4. Recovery dynamics – fast or
slow?
1) Stepwise recovery of life – slow and gradual
- delayed by biotic drivers
- physical perturbations (high temps/CO2/acid rain) during Induan
to Anisian (first 6MY)
- the addition of progressively higher trophic levels
- spanning some 8-9 Myr well into Middle Triassic
2) Rapid recovery
- environmental inhibition not so significant
- suggested burst of diversification in Anisian (Mid Triassic)
6. 1. Counts of major clades
Chinese marine reptile Lagerstatten
richest fauna
most continuous over long span of time
Key vertebrate biotas occur in 3
formations
7. International Union of Geological Sciences, 2009
Guanling formation (Luoping and Panxian biota)
Zhuganpo formation (Xingyi biota)
Xiowa formation (Guanling biota)
8. Early Triassic (fossiliferous)
Chaohu area, famous reptile fossil assemblage
Late Spathian
Basal ichthyopterygian present
Chaohusarus geishanensis, <1 or 2m length
Sauropterygians
Hupehsuchia
9 valid taxa reported
Source: Wikipedia
9. Clades in Triassic
CLADE: Sauropterygians Ichthyopterygians Thalattosaurs Hupehsuchians
EARLY
TRIASSIC
(Chaohu)
NO YES NO YES
EARLY MID
TRIASSIC
(Guanling)
YES YES YES NO
LATE MID
TRIASSIC
(Zhuganpo)
YES NO YES NO
LATE TRIASSIC
(Xiowa)
NO YES YES
(dominant)
NO
10. A recent summary of Chinese Triassic marine reptiles implies early
diversification throughout much of the early Triassic and even close to
the PT boundary
11. However…
Sampling bias possible
Artificial diversity boosts
Low taxon numbers – truly represent success?
NO fossil Lagerstatten from Early Triassic
12. 2. Feeding guilds
Unique feeding adaptations - Early Triassic
1) Feeding habitat – pelagic or demersal
2) Prey capture – ram with biting, lunge, suction
3) Tooth shape – pointed, rounded, filter, edentulous
Use these 3 basic features to capture any large scale
patterns in the evolution of feeding guilds
13. Feeding guilds
Examples: looking at variation in feeding styles of -
Hupesuchians - Palate and mandible suggest – rare
lunge feeder - first in history of life
Spathian (Early Triassic)
Ichthyosauria (Omphalosaurus)
Rounded teeth, rostral jaw, edentulous
Spathian (Olenekian, Early Triassic)
Sauropterygian (Atopodentatus)
Filter feeder
Anisian (early middle Triassic)
Source: http://alphynix.tumblr.com/image/120459753490
14. Feeding guilds
Highest variation in marine reptile feeding
strategy reached in Spathian (Early
Triassic), indicates a rapid diversification
of prey preference in less than 1 MY
Burst in early Triassic
15. However….
Minor lineages of marine reptile - poorly understood –
conceal true diversity of feeding styles
Incompleteness of fossil record – inherently biased
16. 3. Morphology
Unusually large ichthyosaur humerus about 28cm length recovered
from Spathian (Early Triassic) –humerus length correlated to overall
body length
C. geishanensis of Chaohu was max 2m length
Humerus – shows that Early Triassic ichthyosaur record ALREADY quite
diverse and large ichthyosaurs were already widespread during the
Spathian
NO significant size increase of predators observable from Early Triassic
to the Anisian
17. But…
Accurate age dating of these Early Triassic fossils
remains difficult – depending on the definition of the
Olenekian-Anisian boundary (Late Early to Early Mid
Triassic)
18. Further evidence –
Thalattoarchon saurophagis
Ichthyosaur – large - 8.6m or over
12 cm tooth, large bicatinate cutting,
macropredatory
Discovered Nevada - indicates early and
middle-Triassic ichthyosaur radiation
this large macrophagous apex predator
as early as Anisian (mid Triassic)
Modern level complexity reached within
8 MY after PTME and within 4 MY of
when reptiles first invaded the sea
Top tier – indicates rest of ecosystem
had recovered by its appearance, no
gradual build up of forms to get to it Source: National Geographic
19. But…
Analyses of rich fossil Lagerstatten in S. China ALSO
show evolution of diverse marine reptile faunas by
ANISIAN (early middle Triassic) - BUT large and
macrophagous apex predator is unknown there
Could be peculiarity of record in China
20. Why not slow?
Pattern - feeding guilds - does not support slow stepwise
Delayed recovery could reflect poor sampling in the Early
Triassic – not true absence
Already by the Induan had several trophic levels for global
marine ecosystem present - Marine trophic pyramid was
NOT truncated in early Triassic
Prolonged stepwise recovery pattern of marine ecosystems
after PTME needs reconsideration
21. Summary – how rapid was marine
reptile diversification?
Clade diversity –peak already reached in Anisian (Early Mid Triassic)
Feeding guild diversification – RAPID – highest variation- Spathian –
EARLY TRIASSIC
morphological disparity - suggests this 1st radiation already diversified
broadly to a variety of trophic guilds (like feeding guilds)
Discovery of Thalattoarchon shows full ecosystem recovery early on in
Triassic
High degree of adaptation to aquatic environment of marine reptiles,
infer that they evolved during EARLIER stages of Early Triassic e.g.
Induan
Likely follows rapid recovery model for diversification
22. References
Benton MJ, Zhang Q, Hu S, Chen Z-Q, Wen W, et al. (2013) Exceptional
vertebrate biotas from the Triassic of China, and the expansion of marine
ecosystems after the Permo-Triassic mass extinction. Earth Sci Rev 125: 199–
243
Chen, Z-Q and Benton, M.J. (2012) The timing and pattern of biotic recovery
folllowing the end-Permian mass extinction. Nature Geoscience. 5:375-383
Fröbisch, N. B., Fröbisch, J., Sander, P. M., Schmitz, L., & Rieppel, O. 2013.
Macropredatory ichthyosaur from the Middle Triassic and the origin of
modern trophic networks. Proceedings of the National Academy of
Sciences, 110: 1393-1397
Motani, R., Chen, X. H., Jiang, D. Y., Cheng, L., Tintori, A., & Rieppel, O.
(2015). Lunge feeding in early marine reptiles and fast evolution of marine
tetrapod feeding guilds. Scientific reports, 5.
Scheyer, T. M., Romano, C., Jenks, J., & Bucher, H. 2014. Early Triassic Marine
Biotic Recovery: The Predators' Perspective. PloS one. 9: 3.
