Enter Saurischia! Saurischians: Two major clades: -Sauropodomorpha - - PowerPoint PPT Presentation

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Enter Saurischia! Saurischians: Two major clades: -Sauropodomorpha - - PowerPoint PPT Presentation

Mar 17, 2024 324 likes •1.12k views

Enter Saurischia! Saurischians: Two major clades: -Sauropodomorpha The Big -Theropoda The Bad The Ugly What characterizes Saurischian Dinosaurs? 1. Subnarial foramen 2. Extra articulation on dorsal vertebrae 3. Twisted thumb

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Enter Saurischia! Saurischians: Two major clades:

  • Sauropodomorpha

The Big

  • Theropoda

The Bad The Ugly

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What characterizes Saurischian Dinosaurs?

  • 1. Subnarial foramen
  • 2. Extra articulation on dorsal vertebrae
  • 3. Twisted thumb

Ancestral characteristics:

  • ’Lizard Hip’ three-pronged pelvis structure

Tyrannosaurus

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Basal, non-sauropoda Saurischians

Small Bipedal Fast-moving (how can you tell?) Carnivorous Possibly a very early sauropodomorpha: Saturnalia Herrerasaurus Eoraptor

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Sauropodomorpha

  • 1. Prosauropoda
  • 2. Sauropoda

Massospondylus Diplodocus

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Sauropodomorpha Shared, derived characteristics Relatively small skull Long neck (10 vertebrae or more!) Deflected front end of lower jaw Elongate, peg-like teeth Added dorsal vertebrae in front of and behind the sacrum Enormous thumb Elongate femur (upper leg bone)

Plateosaurus (prosauropod)

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Prosauropoda

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Squares = prosauropod fossil localities Prosauropods Late Triassic to Early Jurassic

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Plateosaurus

Prosauropoda Shared, derived characteristics

Plateosaurus (prosauropod) Whopping big claw on thumb Reduced pinky toe Front limbs shorter than hind limbs

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Anchisaurus Coloradisaurus Lufengosaurus Yunnanosaurus Anchisaurus Coloradisaurus Lufengosaurus Yunnanosaurus Not meant for chewing Jaw joint below tooth row Leaf-shaped teeth (few grinding marks) NOT CHEWERS Predominantly herbivorous, but some basal forms may have been

  • mnivorous

Skull:

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Gastroliths a-plenty Likely utilized stomach fermentation Stomach-contents finds and morphology suggest gymnosperms were likely important The increase in diversity of prosauropods parallels gymnosperm diversity! Gastroliths, in situ

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Derived Prosauropoda

Riojasaurus Fully quadrupedal Quadrupedal / Facultative bipedal Plateosaurus

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Mussaurus (late Triassic)

Adults probably 10 ft long

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Sauropoda

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Cetiosaurus- first sauropod discovered Had spongy bone (similar to whales), hence it’s name Thought to be strictly aquatic & related to crocodiles Later, finds of the leg bone suggested an upright stance, rather than a crocodilian sprawling posture

Edward Drinker Cope

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Prosauropods Sauropods

Sauropod Skulls Shortened head Rounded snout Lower temporal fenestra below orbit No inset cheek teeth

  • not chewers

Delicate- not built to withstand large forces Evolutionary trend: nares gradually move to the top of the skulls

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Triangulate, spatulate, or pencil-like teeth In some clades, teeth are limited

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Nigersaurus

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Pleurocoels (particularly in neck) 12+ cervical vertebrae

Sauropoda-Neosauropoda

Massive, solid limb bones Long tail 5 fingers, 5 toes

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Uni-Directional Breathing

Air flows in one direction Pumped by auxiliary air sacs More O2 can be extracted Auxiliary airsacs partly housed in cavities within bones (sinuses) ~ pneumatic foramen Sauropods have these cavities in their backbones... dual purpose

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Uni-Directional Breathing

compared to bi-directional breathing (Mammals, lizards, snakes, crocodiles)

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https://www.youtube.com/watch?v=rfh-64s5va4

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Basal Sauropods

Shunosaurus Middle Jurassic Vulcanodon Early Jurassic Omeisaurus Late Jurassic 6.5 m (20 ft) long 10 m (32 ft) long Club Tail 15.2 m (50 ft) long 4 m (12 ft) high

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Omeisaurus in Hong Kong; 17 cervical vertebrae

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Omeisaurus Late Jurassic Mamenchisaurus Late Jurassic

19 elongate vertebrae

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Camarasauromorpha

Sauropoda/Neosauropoda

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Camarasauromorpha

Large Nares Relatively Short Neck Relatively long forelimbs

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U-shaped neck vertebrae To house strong, thick neck ligaments!

