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erth 2401 > lec 12 > Flashcards

lec 12 Flashcards

1
Q

PACHYCEPHALOSAURIA –

A
  • Late Cretaceous of Asia & North America
  • Thickened skull roof
  • Short ‘frill’ (squamosal) over occiput (back of skull)
  • Osteoderms on squamosal
  • Obligate bipeds
  • Short arms & hands
  • Stenopelix, Early Cret. Germany ~ 2 m total length  Originally considered to be a basal pachycephalosaur; now considered to be a basal ceratopsian (sister taxon to Yinlong)
  • Dracorex (juvenile)  Stygimoloch (subadult)  Pachycephalosaursus (adult) – as the animal grows it reabsorbs horns on the skull into the body
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2
Q

Development of the Dome

A

 Growth series of Stegoceras validum in dorsal (top) and lateral (bottom) views
 Note transition from a flat-headed to domed frontoparietal morphology that occurred through ontogeny

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3
Q

YINLONG DOWNSI XU – earliest member of Ceratopsia – most basal member

A

 Early Late Jurassic, Shishugou Formation of Xinjiang, China
 Forelimb <40% hindlimb
 Rostral (1) Skull larger than most ornithischians but < other ceratopsians
 Thickened jugal, but no flange – no horn (2)
 Elevated post skull but no parietal contribution to frill (3)

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4
Q

PSITTACOSAURIDAE Osborn 1923

A

123-125 Ma (Barremian-Aptian boundary) – mid Albian (~ 112 Ma)
 Skulls short and tall.
 Adults bipedal; hatchlings probably quadrupedal
 Dentary teeth with bulbous primary ridge
 Tails have “quills” – modified scales of some sort
 Bonebed accumulations suggest social behaviour

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5
Q

NEOCERATOPSIA

A

 Defined by the presence of a well-developed frill
 Basal members biped
 Frill Size Increases throughout Ceratopsian Evolution

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6
Q

AQUILOPS = Early Cretaceous, Montana

A

 Oldest North American ceratopsian
 Aquilops is a basal neoceratopsian
 Shows connection between Asia and North America ~105 million years ago

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7
Q

LEPTOCERATOPSIDAE

A

 Unique horizontal shelf (notch) on teeth
 Vertical-notch tooth-wear pattern was produced by both vertical shearing and grinding
 More basal neoceratopsians exhibit an oblique wear pattern vs. more derived neoceratopsians with a vertical shear wear pattern
 1st non-ceratopsid neoceratopsian to be described
 Mid-caudal neural spine height 4x centrum height. (1)

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8
Q

KOREACERATOPS HWASEONGENSIS

A

 First dino to be found in Korea
 Outgroup to more derived neoceratopsians.
 Very tall neural spines over 5 times higher than the associated.
 centra in the distal caudals.
 Claws, not hoofs.
 Probably functionally bipedal

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9
Q

CORONOSAURIA = Protoceratopsidae + Ceratopsoidea

A

 Enlarged frill, enlarged skull, obligate quadrupedality

 Ceratopsians laid soft-shelled eggs and that’s why there are no found ceratopsian eggs

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10
Q

CERATOPSOIDEA = Ceratopsidae + closest sister taxa (e.g., Zuniceratops)

A

 Large body size (.5 to 2 tons)
 Postorbital brow horns are a synapomorphy
 Might have burrowed
 Double rooted teeth

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11
Q

ZUNICERATOPS CHRISTOPHERI – New Mexico

A

 Postorbital horncore mediolaterally compressed
 No nasal horn.
 Two replacement tooth rows with single-rooted teeth

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12
Q

CENTROSAURINAE

A

 Relatively short, deep snout
 Pair of long horns (P3) at back corners of the frill
 Short, rectangular squamosals

