodont molars

• reduced tail

• short stout limbs semiaquatic

• maybe Sirenia or Desmostylia rather than Proboscidea?

African proboscidean radiation

• Dinotheres (late Oligocene Ethiopia) seem to have evolved directly from a Moeritherium-like ancestor

• deinotheres represent a distinct line evolution that probably diverged very early in the history of proboscideans

Deinotheres (Proboscidea, Afrotheria)

• first in late Oligocene, Ethiopia

• only 2 or 3 simple lophs on molars

• tusks

• Came into Asia through ‘Gomphothere Land Bridge’ in middle Miocene (Arabian Peninsula)

Palaeomastodon and Proboscidea evolution

believed to have given rise to subsequent radiation of proboscideans other than deinotheres

Mastodons (Mammutidae, Afrotheria)

• Miocene until start of Holocene

• name derives from Greek: nipple tooth

• e.g., Zygolophodon, one of largest terrestrial mammals ever

• Thomas Jefferson

Gomphotheriidae (Proboscidea)

• molars differ from elephants (but like mastodons) - bunodont

• earlier species with four tusks

• retracted facial and nasal bones - trunks

• widespread in North America during the Miocene and Pliocene (12–1.6 mya)

• lived in parts of Eurasia, Beringia, and with the Great American Interchange into South America

• starting about 5mya - replaced by elephants

Platybelodon grangeri (Gomphotheriidae, Proboscidea)

• tusks like incisors

• Scooped up water and plants

• Lived in wet areas

Stegadontidae (Elephantoidea)

• Miocene to Pleistocene

• distinct ridges on molars

• Beresovka Mammoth

Euarchontoglires

• arisen in Early Cretaceous

• Plesiadapiformes, Primates, Dermoptera (colugos = flying lemurs), and Scandentia (tree shrews)

Scandentia (Euarchontoglires, tree shrews)

• Eocene Eodendrogale, Asia

• 1-2 Miocene forms (plus extant genus Tupaia)

• Auditory bullae

• Complete zygomatic arch

• Dilambdodont

Dermoptera (Euarchontoglires, flying lemurs)

• two extant species: Cynocephalus volans = Philippine flying lemur (colugo); Galeopterus variegatus = Sunda flying lemur

• two extinct species Dermotherium major and D. chimaera from Eocene, Thailand are fully evolved dermopterans

• 2 pairs of lower incisors comb-like – cheek teeth with wrinkled enamel

• postcranial adapted for gliding membrane stretched between all four limbs

• Nearly completely postorbital bar

Boreoeutheria/Boreotheria

Euarchontoglires + Laurasiatheria

• sister groups probably split about 85 to 95 mya;

• early Palaeocene

• males share characteristic of external testicles (keep sperm cool); except in rhinos, hippos, cetaceans, etc.

Palaeontologists that discovered Purgatorius

• holotypes of two species with a single tooth (molars) each from Montana

• one species (Purgatorius ceratops) was from the Hell Creek Formation

• Leigh van Valen and Robert Sloan

Purgatorius

• the oldest and most primitive plesiadapiform

• long known only from isolated teeth and jaw fragments since it was first discovered 50 years ago

• Ankle bones diagnostic characteristics for mobility

Plesiadapiformes

• most primitive primates

• Cretaceous specimens from Alberta and Montana:

• Immediate post-Cretaceous origin for Primates followed by Palaeocene radiation

• Arboreal

• mobile shoulder and elbow joints

• mobile hip joint capable of a great range of abduction and lateral rotation

• lower ankle joint mobility for inversion of the foot

• terminal phalanges suggest “claw-clinging”

Primate characters lacking in Plesiadapiformes

• no postorbital bar

• no shortened snout

• supposedly no opposable hallux and pollex

Plesiadapis vs Carpolestes (Plesiadapiformes)

• Plesiadapis - short fingers, extremely long hook- like claws, lessened ability to grasp small-diameter supports

