Dinosaurian palaeobiology: a New Zealand perspective

7 Pages·1996·2.2 MB·

by  J Wiffen

DINOSAURIAN PALAEOBIOLOGY: A NEWZEALAND PERSPECTIVE
J.WIFFEN
Wiffen,J. 1996 1220: Dinosaurianpalaeobiology: aNewZealandperspective.Memoirsof
theQueenslandMuseum 39(3): 725-731. Brisbane. ISSN0079-8835.
ThefirstknowndinosaurbonefromNew Zealand wasidentified from theLateCretaceous
marine sandstones at the Mangahouanga Stream site in 1980 (Molnar, 1981). Since then
isolated bones indicate that a variety ofherbivores and carnivores were present after the
separationfromGondwana80-85millionyearsagountiltheirextinction.Thoughgeographi-
cally polarinorigin, survival fora long periodon an island landmass suggests a temperate
Q
climate prevailed as New Zealand drifted north. New Zealand, Cretaceous, dinosaur,
palaeoclimate,paleobotany, taphonomy.
J. Wiffen, 138BeachRoad, Haumoana, Hawke'sBay, NewZealand, 5July 1996.
The only dinosaur fossils so far found in New dry summers), with resulting surfaces worn by
Zealand come from the Late Cretaceous running water.
Maastrichtian-Campanian marine sediments in
the Mangahouanga Stream fossil site, North Is- SIGNIFICANCE
land, New Zealand. These bones represent a
By and large the record of terrestrial life from
tdeirvreersstreiadlilniofesafurromfMauensaozaonidcNtheewoZnelaylarnedc.orTdheoyf ealnscieewnhterNe.ewAcZiedalcoanndditisino'ntsapsrgoodoudceadsbtyhotsheefhriogmh
includevertebraeandphalanges from2-3 species
rainfall and extensive forestcover are thoughtto
oftheropod, vertebrae(Fig. 1A)andaribfroman account for the generally poor fossil record
ankylosaur, an ilium (Fig. IB) from an or- (Fleming, 1962).
nithopod and a rib fragment (Fig. 1C) from a Consequently althoughthe numberofdinosaur
&
sauropod(Molnar, 1981;Wiffen Molnar, 1989; bones identified to date is small, they are sig-
Molnar & Wiffen, 1994). nificant for several reasons:
Thebonesarefoundinhardcalcareousconcre- 1)They show thatdinosaursinhabitedthis part
tions, locallyderived fromtheupperlayersofthe of Gondwana prior to its separation from the
Maungataniwha Sandstone. This was laid down Marie Byrd Land area of western Antarctica
on the eastern coastline of ancient New Zealand (Stevens, 1985).
in Campanian-Maastrichtian (Haumurian- 2) They are the first evidence that terrestrial
Piripauan) times and is now exposedat theMan- vertebrates survived in New Zealand after its
gahouanga Stream (Fig. 2). Isolated bones were separation from Gondwana,asopposedtohaving
carried from the adjacent l—andmass by rivers arrived there by dispersal.
probably in seasonal floods the larger bones 3)Thisistheonlyknown SouthernHemisphere
dropped as the f—low slowed through lagoonal or region where dinosaurs lived on a small island,
estuarine areas prior to burial in riverborne for up to 15-20 million years, until their extinc-
debris in nearshore wave base deposits tion.
(Crampton & Moore, 1990; Moore & Joass, Whatevolutionary changes, ifany, occurred in
1991; Wilson & Moore, 1988). Theyoccuralong tvhiersoenmfeonrtm,sininthteheabpsreenscuemaobflmyigsrtaattiiconissltaondNeenw-
with fossils ofmarine origin. Zealand and with (presumably) decreased com-
Thedescribedterrestrialbonesareeasilyrecog- petition, are not known. To date no unique fea-
nised(Fig. 3)andwellpreserved, withdiagnostic tures have been seen to suggest morphological
features. Soitseemslikelythatthebonesweren't changes or geographic or climatic adaptations:
transported far from land to the site. When ex- however, considerably more complete fossil
tracted from the rock, there is little apparent material is required to determine this.
