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We describe a partial dyrosaurid skeleton recently prepared out of a limestone block discovered in the 1930s from Danian strata along the Atlantic coast of Senegal. The specimen, from a single individual, comprises nicely preserved elements of the appendicular and axial skeleton from the abdominal and sacral region, which enables us to refine our knowledge on some postcranial characteristics of the Dyrosauridae. Although Dyrosauridae are abundant in early Eocene deposits of North Africa, the present discovery in the Danian of Senegal fills a patchier record early after the K/Pg boundary and provides an important comparative data point with the few other Danian dyrosaurid records such as Atlantosuchus from nearby Morocco or Guarinisuchus and Hyposaurus from Brazil and the USA, respectively.

The phosphate series of Matam (located at the NorthEast of Senegal) consists of a 10 meters alternation of soft phosphate levels, sand horizons and phosphatic limestones. While they were only mentioned in some preliminary geological works, isolated teeth of selachians are nevertheless common in these phosphate deposits. Detailed fieldwork of 9 new well-drillings allowed us to establish the first exhaustive list of the Matam selachian fauna with their biostratigraphical distribution through five main fossiliferous levels spanning the Thanetian-Early Lutetian period. Their importance for biochronological, paleoenvironmental purposes and correlations with the other Eocene phosphate deposits worldwide is noteworthy. The Matam selachian is represented by 38 species belonging to 34 genera, 16 families and 6 orders, which allow us to define different biochronological associations. The first association (e.g. characterized by Eotorpedo hilgendorfi and E. jaekeli) is associated with the sands of the top of Gorgol Fm. that constitute the ground level of exploited phosphate deposits and testify of a clear marine influence during the Late Thanetian. The three following associations were recovered in the main levels of exploited phosphate of the Matam Fm. They contain a richer and more diversified fauna dated to ?Lower Ypresian and are characteristic of neritic environments too. The last association (top of the Matam Fm.) overlies the phosphate layers and is characterized by a drastic decrease in selachian richness and diversity. Dated to the Lower Lutetian, this last faunal association may be indicative of a marine embayment in Matam area and contrary to western Senegal where phosphate deposits begin. If all these associations appear typical of the eastern margins of central Atlantic, the light observed faunal turnover across the ten-meter sequence suggests productivity changes in phosphate depositions during the Late Thanetian-Early Lutetian period.

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