• Carpolestes - shorter claws, longer fingers and toes, relatively shorter metacarpals and metatarsals, foot with a divergent, opposable hallux with a nails, better adapted for grasping small diameter supports in a powerful and precise manner

Carpolestes simpsoni (Plesiadapiformes)

• almost complete specimen found in U. Paleocene, Wyoming

• has opposable first digits with nails

Ignacius dawsonae (Plesiadapiformes)

• Ellesmere Island

• Early Eocene

• Showed Arctic was warm and diverse

Order Primates

• found in wide diversity of habitats on all continents except Antarctica

• Auditory bulla derived from petrosal portion of the temporal bone

Adapiformes (Primates)

• thrived in Eocene; disappeared from most of Northern Hemisphere with cooling climate; gone by end Miocene (~7 mya)

• some are lemur-like

• may/may not be link between Strepsirrhini and Haplorrhini

• unspecialized bunodont dentition – frugivores

• Notharctus

‘Ida’ Darwinius masillae (Primates)

oldest and most complete primate fossil in the world. Even the stomach contents have been preserved

• Messel, Germany

‘prosimians’ (Primates, lemurs, galagos, lorises, tarsiers)

retain primitive features:

• small brain, long snout, postorbital bar not expanded to enclose back of orbit

• incisors rounded not spatulate

• mandibular symphysis unfused

• earliest Eocene, then radiate through northern continents

Strepsirrhini

lemurs (Madagascar), galagos (bushbabies, Africa), lorises (India and SE Asia and pottos of Africa), †Adapiformes (Eocene, N. America, Europe, Asia)

• wet nose/rhinarium

• vomeronasal organ

• bicornuate uterus with epitheliochorial placenta

• tapetum ludicum

• have bony eye ring but lack thin wall of bone behind

• produce vitamin C

• tooth comb (not in adapiforms)

• grooming claw on second toe (?adapiforms)

Lemuriformes & Lorisiformes (Strepsirrhini)

• very poor fossil record

• first lemuriform = Miocene East Africa; Pleistocene,

  Madagascar

• first lorisiform = mid Eocene, Fayum (teeth)

Omomyoidea (Haplorrhini, Primates)

• Eocene

• insectivorous,

• arboreal

• tarsier-like (large orbits, no PM1)

• Shosonius

Tarsiiformes (Haplorrhini)

• fossil = Europe, north Africa, Asia, North America

• extant = SE Asia, Tarsiidae

• may include Omomyidae

• Semi-bunodont

Simiiformes

• Haplorrhini excluding Tarsiiformes

• migration to South America via rafting or land bridge in Oligocene

Platyrrhini (Simiiformes, Haplorrhini)

• New World monkeys; five extant families

• only spider monkeys and relatives (Atelidae) have prehensile tails

• ‘flat nose’ and sideways nostrils compared to Old World monkeys and apes

• earliest fossils; 25 mya Branisella; 20 mya Chilecebus

Catarrhini (Simiiformes, Haplorrhini)

• Old World monkeys and apes

• Africa and Asia

• Aegyptopithec

• Cercopithecidae (monkeys) + Hominoidea (apes = Hylobatidae + Hominidae)

• arboreal to fully terrestrial

Aegyptopithecus (Catarrhini, Simiiformes, Haplorrhini)

• Catarrhini

• Jbel Qatrani Fm, Fayum, ~30 mya

Hylobatidae (Catarrhini, Simiiformes, Haplorrhini)

• small or lesser apes = Gibbons

• primary mode of locomotion = brachiation

• walk bipedally with arms raised for balance

• Yuanmoupithecus - Yunnan, China Miocene

Macroscelidea (Elephant Shrews)

• Africa, Eocene to present

• insectivorous

• saltorial

When did Rodents and lagomorphs diverge and radiate?