abrasive damage on the bone surface that oc- Although similar taxa have been found from
curredpriortoburial. Mostofthedamage seen is this period in Antarctica (Hooker et al., 1991;
recent, from exposure afterthe concretions have Hammer & Hickerson, 1994) no closely-related
eroded out ofthe enclosing rock and split due to forms h—ave been detected, in spite ofthe variety
temperature extremes (i.e., winter frosts and hot oftaxa ornithopod, sauropod and ankylosaur,
726 MEMOIRS OFTHEQUEENSLAND MUSEUM
thisvolume)andasecondskull
of the large ornithopod Mut-
taburrasaurus (Molnar, this
volume) from Queensland and
a range of new Jurassic
material from Antarctica
(Hammer & Hickerson, 1994)
suggest the early and
widespread distribution of
dinosaurs on the southern con-
tinent. So a greater under-
standing ofthedistributions of
thesepolardinosaurs,andtheir
relationships to those from
New Zealand, should result
when more becomes known
aboutthese new discoveries.
Thedifficultiesofclosecom-
parisons with New Zealand
dinosaur bones are due to the
paucity of fossil material col-
lected and identified to date,
hence the difficulty in finding
homologouselementsforcom-
parison, as well as the dis-
crepancy in geological age
from most other Australasian
/Antarctic sites.
FLORAANDFAUNA
The New Zealand marine
fossilrecordis relativelygood,
andtheMangahouangaStream
site has contributed fossils to
9 both marine (Crampton &
Moore, 1990; Glaessner, 1980;
Feldmann, 1993; Wiffen—,
1981)andterrestrialrecords
including (possibly fresh-
FIG. 1. A, Articulated nodosaurian caudal vertebrae (CD 546) from the water\ turtles (Gaffnev oers
MaungataniwhaSandstone,MangahouangaStream,inposterolateralobli- cornm iQflQi flvinp rentTles
cqaumeevriae.w.CDT,heNsepweciZmeeanlaunndfoGretoulnoagtielcyalexScuerevdeeydCtohleldecetpitohn,ofLfoowceusroHfuttth.e \(V,^- \ 4A\nr\Wk*/'ifrfen &s \M/oilnlar&,
Scale= lcm.B,Posteriorpartoftherightilium(CD529)ofadryosaur-like 198**)> a coleopteran (Craw
ornithopod from the Maungataniwha Sandstone, Mangahouanga Stream. Watt, 1987) and a cockroach,
Scale = 1cm. C, Fragment of sauropod rib (CD 542) from the Maun- whichisstillunderstudy(Fig.5).
gataniwhaSandstone,MangahouangaStream. Scale=5cm. A considerable quantity of
— fossil wood and plant material
probablynodosaurian,dinosaurs thathavebeen has been collected as well and this is currently
&identified from the Mangahouanga site (Molnar beingdescribedbyJ.LRaine.Theavailablefossil
Wiffen, 1994): the ankylosaurid bones found
by the British Museum are as yet undescribed. plant material (wood, leaves, seeds and cone
Recent discoveries, which include a neoceratop- scales) is probably biased due toits prese—rvation
sian, Timimus hermani and a possible ovirap- in shallow wave-base marine sediments with
torosaur(Rich & Rich, 1994; Currieetal., 1996) only the tougher plant material surviving
fromVictoria, new ankylosaurmaterial (Molnar, transportationbyrivertotheregionofdeposition.
DINOSAURIANPALAEOBIOLOGY: ANEWZEALAND PERSPECTIVE 727
bivorous dinosaur population, which in turn
provided the food forthe carnivorous dinosaurs.
