Functional morphology of the hominoid shoulder, past and present
Date
2016-07-18
Authors
Berger, Lee Rogers
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Abstract
This thesis presents an :investigation into the
functional morphology and form of the skeletal
elements of" the shoulder girdle of extant h0111inoids
and extinct hO)ll.inids\~hich inhabited the Afr:i.c~n
continent during the Late pliocene and Elarly \Ii Ii \Ii,
ill Partic'l.l.lcu: emphasis is placed o\~\the \' i\.
form of the scapula, clavicle and humerus. \Ii
variation in the bony, arthrological and 41.yoloQif\;Lcal
I" anatomy' Of this region in extant hominoids is I
Pleistocene.
examined. In light of biomechaniq~l models
II
reSUlting from this work, the bony,;anatomy of u
hominid shoulder girdle elements examined and
i.
.1
r;:I~t>. ssil .1,1 .
"
biomechanical interpretations are made.
The fossil shoulder girdle elements exan\ine~ in
this study are grouped into four species samples.
The first sample (Australopithecus a.:friCaIlUS)
comprises Pliocene ,fossils from sterkfontein, South
Africa. 'rhe second sampJ.e (A. afarelJ.si.s) i.s
comprised of fossilo front Hadar, Ethiopia. The
third (Homo habilis) and, fourth (ii. boisei) samples
comprise fossils from C'lduvai GorgeI Ta:nzania,
Koobi For~ll, Ke!nya and t.ne omo Valley ~ Ethiopia.
When the t!;ossil homi.ndd. remains are scrt.ed into
specf.ea, jl~heI:;houlder g;l.rdle elements InelYd:>e used to
const.zuct; and contrast specd.es specijSiq '1· . )
bitOmechar1,ic::aml odelS of th~ shoulder. Th~~se
models e:>fltP10re differernoes in form amon~,r.;tj;ossil
hominid. species that may'be reJ,ated to dii.:;eetenc;:.es
in behaviour. The models may also be appU.ed to the :~......,..~
interpretation of systemat.ic relationShips amongst
early hominids.
In o:(.~ierto construct models of early homi:p,ids
it is first necessary to establish the,movement,
myology and oste0logy of the extant hominoid
shoulder. Chapters 4,5 and 6 sUl'l.1Il1ar~n,$eew data and
available in,formation concel:"ning shoulder girdle
mo.Jementand form. Chapter 7 presents detailed
C';escriptiQns Of the fossil hominid ma.terial (u:::::19)
available for study. 'rhis descriptive information,
in conibination with all of the information derived
from Chapters 4 through 6, is then used to
inte1.pret, compaxe and contrast the fu.nctional
morphology Of the shoulder girdle elements of each
species of early hotninid. pa:q:ticuJ.ar emphasis is
placed .on those features that cart be. directly
related to specific :functiOl'l~ Model.s ,,.l the
functional morphology of each of t1Je four species
are then created. comparisons are made between
indJ.vidual Shoulder girdle elements 'cg,fthe different
homj.nid spacd.es as well as between the interpreted
total morphology of each species' shoulder girdle.
The study concludes that the functional
m~>l':phologyof the shoulder girdle Qf A. afriaanus is
unique ~unorJ.gstknown hominoic1~mode'l.s in that it
poasesaes shoul<;ier girdle mo;t,'ph.oo.)gy adapted to bobh
suspen ory behaviour and bipE~d;;d~i.srn. TIte
suspensory adaptations are :Lndi9ated by the overall
ape ..like morphology of the humeri, claviculae and
heCid.of the scapulae, whilst bipedalism is mainly
(J
G indicated. by a broad, human-like inf.Ell:'ior'an9,'].eof "
=
the scapula. Several' RpparentlY prim.itive featu:r:es"
are present in,..the A. africanus Ejcapl,1la,incl~dirtg a
0i,? ..... . _ .. '. \
shortened scapular 'n~ck, that ind:l.Cate'-\poss~ple
ancestry f.roma quadru:pedal form. ~p.e functi<:>tJ.al.
morphology of the A. afarens.ts shoulder is founa .to
be more diffi.cult to interpret d'.le to poor f(i:;
,pre.~ervationt but the hypothesised znodel'~does not
diffe):: substantially from th~t constructed for A.
_c,~) . ..' .', 1) (;
a£ricanus. The few robust aURtra.lopithecine,.,(A.
boi.se:1) sho~~der girdle elements appear to possess ~,..
similar morpJ;lologi.esto A. a.:falyrnsis and )1-
africanus. There ara .no'l:.SUfi:'lc:tently well
preServedoH. habili.s shoulder girdle elements
preserved to 'makemeffilningfulinterpreta.tions about
the functional morphology of this, specie~:'
.' n the lack of comparable elements amongst the two (I
1arger samples (...21.. a:faJ;'ensi.s and ,fl. arr:J;canus) I .it
'..':::/
is not knownwhether the features found to be
apparently unique to either species are useful as
n taxonomic indicators.
Description
A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg 1994.