TERRESTRIALIZATION AND THE ORIGIN OF LAND VERTEBRATES – EVIDENCE FROM THE EDEN PROJECT (SE AUSTRALIA)

1. Terrestrialization and the Origin of Land
Vertebrates
Evidence from the Eden Project [SE Australia]
G.C.Young1, Jing Lu2, R.L.Dunstone1, B.Young1, Yuzhi Hu1,
You-An Zhu2
1 Research School of Physics, ANU, Canberra, Australia
2 IVPP Chinese Academy of Sciences, Beijing, China

2. Presentation Summary
A. Terrestrialization of the biota during the Devonian Period
B. Origin of Land Vertebrates
C. Tristichopterids and elpistostegids – closest fish relatives to
tetrapods?
D. Tetrapods of Gondwana, the largest Devonian Landmass
E. Tetrapodomorph fishes from the Devonian of Gondwana
F. Tetrapod origins – trackways, phylogenetic and
biogeographic evidence
G. Edenopteron and the Eden Project [SE Australia]
H. Acknowledgments

3. A. Terrestrialization of the biota during the
Devonian Period
• Increasing complexity of land vegetation by the Early Devonian led to
changes in geological processes [e.g. braided to meandering streams;
Davies & Gibling 2010, Geology 38: 51-54]
• Evolution of trees and first forests during the Middle-Late Devonian,
for the first time gave the landscape some resemblance to that of today
• First forest soils evolved [e.g. Retallack 1997, Science 276: 583-585]
• Atmospheric modelling indicated significant decreases in carbon
dioxide and increased oxygen across the Devonian Period [e.g. Berner
et al. 2007, Science 316: 557-558; Berner 2009, Am. J. Science 309:
603-606]
• ‘Old Red Sandstone’ facies red sediments characterize Devonian non-
marine sequences in many regions

4. Early Devonian landscapes
From Hao Shougang & Xue Jinzhuang [2013] The Early Devonian
Posongchong Flora of Yunnan. Science Press, Beijing

5. DEVONIAN ~420-360 Ma
Bergman et al. (2004): COPSE model [Amer. J. Science 304: 397-437]
Modelling of atmospheric O2 – COPSE model

6. DEVONIAN ~420-360 Ma
Modelling of atmospheric O2 – GEOCARBSULF model
Berner (2009): GEOCARBSULF [Amer. J. Science 309: 603-606]

7. B. Origin of Land Vertebrates
• Diverse terrestrial invertebrates [e.g. arthropods] were already
exploiting the Early Devonian land vegetation [e.g. Edgecombe 1998,
Nature 394: 172-174]
• Evolution of limbed vertebrates from fishes – the ‘Fish-Tetrapod
[F/T] Transition’ – was assumed to have occurred somewhat later
[~372-382 Ma], during the Frasnian of the Late Devonian [e.g.
Ahlberg & Clack 2006, Nature 440: 747-749]
• The discovery in 1932 of the first Devonian tetrapods [Ichthyostega,
Acanthostega] was in Upper Devonian [Famennian] red-beds of East
Greenland
• Morphological evidence indicated that the closest finned relatives to
the tetrapods were within Devonian sarcopterygians (lobe-finned
fishes), specifically tristichopterids and elpistostegids

8. CARBONIFEROUS
Famennian
Frasnian
Givetian
Eifelian
Emsian
Pragian
Lochkovian
SILURIAN
LATE
MIDDLE
EARLY
DEVONIAN
Land plants, terrestrial arthropods
[myriapods, arachnids]
Increasing complexity of land
vegetation; first trees and forests
360
420
?First terrestrial vertebrates [Tetrapod Origins]
Fish-Tetrapod [F/T] Transition

9. Ichthyostega, first discovered Devonian land animal (1932)
Upper Devonian (Famennian), East Greenland
Skull specimen Limb bones

10. Ichthyostega, Upper Devonian (Famennian), East Greenland
Restoration by Jarvik (1996)
Alternative restoration by Clack (2002)