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13
Q

CHASMOSAURINAE

A

 Longer, shallower snouts
 Elongate rostral bones
 Long squamosals

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14
Q

CERATOPSIAN SOCIAL BEHAVIOUR

A

 Ceratopsid bonebeds are common in the Campanian of W NA, esp. for centrosaurines: Coronosaurus, Centrosaurus, & Pachyrhinosaurus
 Carcasses are disarticulated
 >100000 elements preserved from 100s or 1000s of centrosaurs
 All size classes preserved

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15
Q

EVOLUTIONARY PATTERNS IN MARGINOCEPHALIA

- FEEDING

A

 Pachycephalosaurs have relatively unspecialized snouts and teeth, and so were probably nipping browsers
 Basal ceratopsians increased their jaw power and evolved the cropping rostral bone (+ predentary = ‘beak’)
 The frill of basal ceratopsians greatly increased their jaw muscle power
 Shearing dental batteries in Ceratopsidae gave them one of the most powerful bites to evolve among amniotes

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16
Q

EVOLUTIONARY PATTERNS IN MARGINOCEPHALIA

-LOCOMOTION

A

 Pachycephalosaurs, basal ceratopsians, and basal neoceratopsians were bipedal
 Increased skull size forced advanced neoceratopsians onto all fours, such that Coronosaurs were obligate quadrupeds

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17
Q

EVOLUTIONARY PATTERNS IN MARGINOCEPHALIA

-SIZE TRENDS

A

 Most pachycephalosaurs, basal ceratopsians, and basal neoceratopsians were small (all in the 1-3 m range, smaller than humans)
 Increased size in pachycephalosaurs (e.g., Pachycephalosaursus) only occurs at the very end of the Late Cretaceous.
 For most of its history, Ceratopsia consisted of only small dinosaurs.
 Advanced neoceratopsians show a size increase earlier than pachycephalosaurs, culminating in the major size increases at the base of Ceratopsoidea

18
Q

PATTERNS IN MARGINOCEPHALIA

-SOCIAL BEHAVIOUR

A

 Both pachycephalosaurs and ceratopsians seem to have used their heads for within-species interactions.
 Ornamentation (marginal osteoderms, domes, frills, horns, etc.) and possible combat features (thickened skulls, horns) are present in both clades, and some of these only appear at fully adult sizes.
 Evidence for gregarious behaviour is present throughout Ceratopsia (e.g., Psittacosauridae, Leptoceratopsidae, Protoceratopsidae, Ceratopsidae)

19
Q

CERATOPSIAN PALEOBIOGEOGRAPHY

A
  1. Ceratopsia originated in Asia (Late Jurassic)
  2. Initial radiation of neoceratopsians in Asia (Early Cretaceous).
  3. Dispersal of basal neoceratopsians into Europe before Bering Land Bridge (late Early Cret.). – entry of Leptoceratopsid ancestor into NA via Europe.
  4. Radiation of basal neoceratopsian in NA via land bridge ~Turonian.
  5. Origin of ancestral ceratopsid equivocal (Turanoceratops in Asia, Zuniceratops in NA in Turonian).
  6. Radiation of ceratopsids in NA; possible Late Cret. return of Leptoceratopsids to Asia (Udanoceratops); possible return of ceratopsids to Asia.
20
Q

LEC 13 - ORNITHOPODA

A

ORNITHOPODA = Parasaurolophus and all taxa closer to it than to Triceratops
Ornithopoda (“bird feet”)
 Basal ornithopods have 4 toes supporting weight; Styracosterna have 3 functional toes
 Evolved in the Early Jurassic, survived until the end of the Cretaceous.
 Consist of basal ‘hypsilophodont-grade’ taxa (e.g., Thescelosauridae), and large clade of iguanodontians, including hadrosaurs
 Primitively ornithopods were small, agile bipeds. Iguanodontians were generally much larger, and quadrupedal.
 Hypsilophodon from the Early Cretaceous of England is an archetypical ‘basal’ ornithopod
 Most complex jaw vertebrate
 ‘Basal Ornithopoda’, often referred to as ‘hypsilophodonts’, are ornithopods less derived than Styracosterna
 Most are Early to Late Cret., so not basal temporally, but phylogenetically
 All are bipedal, but most not well-adapted to fast running
 Lack defensive mechanisms

21
Q

Feathers: Kulindadromeus zabaikalicus (2014)

A

 Middle to Late Jurassic (175 Ma), Siberia
 Oldest ornithischian with feathers.
 Combination of modified scales and feathers on body.
 Multiple specimens from bonebeds = sociality?