However, palaeobotanical evidence appears to
be accumulating to support the view of a cold
Australasian polar climate, i.e., dominant an-
giosperms that were deciduous, dormant in
periods of cold and darkness and dropping all
theirleaves overa shortperiod to formleafmats
&
(Vickers-Rich Rich, 1993; Johnson, 1993),
thoughPole(1993)suggeststhatthisisstillbased
on scant evidence. If true, presumably the
deciduous plants would have, to some extent,
replaced the conifers. From a practical point of
FIG.2.TheMangahouangaStreamfossilsite,showing view, suchadeciduous vegetation wouldseemto
a concretion eroding from the Maunataniwha haveprovidedameagrewinterdietfortheactive,
Sandstone. Dinosaurian, and other, boneshavebeen medium-sized dryosaur-like herbivorous
recovered fromsomeoftheseconcretions. dinosaur, while having the larger herbivores
(sauropods) dependent on foraging for and
Howevereighttypes ofangiosperm leaves and browsing on fallen leaf mats to sustain life over
several seed capsules have been recognised and prolonged periods ofdarkness and low tempera-
a considerable amount ofpodocarp-li—ke foliage, tureseemsan unlikelyscenario. Howmuchnutri-
similar to present-day material though ment could be derived from cold, semi-frozen,
araucarian wood, leaves and cone scales fallen leaves alone does not appearto have been
dominate the collections (Raine, 1990; calculated, but it was probably substantially
Crampton, 1990). It is hoped that ultimately the lower than in still-attached leaves, because most
study ofthis material, combined with pollen and nutrients are withdrawn from leaves before they
sporesamples,willgiveaclearerindicationofthe are dropped. The feasibility ofsauropodsofeven
botanical environment in which these dinosaurs modest proportions 'grazing' on such a leafmat
survived. is unclear, and even the question of how
sauropods supported themselves in more
POLAR DINOSAURS? temperateclimates isunresolved(Ostrom, 1985).
There is no evidence that herbivorous dinosaurs
roamed New Zealand in large herds, as occurred
WhileitisevidentthatNewZealand'sdinosaur oinfNboortthhhAemrebriviocraesatatnhdiscpaerrniiodv,oraensdwtohuelbdalhaanvcee
population was subpolarin the geographic sense
& been ultimately controlled on this island
(Fig. 6) (Molnar Wiffen 1994), it is notreadily
landmass by the quality, quantity, reproductive
apparentthattheclimateandconditions in which
they survived during the subsequent 15-20 mil- rate and availablity ofthe vegetation that formed
lion years werepolarintheclimatic sense. Water the food supply. The deciduous vegetation does
temperatures of 14.3°C are suggested from not appear to have been adequate to support the
oxygen isotope studies by Stevens & Clayton known dinosaurs through a cold polar winter.
(1971) and the marine record shows that Migration was not an option on this relatively
plesiosaurs, mosasaurs andturtles werecommon small island landmass (Molnar & Wiffen, 1994).
in offshore waters in the Late Cretaceous. On There is nothing in the dinosaur bones so far
land, there is—evidence of continuous forest and identifiedfrom the Mangahouanga Stream siteto
plant growth e.g., the Jurassic fossil forest at indicate dwarfism, as suggested for Victorian
&
Curio Bay, Southland, the plant beds at Port dinosaurs by Vickers-Rich Rich (1993): a use-
Waikato, the lignite and plant fossils in both ful strategy if food resources or climatic condi-
South and North Islands, material from Shag tions made hibernation necessary for survival.
Point and Cretaceous material from Putarau, But hibernation forthe relatively large dinosaurs
northwesternNelson, KaiparaHarbourandMan- (Allosaurus-slze theropods and medium-size
gahouanga Stream (Bose, 1975; Edwards, 1926; sauropods) found in New Zealand seems unlike-
Ettingshausen, 1891; Johnson, 1993; K—ennedy, ly. Even remaining stationary for long periods in
1993;Mildenhall, 1970;Stevens, 1985) which groups toconserve warmthwouldbeunlikelyfor
would have been essential to maintain a her- dinosaurs of this large size, while laying down
728 MEMOIRS OFTHEQUEENSLAND MUSEUM
DINOSAURIAN PALAEOBIOLOGY: ANEWZEALANDPERSPECTIVE 729
FIG.4.Pterosaurdistalulna(CD467)fromtheMaun-
gatanwha Sandstone, Mangahouanga Stream. Scale
= 1cm.
and curling up to keep the extremities warm
would be improbable and finding sufficient
handy caves to accommodate a number of
animals ofthissize unbelievable. Sothere are no
obviousbehavioral strategiesforthedinosaursto
have coped with acold polar winter, either.