11. LOBE-FINNED FISHES -- MODERN
Coelacanth [Latimeria] – Mozambique Channel
Queensland lungfish [Neoceratodus]
Canberra Zoo & Aquarium

12. LOBE-FINNED FISHES -- DEVONIAN
Fish impression 80 cm long
[Hegartys Bay, S. of Eden]
Cast of impression,
showing pectoral fins
Fleshy lobes

13. C. Tristichopterids and elpistostegids – closest
fish relatives to tetrapods?
• The well-studied tristichopterid Eusthenopteron [Frasnian, Canada]
demonstrated close similarity to the tetrapod limb in the internal
skeleton of its lobed fins
• The elpistostegids, of similar age, are more tetrapod-like, with
flattened crocodile-like skulls with dorsally situated orbits, compared
to the widely separated lateral orbits of fishes like Eusthenopteron
• The best-known elpistostegids are Tiktaalik [e.g. Daeschler et al. 2006
Nature 440: 757-763; Shubin et al. 2006 Nature 440: 764-771] and
Elpistostege [e.g. Cloutier et al. 2020 Nature 579: 549-554]
• These demonstrate numerous tetrapod similarities, but also that
elpistostegids are still fishes, with fins rather than limbs

14. Devonian tristichopterid [lobed-finned fish] Eusthenopteron
Internal skeleton of lobed fins

15. Nature 440 (2006)
Tiktaalik
Upper Devonian,
Ellesmere Is., Arctic Canada
Devonian elpistostegid [lobed-finned fish] Tiktaalik

16. D. Tetrapods of Gondwana, the largest Devonian
Landmass
• Tristichopterids [e.g. Eusthenopteron], elpistostegids [Elpistostege,
Panderichthys, Tiktaalik] and the first Devonian tetrapods [Ichthyostega,
Acanthostega] all come from Upper Devonian strata belonging to the
northern paleocontinent of Laurussia.
• This strongly indicated that the first tetrapods evolved in the Northern
Hemisphere
• Before 1972 it was widely assumed that tetrapods did not reach the
Southern Hemisphere until after the Permian glaciation
• Then Devonian trackways were discovered in Victoria, Australia [Warren
& Wakefield 1972, Nature 228: 469-470]
• The Victorian trackways demonstrate that while elpistostegids were still
swimming around in the Northern Hemisphere, two unknown land animals
were already walking in Gondwana
• Only one tetrapod body fossil is known from the Devonian of Gondwana:
Metaxygnathus, an isolated lower jaw [Campbell & Bell 1977, Alcheringa
1: 369-381; Ahlberg & Clack 1998, Trans. R. Soc. Edinb Earth Sci. 89:11-
46]

17. Genoa River trackway discovery, Victoria [1971]
Warren & Wakefield (1972), cover of Nature on
‘Earliest Tetrapod Trackways’
Tetrapod origins?? – Northern [Laurussia] or Southern Hemisphere [Gondwana]

18. Metaxygnathus denticulus Campbell & Bell, 1977
[from Jemalong Quarry near Forbes NSW]
Metaxygnathus
[Australia]
Ichthyostega
[E. Greenland]
The only tetrapod body fossil known so far from the Devonian of Gondwana
RIGHT LOWER JAWS

19. Prof. Chang Mee-mann
[IVPP, Beijing]
Vertebrates in basal unit [Cloghnan Shale], overlain
by 600+ m sandstone forming the Jemalong Range
Jemalong Quarry [near Forbes, NSW] 1983
Type Locality for Metaxygnathus denticulus Campbell & Bell 1977
[the only Devonian tetrapod body fossil known from the entire
Gondwana supercontinent]
AGE: ~ 370 million years (Frasnian, Late Devonian) [Young, 1999]
Dr Wang Nianzhong [IVPP, Beijing]