22
Q

Orodrominae

A

 Early to Late Cret. NA & Asia
 Oryctodromeus = 1st dino to show burrowing and denning behaviour
 Adult & 2 juveniles found in ~2x1 m den
 Bipedal with forelimb adapted for digging

23
Q

Hypsilophodontidae

A

 Early Cretaceous, Isle of Wight
 1st discovered 1849; named 1869
 ~2m long; ~ 20 kg; agile runner;
 Pointed snout with sharp beak for snipping plants

24
Q

Thescelosauridae

A

 Early to Late Cret. of North and South America, & Asia
 Cone-like teeth in premax; leaf-shaped teeth in dentary and maxilla
 Long snout, larger body size than more basal ornithopods.
 Most 2-4 m, but some up to 6 m
 5 fingers, 4 toes
 Watch Michael Hudgins talk for more details on basal ornithopods and Thescelosauridae

25
Q

IGUANODONTIA

A

 all ornithopods more closely related to Parasaurolophus than to Hypsilophodon or Thescelosaurus

26
Q

IGUANODONTIA vs. basal ornithopods

A

 Larger & heavier
 Enlarged naris
 Toothless premaxilla
 Diamond-shaped tooth crowns
 Increased sideways and backwards motion of the dentaries during chewing
 Well-developed pleurokinetic hinge in upper jaw, allowing lateral motion of the maxillae and other facial bones during chewing

27
Q

BASAL IGUANODONTIA

A

 Many were facultative bipeds
 Oldest iguanodontian is the Middle Jurassic (dryosaurid Callovosaurus) (most boring dinos)
 Iguanodontians common in the Late Jurassic & widespread in E Cret
 Most abundant large animals in most ecosystems, displacing sauropods & stegosaurs (L Jurassic-E Cret)
 Tenontosaurus is one of the most common dinosaurs in the E Cret (e.g., Cloverly & Antlers formations) of western NA.
 75% of all Tenontosaurus localities contain remains of the dromaeosaurid Deinonychus; size difference (8 vs. 3 m for adults) suggests pack hunting.

28
Q

Iguanodon

A

 Early Cretaceous, Europe
 Adults up to 10 m; ~3 tons
 Named in 1825 by Gideon Mantell; 2nd dino named
 38 skeletons from Belgium coal mine (1878) at 332 m
 15 individuals from a BB in Germany; sociality
 Forelimb ~ 75% hindlimb

29
Q

Iguantodontia: Ouranosaurus - Early Cret, Niger – Elrhaz Fm

A

 ~ 8 m in length; ~ 4 tons
 Premaxilla toothless; 1 row of replacement teeth; 1st & 2nd generation teeth form continuous bite surface
 Small crest in front of orbit – development of premaxilla crest on the front of the skull
 Small thumb spike
 Very large neural spines bound by ossified tendons over hips to support weight

30
Q

HADROSAURIDAE

A

 Dominant large herbivores in Late Cret ecosystems in North Am. Also, in Asia, EU, SA, Antarctica & Africa – 50% of the dinos were duck-billed
 Two major clades:
1. HADROSAURINAE (‘solid-crested’) – no crest – long thin ischium
2. LAMBEOSAURINE (hollow-crested) – large crest – has a boot ischium (looks like a hockey stick)
 Up to 15m in length; 2 m skulls
 Exclusively Late Cretaceous in age.
 Cranial crest formed by nasal bone
 Tall, symmetrical lancelet tooth
 Dental battery with 3 or more replacement teeth
 >32 rows of teeth in each jaw