Camarasauromorpha

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Shorter snout Enlarged external nares

Camarasauromorpha

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Camarasauromorpha

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  • aof

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Camarasaurus

18 m (60 ft) long

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Brachiosaurids

13 elongate vertebrae Distinct snout Vaulted skull Very long forelimbs Neck held vertically 16 m (52 feet) tall Brachiosaurus

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Brachiosaurids

Brachiosaurus

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Brachiosaurids Sauroposeidon

Late Jurassic Neck: 37-40 ft long Vertebrae EXTREMELY ELONGATED Honeycombed with tiny air cells Bones very thin Longest sauropod neck vertebrae on record Likely able to raise it’s head 6 stories high

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Brachiosaurids: an interesting physical problem...

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Titanosaurids

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Robust lower forelimbs Titanosaurids: primarily in the Cretaceous

Alamosaurus

~9-10 m (30 ft) long Osteoderms! Very small heads

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Nemegtosaurus Pencil-like teeth; similar to Diplodocids Probably convergent evolution (the rest of body is very different)

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Titanosaurids: Saltasaurus

Saltasaurus egg Nesting ground; implies herding One of the only lines of evidence for sauropod reproduction

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Titanosaurids: Argentinosaurus Mid-Cretaceous 21-35 m (72-85 ft) long

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Titanosaur Brachiosaur

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27 m = 90 ft; Blue whale length

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Maximum stress centered over haunches

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Long sub-rectangular skulls Fully retracted Nares (on roof of skull)

Diplodocids

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Diplodocids: Apatosaurus

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Diplodocids: Barosaurus Late Jurassic 26 m (86 ft) long Compared to Diplodocus, longer neck and shorter tail

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Diplodocids: Supersaurus Late Jurassic 25-30 m (80-100 ft) long

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Diplodocids: Diplodocus Late Jurassic 54 m (177 ft) long Compared to Diplodocus, longer neck and shorter tail

Double-beamed chevrons

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Amphicoelias The largest known sauropod; almost 2x the length of a blue whale WHY SO BIG? ... a complex question. Ecology & Physiology Sauropods attained large body size in the latest Triassic / early Jurassic... i.e. quickly Very large body size is found among Diplodocids, Titanosaurs, Brachiosaurids Benefits include Obtain food that is out of reach for other animals Greater ability to digest low-nutrient foods Higher metabolic efficiency Escape from predation Cope’s Rule: Animals tend to increase in body size over evolutionary time

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Cope’s Rule and the evolution of large body size Advantages of large body size? Disadvantages?

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Diplodocid Titanosaur

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Diplodocid Tails: strange chevrons... Recall...

Diplodocus chevrons...

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Tail variations involve and increase in tail vertebrae from 44 - 80 (Apatosaurus & Diplodocus) Why?

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Accessories

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Classical rendering Hypothesized trunk Modern depiction w/ resonating chamber

Accessories

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Accessories

Vertebral spines: Amargasaurus (Diplodocid)

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Accessories

Keratinous spines?

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Sauropod Lifestyles

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“The start of the sauropod hiatus is interpreted as the result of a genuine continent-wide extinction, coincident with the appearance

  • f (and perhaps attributable to competition with) advanced
  • rnithischian herbivores, decrease in habitat due to the incursion
  • f the Western Interior Seaway, or both.”
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Apatosaurus

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Herding?

Shunosaurus Diplodocus Camarasaurus

Ecosystem Engineers

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Tsavo 1898

1st man-eater 2nd man-eater FMNH 23970 FMNH 23969

  • elephants

+ woodlands + droughts Rinderpest

  • grazers

hungry lions = novel prey?

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Along the Tsavo Railroad: From Slave Trade to Ivory

Tsavo: 1970 Less Elephant poaching Tsavo: 1994 More Elephant poaching

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Tsavo, 1898

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