The Ypresian Cambay Formation at Vastan and Mangrol mines in Gujarat, western India, has yielded a rich vertebrate fauna with a large proportion of small to middle-sized mammal taxa of European affinities. Here we report a new, approximately contemporary mammal assemblage from the nearby mine of Tadkeshwar. Two fossil layers have been discovered. The older one is a grey clayey sand situated a few meters above the lower major lignite seam and represents a fluvial deposit. The younger layer is a lenticular dark clayey silt, lignitic and rich in organic remains situated just below the upper major lignite seam. This younger layer is sedimentologically similar to the famous fossiliferous lenses known from Vastan. These two fossil layers have yielded a mammal fauna similar to that of Vastan with the co-occurrence of the perissodactyl-like cambaytheriid Cambaytherium thewissi, the adapoid primates Marcgodinotius indicus and Asiadapis cambayensis, and the hyaenodontid Indohyaenodon raoi. The presence of these species in both mines and at different levels suggests that the deposits between the two major lignite seams represent a single mammal age. Apart from the aforementioned classic species there are at least two new species. A new smaller but abundant cambaytheriid is represented by upper and lower jaws, many isolated teeth and postcranial bones. A new esthonychid tillodont is described based on a dentary with m3, an isolated m2, two upper molars and two lower incisors. This new fauna from Tadkeshwar also contains the first large early Eocene vertebrates from India including an unidentified perissodactyl-like ungulate, a mesosuchian dyrosaurid-like crocodiliform and a giant madtsoiid snake. This latter group is particularly diversified in Tadkeshwar. Among the Tadkeshwar vertebrates, several taxa are of Gondwanan affinities attesting that the early Eocene was a crucial period in India during which Laurasian taxa of European affinities coexisted with relict taxa from Gondwana before the India-Asia collision. Grant Information Fieldwork and research supported by National Geographic Society, Leakey Foundation, Wadia Institute of Himalayan Geology, Belgian Science Policy Office.
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European mesonychids are represented by few specimens found only in late Paleocene and early Eocene localities. Recent field works in Palette and La Borie (Ypresian of France) resulted in the discovery of new mesonychid specimens. Additionally, our review of the mesonychids housed by European scientific institutions allowed establishing the occurrence of Dissacus in Berru (Thanetian) and Sézanne-Broyes (Ypresian). Only the genera Pachyaena and Dissacus are recognized in Europe. Furthermore, two new Dissacus species can be defined from the Ypresian localities of Palette, Sézanne-Broyes and La Borie. We also identified from three localities several postcranial elements that could be referred to Dissacus. The preliminary study of this postcranial material suggests a cursorial locomotion. As a result of our study, we propose a scheme of evolution comprising three phases for these particular mammals in Europe. (1) The mesonychid Dissacus dispersed into Europe during Thanetian, probably from North America; it survived the PETM event and even possibly experienced a dwarfism during this global warming. (2) The very large mesonychid Pachyaena migrated into Europe shortly after the Paleocene–Eocene boundary, but it seems that it did not coexist with Dissacus: it was restricted to Northern Europe, while Dissacus was possibly present at that time only in southern areas. (3) However, Pachyaena rapidly disappeared from the European environments, while Dissacus dispersed subsequently into Northern Europe. These data support the existence of a faunal turnover in Northern Europe shortly after the PETM event: it has been notably proposed for explaining the disappearance from Europe of the carnivorous oxyaenids and hyaenodont sinopines, and their subsequent replacement by taxa from the southern areas. The persistence of Dissacus in Europe shows that size was not the main selective factor during this dramatic period. Dissacus has evolved endemically during Thanetian and Ypresian in Europe where it reached a very large size, especially in southern France and Spain. Due to its size, dental, and locomotor adaptations, Dissacus was probably the top mammal predator in Europe. It survived in Europe after its disappearance from North America, possibly due to its ecologic position and the lack of competitors. Grant Information This abstract is a contribution to the project BR/121/A3/PALEURAFRICA funded by the Belgian Science Policy Office.
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