31
Q

Hadrosaurids vs. basal Iguanodontia:

A

 Further expansion of the snout (“duck bill”)
 Further increase in # of tooth positions
 Grinding dental battery forms continuous grinding surface
 Teeth of greater structural complexity than all other vertebrates
 Loss of the thumb spike (hadrosaurids are thumbless)
 Elongation of metacarpals II-IV

32
Q

Hadrosauridae: Dental Histology

A

 Hadrosaurid teeth were individually complex.
 Research by Erickson et al. 2012 has shown that each tooth is comprised of at least 6 different dental tissues.
 This makes hadrosaurid teeth more complex than those of mammals, including horses.
 Combine this with continuous tooth development makes hadrosaurids the most sophisticated dental system in vertebrates.

 Hadrosaurs are the most abundant dinosaurs in the Late Cretaceous of NA
 Likely moved in large herds at least part of the year
 Efficient jaws maximized the energy available from plant resources

33
Q

Social Behaviour: Hadrosaur bonebeds

A

 Monodominant hadrosaur bonebeds are well known from NA & Asia, with dozens of Edmontosaurus BBs from the L Campanian & Maastrichtian of Canada and the US
 Some preserved >10000 disarticulated elements from all size classes, but large subadults & adult
 Material dominate
 These provide strong evidence for social and/or herding behaviours
 Many hadrosaur skeletons preserve skin impressions.
 Scale patterns in hadrosaurs are species specific

34
Q

EVOLUTIONARY PATTERNS IN ORNITHOPODA

- Feeding

A

 The modified jaw/tooth position and (and possible pleurokinetic hinge) allowed basal ornithopods to process food more efficiently than typical ornithischians
 Primitive ornithopods had relatively narrow snouts; selective feeders?
 Larger iguanodontians (with broader beaks and greater feeding height range) may have had a more general diet
 Increasing mandibular (and pleurokinetic hinge?) ability, broader bill, and development of the dental battery allowed Styracosterna (esp. hadrosaurids) to become the most efficient herbivores in amniote history.

35
Q

EVOLUTIONARY PATTERNS IN ORNITHOPODA

- Locomotion

A

 Basal ornithopods retained the dinosaurian obligate bipedal habit
 Iguanodontians became facultative bipeds, with at least some hand function becoming locomotory
 Even the largest ornithopods seem to have been at least partly bipedal

36
Q

EVOLUTIONARY PATTERNS IN ORNITHOPODA

- Size trends

A

 Basal ornithopods were small (comparable to basal members of other ornithischian groups).
 But at the base of Iguanodontia and the base of Styracosterna there are major size increases.
 Additionally, various different styracosternan lineages independently achieved very large (>12 m) size.

37
Q

EVOLUTIONARY PATTERNS IN ORNITHOPODA

Social behaviour

A

 Abundant evidence for socially related adaptations, including herding; visual (and possibly aural) displays; species recognition structures; possible sexual dimorphism.

38
Q

BASAL ORNITHOPODA –

Late Triassic

A 
	No basal ornithopods present 
	Originally tooth taxa
	Teeth belong to croc line archosaur
	Extremely rare
	Track sites are abundant 
	Identification is still up for debate
39
Q

BASAL ORNITHOPODA –

Jurassic

A

 Basal and derived ornithopods are much more abundant
 Nanosaurus
 Agilisaurus
 Hexinlusaurus
 Derived ornithopods are present (e.g. Camptosaurus, and Dryosaurus)

40
Q

BASAL ORNITHOPODA –

Cretaceous

A

 Basal and derived ornithopods are common and diverse.
 Although basal, they have many derived characters.
 Thescelosaurus
 Orodromeus
 Jeholosaurus
 Hypsilophodon

erth 2401 (3 decks)

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