Monday, October 29, 2012

[PaleoIchthyology • 2007] เฟอร์กาโนเซอราโตดัส มาร์ตินี | Ferganoceratodus martini • A new Thai Mesozoic lungfish (Sarcopterygii, Dipnoi) with an insight into post-Palaeozoic dipnoan evolution

We describe a new species of lungfish, Ferganoceratodus martini sp. nov., based on a single specimen discovered in the Late Jurassic – Early Cretaceous of the Phu Nam Jun locality, north-eastern Thailand. The material comprises an almost complete skull roof with associated upper and lower jaws, as well as some postcranial remains. F. martini shows characters unexpected and/or unknown in other Mesozoic lungfishes, such as pieces of a ‘hard snout’. The microstructure of the ‘hard snout’ provides support to the Bemis and Northcutt interpretation of the cosmine tissue of Palaeozoic lungfishes as homologous to the complex cutaneous vasculature of the living Neoceratodus. Because the homologies of the ossifications of the skull roof among lungfishes and among piscian sarcopterygians are unsatisfactorily understood, we use a topological nomenclature in the description of the specimen and in the discussion of post-Devonian dipnoan skull roof characters. We define a few characters for the cladistic analysis only, but these are regarded as less theory-laden. We propose a hypothesis of phylogenetic relationships for most of the post-Devonian forms known by skull remains. The main feature is the ancient dichotomy between the Neoceratodus lineage and most of the other Mesozoic forms, including the Lepidosirenids. The palaeobiogeographical pattern shows a series of vicariant events between Laurasia and Gondwana in the Late Triassic – Early Jurassic, followed by a vicariant event between Africa and South America.  

 Keywords: histology – new taxon – palaeoecology – palaeogeography – phylogeny – tooth plate.

Reconstitution of fossil lungfish Ferganoceratodus martini discovered in the Early Cretaceous (140 million years) in Thailand. © Lionel Cavin MHN / MHS

A, B: fossil lungfish Ferganoceratodus martini discovered in the Early Cretaceous (140 million years) in Thailand. C, D: Position of fossil inside the head of the animal. This fish has large enameled plates instead of teeth (visible between the eyes) he used to grind their food. E: reconstitution of lungfish. © Lionel Cavin MHN / MHS

Lionel Cavin, a paleontologist at the Natural History Museum of the City of Geneva (Switzerland) and Anne Kemp, a biologist at the Australian Rivers Institute, Brisbane (Australia), have recently shown that the lungfish, these curious primitive fish that have the both lungs and gills are much older and valuable than was previously thought.

Thailand discovering a fossil from the Lower Cretaceous (140 million years) belonging to this lineage of fish fossils and reviewing the Triassic (250 million years) from museum collections, the two researchers have shown that some lungfish belong to a branch very old, very special and long tree of evolution, as well as the famous coelacanth fish considered true living fossils.

Lungfish were widespread in the freshwaters of the world at the beginning of secondary. Helvetic-Australian study shows that it is in these times that distant line of lungfish is individualized and managed to survive until today in the form of a single species living in Australia.

This discovery provides novel arguments in favor of the protection of lungfish. According to Lionel Cavin and Anne Kemp, "we must now consider the fish as a living fossil part of our global heritage of biodiversity." It now appears particularly urgent to protect Neoceratodus forsteri, the endemic Australian species of about 120 cm long is weakened because it does (on) lives only in four small watersheds in the region of Brisbane (Queensland ). To preserve the unique Australian lungfish, it is essential to better manage the development and operation of waterways around Brisbane, a high growth area and among the most densely populated areas of Australia.

This study shows that paleontology, science based on the study of extinct for millions of years, can lead to very current issues related to the future of biodiversity.

The Australian lungfish Neoceratodus forsteri in the process of breathing air. Lungfish have both gills and lungs, which allows them to breathe in water as in the air. © Anne Kemp

2007. A new Thai Mesozoic lungfish (Sarcopterygii, Dipnoi) with an insight into post-Palaeozoic dipnoan evolution. Zoological Journal of the Linnean Society. 149: 141–177. [[Fulltext]]

Progress in Jurassic studies in Thailand in 2006 and early 2007