• diverged from other placentals by a few million years after K-Pg boundary

• radiated in Cenozoic

Standard rodent dentition

• only 2 gliriform lower incisors

• double layer of enamel on front surface of rodents (single in lagomorphs)

• fully molariform fourth premolars

• described by Hayden, Hatcher, Leidy, Osborn, Marsh

• White River Badlands

Rodentia radiation

majority of families appear in late Eocene (explosive radiation)

• took over niches from multituberculates that were lost by end-Cretaceous extinction

• Spread all over, crossing oceans from Africa to Madagascar and South America; only terrestrial placentals to reach Australia by themselves

Ischyromyids (Euarchontoglires)

• late Palaeocene of North America

• standard rodent dentition

• primitive jaw- closing musculature

• no specialization in rostrum for masseteric musculature

• basal rodents

• Two gliriform incisors (enamel on the front)

• Fully molariform fourth premolars

Paramys (Ischyromyid)

• Eocene

• sister to squirrels and mice rather than as a

  basal sciuromorph

• North America, Eurasia, Africa

• may have given rise to Sciuromorpha and Myomorpha

• Messel, Germany

Mixodonta (Euarchontoglires)

• early Palaeocene Asia

• Heomys

• single pair of gliriform incisors, postcanines similar to basal rodents

Groups in Rodentia

• Castorimorpha–beavers, pocket gophers, kangaroo rats, kangaroo mice

• Hystricomorpha–(includes caviomorphs) gundis, porcupines, pacas, pacaranas, agoutis, cane rats, capybaras, nutria, chinchillas

• Myomorpha–mice, rats, gerbils, hamsters, lemmings, voles

• Sciuromorpha–mountain beaver, squirrels, chipmunks, marmots, flying squirrels, dormice

Hystricomorpha (Rodentia) dispersal

Originate in Asia about 40 mya, invade Africa in late Eocene, then into South America (across ocean) by early Oligocene

Rodentia dispersals during the Great American Biotic Interchange

• New World porcupines head north

• sigmodontines (New World mice/rats) head south and explosively radiate in South America, preventing other rodents from doing the same

When did Rodentia arrive in Australia

arrive in Australia from Indonesia at the end of the early Pliocene about 5 mya

Rodentia zygomasseteric system

propalinal (fore-aft motion while teeth in occlusion) motion of jaw enabled by an extension of the zygomatic arch and the division of the masseter muscle into three distinct parts

Rodentia 3 masseter muscles

• superficial masseter

• lateral masseter

• medial masseter

• moving origin of muscles anteriorly - additional range of movement for lower jaw and stronger force

• main force for closing rodent jaw

Rodentia protrogomorphy zygomasseteric system

snout unmodified; masseter originates on ventral surface of zygomatic arch

• Only seen in aplodontiidae (mountain beaver) and some fossil groups

Rodentia sciuromorphy zygomasseteric system

ventral surface of zygoma (cheek) tilts and broadens into zygomatic plate; lateral masseter extends forwards onto snout, superficial masseter extends forwards along zygoma

• in Sciuromorpha

Trogontherium cuvieri von Waldheim (Rodentia)

• Europe, Siberia, China

• Pliocene, Pleistocene

What group are Casteroides ohioensis, Trogontherium cuvieri von Waldheim, Palaeocastor in?

Rodentia

• Palaeocastor - Miocene beaver

Hystricomorph rodents radiation

South American radiation originated with dispersal from west Africa during Oligocene

• includes capybaras

What group are Erethizon dorsatum (porcupine), Josephoartigasia monesi, Phoberomys and the Patagonian hare in?

Hystricomorph rodentia

• Phoberomys - Late Miocene Venezuela, hippo-sized

Rodentia Hystricomorpha zygomasseteric system

medial masseter enlarged, passes through enlarged infraorbital foramen; superficial masseter originates on front edge of zygoma; lateral masseter extends along zygoma

• Hystricomorpha, Anomaluromorpha, some Sciuromorpha (Gliridae, dormice)

• ateral masseter attaches to the back of the zygomatic arch

• origin of the superficial masseter is on anterior part of zygomatic arch

• angular process lies lateral to the vertical plane of the tooth row.