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The most ancient animal species on Madagascar ascertained

The Russian researchers in collaboration with the foreign colleagues have ascertained the most ancient animal species on the island Madagascar. This is a representative of the family of carnivorous water whirligig beetles.
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On the Madagascar located near the East coast of Africa, there live hundreds of endemic (unique for this particular place) species of flora and fauna. The most well-known among Madagascar endemic species are lemurs and tenrecs which are supposed by scientists to come to the island in the last 60 million of years. The biologists have decided to study more ancient species which had inhabited Madagascar even before the island had split from the supercontinent Gondwana and afterward from the future Indian subcontinent.

A research assistant from the I.D. Papanin Institute of Biology of Inland Waters RAS Alexander Prokhin and his colleagues from the Universities in Sweden and USA have become interested in water whirligig beetles (family Gyrinidae). These beetles can run along the water surface and known as model organisms for study such habit of life.

In the south-west part of Madagascar, the species Heterogyrus milloti inhabiting mountain watercourses is preserved. To clarify its origin and the spot in the genealogic table of the family, the authors of the study have analyzed the morphology of living and extinct representatives of Gyrinidae.

They have detected 121 morphological characters of imago of 127 species including 20 fossil ones from all subfamilies of world fauna, and also 11 species from an external group (the species which resemble the studied object by external features) including six fossil ones. By comparing the species and placing them based on the comparison on the phylogenetic tree, the researchers have composed a consistent scenario of family evolution.

As a result, it has been cleared up that Heterogyrus milloti is a unique descendant of insects from Mesozoic epoch which survived up to present days. This group formed in the late Triassic/ early Jurassic periods (226 — 187 million of years ago). By comparing the data with the known genealogic trees of other species of the island, the researches have concluded that the water beetles are the most ancient species on Madagascar. The most ancient vertebrate are turtles from genus Podocnemis, blind snakes from genus Xenotyphlops and some species of frogs and fishes cichlids. However, all these species had appeared on the island in the late Jurassic / early Cretaceous periods.

«The mountains and islands hide many endemics, the very narrow-spread and victimizable local species. They could become a safe harbor for very ancient groups in the course of global cataclysms. A remote island is very similar to the „Jurassic Park.“ Otherwise, one could not explain the presence of the unique species survived from the large subfamily on Madagascar,» - a coauthor of the study Alexander Prokin commented.

Previously, all fossil species of water whirligig beetles have been described by Russian paleoentomologist Alexander Ponomarenko from the Paleontological Institute RAS. The discovery shows the importance of protection of ecosystem of Madagascar: the isolated water ponds and other biotopes of the island can hide unique relict species and communities.

The results of the study have been published in the journal Nature Scientific Reports.

Before, a new species of geckos shedding scale has been discovered on Madagascar.

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