20. E. Tetrapodomorph fishes from the Devonian
of Gondwana
• Tristichopterids were later discovered in the Middle-Upper Devonian of the
Southern Hemisphere:
– Notorhizodon [Givetian, Antarctica; Young et al. 1992]
– Mandageria [Frasnian, Canowindra NSW; Johanson & Ahlberg 1997]
– Cabonnichthys [Frasnian, Canowindra NSW; Ahlberg & Johanson 1997]
– Eusthenodon [Famennian, Grenfell NSW; Johanson & Ritchie 2000]
– Edenopteron [Famennian, Eden NSW; Young et al. 2013, 2019]
• Marsdenichthys, from Victoria, Australia, shared characters with both
tristichopterids and Middle Devonian ‘osteolepids’; it was proposed by Long (1985)
as the sister-group to all tristichopterids
• Chang & Yu (1997) noted similarities between even older osteolepid remains from
SE Australia, and Kenichthys Chang & Yu 1993 from the Emsian of Yunnan, China
• Kenichthys, and Tungsenia [Pragian, Yunnan] are now recognized as the oldest
known stem-tetrapodomorphs [Zhu & Ahlberg 2004, Nature 432: 94-97; Lu et al.
2012, Nature Comm. 3: 1160]
• These stem-tetrapods are so far recorded only from China and Australia, suggesting
faunal exchange in the Early Devonian [Young & Lu 2020, J. Palaeogeography]

21. Tristichopterid Mandageria fairfaxi - largest fish
[1.2+ m long] in Canowindra fossil fish assemblage
Dr Alex Ritchie
[Aust. Museum, Sydney]
Mandageria fairfaxi
[latex cast of holotype]
Tristichopterid Cabonnichthys burnsi
Canowindra, NSW
Canowindra tristichopterids [first described 1997]

22. LIFE SIZE MODEL OF Edenopteron
ON DISPLAY @ CT LAB, A.N.U., CANBERRA
Prof. Jing Lu
[IVPP, Beijing]
Dr Yuzhi Hu
[ANU]
Tristichopterid Edenopteron keithcrooki Young et al. 2013
Eden, NSW

23. Dr Jing Lu
[RSPE postdoc] Yuzhi Hu
[PhD, RSES]
Edenopteron keithcrooki Young et al. 2013
World’s largest articulated Devonian lobe-fin [jaws ~50 cm long]
LIFE SIZE MODEL [by Baz Crook] ON DISPLAY
CT LAB, A.N.U., CANBERRA

24. F. Tetrapod origins - trackways, phylogenetic and
biogeographic evidence
• Mandageria and Cabonnichthys from Canowindra NSW were interpreted as derived
tristichopterids, and not immediately related in the phylogeny of Ahlberg & Johanson [1998,
Nature 395: 792-794]
• Mandageria was shown closest to Eusthenodon [Upper Devonian, East Greenland]; the
oldest, more basal tristichopterids were all from the Northern Hemisphere [Laurussian
paleocontinent]
• This indicated tristichopterids were of northern origin, with Australian and Antarctic
representatives dispersing later into East Gondwana [Ahlberg & Johanson 1997; Johanson &
Ahlberg 2001]
• The underlying assumption is that basal and/or stratigraphically older taxa indicate the centre
of origin for a group, but the Gondwanan Marsdenichthys and Notorhizodon were excluded
from the phylogeny
• Inclusion of Notorhizodon, Marsdenichthys, and older stem-tetrapods from China-Australia
mentioned above, would implicate these areas as the centre of origin for tetrapods
• In addition, Cabonnichthys, Mandageria and Edenopteron share significant characters, e.g.
accessory vomers [unknown in any other sarcopterygian], suggesting they form an endemic
tristichopterid subgroup
• Tetrapod trackways from Australia (Warren et al. 1986) and Poland (Niedzweidski et al.
2010) demonstrate a much older tetrapod origin than the ‘F/T Transition’ previously argued
from the known body fossil record.