The difficulty of comparing the environment
and dinosaurs from New Zealand and Australia
arises from the difference in geological ages of
rthaensgeedfirnoomsaJuurrafsasuincast.oTEhaerlAyusCtrreatlaicaenoudsi,nowshaiulres FIMGa.un5.gaFtosasniilwchoackSraonadcsht,onaeb,ouMta4ng3amhmoulaonngg,afSrtormeatmh.e
wAuhsetrreaalsiathweasonsltyillknatotwanchebdonteosGfornodmwaNneaw, Tprheesehnet.ad was not found, but the right antenna (a) is
Zealand are Late Cretaceous (Maastrichtian, 65-
70 mill—ion years) when New Zealan—d had been bered that Sphenodon punctatus was a New
adrift and an isolated island for ap- Zealandresidentpriortoand sincethe separation
proximately 15-20 million years after separation from Gondwana and that it apparently survived
from Gondwana. It would appear that dinosaurs everything, including the Pleistocene ice ages
eitheradapted to whateverclimatic changes they from around 2 million to 14,000 years ago: an
encountered over their 15-20 million years of example ofenduranceovera longperiodoffluc-
occupation or the climate on the New Zealand tuating temperature. Admittedly, the relatively
landmass remained relatively stable and smallsizeandlowermetabolicrateoftheTuatara
temperate. Doubtless even with a reasonably allowed it to hibernate using holes and tunnels
stableandtemperatemaritimeclimate,asprobab- made by birds, or tree roots, for shelter. On the
ly existed, there were times when temperatures other hand the Moas, flightless ratite birds of
droppedorroseand—conditions wereunfavorable large proportions whose ancestors are also
fordinosaurian life withsubsequentdecreases believed to have lived on New Zealand since it
in population size and reproduction at that time, separated from Gondwana, would have had dif-
such as occurs in the wild (and also with domes- ficulty in hibernating during the Ice Age, b—ut
ticated) animals today, but so far as is known of survived until shortly afterthe arrival ofman
insufficient magnitude to wipe out any species around 1,000 years ago. This in spite of their
before the end ofthe Cretaceous. higher metabolic rates and hence increased sus-
Aliving example ofthe resiliency that favours ceptibility to low temperatures and winter food
long-term survival is the Tuatara (Sphenodon shortages.
punctatus): toquoteVickers-Rich&Rich(1993), These are just two of a number of the forms
'this reptile can live in conditions down to 5°C which are known to have survived, regardless of
r
as long as it can sun itself. It must be remem- climaticchangesand turbulentgeologicalevents,
FIG,3.A,PlesiosaurianvertebraeexposedinaconcretionattheMangahouangaStreamlocality.B,Pedalphalanx
ofalargetheropodexposedinaconcretionatthislocality. Bothspecimensshow thecharacteristicstructureof
fossilbone as itis seen inthe fieldand show how thebonecanbe easilyrecognised in situ.
730 MEMOIRS OFTHEQUEENSLANDMUSEUM
dominated the forests in this region. The
recovered dinosaur material shows no special
adaptations to cold climates. However, the sur-
vival ofTuataras and Moas through the climatic
variations that occurred in New Zealandsinceits
separation from Gondwana shows that both en-
dothermicandectothermicformswerecapableof
surviving here for long periods. There is no
reasonto thinkthat dinosaurs werenotabletodo
so, too.
It is hoped that other New Zealand sites yield-
ingMesozoicterrestrialfossilswillbefound,and
that more material will add to what we already
know and expand our understanding of
dinosaurian life and survival here on New
Zealand and our place in the evolution of
Gondwanan dinosaurs.
ACKNOWLEDGEMENTS
FIG. 6. MapofLateCretaceousSouthernHemisphere IwouldliketothankMikePole,I.L.Danieland
insouthpolarprojectionshowingthepositionofNew J.P. Lovis for information regarding Cretaceous
Zealand(NZ). SP=South Pole. plant life in New Zealand, J.I. Raine forhis con-
tinuing study of the Mangahouanga Stream site
since New—Zealand's isolation 80-85 million plant fossils, and R.E. Molnar for his editorial
years ago though, as yet, there is little fossil assistance.
evidence oftheir long period ofresidence. So it
is not unexpected that the—dinosaurs whetherec- LITERATURECITED
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DINOSAURIAN PALAEOBIOLOGY: ANEWZEALANDPERSPECTIVE 731
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