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[dinosaur] Late Cretaceous faunal similarity of Madgascar and South India + Triassic bonebed in Poland




Ben Creisler
bcreisler@gmail.com

A new paper:


Thomas John Dixon Halliday, Guntupalli Veera Raghavendra Prasad & Anjali Goswami (2016)
Faunal similarity in Madagascan and South Indian Late Cretaceous vertebrate faunas.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
doi: http://dx.doi.org/10.1016/j.palaeo.2016.11.046
http://www.sciencedirect.com/science/article/pii/S0031018216307970

Highlights

The Cretaceous vertebrate fauna of the Cauvery Basin is strongly similar to that of Madagascar.
The Cauvery Basin and Madagascar cluster to the exclusion of the Deccan Volcanic Province.
Faunas imply long-maintained vicariance or dispersal despite several million years separation.

Abstract

The modern-day fauna of the Indian subcontinent is a mixture of ancestral Gondwanan clades, Laurasian immigrants, and endemic radiations as a result of its complex geological history. During the latest Cretaceous, the Indian subcontinent has been reconstructed at peak isolation from other continents, having separated last from Madagascar approximately 85 million years ago. The majority of vertebrate fossils known from the Late Cretaceous of India are from the Deccan Volcanic Province, but fossil material from the Cauvery Basin in South India has provided a second diverse vertebrate fauna from this time period. Here, we use the modified Forbes and Raup-Crick faunal dissimilarity indices to demonstrate that the faunal composition of the Cauvery Basin is distinct from that of the Deccan intertrappean and infratrappean beds, and shows greater faunal similarity with the Maevarano Basin of Madagascar than other Indian localities, despite several million years having elapsed since the geological separation of the two island continents.

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Also, another paper not yet mentioned:

Monika Kowal-Linka & Adam Bodzioch (2017)

Genesis of the Lower Triassic bonebeds from Gogolin (S Poland): The impact of microbial mats on trapping of vertebrate remains.

Palaeogeography, Palaeoclimatology, Palaeoecology 466, 15 January 2017: 38–58

doi: http://dx.doi.org/10.1016/j.palaeo.2016.11.010

http://www.sciencedirect.com/science/article/pii/S0031018216306988


 

Highlights


Three Lower Triassic bone-bearing horizons were recently discovered (S Poland).

The vertebrate remains accumulated in a transitional zone between a sabkha and a sea.

The presence of microbial mats was the crucial factor controlling these accumulations.

The microbial mats trapped reptile and fish remains transported across them.

The reptile remains represent at least Dactylosaurus and Nothosaurus (Sauropterygia).


Abstract


Three bone-bearing horizons, consisting of seven bone-bearing beds with fish and reptile remains, were recently discovered in the Uppermost Röt (Buntsandstein, Lower Triassic) peritidal and shallow marine carbonates in the vicinity of Gogolin (S Poland). The aim of this study is to recognize the genesis and depositional environments of the bonebeds. Detailed fieldwork, microfacies analysis, and SEM-EDS analysis reveal that the vertebrate remains occur to a great extent alongside evidence for former microbial activity. The reptile remains represent at least Dactylosaurus and Nothosaurus (Sauropterygia) genera, while the fish remains belong to the Chondrichthyes and Actinopterygii. The vertebrate remains were deposited in a transitional zone between the costal sabkha and the epicontinental sea. The first bone-bearing horizon originated in the most landward setting, in the uppermost intertidal zone, likely at the margins of a pond or coastal lagoon. The second bone-bearing horizon was formed in the upper intertidal zone. The vertebrate remains of the third bone-bearing horizon were accumulated in two different settings: in the lower intertidal zone (in a small palaeopond) and in the subtidal zone (in a protected back-shoal lagoon). Three bone accumulations occur within planar stromatolites, while the other bone-bearing beds reveal more indirect evidence for former microbial activity. In our opinion, the presence of the sticky microbial mats in the intertidal settings was the crucial factor that allowed the establishment of and controlled these accumulations of vertebrate remains. The soft gluey substrates trapped vertebrate remains that were transported across them. Once trapped, the vertebrate bioclasts were efficiently immobilized and thus protected against damage due to sedimentological agents. The lack of any orderly arrangement of the vertebrate bioclasts suggests that they may have been delivered to the individual mat surfaces by diverse media, from various directions, and also at different times.