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Pakasuchus: The "crocodile cat"

Dopo due anni di studi ricercatori dell’Università dell’Ohio hanno pubblicato la descrizione di una nuova specie di coccodrillo che mostra una peculiarità molto "mammaliana".
Le somiglianze ritrovate hanno perfino indotto i paleontologi a designare la specie con il termine swahili per "gatto” (Paka): Pakasuchus kapilimai (anche se le due specie sistematicamente non centrano nulla – restiamo a osservare se i media generali capiranno il concetto).

Fig.1. Ricostruzione di Pakasuchus kapilimai (National Science Foundation / Zina Deretsky).

The nearly complete fossil (especially the skull) of the animal was discovered in 2008 on the banks of a river in a secondary basin of the Rift Valley of Africa, Rukwa Rift Basin near Lake Tanganyika in the state of Tanzania . The river sediments from which the findings are dated at 105 million years, have also returned a variety of other species of reptiles, dinosaurs and fish (we hope that in future s entiremo other novelty of this field).

Large modern crocodiles with their conical teeth are perfectly adapted to capture, hold and drag their prey, but not to chew and process the food already in the oral cavity. Unlike them , the new species shows many features that recall the case of mammals, one animal was small and frail, the bony plates of the typical crocodile show a reduction to minimize the mass of the body and increase its mobility and arts are very slow lto in relation to lean body, but the biggest surprise is the paleontological complex dentition that this species had developed. The total number of teeth is very small when compared to modern crocodiles, but highly specialized with a pronounced eterodonte shape - reminiscent of the back teeth of molars, are large and fit on their crowns, as in mammals, forming plaques capable of chopping food.

Fig.2. Skull Pakasuchus kapilimai , that in a 'really remember the first time the skull of a synapsids, except that the openings of the skull do not match (AFP / National Science Foundation / John Sattle).

These and other characters the new species arise from or relating to the sottoordine Notosuchia, a group of "coccodrilliformi" spread between 110 and 80 million years ago on the southern continent of Gondawana and related sub-continents from the Cretaceous onwards.

A stunning example of convergent evolution - according to the preliminary hypothesis formulated on the basis of recent findings, these reptiles have adapted to the southern hemisphere in the northern hemisphere niches that were occupied by mammals: small, agile predators to pursue specialized processing and small prey such as insects and vertebrates less tonnage.

Bibliography:

CONNOR et al. (2010): The evolution of mammal-like crocodyliforms in the Cretaceous Period of Gondwana. Nature 466: 748-751