25. Cladogram from Ahlberg & Johanson (Nature, 1998)
TETRAPODA
PAUP analysis of 99 char./29 taxa
Consensus of nine trees
TRISTICHOPTERIDAE

26. Cladogram from Ahlberg & Johanson (Nature, 1998)
TETRAPODA
PAUP analysis of 99 char./29 taxa
Consensus of nine trees
E. Greenland
E. Gondwana [EG]
Notorhizodon [EG]
Canowindridae [EG]
TRISTICHOPTERIDAE
Marsdenichthys [EG]
cf. Kenichthys [EG]
Evidence from East Gondwana [EG] added

27. Johanson & Ahlberg (1997, p. 51) on Mandageria:
• “we assign the name ‘accessory vomers’ in accordance
with Gardiner’s (1984) terminology for actinopterygians.”
• “They are not known in any other sarcopterygian … are
presumably homoplastic with the accessory vomers of
actinopterygians.”
ACCESSORY VOMERS IN SARCOPTERYGIANS:
• Only three occurrences known, all from the Devonian of SE
Australia
• 3 genera and 2 localities, with ~10 m.yr. age difference

28. Vomer
CANOWINDRA, NSW
Cabonnichthys Mandageria
acVo
Palate of two Canowindra tristichopterids described
in 1997 by Per Ahlberg & Zerina Johanson
Parasphenoid
acVo = accessory vomer
Psp = parasphenoid
Psp

29. Psp
Cleithrum
Detail of ‘accessory vomers’
Palate of tristichopterid Edenopteron [Hegartys Bay specimen] described Young et al. [2019]
acVo
acVo = accessory vomer
Psp = parasphenoid

30. 37 generalised Australian Devonian vertebrate localities
[Documented Australian Devonian fish fauna: ~248 genera; ~327 species]
Jemalong
Metaxygnathus
Only known tetrapod bone from Gondwana
Southern Hemisphere Devonian tetrapod evidence [all Australian]
Genoa River
Trackways
[Frasnian]
Campbell & Bell [1977]
Warren & Wakefield [1972]
Warren et al. [1986]
Glen Isla
Trackways
[Sil.-Dev.]

31. Global Summary -- biostratigraphic and biogeographic evidence
Fig. 8 from Young & Lu [2020]
Jour. Palaeogeography

32. G. Edenopteron and the Eden Project
[SE Australia: Boyds Tower]
• Devonian rocks are exposed along the coastal cliffs on the far south coast of NSW.
North of this the coastal rocks are mainly Ordovician, overlain by Permo-Triassic of
the Sydney Basin from just north of Batemans Bay
• Devonian outcrops extend south across the state border into Victoria, and inland as
far as the upper Genoa River. This includes the tetrapod trackway site reported in
Nature by Warren & Wakefield [1972]
• A possible Devonian fish bone was recorded in 1860 from near Eden, on the
southern side of Twofold Bay [Boyds Tower]
• An extensive collection from Boyds Tower in 1979 was mainly disarticulated bones
of Remigolepis, a placoderm fish first described in 1931 from the East Greenland
[Famennian] tetrapod locality
• A single articulated Remigolepis specimen from 1979 was relocated at Boyds Tower
in 2006, leading to the discovery of numerous articulated specimens including the
holotype of Edenopteron keithcrooki Young et al.[ 2013]
• A second site [Hegartys Bay] to the south represents the same fish assemblage, with
placoderms Remigolepis and Groenlandaspis, Edenopteron, and other
sarcopterygians [see below]. The age is late Famennian.

