Why giraffes havesuch short necks

Michael P. TaylorMathew J. Wedel

Why giraffes havesuch short necks

… and howsauropodsgot it right

Michael P. TaylorMathew J. Wedel

3-meter barrier for all non-aquatic animals

Long-necked sauropod groupsUpchurch et al. (2004:fig. 13.18)

Long-necked sauropod groupsUpchurch et al. (2004:fig. 13.18)

Long-necked sauropod groups

I suck ...

Upchurch et al. (2004:fig. 13.18)

Long-necked sauropod groups

Magic

I suck ...

Upchurch et al. (2004:fig. 13.18)

Factors contributing to long necks1. No constraint on vertebral count

Paraceratherium (Osborn 1923:fig 1)

Factors contributing to long necks1. No constraint on vertebral count

Mamenchisaurus (modified from Ouyang and Ye 2003:fig. 13)

Paraceratherium (Osborn 1923:fig 1)

Factors contributing to long necks2. Heads that did not process food

Factors contributing to long necks2. Heads that did not process food

Diplodocus

Factors contributing to long necks3. Heads that did not process food

Unholy Diplodocus ☓ Elephas hybrid

Factors contributing to long necks3. Absolutely large bodies

Factors contributing to long necks3. Absolutely large bodies

C

Factors contributing to long necks3. Absolutely large bodies

Crap.

Crap.C

Factors contributing to long necks3A. Large quadrupedal bodies

Crap.C

Factors contributing to long necks3A. Large quadrupedal bodies

C

Factors contributing to long necks3A. Large quadrupedal bodies

Crap.

Factors contributing to long necks3. Absolutely large bodies

Parrish (2006) showed that sauropod neck lengthscales with torso length to the power 1.35

Factors contributing to long necks3. Absolutely large bodies

Carpenter (2006) scaled Amphicoelias fragillimus as 2.2 times Diplodocus.But Parrish suggests neck is 2.2^1.35 = 2.9 times => a neck 22 m long

Factors contributing to long necks4. Air-sacs overcame dead-space

Factors contributing to long necks4. Air-sacs overcame dead-space

Like ostriches?

Factors contributing to long necks4. Air-sacs overcame dead-space

But what aboutsperm whales?

Paul 1998:fig. 11

Factors contributing to long necks4. Air-sacs overcame dead-space

But what aboutsperm whales?

Paul 1998:fig. 11

Factors contributing to long necks5. Vertebral architecture

Diplodocus carnegii holotype CM 84, cervical 10 (Hatcher 1901:plate III)

Cervical vertebral innovations

1. Extreme pneumaticity2. Bifid neural spines3. Elongate cervical ribs

Cervical vertebral innovations1. Extreme pneumaticity

Ostrich

Cervical vertebral innovations1. Extreme pneumaticity

Diplodocus

Cervical vertebral innovations1. Extreme pneumaticity

Diplodocus modified from Paul 1998:fig. 1(a)F

Cervical vertebral innovations1. Extreme pneumaticity

Diplodocus cervical cross-sections

Paul 1997:fig. 4 Schwarz et al. 2007:fig. 7A2

Cervical vertebral innovations1. Extreme pneumaticity

Diplodocus

Cervical vertebral innovations1. Extreme pneumaticity

Diplodocus

Cervical vertebral innovations1. Extreme pneumaticity

Diplodocus

Cervical vertebral innovations1. Extreme pneumaticity

Redtailedhawk

Cervical vertebral innovations2. Bifid neural spines

Apatosaurus

Long-necked sauropod groupsUpchurch et al. (2004:fig. 13.18)

Long-necked sauropod groupsBifid neural spines evolvedat least five times

Never secondarily lost?

