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A comparative essay on the anatomy and function between a Human hand
and an Iguanodon hand
Human hands are exquisitely adapted for their elegant and prehensile use
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Looking at
the hands anatomical differences between species it is clear to see the
distinctions in their functional uses
...

Iguanodons were 30ft long herbivores that lived in the early Cretaceous
period roughly 135-125 million years ago
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Just like human hands there are five digits; however there are extreme
differences in their anatomy, which is directly related to their use
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This shift
allowed them to live in many environments and being able to stand on two
legs allowed them to reach higher planation that other quadrupeds could not
reach, giving them a competitive advantage
...

Humans and Iguanodons both have 14 phalangeal bones, however the
phalangeal formula of human fingers is 2-3-3-3-3 compared to the
Iguanodons’ 2-3-3-2-4 formula
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This specialised geometric design, common throughout nature,
produces the arcs of joint motion, a trait not seen in the Iguanodon
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Humans have the most complex carpal system of any species with eight,
separate bone structures arranged into two transverse rows
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The Iguanodon, as is the case of many extinct
animals, had single/few bones with intercalated segments
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The ratio of the
metacarpus to carpus in the Iguanodon is lower than in a human, because
humans require this for the action of gripping objects4
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It is hypothesised that
the Iguanodon used this finger to wrap around tall vegetation to pull it down
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Furthermore, in junction with many other large extinct animals, the articulation
of the broad part of the Iguanodon’s radius with the carpal bones is great
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This
is however not essential in humans, whose wrists bear considerably less
1

weight and only intermittently
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The size of the pisiform directly relates to function of the hand by
affecting the moment of the flexor carpi ulnaris tendon
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In larger
quadrupedal animals like the Iguanodon, the pisiform is very long and
prominent, almost acting as the ‘heel’ of the hand
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The largest and most obvious difference lies in the thumb
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The thumb of the Iguanodon was wildly different with an
odd specialisation
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The spike was between two and six inches long and its functional use
is yet to be proven and highly debated among palaeontologists
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g
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There have been many theories of its use, including: a self-defence
mechanism, a method of breaking open food and also a collector of food via
stripping foliage from trees7
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Finally, the middle three fingers of Iguanodons are largely different to human’s
middle fingers
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This compact part of
the Iguanodons hand allowed little flexion and was the main weight bearing
area that is crucial for quadrupedal animals8
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At a glance, the digits are all clearly different and on
closer inspection there are large variations in the anatomy of the carpal
region
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[Word count = 940]

References

2

1

Sarjeant WS, Delair JB and Lockley MG
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Ichnos: An International Journal for Plant and
Animal Traces
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2

Tang JB
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J Hand Surg Eur
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3

Rotmann MB and Donovan JP
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Hand
Clinics
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4

Durand S, Marin F, Oberlin C and Ho MC
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Clinical Anat
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5

Moojen TM, Snel JG, Ritt JGS, Venema HW, Kauer JMG, Bos KE
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J
Hand Surg Eur
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6

Ferris BD, Stanton J and Zamora J
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J Bone Joint Surg
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7

Weishampel DB, Dodson P and Osmolska H
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Uni of
California Press
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8

Norman DB
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Institut Royal des Sciences
Naturelles de Belgique, Mémoire 1980;178: 1–104

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