33. ~250 million yrs
[or younger]
~450+ million yrs
~360+ million yrs
EDEN, NSW

34. Devonian vertebrate fossil sites
Boyds Tower
Genoa R. Trackways
Hegartys Bay

35. Boyds Tower site – bone beds [mainly the placoderm Remigolepis]
Chinese colleagues visit Boyds Tower site [1989]
Dr Wang Shitao [Inst. Geol. Sci., Beijing]
Dr Zhang Guorui [IVPP, Beijing]

36. Rubber cast of 1979 Eden
specimen
Prof. Keith Crook
GC Young
Reconstruction
[based on Canowindra]
Placoderm [armoured] fish Remigolepis
[First described from E. Greenland 1931]
‘Armoured Fish’,
and ‘Fish with Arms’
‘Remigo’ [Latin] = Rower/Oarsman
Edenopteron Discovery [Boyds Tower, August 2006]
Articulated Remigolepis Specimen [part
collected 1979] rediscovered 2006

37. FANGS ON VOMERS
40+ mm long tooth
August 2006: 40 mm long fang attached to collected Remigolepis specimen
[found to belong to Edenopteron Holotype ]

38. ‘vomer’ [Latin] = ploughshare
Vomer
Vomer [unpaired] in the human skull

39. Paired vomers with fangs
Life size model of Edenopteron keithcrooki
[built by Prof. Crook’s son Baz Crook]

40. Edenopteron keithcrooki new genus; new species
Collected and prepared in lab [2006-2012]; published 2013

41. Edenopteron Type Specimen: 85 pieces stored in 16 drawers
Research School of Physics, ANU Canberra

42. G. Edenopteron and the Eden Project
[SE Australia: Hegartys Bay]
• The Hegartys Bay site was discovered by Dr Anne Warren in 1986, and
excavated in 1996 by Dr Alex Ritchie [Australian Museum], with helicopter
support from NSW National Parks to lift the fossils up the cliff face
• Collected specimens included an excellent Edenopteron skull and palate,
the latter demonstrating clearly the presence of accessory vomers as in the
Canowindra tristichopterids [Young et al. 2019]
• The excavation was never completed, and an extreme weather event [June
2016] re-exposed numerous fossil fish specimens to weathering and
disintegration
• To rescue this fossil material a new excavation was initiated in November
2019 [with funding support from the Chinese Academy of Sciences]
• Devastating bushfires [early 2020] followed by Covid lockdowns prevented
further field excavation until June 2021
• Continuing excavations at Hegartys Bay 2019-2021 have so far revealed at
least 17 complete specimens of large Gondwanan sarcopterygians unknown
to science, some showing resemblance to cosmoid sarcopts from Antarctica.
This work is ongoing.

43. Young et al. (2019). Aust. J. of Earth Sciences
First description -- Hegartys Bay fossil fish collected 1996

44. Hegartys Bay – Australian Museum excavation 1996
Documentary of 1996 excavation

45. Hegartys Bay – Australian Museum excavation 1996
[Scenes from Documentary]

46. Hegartys Bay Excavation site [uncollected fossil fish, 2008]

47. Hegartys Bay – 2017 [fossil bed exposed after storm event of June 2016]
Peter Ollerenshaw
At least 12 complete lobe-finned fish bodies new to science

48. Hegartys Bay – November 2019 [funded by Chinese Acad. Sciences]
Plaster jackets
Fossil stockpile

49. Hegartys Bay – June 2020 [after Jan-Feb 2020 bushfires]
Fossil stockpile
Bushfire devastation

50. Hegartys Bay – October 2020 [sedimentology field excursion]
Prof. R.V. Burne [ANU]
demonstrates laminar interbeds
Fossil stockpile

51. Hegartys Bay – June 2021 [funded by Chinese Acad. Science]
Fossil stockpile
Further excavation: now at least 17
complete lobe-finned fish discovered

52. • Sarah Ferguson [& others] from NSW National Parks provided
access to the national park, and help with fieldwork
• P. Ollerenshaw, L. Charlton, M. McCurry, C. O’Donnell, A. Watt,
M. & H. Pytela provided assistance with field excavations at the
Hegartys Bay fossil site
• The Strategic Priority Research Program [Chinese Academy of
Sciences], National Natural Science Foundation of China, and the
Chinese National Science Fund for Excellent Young Scholars, all
contributed funding support for the Eden Project
• ARC Discovery Grants gave funding for the original Edenopteron
description
• Numerous other colleagues have assisted in discussing scientific
aspects of this research
H. Acknowledgments