Otherwise found only inthe rhea (and only just)

Upchurch et al. (2004:fig. 13.18)

Cervical vertebral innovations2. Bifid neural spines

Alexander (1985) thoughtthe trough was filled witha giant elastin ligament

Diplodocus

Cervical vertebral innovations2. Bifid neural spines

Apatosaurus

Cervical vertebral innovations2. Bifid neural spines

Apatosaurus

Cervical vertebral innovations2. Bifid neural spines

Apatosaurus

Cervical vertebral innovations2. Bifid neural spines

Diplodocus (Schwarz et al. 2007:fig. 7A2)

Cervical vertebral innovations2. Bifid neural spines

Cervical vertebral innovations2. Bifid neural spines

Cervical vertebral innovations2. Bifid neural spines

Cervical vertebral innovations3. Elongate cervical ribs

Turkeycervical 7

Cervical vertebral innovations3. Elongate cervical ribs

Turkeycervical 7

Cervical vertebral innovations3. Elongate cervical ribs

4.1 m

Turkeycervical 7 Mamenchisaurus

Cervical vertebral innovations3. Elongate cervical ribs

4.1 m

Mamenchisaurus

That lamegiraffe

Turkeycervical 7

Cervical vertebral innovations3. Elongate cervical ribs

Giraffatitan

Cervical vertebral innovations3. Elongate cervical ribs

Giraffatitan

Cervical vertebral innovations3. Elongate cervical ribs

Giraffatitan

Comparison with birds and crocs

Turkey cervical 7

Comparison with birds and crocs

Turkey cervical 7

Comparison with birds and crocs

Turkey cervical 7

Comparison with birds and crocs

Turkey cervical 7

Comparison with birds and crocsAlligator Majungasaurus Turkey

Majungasaurus from O'Connor 2007:figs. 8, 20

Comparison with birds and crocsAlligator Majungasaurus Turkey

Majungasaurus from O'Connor 2007:figs. 8, 20

Comparison with birds and crocsAlligator Majungasaurus Turkey

Majungasaurus from O'Connor 2007:figs. 8, 20

Comparison with birds and crocsAlligator Majungasaurus TurkeyGiraffatitan

Giraffatitan from Janensch 1950:fig. 46

Majungasaurus from O'Connor 2007:figs. 8, 20

Comparison with birds and crocsAlligator Majungasaurus TurkeyGiraffatitan Camarasaurus

Giraffatitan from Janensch 1950:fig. 46Camarasaurus from Osborn and Mook 1921:plate LXVIIMajungasaurus from O'Connor 2007:figs. 8, 20

Comparison with birds and crocs

Analogous but not homologous

Alligator Majungasaurus TurkeyGiraffatitan Camarasaurus

Giraffatitan from Janensch 1950:fig. 46Camarasaurus from Osborn and Mook 1921:plate LXVIIMajungasaurus from O'Connor 2007:figs. 8, 20

Why are epipophyses not elongate?

Euhelopus (Wiman 1929:plate III)

Why are epipophyses not elongate?

Euhelopus (Wiman 1929:plate III)

Why are epipophyses not elongate?

Euhelopus (Wiman 1929:plate III)

Why are epipophyses not elongate?

Euhelopus (Wiman 1929:plate III)

Why are epipophyses not elongate?

Deinonychus (Ostrom 1969:fig. 37)

Why are epipophyses not elongate?

Giraffatitan (Janensch 1950:fig. 43)

Why are epipophyses not elongate?

Need finer control for precise movements – requires shorter levers

Giraffatitan (Janensch 1950:fig. 43)

Why are epipophyses not elongate?

Tendon is stronger in tension than bone

Giraffatitan (Janensch 1950:fig. 43)

Why are epipophyses not elongate?

Muscles expand when they contract lengthways

Giraffatitan (Janensch 1950:fig. 43)

Why are epipophyses not elongate?

Muscles expand when they contract lengthways

Giraffatitan (Janensch 1950:fig. 43)

Why are epipophyses not elongate?

Why are epipophyses not elongate?

Crap.

Conclusion

TaxonManyvertebrae

No dental battery

Large body, four legs

Air-sacs Pneumatic vertebrae

Elongate cervical ribs

Giraffe Birds ✓ ✓ ✓ ✓Non-avian Theropods ✓ ✓ ✓Pterosaurs ✓ ✓ ✓Sauropods ✓ ✓ ✓ ✓ ✓ ✓

Conclusion

TaxonManyvertebrae

No dental battery

Large body, four legs

Air-sacs Pneumatic vertebrae

Elongate cervical ribs

Giraffe X X X X X XBirds ✓ ✓ ✓ ✓Non-avian Theropods ✓ ✓ ✓Pterosaurs ✓ ✓ ✓Sauropods ✓ ✓ ✓ ✓ ✓ ✓

Acknowledgements

Everyone who allowed us access to specimensEveryone that we stole images fromWestern University for sending Matt to SVPCA

Sauroposeidon